diff --git a/BUGS-TO-REPORT.md b/BUGS-TO-REPORT.md
index cd0d659ed..b949bea2f 100644
--- a/BUGS-TO-REPORT.md
+++ b/BUGS-TO-REPORT.md
@@ -1150,17 +1150,17 @@ Severity: crash. The crash is in the read, so no `On Error` handler helps, and a
 ## File statements and functions raise *Unspecified error* (-2147467259) in place of VB6's error numbers
 
 **Describe the bug**
-When a file statement or function fails, twinBASIC raises run-time error -2147467259 (`&H80004005`, *Unspecified error*) where VB6 raises a numbered error: 52 *Bad file name or number*, 53 *File not found*, 55 *File already open*, 58 *File already exists*, 59 *Bad record length*, 63 *Bad record number*, 75 *Path/File access error* or 76 *Path not found*. Of 42 failing file operations, 37 raise -2147467259, and the other 5 match VB6. An `On Error` handler written for VB6, which tests `Err.Number` for one of those numbers, does not recognise the error. Observed in a run of the reproducer project, in the IDE and in a built exe alike.
+When a file statement or function fails, twinBASIC raises run-time error -2147467259 (`&H80004005`, *Unspecified error*) where VB6 and 64-bit VBA raise a numbered error: 5 *Invalid procedure call or argument*, 52 *Bad file name or number*, 53 *File not found*, 54 *Bad file mode*, 55 *File already open*, 58 *File already exists*, 59 *Bad record length*, 62 *Input past end of file*, 63 *Bad record number*, 67 *Too many files*, 68 *Device unavailable*, 75 *Path/File access error* or 76 *Path not found*. Of 72 failing file operations, 67 raise -2147467259, and the other 5 match VB6. An `On Error` handler written for VB6, which tests `Err.Number` for one of those numbers, does not recognise the error. Observed in a run of the reproducer project, in the IDE and in a built exe alike.
 
 **To Reproduce**
 Steps to reproduce the behavior:
-1. Open `file-errors-unspecified.twinproj` (attached as `file-errors-unspecified.zip`) and run it (F5). Its `Sub Main` makes a folder in `%TEMP%`, makes 42 file operations fail one at a time under `On Error Resume Next`, and prints `<case>: <Err.Number> <Err.Description>` after each. The smallest of them:
+1. Open `file-errors-unspecified.twinproj` (attached as `file-errors-unspecified.zip`) and run it (F5). Its `Sub Main` makes a folder in `%TEMP%`, makes 72 file operations fail one at a time under `On Error Resume Next`, and prints `<case>: <Err.Number> <Err.Description>` after each. The smallest of them:
    ```
    On Error Resume Next
    Kill Environ$("TEMP") & "\no-such-file.txt"
    Debug.Print Err.Number, Err.Description
    ```
-2. See `-2147467259 Unspecified error` in each of these 37 cases, where the same program built in VB6 (attached as `file-errors-unspecified-vb6.zip`) prints the number shown:
+2. See `-2147467259 Unspecified error` in each of these 67 cases, where the same program built in VB6 (attached as `file-errors-unspecified-vb6.zip`) prints the number shown:
 
    | operation that fails | VB6 |
    |---|---|
@@ -1186,26 +1186,51 @@ Steps to reproduce the behavior:
    | `EOF`, `LOF`, `Loc`, `Seek`, `FileAttr`, `Get #`, `Put #`, `Print #` and `Line Input #` with file number 99, which is not open (9 cases) | 52 |
    | `Seek #f, 0` | 63 |
    | `Put` of a 22-character string to a `Random` file opened with `Len = 4` | 59 |
+   | `ChDir` to a file, to `""` and to a wildcard (3 cases) | 76 |
+   | `ChDrive` and `CurDir` of a drive letter no drive has (2 cases) | 68 |
+   | `ChDrive` and `CurDir` of `"1"`, which is not a letter (2 cases) | 5 |
+   | `Dir()` after `Dir` has returned `""` | 5 |
+   | `Dir` of a file name with a backslash at its end | 52 |
+   | `Dir` of a name of 256 characters | 53 |
+   | `FileAttr` with a *returntype* of 2 | 5 |
+   | `FileCopy` from `""` | 75 |
+   | `FileCopy` from a wildcard | 52 |
+   | `FileLen` of a file in a folder that does not exist | 76 |
+   | `FileLen` of a wildcard that matches nothing | 52 |
+   | `FreeFile` with every file number from 1 to 255 in use | 67 |
+   | `GetAttr` of a wildcard | 52 |
+   | `GetAttr` of a name with `<` in it | 5 |
+   | `Input` and `InputB` of more characters than are left in a file open `For Input` (2 cases) | 62 |
+   | `Input` from a file open `For Output` | 54 |
+   | `Input` of -1 characters | 5 |
+   | `Input` from file number 99, which is not open | 52 |
+   | `Kill` of a folder | 53 |
+   | `Kill` of a wildcard that matches a read-only file | 75 |
+   | `MkDir ""` | 76 |
+   | `RmDir` of a file | 76 |
+   | `RmDir` of the current directory | 75 |
+   | `SetAttr` of a wildcard | 52 |
+   | `Width #99`, which is not open | 52 |
 
 3. See the 5 cases that match VB6: `FileCopy` of a file that does not exist (53) and into a folder that does not exist (76), `Line Input #` past the end of the file (62), and `Close` of a file number that is not open and `SetAttr` of a file open `For Input`, which raise no error in either.
 
 **Expected behavior**
-The numbers in the table, with VB6's descriptions, as for the 5 cases that already match. A VB6 program that handles a missing file by testing `Err.Number = 53` takes its other branch in twinBASIC.
+The numbers in the table, with VB6's descriptions, as for the 5 cases that already match; 64-bit VBA raises the same numbers. A VB6 program that handles a missing file by testing `Err.Number = 53` takes its other branch in twinBASIC.
 
 **Desktop:**
  - OS: Windows 10 Pro 22H2 (build 19045)
  - twinBASIC compiler version: BETA 1010
 
 **Additional context**
-This extends #2345, which reports the first row of the table, and is part of #56. `FileCopy` raises VB6's numbers, since #2451 fixed it.
+This extends #2345, which reports the first row of the table, and is part of #56. `FileCopy` raises VB6's numbers for a source or a folder that does not exist, since #2451 fixed it; the numbers it raises for the other failures are a separate report.
 
-The same in a built exe as in the IDE, and the same with the project setting *Use Unicode Standard Library* set to No. In code compiled with LLVM the number is the same, and the description is *Application-defined or object-defined error*.
+The same in a built exe as in the IDE, and the same with the project setting *Use Unicode Standard Library* set to No. In code compiled with LLVM the number is the same, and the description is *Application-defined or object-defined error*. A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
 
 What does not reproduce it: the `DirListBox` and `FileListBox` controls trap the error themselves, and raise 76 for a `Path` that does not exist, as VB6 does.
 
 Severity: moderate. An error is raised wherever VB6 raises one, so no failure goes unreported. But a handler that tests for the number does not recognise the error, a handler that shows `Err.Description` shows *Unspecified error*, and code that decides a file exists from `Err.Number <> 53` decides wrongly.
 
-<!-- Reproducer: bugs/file-errors-unspecified/ (mode run; expect lists the 37 lines that print -2147467259, so a fix of some statements and not others shows as NO LONGER REPRODUCES). verify reproduces on BETA 1005; VB6 side in vb6/, built and run by bug_repro.mjs vb6; the built-exe and LLVM results and the Use Unicode Standard Library check are from probes in a local scratch folder, not in the repository. Found while testing scripts/imagestrip/, a twinBASIC console program that strips the metadata from the images in the IDE's CSS files. Stated in a NOTE naming BETA 1005 on each of these pages: docs/Reference/Core/Open.md, Name.md, Get.md, Put.md, Print.md (under "Writing to a file") and Line-Input.md; docs/Reference/Default/VBA/FileSystem/Kill.md, GetAttr.md, SetAttr.md (the NOTE, not the WARNING, which belongs to the SetAttr entry), FileLen.md, FileDateTime.md, MkDir.md, RmDir.md, ChDir.md, EOF.md, LOF.md, Loc.md, Seek.md and FileAttr.md. When a statement is fixed, its NOTE goes, and its page states the error number it raises with no mention of the defect. -->
+<!-- Reproducer: bugs/file-errors-unspecified/ (mode run; expect lists the 67 lines that print -2147467259, so a fix of some statements and not others shows as NO LONGER REPRODUCES). verify reproduces on BETA 1010; VB6 side in vb6/, built and run by bug_repro.mjs vb6; the built-exe and LLVM results and the Use Unicode Standard Library check are from probes in a local scratch folder, not in the repository; 64-bit and 64-bit VBA from the run-time errors data (errors/VBA.FileSystem.yml, `errors.mjs run`, all four runtimes). Found while testing scripts/imagestrip/, a twinBASIC console program that strips the metadata from the images in the IDE's CSS files; the 30 cases from ChDir to a file on were added 2026-10-27 by batch 7 of WIP.Errors.md. Stated in a NOTE on each of these pages: docs/Reference/Core/Open.md, Name.md, Get.md, Put.md, Print.md (under "Writing to a file") and Line-Input.md (hand NOTEs, until batch 11); and in the Common Errors sections (rows `bug: file-errors-unspecified`) of docs/Reference/Default/VBA/FileSystem/ChDir, ChDrive, CurDir, Dir, EOF, FileAttr, FileCopy, FileDateTime, FileLen, FreeFile, GetAttr, Input, InputB, Kill, LOF, Loc, MkDir, RmDir, Seek, SetAttr and Width, from errors/VBA.FileSystem.yml. When a statement is fixed, its row's cases move to a row of VB's number and the NOTE goes (a hand NOTE goes, and its page states the error number it raises with no mention of the defect). -->
 
 ---
 
@@ -1237,7 +1262,7 @@ Error 55 for a file open `For Output`, `Append`, `Binary` or `Random`, with its
 **Additional context**
 Severity: low, but silent. No error is raised, and the file's attributes change where VB6 leaves them alone: the file stays read-only until its attributes are set back.
 
-<!-- Reproducer: bugs/setattr-open-file-no-error/ (mode run; expect lists the four lines for the write modes). verify reproduces on BETA 1005; VB6 side in vb6/. Found while checking the error numbers of the file statements (the entry above). Stated in docs/Reference/Default/VBA/FileSystem/SetAttr.md: the sentence that SetAttr sets the attributes of an open file without an error, and the WARNING after it, naming BETA 1005. The VBA-Docs sentence it replaced ("A run-time error occurs when setting the attributes of an open file") was true of neither product as written. When fixed, the WARNING goes and the sentence says that SetAttr raises error 55 for a file open for Output, Append, Binary or Random, and sets the attributes of a file open for Input. -->
+<!-- Reproducer: bugs/setattr-open-file-no-error/ (mode run; expect lists the four lines for the write modes). verify reproduces on BETA 1005; VB6 side in vb6/. Found while checking the error numbers of the file statements (the entry above). Stated in docs/Reference/Default/VBA/FileSystem/SetAttr.md: the sentence that SetAttr sets the attributes of an open file without an error, the WARNING after it, and the Common Errors section's NOTE (the row `bug: setattr-open-file-no-error` in errors/VBA.FileSystem.yml, whose cases 64-bit twinBASIC and 64-bit VBA agree with, batch 7 of WIP.Errors.md, 2026-10-27). VB6 and 64-bit VBA also raise 55 for a file open For Binary Access Read, which the row leaves out. The VBA-Docs sentence it replaced ("A run-time error occurs when setting the attributes of an open file") was true of neither product as written. When fixed, the WARNING goes and the sentence says that SetAttr raises error 55 for a file open for Output, Append, Binary or Random, and sets the attributes of a file open for Input. -->
 
 ---
 
@@ -7259,13 +7284,14 @@ Given an argument they refuse, several runtime procedures raise -2147467259 (`&H
 - `Shell` with a zero-length path, spaces, a folder, a file that is not a program, or a path longer than 32,767 characters: 5; with a program or folder that does not exist, or an unclosed quotation mark: 53, *File not found*; with a *windowstyle* less than 0 or greater than 10: 5.
 - `MsgBox` and `InputBox` with a *helpfile* and no *context*: 5.
 - `SendKeys` raises -2147352567 (`&H80020009`), *Exception occurred.*, instead: for an unknown key code (`{INS}` and `{F17}` included), an unclosed brace, a count in braces that is not a whole number from 0 to 8,175, unbalanced parentheses or `++`, VB raises 5; for a *wait* of `Null`, 94; for a *wait* string that is not a `Boolean`, 13.
+- The Financial functions, where VB raises 5: `DDB`, `SLN` and `SYD` with a *life* of 0 or less (`SLN`: of 0), `DDB` and `SYD` with a *period* of 0 or less or greater than *life*, or a *salvage* less than 0, and `DDB` with a *factor* of 0 or less; `IPmt` with an *nper* of 0 or less and `PPmt` with an *nper* less than 0; `Pmt` with a *rate* and an *nper* of 0, and `NPer` with a *rate* and a *pmt* of 0; `Rate` with an *nper* of 0 or less, or no result in 20 tries from *guess*; `IRR` with no payment or no receipt in *values*, or no result in 20 tries. `Rate` with an *nper* below 1 whose result is beyond the range of a `Double`: VB raises 6.
 
 It is the pattern of #2544 (`ReDim` with inverted bounds raises -2147467259 where VB6 raises 9). Observed in the compiler's test mode and in built exes, 32-bit and 64-bit.
 
 **To Reproduce**
 Steps to reproduce the behavior:
 1. Open `argument-errors-unspecified-error.twinproj` (attached as `argument-errors-unspecified-error.zip`).
-2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other twenty-five fail, each with `Err.Number` -2147467259, or -2147352567 for the two `SendKeys` cases.
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other thirty-five fail, each with `Err.Number` -2147467259, or -2147352567 for the two `SendKeys` cases.
 
 The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`argument-errors-unspecified-error-vb6.zip`) prints; 64-bit VBA raises the same numbers. No case writes to the registry: the registry procedures are given names that do not exist.
 ```vb
@@ -7507,6 +7533,88 @@ Module RegressionTests
         Assert.Strict.AreEqual 94&, Err.Number
     End Sub
 
+    ' The Financial functions (batch 9).
+    [TestCase]
+    Public Sub DDB_LifeZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = DDB(1000, 100, 0, 1)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub SLN_LifeZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = SLN(1000, 100, 0)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub SYD_PeriodAboveLife_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = SYD(1000, 100, 5, 6)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_NperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = IPmt(0.01, 1, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_NperNegative_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = PPmt(0.01, 1, -10, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_RateAndNperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = Pmt(0, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub NPer_RateAndPmtZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = NPer(0, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_NperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = Rate(0, -100, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_NperBelowOneOverflow_Raises6()
+        Dim R As Double
+        On Error Resume Next
+        R = Rate(0.5, -100, 1000)
+        Assert.Strict.AreEqual 6&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_NoReceipt_Raises5()
+        Dim R As Double, F(1) As Double
+        F(0) = -100: F(1) = -110
+        On Error Resume Next
+        R = IRR(F)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
 End Module
 ```
 
@@ -7524,7 +7632,7 @@ A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01
 
 What does not reproduce it: the errors these procedures already raise with VB's numbers, such as `LBound` of an array not yet sized (9), `QBColor` outside 0 to 15 (5), `RGB` with a negative component (5), and `Null` for any of the arguments above (94).
 
-<!-- Reproducer: bugs/argument-errors-unspecified-error/ (mode test: `tbrun --tests`; expect lists the three PASS and twenty-five FAIL lines); run on BETA 1010 with `bug_repro.mjs run`; 64-bit from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case. Stated in the Common Errors sections (rows `bug: argument-errors-unspecified-error`) of LBound, UBound, Switch, Partition, Environ, GetObject, CallByName, SaveSetting, GetSetting, GetAllSettings, DeleteSetting, AppActivate, Shell, MsgBox, InputBox and SendKeys, from errors/VBA.Information.yml and errors/VBA.Interaction.yml; when fixed, each row's `error` becomes VB's number and its `vb6` and `bug` go, and the NOTEs with them. Found 2026-10-22 by batch 6a of WIP.Errors.md; grouped as one entry by the owner. The interactive procedures added 2026-10-27 by batch 6b (owner: SendKeys' -2147352567 joins it); the VB6 side carries a copy of errors/harnesses/dialog.bas for its MsgBox and InputBox cases. -->
+<!-- Reproducer: bugs/argument-errors-unspecified-error/ (mode test: `tbrun --tests`; expect lists the three PASS and thirty-five FAIL lines); run on BETA 1010 with `bug_repro.mjs run`; 64-bit from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case. Stated in the Common Errors sections (rows `bug: argument-errors-unspecified-error`) of LBound, UBound, Switch, Partition, Environ, GetObject, CallByName, SaveSetting, GetSetting, GetAllSettings, DeleteSetting, AppActivate, Shell, MsgBox, InputBox and SendKeys, from errors/VBA.Information.yml and errors/VBA.Interaction.yml, and of DDB, SLN, SYD, IPmt, PPmt, Pmt, NPer, Rate and IRR, from errors/VBA.Financial.yml (the Financial functions added 2026-10-28 by batch 9); when fixed, each row's `error` becomes VB's number and its `vb6` and `bug` go, and the NOTEs with them. Found 2026-10-22 by batch 6a of WIP.Errors.md; grouped as one entry by the owner. The interactive procedures added 2026-10-27 by batch 6b (owner: SendKeys' -2147352567 joins it); the VB6 side carries a copy of errors/harnesses/dialog.bas for its MsgBox and InputBox cases. -->
 
 ---
 
@@ -8493,3 +8601,2534 @@ Severity: low. Programs on the user's own desktop are not affected.
 When the window is created hidden and shown with `SW_SHOWNA`, the 2 s moves from `CreateWindowEx` into `AppActivate`; so the wait belongs to the activation of a new window, whichever call makes it. The program never calls `GetForegroundWindow` during it. On a private desktop no window becomes the foreground window; something in the twinBASIC runtime apparently waits for that, with a 2 s limit.
 
 <!-- Reproducer: bugs/private-desktop-window-activation-delay/ (mode run with exe: `tbrun --exe`, which starts the exe on a private desktop; expect lists windows 2 to 4 at 2 s); verified on BETA 1010 by `bug_repro.mjs verify`. VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints 0.00 for every step on a private desktop. On the user's desktop (owner, 2026-10-27, a run of the same program from the session's scratchpad) twinBASIC took 0.02 s a window. Not stated on any page: the documentation does not run on a private desktop; scripts/errors.mjs gives a twinBASIC probe 120 s because of it (WIP.Errors.md, the window harness). Found 2026-10-22 by batch 6b of WIP.Errors.md; owner: a bug, surprising for anyone who tests on a private desktop. -->
+
+---
+
+## `Kill` deletes hidden and system files, where VB6 and VBA raise error 53 and leave them
+
+**Describe the bug**
+`Kill` deletes a file that has the hidden or the system attribute, and raises no error. VB6 and 64-bit VBA never delete such a file: `Kill` of a hidden or system file raises 53, *File not found*, and leaves it, and a wildcard skips such files, deleting the others it matches (and raising 53 when it matches nothing else). So `Kill "*.*"` in twinBASIC also deletes the hidden and system files of the folder, which a VB6 program relies on it to keep. Observed by running the reproducer's test cases.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `kill-hidden-system-files.twinproj` (attached as `kill-hidden-system-files.zip`).
+2. Run its test cases, the module below. On BETA 1010 the two controls pass and the other five fail.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`kill-hidden-system-files-vb6.zip`) prints; 64-bit VBA raises the same numbers. Every case runs under a copy of a files harness, which makes a folder of the case's own under `%TEMP%` the current directory, fills it with the files the case names, and deletes it after the case, so no case touches any other file. The harness is in the attached project, left out below.
+```vb
+' Regression tests: Kill refuses a hidden or a system file with error 53, as VB6 and 64-bit VBA
+' do, and a wildcard skips such files, where twinBASIC deletes them.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ... the copy of the files harness: in the attached project. files_Begin makes a folder of
+    ' the case's own the current directory, with a.txt (10 bytes), empty.txt, ro.txt (read-only),
+    ' hid.txt (hidden), the empty folder sub and the folder full holding f.txt; files_End closes
+    ' every file, deletes the folder and keeps the case's error; files_Attr is GetFileAttributesW ...
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Kill_NormalFile_Deletes()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") = -1
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Kill_ReadOnlyFile_RaisesAndKeepsIt()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "ro.txt"
+        Holds = files_Attr("ro.txt") <> -1
+        files_End
+        Assert.Strict.AreNotEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_HiddenFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "hid.txt"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_SystemFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "a.txt", vbSystem
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_HiddenSystemFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "a.txt", vbHidden + vbSystem
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_WildcardMatchingOnlyAHiddenFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "h*"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_Wildcard_LeavesHiddenFile()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "ro.txt", vbNormal
+        Kill "*.txt"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+Error 53 for `Kill` of a hidden or a system file, the file left in place, and a wildcard that skips hidden and system files, as VB6 and 64-bit VBA do.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045), system locale 1033
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: high. Files are deleted that a VB6 or VBA program would keep, with no error: `desktop.ini`, `Thumbs.db` and other hidden or system files in a folder a program empties with `Kill "*.*"`.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: a file with the read-only attribute (75 in VB, -2147467259 in twinBASIC, the entry on *Unspecified error*, and the file kept in all three); a file with only the archive attribute, which all of them delete.
+
+<!-- Reproducer: bugs/kill-hidden-system-files/ (mode test: `tbrun --tests`; expect lists the two PASS and five FAIL lines); verified on BETA 1010 by `bug_repro.mjs verify`, and in a 64-bit run (`run --arch win64`); 64-bit VBA from the run-time errors data (`errors.mjs run`, all four runtimes). Both sides carry a copy of errors/harnesses/files.bas. VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case and whether the file is as the case expects. Stated in the WARNING on docs/Reference/Default/VBA/FileSystem/Kill.md and in its Common Errors section (row `bug: kill-hidden-system-files` in errors/VBA.FileSystem.yml); when fixed, the row's cases move to a row of 53, and the NOTE and the WARNING go. Found 2026-10-27 by batch 7 of WIP.Errors.md. -->
+
+---
+
+## `FileCopy` raises 70 where VB6 and VBA raise 75, and 55 where they raise 70
+
+**Describe the bug**
+When `FileCopy` fails for one of these reasons, it raises another number than VB6 and 64-bit VBA:
+- *source* is a folder, or *destination* is a folder, a read-only file or a hidden file: twinBASIC raises 70, *Permission denied*; VB raises 75, *Path/File access error*.
+- *destination* is *source* itself, by any spelling (`"a.txt"`, `"A.TXT"`, `".\a.txt"`), or *source* is open `For Input Lock Read`: twinBASIC raises 55, *File already open*; VB raises 70.
+
+An error is raised in each case, and nothing is copied, but a handler written for VB6 or VBA does not recognise it.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `filecopy-error-numbers.twinproj` (attached as `filecopy-error-numbers.zip`).
+2. Run its test cases, the module below. On BETA 1010 the two controls pass and the other seven fail.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`filecopy-error-numbers-vb6.zip`) prints; 64-bit VBA raises the same numbers. Every case runs under a copy of a files harness, which makes a folder of the case's own under `%TEMP%` the current directory, fills it with the files the case names, and deletes it after the case, so no case touches any other file. The harness is in the attached project, left out below.
+```vb
+' Regression tests: FileCopy raises VB6's numbers, 70 for a copy onto its own source or of a
+' source locked against reading, and 75 for a folder or a read-only or hidden destination.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ... the copy of the files harness: in the attached project. files_Begin makes a folder of
+    ' the case's own the current directory, with a.txt (10 bytes), empty.txt, ro.txt (read-only),
+    ' hid.txt (hidden), the empty folder sub and the folder full holding f.txt; files_End closes
+    ' every file, deletes the folder and keeps the case's error; files_Attr is GetFileAttributesW ...
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileCopy_MissingSource_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "nosuch.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileCopy_SourceOpenForAppend_Raises55()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Append As #1
+        FileCopy "a.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 55&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_OntoItself_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "a.txt"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_OntoItselfOtherCase_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "A.TXT"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_SourceOpenLockRead_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Input Lock Read As #1
+        FileCopy "a.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_SourceFolder_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "sub", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationFolder_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "sub"
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationReadOnly_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "ro.txt"
+        Holds = FileLen("ro.txt") = 1
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationHidden_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "hid.txt"
+        Holds = FileLen("hid.txt") = 1
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+75 for a folder or a read-only or hidden destination, and 70 for a copy onto the source or of a source locked against reading, as VB6 and 64-bit VBA raise.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045), system locale 1033
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low. Each failure raises an error, but not the number a VB6 or VBA handler tests for.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: a source that does not exist (53) or a folder that does not exist (76), which #2451 fixed; a source open with write access (55 in all). The other failures of `FileCopy` that raise -2147467259 (a zero-length name, a wildcard) are in the entry on *Unspecified error*. twinBASIC also copies a source open with `Access Read` in any mode, where VB raises 55; the owner takes that as an extension.
+
+<!-- Reproducer: bugs/filecopy-error-numbers/ (mode test: `tbrun --tests`; expect lists the two PASS and seven FAIL lines); verified on BETA 1010 by `bug_repro.mjs verify`, and in a 64-bit run (`run --arch win64`); 64-bit VBA from the run-time errors data (`errors.mjs run`, all four runtimes). Both sides carry a copy of errors/harnesses/files.bas. VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case. Stated in the Common Errors section of docs/Reference/Default/VBA/FileSystem/FileCopy.md (rows `bug: filecopy-error-numbers` in errors/VBA.FileSystem.yml); when fixed, each row's cases move to a row of VB's number and the NOTEs go. Found 2026-10-27 by batch 7 of WIP.Errors.md. -->
+
+---
+
+## `CurDir`, `Dir`, `FileDateTime`, `FileLen`, `Input` and `Width` check their arguments differently from VB6 and VBA
+
+**Describe the bug**
+Given these arguments, the procedures do something other than VB6 and 64-bit VBA:
+- `CurDir(Null)` and `Dir(Null)` raise 94, *Invalid use of Null*; VB raises 13, *Type mismatch*.
+- `FileLen` and `FileDateTime` of a name with a wildcard that matches something (`"*.txt"`, `"e*"`, `"a.tx?"`) return the length or the date of the first match, which may be a hidden file or a folder, and raise nothing; VB raises 52, *Bad file name or number*. (A wildcard that matches nothing raises -2147467259, the entry on *Unspecified error*; so does `"a?txt"`.)
+- `Width #f, n` with a negative *n* raises nothing, and `Print #f` then starts a new line before each item after the first; VB raises 5, *Invalid procedure call or argument*.
+- `Input(0, #f)` raises -2147467259, *Unspecified error*; VB returns a zero-length string. (`InputB(0, #f)` returns one in both.)
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `filesystem-argument-checks.twinproj` (attached as `filesystem-argument-checks.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other six fail.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`filesystem-argument-checks-vb6.zip`) prints; 64-bit VBA raises the same numbers. Every case runs under a copy of a files harness, which makes a folder of the case's own under `%TEMP%` the current directory, fills it with the files the case names, and deletes it after the case, so no case touches any other file. The harness is in the attached project, left out below.
+```vb
+' Regression tests: CurDir, Dir, FileDateTime, FileLen, Input and Width check their arguments
+' as VB6 and 64-bit VBA do: 13 for a Null drive or path, 52 for a wildcard where a file name is
+' expected, 5 for a negative width, and no error for Input of 0 characters.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ... the copy of the files harness: in the attached project. files_Begin makes a folder of
+    ' the case's own the current directory, with a.txt (10 bytes), empty.txt, ro.txt (read-only),
+    ' hid.txt (hidden), the empty folder sub and the folder full holding f.txt; files_End closes
+    ' every file, deletes the folder and keeps the case's error; files_Attr is GetFileAttributesW ...
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub CurDir_ZeroLength_ReturnsCurrent()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = CurDir("")
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileLen_File_Returns10()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileLen("a.txt")
+        Holds = V = 10
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Width_255_Accepted()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "b.txt" For Output As #1
+        Width #1, 255
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub CurDir_Null_Raises13()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = CurDir(Null)
+        files_End
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Dir_Null_Raises13()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = Dir(Null)
+        files_End
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileLen_Wildcard_Raises52()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileLen("*.txt")
+        files_End
+        Assert.Strict.AreEqual 52&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileDateTime_Wildcard_Raises52()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileDateTime("e*")
+        files_End
+        Assert.Strict.AreEqual 52&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Width_Negative_Raises5()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "b.txt" For Output As #1
+        Width #1, -1
+        files_End
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Input_ZeroCharacters_ReturnsEmpty()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Input As #1
+        V = Input(0, #1)
+        Holds = V = ""
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+13 for a `Null` drive or path, 52 for a wildcard in `FileLen` and `FileDateTime`, 5 for a negative width, and a zero-length string from `Input(0, #f)`, as VB6 and 64-bit VBA give.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045), system locale 1033
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: medium for `FileLen` and `FileDateTime`, which return a value for a file the program did not name, silently, and for a negative `Width`, which changes what `Print #` writes, silently. Low for the rest.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: a *Width* from 0 to 255, or from 256 to 32,767, which twinBASIC takes as a line width where VB raises 5 (the owner takes that as an extension); `FileLen` and `FileDateTime` of a file or a folder named without a wildcard; `Input` of 1 or more characters.
+
+<!-- Reproducer: bugs/filesystem-argument-checks/ (mode test: `tbrun --tests`; expect lists the three PASS and six FAIL lines); verified on BETA 1010 by `bug_repro.mjs verify`, and in a 64-bit run (`run --arch win64`); 64-bit VBA from the run-time errors data (`errors.mjs run`, all four runtimes). Both sides carry a copy of errors/harnesses/files.bas. VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case. Stated in the Common Errors sections (rows `bug: filesystem-argument-checks` in errors/VBA.FileSystem.yml) of CurDir, Dir, FileDateTime, FileLen, Input and Width under docs/Reference/Default/VBA/FileSystem/, and in the WARNINGs on FileDateTime.md, FileLen.md and Width.md; when fixed, each row's cases move to a row of VB's number (Input's to its quiet cases), and the NOTEs and the WARNINGs go. Found 2026-10-27 by batch 7 of WIP.Errors.md; owner: bugs, while Dir's attributes, non-String arguments of Dir and CurDir, FileCopy of a source open for reading, SetAttr's attributes and a Width above 255 are extensions. -->
+
+---
+
+## Assigning `Err.HelpFile` or `Err.HelpContext`, or `Err.ReturnHResult` in a module, compiles but fails the build with a codegen error
+
+**Describe the bug**
+A statement that assigns `Err.HelpFile` or `Err.HelpContext` compiles with no diagnostic, but the build fails with a code-generation error in the procedure that holds it:
+```
+[LINKER] compilation (codegen) error detected in 'Startup.Mainrootmain' at line #3
+[LINKER] FAILED due to compilation errors '...\ErrHelpfileHelpcontextCodegen_win32.exe'
+[BUILD] failed
+```
+The same happens through `With Err`, `VBA.Err` and a variable declared `As ErrObject`, for a constant or a variable value, and for `Err.ReturnHResult` assigned in a procedure of a module. In the compiler's test mode, which builds nothing, each such procedure ends at once as *aborted*.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Create a project whose only module is:
+   ```vb
+   Module Startup
+       Public Sub Main()
+           Err.HelpFile = "x"
+           Debug.Print Err.HelpFile
+       End Sub
+   End Module
+   ```
+2. Compile it: no diagnostic. Build it: the build fails with the error above, naming the line of the assignment.
+3. Or open `err-helpfile-helpcontext-codegen.twinproj` (attached as `err-helpfile-helpcontext-codegen.zip`) and run its test cases, the module below, with the class `Thing` it calls. On BETA 1010 the five controls pass and the other four end as *aborted*.
+
+The module is meant to be adapted as a regression test. Each case assigns a property of `Err` and reads it back; the attached VB6 project (`err-helpfile-helpcontext-codegen-vb6.zip`) makes the same assignments and prints `HelpFile: [x]`, `HelpContext: 5` and `HelpFile through ErrObject: [y]`.
+```vb
+' The issue's regression tests. Each assigns one property of Err and reads it back.
+' The controls (Description, Source, Number, HelpFile and HelpContext through an
+' Object variable, and ReturnHResult in a class method) pass; HelpFile and
+' HelpContext assigned through Err itself, or through a variable declared As
+' ErrObject, and ReturnHResult in a module procedure, do not build.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_SetDescription()
+        Err.Description = "x"
+        Assert.Strict.AreEqual "x", Err.Description
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetSource()
+        Err.Source = "x"
+        Assert.Strict.AreEqual "x", Err.Source
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetNumber()
+        Err.Number = 5
+        Assert.Strict.AreEqual 5&, Err.Number
+        Err.Clear
+    End Sub
+
+    [TestCase]
+    Public Sub Control_LateBoundHelpFileAndContext()
+        Dim o As Object
+        Set o = Err
+        o.HelpFile = "x"
+        o.HelpContext = 5
+        Assert.Strict.AreEqual "x", Err.HelpFile
+        Assert.Strict.AreEqual 5&, Err.HelpContext
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpFile()
+        Err.HelpFile = "x"
+        Assert.Strict.AreEqual "x", Err.HelpFile
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpContext()
+        Err.HelpContext = 5
+        Assert.Strict.AreEqual 5&, Err.HelpContext
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpFileThroughErrObjectVariable()
+        Dim e As ErrObject
+        Set e = Err
+        e.HelpFile = "x"
+        Assert.Strict.AreEqual "x", Err.HelpFile
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetReturnHResultInClassMethod()
+        Dim t As New Thing
+        t.Status
+        Assert.Strict.AreEqual 1&, Err.LastHresult
+    End Sub
+
+    [TestCase]
+    Public Sub SetReturnHResultInModule()
+        Err.ReturnHResult = 1
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+End Module
+```
+```vb
+' A class whose method sets the HRESULT it returns, as the ReturnHResult page shows.
+Class Thing
+
+    Public Function Status() As Long
+        Err.ReturnHResult = 1
+    End Function
+
+End Class
+```
+
+**Expected behavior**
+The assignments build and set the property, as in VB6 and 64-bit VBA, which assign `HelpFile` and `HelpContext` like any other property of `Err`. If assigning `ReturnHResult` outside a method of a class is meant to be refused, a diagnostic that says so at compile time, rather than a failed build.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low. The build fails, so nothing is lost, and there are ways round it: `Err.Raise` sets both properties through its *helpfile* and *helpcontext* arguments, and an assignment through a variable declared `As Object` that holds `Err` works.
+
+A 64-bit build fails the same way.
+
+What does not reproduce it: assigning `Err.Description`, `Err.Source` or `Err.Number`; reading `Err.HelpFile` or `Err.HelpContext`; assigning them late-bound, through an `Object` variable; assigning `Err.ReturnHResult` in a method of a class, which builds and gives the caller its value in `Err.LastHresult`.
+
+<!-- Reproducer: bugs/err-helpfile-helpcontext-codegen/ (mode test: `tbrun --tests`; expect lists the five PASS and four FAIL lines, each FAIL "aborted"); verified on BETA 1010, and in a 64-bit run (`run --arch win64`). The build failure of step 2 was checked with `tbbuild --build` on a one-line project. VB6 side in vb6/ (VB6 6.0). Stated in NOTEs on docs/Reference/Default/VBA/ErrObject/HelpFile.md, HelpContext.md and ReturnHResult.md; when fixed, the NOTEs go and errors/VBA.ErrObject.yml gets the HelpFile and HelpContext pages' cases (`Err.HelpFile = Null` and `Err.HelpContext = Null`, which raise 94 in VB6 and 64-bit VBA). Found 2026-10-27 by batch 8 of WIP.Errors.md, where the probe's build failed. -->
+
+---
+
+## `Err.Raise` and `Err.Number` keep an `HRESULT` that VB6 and VBA turn into the VB error of the same meaning
+
+**Describe the bug**
+`Err.Raise` of an `HRESULT` raises that `HRESULT`, and assigning one to `Err.Number` stores it. VB6 and 64-bit VBA raise, and store, the VB error of the same meaning for many of them: `Err.Raise &H80070057` (`E_INVALIDARG`) raises 5, *Invalid procedure call or argument*, there, and twinBASIC raises -2147024809. A handler that tests `Err.Number` for the VB number does not recognise the error.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `err-raise-hresult-mapping.twinproj` (attached as `err-raise-hresult-mapping.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other nine fail.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`err-raise-hresult-mapping-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: Err.Raise of an HRESULT that has a VB error of the same meaning raises
+' that VB error, as VB6 and 64-bit VBA do, and assigning one to Err.Number stores the VB
+' error. The controls raise a VB number and an HRESULT that VB keeps as it is.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function Raised(ByVal Number As Long) As Long
+        On Error Resume Next
+        Err.Raise Number
+        Raised = Err.Number
+    End Function
+
+    [TestCase]
+    Public Sub Control_Raise5_Raises5()
+        Assert.Strict.AreEqual 5&, Raised(5)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RaiseEFail_RaisesEFail()
+        Assert.Strict.AreEqual &H80004005, Raised(&H80004005)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RaiseDispException_RaisesDispException()
+        Assert.Strict.AreEqual &H80020009, Raised(&H80020009)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_EInvalidArg_Raises5()
+        Assert.Strict.AreEqual 5&, Raised(&H80070057)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_EOutOfMemory_Raises7()
+        Assert.Strict.AreEqual 7&, Raised(&H8007000E)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ENotImpl_Raises445()
+        Assert.Strict.AreEqual 445&, Raised(&H80004001)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ENoInterface_Raises430()
+        Assert.Strict.AreEqual 430&, Raised(&H80004002)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_DispUnknownName_Raises438()
+        Assert.Strict.AreEqual 438&, Raised(&H80020006)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_DispTypeMismatch_Raises13()
+        Assert.Strict.AreEqual 13&, Raised(&H80020005)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ClassNotRegistered_Raises429()
+        Assert.Strict.AreEqual 429&, Raised(&H80040154)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_VbErrorAsHResult_Raises53()
+        Assert.Strict.AreEqual 53&, Raised(&H800A0035)
+    End Sub
+
+    [TestCase]
+    Public Sub Number_EInvalidArg_Is5()
+        Err.Number = &H80070057
+        Dim N As Long = Err.Number
+        Err.Clear
+        Assert.Strict.AreEqual 5&, N
+    End Sub
+
+End Module
+```
+
+Every `HRESULT` tried, with what `Err.Raise` gives (twinBASIC raises each one as it is):
+
+| `HRESULT` | VB6 and 64-bit VBA |
+|---|---|
+| `&H80070057` `E_INVALIDARG` | 5 |
+| `&H8007000E` `E_OUTOFMEMORY` | 7 |
+| `&H80070005` `E_ACCESSDENIED` | 70 |
+| `&H80004001` `E_NOTIMPL` | 445 |
+| `&H80004002` `E_NOINTERFACE` | 430 |
+| `&H80004004` `E_ABORT` | 287 |
+| `&H80020003` `DISP_E_MEMBERNOTFOUND` | 438 |
+| `&H80020005` `DISP_E_TYPEMISMATCH` | 13 |
+| `&H80020006` `DISP_E_UNKNOWNNAME` | 438 |
+| `&H80020008` `DISP_E_BADVARTYPE` | 458 |
+| `&H8002000A` `DISP_E_OVERFLOW` | 6 |
+| `&H8002000B` `DISP_E_BADINDEX` | 9 |
+| `&H8002000E` `DISP_E_BADPARAMCOUNT` | 450 |
+| `&H80020011` `DISP_E_NOTACOLLECTION` | 451 |
+| `&H80030002` `STG_E_FILENOTFOUND` | 432 |
+| `&H80030003` `STG_E_PATHNOTFOUND` | 76 |
+| `&H80030005` `STG_E_ACCESSDENIED` | 70 |
+| `&H80030070` `STG_E_MEDIUMFULL` | 61 |
+| `&H80040112` `CLASS_E_NOTLICENSED` | 429 |
+| `&H80040154` `REGDB_E_CLASSNOTREG` | 429 |
+| `&H800401E3` `MK_E_UNAVAILABLE` | 429 |
+| `&H800401F3` `CO_E_CLASSSTRING` | 429 |
+| `&H800A0005`, `&H800A0035`, `&H800A01A8`, `&H800AFFFF` (a VB error as an `HRESULT`) | 5, 53, 424, 65535 (the low 16 bits) |
+| `&H80004005` `E_FAIL`, `&H80020009` `DISP_E_EXCEPTION`, `&H80070002`, `&H80070006`, `&H8007000B`, `&H80070020`, `&H80070070`, `&H8007007E`, `&H8000FFFF` `E_UNEXPECTED`, `&H80004003` `E_POINTER`, `&H80040000` (`vbObjectError`) | the same `HRESULT` |
+
+`Err.Number = &H80070057`, `&H80004001` and `&H800A0035` leave `Err.Number` 5, 445 and 53 in VB6 and 64-bit VBA, without raising an error.
+
+**Expected behavior**
+The VB number, as VB6 and 64-bit VBA give, for `Err.Raise` and for an assignment to `Err.Number`, so that a handler written for VB sees the number it tests for.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low to medium. An error is raised in every case, but code that raises an `HRESULT` it got from an API, or a class that reports `E_INVALIDARG` the way COM code does, reaches a handler that tests for 5 with a number it does not recognise.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+Related: the queued entry on late-bound calls (`latebound-hresult-mapping`) is about the `HRESULT` a late-bound call returns, which VB maps the same way; this one is about `Err.Raise` and `Err.Number` themselves.
+
+What does not reproduce it: an `HRESULT` that VB keeps as it is (the last row of the table); a VB number from 1 to 65535. twinBASIC also raises a positive number above 65535, where VB raises 5; the owner takes that as an extension.
+
+<!-- Reproducer: bugs/err-raise-hresult-mapping/ (mode test: `tbrun --tests`; expect lists the three PASS and nine FAIL lines); verified on BETA 1010. The table comes from the run-time errors data's exploration in all four runtimes (`errors.mjs run`: twinBASIC 32-bit and 64-bit, VB6 and 64-bit VBA); errors/VBA.ErrObject.yml keeps twinBASIC's side as `only: tb` quiet cases of Raise.md and Number.md. VB6 side in vb6/ (VB6 6.0). Stated in the hand NOTEs (BETA 1010) on docs/Reference/Default/VBA/ErrObject/Raise.md, which has the table, and Number.md; when fixed, the NOTEs go, the `only: tb` quiet cases become rows of their VB numbers, and the central page's note on Err.Raise of an HRESULT (docs/Reference/Run-time-Errors.md) is checked. Found 2026-10-27 by batch 8 of WIP.Errors.md. -->
+
+---
+
+## `Collection`'s `Item`, `Remove` and `Add` check an index or a position differently from VB6 and VBA
+
+**Describe the bug**
+Given these indexes and positions, a `Collection` does something other than VB6 and 64-bit VBA:
+- A `Currency`, `Decimal` or `Date` number is refused: `Item` and `Remove` raise 9, *Subscript out of range*, and `Add`'s *before* and *after* raise 13, *Type mismatch*, where VB takes the number as it takes a `Long` or a `Double` (`C.Item(CCur(2))` is the second item).
+- `Item` of a number on an empty collection raises 9; VB raises 5, *Invalid procedure call or argument*, as twinBASIC's own `Remove` does.
+- `Item` and `Remove` of `Null`, an object, `Nothing`, an array, an error value or a number outside the `Long` range raise 9; VB raises 13. So does `Add`'s *before* of a number outside the `Long` range.
+- `Add`'s *before* or *after* of -1, `True` or `Empty` raises 13; VB raises 9, as for any other position that is not an item's.
+- `Add` with a *key* of `Empty` adds the item without a key and raises nothing; VB raises 13, as for any other key that is not a `String`.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `collection-index-checks.twinproj` (attached as `collection-index-checks.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other fourteen fail.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`collection-index-checks-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: Collection's Item, Remove and Add take an index or a position as VB6 and
+' 64-bit VBA do: a Currency, Decimal or Date number like any other number; 5 for a number on
+' an empty collection (Item); 13 for Null, an object or a number outside the Long range
+' (Item, Remove); 9 for a position of -1, True or Empty, and 13 for a key of Empty (Add). The controls use a Long, a
+' Double and a Byte, and a string key. tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    ' A collection holding "a" and "b", without keys.
+    Private Function Two() As Collection
+        Set Two = New Collection
+        Two.Add "a"
+        Two.Add "b"
+    End Function
+
+    ' The error Item(Index) raises on C, or 0 and the item in Got.
+    Private Function ItemError(ByVal C As Collection, ByVal Index As Variant, Optional ByRef Got As Variant) As Long
+        On Error Resume Next
+        Got = C.Item(Index)
+        ItemError = Err.Number
+    End Function
+
+    Private Function RemoveError(ByVal C As Collection, ByVal Index As Variant) As Long
+        On Error Resume Next
+        C.Remove Index
+        RemoveError = Err.Number
+    End Function
+
+    Private Function AddBeforeError(ByVal C As Collection, ByVal Before As Variant) As Long
+        On Error Resume Next
+        C.Add "x", , Before
+        AddBeforeError = Err.Number
+    End Function
+
+    [TestCase]
+    Public Sub Control_ItemOfLongDoubleByte()
+        Dim Got As Variant
+        Assert.Strict.AreEqual 0&, ItemError(Two(), 2&, Got)
+        Assert.Strict.AreEqual "b", Got
+        Assert.Strict.AreEqual 0&, ItemError(Two(), 2#, Got)
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CByte(2), Got)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ItemOutOfRange_Raises9()
+        Assert.Strict.AreEqual 9&, ItemError(Two(), 3)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ItemOfMissingKey_Raises5()
+        Assert.Strict.AreEqual 5&, ItemError(Two(), "z")
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Currency_ReturnsItem()
+        Dim Got As Variant
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CCur(2), Got)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Decimal_ReturnsItem()
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CDec(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Date_ReturnsItem()
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CDate(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Remove_Currency_Removes()
+        Assert.Strict.AreEqual 0&, RemoveError(Two(), CCur(2))
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_Currency_Adds()
+        Assert.Strict.AreEqual 0&, AddBeforeError(Two(), CCur(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Item_EmptyCollection_Raises5()
+        Assert.Strict.AreEqual 5&, ItemError(New Collection, 1)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Null_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), Null)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Object_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), New Collection)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_BeyondLong_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), 2147483648#)
+    End Sub
+
+    [TestCase]
+    Public Sub Remove_Null_Raises13()
+        Assert.Strict.AreEqual 13&, RemoveError(Two(), Null)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_MinusOne_Raises9()
+        Assert.Strict.AreEqual 9&, AddBeforeError(Two(), -1)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_Empty_Raises9()
+        Assert.Strict.AreEqual 9&, AddBeforeError(Two(), Empty)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_BeyondLong_Raises13()
+        Assert.Strict.AreEqual 13&, AddBeforeError(Two(), 2147483648#)
+    End Sub
+
+    [TestCase]
+    Public Sub Add_EmptyKey_Raises13()
+        Dim C As New Collection
+        On Error Resume Next
+        C.Add "x", Empty
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+The numbers VB6 and 64-bit VBA give: a `Currency`, `Decimal` or `Date` index or position taken as a number; 5 for `Item` of a number on an empty collection; 13 for `Null`, an object, an array or a number outside the `Long` range; 9 for a position of -1, `True` or `Empty`; 13 for a key of `Empty`.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: medium for the `Currency`, `Decimal` and `Date` indexes, which VB code passes without thinking (a `Currency` loop counter, a value read from a database field), and which twinBASIC refuses. Low for the key of `Empty`, whose item can then be reached only by its position. Low for the rest: an error is raised where VB raises one, with another number.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: an index or a position of `Byte`, `Integer`, `Long`, `LongLong`, `Single` or `Double`, rounded as VB rounds it; a string key; a number out of range on a collection that has items (9 in all); `Remove` on an empty collection (5 in all); `Add`'s *before* or *after* given on an empty collection (5 in all). twinBASIC also takes a *before* of one more than `Count` as the end and an *after* of 0 as the start, where VB raises 9; the owner takes those as extensions.
+
+<!-- Reproducer: bugs/collection-index-checks/ (mode test: `tbrun --tests`; expect lists the three PASS and fourteen FAIL lines); verified on BETA 1010; 64-bit and 64-bit VBA from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB's number for each case. Stated in the Common Errors sections (rows `bug: collection-index-checks` in errors/VBA.Collection.yml) of Add, Item and Remove under docs/Reference/Default/VBA/Collection/; when fixed, each row's cases move to a row of VB's number (the Currency, Decimal and Date ones to the quiet cases), and the NOTEs go. Found 2026-10-27 by batch 8 of WIP.Errors.md; owner, 2026-10-28: the `Empty` key is a bug, while a *before* of Count + 1 and an *after* of 0 are extensions (a NOTE on Add.md). -->
+
+---
+
+## `Rate` raises -2147467259 for almost every annuity, and returns -2.1 for a lump sum where VB6 returns 0.1
+
+**Describe the bug**
+`Rate` raises -2147467259 (`&H80004005`), *Unspecified error*, for almost every annuity that VB6 and 64-bit VBA solve: a loan (`Rate(10, -100, 800)` is 0.0427749780351145 in VB6), a mortgage (`Rate(360, -600, 100000)`), a savings plan (`Rate(10, -100, 0, 1200)`), payments due at the start of the period, the signs reversed, a *guess* given, and a lump sum over ten periods (`Rate(10, 0, 1000, -2000)`). Of the annuities tried, it answers only some lump sums (a *pmt* of 0), such as those over one to four periods, and for an even number of periods it returns the wrong root: `Rate(2, 0, 100, -121)` and `Rate(4, 0, 100, -146.41)` are -2.1, where VB6 returns 0.1. (-2.1 also solves the equation, but no annuity has a rate below -1.)
+
+Also:
+- With an *nper* below 1 and a *pmt* of 0 it raises 5, *Invalid procedure call or argument*; VB6 returns the rate (`Rate(0.5, 0, 100, -110)` is 0.21).
+- It does not check *guess*: a *guess* of `Null`, a string that is not a number, or an error value raises nothing, where VB raises 94, *Invalid use of Null*, and 13, *Type mismatch*.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `rate-fails.twinproj` (attached as `rate-fails.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other twelve fail.
+
+The module is meant to be adapted as a regression test. Each case asserts what VB6 returns or raises, which the attached VB6 project (`rate-fails-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: Rate returns the rate of an annuity, as VB6 and 64-bit VBA do, for a loan,
+' a mortgage, a savings plan, payments due at the start, a guess and an nper below 1, and
+' the positive rate (0.1, not -2.1) of a lump sum over an even number of periods; and it raises
+' 94 for a guess of Null and 13 for a guess that is not a number. The controls are two
+' lump sums Rate answers rightly (one and three periods) and a Null nper.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_PmtZeroOnePeriod()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_PmtZeroThreePeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(3, 0, 100, -133.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_NperNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(Null, -100, 800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroTwoPeriods_ReturnsPositiveRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(2, 0, 100, -121)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroFourPeriods_ReturnsPositiveRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(4, 0, 100, -146.41)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Loan_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Mortgage_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(360, -600, 100000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0050058250068) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub DueAtStart_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800, 0, 1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.053446167382) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SavingsPlan_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 0, 1200)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0398902762) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SignsReversed_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, 100, -800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroTenPeriods_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, 0, 1000, -2000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0717734625363) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub WithGuess_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800, 0, 0, 0.04)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub NperBelowOne_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(0.5, 0, 100, -110)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.21) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub GuessNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub GuessString_Raises13()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, 0, "abc")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+The rate VB6 and 64-bit VBA return, found from the default *guess* of 0.1 or from the one given: 0.0427749780351145 for `Rate(10, -100, 800)`, 0.1 for `Rate(2, 0, 100, -121)`, 0.21 for `Rate(0.5, 0, 100, -110)`; and 94 or 13 for a *guess* of `Null` or one that is not a number.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: high. `Rate` cannot be used for a loan or a savings plan, its main use, and where it does answer it can return a rate below -1 with no error.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+Related: the queued entry on refused arguments (`argument-errors-unspecified-error`) covers `Rate`'s -2147467259 where VB raises 5 or 6 (no result in 20 tries, an *nper* of 0 or less); this one is about the annuities that have a rate.
+
+What does not reproduce it: a lump sum over one or three periods (`Rate(1, 0, 100, -110)` and `Rate(3, 0, 100, -133.1)` are 0.1); `Null` in *nper*, *pmt* or *pv* (94 in all).
+
+<!-- Reproducer: bugs/rate-fails/ (mode test: `tbrun --tests`; expect lists the three PASS and twelve FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; 64-bit VBA's numbers from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0): `bug_repro.mjs vb6` prints VB6's number and value for each case. Stated in the Common Errors section (rows `bug: rate-fails` in errors/VBA.Financial.yml) and a WARNING (BETA 1010, the wrong root) of docs/Reference/Default/VBA/Financial/Rate.md; when fixed, the rows' cases move to the quiet cases (the *guess* ones to rows of 94 and 13), and the NOTEs and the WARNING go. Found 2026-10-28 by batch 9 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## `NPer` raises error 6 for a loan or a savings plan, where VB6 returns the number of periods
+
+**Describe the bug**
+Given a *rate* and a *pmt* of opposite signs, as in every loan or savings plan at a positive rate, `NPer` raises 6, *Overflow*, where VB6 and 64-bit VBA return the number of periods. `NPer(0.01, -100, 1000)`, a loan of 1000 repaid at 100 a period at 1% a period, is 10.5886444594232 in VB6; so are a car loan (`NPer(0.1 / 12, -500, 20000)`, 48.86), a loan with a balance left (*fv*), one with payments due at the start, a savings plan (`NPer(0.01, -100, 0, 1000)`, 9.58) and a negative rate with a positive payment (`NPer(-0.5, 100, -1000)`, 2.58).
+
+Where no number of periods exists, it raises 6 (a payment that does not cover the interest, `NPer(0.01, -1, 1000)`) or 11, *Division by zero* (a *pmt* of 0, a *rate* of -1), where VB raises 5, *Invalid procedure call or argument*.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `nper-opposite-signs-overflow.twinproj` (attached as `nper-opposite-signs-overflow.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other nine fail.
+
+The module is meant to be adapted as a regression test. Each case asserts what VB6 returns or raises, which the attached VB6 project (`nper-opposite-signs-overflow-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: NPer returns the number of periods of a loan or a savings plan, as VB6 and
+' 64-bit VBA do, whatever the signs of rate and pmt, and raises 5 where no number of periods
+' exists. The controls have rate and pmt of the same sign, or a rate of 0.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_PositivePmt()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, -1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RateZero()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SameSigns()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - -9.57859403981317) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Loan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub CarLoan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.1 / 12, -500, 20000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 48.8582651211073) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub LoanWithBalance_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000, 100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 11.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub LoanDueAtStart_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000, 0, 1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.4781450851168) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SavingsPlan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 9.57859403981317) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub NegativeRate_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(-0.5, 100, -1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 2.58496250072116) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtBelowInterest_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -1, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub RateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(-1, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+The number of periods VB6 and 64-bit VBA return, whatever the signs of *rate* and *pmt*, and 5 where no number of periods exists.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: high. `NPer` fails for a loan, its main use. An error is raised, so no wrong value reaches the program.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+Related: the queued entry on refused arguments (`argument-errors-unspecified-error`) covers `NPer` with a *rate* and a *pmt* of 0 (-2147467259; VB 5).
+
+What does not reproduce it: a *rate* and a *pmt* of the same sign (`NPer(0.01, 100, -1000)` is 10.5886444594232, and `NPer(0.01, 100, 1000)` is -9.57859403981317, as in VB6); a *rate* of 0 (`NPer(0, -100, 1000)` is 10).
+
+<!-- Reproducer: bugs/nper-opposite-signs-overflow/ (mode test: `tbrun --tests`; expect lists the three PASS and nine FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; 64-bit VBA's numbers from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0). Stated in the Common Errors section (rows `bug: nper-opposite-signs-overflow` in errors/VBA.Financial.yml) of docs/Reference/Default/VBA/Financial/NPer.md; when fixed, the first row's cases move to the quiet cases, the others become a row of 5, and the NOTEs go. Found 2026-10-28 by batch 9 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## `Null` in an optional argument of a Financial function raises 13, where VB6 raises 94
+
+**Describe the bug**
+Given `Null` as an optional argument --- *pv*, *fv* or *type* of `FV`, `PV`, `Pmt`, `NPer`, `IPmt`, `PPmt` and `Rate`, or *factor* of `DDB` --- these functions raise 13, *Type mismatch*. VB6 and 64-bit VBA raise 94, *Invalid use of Null*, as twinBASIC itself does for `Null` in a required argument.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `financial-null-optional-argument.twinproj` (attached as `financial-null-optional-argument.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other nine fail, each with `Err.Number` 13.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`financial-null-optional-argument-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: a Null optional argument of a Financial function (pv, fv, type, factor)
+' raises 94, Invalid use of Null, as VB6 and 64-bit VBA do. The controls are a Null required
+' argument (94), a string that is not a number (13) and a number in the optional argument.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_RequiredNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(Null, 10, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_OptionalString_Raises13()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, "abc")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_OptionalNumber()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub FV_PvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub FV_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(0.01, 10, -100, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(0.01, 10, 1000, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPer_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, -1000, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 1, 10, 1000, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 1, 10, 1000, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub DDB_FactorNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 5, 1, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+94, *Invalid use of Null*, as VB6 and 64-bit VBA raise.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low. An error is raised where VB raises one, with another number.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: `Null` in a required argument (94 in all); a string that is not a number in an optional argument (13 in all).
+
+<!-- Reproducer: bugs/financial-null-optional-argument/ (mode test: `tbrun --tests`; expect lists the three PASS and nine FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; 64-bit VBA's numbers from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0). Stated in the Common Errors sections (rows `bug: financial-null-optional-argument` in errors/VBA.Financial.yml) of DDB, FV, IPmt, NPer, PPmt, PV, Pmt and Rate under docs/Reference/Default/VBA/Financial/; when fixed, each row becomes a row of 94 and its NOTE goes. Found 2026-10-28 by batch 9 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## `IRR`, `MIRR` and `NPV` end the program for an array that has never been sized, and raise &H8000FFFF for one of two dimensions
+
+**Describe the bug**
+Given a `Double` array that has never been sized (`Dim A() As Double` with no `ReDim`), or one emptied by `Erase`, `IRR`, `MIRR` and `NPV` end the program with an access violation, in a built exe and in the IDE, 32-bit and 64-bit. In the compiler's test mode the case reports `NATIVE EXCEPTION: ACCESS_VIOLATION`. VB6 and 64-bit VBA raise 5, *Invalid procedure call or argument*.
+
+Given an array of two dimensions, they raise -2147418113 (`&H8000FFFF`), *Catastrophic failure*, where VB raises 5.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `financial-array-arguments.twinproj` (attached as `financial-array-arguments.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass, the four unsized cases end with an access violation, and the three two-dimensional ones fail with `Err.Number` -2147418113.
+
+The module is meant to be adapted as a regression test. Each case asserts VB6's number, which the attached VB6 project (`financial-array-arguments-vb6.zip`) prints; 64-bit VBA raises the same numbers.
+```vb
+' Regression tests: IRR, MIRR and NPV raise 5, Invalid procedure call or argument, for an
+' array that has never been sized or has been erased, and for one of two dimensions, as VB6
+' and 64-bit VBA do. On BETA 1010 the unsized cases end with an access violation. The
+' controls are each function of a sized one-dimensional array.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_IRR()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = -100
+        A(1) = 110
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_MIRR()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0723805294763609) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_NPV()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = NPV(0.1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - -4.50788880540947) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_Erased_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = -100
+        A(1) = 110
+        Erase A
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPV(0.1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = IRR(B)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = MIRR(B, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = NPV(0.1, B)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+5, *Invalid procedure call or argument*, as VB6 and 64-bit VBA raise, for an array that has never been sized, has been erased, or has more than one dimension.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: high for the access violation: the program ends without a chance to save its data, and an array that is filled later, or emptied by `Erase`, is an ordinary state for one passed to these functions. Low for the two dimensions.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: a sized one-dimensional array, whatever its lower bound (`Dim A(1 To 3) As Double` works).
+
+<!-- Reproducer: bugs/financial-array-arguments/ (mode test: `tbrun --tests`; expect lists the three PASS lines, four FAIL lines with ACCESS_VIOLATION and three with -2147418113); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; the crash also in built exes (`errors.mjs run`), and 64-bit VBA's numbers from the run-time errors data. VB6 side in vb6/ (VB6 6.0). Stated in a WARNING (BETA 1010) each on docs/Reference/Default/VBA/Financial/IRR.md, MIRR.md and NPV.md, for the crash, and in their Common Errors sections (rows `bug: financial-array-arguments` in errors/VBA.Financial.yml), for two dimensions; when fixed, the WARNINGs go, the unsized cases join a row of 5 with the two-dimensional ones, and the NOTEs go. Found 2026-10-28 by batch 9 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## `IPmt`, `PPmt`, `MIRR`, `NPV`, `DDB`, `Pmt`, `FV`, `PV` and `SLN` check their arguments differently from 64-bit VBA
+
+**Describe the bug**
+Given these arguments, the Financial functions do something other than 64-bit VBA:
+- `IPmt` and `PPmt` take any *per*. For a *per* of 0 or less, or of *nper* + 1 or more, they return a value computed for a period outside the annuity (`IPmt(0.01, 0, 10, 1000)` is -10.946357193576) and raise nothing; VB raises 5, *Invalid procedure call or argument*.
+- `MIRR` returns -1 for *values* of one element and a rate for a *finance_rate* or *reinvest_rate* of -1, where VB raises 5; and infinity or NaN for *values* with no element less than 0, where VB raises 11, *Division by zero*.
+- `NPV` returns NaN for a *rate* of -1; VB raises 5.
+- `DDB` raises -2147467259 (`&H80004005`), *Unspecified error*, for a *life* greater than 0 and less than 1; VB returns the depreciation (`DDB(1000, 100, 0.5, 0.5)` is 900).
+- `Pmt` and `PPmt` raise 11 for an *nper* of 0; VB raises 5.
+- With a *rate* of -1, `FV` raises 5 for a negative *nper*, where 64-bit VBA raises 6, *Overflow* (VB6 11), and `PV` raises -2147467259, where 64-bit VBA returns 0 for an *nper* of 0 and raises 11 for a positive *nper* and 6 for a negative one (VB6 raises nothing, and returns 0, infinity or NaN).
+- `SLN` returns infinity for a result beyond the range of a `Double` (`SLN(1000, 100, 1E-308)`), where 64-bit VBA raises 6 (VB6 returns infinity).
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `financial-argument-checks.twinproj` (attached as `financial-argument-checks.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other sixteen fail.
+
+The module is meant to be adapted as a regression test. Each case asserts 64-bit VBA's number. The attached VB6 project (`financial-argument-checks-vb6.zip`) prints VB6's, which are the same but for the four cases of `FV`, `PV` and `SLN` that the list above gives.
+```vb
+' Regression tests: the Financial functions check their arguments as 64-bit VBA does: 5 for a
+' period outside 1 to nper (IPmt, PPmt), for an nper of 0 (Pmt, PPmt), for MIRR of one element
+' or a rate of -1, and for NPV at a rate of -1; 11 for MIRR with no payment; a DDB of a life
+' below 1; and with a rate of -1, FV's 6 and PV's 0, 11 and 6; SLN's 6 for an infinite result.
+' VB6 agrees but for FV (11), PV and SLN (no error, infinity). The controls pass in all.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_IPmtLastPeriod()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 10.9999999, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_PmtRateMinusTwo_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(-2, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_DDBLifeOne()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 1, 0.5)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 900) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_PerZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 0, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_PerNperPlusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 11, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_PerZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 0, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_PerNperPlusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 11, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_NperZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(0.01, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_NperZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 1, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_OneElement_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(0)
+        A(0) = -100
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_ReinvestRateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = MIRR(A, 0.1, -1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_NoPayment_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = 100
+        A(1) = 110
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_RateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = NPV(-1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub DDB_LifeBelowOne_Returns900()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 0.5, 0.5)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 900) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub FV_RateMinusOneNegativeNper_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(-1, -1, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOneNperZero_Returns0()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, 0, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOne_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, 10, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOneNegativeNper_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, -1, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+    [TestCase]
+    Public Sub SLN_InfiniteResult_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = SLN(1000, 100, 1E-308)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+The numbers 64-bit VBA gives, as listed above. Where VB6 and 64-bit VBA differ (`FV`, `PV`, `SLN`), twinBASIC is to do as 64-bit VBA does.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: medium for `IPmt`, `PPmt`, `MIRR` and `NPV`, which return a value with no error for arguments VB refuses, so a mistake in a program goes unnoticed. Low for the rest: an error is raised where VB raises one, with another number, or (`DDB`) a value VB computes is refused.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+Related: the queued entry on refused arguments (`argument-errors-unspecified-error`) covers these functions' -2147467259 where VB raises 5.
+
+What does not reproduce it: a *per* just below *nper* + 1 (`IPmt(0.01, 10.9999999, 10, 1000)`); `Pmt` with a *rate* of -2 and an even *nper* (11 in all); `DDB` with a *life* of 1. `PV` already raises 11 for a result beyond the range of a `Double`, as 64-bit VBA does (VB6 returns infinity).
+
+<!-- Reproducer: bugs/financial-argument-checks/ (mode test: `tbrun --tests`; expect lists the three PASS and sixteen FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; 64-bit VBA's numbers from the run-time errors data (`errors.mjs run`, all four runtimes). VB6 side in vb6/ (VB6 6.0). Stated in the Common Errors sections (rows `bug: financial-argument-checks` in errors/VBA.Financial.yml) of DDB, FV, IPmt, MIRR, NPV, PPmt, PV, Pmt and SLN under docs/Reference/Default/VBA/Financial/, and in WARNINGs (BETA 1010) on IPmt, PPmt, MIRR and NPV for the values returned with no error; when fixed, each row becomes a row of 64-bit VBA's number (DDB's to the quiet cases), and the NOTEs and WARNINGs go. Found 2026-10-28 by batch 9 of WIP.Errors.md; owner, 2026-10-28: a bug, twinBASIC to do as 64-bit VBA where VB6 and 64-bit VBA differ; PV's 11 for a result beyond the range of a Double is that, not a bug. -->
+
+---
+
+## `ConvertIconToBitmap`, `GetInheritedOwner`, `AddCustomBinder` and `AddCustomBinderObject` end the program when given `Nothing`
+
+**Describe the bug**
+Five calls end the program with an access violation, in a built exe and in the IDE, 32-bit and 64-bit; in the compiler's test mode the case reports `NATIVE EXCEPTION: ACCESS_VIOLATION`:
+
+- `ConvertIconToBitmap(Nothing)`. Given any other object that is not an icon (a `Collection`, a bitmap picture) it raises -2147467259, as it should.
+- `GetInheritedOwner(Nothing)`, and `GetInheritedOwner` of an object that is not a control: a `Collection` in both builds, a `Scripting.Dictionary` in a 64-bit build (in a 32-bit one it returns).
+- `TbExpressionService.AddCustomBinder Nothing`.
+- `TbExpressionService.AddCustomBinderObject "D", Nothing`.
+- `V = RuntimeCreateGetMessageHook()`, a `Let` of the hook object into a `Variant`. `Set V = RuntimeCreateGetMessageHook()` works, and so does a `Let` of the same object held in a variable declared `As IGetMessageHook`; a `Let` of an object of a twinBASIC class behind an interface without `IDispatch` stores it with no error, so the fault is in the hook object.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `nothing-argument-crashes.twinproj` (attached as `nothing-argument-crashes.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the other seven end with an access violation; the `Scripting.Dictionary` case passes in a 32-bit build.
+
+The module is meant to be adapted as a regression test. A case asserts only that an error is raised (or, for `GetInheritedOwner`, that it returns `Nothing`), not which: VB6 and VBA have none of these procedures.
+```vb
+' Regression tests: given Nothing, or an object they cannot use, ConvertIconToBitmap,
+' GetInheritedOwner, TbExpressionService.AddCustomBinder and AddCustomBinderObject raise a
+' run-time error (or, for GetInheritedOwner, return Nothing) instead of ending the program
+' with an access violation; and the object RuntimeCreateGetMessageHook returns can be
+' assigned to a Variant without Set, as any other object without IDispatch can. On BETA 1010
+' each case but the controls ends with an access violation, 32-bit and 64-bit.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Declare PtrSafe Function LoadIconW Lib "user32" (ByVal Inst As LongPtr, ByVal Name As LongPtr) As LongPtr
+
+    ' The controls: each procedure working, or refusing an argument with an error.
+    [TestCase]
+    Public Sub Control_ConvertIconToBitmap_Icon()
+        Dim Icon As StdPicture = CreateStdPictureFromHandle(LoadIconW(0, 32512), vbPicTypeIcon, False)
+        Assert.Strict.AreEqual CLng(vbPicTypeBitmap), CLng(ConvertIconToBitmap(Icon).Type)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ConvertIconToBitmap_NotAPicture_Raises()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = ConvertIconToBitmap(New Collection)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual -2147467259, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_AddCustomBinderObject_Object()
+        Dim S As New TbExpressionService
+        S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary")
+        Assert.Strict.AreEqual 0, CInt(S.Compile("D.Count").Evaluate())
+    End Sub
+
+    [TestCase]
+    Public Sub ConvertIconToBitmap_Nothing_RaisesAnError()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = ConvertIconToBitmap(Nothing)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Nothing_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(Nothing)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Collection_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(New Collection)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Dictionary_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(CreateObject("Scripting.Dictionary"))
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub AddCustomBinder_Nothing_RaisesAnError()
+        Dim S As New TbExpressionService
+        Dim E As Long
+        On Error Resume Next
+        S.AddCustomBinder Nothing
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub AddCustomBinderObject_Nothing_RaisesAnError()
+        Dim S As New TbExpressionService
+        Dim E As Long
+        On Error Resume Next
+        S.AddCustomBinderObject "D", Nothing
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub RuntimeCreateGetMessageHook_LetIntoVariant_StoresTheObject()
+        Dim V As Variant
+        V = RuntimeCreateGetMessageHook()
+        Assert.Strict.AreEqual CInt(vbDataObject), VarType(V)
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+A run-time error for **Nothing**, as `GetNameFromDispID(Nothing, 0)` raises -2147467261, *Invalid pointer*, and as VB's `CallByName` raises 5 for an object of **Nothing**; for `GetInheritedOwner`, an error or **Nothing**. A `Let` of the hook object into a `Variant` stores it, as a `Let` of any other object without `IDispatch` does.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: high: the program ends without a chance to save its data, and an object variable that is still **Nothing** is an ordinary mistake that an error handler should be able to catch.
+
+A 64-bit build gives the same results, but for `GetInheritedOwner` of a `Scripting.Dictionary` (above).
+
+What does not reproduce it: any of these procedures given the object it is meant for (the controls), or an object of the wrong kind other than those named (`ConvertIconToBitmap` of a bitmap or a `Collection` raises -2147467259).
+
+<!-- Reproducer: bugs/nothing-argument-crashes/ (mode test: `tbrun --tests`; expect lists the three PASS lines, six FAIL lines with ACCESS_VIOLATION and the Dictionary case as either); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; the crashes also in built exes (`errors.mjs run` while exploring). No VB6 side: VB6 and VBA have none of these procedures. Stated in a WARNING (BETA 1010) each on docs/Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md, GetInheritedOwner.md and RuntimeCreateGetMessageHook.md, and docs/Reference/Default/VBA/TbExpressionService/AddCustomBinder.md and AddCustomBinderObject.md; when fixed, the WARNINGs go, and the error each raises becomes a row in errors/VBA.HiddenModule.yml or VBA.TbExpressionService.yml. Found 2026-10-28 by batch 10 of WIP.Errors.md; owner, 2026-10-28: a bug, one entry, GetInheritedOwner of a non-control included. -->
+
+---
+
+## `Eval` and `TbExpressionService.Compile` accept an expression that ends in an operator or has an unmatched parenthesis
+
+**Describe the bug**
+`Eval` and `TbExpressionService.Compile` accept some malformed expressions without an error: the part they cannot read is left out, and the value is that of what comes before it. `Eval("2 +")`, `Eval("2 Mod")`, `Eval("(2")` and `Eval("2)")` each return 2, and `Compile` of each gives an expression whose value is 2. Other malformed expressions are refused with -2147467259: `"1 2"`, `"2 * (3 + 4"`, `"Sqr(4"`, `")"`.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `expression-service-dangling-tokens.twinproj` (attached as `expression-service-dangling-tokens.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the eight other cases fail: no error is raised.
+
+The module is meant to be adapted as a regression test. A case asserts only that an error is raised, not which.
+```vb
+' Regression tests: Eval and TbExpressionService.Compile refuse a malformed expression with a
+' run-time error, as they refuse "1 2", instead of leaving out the part they cannot read. On
+' BETA 1010 an expression that ends in an operator, or has a parenthesis with no partner at
+' either end, is accepted, and its value is that of what comes before the fault: each case
+' below gives 2. VBScript's Eval refuses each with 1002, Syntax error, or 1006, Expected ')';
+' Access's Eval with 2431, 2435 or 2436.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function EvalError(ByVal Source As String) As Long
+        Dim V As Variant
+        On Error Resume Next
+        V = Eval(Source)
+        EvalError = Err.Number
+    End Function
+
+    Private Function CompileError(ByVal Source As String) As Long
+        Dim S As New TbExpressionService
+        Dim E As ITbExpression
+        S.AddStdLibraryBinder
+        On Error Resume Next
+        Set E = S.Compile(Source)
+        CompileError = Err.Number
+    End Function
+
+    ' The controls: a well-formed expression, and malformed ones that are refused.
+    [TestCase]
+    Public Sub Control_Eval_WellFormed()
+        Assert.Strict.AreEqual 2, CInt(Eval("(2)"))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Eval_TwoNumbers_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("1 2")
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Compile_UnclosedAfterOperator_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 * (3 + 4")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_TrailingPlus_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2 +")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_TrailingMod_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2 Mod")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_UnclosedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("(2")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_UnopenedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2)")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_TrailingPlus_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 +")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_TrailingMod_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 Mod")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_UnclosedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("(2")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_UnopenedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2)")
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+A run-time error for each, as for `"1 2"`. VBScript's `Eval` (through `MSScriptControl.ScriptControl` in VB6) raises 1002, *Syntax error*, for `"2 +"`, `"2 Mod"` and `"2)"`, and 1006, *Expected ')'*, for `"(2"`; Access's `Eval` in 64-bit VBA raises 2431, *The expression you entered contains invalid syntax.*, 2436 (a missing closing parenthesis) and 2435 (too many closing parentheses).
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: medium: a wrong value with no error, for text a user typed, the very input an expression service is given.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: two operands with no operator (`"1 2"`), an unclosed parenthesis after an operator (`"2 * (3 + 4"`, `"2 + (3"`), an unclosed argument list (`"Sqr(4"`), a lone `")"`, `"+"` or `"-"`. `"2 *"` is accepted, `"2 * "` with a trailing space is refused.
+
+Related: the queued entry `expression-service-error-numbers`, on the number these functions raise.
+
+<!-- Reproducer: bugs/expression-service-dangling-tokens/ (mode test: `tbrun --tests`; expect lists the three PASS and eight FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; VBScript's numbers from VB6 with MSScriptControl, Access's from VbaSession (scripts/lib/vba.mjs). No VB6 side: VB6 has no Eval. Stated in a WARNING (BETA 1010) each on docs/Reference/Default/VBA/HiddenModule/Eval.md and docs/Reference/Default/VBA/TbExpressionService/Compile.md, and as quiet cases (comment `bugs/expression-service-dangling-tokens`) in errors/VBA.HiddenModule.yml and VBA.TbExpressionService.yml; when fixed, the WARNINGs go and the quiet cases join Eval's and Compile's rows of the error raised. Found 2026-10-28 by batch 10 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## `Eval` and `ITbExpression.Evaluate` raise -2147467259 for every error inside the expression, instead of passing it on unchanged
+
+**Describe the bug**
+An error that a function, an operator or a bound object's member raises while `Eval` or `ITbExpression.Evaluate` evaluates an expression does not reach the caller as it was raised. Whatever it was, the caller gets -2147467259 (`&H80004005`): `Eval("1 / 0")` raises -2147467259, not 11, *Division by zero*; `CInt("abc")` in an expression not 13, `CInt(40000)` not 6, `Sqr(-1)` not 5; and a bound object's error, a `Scripting.Dictionary`'s `Add` of a key it holds, not 457. Each of these raises its own number when the same code is written in a procedure.
+
+The description is lost with the number: in a built exe the first such error of the process has the description *Automation error* and every later one *Unspecified error*; in the IDE every one has *Automation error*.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `expression-service-error-numbers.twinproj` (attached as `expression-service-error-numbers.zip`).
+2. Run its test cases, the module below. On BETA 1010 the two controls pass and the seven other cases fail, each with -2147467259 (and the description case with *Automation error*).
+
+The module is meant to be adapted as a regression test. Each case asserts the number, or the description, that the same code raises written in a procedure.
+```vb
+' Regression tests: an error raised by a function, an operator or a bound object's member
+' while Eval or ITbExpression.Evaluate evaluates an expression reaches the caller unchanged,
+' with the number and description the same code raises written in a procedure, as VBScript's
+' Eval and Access's Eval pass it on. On BETA 1010 each of these raises -2147467259, whose
+' description is "Automation error" in the IDE and in an exe's first such error, and
+' "Unspecified error" after it.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function EvalError(ByVal Source As String) As Long
+        Dim V As Variant
+        On Error Resume Next
+        V = Eval(Source)
+        EvalError = Err.Number
+    End Function
+
+    ' The controls: an expression that raises nothing, and a bound object's error raised by
+    ' the same call written in a procedure.
+    [TestCase]
+    Public Sub Control_Eval_Sum()
+        Assert.Strict.AreEqual 4, CInt(Eval("2 + 2"))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_DictionaryAddOfAKeyItHolds_Raises457()
+        Dim D As Object = CreateObject("Scripting.Dictionary")
+        Dim E As Long
+        D.Add 1, 1
+        On Error Resume Next
+        D.Add 1, 2
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 457&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_DivisionByZero_Raises11()
+        Assert.Strict.AreEqual 11&, EvalError("1 / 0")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_DivisionByZero_DescriptionIsDivisionByZero()
+        Dim V As Variant, D As String
+        On Error Resume Next
+        V = Eval("1 / 0")
+        D = Err.Description
+        On Error GoTo 0
+        Assert.Strict.AreEqual "Division by zero", D
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_CIntOfText_Raises13()
+        Assert.Strict.AreEqual 13&, EvalError("CInt(""abc"")")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_CIntOverflow_Raises6()
+        Assert.Strict.AreEqual 6&, EvalError("CInt(40000)")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_SqrOfNegative_Raises5()
+        Assert.Strict.AreEqual 5&, EvalError("Sqr(-1)")
+    End Sub
+
+    [TestCase]
+    Public Sub Evaluate_DivisionByZero_Raises11()
+        Dim S As New TbExpressionService
+        Dim X As ITbExpression, V As Variant, E As Long
+        S.AddStdLibraryBinder
+        Set X = S.Compile("1 / 0")
+        On Error Resume Next
+        V = X.Evaluate()
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Evaluate_BoundObjectsError_Raises457()
+        Dim S As New TbExpressionService
+        Dim D As Object = CreateObject("Scripting.Dictionary")
+        Dim X As ITbExpression, V As Variant, E As Long
+        D.Add 1, 1
+        S.AddCustomBinderObject "D", D
+        Set X = S.Compile("D.Add(1, 2)")
+        On Error Resume Next
+        V = X.Evaluate()
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 457&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+The error reaches the caller unchanged, with the number and description it has when the same code is written in a procedure: `Eval` and `Evaluate` add nothing of their own. That is what the VB family's expression evaluators do: Access's `Eval` in 64-bit VBA raises 11, 13, 6 and 5 for the four `Eval` cases, with the same descriptions as direct code, and VBScript's `Eval` (through `MSScriptControl.ScriptControl` in VB6) the same numbers.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: medium: an error handler cannot tell a division by zero from a type mismatch or a bound object's own error, and a handler written for one number never runs. The class's own documentation says an error inside the expression propagates out of `Evaluate` like any other run-time error.
+
+A 64-bit build gives the same results. 64-bit VBA here is VBA 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: an expression that raises nothing.
+
+Related: the queued entry `expression-service-dangling-tokens`, on malformed expressions that are accepted.
+
+<!-- Reproducer: bugs/expression-service-error-numbers/ (mode test: `tbrun --tests`; expect lists the two PASS and seven FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`; the descriptions in exes with `tbrun --exe` and `errors.mjs run`; VBScript's numbers from VB6 with MSScriptControl, Access's from VbaSession (scripts/lib/vba.mjs). No VB6 side: VB6 has no Eval. Stated in the first NOTE (BETA 1010) on docs/Reference/Default/VBA/HiddenModule/Eval.md and on docs/Reference/Default/VBA/TbExpressionService/Evaluate.md, and in their Common Errors sections (the rows of errors raised while evaluating, -2147467259, in errors/VBA.HiddenModule.yml and VBA.TbExpressionService.yml); when fixed, those rows become the errors' own numbers and the NOTEs go. Not in this entry (owner, 2026-10-28: it asks only that errors pass through unchanged): a compile failure's number and description, `Eval("Len(Null)")` and `Eval("CVErr(5)")`, and the description NOTEs with the `expression` harness. Found 2026-10-28 by batch 10 of WIP.Errors.md; owner, 2026-10-28: Eval is not to special-case errors, unless VB does, which it does not. -->
+
+---
+
+## `vbaCastObj` returns `Nothing` for an interface the object does not have, where VB6's `__vbaCastObj` raises 13
+
+**Describe the bug**
+`vbaCastObj(Obj, IID)` asks *Obj* for the interface whose ID is at the address *IID*. When *Obj* does not have it, `vbaCastObj` returns `Nothing` and raises no error. VB6's own `__vbaCastObj`, which msvbvm60 exports and which `vbaCastObj` mirrors, raises 13, *Type mismatch*, there: it is the function VB6's compiled code calls for a `Set` to a variable of an interface type, and the 13 is the error that `Set` raises. A `String` given as *IID* is the same case: its text is read as the interface ID, which no object has, so VB6 raises 13 and twinBASIC returns `Nothing`.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `vbacastobj-no-type-mismatch.twinproj` (attached as `vbacastobj-no-type-mismatch.zip`).
+2. Run its test cases, the module below. On BETA 1010 the three controls pass and the two other cases fail: `Err.Number` is 0.
+3. Build and run the VB6 project (attached as `vbacastobj-no-type-mismatch-vb6.zip`), which calls `__vbaCastObj` through a `Declare` with the same arguments. It prints:
+   ```
+   Control_IUnknown_ReturnsTheInterface: 0 an interface
+   Control_IDispatch_ReturnsTheInterface: 0 an interface
+   Control_Nothing_ReturnsNothing: 0 Nothing
+   InterfaceItLacks_Raises13: 13 Nothing
+   StringGivenAsTheInterfaceId_Raises13: 13 Nothing
+   ```
+
+The module is meant to be adapted as a regression test. Each case asserts what VB6's `__vbaCastObj` does.
+```vb
+' Regression tests: vbaCastObj raises 13, Type mismatch, when the object does not have the
+' interface asked for, as VB6's own __vbaCastObj (msvbvm60) does, and still returns the
+' interface when it does, and Nothing for Nothing. On BETA 1010 it returns Nothing with no
+' error, for an interface the object lacks and for a String given as the interface ID (whose
+' text is not an interface ID). The VB6 project beside this one calls __vbaCastObj with the
+' same arguments.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Type InterfaceGuid
+        Data1 As Long
+        Data2 As Integer
+        Data3 As Integer
+        Data4(0 To 7) As Byte
+    End Type
+
+    Private Iid As InterfaceGuid
+
+    ' The address of the interface ID {Data1-0000-0000-C000-000000000046}: 0 is IUnknown,
+    ' &H20400 IDispatch, &H12345 an interface nothing has.
+    Private Function StdIid(ByVal Data1 As Long) As LongPtr
+        Iid.Data1 = Data1
+        Iid.Data4(0) = &HC0
+        Iid.Data4(7) = &H46
+        StdIid = VarPtr(Iid)
+    End Function
+
+    [TestCase]
+    Public Sub Control_IUnknown_ReturnsTheInterface()
+        Assert.Strict.IsNotNothing vbaCastObj(New Collection, StdIid(0))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_IDispatch_ReturnsTheInterface()
+        Assert.Strict.IsNotNothing vbaCastObj(New Collection, StdIid(&H20400))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Nothing_ReturnsNothing()
+        Assert.Strict.IsNothing vbaCastObj(Nothing, StdIid(0))
+    End Sub
+
+    [TestCase]
+    Public Sub InterfaceItLacks_Raises13()
+        Dim E As Long, U As IUnknown
+        On Error Resume Next
+        Set U = vbaCastObj(New Collection, StdIid(&H12345))
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+    [TestCase]
+    Public Sub StringGivenAsTheInterfaceId_Raises13()
+        Dim E As Long, U As IUnknown
+        On Error Resume Next
+        Set U = vbaCastObj(New Collection, "{00000000-0000-0000-C000-000000000046}")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+13, *Type mismatch*, as VB6's `__vbaCastObj` raises, when the object does not have the interface; the interface when it does; `Nothing` for an object of `Nothing`, as now.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low to medium: code ported from VB6 that relies on the 13 from `__vbaCastObj` goes on with `Nothing`, and code that passes the IID as text, as the function's documentation once said it could, always gets `Nothing` and never learns why.
+
+A 64-bit build gives the same results. 64-bit VBA cannot be compared: VBE7.DLL exports no `__vba` function.
+
+What does not reproduce it: an interface the object has (`IUnknown`, `IDispatch` of a `Collection`), and an object of `Nothing`, for which both return `Nothing` with no error.
+
+<!-- Reproducer: bugs/vbacastobj-no-type-mismatch/ (mode test: `tbrun --tests`; expect lists the three PASS and two FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`. VB6 side in vb6/ (VB6 6.0), calling msvbvm60's __vbaCastObj. Stated in a WARNING (BETA 1010) on docs/Reference/Default/VBA/HiddenModule/vbaCastObj.md, and in its Common Errors section (row `bug: vbacastobj-no-type-mismatch`, error 0, vb6 13, in errors/VBA.HiddenModule.yml); when fixed, the row becomes a row of 13 with no vb6:, and the WARNING and the NOTE go. Found 2026-10-28 by batch 10 of WIP.Errors.md; owner, 2026-10-28: a bug. -->
+
+---
+
+## Assigning `Nothing` without `Set` to a variable that is not an object, or comparing with `Nothing` by `=`, compiles, where VB6 and VBA refuse it
+
+**Describe the bug**
+`Nothing` is an object reference: it is assigned with `Set` and compared with `Is`. VB6 and 64-bit VBA refuse, when they compile, a Let of `Nothing` to a variable that is neither an object nor a `Variant` (`Count = Nothing` for a `Long`, a `String` or a `Boolean`), and `Nothing` as an operand of `=` or `<>` (`If Obj = Nothing`, `Count <> Nothing`), each with *Invalid use of object*. twinBASIC compiles every one of them with no diagnostic, and each raises 91, *Object variable or With block variable not set*, when it runs. An error the compiler could report is put off until the line runs, so a mistake on a path that rarely runs is found late or not at all.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `nothing-let-compiles.twinproj` (attached as `nothing-let-compiles.zip`).
+2. Compile it. On BETA 1010 it compiles with no error. The module's five lines marked `error` are each one of the forms above; the three marked `none` are the forms VB6 and VBA compile too (`Set Items = Nothing`, `Items Is Nothing`, `Set Value = Nothing`).
+3. The same lines in VB6 6.0 and in 64-bit VBA each stop the compile with *Compile error: Invalid use of object*.
+
+The module is meant to be adapted as a regression test, as compile cases.
+```vb
+Module NothingLetTests
+
+    Private Sub Uses()
+        Dim Count As Long, Text As String, Flag As Boolean, Items As Collection, Value As Variant, Obj As Object
+        Count = Nothing  ' CASE LetLong_Nothing: error
+        Text = Nothing  ' CASE LetString_Nothing: error
+        Flag = Nothing  ' CASE LetBoolean_Nothing: error
+        If Obj = Nothing Then Count = 1  ' CASE EqualsComparison_Nothing: error
+        Flag = (Count <> Nothing)  ' CASE NotEqualsComparison_Nothing: error
+        Set Items = Nothing  ' CASE Control_SetObject: none
+        If Items Is Nothing Then Count = 1  ' CASE Control_IsNothing: none
+        Set Value = Nothing  ' CASE Control_SetVariant: none
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+A compile error on each of the five lines, as VB6 and 64-bit VBA give (*Invalid use of object*); no change to the three controls.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low: the code is wrong in every runtime, and twinBASIC does report it, but only when the line runs, as error 91.
+
+A 64-bit build gives the same results. VBA was 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access.
+
+What does not reproduce it: a Let of `Nothing` to a variable declared `As Object` (`Obj = Nothing`), which VB6 and VBA compile too and which raises 91 in all three, and to a `Variant`, which VB6 and VBA also compile (the queued entry `nothing-let-variant-no-error` is about what twinBASIC does with it). `Items = Nothing` for a `Collection` is refused by twinBASIC as well, with TB5092, *Missing argument 'Index'*, from the collection's default member.
+
+<!-- Reproducer: bugs/nothing-let-compiles/ (mode test: `tbrun --tests`, compile cases; expect lists the three PASS and five FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`. No VB6 side: VB6 refuses the project at compile, checked with scripts/vb6run.mjs on each line; 64-bit VBA checked with VbaSession, one module per line. Stated in a NOTE (BETA 1010) under Nothing on docs/Reference/Literal-Keywords.md; when fixed, the NOTE goes. Found 2026-10-29 writing that page; owner, 2026-10-29: a bug. -->
+
+---
+
+## A `Variant` assigned `Nothing` without `Set` holds `Nothing`, where VB6 and VBA raise 91 and leave it `Empty`
+
+**Describe the bug**
+`Value = Nothing`, with `Value` a `Variant` and no `Set`, makes `Value` hold `Nothing`, as `Set Value = Nothing` does, and raises no error. VB6 and 64-bit VBA read it as a Let of the default value of an object that is not there: they raise 91, *Object variable or With block variable not set*, and leave the `Variant` `Empty`. Code that leaves out `Set` by mistake therefore runs on in twinBASIC, where in VB6 and VBA it stops.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Open `nothing-let-variant-no-error.twinproj` (attached as `nothing-let-variant-no-error.zip`).
+2. Run its test cases, the module below. On BETA 1010 the two controls pass and the two other cases fail: `Err.Number` is 0, and the `Variant` holds `Nothing`.
+3. Build and run the VB6 project (attached as `nothing-let-variant-no-error-vb6.zip`), which runs the same statements. It prints:
+   ```
+   LetVariant: error 91, Value Empty
+   Control_SetVariant: Value Is Nothing True
+   Control_LetObject: error 91
+   ```
+
+The module is meant to be adapted as a regression test. Each case asserts what VB6 and 64-bit VBA do.
+```vb
+' Regression tests: assigning Nothing to a Variant without Set raises 91, Object variable or With
+' block variable not set, and leaves the Variant Empty, as VB6 does: it reads the assignment as
+' a Let of the default value of an object that is not there. On BETA 1010 the Variant holds
+' Nothing and no error is raised. The controls: Set stores Nothing, and a Let of Nothing to an
+' Object variable raises 91 in both.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub LetVariant_Raises91()
+        Dim Value As Variant
+        Value = 3
+        On Error Resume Next
+        Value = Nothing
+        Assert.Strict.AreEqual 91, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub LetVariant_LeavesItEmpty()
+        Dim Value As Variant
+        Value = 3
+        On Error Resume Next
+        Value = Nothing
+        On Error GoTo 0
+        Assert.Strict.IsTrue IsEmpty(Value)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetVariant_HoldsNothing()
+        Dim Value As Variant
+        Value = 3
+        Set Value = Nothing
+        Assert.Strict.IsTrue Value Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub Control_LetObject_Raises91()
+        Dim Obj As Object
+        On Error Resume Next
+        Obj = Nothing
+        Assert.Strict.AreEqual 91, Err.Number
+    End Sub
+
+End Module
+```
+
+**Expected behavior**
+Error 91, with the `Variant` left `Empty`, as VB6 and 64-bit VBA do.
+
+**Desktop:**
+ - OS: Windows 10 Pro 22H2 (build 19045)
+ - twinBASIC compiler version: BETA 1010
+
+**Additional context**
+Severity: low: the missing `Set` goes unreported, and the `Variant` holds what `Set` would have stored.
+
+A 64-bit build gives the same results. 64-bit VBA, 7.1 (VBE7.DLL 7.01.1158) in 64-bit Microsoft 365 Access, gives what VB6 gives.
+
+What does not reproduce it: `Set Value = Nothing`, which holds `Nothing` in all three, and a Let of `Nothing` to an `Object` variable, which raises 91 in all three.
+
+Related: the queued entry `nothing-let-compiles`, on the forms VB6 and VBA refuse when they compile.
+
+<!-- Reproducer: bugs/nothing-let-variant-no-error/ (mode test: `tbrun --tests`; expect lists the two PASS and two FAIL lines); run on BETA 1010, 32-bit and 64-bit, with `bug_repro.mjs run`. VB6 side in vb6/ (VB6 6.0); 64-bit VBA checked with VbaSession. Stated in a WARNING (BETA 1010) under Nothing on docs/Reference/Literal-Keywords.md; when fixed, the WARNING goes. Found 2026-10-29 writing that page; owner, 2026-10-29: a bug. -->
+
diff --git a/WIP.Authoring.md b/WIP.Authoring.md
index 26636360e..aa5bd8051 100644
--- a/WIP.Authoring.md
+++ b/WIP.Authoring.md
@@ -127,7 +127,17 @@ both. A page whose title cannot name its subject says so with `symbols:`, which
 those names. Two pages need it: the (Default) module (`[_HiddenModule]`) and the comparison
 operators (`["=", "<>", "<", "<=", ">", ">="]`, quoted, since a bare `>` is YAML). On a
 Core statement page the first name is the statement and the rest its keywords; on an
-operator page each is an operator.
+operator page each is an operator. **Quote `True`, `False` and `Null` too**: YAML reads them
+bare as a boolean and as null, and `symbolPages` fails the build on any entry that is not a
+string, rather than index it as `true`.
+
+Two summary pages outside `/tB/` are read as well (`SUMMARY_PAGES` in
+[builder/symbols.mjs](builder/symbols.mjs)): each name of their `symbols:` is at the `##`
+heading of that name, a `type` on `Reference/Data-Types.md` and a `keyword` on
+`Reference/Literal-Keywords.md` (owner, 2026-10-29: one page for **Nothing**, **Null**,
+**Empty**, **True** and **False**, a section each). `keyword` rather than `constant`, because
+the search ranks a keyword with no package first and a constant not; it is also VBA's word
+for them. A name with no such heading fails the build.
 
 The build names any page in a package folder that gives the index no entry, after its
 summary line. That is the cue for a third. **Do not add `symbols:` to change how a page
diff --git a/WIP.Build.md b/WIP.Build.md
index cfa27f50e..6b9830693 100644
--- a/WIP.Build.md
+++ b/WIP.Build.md
@@ -190,7 +190,7 @@ opens in the IDE and builds (`bundle_extra`, `docs/_config.yml`). It is laid out
 for byte; nothing checks that they agree, so a change to `src/` is packed again by hand
 (`node scripts/impexp.mjs import scripts/impexp/impexp.twinproj scripts/impexp/src
 --overwrite`). It has the same command line, output, exit codes and `--self-test` (the same
-20 tests) as `impexp.mjs` and `impexp.py`, and writes byte-identical project files. Its tests
+21 tests) as `impexp.mjs` and `impexp.py`, and writes byte-identical project files. Its tests
 are that `--self-test` and the commands of `check_impexp_parity.mjs`, which compares it
 when `IMPEXP_EXE` names its built exe, because no gate can build it; CI never sets the
 variable. The check runs the exe through `launchOnDesktop` with `cwd` (`TBBUILD_CWD` in
diff --git a/WIP.Errors.md b/WIP.Errors.md
index 30fd8e945..aba6e02dd 100644
--- a/WIP.Errors.md
+++ b/WIP.Errors.md
@@ -70,7 +70,38 @@ harnesses (`dialog`, `keys`, `window`): 164 cases, all agreeing in all four runt
 Shell; DoEvents quiet; Beep nothing (D3). `argument-errors-unspecified-error` extended, three
 entries queued (*Batch 6b findings*). No row is `bug: pending`, and no question is open.
 
-**Next: batch 7**, VBA `FileSystem`.
+**Batch 7 is done** (2026-10-27), VBA `FileSystem`, under a new harness (`files`): 448 cases in
+`errors/VBA.FileSystem.yml`, all agreeing in all four runtimes; sections on 21 of the module's 22
+pages (Reset raises nothing; the index documents nothing). The owner's rulings applied (six
+extensions, three bugs); `file-errors-unspecified` extended by 30 cases, three entries queued
+(*Batch 7 findings*). No row is `bug: pending`, and no question is open.
+
+**Batch 8 is done** (2026-10-28), VBA `Collection` and `ErrObject`: 259 cases in
+`errors/VBA.Collection.yml` and `errors/VBA.ErrObject.yml`, all agreeing in all four runtimes;
+sections on 10 of the 20 member pages (Count, both Clears, Items, Keys, LastDllError and
+LastHresult raise nothing; HelpFile, HelpContext and ReturnHResult cannot be probed, their
+assignment failing twinBASIC's build; the indexes document nothing). The owner's rulings
+applied (two extensions, one bug); three entries queued (*Batch 8 findings*). No row is `bug:
+pending`, and no question is open.
+
+**Batch 9 is done** (2026-10-28), VBA `Financial`: 349 cases in `errors/VBA.Financial.yml`,
+all agreeing in all four runtimes; sections on all 13 member pages (the index documents
+nothing); `-2147418113` (`E_UNEXPECTED`) added to `messages.yml` and measured. The owner's
+rulings applied: five entries queued, `argument-errors-unspecified-error` extended, and PV's 11
+for an infinite result an extension (*Batch 9 findings*). No row is `bug: pending`, and no
+question is open.
+
+**Batch 10 is done** (2026-10-28), VBA `HiddenModule`,
+`Compilation` and `TbExpressionService`: 280 cases in `errors/VBA.HiddenModule.yml`,
+`VBA.Compilation.yml` and `VBA.TbExpressionService.yml`, every one `only: tb` (VB6 and VBA have
+none of these procedures), all agreeing in both twinBASIC builds; sections on 35 pages; two new
+harnesses, `native` and `expression`; four HRESULTs added to `messages.yml` and measured. The
+owner's rulings applied: four entries queued (`nothing-argument-crashes`,
+`expression-service-dangling-tokens`, `expression-service-error-numbers`,
+`vbacastobj-no-type-mismatch`), and `CreateGUID`'s braceless form and `AllocMem(0)`'s error are
+the spec (*Batch 10 findings*). No question is open.
+
+**Next: batch 11**, Core file I/O statements.
 
 ## Owner's decisions
 
@@ -84,7 +115,10 @@ entries queued (*Batch 6b findings*). No row is `bug: pending`, and no question
   VB6, and twinBASIC 64-bit, compared with **64-bit VBA, whose behaviour must be respected**
   (owner): a difference between twinBASIC 64-bit and 64-bit VBA is a bug, exactly as one from
   VB6 is, with a NOTE and a queued reproducer. (Before: twinBASIC 64-bit for operators and
-  `Math` only, and no VBA.)
+  `Math` only, and no VBA.) **Where VB6 and 64-bit VBA differ, twinBASIC does as 64-bit VBA
+  does**, in both builds (owner, 2026-10-28): matching 64-bit VBA is an extension against VB6
+  (`only: [tb, vba64]` cases, a NOTE in the prose), and matching neither is a bug whose
+  reproducer asserts 64-bit VBA's number.
 - **Scope.** `docs/Reference/Default/` (VBA, VB, VBRUN), `docs/Reference/Core/` (statements and
   operators) and `docs/Reference/Built-In/`. Not `Contributed/`.
 - **Existing error prose moves into the tables.** A page that states an error in a sentence
@@ -177,19 +211,14 @@ What `errors.mjs messages` found (BETA 1010):
   these the two messages differ, and the file says `{ raised, error }`. The sections show
   `Err.Description` (owner: settled); showing `Error$(n)` instead would be a one-line change in
   `renderSection` (`.raised` to `.error`).
-- **Differences from VB6 that batch 8 (`ErrObject`) should take up**, none queued yet (batch 3
-  queued `Error$` above 65535, `error-function-above-65535`):
-  `Err.Raise n` of a number from 1 to 65535 without a message of its own leaves
-  `Err.Description` empty in twinBASIC below 747, and from 747 up gives the Windows system
-  message of that number (*Page fault was a transition fault.* for 747); VB6 gives
-  *Application-defined or object-defined error* (the central page says so in a NOTE).
-  VB6's `Err.Raise` of a common HRESULT raises its own number instead (`&H80070057` raises 5,
-  `&H80004001` 445, `&H80004002` 430, `&H80020003` 438, `&H80040154` 429, ...) and describes
-  the rest as *Automation error* with the HRESULT's text on a second line; twinBASIC keeps the
-  HRESULT and its text. `Err.Raise 65536` raises 5 in VB6, and `Error$(65536)` raises 6;
-  twinBASIC raises 65536 as *Automation error*, and `Error$(65536)` is generic. twinBASIC's
-  `Error$` of a few HRESULTs is VB's message (`Error$(&H80070057)` is *Invalid procedure call
-  or argument*), VB6's is generic.
+- **Differences from VB6 found here, and where each went** (batch 8 took them up):
+  `Err.Raise n` without a description, *Application-defined or object-defined error* in VB6 and
+  empty or a system message in twinBASIC, is filed (`err-raise-defaults`, #2504; the central
+  page's NOTE). VB's `Err.Raise` of a common HRESULT as its own number is queued
+  (`err-raise-hresult-mapping`). `Err.Raise 65536`, 5 in VB6, is an extension (owner,
+  2026-10-28; the Raise page's NOTE). `Error$` above 65535 is filed (`error-function-above-65535`). Left alone:
+  twinBASIC's `Error$` of a few HRESULTs is VB's message (`Error$(&H80070057)` is *Invalid
+  procedure call or argument*), VB6's is generic.
 
 ## Tooling
 
@@ -376,6 +405,31 @@ Windows refuses). `check_errors.mjs` reports a harness the data names and has no
   becomes the foreground one, and AppActivate raises nothing for that; in twinBASIC, activating a
   new window there takes 2 s from the third on (not on the user's desktop), so `errors.mjs`
   gives a twinBASIC probe 120 s.
+- **`files`** (batch 7) --- every procedure that names or opens a file. `files_Begin` makes
+  `files_Dir`, `tbdocsErrorsProbe` and the process id under the temporary folder, makes it the
+  current directory (Windows' own calls, so no statement under test sets it up) and fills it:
+  `a.txt` (`abc`, CR LF, `def`, CR LF: 10 bytes), `empty.txt`, `ro.txt` (read-only), `hid.txt`
+  (hidden), the empty folder `sub` and `full`, which holds `f.txt`. A case names its files
+  relatively. `files_End` closes every file, puts the current directory back and deletes the
+  folder whatever its files' attributes, keeping the case's error; it deletes nothing whose path
+  does not end in the folder's own name. `files_Begin` raises 1003 when it cannot make or enter
+  the folder, so a case never runs in another folder. `files_Attr(name)` is
+  `GetFileAttributesW` (-1: no such file), `files_Expect Cond` raises 1001, `files_NoDrive` is a
+  letter no drive has. **A probe line that starts `Reset:` is a label**, not the statement: put
+  `Reset` on a line of its own (`run: "Reset\n..."`). Check after a run that no
+  `tbdocsErrorsProbe*` folder is left in `%TEMP%`.
+- **`native`** (batch 10) --- **twinBASIC only**: every case that uses it is `only: tb`, so it uses
+  twinBASIC syntax. What the (Default) module's procedures take: `native_Icon` (the shared
+  `IDI_APPLICATION` icon), `native_Bitmap` (a 2 x 2 bitmap that `native_End` deletes unless
+  `native_Keep` says a picture owns it), `native_Window` (a hidden `STATIC` window, made by
+  `native_Begin`), `native_Handler` (a `GetMessageHookHelper.GetMessageHandler` that does
+  nothing), `native_StdIid(Data1)` (the address of the interface ID
+  `{Data1-0000-0000-C000-000000000046}`, for `vbaCastObj`) and the enumeration `native_Kind`
+  (-3 to 7).
+- **`expression`** (batch 10) --- twinBASIC only. In a built exe the first error the expression
+  service (`Eval`, `TbExpressionService`) raises in a process has the description *Automation
+  error*, every later one *Unspecified error*; `expression_Begin` raises the first once and
+  clears it, so a case's description does not depend on which case runs first (`--only`).
 
 **YAML pitfalls**, each met in batch 2:
 
@@ -443,6 +497,14 @@ What the probes must respect (BETA 1010; `errors.mjs` already does all of it):
   builds a failing project again without the case named in the error.
 - **A case that allocates near the string limit raises 14** (`String(1073741823, "a")` in
   32-bit): use it to show that the 5 above the limit is a check of its own, never as a row.
+- **A case that crashes stops the probe, and every later case reports `none`** (`the probe
+  stopped before it ended: exception 0xc0000005`), as a hang does. Explore one page per probe
+  (a data file holding only that page), then one case per probe for a page that stops; a case
+  that crashes is a WARNING by hand, never a case.
+- **The probe is one module**: a case cannot declare a class, an interface or a `Type`. A
+  harness can hold a `Type`, an `Enum`, a `Declare` and procedures; a fact that needs a class
+  (`GetNameFromDispID` on a twinBASIC class) is checked with `tbrun` on a tree of its own and
+  stated in the page's prose.
 
 ## Batch 2 findings (VBA `Strings`, BETA 1010)
 
@@ -864,6 +926,243 @@ twinBASIC's InputBox fault (a string it never set); a reproducer's VB6 project m
 InputBox when it carries the dialog harness (`reproAnswersBoxes`). The broker's startup race
 (four clients, all ENOENT) is fixed on both sides (WIP.Broker.md).
 
+## Batch 7 findings (VBA `FileSystem`, BETA 1010, 2026-10-27)
+
+twinBASIC 64-bit agrees with 32-bit on every case, and 64-bit VBA with VB6, so every difference
+is twinBASIC against both.
+
+- **-2147467259 where VB raises a number, almost everywhere** (`file-errors-unspecified`, queued
+  since BETA 1005 and extended by 30 cases): 5, 52, 53, 54, 62, 63, 67, 68, 75, 76. The page's old
+  hand NOTEs went; the rows' generated NOTEs replace them. The Core pages (Open, Name, Get, Put,
+  Print, Line Input) keep their hand NOTEs until batch 11. What VB raises for a bad name differs
+  by procedure: GetAttr 5 for `<` or a file name ending in a backslash, FileLen and FileDateTime
+  53 for those, Dir 52 for the backslash; a wildcard is 52 everywhere but ChDir, MkDir and RmDir
+  (76) and Kill (53 when nothing matches).
+- **Null raises 94 everywhere**, but `CurDir(Null)` and `Dir(Null)` raise 13 in VB
+  (`filesystem-argument-checks`).
+- **Owner's rulings (2026-10-27)**. Extensions, with a NOTE saying what VB does and
+  twinBASIC-only quiet cases: Dir's *attributes* outside 0 to 63 (unknown bits ignored; VB 5);
+  a non-String argument to Dir and CurDir, converted as ChDir and ChDrive convert theirs in VB
+  (`Dir(5)`; VB 13); FileCopy of a source open for reading only, not locked against reading
+  (VB 55 for any mode but Input); SetAttr's *attributes* wherever Windows accepts them ("tB
+  extension where the attributes are valid for the underlying WINAPI; where the WINAPI fails,
+  SetAttr must correctly raise an error"; VB 5 for anything but sums of 1, 2, 4, 32, and 16 on a
+  folder); Width from 256 to 32,767 (VB 5). Bugs (`filesystem-argument-checks`): a negative Width
+  (no error, a new line before each item), FileLen and FileDateTime of a wildcard that matches (the
+  first match's value; VB 52), and with them `Input(0)` (-2147467259; VB returns `""`) and the
+  Null 13.
+- **Kill deletes hidden and system files** (`kill-hidden-system-files`, a WARNING): VB raises 53
+  for one named alone and skips it in a wildcard.
+- **FileCopy's numbers** (`filecopy-error-numbers`): 70 for a folder or a read-only or hidden
+  destination (VB 75), 55 for a copy onto itself or of a source open `Lock Read` (VB 70).
+- **SetAttr of a file open for writing**: no error (VB 55), `setattr-open-file-no-error`, queued
+  since BETA 1005; its WARNING stays beside the generated NOTE.
+- **Agree in all four**: FileCopy's 53, 55 and 76; Binary-mode `Input` past the end returns
+  what is left, with no error; `InputB(0)` returns `""`; `FreeFile` takes any *rangenumber*
+  (nonzero after rounding is 256 to 511), and with 256 to 511 all in use `FreeFile(1)` returns
+  512, which `Open` accepts; Reset closes files 256 to 511 too; Width does not wrap inside one
+  item; Kill stops at an open file a wildcard matches, after the files before it.
+- **Page edits**: the error sentences of Dir, FileCopy, Kill, RmDir and Seek went into the
+  tables; Width's parameter is an **Integer** from 0 to 32,767 (32,768 is the conversion's 6);
+  CurDir's section moved below both functions, and ChDrive's, Dir's, MkDir's and RmDir's above
+  their See Also, which those pages put before the Example (`spliceSection` places a new
+  section before the first Example, so a page with See Also first needs moving by hand once).
+
+## Batch 8 findings (VBA `Collection` and `ErrObject`, BETA 1010, 2026-10-27)
+
+twinBASIC 64-bit agrees with 32-bit on every case, and 64-bit VBA with VB6.
+
+- **Assigning `Err.HelpFile`, `Err.HelpContext`, or `Err.ReturnHResult` in a module procedure,
+  compiles and fails the build** with a codegen error (`err-helpfile-helpcontext-codegen`); in
+  test mode the procedure aborts. So the data has no case for those three pages (a case would
+  fail the whole probe): each page has a hand NOTE, and Raise's *helpfile* and *helpcontext*
+  are covered on the Raise page. When it is fixed, add `Err.HelpFile = Null` and
+  `Err.HelpContext = Null` (94 in VB6 and VBA) as rows. ReturnHResult's example now sits in a
+  class (its build failed as a module function; `examples.bat --build` is clean).
+- **VB turns HRESULTs into VB numbers; twinBASIC does not** (`err-raise-hresult-mapping`):
+  `Err.Raise` of 22 HRESULTs tried raises a VB number in VB6 and 64-bit VBA (`E_INVALIDARG`
+  5, `E_NOTIMPL` 445, the `DISP_E_` ones, `&H800A0000 + n` as *n*, ...), and `Err.Number =` of
+  one stores the VB number without raising. Data rows cannot hold one `vb6:` per HRESULT, so
+  the Raise page has a hand NOTE with the table, and twinBASIC's side is `only: tb` quiet cases
+  (wrapped, below). `Err.Raise &H800A0000` raises nothing at all in VB6 and VBA; not written.
+- **How a case says "raised what it was asked"**: `Err.Raise n` (and `Err.Number = n`) then
+  `If Err.Number = n Then Err.Clear`, so the case reports 0, and a runtime that raises or keeps
+  another number reports that. `Err.Number = 65536` raises 5 in VB (an `On Error GoTo` handler
+  is entered); `Err.Number = &H80070057` only stores 5.
+- **Collection** (`collection-index-checks`): a `Currency`, `Decimal` or `Date` index is
+  refused (Item and Remove 9, Add's position 13; VB takes it as a number); Item of a number on
+  an empty collection 9 (VB 5; Remove is 5 in both); Item and Remove of `Null`, an object, an
+  array, an error value or a number beyond `Long` 9 (VB 13); Add's position of -1, `True` or
+  `Empty` 13 (VB 9). Agree in all four: duplicate key 457 (`""` is a key); a non-String key 13
+  (a number too: VB does not convert it); both positions 5; a position on an empty collection
+  5, `Null` there too; a string position or index that is no key 5.
+- **Owner's rulings (2026-10-28)**. Extensions, each with a NOTE in the page's prose and
+  `only: tb` quiet cases: `Err.Raise` and `Err.Number =` of a number above 65535 (twinBASIC
+  raises or sets it; VB raises 5), and `Collection.Add` with *before* one more than **Count**
+  (adds at the end) or *after* 0 (adds at the start; VB raises 9 for both). A bug, in
+  `collection-index-checks`: `Collection.Add` with a *key* of **Empty** adds the item without a
+  key (VB 13).
+- **Page edits**: the error sentences of Add, Item, Remove and KeyCompareMode went into the
+  tables; the central page has a NOTE on `Err.Raise` of an HRESULT.
+
+## Batch 9 findings (VBA `Financial`, BETA 1010, 2026-10-28)
+
+twinBASIC 64-bit agrees with 32-bit on every case. Unlike the earlier batches, **VB6 and 64-bit
+VBA differ** where a result is infinite: VB6 returns infinity from SLN and PV, 64-bit VBA raises
+6 or 11 (the rows carry `vba64:`). The values behind the defects below were read with a value
+probe (twinBASIC through `tbrun`, VB6 through `vb6run`), not only the error numbers.
+
+- **Every parameter is a Double** in twinBASIC's declarations and in VBA's; FV, PV, Pmt and
+  PPmt said **Integer** for *nper* (and PPmt for *per*), from VBA-Docs. Fixed on the pages.
+- **The -2147467259 family** (`argument-errors-unspecified-error`): every argument check where
+  VB raises 5 (and Rate's 6), in DDB, SLN, SYD, IPmt, PPmt, Pmt, NPer, Rate and IRR.
+- **Rate fails for almost every annuity**: -2147467259 for every case tried with *pmt* other
+  than 0, and for `Rate(10, 0, 1000, -2000)`; it answers `Rate(1, 0, 100, -110)` and
+  `Rate(2, 0, 100, -121)`. It also raises 5 for an *nper* below 1 with *pmt* 0 (VB answers), and
+  never checks *guess*: **Null**, `"abc"` and an error value pass (VB 94, 13, 13).
+- **NPer raises 6 when *rate* and *pmt* have opposite signs**, which is every loan and savings
+  plan at a positive rate (`NPer(0.01, -100, 1000)` is 10.59 in VB6); where it answers, the value
+  is right. Where no number of periods exists it raises 6 or 11, VB 5.
+- **Null in an optional Variant argument raises 13**, VB 94: *pv*/*fv* and *type* of FV, PV, Pmt,
+  NPer, IPmt, PPmt and Rate, and DDB's *factor*.
+- **Arrays**: IRR, MIRR and NPV of an array never sized **crash** (access violation, 32-bit and
+  64-bit, IDE and exe; VB 5), a hand WARNING on each page and no case; a 2-D array raises
+  -2147418113, *Catastrophic failure* (VB 5).
+- **Missing checks that return a value** (hand WARNINGs beside the generated NOTEs): IPmt and
+  PPmt take any *per* (VB 5 when *per* is 0 or less, or *nper* + 1 or more); MIRR returns -1 for
+  one element, a rate for a *finance_rate* or *reinvest_rate* of -1 (VB 5), and infinity or NaN
+  for *values* with no negative element (VB 11); NPV returns NaN for a *rate* of -1 (VB 5).
+- **Other differences**: DDB refuses a *life* between 0 and 1 (VB answers); Pmt and PPmt raise 11
+  for an *nper* of 0 (VB 5); FV raises 5 for *rate* -1 and a negative *nper* (VB6 11, 64-bit VBA
+  6); PV raises -2147467259 for a *rate* of -1 (VB6 returns infinity or 0; 64-bit VBA 11, 6, or 0
+  for *nper* 0).
+- **Infinite results**: PV raises 11 (as 64-bit VBA does; VB6 returns infinity), SLN returns
+  infinity (as VB6 does; 64-bit VBA raises 6). FV raises 6 in all four.
+- **Agree in all four**: **Null** in a required argument 94; a string that is not a number in an
+  optional argument 13; Pmt's 6 and 11 for a *rate* of -1 or -2; IRR's guess 94 and 13; FV's 6;
+  any *type* is taken (only 0 means the end of the period).
+- **Page edits**: SLN's, SYD's and DDB's "All arguments must be positive numbers" and NPV's (and
+  MIRR's half of) "must contain at least one negative value and one positive value" are
+  `<!-- VBA: -->` comments (all four take what they forbid); IRR's and Rate's "If ... can't find a
+  result after 20 tries, it fails" is reworded, the table carrying the error; the module index no
+  longer says MIRR takes a *guess* or that every array needs both signs.
+
+- **Rate's wrong root** (found writing its reproducer): for a lump sum (*pmt* 0) over an even
+  number of periods it returns -2.1 where VB6 returns 0.1 (`Rate(2, 0, 100, -121)`,
+  `Rate(4, 0, 100, -146.41)`; one and three periods are right). Silent, so a WARNING by hand on
+  Rate, in `rate-fails`. Not in the data: a value, not an error.
+
+**Owner's rulings (2026-10-28)**:
+
+1. **The five entries accepted**, as proposed, and queued with `tests` reproducers and VB6
+   sides: `rate-fails` (3 PASS, 12 FAIL), `nper-opposite-signs-overflow` (3, 9),
+   `financial-null-optional-argument` (3, 9), `financial-array-arguments` (3 PASS, 4
+   ACCESS_VIOLATION, 3 FAIL), `financial-argument-checks` (3, 16). `argument-errors-unspecified-error`
+   extended by one case per function (DDB, SLN, SYD, IPmt, PPmt, Pmt, NPer, Rate twice, IRR: 3
+   PASS, 35 FAIL now).
+2. **Where VB6 and 64-bit VBA differ, twinBASIC does as 64-bit VBA does.** So PV's 11 for an
+   infinite result is an extension against VB6 (cases `only: [tb, vba64]`, a NOTE in PV's
+   prose), and SLN's infinity is a bug (`financial-argument-checks`, asserting 6).
+3. **A *rate* of -1 in FV and PV, by the same rule**: FV is to raise 6, and PV 0, 11 or 6 by
+   the sign of *nper*, as 64-bit VBA; in `financial-argument-checks`, whose cases assert 64-bit
+   VBA's numbers (its VB6 side prints VB6's, which differ in those four cases).
+
+A reproducer's case asserts 64-bit VBA's number where the two VB runtimes differ; say so in the
+entry, since the VB6 project then disagrees with the module.
+
+## Batch 10 findings (VBA `HiddenModule`, `Compilation`, `TbExpressionService`, BETA 1010, 2026-10-28)
+
+Every procedure is twinBASIC's own, so every case is `only: tb` and no row has a `vb6:`: a
+defect here is one against the page or against what the procedure is for, not against VB.
+twinBASIC 64-bit agrees with 32-bit on every case but `AllocMem(2000000000)` (a `win64: 0`
+row). The pages with no section raise nothing of their own: `Compilation`'s eight (compile-time
+intrinsics), `CreateGUID`, the `GetDeclared...` six, `StackArgsSize`, `StackOffset`,
+`InterlockedIncrement32`/`Decrement32`, `Start`, `Stop`, `RuntimeCreateGetMessageHook`,
+`UnprotectedAccess`, `vbaAryMove`, `vbaRefVarAry`, `AddStdLibraryBinder`; and `Emit`, `EmitAny`,
+`InternalGetReturnAddress` (fails a 64-bit build), `AddCustomBinder` and `Bind` have no case.
+
+- **Null raises 94** for every numeric or string argument, **424** for an object one
+  (`AddClassInstanceFlag`, `ConvertIconToBitmap`, `GetInheritedOwner`, `GetNameFromDispID`,
+  `PictureToByteArray`, `vbaCastObj`).
+- **Raw HRESULTs** where the procedure fails: `AllocMem` of 0 or less -2147024882
+  (`E_OUTOFMEMORY`, as for a block too big); `CreateStdPictureFromHandle` -2147467259 for a
+  handle of the wrong kind and -2147418113 for a *Type* outside 0 to 4 (a bitmap handle is never
+  checked); `ConvertIconToBitmap` -2147467259 for anything but an icon, 5 and 13 for its
+  *BackColor* as `TranslateColor`; `PictureToByteArray` -2147467262 for a non-picture;
+  `GetNameFromDispID`'s four (the page's hand table, now data), and `ShowPropertyPageEditor`'s
+  -2147467261 and -2147467262. On an object of a twinBASIC class `GetNameFromDispID` raises 5
+  (-4: -2147319765), checked with `tbrun` on a tree with a class: a sentence on the page.
+- **The expression service** (`Eval`, `Compile`, `Evaluate`): every failure is -2147467259, a
+  name it cannot resolve and a syntax error alike, and so is **any error inside the expression**
+  (11, 13, 5, a bound object's 457): its number is lost (NOTEs on Eval and Evaluate).
+  `Eval("CVErr(5)")` and `Eval("Len(Null)")` raise it too, though `Len(Null)` is **Null**
+  outside an expression. **Some malformed expressions are accepted silently**: `"2 +"`,
+  `"2 Mod"`, `"(2"`, `"2)"` give 2 (WARNINGs on Eval and Compile; quiet cases). The first error of
+  a process says *Automation error*, later ones *Unspecified error*; in the IDE, always
+  *Automation error* (NOTEs; the `expression` harness).
+- **Crashes** (access violation, 32-bit and 64-bit; a WARNING by hand on each page, no case):
+  `ConvertIconToBitmap(Nothing)`; `GetInheritedOwner` of **Nothing** or of an object that is not
+  a control (a `Collection` in both builds, a `Scripting.Dictionary` in 64-bit);
+  `AddCustomBinder Nothing`; `AddCustomBinderObject name, Nothing`; and `V =
+  RuntimeCreateGetMessageHook()` into a Variant without `Set` (`Set V =` is fine, and a Let of
+  another non-dispatch object, a twinBASIC class behind an `IUnknown` interface, stores it with
+  no error, so the fault is the hook object's). Also, with no WARNING (misuse of an internal or
+  of a raw address): `AddClassInstanceFlag` of -1, an address of 0 to `GetMem*`, `PutMem*` and
+  `vbaCopyBytes` (`FreeMem 0` and `vbaObjAddref 0` are quiet), and `vbaCastObj` given a number or
+  (32-bit) **Null** as *IID*.
+- **Pages corrected from what twinBASIC does**: `CreateGUID` returns 36 characters without
+  braces (the page said `{...}`; the index pages too); `vbaCastObj` reads *IID* as the address of a
+  GUID, so a String gives **Nothing** silently (the page said it took a String; its example and
+  `GetDeclaredTypeIid`'s now use `VarPtr` of a GUID and print the IID); `PictureToByteArray(Nothing)`
+  is a `Byte` array with no bounds; `FreeMem 0` does nothing; `Compile` without a binder takes
+  `"1 + 1"`; `AllocMem`'s and `Compile`'s error sentences went into the tables. Added:
+  `RegisterMessage` checks no argument, `InterlockedIncrement32`/`Decrement32` wrap with no error.
+- **Out of this batch**: `Set X = obj` where *X* is declared as an interface *obj* does not
+  have raises -2147467262 (`E_NOINTERFACE`); VB6 raises 13. Not checked in VB6 here, not queued:
+  for a Core batch.
+
+**Owner's rulings (2026-10-28)**, and what was done:
+
+1. **The crashes: one entry**, GetInheritedOwner of a non-control in it: queued as
+   `nothing-argument-crashes` (3 PASS, 7 FAIL with ACCESS_VIOLATION; the `Scripting.Dictionary`
+   case passes in 32-bit), the five WARNINGs tagged.
+2. **Malformed expressions: an entry**, `expression-service-dangling-tokens` (3 PASS, 8 FAIL), the
+   two WARNINGs and the quiet cases' comments tagged.
+3. **The lost error number: "investigate what is most appropriate from a tB user's perspective,
+   and proceed accordingly"**. Both VB-family evaluators keep the error: VBScript's `Eval`
+   (`MSScriptControl.ScriptControl` from VB6) raises 11, 13 (*Type mismatch: 'CInt'*), 6, 5 and
+   450 for `1 / 0`, `CInt("abc")`, `CInt(40000)`, `Sqr(-1)`, `Sqr(1, 2)`, and 1002 *Syntax error*
+   or 1006 *Expected ')'* for every malformed expression; Access's `Eval` (64-bit VBA, VbaSession)
+   raises 11, 13, 6, 5, returns **Null** for `Len(Null)`, and raises 2431, 2434, 2435, 2436, 2439
+   for syntax errors and argument counts. So a bug: queued as `expression-service-error-numbers`.
+   **Owner, then: "Eval should not be special casing errors"** unless VB does, which it does
+   not, and **the entry asks only for errors to be passed through unchanged** (2 PASS, 7 FAIL:
+   11, 13, 6, 5 and a bound object's 457, and the description *Division by zero*). Left out of it,
+   and in no entry: a compile failure's number and description (no direct code to compare:
+   `Sqr(1, 2)` does not compile), `Eval("Len(Null)")` and `Eval("CVErr(5)")` (Eval fails where
+   direct code returns a value), and the unstable description (the description NOTEs, untagged,
+   and the `expression` harness). **Owner: they stay NOTEs, with no entry** (untagged, so no
+   retired entry removes them: check them against each new BETA, as every labelled callout is).
+   The Evaluate page's prose states the propagation, the tagged NOTEs say what BETA 1010 does.
+4. **"What does VBx do?" for `vbaCastObj`**: VB6's own `__vbaCastObj` (msvbvm60, called through a
+   `Declare`) returns the interface for a GUID's address, 0 for **Nothing**, and raises **13,
+   Type mismatch** for an interface the object lacks, a String's text read as an IID included;
+   twinBASIC returns **Nothing** for both. VBE7.DLL exports no `__vba` procedure, so 64-bit VBA
+   cannot be asked. **Owner: a bug.** Queued as `vbacastobj-no-type-mismatch` (3 PASS, 2 FAIL;
+   VB6 side calling `__vbaCastObj`); the data's row is `error: 0`, `vb6: 13` (its cases `only:
+   tb`, so the NOTE names VB6 alone); the page states the 13 and has a WARNING.
+5. **"What does VBx do?" for `CreateGUID`**: nothing to compare. VB6 and VBA have no CreateGUID,
+   nor does Access (`Application.CreateGUID` 438, `Eval("CreateGUID()")` 2425), and no runtime
+   exports one. VB code makes one with `CreateObject("Scriptlet.TypeLib").Guid`, which is braced
+   (`{...}`, and two trailing NULs: 40 characters), or `StringFromGUID2`, braced. twinBASIC's
+   `GetDeclaredTypeIid` and its kin return the braced form; `CreateGUID` the 36-character form the
+   `ClassId` and `InterfaceId` attributes take. **Owner: the existing behaviour is the spec**,
+   as the page now states it.
+6. **"What does VBx do?" for `AllocMem(0)`**: nothing to compare: no AllocMem in VB6, VBA, msvbvm60
+   or VBE7 (their GetMem/PutMem family has no allocator). Windows' allocators (`HeapAlloc`,
+   `CoTaskMemAlloc`, `GlobalAlloc`) return a block for 0 bytes. **Owner: the existing behaviour
+   is the spec**: the page's row of -2147024882 for 0 or less stands.
+
 ## The 64-bit VBA re-check (BETA 1010, Office 365 x64, VBA 7.1 VBE7.DLL 7.01.1158, 2026-10-22)
 
 Batches 2 to 5 and `Core.yml` in all four runtimes. Every runtime agreed with the data as it
@@ -945,10 +1244,10 @@ each can be run when there is budget. Status is kept here.
 | 5 | VBA `DateTime` | 20 | done: 17 sections, 328 cases; owner's questions answered 2026-10-22 |
 | 6a | VBA `Information`, and `Interaction`'s non-interactive procedures: `CallByName`, `CallByDispId`, `Choose`, `Command`, `CreateObject`, `GetObject`, `Environ`, `IIf`, `If`, `Partition`, `Switch`, `RaiseEventByName`, `RaiseEventByName2`, `SaveSetting`, `GetSetting`, `GetAllSettings`, `DeleteSetting` (owner split batch 6, 2026-10-22) | 45 | done: 27 sections, 302 cases; four entries queued 2026-10-22 |
 | 6b | `Interaction`'s interactive procedures: `AppActivate`, `Beep`, `DoEvents`, `InputBox`, `MsgBox`, `SendKeys`, `Shell`, under the `dialog`, `keys` and `window` harnesses (`Shell` only with programs that do not exist or `cmd.exe /c exit`) | 7 | done: 5 sections, 164 cases; three entries queued 2026-10-27 |
-| 7 | VBA `FileSystem` | 23 | not started |
-| 8 | VBA `Collection` and `ErrObject` (and the `Err.Raise` differences under *The central page*) | 22 | not started |
-| 9 | VBA `Financial` | 14 | not started |
-| 10 | VBA `HiddenModule`, then `Compilation` and `TbExpressionService` (`Constants` has nothing to raise) | 68 | not started |
+| 7 | VBA `FileSystem`, under the `files` harness | 23 | done: 21 sections, 448 cases; three entries queued, one extended, 2026-10-27 |
+| 8 | VBA `Collection` and `ErrObject` (and the `Err.Raise` differences under *The central page*) | 22 | done: 10 sections, 259 cases; three entries queued 2026-10-27; owner's rulings 2026-10-28 |
+| 9 | VBA `Financial` | 14 | done: 13 sections, 349 cases; five entries queued, one extended; owner's rulings 2026-10-28 |
+| 10 | VBA `HiddenModule`, then `Compilation` and `TbExpressionService` (`Constants` has nothing to raise) | 68 | 35 sections, 280 cases, harnesses `native` and `expression`; four entries queued; owner's rulings 2026-10-28 |
 | 11 | Core file I/O statements (`Open`, `Get`, `Put`, `Input`, ...: errors 52--75) | 15 | not started |
 | 12 | Core arrays and control flow (`ReDim`, `Erase`, `Resume`, `Return`, ...); ReDim has data already, in `errors/Core.yml` | 15 | not started |
 | 13 | Operators: the matrix generator and its pages | 25 | not started |
diff --git a/add-in/Resources/SYMBOLS/symbols.json b/add-in/Resources/SYMBOLS/symbols.json
index d8e114075..4c7f00bb7 100644
--- a/add-in/Resources/SYMBOLS/symbols.json
+++ b/add-in/Resources/SYMBOLS/symbols.json
@@ -18,6 +18,11 @@
     {"name":"Single","package":null,"container":null,"kind":"type","url":"/Reference/Data-Types#single"},
     {"name":"String","package":null,"container":null,"kind":"type","url":"/Reference/Data-Types#string"},
     {"name":"Variant","package":null,"container":null,"kind":"type","url":"/Reference/Data-Types#variant"},
+    {"name":"Empty","package":null,"container":null,"kind":"keyword","url":"/Reference/Literal-Keywords#empty"},
+    {"name":"False","package":null,"container":null,"kind":"keyword","url":"/Reference/Literal-Keywords#false"},
+    {"name":"Nothing","package":null,"container":null,"kind":"keyword","url":"/Reference/Literal-Keywords#nothing"},
+    {"name":"Null","package":null,"container":null,"kind":"keyword","url":"/Reference/Literal-Keywords#null"},
+    {"name":"True","package":null,"container":null,"kind":"keyword","url":"/Reference/Literal-Keywords#true"},
     {"name":"AddressOf","package":null,"container":null,"kind":"operator","url":"/tB/Core/AddressOf"},
     {"name":"Alias","package":null,"container":null,"kind":"statement","url":"/tB/Core/Alias"},
     {"name":"And","package":null,"container":null,"kind":"operator","url":"/tB/Core/And"},
diff --git a/bugs/argument-errors-unspecified-error/argument-errors-unspecified-error.twinproj b/bugs/argument-errors-unspecified-error/argument-errors-unspecified-error.twinproj
index aa20aba3f..19807f567 100644
Binary files a/bugs/argument-errors-unspecified-error/argument-errors-unspecified-error.twinproj and b/bugs/argument-errors-unspecified-error/argument-errors-unspecified-error.twinproj differ
diff --git a/bugs/argument-errors-unspecified-error/repro.json b/bugs/argument-errors-unspecified-error/repro.json
index 9617c6156..870a96a27 100644
--- a/bugs/argument-errors-unspecified-error/repro.json
+++ b/bugs/argument-errors-unspecified-error/repro.json
@@ -30,7 +30,17 @@
       "^FAIL RegressionTests.MsgBox_HelpFileWithoutContext_Raises5: .*Actual: -2147467259 ",
       "^FAIL RegressionTests.InputBox_HelpFileWithoutContext_Raises5: .*Actual: -2147467259 ",
       "^FAIL RegressionTests.SendKeys_UnknownKeyCode_Raises5: .*Actual: -2147352567 ",
-      "^FAIL RegressionTests.SendKeys_WaitNull_Raises94: .*Actual: -2147352567 "
+      "^FAIL RegressionTests.SendKeys_WaitNull_Raises94: .*Actual: -2147352567 ",
+      "^FAIL RegressionTests.DDB_LifeZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.SLN_LifeZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.SYD_PeriodAboveLife_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.IPmt_NperZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.PPmt_NperNegative_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Pmt_RateAndNperZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.NPer_RateAndPmtZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Rate_NperZero_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Rate_NperBelowOneOverflow_Raises6: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.IRR_NoReceipt_Raises5: .*Actual: -2147467259 "
     ]
   }
 }
diff --git a/bugs/argument-errors-unspecified-error/src/Sources/RegressionTests.twin b/bugs/argument-errors-unspecified-error/src/Sources/RegressionTests.twin
index e266f8e40..6f5bd9d38 100644
--- a/bugs/argument-errors-unspecified-error/src/Sources/RegressionTests.twin
+++ b/bugs/argument-errors-unspecified-error/src/Sources/RegressionTests.twin
@@ -236,4 +236,86 @@ Module RegressionTests
         Assert.Strict.AreEqual 94&, Err.Number
     End Sub
 
+    ' The Financial functions (batch 9).
+    [TestCase]
+    Public Sub DDB_LifeZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = DDB(1000, 100, 0, 1)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub SLN_LifeZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = SLN(1000, 100, 0)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub SYD_PeriodAboveLife_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = SYD(1000, 100, 5, 6)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_NperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = IPmt(0.01, 1, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_NperNegative_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = PPmt(0.01, 1, -10, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_RateAndNperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = Pmt(0, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub NPer_RateAndPmtZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = NPer(0, 0, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_NperZero_Raises5()
+        Dim R As Double
+        On Error Resume Next
+        R = Rate(0, -100, 1000)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_NperBelowOneOverflow_Raises6()
+        Dim R As Double
+        On Error Resume Next
+        R = Rate(0.5, -100, 1000)
+        Assert.Strict.AreEqual 6&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_NoReceipt_Raises5()
+        Dim R As Double, F(1) As Double
+        F(0) = -100: F(1) = -110
+        On Error Resume Next
+        R = IRR(F)
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
 End Module
diff --git a/bugs/argument-errors-unspecified-error/vb6/Module1.bas b/bugs/argument-errors-unspecified-error/vb6/Module1.bas
index c488ae46e..7c035b03b 100644
--- a/bugs/argument-errors-unspecified-error/vb6/Module1.bas
+++ b/bugs/argument-errors-unspecified-error/vb6/Module1.bas
@@ -379,5 +379,17 @@ Sub Main()
     dialog_End
     SendKeys "{BAD}": Report "SendKeys_UnknownKeyCode"
     SendKeys "", Null: Report "SendKeys_WaitNull"
+    Dim R As Double, F(1) As Double
+    R = DDB(1000, 100, 0, 1): Report "DDB_LifeZero"
+    R = SLN(1000, 100, 0): Report "SLN_LifeZero"
+    R = SYD(1000, 100, 5, 6): Report "SYD_PeriodAboveLife"
+    R = IPmt(0.01, 1, 0, 1000): Report "IPmt_NperZero"
+    R = PPmt(0.01, 1, -10, 1000): Report "PPmt_NperNegative"
+    R = Pmt(0, 0, 1000): Report "Pmt_RateAndNperZero"
+    R = NPer(0, 0, 1000): Report "NPer_RateAndPmtZero"
+    R = Rate(0, -100, 1000): Report "Rate_NperZero"
+    R = Rate(0.5, -100, 1000): Report "Rate_NperBelowOneOverflow"
+    F(0) = -100: F(1) = -110
+    R = IRR(F): Report "IRR_NoReceipt"
     Close #9
 End Sub
diff --git a/bugs/collection-index-checks/collection-index-checks.twinproj b/bugs/collection-index-checks/collection-index-checks.twinproj
new file mode 100644
index 000000000..683245a79
Binary files /dev/null and b/bugs/collection-index-checks/collection-index-checks.twinproj differ
diff --git a/bugs/collection-index-checks/repro.json b/bugs/collection-index-checks/repro.json
new file mode 100644
index 000000000..997ca6d2b
--- /dev/null
+++ b/bugs/collection-index-checks/repro.json
@@ -0,0 +1,25 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_ItemOfLongDoubleByte$",
+      "^PASS RegressionTests\\.Control_ItemOutOfRange_Raises9$",
+      "^PASS RegressionTests\\.Control_ItemOfMissingKey_Raises5$",
+      "^FAIL RegressionTests\\.Item_Currency_ReturnsItem: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Item_Decimal_ReturnsItem: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Item_Date_ReturnsItem: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Remove_Currency_Removes: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.AddBefore_Currency_Adds: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.Item_EmptyCollection_Raises5: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Item_Null_Raises13: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Item_Object_Raises13: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Item_BeyondLong_Raises13: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Remove_Null_Raises13: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.AddBefore_MinusOne_Raises9: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.AddBefore_Empty_Raises9: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.AddBefore_BeyondLong_Raises13: .*Actual: 9 ",
+      "^FAIL RegressionTests\\.Add_EmptyKey_Raises13: .*Actual: 0 "
+    ]
+  }
+}
diff --git a/bugs/collection-index-checks/src/Settings b/bugs/collection-index-checks/src/Settings
new file mode 100644
index 000000000..e887e7c49
--- /dev/null
+++ b/bugs/collection-index-checks/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "CollectionIndexChecks",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Collection's Item, Remove and Add check an index or a position differently from VB",
+	"project.exportPathIsV2": true,
+	"project.id": "{4A7DA874-1C47-458C-A7CB-31B020EF778B}",
+	"project.name": "CollectionIndexChecks",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/collection-index-checks/src/Sources/RegressionTests.twin b/bugs/collection-index-checks/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..08e5b44f8
--- /dev/null
+++ b/bugs/collection-index-checks/src/Sources/RegressionTests.twin
@@ -0,0 +1,128 @@
+' Regression tests: Collection's Item, Remove and Add take an index or a position as VB6 and
+' 64-bit VBA do: a Currency, Decimal or Date number like any other number; 5 for a number on
+' an empty collection (Item); 13 for Null, an object or a number outside the Long range
+' (Item, Remove); 9 for a position of -1, True or Empty, and 13 for a key of Empty (Add). The controls use a Long, a
+' Double and a Byte, and a string key. tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    ' A collection holding "a" and "b", without keys.
+    Private Function Two() As Collection
+        Set Two = New Collection
+        Two.Add "a"
+        Two.Add "b"
+    End Function
+
+    ' The error Item(Index) raises on C, or 0 and the item in Got.
+    Private Function ItemError(ByVal C As Collection, ByVal Index As Variant, Optional ByRef Got As Variant) As Long
+        On Error Resume Next
+        Got = C.Item(Index)
+        ItemError = Err.Number
+    End Function
+
+    Private Function RemoveError(ByVal C As Collection, ByVal Index As Variant) As Long
+        On Error Resume Next
+        C.Remove Index
+        RemoveError = Err.Number
+    End Function
+
+    Private Function AddBeforeError(ByVal C As Collection, ByVal Before As Variant) As Long
+        On Error Resume Next
+        C.Add "x", , Before
+        AddBeforeError = Err.Number
+    End Function
+
+    [TestCase]
+    Public Sub Control_ItemOfLongDoubleByte()
+        Dim Got As Variant
+        Assert.Strict.AreEqual 0&, ItemError(Two(), 2&, Got)
+        Assert.Strict.AreEqual "b", Got
+        Assert.Strict.AreEqual 0&, ItemError(Two(), 2#, Got)
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CByte(2), Got)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ItemOutOfRange_Raises9()
+        Assert.Strict.AreEqual 9&, ItemError(Two(), 3)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ItemOfMissingKey_Raises5()
+        Assert.Strict.AreEqual 5&, ItemError(Two(), "z")
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Currency_ReturnsItem()
+        Dim Got As Variant
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CCur(2), Got)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Decimal_ReturnsItem()
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CDec(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Date_ReturnsItem()
+        Assert.Strict.AreEqual 0&, ItemError(Two(), CDate(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Remove_Currency_Removes()
+        Assert.Strict.AreEqual 0&, RemoveError(Two(), CCur(2))
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_Currency_Adds()
+        Assert.Strict.AreEqual 0&, AddBeforeError(Two(), CCur(2))
+    End Sub
+
+    [TestCase]
+    Public Sub Item_EmptyCollection_Raises5()
+        Assert.Strict.AreEqual 5&, ItemError(New Collection, 1)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Null_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), Null)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_Object_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), New Collection)
+    End Sub
+
+    [TestCase]
+    Public Sub Item_BeyondLong_Raises13()
+        Assert.Strict.AreEqual 13&, ItemError(Two(), 2147483648#)
+    End Sub
+
+    [TestCase]
+    Public Sub Remove_Null_Raises13()
+        Assert.Strict.AreEqual 13&, RemoveError(Two(), Null)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_MinusOne_Raises9()
+        Assert.Strict.AreEqual 9&, AddBeforeError(Two(), -1)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_Empty_Raises9()
+        Assert.Strict.AreEqual 9&, AddBeforeError(Two(), Empty)
+    End Sub
+
+    [TestCase]
+    Public Sub AddBefore_BeyondLong_Raises13()
+        Assert.Strict.AreEqual 13&, AddBeforeError(Two(), 2147483648#)
+    End Sub
+
+    [TestCase]
+    Public Sub Add_EmptyKey_Raises13()
+        Dim C As New Collection
+        On Error Resume Next
+        C.Add "x", Empty
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+End Module
diff --git a/bugs/collection-index-checks/src/Sources/Startup.twin b/bugs/collection-index-checks/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/collection-index-checks/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/collection-index-checks/vb6/Module1.bas b/bugs/collection-index-checks/vb6/Module1.bas
new file mode 100644
index 000000000..497ab605b
--- /dev/null
+++ b/bugs/collection-index-checks/vb6/Module1.bas
@@ -0,0 +1,67 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/collection-index-checks: the cases of src/Sources/RegressionTests.twin,
+' in the same order, each printing the error VB6 raises (0: none). Build and run it with:
+'     node scripts/bug_repro.mjs vb6 collection-index-checks
+
+Private Function Two() As Collection
+    Set Two = New Collection
+    Two.Add "a"
+    Two.Add "b"
+End Function
+
+Private Function ItemError(ByVal C As Collection, ByVal Index As Variant) As Long
+    Dim Got As Variant
+    On Error Resume Next
+    Got = C.Item(Index)
+    ItemError = Err.Number
+End Function
+
+Private Function RemoveError(ByVal C As Collection, ByVal Index As Variant) As Long
+    On Error Resume Next
+    C.Remove Index
+    RemoveError = Err.Number
+End Function
+
+Private Function AddBeforeError(ByVal C As Collection, ByVal Before As Variant) As Long
+    On Error Resume Next
+    C.Add "x", , Before
+    AddBeforeError = Err.Number
+End Function
+
+Private Sub Report(ByVal Name As String, ByVal Number As Long)
+    Print #9, Name & ": " & Number
+End Sub
+
+Sub Main()
+    On Error GoTo Fail
+    Open App.Path & "\out.txt" For Output As #9
+    Report "Control_ItemOfLongDoubleByte", ItemError(Two(), 2&) + ItemError(Two(), 2#) + ItemError(Two(), CByte(2))
+    Report "Control_ItemOutOfRange_Raises9", ItemError(Two(), 3)
+    Report "Control_ItemOfMissingKey_Raises5", ItemError(Two(), "z")
+    Report "Item_Currency_ReturnsItem", ItemError(Two(), CCur(2))
+    Report "Item_Decimal_ReturnsItem", ItemError(Two(), CDec(2))
+    Report "Item_Date_ReturnsItem", ItemError(Two(), CDate(2))
+    Report "Remove_Currency_Removes", RemoveError(Two(), CCur(2))
+    Report "AddBefore_Currency_Adds", AddBeforeError(Two(), CCur(2))
+    Report "Item_EmptyCollection_Raises5", ItemError(New Collection, 1)
+    Report "Item_Null_Raises13", ItemError(Two(), Null)
+    Report "Item_Object_Raises13", ItemError(Two(), New Collection)
+    Report "Item_BeyondLong_Raises13", ItemError(Two(), 2147483648#)
+    Report "Remove_Null_Raises13", RemoveError(Two(), Null)
+    Report "AddBefore_MinusOne_Raises9", AddBeforeError(Two(), -1)
+    Report "AddBefore_Empty_Raises9", AddBeforeError(Two(), Empty)
+    Report "AddBefore_BeyondLong_Raises13", AddBeforeError(Two(), 2147483648#)
+    Dim C As New Collection
+    On Error Resume Next
+    C.Add "x", Empty
+    Report "Add_EmptyKey_Raises13", Err.Number
+    On Error GoTo Fail
+    Close #9
+    Exit Sub
+Fail:
+    On Error Resume Next
+    Print #9, "unhandled error " & Err.Number & ": " & Err.Description
+    Close #9
+End Sub
diff --git a/bugs/collection-index-checks/vb6/Probe.vbp b/bugs/collection-index-checks/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/collection-index-checks/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/err-helpfile-helpcontext-codegen/err-helpfile-helpcontext-codegen.twinproj b/bugs/err-helpfile-helpcontext-codegen/err-helpfile-helpcontext-codegen.twinproj
new file mode 100644
index 000000000..eaf7a4397
Binary files /dev/null and b/bugs/err-helpfile-helpcontext-codegen/err-helpfile-helpcontext-codegen.twinproj differ
diff --git a/bugs/err-helpfile-helpcontext-codegen/repro.json b/bugs/err-helpfile-helpcontext-codegen/repro.json
new file mode 100644
index 000000000..8c42fb175
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/repro.json
@@ -0,0 +1,17 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_SetDescription$",
+      "^PASS RegressionTests.Control_SetSource$",
+      "^PASS RegressionTests.Control_SetNumber$",
+      "^PASS RegressionTests.Control_LateBoundHelpFileAndContext$",
+      "^PASS RegressionTests.Control_SetReturnHResultInClassMethod$",
+      "^FAIL RegressionTests.SetHelpFile: aborted",
+      "^FAIL RegressionTests.SetHelpContext: aborted",
+      "^FAIL RegressionTests.SetHelpFileThroughErrObjectVariable: aborted",
+      "^FAIL RegressionTests.SetReturnHResultInModule: aborted"
+    ]
+  }
+}
diff --git a/bugs/err-helpfile-helpcontext-codegen/src/Settings b/bugs/err-helpfile-helpcontext-codegen/src/Settings
new file mode 100644
index 000000000..6b9ff2575
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "ErrHelpfileHelpcontextCodegen",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Assigning Err.HelpFile or Err.HelpContext fails the build with a codegen error",
+	"project.exportPathIsV2": true,
+	"project.id": "{214C222C-5F1B-40EE-BADD-FD3A99F370A4}",
+	"project.name": "ErrHelpfileHelpcontextCodegen",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/err-helpfile-helpcontext-codegen/src/Sources/RegressionTests.twin b/bugs/err-helpfile-helpcontext-codegen/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..0492347d7
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/src/Sources/RegressionTests.twin
@@ -0,0 +1,71 @@
+' The issue's regression tests. Each assigns one property of Err and reads it back.
+' The controls (Description, Source, Number, HelpFile and HelpContext through an
+' Object variable, and ReturnHResult in a class method) pass; HelpFile and
+' HelpContext assigned through Err itself, or through a variable declared As
+' ErrObject, and ReturnHResult in a module procedure, do not build.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_SetDescription()
+        Err.Description = "x"
+        Assert.Strict.AreEqual "x", Err.Description
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetSource()
+        Err.Source = "x"
+        Assert.Strict.AreEqual "x", Err.Source
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetNumber()
+        Err.Number = 5
+        Assert.Strict.AreEqual 5&, Err.Number
+        Err.Clear
+    End Sub
+
+    [TestCase]
+    Public Sub Control_LateBoundHelpFileAndContext()
+        Dim o As Object
+        Set o = Err
+        o.HelpFile = "x"
+        o.HelpContext = 5
+        Assert.Strict.AreEqual "x", Err.HelpFile
+        Assert.Strict.AreEqual 5&, Err.HelpContext
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpFile()
+        Err.HelpFile = "x"
+        Assert.Strict.AreEqual "x", Err.HelpFile
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpContext()
+        Err.HelpContext = 5
+        Assert.Strict.AreEqual 5&, Err.HelpContext
+    End Sub
+
+    [TestCase]
+    Public Sub SetHelpFileThroughErrObjectVariable()
+        Dim e As ErrObject
+        Set e = Err
+        e.HelpFile = "x"
+        Assert.Strict.AreEqual "x", Err.HelpFile
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetReturnHResultInClassMethod()
+        Dim t As New Thing
+        t.Status
+        Assert.Strict.AreEqual 1&, Err.LastHresult
+    End Sub
+
+    [TestCase]
+    Public Sub SetReturnHResultInModule()
+        Err.ReturnHResult = 1
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+End Module
diff --git a/bugs/err-helpfile-helpcontext-codegen/src/Sources/Startup.twin b/bugs/err-helpfile-helpcontext-codegen/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/err-helpfile-helpcontext-codegen/src/Sources/Thing.twin b/bugs/err-helpfile-helpcontext-codegen/src/Sources/Thing.twin
new file mode 100644
index 000000000..f826c80c1
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/src/Sources/Thing.twin
@@ -0,0 +1,8 @@
+' A class whose method sets the HRESULT it returns, as the ReturnHResult page shows.
+Class Thing
+
+    Public Function Status() As Long
+        Err.ReturnHResult = 1
+    End Function
+
+End Class
diff --git a/bugs/err-helpfile-helpcontext-codegen/vb6/Module1.bas b/bugs/err-helpfile-helpcontext-codegen/vb6/Module1.bas
new file mode 100644
index 000000000..390320ccb
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/vb6/Module1.bas
@@ -0,0 +1,25 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of err-helpfile-helpcontext-codegen: the same assignments as the
+' twinBASIC tests, each read back. Build and run with:
+'   node scripts/bug_repro.mjs vb6 err-helpfile-helpcontext-codegen
+
+Sub Main()
+    On Error GoTo Fail
+    Open App.Path & "\out.txt" For Output As #9
+    Err.HelpFile = "x"
+    Print #9, "HelpFile: [" & Err.HelpFile & "]"
+    Err.HelpContext = 5
+    Print #9, "HelpContext: " & Err.HelpContext
+    Dim e As ErrObject
+    Set e = Err
+    e.HelpFile = "y"
+    Print #9, "HelpFile through ErrObject: [" & Err.HelpFile & "]"
+    Close #9
+    Exit Sub
+Fail:
+    On Error Resume Next
+    Print #9, "unhandled error " & Err.Number & ": " & Err.Description
+    Close #9
+End Sub
diff --git a/bugs/err-helpfile-helpcontext-codegen/vb6/Probe.vbp b/bugs/err-helpfile-helpcontext-codegen/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/err-helpfile-helpcontext-codegen/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/err-raise-hresult-mapping/err-raise-hresult-mapping.twinproj b/bugs/err-raise-hresult-mapping/err-raise-hresult-mapping.twinproj
new file mode 100644
index 000000000..fa084a0a6
Binary files /dev/null and b/bugs/err-raise-hresult-mapping/err-raise-hresult-mapping.twinproj differ
diff --git a/bugs/err-raise-hresult-mapping/repro.json b/bugs/err-raise-hresult-mapping/repro.json
new file mode 100644
index 000000000..0d6f9649f
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/repro.json
@@ -0,0 +1,20 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_Raise5_Raises5$",
+      "^PASS RegressionTests\\.Control_RaiseEFail_RaisesEFail$",
+      "^PASS RegressionTests\\.Control_RaiseDispException_RaisesDispException$",
+      "^FAIL RegressionTests\\.Raise_EInvalidArg_Raises5: .*Actual: -2147024809 ",
+      "^FAIL RegressionTests\\.Raise_EOutOfMemory_Raises7: .*Actual: -2147024882 ",
+      "^FAIL RegressionTests\\.Raise_ENotImpl_Raises445: .*Actual: -2147467263 ",
+      "^FAIL RegressionTests\\.Raise_ENoInterface_Raises430: .*Actual: -2147467262 ",
+      "^FAIL RegressionTests\\.Raise_DispUnknownName_Raises438: .*Actual: -2147352570 ",
+      "^FAIL RegressionTests\\.Raise_DispTypeMismatch_Raises13: .*Actual: -2147352571 ",
+      "^FAIL RegressionTests\\.Raise_ClassNotRegistered_Raises429: .*Actual: -2147221164 ",
+      "^FAIL RegressionTests\\.Raise_VbErrorAsHResult_Raises53: .*Actual: -2146828235 ",
+      "^FAIL RegressionTests\\.Number_EInvalidArg_Is5: .*Actual: -2147024809 "
+    ]
+  }
+}
diff --git a/bugs/err-raise-hresult-mapping/src/Settings b/bugs/err-raise-hresult-mapping/src/Settings
new file mode 100644
index 000000000..759972e5d
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "ErrRaiseHresultMapping",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Err.Raise and Err.Number keep an HRESULT that VB turns into a VB error number",
+	"project.exportPathIsV2": true,
+	"project.id": "{F3098B1E-1A6C-44D4-B74D-2CC4A070AE85}",
+	"project.name": "ErrRaiseHresultMapping",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/err-raise-hresult-mapping/src/Sources/RegressionTests.twin b/bugs/err-raise-hresult-mapping/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..9d9f68414
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/src/Sources/RegressionTests.twin
@@ -0,0 +1,77 @@
+' Regression tests: Err.Raise of an HRESULT that has a VB error of the same meaning raises
+' that VB error, as VB6 and 64-bit VBA do, and assigning one to Err.Number stores the VB
+' error. The controls raise a VB number and an HRESULT that VB keeps as it is.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function Raised(ByVal Number As Long) As Long
+        On Error Resume Next
+        Err.Raise Number
+        Raised = Err.Number
+    End Function
+
+    [TestCase]
+    Public Sub Control_Raise5_Raises5()
+        Assert.Strict.AreEqual 5&, Raised(5)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RaiseEFail_RaisesEFail()
+        Assert.Strict.AreEqual &H80004005, Raised(&H80004005)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RaiseDispException_RaisesDispException()
+        Assert.Strict.AreEqual &H80020009, Raised(&H80020009)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_EInvalidArg_Raises5()
+        Assert.Strict.AreEqual 5&, Raised(&H80070057)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_EOutOfMemory_Raises7()
+        Assert.Strict.AreEqual 7&, Raised(&H8007000E)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ENotImpl_Raises445()
+        Assert.Strict.AreEqual 445&, Raised(&H80004001)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ENoInterface_Raises430()
+        Assert.Strict.AreEqual 430&, Raised(&H80004002)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_DispUnknownName_Raises438()
+        Assert.Strict.AreEqual 438&, Raised(&H80020006)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_DispTypeMismatch_Raises13()
+        Assert.Strict.AreEqual 13&, Raised(&H80020005)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_ClassNotRegistered_Raises429()
+        Assert.Strict.AreEqual 429&, Raised(&H80040154)
+    End Sub
+
+    [TestCase]
+    Public Sub Raise_VbErrorAsHResult_Raises53()
+        Assert.Strict.AreEqual 53&, Raised(&H800A0035)
+    End Sub
+
+    [TestCase]
+    Public Sub Number_EInvalidArg_Is5()
+        Err.Number = &H80070057
+        Dim N As Long = Err.Number
+        Err.Clear
+        Assert.Strict.AreEqual 5&, N
+    End Sub
+
+End Module
diff --git a/bugs/err-raise-hresult-mapping/src/Sources/Startup.twin b/bugs/err-raise-hresult-mapping/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/err-raise-hresult-mapping/vb6/Module1.bas b/bugs/err-raise-hresult-mapping/vb6/Module1.bas
new file mode 100644
index 000000000..ac80235d2
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/vb6/Module1.bas
@@ -0,0 +1,45 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/err-raise-hresult-mapping: the cases of src/Sources/RegressionTests.twin,
+' in the same order, each printing the number Err holds after it. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 err-raise-hresult-mapping
+
+Private Function Raised(ByVal Number As Long) As Long
+    On Error Resume Next
+    Err.Raise Number
+    Raised = Err.Number
+End Function
+
+Private Sub Report(ByVal Name As String, ByVal Number As Long)
+    Print #9, Name & ": " & Number
+End Sub
+
+Sub Main()
+    On Error GoTo Fail
+    Open App.Path & "\out.txt" For Output As #9
+    Report "Control_Raise5_Raises5", Raised(5)
+    Report "Control_RaiseEFail_RaisesEFail", Raised(&H80004005)
+    Report "Control_RaiseDispException_RaisesDispException", Raised(&H80020009)
+    Report "Raise_EInvalidArg_Raises5", Raised(&H80070057)
+    Report "Raise_EOutOfMemory_Raises7", Raised(&H8007000E)
+    Report "Raise_ENotImpl_Raises445", Raised(&H80004001)
+    Report "Raise_ENoInterface_Raises430", Raised(&H80004002)
+    Report "Raise_DispUnknownName_Raises438", Raised(&H80020006)
+    Report "Raise_DispTypeMismatch_Raises13", Raised(&H80020005)
+    Report "Raise_ClassNotRegistered_Raises429", Raised(&H80040154)
+    Report "Raise_VbErrorAsHResult_Raises53", Raised(&H800A0035)
+    Dim N As Long
+    On Error Resume Next
+    Err.Number = &H80070057
+    N = Err.Number
+    Err.Clear
+    On Error GoTo Fail
+    Report "Number_EInvalidArg_Is5", N
+    Close #9
+    Exit Sub
+Fail:
+    On Error Resume Next
+    Print #9, "unhandled error " & Err.Number & ": " & Err.Description
+    Close #9
+End Sub
diff --git a/bugs/err-raise-hresult-mapping/vb6/Probe.vbp b/bugs/err-raise-hresult-mapping/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/err-raise-hresult-mapping/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/expression-service-dangling-tokens/expression-service-dangling-tokens.twinproj b/bugs/expression-service-dangling-tokens/expression-service-dangling-tokens.twinproj
new file mode 100644
index 000000000..ffcdd4e2f
Binary files /dev/null and b/bugs/expression-service-dangling-tokens/expression-service-dangling-tokens.twinproj differ
diff --git a/bugs/expression-service-dangling-tokens/repro.json b/bugs/expression-service-dangling-tokens/repro.json
new file mode 100644
index 000000000..28947be0b
--- /dev/null
+++ b/bugs/expression-service-dangling-tokens/repro.json
@@ -0,0 +1,19 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_Eval_WellFormed$",
+      "^PASS RegressionTests.Control_Eval_TwoNumbers_Raises$",
+      "^PASS RegressionTests.Control_Compile_UnclosedAfterOperator_Raises$",
+      "^FAIL RegressionTests.Eval_TrailingPlus_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Eval_TrailingMod_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Eval_UnclosedParenthesis_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Eval_UnopenedParenthesis_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Compile_TrailingPlus_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Compile_TrailingMod_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Compile_UnclosedParenthesis_Raises: .*Actual: 0 ",
+      "^FAIL RegressionTests.Compile_UnopenedParenthesis_Raises: .*Actual: 0 "
+    ]
+  }
+}
diff --git a/bugs/expression-service-dangling-tokens/src/Settings b/bugs/expression-service-dangling-tokens/src/Settings
new file mode 100644
index 000000000..24f386f05
--- /dev/null
+++ b/bugs/expression-service-dangling-tokens/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "ExpressionServiceDanglingTokens",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Eval and TbExpressionService.Compile accept an expression that ends in an operator or has an unmatched parenthesis",
+	"project.exportPathIsV2": true,
+	"project.id": "{31980062-F599-41C1-87EA-9FD72E3D3E1E}",
+	"project.name": "ExpressionServiceDanglingTokens",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/expression-service-dangling-tokens/src/Sources/RegressionTests.twin b/bugs/expression-service-dangling-tokens/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..6774b7eec
--- /dev/null
+++ b/bugs/expression-service-dangling-tokens/src/Sources/RegressionTests.twin
@@ -0,0 +1,83 @@
+' Regression tests: Eval and TbExpressionService.Compile refuse a malformed expression with a
+' run-time error, as they refuse "1 2", instead of leaving out the part they cannot read. On
+' BETA 1010 an expression that ends in an operator, or has a parenthesis with no partner at
+' either end, is accepted, and its value is that of what comes before the fault: each case
+' below gives 2. VBScript's Eval refuses each with 1002, Syntax error, or 1006, Expected ')';
+' Access's Eval with 2431, 2435 or 2436.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function EvalError(ByVal Source As String) As Long
+        Dim V As Variant
+        On Error Resume Next
+        V = Eval(Source)
+        EvalError = Err.Number
+    End Function
+
+    Private Function CompileError(ByVal Source As String) As Long
+        Dim S As New TbExpressionService
+        Dim E As ITbExpression
+        S.AddStdLibraryBinder
+        On Error Resume Next
+        Set E = S.Compile(Source)
+        CompileError = Err.Number
+    End Function
+
+    ' The controls: a well-formed expression, and malformed ones that are refused.
+    [TestCase]
+    Public Sub Control_Eval_WellFormed()
+        Assert.Strict.AreEqual 2, CInt(Eval("(2)"))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Eval_TwoNumbers_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("1 2")
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Compile_UnclosedAfterOperator_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 * (3 + 4")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_TrailingPlus_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2 +")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_TrailingMod_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2 Mod")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_UnclosedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("(2")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_UnopenedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, EvalError("2)")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_TrailingPlus_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 +")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_TrailingMod_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2 Mod")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_UnclosedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("(2")
+    End Sub
+
+    [TestCase]
+    Public Sub Compile_UnopenedParenthesis_Raises()
+        Assert.Strict.AreNotEqual 0&, CompileError("2)")
+    End Sub
+
+End Module
diff --git a/bugs/expression-service-dangling-tokens/src/Sources/Startup.twin b/bugs/expression-service-dangling-tokens/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/expression-service-dangling-tokens/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/expression-service-error-numbers/expression-service-error-numbers.twinproj b/bugs/expression-service-error-numbers/expression-service-error-numbers.twinproj
new file mode 100644
index 000000000..24d187d9b
Binary files /dev/null and b/bugs/expression-service-error-numbers/expression-service-error-numbers.twinproj differ
diff --git a/bugs/expression-service-error-numbers/repro.json b/bugs/expression-service-error-numbers/repro.json
new file mode 100644
index 000000000..b67871fb7
--- /dev/null
+++ b/bugs/expression-service-error-numbers/repro.json
@@ -0,0 +1,17 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_Eval_Sum$",
+      "^PASS RegressionTests.Control_DictionaryAddOfAKeyItHolds_Raises457$",
+      "^FAIL RegressionTests.Eval_DivisionByZero_Raises11: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Eval_DivisionByZero_DescriptionIsDivisionByZero: .*Actual: \"Automation error\"",
+      "^FAIL RegressionTests.Eval_CIntOfText_Raises13: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Eval_CIntOverflow_Raises6: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Eval_SqrOfNegative_Raises5: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Evaluate_DivisionByZero_Raises11: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests.Evaluate_BoundObjectsError_Raises457: .*Actual: -2147467259 "
+    ]
+  }
+}
diff --git a/bugs/expression-service-error-numbers/src/Settings b/bugs/expression-service-error-numbers/src/Settings
new file mode 100644
index 000000000..063a95fc0
--- /dev/null
+++ b/bugs/expression-service-error-numbers/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "ExpressionServiceErrorNumbers",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Eval and ITbExpression.Evaluate raise -2147467259 for every error inside the expression",
+	"project.exportPathIsV2": true,
+	"project.id": "{7F94F222-CF31-426C-963D-719182EFF8B8}",
+	"project.name": "ExpressionServiceErrorNumbers",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/expression-service-error-numbers/src/Sources/RegressionTests.twin b/bugs/expression-service-error-numbers/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..dbbde0a7b
--- /dev/null
+++ b/bugs/expression-service-error-numbers/src/Sources/RegressionTests.twin
@@ -0,0 +1,95 @@
+' Regression tests: an error raised by a function, an operator or a bound object's member
+' while Eval or ITbExpression.Evaluate evaluates an expression reaches the caller unchanged,
+' with the number and description the same code raises written in a procedure, as VBScript's
+' Eval and Access's Eval pass it on. On BETA 1010 each of these raises -2147467259, whose
+' description is "Automation error" in the IDE and in an exe's first such error, and
+' "Unspecified error" after it.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Function EvalError(ByVal Source As String) As Long
+        Dim V As Variant
+        On Error Resume Next
+        V = Eval(Source)
+        EvalError = Err.Number
+    End Function
+
+    ' The controls: an expression that raises nothing, and a bound object's error raised by
+    ' the same call written in a procedure.
+    [TestCase]
+    Public Sub Control_Eval_Sum()
+        Assert.Strict.AreEqual 4, CInt(Eval("2 + 2"))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_DictionaryAddOfAKeyItHolds_Raises457()
+        Dim D As Object = CreateObject("Scripting.Dictionary")
+        Dim E As Long
+        D.Add 1, 1
+        On Error Resume Next
+        D.Add 1, 2
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 457&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_DivisionByZero_Raises11()
+        Assert.Strict.AreEqual 11&, EvalError("1 / 0")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_DivisionByZero_DescriptionIsDivisionByZero()
+        Dim V As Variant, D As String
+        On Error Resume Next
+        V = Eval("1 / 0")
+        D = Err.Description
+        On Error GoTo 0
+        Assert.Strict.AreEqual "Division by zero", D
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_CIntOfText_Raises13()
+        Assert.Strict.AreEqual 13&, EvalError("CInt(""abc"")")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_CIntOverflow_Raises6()
+        Assert.Strict.AreEqual 6&, EvalError("CInt(40000)")
+    End Sub
+
+    [TestCase]
+    Public Sub Eval_SqrOfNegative_Raises5()
+        Assert.Strict.AreEqual 5&, EvalError("Sqr(-1)")
+    End Sub
+
+    [TestCase]
+    Public Sub Evaluate_DivisionByZero_Raises11()
+        Dim S As New TbExpressionService
+        Dim X As ITbExpression, V As Variant, E As Long
+        S.AddStdLibraryBinder
+        Set X = S.Compile("1 / 0")
+        On Error Resume Next
+        V = X.Evaluate()
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Evaluate_BoundObjectsError_Raises457()
+        Dim S As New TbExpressionService
+        Dim D As Object = CreateObject("Scripting.Dictionary")
+        Dim X As ITbExpression, V As Variant, E As Long
+        D.Add 1, 1
+        S.AddCustomBinderObject "D", D
+        Set X = S.Compile("D.Add(1, 2)")
+        On Error Resume Next
+        V = X.Evaluate()
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 457&, E
+    End Sub
+
+End Module
diff --git a/bugs/expression-service-error-numbers/src/Sources/Startup.twin b/bugs/expression-service-error-numbers/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/expression-service-error-numbers/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/file-errors-unspecified/file-errors-unspecified.twinproj b/bugs/file-errors-unspecified/file-errors-unspecified.twinproj
index bd08df406..c11437274 100644
Binary files a/bugs/file-errors-unspecified/file-errors-unspecified.twinproj and b/bugs/file-errors-unspecified/file-errors-unspecified.twinproj differ
diff --git a/bugs/file-errors-unspecified/repro.json b/bugs/file-errors-unspecified/repro.json
index 8a98b7f3a..68c9ac9ec 100644
--- a/bugs/file-errors-unspecified/repro.json
+++ b/bugs/file-errors-unspecified/repro.json
@@ -39,7 +39,37 @@
       "^Print to file number 99, not open: -2147467259 ",
       "^Line Input from file number 99, not open: -2147467259 ",
       "^Seek to position 0: -2147467259 ",
-      "^Put a record longer than Len: -2147467259 "
+      "^Put a record longer than Len: -2147467259 ",
+      "^ChDir to a file: -2147467259 ",
+      "^ChDir to a zero-length string: -2147467259 ",
+      "^ChDir to a wildcard: -2147467259 ",
+      "^ChDrive to a drive that does not exist: -2147467259 ",
+      "^ChDrive to a character that is not a letter: -2147467259 ",
+      "^CurDir of a drive that does not exist: -2147467259 ",
+      "^CurDir of a character that is not a letter: -2147467259 ",
+      "^Dir without a pathname after it returned a zero-length string: -2147467259 ",
+      "^Dir of a file name with a backslash at its end: -2147467259 ",
+      "^Dir of a name longer than 255 characters: -2147467259 ",
+      "^FileAttr with a returntype of 2: -2147467259 ",
+      "^FileCopy from a zero-length string: -2147467259 ",
+      "^FileCopy from a wildcard: -2147467259 ",
+      "^FileLen in missing folder: -2147467259 ",
+      "^FileLen of a wildcard that matches nothing: -2147467259 ",
+      "^FreeFile with every file number from 1 to 255 in use: -2147467259 ",
+      "^GetAttr of a wildcard: -2147467259 ",
+      "^GetAttr of a name with a character a name cannot hold: -2147467259 ",
+      "^Input past the end of the file: -2147467259 ",
+      "^Input from a file open For Output: -2147467259 ",
+      "^Input of a negative number of characters: -2147467259 ",
+      "^Input from file number 99, not open: -2147467259 ",
+      "^InputB past the end of the file: -2147467259 ",
+      "^Kill of a folder: -2147467259 ",
+      "^Kill of a pattern that matches a read-only file: -2147467259 ",
+      "^MkDir of a zero-length string: -2147467259 ",
+      "^RmDir of a file: -2147467259 ",
+      "^RmDir of the current directory: -2147467259 ",
+      "^SetAttr of a wildcard: -2147467259 ",
+      "^Width of file number 99, not open: -2147467259 "
     ]
   }
 }
diff --git a/bugs/file-errors-unspecified/src/Sources/Startup.twin b/bugs/file-errors-unspecified/src/Sources/Startup.twin
index 956ec0df1..611cf382c 100644
--- a/bugs/file-errors-unspecified/src/Sources/Startup.twin
+++ b/bugs/file-errors-unspecified/src/Sources/Startup.twin
@@ -1,6 +1,17 @@
 ' Each case makes one file statement or function fail and prints the error it raises.
 Module Startup
 
+    Private Declare PtrSafe Function GetLogicalDrives Lib "kernel32" () As Long
+
+    ' A drive letter that no drive has, from Z down.
+    Private Function NoDrive() As String
+        Dim m As Long, i As Long
+        m = GetLogicalDrives()
+        For i = 25 To 3 Step -1
+            If (m And (2 ^ i)) = 0 Then NoDrive = Chr$(65 + i): Exit Function
+        Next
+    End Function
+
     Private Sub Show(ByVal Label As String)
         Debug.Print Label & ": " & Err.Number & " " & Err.Description
     End Sub
@@ -231,6 +242,161 @@ Module Startup
         Show "Put a record longer than Len"
         Close #f
 
+        ' ---- added by batch 7 of the run-time errors work (WIP.Errors.md)
+        Dim i As Long, here As String
+
+        Err.Clear
+        ChDir d & "\exists.txt"
+        Show "ChDir to a file"
+
+        Err.Clear
+        ChDir ""
+        Show "ChDir to a zero-length string"
+
+        Err.Clear
+        ChDir d & "\*"
+        Show "ChDir to a wildcard"
+
+        Err.Clear
+        ChDrive NoDrive()
+        Show "ChDrive to a drive that does not exist"
+
+        Err.Clear
+        ChDrive "1"
+        Show "ChDrive to a character that is not a letter"
+
+        Err.Clear
+        s = CurDir(NoDrive())
+        Show "CurDir of a drive that does not exist"
+
+        Err.Clear
+        s = CurDir("1")
+        Show "CurDir of a character that is not a letter"
+
+        Err.Clear
+        s = Dir(d & "\missing.txt")
+        Err.Clear
+        s = Dir()
+        Show "Dir without a pathname after it returned a zero-length string"
+
+        Err.Clear
+        s = Dir(d & "\exists.txt\")
+        Show "Dir of a file name with a backslash at its end"
+
+        Err.Clear
+        s = Dir(d & "\" & String(256, "a"))
+        Show "Dir of a name longer than 255 characters"
+
+        Err.Clear
+        f = FreeFile
+        Open d & "\exists.txt" For Input As #f
+        n = FileAttr(f, 2)
+        Show "FileAttr with a returntype of 2"
+        Close #f
+
+        Err.Clear
+        FileCopy "", d & "\copy.txt"
+        Show "FileCopy from a zero-length string"
+
+        Err.Clear
+        FileCopy d & "\*.txt", d & "\copy.txt"
+        Show "FileCopy from a wildcard"
+
+        Err.Clear
+        n = FileLen(d & "\nofolder\x.txt")
+        Show "FileLen in missing folder"
+
+        Err.Clear
+        n = FileLen(d & "\z*")
+        Show "FileLen of a wildcard that matches nothing"
+
+        Err.Clear
+        For i = 1 To 255
+            Open d & "\n" & i & ".txt" For Output As #i
+        Next
+        Err.Clear
+        f = FreeFile
+        Show "FreeFile with every file number from 1 to 255 in use"
+        For i = 1 To 255
+            Close #i
+        Next
+
+        Err.Clear
+        n = GetAttr(d & "\*.txt")
+        Show "GetAttr of a wildcard"
+
+        Err.Clear
+        n = GetAttr(d & "\a<b")
+        Show "GetAttr of a name with a character a name cannot hold"
+
+        Err.Clear
+        f = FreeFile
+        Open d & "\exists.txt" For Input As #f
+        s = Input(4, #f)
+        Show "Input past the end of the file"
+        Close #f
+
+        Err.Clear
+        f = FreeFile
+        Open d & "\output.txt" For Output As #f
+        s = Input(1, #f)
+        Show "Input from a file open For Output"
+        Close #f
+
+        Err.Clear
+        f = FreeFile
+        Open d & "\exists.txt" For Input As #f
+        s = Input(-1, #f)
+        Show "Input of a negative number of characters"
+        Close #f
+
+        Err.Clear
+        s = Input(1, #99)
+        Show "Input from file number 99, not open"
+
+        Err.Clear
+        f = FreeFile
+        Open d & "\exists.txt" For Input As #f
+        s = InputB(4, #f)
+        Show "InputB past the end of the file"
+        Close #f
+
+        Err.Clear
+        Kill d & "\full"
+        Show "Kill of a folder"
+
+        Err.Clear
+        Kill d & "\read*"
+        Show "Kill of a pattern that matches a read-only file"
+
+        Err.Clear
+        MkDir ""
+        Show "MkDir of a zero-length string"
+
+        Err.Clear
+        RmDir d & "\exists.txt"
+        Show "RmDir of a file"
+
+        Err.Clear
+        here = CurDir$
+        MkDir d & "\cwd"
+        ChDrive d
+        ChDir d & "\cwd"
+        Err.Clear
+        RmDir d & "\cwd"
+        Show "RmDir of the current directory"
+        ChDrive here
+        ChDir here
+        RmDir d & "\cwd"
+
+        Err.Clear
+        SetAttr d & "\*.txt", vbNormal
+        Show "SetAttr of a wildcard"
+
+        Err.Clear
+        Width #99, 5
+        Show "Width of file number 99, not open"
+
         Err.Clear
         SetAttr d & "\readonly.txt", vbNormal
         Kill d & "\*.*"
diff --git a/bugs/file-errors-unspecified/vb6/Module1.bas b/bugs/file-errors-unspecified/vb6/Module1.bas
index 03573bc5d..09b5f8e02 100644
--- a/bugs/file-errors-unspecified/vb6/Module1.bas
+++ b/bugs/file-errors-unspecified/vb6/Module1.bas
@@ -5,6 +5,17 @@ Option Explicit
 ' Build and run it with:  node scripts/bug_repro.mjs vb6 file-errors-unspecified
 ' File number 9 is out.txt, so no case closes every file or uses number 9.
 
+Private Declare Function GetLogicalDrives Lib "kernel32" () As Long
+
+' A drive letter that no drive has, from Z down.
+Private Function NoDrive() As String
+    Dim m As Long, i As Long
+    m = GetLogicalDrives()
+    For i = 25 To 3 Step -1
+        If (m And (2 ^ i)) = 0 Then NoDrive = Chr$(65 + i): Exit Function
+    Next
+End Function
+
 Sub Show(ByVal Label As String)
     Print #9, Label & ": " & Err.Number & " " & Err.Description
 End Sub
@@ -247,6 +258,161 @@ Sub Cases()
     Show "Put a record longer than Len"
     Close #f
 
+    ' ---- added by batch 7 of the run-time errors work (WIP.Errors.md)
+    Dim i As Long, here As String
+
+    Err.Clear
+    ChDir d & "\exists.txt"
+    Show "ChDir to a file"
+
+    Err.Clear
+    ChDir ""
+    Show "ChDir to a zero-length string"
+
+    Err.Clear
+    ChDir d & "\*"
+    Show "ChDir to a wildcard"
+
+    Err.Clear
+    ChDrive NoDrive()
+    Show "ChDrive to a drive that does not exist"
+
+    Err.Clear
+    ChDrive "1"
+    Show "ChDrive to a character that is not a letter"
+
+    Err.Clear
+    s = CurDir(NoDrive())
+    Show "CurDir of a drive that does not exist"
+
+    Err.Clear
+    s = CurDir("1")
+    Show "CurDir of a character that is not a letter"
+
+    Err.Clear
+    s = Dir(d & "\missing.txt")
+    Err.Clear
+    s = Dir()
+    Show "Dir without a pathname after it returned a zero-length string"
+
+    Err.Clear
+    s = Dir(d & "\exists.txt\")
+    Show "Dir of a file name with a backslash at its end"
+
+    Err.Clear
+    s = Dir(d & "\" & String(256, "a"))
+    Show "Dir of a name longer than 255 characters"
+
+    Err.Clear
+    f = FreeFile
+    Open d & "\exists.txt" For Input As #f
+    n = FileAttr(f, 2)
+    Show "FileAttr with a returntype of 2"
+    Close #f
+
+    Err.Clear
+    FileCopy "", d & "\copy.txt"
+    Show "FileCopy from a zero-length string"
+
+    Err.Clear
+    FileCopy d & "\*.txt", d & "\copy.txt"
+    Show "FileCopy from a wildcard"
+
+    Err.Clear
+    n = FileLen(d & "\nofolder\x.txt")
+    Show "FileLen in missing folder"
+
+    Err.Clear
+    n = FileLen(d & "\z*")
+    Show "FileLen of a wildcard that matches nothing"
+
+    Err.Clear
+    For i = 1 To 255
+        If i <> 9 Then Open d & "\n" & i & ".txt" For Output As #i
+    Next
+    Err.Clear
+    f = FreeFile
+    Show "FreeFile with every file number from 1 to 255 in use"
+    For i = 1 To 255
+        If i <> 9 Then Close #i
+    Next
+
+    Err.Clear
+    n = GetAttr(d & "\*.txt")
+    Show "GetAttr of a wildcard"
+
+    Err.Clear
+    n = GetAttr(d & "\a<b")
+    Show "GetAttr of a name with a character a name cannot hold"
+
+    Err.Clear
+    f = FreeFile
+    Open d & "\exists.txt" For Input As #f
+    s = Input(4, #f)
+    Show "Input past the end of the file"
+    Close #f
+
+    Err.Clear
+    f = FreeFile
+    Open d & "\output.txt" For Output As #f
+    s = Input(1, #f)
+    Show "Input from a file open For Output"
+    Close #f
+
+    Err.Clear
+    f = FreeFile
+    Open d & "\exists.txt" For Input As #f
+    s = Input(-1, #f)
+    Show "Input of a negative number of characters"
+    Close #f
+
+    Err.Clear
+    s = Input(1, #99)
+    Show "Input from file number 99, not open"
+
+    Err.Clear
+    f = FreeFile
+    Open d & "\exists.txt" For Input As #f
+    s = InputB(4, #f)
+    Show "InputB past the end of the file"
+    Close #f
+
+    Err.Clear
+    Kill d & "\full"
+    Show "Kill of a folder"
+
+    Err.Clear
+    Kill d & "\read*"
+    Show "Kill of a pattern that matches a read-only file"
+
+    Err.Clear
+    MkDir ""
+    Show "MkDir of a zero-length string"
+
+    Err.Clear
+    RmDir d & "\exists.txt"
+    Show "RmDir of a file"
+
+    Err.Clear
+    here = CurDir$
+    MkDir d & "\cwd"
+    ChDrive d
+    ChDir d & "\cwd"
+    Err.Clear
+    RmDir d & "\cwd"
+    Show "RmDir of the current directory"
+    ChDrive here
+    ChDir here
+    RmDir d & "\cwd"
+
+    Err.Clear
+    SetAttr d & "\*.txt", vbNormal
+    Show "SetAttr of a wildcard"
+
+    Err.Clear
+    Width #99, 5
+    Show "Width of file number 99, not open"
+
     Err.Clear
     SetAttr d & "\readonly.txt", vbNormal
     Kill d & "\*.*"
diff --git a/bugs/filecopy-error-numbers/filecopy-error-numbers.twinproj b/bugs/filecopy-error-numbers/filecopy-error-numbers.twinproj
new file mode 100644
index 000000000..bc64d67ca
Binary files /dev/null and b/bugs/filecopy-error-numbers/filecopy-error-numbers.twinproj differ
diff --git a/bugs/filecopy-error-numbers/repro.json b/bugs/filecopy-error-numbers/repro.json
new file mode 100644
index 000000000..db0bf4948
--- /dev/null
+++ b/bugs/filecopy-error-numbers/repro.json
@@ -0,0 +1,17 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.FileCopy_MissingSource_Raises53$",
+      "^PASS RegressionTests\\.FileCopy_SourceOpenForAppend_Raises55$",
+      "^FAIL RegressionTests\\.FileCopy_OntoItself_Raises70: .*Actual: 55 ",
+      "^FAIL RegressionTests\\.FileCopy_OntoItselfOtherCase_Raises70: .*Actual: 55 ",
+      "^FAIL RegressionTests\\.FileCopy_SourceOpenLockRead_Raises70: .*Actual: 55 ",
+      "^FAIL RegressionTests\\.FileCopy_SourceFolder_Raises75: .*Actual: 70 ",
+      "^FAIL RegressionTests\\.FileCopy_DestinationFolder_Raises75: .*Actual: 70 ",
+      "^FAIL RegressionTests\\.FileCopy_DestinationReadOnly_Raises75: .*Actual: 70 ",
+      "^FAIL RegressionTests\\.FileCopy_DestinationHidden_Raises75: .*Actual: 70 "
+    ]
+  }
+}
diff --git a/bugs/filecopy-error-numbers/src/Settings b/bugs/filecopy-error-numbers/src/Settings
new file mode 100644
index 000000000..c361e09e6
--- /dev/null
+++ b/bugs/filecopy-error-numbers/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "FilecopyErrorNumbers",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: FileCopy raises 70 where VB6 raises 75, and 55 where VB6 raises 70",
+	"project.exportPathIsV2": true,
+	"project.id": "{FB2740BC-566E-441B-A906-4712886CBBDD}",
+	"project.name": "FilecopyErrorNumbers",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/filecopy-error-numbers/src/Sources/RegressionTests.twin b/bugs/filecopy-error-numbers/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..1bbf339a0
--- /dev/null
+++ b/bugs/filecopy-error-numbers/src/Sources/RegressionTests.twin
@@ -0,0 +1,273 @@
+' Regression tests: FileCopy raises VB6's numbers, 70 for a copy onto its own source or of a
+' source locked against reading, and 75 for a folder or a read-only or hidden destination.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+    ' folder of its own under the temporary folder, made the current directory and filled with
+    ' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+    ' the folder full holding f.txt, and the folder is deleted after it.
+    ' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+    ' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+    ' process id under the temporary folder (the four runtimes run at once), fills it with the
+    ' fixtures below and makes it the current directory, so that a case names its files relatively
+    ' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+    ' and deletes the folder with everything in it, read-only, hidden and system files included.
+    ' The error the case raised is kept: files_End raises it again, with its description.
+    '
+    ' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+    ' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+    '
+    ' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+    ' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+    ' The folder and the files are made with Windows' own calls, never with a statement under test,
+    ' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+    ' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+    '
+    ' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+    ' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+    ' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+    ' compiles only the #Else branch.
+
+    #If VBA7 Then
+    Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+    Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+    Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+    Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+    Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+    #Else
+    Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+    Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+    Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+    Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+    Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+    Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+    #End If
+
+    ' The current directory before the case, put back by files_End.
+    Private files_Saved As String
+
+    Private Function files_Name() As String
+        files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+    End Function
+
+    ' The case's folder: the temporary folder's path, with no backslash at its end.
+    Private Function files_Dir() As String
+        Dim B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetTempPath(1024, StrPtr(B))
+        B = Left$(B, N)
+        If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+        files_Dir = B & "\" & files_Name()
+    End Function
+
+    Private Function files_Attr(ByVal Path As String) As Long
+        files_Attr = files_GetFileAttributes(StrPtr(Path))
+    End Function
+
+    Private Sub files_Expect(ByVal Cond As Boolean)
+        If Err.Number <> 0 Then Exit Sub
+        If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+    End Sub
+
+    ' A drive letter that no drive has, from Z down.
+    Private Function files_NoDrive() As String
+        Dim Mask As Long, I As Long
+        Mask = files_GetLogicalDrives()
+        For I = 25 To 3 Step -1
+            If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+        Next
+    End Function
+
+    ' Deletes Path and everything in it, whatever their attributes.
+    Private Sub files_DeleteTree(ByVal Path As String)
+        Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+        Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+        ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+        Pattern = Path & "\*"
+        H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+        If H <> -1 Then
+            Do
+                Nm = String$(260, vbNullChar)
+                files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+                N = InStr(Nm, vbNullChar)
+                If N > 0 Then Nm = Left$(Nm, N - 1)
+                files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+                If Nm <> "." And Nm <> ".." Then
+                    If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                    Names(Count) = Nm
+                    Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                    Count = Count + 1
+                End If
+            Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+            files_FindClose H
+        End If
+        For I = 0 To Count - 1
+            Nm = Path & "\" & Names(I)
+            files_SetFileAttributes StrPtr(Nm), 128
+            If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+        Next
+        files_SetFileAttributes StrPtr(Path), 128
+        files_RemoveDirectory StrPtr(Path)
+    End Sub
+
+    ' Closes every file, puts the current directory back and deletes the folder.
+    Private Sub files_Clear()
+        Dim D As String
+        Close
+        If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+        D = files_Dir()
+        If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+        If files_Attr(D) <> -1 Then files_DeleteTree D
+    End Sub
+
+    Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+        Dim F As Integer
+        F = FreeFile
+        Open Path For Output As #F
+        Print #F, Contents;
+        Close #F
+        If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+    End Sub
+
+    Private Sub files_Begin()
+        Dim D As String, B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetCurrentDirectory(1024, StrPtr(B))
+        files_Saved = Left$(B, N)
+        files_Clear
+        D = files_Dir()
+        If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+        If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+        files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+        files_Make D & "\empty.txt", "", 0
+        files_Make D & "\ro.txt", "x", 1
+        files_Make D & "\hid.txt", "x", 2
+        files_CreateDirectory StrPtr(D & "\sub"), 0
+        files_CreateDirectory StrPtr(D & "\full"), 0
+        files_Make D & "\full\f.txt", "x", 0
+    End Sub
+
+    Private Sub files_End()
+        Dim N As Long, D As String
+        N = Err.Number: D = Err.Description
+        files_Clear
+        If N <> 0 Then Err.Raise N, , D
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileCopy_MissingSource_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "nosuch.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileCopy_SourceOpenForAppend_Raises55()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Append As #1
+        FileCopy "a.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 55&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_OntoItself_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "a.txt"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_OntoItselfOtherCase_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "A.TXT"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_SourceOpenLockRead_Raises70()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Input Lock Read As #1
+        FileCopy "a.txt", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 70&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_SourceFolder_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "sub", "b.txt"
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationFolder_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "sub"
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationReadOnly_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "ro.txt"
+        Holds = FileLen("ro.txt") = 1
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub FileCopy_DestinationHidden_Raises75()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        FileCopy "a.txt", "hid.txt"
+        Holds = FileLen("hid.txt") = 1
+        files_End
+        Assert.Strict.AreEqual 75&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
diff --git a/bugs/filecopy-error-numbers/src/Sources/Startup.twin b/bugs/filecopy-error-numbers/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/filecopy-error-numbers/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/filecopy-error-numbers/vb6/Module1.bas b/bugs/filecopy-error-numbers/vb6/Module1.bas
new file mode 100644
index 000000000..8c231bb44
--- /dev/null
+++ b/bugs/filecopy-error-numbers/vb6/Module1.bas
@@ -0,0 +1,257 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/filecopy-error-numbers: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises and, where the case checks it, whether the file
+' is as the case expects. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 filecopy-error-numbers
+' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+' folder of its own under the temporary folder, made the current directory and filled with
+' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+' the folder full holding f.txt, and the folder is deleted after it.
+' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+' process id under the temporary folder (the four runtimes run at once), fills it with the
+' fixtures below and makes it the current directory, so that a case names its files relatively
+' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+' and deletes the folder with everything in it, read-only, hidden and system files included.
+' The error the case raised is kept: files_End raises it again, with its description.
+'
+' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+'
+' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+' The folder and the files are made with Windows' own calls, never with a statement under test,
+' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+'
+' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+' compiles only the #Else branch.
+
+#If VBA7 Then
+Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+#Else
+Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+#End If
+
+' The current directory before the case, put back by files_End.
+Private files_Saved As String
+
+Private Function files_Name() As String
+    files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+End Function
+
+' The case's folder: the temporary folder's path, with no backslash at its end.
+Private Function files_Dir() As String
+    Dim B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetTempPath(1024, StrPtr(B))
+    B = Left$(B, N)
+    If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+    files_Dir = B & "\" & files_Name()
+End Function
+
+Private Function files_Attr(ByVal Path As String) As Long
+    files_Attr = files_GetFileAttributes(StrPtr(Path))
+End Function
+
+Private Sub files_Expect(ByVal Cond As Boolean)
+    If Err.Number <> 0 Then Exit Sub
+    If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+End Sub
+
+' A drive letter that no drive has, from Z down.
+Private Function files_NoDrive() As String
+    Dim Mask As Long, I As Long
+    Mask = files_GetLogicalDrives()
+    For I = 25 To 3 Step -1
+        If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+    Next
+End Function
+
+' Deletes Path and everything in it, whatever their attributes.
+Private Sub files_DeleteTree(ByVal Path As String)
+    Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+    Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+    ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+    Pattern = Path & "\*"
+    H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+    If H <> -1 Then
+        Do
+            Nm = String$(260, vbNullChar)
+            files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+            N = InStr(Nm, vbNullChar)
+            If N > 0 Then Nm = Left$(Nm, N - 1)
+            files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+            If Nm <> "." And Nm <> ".." Then
+                If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                Names(Count) = Nm
+                Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                Count = Count + 1
+            End If
+        Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+        files_FindClose H
+    End If
+    For I = 0 To Count - 1
+        Nm = Path & "\" & Names(I)
+        files_SetFileAttributes StrPtr(Nm), 128
+        If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+    Next
+    files_SetFileAttributes StrPtr(Path), 128
+    files_RemoveDirectory StrPtr(Path)
+End Sub
+
+' Closes every file, puts the current directory back and deletes the folder.
+Private Sub files_Clear()
+    Dim D As String
+    Close
+    If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+    D = files_Dir()
+    If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+    If files_Attr(D) <> -1 Then files_DeleteTree D
+End Sub
+
+Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+    Dim F As Integer
+    F = FreeFile
+    Open Path For Output As #F
+    Print #F, Contents;
+    Close #F
+    If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+End Sub
+
+Private Sub files_Begin()
+    Dim D As String, B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetCurrentDirectory(1024, StrPtr(B))
+    files_Saved = Left$(B, N)
+    files_Clear
+    D = files_Dir()
+    If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+    If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+    files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+    files_Make D & "\empty.txt", "", 0
+    files_Make D & "\ro.txt", "x", 1
+    files_Make D & "\hid.txt", "x", 2
+    files_CreateDirectory StrPtr(D & "\sub"), 0
+    files_CreateDirectory StrPtr(D & "\full"), 0
+    files_Make D & "\full\f.txt", "x", 0
+End Sub
+
+Private Sub files_End()
+    Dim N As Long, D As String
+    N = Err.Number: D = Err.Description
+    files_Clear
+    If N <> 0 Then Err.Raise N, , D
+End Sub
+
+' out.txt is opened for each line: the harness closes every file after a case.
+Private Sub Report(ByVal Label As String, ByVal Check As String)
+    Dim F As Integer
+    F = FreeFile
+    Open App.Path & "\out.txt" For Append As #F
+    Print #F, Label & ": " & Err.Number & " " & Err.Description & Check
+    Close #F
+End Sub
+
+Sub Main()
+    Dim V As Variant, Holds As Boolean
+    On Error Resume Next
+    Kill App.Path & "\out.txt"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "nosuch.txt", "b.txt"
+    files_End
+    Report "FileCopy_MissingSource_Raises53", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Open "a.txt" For Append As #1
+    FileCopy "a.txt", "b.txt"
+    files_End
+    Report "FileCopy_SourceOpenForAppend_Raises55", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "a.txt", "a.txt"
+    files_End
+    Report "FileCopy_OntoItself_Raises70", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "a.txt", "A.TXT"
+    files_End
+    Report "FileCopy_OntoItselfOtherCase_Raises70", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Open "a.txt" For Input Lock Read As #1
+    FileCopy "a.txt", "b.txt"
+    files_End
+    Report "FileCopy_SourceOpenLockRead_Raises70", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "sub", "b.txt"
+    files_End
+    Report "FileCopy_SourceFolder_Raises75", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "a.txt", "sub"
+    files_End
+    Report "FileCopy_DestinationFolder_Raises75", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "a.txt", "ro.txt"
+    Holds = FileLen("ro.txt") = 1
+    files_End
+    Report "FileCopy_DestinationReadOnly_Raises75", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    FileCopy "a.txt", "hid.txt"
+    Holds = FileLen("hid.txt") = 1
+    files_End
+    Report "FileCopy_DestinationHidden_Raises75", " (check " & IIf(Holds, "holds", "fails") & ")"
+End Sub
diff --git a/bugs/filecopy-error-numbers/vb6/Probe.vbp b/bugs/filecopy-error-numbers/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/filecopy-error-numbers/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/filesystem-argument-checks/filesystem-argument-checks.twinproj b/bugs/filesystem-argument-checks/filesystem-argument-checks.twinproj
new file mode 100644
index 000000000..0d8b3a080
Binary files /dev/null and b/bugs/filesystem-argument-checks/filesystem-argument-checks.twinproj differ
diff --git a/bugs/filesystem-argument-checks/repro.json b/bugs/filesystem-argument-checks/repro.json
new file mode 100644
index 000000000..f67d80e90
--- /dev/null
+++ b/bugs/filesystem-argument-checks/repro.json
@@ -0,0 +1,17 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.CurDir_ZeroLength_ReturnsCurrent$",
+      "^PASS RegressionTests\\.FileLen_File_Returns10$",
+      "^PASS RegressionTests\\.Width_255_Accepted$",
+      "^FAIL RegressionTests\\.CurDir_Null_Raises13: .*Actual: 94 ",
+      "^FAIL RegressionTests\\.Dir_Null_Raises13: .*Actual: 94 ",
+      "^FAIL RegressionTests\\.FileLen_Wildcard_Raises52: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.FileDateTime_Wildcard_Raises52: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Width_Negative_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Input_ZeroCharacters_ReturnsEmpty: .*Actual: -2147467259 "
+    ]
+  }
+}
diff --git a/bugs/filesystem-argument-checks/src/Settings b/bugs/filesystem-argument-checks/src/Settings
new file mode 100644
index 000000000..44074ead8
--- /dev/null
+++ b/bugs/filesystem-argument-checks/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "FilesystemArgumentChecks",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: CurDir, Dir, FileDateTime, FileLen, Input and Width check their arguments differently from VB6",
+	"project.exportPathIsV2": true,
+	"project.id": "{C210C4B0-5202-40B2-BE73-55BF1D864974}",
+	"project.name": "FilesystemArgumentChecks",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/filesystem-argument-checks/src/Sources/RegressionTests.twin b/bugs/filesystem-argument-checks/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..b48459dc5
--- /dev/null
+++ b/bugs/filesystem-argument-checks/src/Sources/RegressionTests.twin
@@ -0,0 +1,276 @@
+' Regression tests: CurDir, Dir, FileDateTime, FileLen, Input and Width check their arguments
+' as VB6 and 64-bit VBA do: 13 for a Null drive or path, 52 for a wildcard where a file name is
+' expected, 5 for a negative width, and no error for Input of 0 characters.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+    ' folder of its own under the temporary folder, made the current directory and filled with
+    ' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+    ' the folder full holding f.txt, and the folder is deleted after it.
+    ' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+    ' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+    ' process id under the temporary folder (the four runtimes run at once), fills it with the
+    ' fixtures below and makes it the current directory, so that a case names its files relatively
+    ' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+    ' and deletes the folder with everything in it, read-only, hidden and system files included.
+    ' The error the case raised is kept: files_End raises it again, with its description.
+    '
+    ' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+    ' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+    '
+    ' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+    ' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+    ' The folder and the files are made with Windows' own calls, never with a statement under test,
+    ' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+    ' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+    '
+    ' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+    ' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+    ' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+    ' compiles only the #Else branch.
+
+    #If VBA7 Then
+    Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+    Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+    Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+    Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+    Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+    #Else
+    Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+    Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+    Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+    Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+    Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+    Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+    #End If
+
+    ' The current directory before the case, put back by files_End.
+    Private files_Saved As String
+
+    Private Function files_Name() As String
+        files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+    End Function
+
+    ' The case's folder: the temporary folder's path, with no backslash at its end.
+    Private Function files_Dir() As String
+        Dim B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetTempPath(1024, StrPtr(B))
+        B = Left$(B, N)
+        If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+        files_Dir = B & "\" & files_Name()
+    End Function
+
+    Private Function files_Attr(ByVal Path As String) As Long
+        files_Attr = files_GetFileAttributes(StrPtr(Path))
+    End Function
+
+    Private Sub files_Expect(ByVal Cond As Boolean)
+        If Err.Number <> 0 Then Exit Sub
+        If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+    End Sub
+
+    ' A drive letter that no drive has, from Z down.
+    Private Function files_NoDrive() As String
+        Dim Mask As Long, I As Long
+        Mask = files_GetLogicalDrives()
+        For I = 25 To 3 Step -1
+            If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+        Next
+    End Function
+
+    ' Deletes Path and everything in it, whatever their attributes.
+    Private Sub files_DeleteTree(ByVal Path As String)
+        Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+        Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+        ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+        Pattern = Path & "\*"
+        H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+        If H <> -1 Then
+            Do
+                Nm = String$(260, vbNullChar)
+                files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+                N = InStr(Nm, vbNullChar)
+                If N > 0 Then Nm = Left$(Nm, N - 1)
+                files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+                If Nm <> "." And Nm <> ".." Then
+                    If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                    Names(Count) = Nm
+                    Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                    Count = Count + 1
+                End If
+            Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+            files_FindClose H
+        End If
+        For I = 0 To Count - 1
+            Nm = Path & "\" & Names(I)
+            files_SetFileAttributes StrPtr(Nm), 128
+            If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+        Next
+        files_SetFileAttributes StrPtr(Path), 128
+        files_RemoveDirectory StrPtr(Path)
+    End Sub
+
+    ' Closes every file, puts the current directory back and deletes the folder.
+    Private Sub files_Clear()
+        Dim D As String
+        Close
+        If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+        D = files_Dir()
+        If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+        If files_Attr(D) <> -1 Then files_DeleteTree D
+    End Sub
+
+    Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+        Dim F As Integer
+        F = FreeFile
+        Open Path For Output As #F
+        Print #F, Contents;
+        Close #F
+        If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+    End Sub
+
+    Private Sub files_Begin()
+        Dim D As String, B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetCurrentDirectory(1024, StrPtr(B))
+        files_Saved = Left$(B, N)
+        files_Clear
+        D = files_Dir()
+        If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+        If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+        files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+        files_Make D & "\empty.txt", "", 0
+        files_Make D & "\ro.txt", "x", 1
+        files_Make D & "\hid.txt", "x", 2
+        files_CreateDirectory StrPtr(D & "\sub"), 0
+        files_CreateDirectory StrPtr(D & "\full"), 0
+        files_Make D & "\full\f.txt", "x", 0
+    End Sub
+
+    Private Sub files_End()
+        Dim N As Long, D As String
+        N = Err.Number: D = Err.Description
+        files_Clear
+        If N <> 0 Then Err.Raise N, , D
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub CurDir_ZeroLength_ReturnsCurrent()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = CurDir("")
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub FileLen_File_Returns10()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileLen("a.txt")
+        Holds = V = 10
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Width_255_Accepted()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "b.txt" For Output As #1
+        Width #1, 255
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub CurDir_Null_Raises13()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = CurDir(Null)
+        files_End
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Dir_Null_Raises13()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = Dir(Null)
+        files_End
+        Assert.Strict.AreEqual 13&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileLen_Wildcard_Raises52()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileLen("*.txt")
+        files_End
+        Assert.Strict.AreEqual 52&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub FileDateTime_Wildcard_Raises52()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        V = FileDateTime("e*")
+        files_End
+        Assert.Strict.AreEqual 52&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Width_Negative_Raises5()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "b.txt" For Output As #1
+        Width #1, -1
+        files_End
+        Assert.Strict.AreEqual 5&, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub Input_ZeroCharacters_ReturnsEmpty()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Open "a.txt" For Input As #1
+        V = Input(0, #1)
+        Holds = V = ""
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
diff --git a/bugs/filesystem-argument-checks/src/Sources/Startup.twin b/bugs/filesystem-argument-checks/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/filesystem-argument-checks/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/filesystem-argument-checks/vb6/Module1.bas b/bugs/filesystem-argument-checks/vb6/Module1.bas
new file mode 100644
index 000000000..0e35f39e5
--- /dev/null
+++ b/bugs/filesystem-argument-checks/vb6/Module1.bas
@@ -0,0 +1,258 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/filesystem-argument-checks: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises and, where the case checks it, whether the file
+' is as the case expects. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 filesystem-argument-checks
+' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+' folder of its own under the temporary folder, made the current directory and filled with
+' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+' the folder full holding f.txt, and the folder is deleted after it.
+' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+' process id under the temporary folder (the four runtimes run at once), fills it with the
+' fixtures below and makes it the current directory, so that a case names its files relatively
+' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+' and deletes the folder with everything in it, read-only, hidden and system files included.
+' The error the case raised is kept: files_End raises it again, with its description.
+'
+' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+'
+' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+' The folder and the files are made with Windows' own calls, never with a statement under test,
+' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+'
+' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+' compiles only the #Else branch.
+
+#If VBA7 Then
+Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+#Else
+Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+#End If
+
+' The current directory before the case, put back by files_End.
+Private files_Saved As String
+
+Private Function files_Name() As String
+    files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+End Function
+
+' The case's folder: the temporary folder's path, with no backslash at its end.
+Private Function files_Dir() As String
+    Dim B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetTempPath(1024, StrPtr(B))
+    B = Left$(B, N)
+    If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+    files_Dir = B & "\" & files_Name()
+End Function
+
+Private Function files_Attr(ByVal Path As String) As Long
+    files_Attr = files_GetFileAttributes(StrPtr(Path))
+End Function
+
+Private Sub files_Expect(ByVal Cond As Boolean)
+    If Err.Number <> 0 Then Exit Sub
+    If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+End Sub
+
+' A drive letter that no drive has, from Z down.
+Private Function files_NoDrive() As String
+    Dim Mask As Long, I As Long
+    Mask = files_GetLogicalDrives()
+    For I = 25 To 3 Step -1
+        If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+    Next
+End Function
+
+' Deletes Path and everything in it, whatever their attributes.
+Private Sub files_DeleteTree(ByVal Path As String)
+    Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+    Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+    ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+    Pattern = Path & "\*"
+    H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+    If H <> -1 Then
+        Do
+            Nm = String$(260, vbNullChar)
+            files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+            N = InStr(Nm, vbNullChar)
+            If N > 0 Then Nm = Left$(Nm, N - 1)
+            files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+            If Nm <> "." And Nm <> ".." Then
+                If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                Names(Count) = Nm
+                Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                Count = Count + 1
+            End If
+        Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+        files_FindClose H
+    End If
+    For I = 0 To Count - 1
+        Nm = Path & "\" & Names(I)
+        files_SetFileAttributes StrPtr(Nm), 128
+        If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+    Next
+    files_SetFileAttributes StrPtr(Path), 128
+    files_RemoveDirectory StrPtr(Path)
+End Sub
+
+' Closes every file, puts the current directory back and deletes the folder.
+Private Sub files_Clear()
+    Dim D As String
+    Close
+    If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+    D = files_Dir()
+    If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+    If files_Attr(D) <> -1 Then files_DeleteTree D
+End Sub
+
+Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+    Dim F As Integer
+    F = FreeFile
+    Open Path For Output As #F
+    Print #F, Contents;
+    Close #F
+    If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+End Sub
+
+Private Sub files_Begin()
+    Dim D As String, B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetCurrentDirectory(1024, StrPtr(B))
+    files_Saved = Left$(B, N)
+    files_Clear
+    D = files_Dir()
+    If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+    If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+    files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+    files_Make D & "\empty.txt", "", 0
+    files_Make D & "\ro.txt", "x", 1
+    files_Make D & "\hid.txt", "x", 2
+    files_CreateDirectory StrPtr(D & "\sub"), 0
+    files_CreateDirectory StrPtr(D & "\full"), 0
+    files_Make D & "\full\f.txt", "x", 0
+End Sub
+
+Private Sub files_End()
+    Dim N As Long, D As String
+    N = Err.Number: D = Err.Description
+    files_Clear
+    If N <> 0 Then Err.Raise N, , D
+End Sub
+
+' out.txt is opened for each line: the harness closes every file after a case.
+Private Sub Report(ByVal Label As String, ByVal Check As String)
+    Dim F As Integer
+    F = FreeFile
+    Open App.Path & "\out.txt" For Append As #F
+    Print #F, Label & ": " & Err.Number & " " & Err.Description & Check
+    Close #F
+End Sub
+
+Sub Main()
+    Dim V As Variant, Holds As Boolean
+    On Error Resume Next
+    Kill App.Path & "\out.txt"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = CurDir("")
+    files_End
+    Report "CurDir_ZeroLength_ReturnsCurrent", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = FileLen("a.txt")
+    Holds = V = 10
+    files_End
+    Report "FileLen_File_Returns10", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Open "b.txt" For Output As #1
+    Width #1, 255
+    files_End
+    Report "Width_255_Accepted", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = CurDir(Null)
+    files_End
+    Report "CurDir_Null_Raises13", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = Dir(Null)
+    files_End
+    Report "Dir_Null_Raises13", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = FileLen("*.txt")
+    files_End
+    Report "FileLen_Wildcard_Raises52", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    V = FileDateTime("e*")
+    files_End
+    Report "FileDateTime_Wildcard_Raises52", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Open "b.txt" For Output As #1
+    Width #1, -1
+    files_End
+    Report "Width_Negative_Raises5", ""
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Open "a.txt" For Input As #1
+    V = Input(0, #1)
+    Holds = V = ""
+    files_End
+    Report "Input_ZeroCharacters_ReturnsEmpty", " (check " & IIf(Holds, "holds", "fails") & ")"
+End Sub
diff --git a/bugs/filesystem-argument-checks/vb6/Probe.vbp b/bugs/filesystem-argument-checks/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/filesystem-argument-checks/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/financial-argument-checks/financial-argument-checks.twinproj b/bugs/financial-argument-checks/financial-argument-checks.twinproj
new file mode 100644
index 000000000..7497780b5
Binary files /dev/null and b/bugs/financial-argument-checks/financial-argument-checks.twinproj differ
diff --git a/bugs/financial-argument-checks/repro.json b/bugs/financial-argument-checks/repro.json
new file mode 100644
index 000000000..28e67cc90
--- /dev/null
+++ b/bugs/financial-argument-checks/repro.json
@@ -0,0 +1,27 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_IPmtLastPeriod$",
+      "^PASS RegressionTests\\.Control_PmtRateMinusTwo_Raises11$",
+      "^PASS RegressionTests\\.Control_DDBLifeOne$",
+      "^FAIL RegressionTests\\.IPmt_PerZero_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.IPmt_PerNperPlusOne_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.PPmt_PerZero_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.PPmt_PerNperPlusOne_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Pmt_NperZero_Raises5: .*Actual: 11 ",
+      "^FAIL RegressionTests\\.PPmt_NperZero_Raises5: .*Actual: 11 ",
+      "^FAIL RegressionTests\\.MIRR_OneElement_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.MIRR_ReinvestRateMinusOne_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.MIRR_NoPayment_Raises11: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.NPV_RateMinusOne_Raises5: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.DDB_LifeBelowOne_Returns900: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.FV_RateMinusOneNegativeNper_Raises6: .*Actual: 5 ",
+      "^FAIL RegressionTests\\.PV_RateMinusOneNperZero_Returns0: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.PV_RateMinusOne_Raises11: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.PV_RateMinusOneNegativeNper_Raises6: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.SLN_InfiniteResult_Raises6: .*Actual: 0 "
+    ]
+  }
+}
diff --git a/bugs/financial-argument-checks/src/Settings b/bugs/financial-argument-checks/src/Settings
new file mode 100644
index 000000000..1de334217
--- /dev/null
+++ b/bugs/financial-argument-checks/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "FinancialArgumentChecks",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Financial functions check their arguments differently from VBA",
+	"project.exportPathIsV2": true,
+	"project.id": "{7DA98539-9162-4AD1-B400-05D4CE082BFB}",
+	"project.name": "FinancialArgumentChecks",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/financial-argument-checks/src/Sources/RegressionTests.twin b/bugs/financial-argument-checks/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..f53190978
--- /dev/null
+++ b/bugs/financial-argument-checks/src/Sources/RegressionTests.twin
@@ -0,0 +1,235 @@
+' Regression tests: the Financial functions check their arguments as 64-bit VBA does: 5 for a
+' period outside 1 to nper (IPmt, PPmt), for an nper of 0 (Pmt, PPmt), for MIRR of one element
+' or a rate of -1, and for NPV at a rate of -1; 11 for MIRR with no payment; a DDB of a life
+' below 1; and with a rate of -1, FV's 6 and PV's 0, 11 and 6; SLN's 6 for an infinite result.
+' VB6 agrees but for FV (11), PV and SLN (no error, infinity). The controls pass in all.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_IPmtLastPeriod()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 10.9999999, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_PmtRateMinusTwo_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(-2, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_DDBLifeOne()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 1, 0.5)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 900) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_PerZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 0, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_PerNperPlusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 11, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_PerZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 0, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_PerNperPlusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 11, 10, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_NperZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(0.01, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_NperZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 1, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_OneElement_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(0)
+        A(0) = -100
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_ReinvestRateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = MIRR(A, 0.1, -1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_NoPayment_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = 100
+        A(1) = 110
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_RateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = NPV(-1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub DDB_LifeBelowOne_Returns900()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 0.5, 0.5)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 900) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub FV_RateMinusOneNegativeNper_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(-1, -1, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOneNperZero_Returns0()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, 0, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOne_Raises11()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, 10, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 11&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_RateMinusOneNegativeNper_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(-1, -1, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+    [TestCase]
+    Public Sub SLN_InfiniteResult_Raises6()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = SLN(1000, 100, 1E-308)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 6&, E
+    End Sub
+
+End Module
diff --git a/bugs/financial-argument-checks/src/Sources/Startup.twin b/bugs/financial-argument-checks/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/financial-argument-checks/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/financial-argument-checks/vb6/Module1.bas b/bugs/financial-argument-checks/vb6/Module1.bas
new file mode 100644
index 000000000..fe8a20608
--- /dev/null
+++ b/bugs/financial-argument-checks/vb6/Module1.bas
@@ -0,0 +1,233 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/financial-argument-checks: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises (0: none) and the value. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 financial-argument-checks
+
+Private Sub Control_IPmtLastPeriod()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = IPmt(0.01, 10.9999999, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_IPmtLastPeriod: " & E & " " & R
+End Sub
+
+Private Sub Control_PmtRateMinusTwo_Raises11()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Pmt(-2, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_PmtRateMinusTwo_Raises11: " & E & " " & R
+End Sub
+
+Private Sub Control_DDBLifeOne()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = DDB(1000, 100, 1, 0.5)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_DDBLifeOne: " & E & " " & R
+End Sub
+
+Private Sub IPmt_PerZero_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = IPmt(0.01, 0, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IPmt_PerZero_Raises5: " & E & " " & R
+End Sub
+
+Private Sub IPmt_PerNperPlusOne_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = IPmt(0.01, 11, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IPmt_PerNperPlusOne_Raises5: " & E & " " & R
+End Sub
+
+Private Sub PPmt_PerZero_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PPmt(0.01, 0, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PPmt_PerZero_Raises5: " & E & " " & R
+End Sub
+
+Private Sub PPmt_PerNperPlusOne_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PPmt(0.01, 11, 10, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PPmt_PerNperPlusOne_Raises5: " & E & " " & R
+End Sub
+
+Private Sub Pmt_NperZero_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Pmt(0.01, 0, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Pmt_NperZero_Raises5: " & E & " " & R
+End Sub
+
+Private Sub PPmt_NperZero_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PPmt(0.01, 1, 0, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PPmt_NperZero_Raises5: " & E & " " & R
+End Sub
+
+Private Sub MIRR_OneElement_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(0)
+    A(0) = -100
+    R = MIRR(A, 0.1, 0.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "MIRR_OneElement_Raises5: " & E & " " & R
+End Sub
+
+Private Sub MIRR_ReinvestRateMinusOne_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(2)
+    A(0) = -100
+    A(1) = 50
+    A(2) = 60
+    R = MIRR(A, 0.1, -1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "MIRR_ReinvestRateMinusOne_Raises5: " & E & " " & R
+End Sub
+
+Private Sub MIRR_NoPayment_Raises11()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(1)
+    A(0) = 100
+    A(1) = 110
+    R = MIRR(A, 0.1, 0.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "MIRR_NoPayment_Raises11: " & E & " " & R
+End Sub
+
+Private Sub NPV_RateMinusOne_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(2)
+    A(0) = -100
+    A(1) = 50
+    A(2) = 60
+    R = NPV(-1, A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NPV_RateMinusOne_Raises5: " & E & " " & R
+End Sub
+
+Private Sub DDB_LifeBelowOne_Returns900()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = DDB(1000, 100, 0.5, 0.5)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "DDB_LifeBelowOne_Returns900: " & E & " " & R
+End Sub
+
+Private Sub FV_RateMinusOneNegativeNper_Raises6()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(-1, -1, -100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "FV_RateMinusOneNegativeNper_Raises6: " & E & " " & R
+End Sub
+
+Private Sub PV_RateMinusOneNperZero_Returns0()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PV(-1, 0, -100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PV_RateMinusOneNperZero_Returns0: " & E & " " & R
+End Sub
+
+Private Sub PV_RateMinusOne_Raises11()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PV(-1, 10, -100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PV_RateMinusOne_Raises11: " & E & " " & R
+End Sub
+
+Private Sub PV_RateMinusOneNegativeNper_Raises6()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PV(-1, -1, -100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PV_RateMinusOneNegativeNper_Raises6: " & E & " " & R
+End Sub
+
+Private Sub SLN_InfiniteResult_Raises6()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = SLN(1000, 100, 1E-308)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "SLN_InfiniteResult_Raises6: " & E & " " & R
+End Sub
+
+Sub Main()
+    Open App.Path & "\out.txt" For Output As #9
+    Control_IPmtLastPeriod
+    Control_PmtRateMinusTwo_Raises11
+    Control_DDBLifeOne
+    IPmt_PerZero_Raises5
+    IPmt_PerNperPlusOne_Raises5
+    PPmt_PerZero_Raises5
+    PPmt_PerNperPlusOne_Raises5
+    Pmt_NperZero_Raises5
+    PPmt_NperZero_Raises5
+    MIRR_OneElement_Raises5
+    MIRR_ReinvestRateMinusOne_Raises5
+    MIRR_NoPayment_Raises11
+    NPV_RateMinusOne_Raises5
+    DDB_LifeBelowOne_Returns900
+    FV_RateMinusOneNegativeNper_Raises6
+    PV_RateMinusOneNperZero_Returns0
+    PV_RateMinusOne_Raises11
+    PV_RateMinusOneNegativeNper_Raises6
+    SLN_InfiniteResult_Raises6
+    Close #9
+End Sub
diff --git a/bugs/financial-argument-checks/vb6/Probe.vbp b/bugs/financial-argument-checks/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/financial-argument-checks/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/financial-array-arguments/financial-array-arguments.twinproj b/bugs/financial-array-arguments/financial-array-arguments.twinproj
new file mode 100644
index 000000000..7fb905d2c
Binary files /dev/null and b/bugs/financial-array-arguments/financial-array-arguments.twinproj differ
diff --git a/bugs/financial-array-arguments/repro.json b/bugs/financial-array-arguments/repro.json
new file mode 100644
index 000000000..afdb682b4
--- /dev/null
+++ b/bugs/financial-array-arguments/repro.json
@@ -0,0 +1,18 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_IRR$",
+      "^PASS RegressionTests\\.Control_MIRR$",
+      "^PASS RegressionTests\\.Control_NPV$",
+      "^FAIL RegressionTests\\.IRR_Unsized_Raises5: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests\\.IRR_Erased_Raises5: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests\\.MIRR_Unsized_Raises5: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests\\.NPV_Unsized_Raises5: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests\\.IRR_TwoDimensions_Raises5: .*Actual: -2147418113 ",
+      "^FAIL RegressionTests\\.MIRR_TwoDimensions_Raises5: .*Actual: -2147418113 ",
+      "^FAIL RegressionTests\\.NPV_TwoDimensions_Raises5: .*Actual: -2147418113 "
+    ]
+  }
+}
diff --git a/bugs/financial-array-arguments/src/Settings b/bugs/financial-array-arguments/src/Settings
new file mode 100644
index 000000000..4255ad535
--- /dev/null
+++ b/bugs/financial-array-arguments/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "FinancialArrayArguments",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: IRR, MIRR and NPV crash on an unsized array",
+	"project.exportPathIsV2": true,
+	"project.id": "{86D08E5C-C491-4A84-9F55-22B80C4E9600}",
+	"project.name": "FinancialArrayArguments",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/financial-array-arguments/src/Sources/RegressionTests.twin b/bugs/financial-array-arguments/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..c2191d6e9
--- /dev/null
+++ b/bugs/financial-array-arguments/src/Sources/RegressionTests.twin
@@ -0,0 +1,149 @@
+' Regression tests: IRR, MIRR and NPV raise 5, Invalid procedure call or argument, for an
+' array that has never been sized or has been erased, and for one of two dimensions, as VB6
+' and 64-bit VBA do. On BETA 1010 the unsized cases end with an access violation. The
+' controls are each function of a sized one-dimensional array.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_IRR()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = -100
+        A(1) = 110
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_MIRR()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0723805294763609) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_NPV()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(2)
+        A(0) = -100
+        A(1) = 50
+        A(2) = 60
+        R = NPV(0.1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - -4.50788880540947) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_Erased_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        ReDim A(1)
+        A(0) = -100
+        A(1) = 110
+        Erase A
+        R = IRR(A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = MIRR(A, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_Unsized_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPV(0.1, A)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IRR_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = IRR(B)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub MIRR_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = MIRR(B, 0.1, 0.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPV_TwoDimensions_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        B(0, 0) = -100
+        B(1, 0) = 110
+        B(0, 1) = -100
+        B(1, 1) = 110
+        R = NPV(0.1, B)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+End Module
diff --git a/bugs/financial-array-arguments/src/Sources/Startup.twin b/bugs/financial-array-arguments/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/financial-array-arguments/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/financial-array-arguments/vb6/Module1.bas b/bugs/financial-array-arguments/vb6/Module1.bas
new file mode 100644
index 000000000..9e93935cb
--- /dev/null
+++ b/bugs/financial-array-arguments/vb6/Module1.bas
@@ -0,0 +1,148 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/financial-array-arguments: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises (0: none) and the value. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 financial-array-arguments
+
+Private Sub Control_IRR()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(1)
+    A(0) = -100
+    A(1) = 110
+    R = IRR(A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_IRR: " & E & " " & R
+End Sub
+
+Private Sub Control_MIRR()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(2)
+    A(0) = -100
+    A(1) = 50
+    A(2) = 60
+    R = MIRR(A, 0.1, 0.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_MIRR: " & E & " " & R
+End Sub
+
+Private Sub Control_NPV()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(2)
+    A(0) = -100
+    A(1) = 50
+    A(2) = 60
+    R = NPV(0.1, A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_NPV: " & E & " " & R
+End Sub
+
+Private Sub IRR_Unsized_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = IRR(A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IRR_Unsized_Raises5: " & E & " " & R
+End Sub
+
+Private Sub IRR_Erased_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    ReDim A(1)
+    A(0) = -100
+    A(1) = 110
+    Erase A
+    R = IRR(A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IRR_Erased_Raises5: " & E & " " & R
+End Sub
+
+Private Sub MIRR_Unsized_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = MIRR(A, 0.1, 0.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "MIRR_Unsized_Raises5: " & E & " " & R
+End Sub
+
+Private Sub NPV_Unsized_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPV(0.1, A)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NPV_Unsized_Raises5: " & E & " " & R
+End Sub
+
+Private Sub IRR_TwoDimensions_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    B(0, 0) = -100
+    B(1, 0) = 110
+    B(0, 1) = -100
+    B(1, 1) = 110
+    R = IRR(B)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IRR_TwoDimensions_Raises5: " & E & " " & R
+End Sub
+
+Private Sub MIRR_TwoDimensions_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    B(0, 0) = -100
+    B(1, 0) = 110
+    B(0, 1) = -100
+    B(1, 1) = 110
+    R = MIRR(B, 0.1, 0.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "MIRR_TwoDimensions_Raises5: " & E & " " & R
+End Sub
+
+Private Sub NPV_TwoDimensions_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    B(0, 0) = -100
+    B(1, 0) = 110
+    B(0, 1) = -100
+    B(1, 1) = 110
+    R = NPV(0.1, B)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NPV_TwoDimensions_Raises5: " & E & " " & R
+End Sub
+
+Sub Main()
+    Open App.Path & "\out.txt" For Output As #9
+    Control_IRR
+    Control_MIRR
+    Control_NPV
+    IRR_Unsized_Raises5
+    IRR_Erased_Raises5
+    MIRR_Unsized_Raises5
+    NPV_Unsized_Raises5
+    IRR_TwoDimensions_Raises5
+    MIRR_TwoDimensions_Raises5
+    NPV_TwoDimensions_Raises5
+    Close #9
+End Sub
diff --git a/bugs/financial-array-arguments/vb6/Probe.vbp b/bugs/financial-array-arguments/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/financial-array-arguments/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/financial-null-optional-argument/financial-null-optional-argument.twinproj b/bugs/financial-null-optional-argument/financial-null-optional-argument.twinproj
new file mode 100644
index 000000000..88334dbc4
Binary files /dev/null and b/bugs/financial-null-optional-argument/financial-null-optional-argument.twinproj differ
diff --git a/bugs/financial-null-optional-argument/repro.json b/bugs/financial-null-optional-argument/repro.json
new file mode 100644
index 000000000..14522a34e
--- /dev/null
+++ b/bugs/financial-null-optional-argument/repro.json
@@ -0,0 +1,20 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_RequiredNull_Raises94$",
+      "^PASS RegressionTests\\.Control_OptionalString_Raises13$",
+      "^PASS RegressionTests\\.Control_OptionalNumber$",
+      "^FAIL RegressionTests\\.FV_PvNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.FV_TypeNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.PV_FvNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.Pmt_FvNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.NPer_TypeNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.IPmt_FvNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.PPmt_TypeNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.Rate_TypeNull_Raises94: .*Actual: 13 ",
+      "^FAIL RegressionTests\\.DDB_FactorNull_Raises94: .*Actual: 13 "
+    ]
+  }
+}
diff --git a/bugs/financial-null-optional-argument/src/Settings b/bugs/financial-null-optional-argument/src/Settings
new file mode 100644
index 000000000..03c604782
--- /dev/null
+++ b/bugs/financial-null-optional-argument/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "FinancialNullOptionalArgument",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Null in an optional argument of a Financial function raises 13",
+	"project.exportPathIsV2": true,
+	"project.id": "{75A44D06-9732-4D04-9414-C62947EEAEFA}",
+	"project.name": "FinancialNullOptionalArgument",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/financial-null-optional-argument/src/Sources/RegressionTests.twin b/bugs/financial-null-optional-argument/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..29936c05c
--- /dev/null
+++ b/bugs/financial-null-optional-argument/src/Sources/RegressionTests.twin
@@ -0,0 +1,140 @@
+' Regression tests: a Null optional argument of a Financial function (pv, fv, type, factor)
+' raises 94, Invalid use of Null, as VB6 and 64-bit VBA do. The controls are a Null required
+' argument (94), a string that is not a number (13) and a number in the optional argument.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_RequiredNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(Null, 10, -100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_OptionalString_Raises13()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, "abc")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_OptionalNumber()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub FV_PvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub FV_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = FV(0.01, 10, -100, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PV_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PV(0.01, 10, -100, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Pmt_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Pmt(0.01, 10, 1000, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub NPer_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, -1000, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub IPmt_FvNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = IPmt(0.01, 1, 10, 1000, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PPmt_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = PPmt(0.01, 1, 10, 1000, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub Rate_TypeNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub DDB_FactorNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = DDB(1000, 100, 5, 1, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+End Module
diff --git a/bugs/financial-null-optional-argument/src/Sources/Startup.twin b/bugs/financial-null-optional-argument/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/financial-null-optional-argument/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/financial-null-optional-argument/vb6/Module1.bas b/bugs/financial-null-optional-argument/vb6/Module1.bas
new file mode 100644
index 000000000..721cccb0a
--- /dev/null
+++ b/bugs/financial-null-optional-argument/vb6/Module1.bas
@@ -0,0 +1,143 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/financial-null-optional-argument: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises (0: none) and the value. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 financial-null-optional-argument
+
+Private Sub Control_RequiredNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(Null, 10, -100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_RequiredNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub Control_OptionalString_Raises13()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(0.01, 10, -100, "abc")
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_OptionalString_Raises13: " & E & " " & R
+End Sub
+
+Private Sub Control_OptionalNumber()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(0.01, 10, -100, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_OptionalNumber: " & E & " " & R
+End Sub
+
+Private Sub FV_PvNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(0.01, 10, -100, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "FV_PvNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub FV_TypeNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = FV(0.01, 10, -100, 0, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "FV_TypeNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub PV_FvNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PV(0.01, 10, -100, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PV_FvNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub Pmt_FvNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Pmt(0.01, 10, 1000, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Pmt_FvNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub NPer_TypeNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, 100, -1000, 0, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NPer_TypeNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub IPmt_FvNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = IPmt(0.01, 1, 10, 1000, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "IPmt_FvNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub PPmt_TypeNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = PPmt(0.01, 1, 10, 1000, 0, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PPmt_TypeNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub Rate_TypeNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(1, 0, 100, -110, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Rate_TypeNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub DDB_FactorNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = DDB(1000, 100, 5, 1, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "DDB_FactorNull_Raises94: " & E & " " & R
+End Sub
+
+Sub Main()
+    Open App.Path & "\out.txt" For Output As #9
+    Control_RequiredNull_Raises94
+    Control_OptionalString_Raises13
+    Control_OptionalNumber
+    FV_PvNull_Raises94
+    FV_TypeNull_Raises94
+    PV_FvNull_Raises94
+    Pmt_FvNull_Raises94
+    NPer_TypeNull_Raises94
+    IPmt_FvNull_Raises94
+    PPmt_TypeNull_Raises94
+    Rate_TypeNull_Raises94
+    DDB_FactorNull_Raises94
+    Close #9
+End Sub
diff --git a/bugs/financial-null-optional-argument/vb6/Probe.vbp b/bugs/financial-null-optional-argument/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/financial-null-optional-argument/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/kill-hidden-system-files/kill-hidden-system-files.twinproj b/bugs/kill-hidden-system-files/kill-hidden-system-files.twinproj
new file mode 100644
index 000000000..b0a304cc0
Binary files /dev/null and b/bugs/kill-hidden-system-files/kill-hidden-system-files.twinproj differ
diff --git a/bugs/kill-hidden-system-files/repro.json b/bugs/kill-hidden-system-files/repro.json
new file mode 100644
index 000000000..c9013e1ae
--- /dev/null
+++ b/bugs/kill-hidden-system-files/repro.json
@@ -0,0 +1,15 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Kill_NormalFile_Deletes$",
+      "^PASS RegressionTests\\.Kill_ReadOnlyFile_RaisesAndKeepsIt$",
+      "^FAIL RegressionTests\\.Kill_HiddenFile_Raises53: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Kill_SystemFile_Raises53: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Kill_HiddenSystemFile_Raises53: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Kill_WildcardMatchingOnlyAHiddenFile_Raises53: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.Kill_Wildcard_LeavesHiddenFile: .*Actual: False\\. "
+    ]
+  }
+}
diff --git a/bugs/kill-hidden-system-files/src/Settings b/bugs/kill-hidden-system-files/src/Settings
new file mode 100644
index 000000000..48f37b710
--- /dev/null
+++ b/bugs/kill-hidden-system-files/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "KillHiddenSystemFiles",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Kill deletes hidden and system files, where VB6 raises error 53",
+	"project.exportPathIsV2": true,
+	"project.id": "{DA4C700B-1B08-4ABB-9C62-DD9ACE9E64B9}",
+	"project.name": "KillHiddenSystemFiles",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/kill-hidden-system-files/src/Sources/RegressionTests.twin b/bugs/kill-hidden-system-files/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..e2915aee0
--- /dev/null
+++ b/bugs/kill-hidden-system-files/src/Sources/RegressionTests.twin
@@ -0,0 +1,264 @@
+' Regression tests: Kill refuses a hidden or a system file with error 53, as VB6 and 64-bit VBA
+' do, and a wildcard skips such files, where twinBASIC deletes them.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+    ' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+    ' folder of its own under the temporary folder, made the current directory and filled with
+    ' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+    ' the folder full holding f.txt, and the folder is deleted after it.
+    ' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+    ' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+    ' process id under the temporary folder (the four runtimes run at once), fills it with the
+    ' fixtures below and makes it the current directory, so that a case names its files relatively
+    ' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+    ' and deletes the folder with everything in it, read-only, hidden and system files included.
+    ' The error the case raised is kept: files_End raises it again, with its description.
+    '
+    ' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+    ' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+    '
+    ' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+    ' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+    ' The folder and the files are made with Windows' own calls, never with a statement under test,
+    ' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+    ' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+    '
+    ' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+    ' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+    ' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+    ' compiles only the #Else branch.
+
+    #If VBA7 Then
+    Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+    Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+    Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+    Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+    Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+    Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+    Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+    #Else
+    Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+    Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+    Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+    Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+    Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+    Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+    Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+    Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+    Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+    Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+    Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+    #End If
+
+    ' The current directory before the case, put back by files_End.
+    Private files_Saved As String
+
+    Private Function files_Name() As String
+        files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+    End Function
+
+    ' The case's folder: the temporary folder's path, with no backslash at its end.
+    Private Function files_Dir() As String
+        Dim B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetTempPath(1024, StrPtr(B))
+        B = Left$(B, N)
+        If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+        files_Dir = B & "\" & files_Name()
+    End Function
+
+    Private Function files_Attr(ByVal Path As String) As Long
+        files_Attr = files_GetFileAttributes(StrPtr(Path))
+    End Function
+
+    Private Sub files_Expect(ByVal Cond As Boolean)
+        If Err.Number <> 0 Then Exit Sub
+        If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+    End Sub
+
+    ' A drive letter that no drive has, from Z down.
+    Private Function files_NoDrive() As String
+        Dim Mask As Long, I As Long
+        Mask = files_GetLogicalDrives()
+        For I = 25 To 3 Step -1
+            If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+        Next
+    End Function
+
+    ' Deletes Path and everything in it, whatever their attributes.
+    Private Sub files_DeleteTree(ByVal Path As String)
+        Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+        Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+        ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+        Pattern = Path & "\*"
+        H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+        If H <> -1 Then
+            Do
+                Nm = String$(260, vbNullChar)
+                files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+                N = InStr(Nm, vbNullChar)
+                If N > 0 Then Nm = Left$(Nm, N - 1)
+                files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+                If Nm <> "." And Nm <> ".." Then
+                    If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                    Names(Count) = Nm
+                    Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                    Count = Count + 1
+                End If
+            Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+            files_FindClose H
+        End If
+        For I = 0 To Count - 1
+            Nm = Path & "\" & Names(I)
+            files_SetFileAttributes StrPtr(Nm), 128
+            If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+        Next
+        files_SetFileAttributes StrPtr(Path), 128
+        files_RemoveDirectory StrPtr(Path)
+    End Sub
+
+    ' Closes every file, puts the current directory back and deletes the folder.
+    Private Sub files_Clear()
+        Dim D As String
+        Close
+        If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+        D = files_Dir()
+        If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+        If files_Attr(D) <> -1 Then files_DeleteTree D
+    End Sub
+
+    Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+        Dim F As Integer
+        F = FreeFile
+        Open Path For Output As #F
+        Print #F, Contents;
+        Close #F
+        If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+    End Sub
+
+    Private Sub files_Begin()
+        Dim D As String, B As String, N As Long
+        B = String$(1024, vbNullChar)
+        N = files_GetCurrentDirectory(1024, StrPtr(B))
+        files_Saved = Left$(B, N)
+        files_Clear
+        D = files_Dir()
+        If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+        If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+        files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+        files_Make D & "\empty.txt", "", 0
+        files_Make D & "\ro.txt", "x", 1
+        files_Make D & "\hid.txt", "x", 2
+        files_CreateDirectory StrPtr(D & "\sub"), 0
+        files_CreateDirectory StrPtr(D & "\full"), 0
+        files_Make D & "\full\f.txt", "x", 0
+    End Sub
+
+    Private Sub files_End()
+        Dim N As Long, D As String
+        N = Err.Number: D = Err.Description
+        files_Clear
+        If N <> 0 Then Err.Raise N, , D
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Kill_NormalFile_Deletes()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") = -1
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    ' A control: twinBASIC already does this.
+    [TestCase]
+    Public Sub Kill_ReadOnlyFile_RaisesAndKeepsIt()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "ro.txt"
+        Holds = files_Attr("ro.txt") <> -1
+        files_End
+        Assert.Strict.AreNotEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_HiddenFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "hid.txt"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_SystemFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "a.txt", vbSystem
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_HiddenSystemFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "a.txt", vbHidden + vbSystem
+        Kill "a.txt"
+        Holds = files_Attr("a.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_WildcardMatchingOnlyAHiddenFile_Raises53()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        Kill "h*"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 53&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+    [TestCase]
+    Public Sub Kill_Wildcard_LeavesHiddenFile()
+        Dim V As Variant, Holds As Boolean
+        On Error Resume Next
+        files_Begin
+        SetAttr "ro.txt", vbNormal
+        Kill "*.txt"
+        Holds = files_Attr("hid.txt") <> -1
+        files_End
+        Assert.Strict.AreEqual 0&, Err.Number
+        Assert.Strict.IsTrue Holds
+    End Sub
+
+End Module
diff --git a/bugs/kill-hidden-system-files/src/Sources/Startup.twin b/bugs/kill-hidden-system-files/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/kill-hidden-system-files/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/kill-hidden-system-files/vb6/Module1.bas b/bugs/kill-hidden-system-files/vb6/Module1.bas
new file mode 100644
index 000000000..1aeaf4b58
--- /dev/null
+++ b/bugs/kill-hidden-system-files/vb6/Module1.bas
@@ -0,0 +1,249 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/kill-hidden-system-files: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises and, where the case checks it, whether the file
+' is as the case expects. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 kill-hidden-system-files
+' ---- a copy of errors/harnesses/files.bas (twinBASIC documentation): each case runs in a
+' folder of its own under the temporary folder, made the current directory and filled with
+' a.txt (10 bytes), empty.txt, ro.txt (read-only), hid.txt (hidden), the empty folder sub and
+' the folder full holding f.txt, and the folder is deleted after it.
+' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+' process id under the temporary folder (the four runtimes run at once), fills it with the
+' fixtures below and makes it the current directory, so that a case names its files relatively
+' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+' and deletes the folder with everything in it, read-only, hidden and system files included.
+' The error the case raised is kept: files_End raises it again, with its description.
+'
+' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+'
+' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+' The folder and the files are made with Windows' own calls, never with a statement under test,
+' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+'
+' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+' compiles only the #Else branch.
+
+#If VBA7 Then
+Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+#Else
+Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+#End If
+
+' The current directory before the case, put back by files_End.
+Private files_Saved As String
+
+Private Function files_Name() As String
+    files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+End Function
+
+' The case's folder: the temporary folder's path, with no backslash at its end.
+Private Function files_Dir() As String
+    Dim B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetTempPath(1024, StrPtr(B))
+    B = Left$(B, N)
+    If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+    files_Dir = B & "\" & files_Name()
+End Function
+
+Private Function files_Attr(ByVal Path As String) As Long
+    files_Attr = files_GetFileAttributes(StrPtr(Path))
+End Function
+
+Private Sub files_Expect(ByVal Cond As Boolean)
+    If Err.Number <> 0 Then Exit Sub
+    If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+End Sub
+
+' A drive letter that no drive has, from Z down.
+Private Function files_NoDrive() As String
+    Dim Mask As Long, I As Long
+    Mask = files_GetLogicalDrives()
+    For I = 25 To 3 Step -1
+        If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+    Next
+End Function
+
+' Deletes Path and everything in it, whatever their attributes.
+Private Sub files_DeleteTree(ByVal Path As String)
+    Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+    Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+    ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+    Pattern = Path & "\*"
+    H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+    If H <> -1 Then
+        Do
+            Nm = String$(260, vbNullChar)
+            files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+            N = InStr(Nm, vbNullChar)
+            If N > 0 Then Nm = Left$(Nm, N - 1)
+            files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+            If Nm <> "." And Nm <> ".." Then
+                If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                Names(Count) = Nm
+                Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                Count = Count + 1
+            End If
+        Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+        files_FindClose H
+    End If
+    For I = 0 To Count - 1
+        Nm = Path & "\" & Names(I)
+        files_SetFileAttributes StrPtr(Nm), 128
+        If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+    Next
+    files_SetFileAttributes StrPtr(Path), 128
+    files_RemoveDirectory StrPtr(Path)
+End Sub
+
+' Closes every file, puts the current directory back and deletes the folder.
+Private Sub files_Clear()
+    Dim D As String
+    Close
+    If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+    D = files_Dir()
+    If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+    If files_Attr(D) <> -1 Then files_DeleteTree D
+End Sub
+
+Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+    Dim F As Integer
+    F = FreeFile
+    Open Path For Output As #F
+    Print #F, Contents;
+    Close #F
+    If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+End Sub
+
+Private Sub files_Begin()
+    Dim D As String, B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetCurrentDirectory(1024, StrPtr(B))
+    files_Saved = Left$(B, N)
+    files_Clear
+    D = files_Dir()
+    If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+    If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+    files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+    files_Make D & "\empty.txt", "", 0
+    files_Make D & "\ro.txt", "x", 1
+    files_Make D & "\hid.txt", "x", 2
+    files_CreateDirectory StrPtr(D & "\sub"), 0
+    files_CreateDirectory StrPtr(D & "\full"), 0
+    files_Make D & "\full\f.txt", "x", 0
+End Sub
+
+Private Sub files_End()
+    Dim N As Long, D As String
+    N = Err.Number: D = Err.Description
+    files_Clear
+    If N <> 0 Then Err.Raise N, , D
+End Sub
+
+' out.txt is opened for each line: the harness closes every file after a case.
+Private Sub Report(ByVal Label As String, ByVal Check As String)
+    Dim F As Integer
+    F = FreeFile
+    Open App.Path & "\out.txt" For Append As #F
+    Print #F, Label & ": " & Err.Number & " " & Err.Description & Check
+    Close #F
+End Sub
+
+Sub Main()
+    Dim V As Variant, Holds As Boolean
+    On Error Resume Next
+    Kill App.Path & "\out.txt"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Kill "a.txt"
+    Holds = files_Attr("a.txt") = -1
+    files_End
+    Report "Kill_NormalFile_Deletes", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Kill "ro.txt"
+    Holds = files_Attr("ro.txt") <> -1
+    files_End
+    Report "Kill_ReadOnlyFile_RaisesAndKeepsIt", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Kill "hid.txt"
+    Holds = files_Attr("hid.txt") <> -1
+    files_End
+    Report "Kill_HiddenFile_Raises53", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    SetAttr "a.txt", vbSystem
+    Kill "a.txt"
+    Holds = files_Attr("a.txt") <> -1
+    files_End
+    Report "Kill_SystemFile_Raises53", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    SetAttr "a.txt", vbHidden + vbSystem
+    Kill "a.txt"
+    Holds = files_Attr("a.txt") <> -1
+    files_End
+    Report "Kill_HiddenSystemFile_Raises53", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    Kill "h*"
+    Holds = files_Attr("hid.txt") <> -1
+    files_End
+    Report "Kill_WildcardMatchingOnlyAHiddenFile_Raises53", " (check " & IIf(Holds, "holds", "fails") & ")"
+
+    Err.Clear
+    V = Empty
+    files_Begin
+    SetAttr "ro.txt", vbNormal
+    Kill "*.txt"
+    Holds = files_Attr("hid.txt") <> -1
+    files_End
+    Report "Kill_Wildcard_LeavesHiddenFile", " (check " & IIf(Holds, "holds", "fails") & ")"
+End Sub
diff --git a/bugs/kill-hidden-system-files/vb6/Probe.vbp b/bugs/kill-hidden-system-files/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/kill-hidden-system-files/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/nothing-argument-crashes/nothing-argument-crashes.twinproj b/bugs/nothing-argument-crashes/nothing-argument-crashes.twinproj
new file mode 100644
index 000000000..432383471
Binary files /dev/null and b/bugs/nothing-argument-crashes/nothing-argument-crashes.twinproj differ
diff --git a/bugs/nothing-argument-crashes/repro.json b/bugs/nothing-argument-crashes/repro.json
new file mode 100644
index 000000000..ed865b3c4
--- /dev/null
+++ b/bugs/nothing-argument-crashes/repro.json
@@ -0,0 +1,18 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_ConvertIconToBitmap_Icon$",
+      "^PASS RegressionTests.Control_ConvertIconToBitmap_NotAPicture_Raises$",
+      "^PASS RegressionTests.Control_AddCustomBinderObject_Object$",
+      "^FAIL RegressionTests.ConvertIconToBitmap_Nothing_RaisesAnError: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests.GetInheritedOwner_Nothing_DoesNotCrash: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests.GetInheritedOwner_Collection_DoesNotCrash: .*ACCESS_VIOLATION",
+      "^(PASS RegressionTests.GetInheritedOwner_Dictionary_DoesNotCrash$|FAIL RegressionTests.GetInheritedOwner_Dictionary_DoesNotCrash: .*ACCESS_VIOLATION)",
+      "^FAIL RegressionTests.AddCustomBinder_Nothing_RaisesAnError: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests.AddCustomBinderObject_Nothing_RaisesAnError: .*ACCESS_VIOLATION",
+      "^FAIL RegressionTests.RuntimeCreateGetMessageHook_LetIntoVariant_StoresTheObject: .*ACCESS_VIOLATION"
+    ]
+  }
+}
diff --git a/bugs/nothing-argument-crashes/src/Settings b/bugs/nothing-argument-crashes/src/Settings
new file mode 100644
index 000000000..5afc2b71d
--- /dev/null
+++ b/bugs/nothing-argument-crashes/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "NothingArgumentCrashes",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: ConvertIconToBitmap, GetInheritedOwner, AddCustomBinder and AddCustomBinderObject end the program for Nothing",
+	"project.exportPathIsV2": true,
+	"project.id": "{84FE9FCF-2C0B-46AA-ABE3-F5519D7DAE26}",
+	"project.name": "NothingArgumentCrashes",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/nothing-argument-crashes/src/Sources/RegressionTests.twin b/bugs/nothing-argument-crashes/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..c11cc7a56
--- /dev/null
+++ b/bugs/nothing-argument-crashes/src/Sources/RegressionTests.twin
@@ -0,0 +1,106 @@
+' Regression tests: given Nothing, or an object they cannot use, ConvertIconToBitmap,
+' GetInheritedOwner, TbExpressionService.AddCustomBinder and AddCustomBinderObject raise a
+' run-time error (or, for GetInheritedOwner, return Nothing) instead of ending the program
+' with an access violation; and the object RuntimeCreateGetMessageHook returns can be
+' assigned to a Variant without Set, as any other object without IDispatch can. On BETA 1010
+' each case but the controls ends with an access violation, 32-bit and 64-bit.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Declare PtrSafe Function LoadIconW Lib "user32" (ByVal Inst As LongPtr, ByVal Name As LongPtr) As LongPtr
+
+    ' The controls: each procedure working, or refusing an argument with an error.
+    [TestCase]
+    Public Sub Control_ConvertIconToBitmap_Icon()
+        Dim Icon As StdPicture = CreateStdPictureFromHandle(LoadIconW(0, 32512), vbPicTypeIcon, False)
+        Assert.Strict.AreEqual CLng(vbPicTypeBitmap), CLng(ConvertIconToBitmap(Icon).Type)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_ConvertIconToBitmap_NotAPicture_Raises()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = ConvertIconToBitmap(New Collection)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual -2147467259, E
+    End Sub
+
+    [TestCase]
+    Public Sub Control_AddCustomBinderObject_Object()
+        Dim S As New TbExpressionService
+        S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary")
+        Assert.Strict.AreEqual 0, CInt(S.Compile("D.Count").Evaluate())
+    End Sub
+
+    [TestCase]
+    Public Sub ConvertIconToBitmap_Nothing_RaisesAnError()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = ConvertIconToBitmap(Nothing)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Nothing_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(Nothing)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Collection_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(New Collection)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub GetInheritedOwner_Dictionary_DoesNotCrash()
+        Dim E As Long, R As Object
+        On Error Resume Next
+        Set R = GetInheritedOwner(CreateObject("Scripting.Dictionary"))
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.IsTrue E <> 0 Or R Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub AddCustomBinder_Nothing_RaisesAnError()
+        Dim S As New TbExpressionService
+        Dim E As Long
+        On Error Resume Next
+        S.AddCustomBinder Nothing
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub AddCustomBinderObject_Nothing_RaisesAnError()
+        Dim S As New TbExpressionService
+        Dim E As Long
+        On Error Resume Next
+        S.AddCustomBinderObject "D", Nothing
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreNotEqual 0&, E
+    End Sub
+
+    [TestCase]
+    Public Sub RuntimeCreateGetMessageHook_LetIntoVariant_StoresTheObject()
+        Dim V As Variant
+        V = RuntimeCreateGetMessageHook()
+        Assert.Strict.AreEqual CInt(vbDataObject), VarType(V)
+    End Sub
+
+End Module
diff --git a/bugs/nothing-argument-crashes/src/Sources/Startup.twin b/bugs/nothing-argument-crashes/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/nothing-argument-crashes/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/nothing-let-compiles/nothing-let-compiles.twinproj b/bugs/nothing-let-compiles/nothing-let-compiles.twinproj
new file mode 100644
index 000000000..b53996158
Binary files /dev/null and b/bugs/nothing-let-compiles/nothing-let-compiles.twinproj differ
diff --git a/bugs/nothing-let-compiles/repro.json b/bugs/nothing-let-compiles/repro.json
new file mode 100644
index 000000000..5a4fb5cdf
--- /dev/null
+++ b/bugs/nothing-let-compiles/repro.json
@@ -0,0 +1,16 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS Control_SetObject$",
+      "^PASS Control_IsNothing$",
+      "^PASS Control_SetVariant$",
+      "^FAIL LetLong_Nothing: ",
+      "^FAIL LetString_Nothing: ",
+      "^FAIL LetBoolean_Nothing: ",
+      "^FAIL EqualsComparison_Nothing: ",
+      "^FAIL NotEqualsComparison_Nothing: "
+    ]
+  }
+}
diff --git a/bugs/nothing-let-compiles/src/Settings b/bugs/nothing-let-compiles/src/Settings
new file mode 100644
index 000000000..b7831679a
--- /dev/null
+++ b/bugs/nothing-let-compiles/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "NothingLetCompiles",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Assigning or comparing Nothing without Set compiles, where VB6 refuses it",
+	"project.exportPathIsV2": true,
+	"project.id": "{0FEA5339-517A-4165-85F7-2609C2BC710A}",
+	"project.name": "NothingLetCompiles",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/nothing-let-compiles/src/Sources/RegressionTests.twin b/bugs/nothing-let-compiles/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..aaedac20f
--- /dev/null
+++ b/bugs/nothing-let-compiles/src/Sources/RegressionTests.twin
@@ -0,0 +1,23 @@
+' Regression tests for the report, as compile cases: each line that ends in a comment
+'  ' CASE <Name>: <expected>  must give that diagnostic on that line (a code, "error" for any
+' error, or "none"). tbrun --tests checks them.
+' Nothing is an object reference, assigned with Set and compared with Is. VB6 refuses, when it
+' compiles, a Let of Nothing to a variable that is not an object or a Variant, and Nothing as an
+' operand of =, with "Invalid use of object". On BETA 1010 each compiles, and raises 91 when it
+' runs. The controls are the forms VB6 compiles too.
+
+Module NothingLetTests
+
+    Private Sub Uses()
+        Dim Count As Long, Text As String, Flag As Boolean, Items As Collection, Value As Variant, Obj As Object
+        Count = Nothing  ' CASE LetLong_Nothing: error
+        Text = Nothing  ' CASE LetString_Nothing: error
+        Flag = Nothing  ' CASE LetBoolean_Nothing: error
+        If Obj = Nothing Then Count = 1  ' CASE EqualsComparison_Nothing: error
+        Flag = (Count <> Nothing)  ' CASE NotEqualsComparison_Nothing: error
+        Set Items = Nothing  ' CASE Control_SetObject: none
+        If Items Is Nothing Then Count = 1  ' CASE Control_IsNothing: none
+        Set Value = Nothing  ' CASE Control_SetVariant: none
+    End Sub
+
+End Module
diff --git a/bugs/nothing-let-compiles/src/Sources/Startup.twin b/bugs/nothing-let-compiles/src/Sources/Startup.twin
new file mode 100644
index 000000000..20233b3a9
--- /dev/null
+++ b/bugs/nothing-let-compiles/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/nothing-let-variant-no-error/nothing-let-variant-no-error.twinproj b/bugs/nothing-let-variant-no-error/nothing-let-variant-no-error.twinproj
new file mode 100644
index 000000000..533057fe2
Binary files /dev/null and b/bugs/nothing-let-variant-no-error/nothing-let-variant-no-error.twinproj differ
diff --git a/bugs/nothing-let-variant-no-error/repro.json b/bugs/nothing-let-variant-no-error/repro.json
new file mode 100644
index 000000000..7855f1cc4
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/repro.json
@@ -0,0 +1,12 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_SetVariant_HoldsNothing$",
+      "^PASS RegressionTests.Control_LetObject_Raises91$",
+      "^FAIL RegressionTests.LetVariant_Raises91: .*Expected: 91 .*Actual: 0 ",
+      "^FAIL RegressionTests.LetVariant_LeavesItEmpty: "
+    ]
+  }
+}
diff --git a/bugs/nothing-let-variant-no-error/src/Settings b/bugs/nothing-let-variant-no-error/src/Settings
new file mode 100644
index 000000000..5b71c922f
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "NothingLetVariantNoError",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: A Variant assigned Nothing without Set holds Nothing, where VB6 raises 91",
+	"project.exportPathIsV2": true,
+	"project.id": "{B81CA640-66AA-4EF4-9B54-1CC0A8855008}",
+	"project.name": "NothingLetVariantNoError",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/nothing-let-variant-no-error/src/Sources/RegressionTests.twin b/bugs/nothing-let-variant-no-error/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..25c5d969b
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/src/Sources/RegressionTests.twin
@@ -0,0 +1,46 @@
+' Regression tests: assigning Nothing to a Variant without Set raises 91, Object variable or With
+' block variable not set, and leaves the Variant Empty, as VB6 does: it reads the assignment as
+' a Let of the default value of an object that is not there. On BETA 1010 the Variant holds
+' Nothing and no error is raised. The controls: Set stores Nothing, and a Let of Nothing to an
+' Object variable raises 91 in both.
+' The VB6 project beside this one runs the same statements.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub LetVariant_Raises91()
+        Dim Value As Variant
+        Value = 3
+        On Error Resume Next
+        Value = Nothing
+        Assert.Strict.AreEqual 91, Err.Number
+    End Sub
+
+    [TestCase]
+    Public Sub LetVariant_LeavesItEmpty()
+        Dim Value As Variant
+        Value = 3
+        On Error Resume Next
+        Value = Nothing
+        On Error GoTo 0
+        Assert.Strict.IsTrue IsEmpty(Value)
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SetVariant_HoldsNothing()
+        Dim Value As Variant
+        Value = 3
+        Set Value = Nothing
+        Assert.Strict.IsTrue Value Is Nothing
+    End Sub
+
+    [TestCase]
+    Public Sub Control_LetObject_Raises91()
+        Dim Obj As Object
+        On Error Resume Next
+        Obj = Nothing
+        Assert.Strict.AreEqual 91, Err.Number
+    End Sub
+
+End Module
diff --git a/bugs/nothing-let-variant-no-error/src/Sources/Startup.twin b/bugs/nothing-let-variant-no-error/src/Sources/Startup.twin
new file mode 100644
index 000000000..20233b3a9
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/nothing-let-variant-no-error/vb6/Module1.bas b/bugs/nothing-let-variant-no-error/vb6/Module1.bas
new file mode 100644
index 000000000..c52905355
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/vb6/Module1.bas
@@ -0,0 +1,37 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of nothing-let-variant-no-error: the statements of the twinBASIC test cases, with
+' what each gives. VB6 raises 91 for Value = Nothing and leaves Value as it was.
+' Build and run it with:  node scripts/bug_repro.mjs vb6 nothing-let-variant-no-error
+' Probe.vbp builds Probe.exe, which writes what it finds to out.txt beside the exe.
+
+Sub Main()
+    Dim Value As Variant, Obj As Object
+    On Error GoTo Fail
+    Open App.Path & "\out.txt" For Output As #9
+
+    Value = 3
+    On Error Resume Next
+    Value = Nothing
+    Print #9, "LetVariant: error " & Err.Number & ", Value " & TypeName(Value) & " " & IIf(IsObject(Value), "(object)", CStr(Value))
+    Err.Clear
+    On Error GoTo Fail
+
+    Value = 3
+    Set Value = Nothing
+    Print #9, "Control_SetVariant: Value Is Nothing " & (Value Is Nothing)
+
+    On Error Resume Next
+    Obj = Nothing
+    Print #9, "Control_LetObject: error " & Err.Number
+    Err.Clear
+    On Error GoTo Fail
+
+    Close #9
+    Exit Sub
+Fail:
+    On Error Resume Next
+    Print #9, "unhandled error " & Err.Number & ": " & Err.Description
+    Close #9
+End Sub
diff --git a/bugs/nothing-let-variant-no-error/vb6/Probe.vbp b/bugs/nothing-let-variant-no-error/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/nothing-let-variant-no-error/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/nper-opposite-signs-overflow/nper-opposite-signs-overflow.twinproj b/bugs/nper-opposite-signs-overflow/nper-opposite-signs-overflow.twinproj
new file mode 100644
index 000000000..f4e1af97c
Binary files /dev/null and b/bugs/nper-opposite-signs-overflow/nper-opposite-signs-overflow.twinproj differ
diff --git a/bugs/nper-opposite-signs-overflow/repro.json b/bugs/nper-opposite-signs-overflow/repro.json
new file mode 100644
index 000000000..d53678e94
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/repro.json
@@ -0,0 +1,20 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_PositivePmt$",
+      "^PASS RegressionTests\\.Control_RateZero$",
+      "^PASS RegressionTests\\.Control_SameSigns$",
+      "^FAIL RegressionTests\\.Loan_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.CarLoan_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.LoanWithBalance_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.LoanDueAtStart_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.SavingsPlan_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.NegativeRate_ReturnsPeriods: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.PmtBelowInterest_Raises5: .*Actual: 6 ",
+      "^FAIL RegressionTests\\.PmtZero_Raises5: .*Actual: 11 ",
+      "^FAIL RegressionTests\\.RateMinusOne_Raises5: .*Actual: 11 "
+    ]
+  }
+}
diff --git a/bugs/nper-opposite-signs-overflow/src/Settings b/bugs/nper-opposite-signs-overflow/src/Settings
new file mode 100644
index 000000000..064c8297f
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "NperOppositeSignsOverflow",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: NPer raises error 6 when rate and pmt have opposite signs",
+	"project.exportPathIsV2": true,
+	"project.id": "{78AC08DF-2B14-4C39-863D-2C0F09318214}",
+	"project.name": "NperOppositeSignsOverflow",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/nper-opposite-signs-overflow/src/Sources/RegressionTests.twin b/bugs/nper-opposite-signs-overflow/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..9d9882a2a
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/src/Sources/RegressionTests.twin
@@ -0,0 +1,149 @@
+' Regression tests: NPer returns the number of periods of a loan or a savings plan, as VB6 and
+' 64-bit VBA do, whatever the signs of rate and pmt, and raises 5 where no number of periods
+' exists. The controls have rate and pmt of the same sign, or a rate of 0.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_PositivePmt()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, -1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_RateZero()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_SameSigns()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - -9.57859403981317) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Loan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub CarLoan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.1 / 12, -500, 20000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 48.8582651211073) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub LoanWithBalance_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000, 100)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 11.5886444594232) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub LoanDueAtStart_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 1000, 0, 1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 10.4781450851168) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SavingsPlan_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -100, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 9.57859403981317) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub NegativeRate_ReturnsPeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(-0.5, 100, -1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 2.58496250072116) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtBelowInterest_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, -1, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZero_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(0.01, 0, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+    [TestCase]
+    Public Sub RateMinusOne_Raises5()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = NPer(-1, -100, 1000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 5&, E
+    End Sub
+
+End Module
diff --git a/bugs/nper-opposite-signs-overflow/src/Sources/Startup.twin b/bugs/nper-opposite-signs-overflow/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/nper-opposite-signs-overflow/vb6/Module1.bas b/bugs/nper-opposite-signs-overflow/vb6/Module1.bas
new file mode 100644
index 000000000..738f59431
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/vb6/Module1.bas
@@ -0,0 +1,143 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/nper-opposite-signs-overflow: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises (0: none) and the value. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 nper-opposite-signs-overflow
+
+Private Sub Control_PositivePmt()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, 100, -1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_PositivePmt: " & E & " " & R
+End Sub
+
+Private Sub Control_RateZero()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0, -100, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_RateZero: " & E & " " & R
+End Sub
+
+Private Sub Control_SameSigns()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, 100, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_SameSigns: " & E & " " & R
+End Sub
+
+Private Sub Loan_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, -100, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Loan_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub CarLoan_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.1 / 12, -500, 20000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "CarLoan_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub LoanWithBalance_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, -100, 1000, 100)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "LoanWithBalance_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub LoanDueAtStart_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, -100, 1000, 0, 1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "LoanDueAtStart_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub SavingsPlan_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, -100, 0, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "SavingsPlan_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub NegativeRate_ReturnsPeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(-0.5, 100, -1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NegativeRate_ReturnsPeriods: " & E & " " & R
+End Sub
+
+Private Sub PmtBelowInterest_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, -1, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PmtBelowInterest_Raises5: " & E & " " & R
+End Sub
+
+Private Sub PmtZero_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(0.01, 0, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PmtZero_Raises5: " & E & " " & R
+End Sub
+
+Private Sub RateMinusOne_Raises5()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = NPer(-1, -100, 1000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "RateMinusOne_Raises5: " & E & " " & R
+End Sub
+
+Sub Main()
+    Open App.Path & "\out.txt" For Output As #9
+    Control_PositivePmt
+    Control_RateZero
+    Control_SameSigns
+    Loan_ReturnsPeriods
+    CarLoan_ReturnsPeriods
+    LoanWithBalance_ReturnsPeriods
+    LoanDueAtStart_ReturnsPeriods
+    SavingsPlan_ReturnsPeriods
+    NegativeRate_ReturnsPeriods
+    PmtBelowInterest_Raises5
+    PmtZero_Raises5
+    RateMinusOne_Raises5
+    Close #9
+End Sub
diff --git a/bugs/nper-opposite-signs-overflow/vb6/Probe.vbp b/bugs/nper-opposite-signs-overflow/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/nper-opposite-signs-overflow/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/rate-fails/rate-fails.twinproj b/bugs/rate-fails/rate-fails.twinproj
new file mode 100644
index 000000000..888d102e5
Binary files /dev/null and b/bugs/rate-fails/rate-fails.twinproj differ
diff --git a/bugs/rate-fails/repro.json b/bugs/rate-fails/repro.json
new file mode 100644
index 000000000..2765bb073
--- /dev/null
+++ b/bugs/rate-fails/repro.json
@@ -0,0 +1,23 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests\\.Control_PmtZeroOnePeriod$",
+      "^PASS RegressionTests\\.Control_PmtZeroThreePeriods$",
+      "^PASS RegressionTests\\.Control_NperNull_Raises94$",
+      "^FAIL RegressionTests\\.PmtZeroTwoPeriods_ReturnsPositiveRate: .*Actual: False ",
+      "^FAIL RegressionTests\\.PmtZeroFourPeriods_ReturnsPositiveRate: .*Actual: False ",
+      "^FAIL RegressionTests\\.Loan_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.Mortgage_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.DueAtStart_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.SavingsPlan_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.SignsReversed_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.PmtZeroTenPeriods_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.WithGuess_ReturnsRate: .*Actual: -2147467259 ",
+      "^FAIL RegressionTests\\.NperBelowOne_ReturnsRate: .*Actual: 5 ",
+      "^FAIL RegressionTests\\.GuessNull_Raises94: .*Actual: 0 ",
+      "^FAIL RegressionTests\\.GuessString_Raises13: .*Actual: 0 "
+    ]
+  }
+}
diff --git a/bugs/rate-fails/src/Settings b/bugs/rate-fails/src/Settings
new file mode 100644
index 000000000..cc9c9c82e
--- /dev/null
+++ b/bugs/rate-fails/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "RateFails",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: Rate raises -2147467259 for almost every annuity",
+	"project.exportPathIsV2": true,
+	"project.id": "{494EFD17-F246-43FF-A8B7-F11D85646DAE}",
+	"project.name": "RateFails",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/rate-fails/src/Sources/RegressionTests.twin b/bugs/rate-fails/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..4dd5ee10b
--- /dev/null
+++ b/bugs/rate-fails/src/Sources/RegressionTests.twin
@@ -0,0 +1,187 @@
+' Regression tests: Rate returns the rate of an annuity, as VB6 and 64-bit VBA do, for a loan,
+' a mortgage, a savings plan, payments due at the start, a guess and an nper below 1, and
+' the positive rate (0.1, not -2.1) of a lump sum over an even number of periods; and it raises
+' 94 for a guess of Null and 13 for a guess that is not a number. The controls are two
+' lump sums Rate answers rightly (one and three periods) and a Null nper.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    [TestCase]
+    Public Sub Control_PmtZeroOnePeriod()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_PmtZeroThreePeriods()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(3, 0, 100, -133.1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Control_NperNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(Null, -100, 800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroTwoPeriods_ReturnsPositiveRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(2, 0, 100, -121)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroFourPeriods_ReturnsPositiveRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(4, 0, 100, -146.41)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.1) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Loan_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub Mortgage_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(360, -600, 100000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0050058250068) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub DueAtStart_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800, 0, 1)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.053446167382) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SavingsPlan_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 0, 1200)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0398902762) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub SignsReversed_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, 100, -800)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub PmtZeroTenPeriods_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, 0, 1000, -2000)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0717734625363) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub WithGuess_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(10, -100, 800, 0, 0, 0.04)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.0427749780351) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub NperBelowOne_ReturnsRate()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(0.5, 0, 100, -110)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 0&, E
+        Assert.Strict.IsTrue Abs(R - 0.21) < 0.000001
+    End Sub
+
+    [TestCase]
+    Public Sub GuessNull_Raises94()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, 0, Null)
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 94&, E
+    End Sub
+
+    [TestCase]
+    Public Sub GuessString_Raises13()
+        Dim A() As Double, B(1, 1) As Double
+        Dim E As Long, R As Variant
+        On Error Resume Next
+        R = Rate(1, 0, 100, -110, 0, "abc")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+End Module
diff --git a/bugs/rate-fails/src/Sources/Startup.twin b/bugs/rate-fails/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/rate-fails/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/rate-fails/vb6/Module1.bas b/bugs/rate-fails/vb6/Module1.bas
new file mode 100644
index 000000000..851620a39
--- /dev/null
+++ b/bugs/rate-fails/vb6/Module1.bas
@@ -0,0 +1,176 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/rate-fails: the cases of src/Sources/RegressionTests.twin, in the same
+' order, each printing the error VB6 raises (0: none) and the value. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 rate-fails
+
+Private Sub Control_PmtZeroOnePeriod()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(1, 0, 100, -110)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_PmtZeroOnePeriod: " & E & " " & R
+End Sub
+
+Private Sub Control_PmtZeroThreePeriods()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(3, 0, 100, -133.1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_PmtZeroThreePeriods: " & E & " " & R
+End Sub
+
+Private Sub Control_NperNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(Null, -100, 800)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Control_NperNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub PmtZeroTwoPeriods_ReturnsPositiveRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(2, 0, 100, -121)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PmtZeroTwoPeriods_ReturnsPositiveRate: " & E & " " & R
+End Sub
+
+Private Sub PmtZeroFourPeriods_ReturnsPositiveRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(4, 0, 100, -146.41)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PmtZeroFourPeriods_ReturnsPositiveRate: " & E & " " & R
+End Sub
+
+Private Sub Loan_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, -100, 800)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Loan_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub Mortgage_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(360, -600, 100000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "Mortgage_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub DueAtStart_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, -100, 800, 0, 1)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "DueAtStart_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub SavingsPlan_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, -100, 0, 1200)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "SavingsPlan_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub SignsReversed_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, 100, -800)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "SignsReversed_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub PmtZeroTenPeriods_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, 0, 1000, -2000)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "PmtZeroTenPeriods_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub WithGuess_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(10, -100, 800, 0, 0, 0.04)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "WithGuess_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub NperBelowOne_ReturnsRate()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(0.5, 0, 100, -110)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "NperBelowOne_ReturnsRate: " & E & " " & R
+End Sub
+
+Private Sub GuessNull_Raises94()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(1, 0, 100, -110, 0, Null)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "GuessNull_Raises94: " & E & " " & R
+End Sub
+
+Private Sub GuessString_Raises13()
+    Dim A() As Double, B(1, 1) As Double
+    Dim E As Long, R As Variant
+    On Error Resume Next
+    R = Rate(1, 0, 100, -110, 0, "abc")
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, "GuessString_Raises13: " & E & " " & R
+End Sub
+
+Sub Main()
+    Open App.Path & "\out.txt" For Output As #9
+    Control_PmtZeroOnePeriod
+    Control_PmtZeroThreePeriods
+    Control_NperNull_Raises94
+    PmtZeroTwoPeriods_ReturnsPositiveRate
+    PmtZeroFourPeriods_ReturnsPositiveRate
+    Loan_ReturnsRate
+    Mortgage_ReturnsRate
+    DueAtStart_ReturnsRate
+    SavingsPlan_ReturnsRate
+    SignsReversed_ReturnsRate
+    PmtZeroTenPeriods_ReturnsRate
+    WithGuess_ReturnsRate
+    NperBelowOne_ReturnsRate
+    GuessNull_Raises94
+    GuessString_Raises13
+    Close #9
+End Sub
diff --git a/bugs/rate-fails/vb6/Probe.vbp b/bugs/rate-fails/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/rate-fails/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/vbacastobj-no-type-mismatch/repro.json b/bugs/vbacastobj-no-type-mismatch/repro.json
new file mode 100644
index 000000000..5f3160d7e
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/repro.json
@@ -0,0 +1,13 @@
+{
+  "mode": "test",
+  "expect": {
+    "exit": 7,
+    "output": [
+      "^PASS RegressionTests.Control_IUnknown_ReturnsTheInterface$",
+      "^PASS RegressionTests.Control_IDispatch_ReturnsTheInterface$",
+      "^PASS RegressionTests.Control_Nothing_ReturnsNothing$",
+      "^FAIL RegressionTests.InterfaceItLacks_Raises13: .*Expected: 13 .*Actual: 0 ",
+      "^FAIL RegressionTests.StringGivenAsTheInterfaceId_Raises13: .*Expected: 13 .*Actual: 0 "
+    ]
+  }
+}
diff --git a/bugs/vbacastobj-no-type-mismatch/src/Settings b/bugs/vbacastobj-no-type-mismatch/src/Settings
new file mode 100644
index 000000000..009930b97
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/src/Settings
@@ -0,0 +1,75 @@
+{
+	"configuration.inherits": "Defaults",
+	"project.appTitle": "VbacastobjNoTypeMismatch",
+	"project.buildPath": "${SourcePath}\\Build\\${ProjectName}_${Architecture}.${FileExtension}",
+	"project.buildType": "Standard EXE",
+	"project.description": "Reproduces: vbaCastObj returns Nothing for an interface the object does not have, where VB6's __vbaCastObj raises 13",
+	"project.exportPathIsV2": true,
+	"project.id": "{F0853028-9C66-46E9-A248-A414E8448136}",
+	"project.name": "VbacastobjNoTypeMismatch",
+	"project.optionExplicit": true,
+	"project.references": [
+		{
+			"id": "{00020430-0000-0000-C000-000000000046}",
+			"lcid": 0,
+			"name": "OLE Automation",
+			"path32": "C:\\Windows\\SysWOW64\\stdole2.tlb",
+			"path64": "C:\\Windows\\System32\\stdole2.tlb",
+			"symbolId": "stdole",
+			"versionMajor": 2,
+			"versionMinor": 0
+		},
+		{
+			"id": "{F50B82D0-DCAB-43FE-9631-11959D4A4728}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - VB Compatibility Package (Forms)",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "VB",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 31
+		},
+		{
+			"id": "{C192FB39-64CA-4D9B-B477-A5502F48EFCC}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] twinBASIC - App global class object",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "AppGlobalClassProject",
+			"versionBuild": 0,
+			"versionMajor": 1,
+			"versionMinor": 0,
+			"versionRevision": 0
+		},
+		{
+			"id": "{9847A10D-8987-44B2-8B87-EA77DEF7F1D9}",
+			"isCompilerPackage": true,
+			"licence": "MIT",
+			"name": "[COMPILER PACKAGE] Assert",
+			"path32": "",
+			"path64": "",
+			"publisher": "TWINBASIC-COMPILER",
+			"symbolId": "Assert",
+			"versionBuild": 0,
+			"versionMajor": 0,
+			"versionMinor": 0,
+			"versionRevision": 24
+		}
+	],
+	"project.settingsVersion": 1,
+	"project.startupObject": "Sub Main",
+	"project.warnings": {
+		"errors": [],
+		"hints": [],
+		"ignored": [],
+		"info": [],
+		"warnings": []
+	},
+	"runtime.useUnicodeStandardLibrary": true
+}
diff --git a/bugs/vbacastobj-no-type-mismatch/src/Sources/RegressionTests.twin b/bugs/vbacastobj-no-type-mismatch/src/Sources/RegressionTests.twin
new file mode 100644
index 000000000..60b37cb62
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/src/Sources/RegressionTests.twin
@@ -0,0 +1,64 @@
+' Regression tests: vbaCastObj raises 13, Type mismatch, when the object does not have the
+' interface asked for, as VB6's own __vbaCastObj (msvbvm60) does, and still returns the
+' interface when it does, and Nothing for Nothing. On BETA 1010 it returns Nothing with no
+' error, for an interface the object lacks and for a String given as the interface ID (whose
+' text is not an interface ID). The VB6 project beside this one calls __vbaCastObj with the
+' same arguments.
+' tbrun --tests runs each case and prints PASS or FAIL.
+[TestFixture]
+Module RegressionTests
+
+    Private Type InterfaceGuid
+        Data1 As Long
+        Data2 As Integer
+        Data3 As Integer
+        Data4(0 To 7) As Byte
+    End Type
+
+    Private Iid As InterfaceGuid
+
+    ' The address of the interface ID {Data1-0000-0000-C000-000000000046}: 0 is IUnknown,
+    ' &H20400 IDispatch, &H12345 an interface nothing has.
+    Private Function StdIid(ByVal Data1 As Long) As LongPtr
+        Iid.Data1 = Data1
+        Iid.Data4(0) = &HC0
+        Iid.Data4(7) = &H46
+        StdIid = VarPtr(Iid)
+    End Function
+
+    [TestCase]
+    Public Sub Control_IUnknown_ReturnsTheInterface()
+        Assert.Strict.IsNotNothing vbaCastObj(New Collection, StdIid(0))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_IDispatch_ReturnsTheInterface()
+        Assert.Strict.IsNotNothing vbaCastObj(New Collection, StdIid(&H20400))
+    End Sub
+
+    [TestCase]
+    Public Sub Control_Nothing_ReturnsNothing()
+        Assert.Strict.IsNothing vbaCastObj(Nothing, StdIid(0))
+    End Sub
+
+    [TestCase]
+    Public Sub InterfaceItLacks_Raises13()
+        Dim E As Long, U As IUnknown
+        On Error Resume Next
+        Set U = vbaCastObj(New Collection, StdIid(&H12345))
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+    [TestCase]
+    Public Sub StringGivenAsTheInterfaceId_Raises13()
+        Dim E As Long, U As IUnknown
+        On Error Resume Next
+        Set U = vbaCastObj(New Collection, "{00000000-0000-0000-C000-000000000046}")
+        E = Err.Number
+        On Error GoTo 0
+        Assert.Strict.AreEqual 13&, E
+    End Sub
+
+End Module
diff --git a/bugs/vbacastobj-no-type-mismatch/src/Sources/Startup.twin b/bugs/vbacastobj-no-type-mismatch/src/Sources/Startup.twin
new file mode 100644
index 000000000..be8f5c8bc
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/src/Sources/Startup.twin
@@ -0,0 +1,6 @@
+Module Startup
+
+    Public Sub Main()
+    End Sub
+
+End Module
diff --git a/bugs/vbacastobj-no-type-mismatch/vb6/Module1.bas b/bugs/vbacastobj-no-type-mismatch/vb6/Module1.bas
new file mode 100644
index 000000000..997a182f0
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/vb6/Module1.bas
@@ -0,0 +1,50 @@
+Attribute VB_Name = "Module1"
+Option Explicit
+
+' The VB6 side of bugs/vbacastobj-no-type-mismatch: the cases of src/Sources/RegressionTests.twin,
+' in the same order, each calling the VB6 runtime's own __vbaCastObj and printing the error
+' it raises (0: none) and whether it returned an interface. Build and run it with:
+'     node scripts/bug_repro.mjs vb6 vbacastobj-no-type-mismatch
+
+Private Type InterfaceGuid
+    Data1 As Long
+    Data2 As Integer
+    Data3 As Integer
+    Data4(0 To 7) As Byte
+End Type
+
+Private Declare Function vbaCastObj Lib "msvbvm60" Alias "__vbaCastObj" (ByVal Obj As Long, ByVal pIid As Long) As Long
+Private Declare Function vbaObjSet Lib "msvbvm60" Alias "__vbaObjSet" (ByRef Dst As Any, ByVal Src As Long) As Long
+
+Private Iid As InterfaceGuid
+
+Private Function StdIid(ByVal Data1 As Long) As Long
+    Iid.Data1 = Data1
+    Iid.Data4(0) = &HC0
+    Iid.Data4(7) = &H46
+    StdIid = VarPtr(Iid)
+End Function
+
+' Calls __vbaCastObj and prints the error and the result; an interface returned is released.
+Private Sub Try(ByVal Name As String, ByVal Obj As Long, ByVal pIid As Long)
+    Dim P As Long, E As Long, U As Object
+    On Error Resume Next
+    P = vbaCastObj(Obj, pIid)
+    E = Err.Number
+    On Error GoTo 0
+    Print #9, Name & ": " & E & " " & IIf(P = 0, "Nothing", "an interface")
+    If P <> 0 Then vbaObjSet U, P
+End Sub
+
+Sub Main()
+    Dim C As New Collection, S As String
+    Open App.Path & "\out.txt" For Output As #9
+    C.Add 1
+    Try "Control_IUnknown_ReturnsTheInterface", ObjPtr(C), StdIid(0)
+    Try "Control_IDispatch_ReturnsTheInterface", ObjPtr(C), StdIid(&H20400)
+    Try "Control_Nothing_ReturnsNothing", 0, StdIid(0)
+    Try "InterfaceItLacks_Raises13", ObjPtr(C), StdIid(&H12345)
+    S = "{00000000-0000-0000-C000-000000000046}"
+    Try "StringGivenAsTheInterfaceId_Raises13", ObjPtr(C), StrPtr(S)
+    Close #9
+End Sub
diff --git a/bugs/vbacastobj-no-type-mismatch/vb6/Probe.vbp b/bugs/vbacastobj-no-type-mismatch/vb6/Probe.vbp
new file mode 100644
index 000000000..4d210b0e8
--- /dev/null
+++ b/bugs/vbacastobj-no-type-mismatch/vb6/Probe.vbp
@@ -0,0 +1,7 @@
+Type=Exe
+Module=Module1; Module1.bas
+Startup="Sub Main"
+ExeName32="Probe.exe"
+Name="Probe"
+CompilationType=0
+OptimizationType=0
diff --git a/bugs/vbacastobj-no-type-mismatch/vbacastobj-no-type-mismatch.twinproj b/bugs/vbacastobj-no-type-mismatch/vbacastobj-no-type-mismatch.twinproj
new file mode 100644
index 000000000..ee3d84e0f
Binary files /dev/null and b/bugs/vbacastobj-no-type-mismatch/vbacastobj-no-type-mismatch.twinproj differ
diff --git a/builder/page-baseline.json b/builder/page-baseline.json
index 80ca1509d..2b5016176 100644
--- a/builder/page-baseline.json
+++ b/builder/page-baseline.json
@@ -1,5 +1,5 @@
 {
   "src": "docs",
-  "pages": 1503,
+  "pages": 1504,
   "staticFiles": 1124
 }
diff --git a/builder/symbol-baseline.json b/builder/symbol-baseline.json
index 398827a3f..d7b51802c 100644
--- a/builder/symbol-baseline.json
+++ b/builder/symbol-baseline.json
@@ -15,6 +15,11 @@
     "/Reference/Data-Types#single",
     "/Reference/Data-Types#string",
     "/Reference/Data-Types#variant",
+    "/Reference/Literal-Keywords#empty",
+    "/Reference/Literal-Keywords#false",
+    "/Reference/Literal-Keywords#nothing",
+    "/Reference/Literal-Keywords#null",
+    "/Reference/Literal-Keywords#true",
     "/tB/Core/AddressOf",
     "/tB/Core/Alias",
     "/tB/Core/And",
diff --git a/builder/symbols.mjs b/builder/symbols.mjs
index b2359ac05..d80b1c096 100644
--- a/builder/symbols.mjs
+++ b/builder/symbols.mjs
@@ -24,10 +24,13 @@
 //     operators". The first word of each form is the statement or operator,
 //     the rest keywords of it: Loop, Next, Wend, Then. Attributes.md, which is
 //     /tB/Core/Attributes, has one attribute to each `##`.
-//   - Reference/Data-Types.md, the one page outside /tB/ that is read: each
-//     intrinsic type its `symbols:` names is a `type`, at the `##` heading of
-//     that name, a short section that links to the type's own page (owner,
-//     2026-10-18). A name with no such heading fails the build.
+//   - The two summary pages outside /tB/, SUMMARY_PAGES: each name the
+//     page's `symbols:` lists is at the `##` heading of that name, and a name
+//     with no such heading fails the build. On Reference/Data-Types.md each
+//     intrinsic type is a `type`, its section a short one that links to the
+//     type's own page (owner, 2026-10-18); on Reference/Literal-Keywords.md
+//     Nothing, Null, Empty, True and False are each a `keyword`, which the
+//     search ranks first, as it does a statement.
 //   - A package folder: a page is a type's when its title or first heading
 //     names a type the package declares ("Strings Module" is Strings, "Len,
 //     LenB" is Len and LenB). A page under a type's page in the nav, named
@@ -72,6 +75,14 @@ export const PACKAGE_FOLDERS = [
 const CORE_FOLDER = "Reference/Core/";
 const ATTRIBUTES_PAGE = "Reference/Attributes.md";
 export const DATA_TYPES_PAGE = "Reference/Data-Types.md";
+export const LITERAL_KEYWORDS_PAGE = "Reference/Literal-Keywords.md";
+
+// The summary pages outside /tB/ that are read, and the kind of each name
+// their `symbols:` lists, at the `##` heading of that name.
+const SUMMARY_PAGES = new Map([
+  [DATA_TYPES_PAGE, "type"],
+  [LITERAL_KEYWORDS_PAGE, "keyword"],
+]);
 
 // Section headings under which every heading names a member, and the kind
 // each gives one the packages do not declare.
@@ -247,11 +258,13 @@ export function deriveSymbolIndex({ pages, api }) {
   const tbPages = pages.filter((p) => String(p.url).startsWith("/tB/"));
 
   // ---- the language
-  const dataTypes = pages.find((p) => p.src === DATA_TYPES_PAGE);
-  for (const name of dataTypes?.symbols ?? []) {
-    const h = dataTypes.headings.find((x) => x.level === 2 && x.id && x.text.toLowerCase() === name.toLowerCase());
-    if (!h) throw new Error(`${DATA_TYPES_PAGE} names ${name} in symbols: and has no ## ${name} heading`);
-    add(entry(name, null, null, "type", `${dataTypes.url}#${h.id}`));
+  for (const [src, kind] of SUMMARY_PAGES) {
+    const summary = pages.find((p) => p.src === src);
+    for (const name of summary?.symbols ?? []) {
+      const h = summary.headings.find((x) => x.level === 2 && x.id && x.text.toLowerCase() === name.toLowerCase());
+      if (!h) throw new Error(`${src} names ${name} in symbols: and has no ## ${name} heading`);
+      add(entry(name, null, null, kind, `${summary.url}#${h.id}`));
+    }
   }
   for (const page of tbPages) {
     if (page.src === ATTRIBUTES_PAGE) {
@@ -605,23 +618,29 @@ export const SYMBOL_INDEX_REL = "tB/symbols.json";
 
 /**
  * The build's pages as deriveSymbolIndex reads them: those under /tB/, and the
- * data types page, with the headings of their rendered HTML.
+ * summary pages, with the headings of their rendered HTML.
  */
 export function symbolPages(pages) {
   return pages
     .filter(
       (p) =>
-        (String(p.permalink ?? "").startsWith("/tB/") || p.srcRel === DATA_TYPES_PAGE) &&
+        (String(p.permalink ?? "").startsWith("/tB/") || SUMMARY_PAGES.has(p.srcRel)) &&
         typeof p.renderedContent === "string",
     )
     .map((p) => {
       const fm = p.frontmatter ?? {};
+      // YAML reads an unquoted True, False or Null as a boolean or null, which would be
+      // indexed as "true", "false" or "null": every name must be written as a string.
+      const odd = fm.symbols == null ? undefined : [].concat(fm.symbols).find((s) => typeof s !== "string");
+      if (odd !== undefined) {
+        throw new Error(`${p.srcRel}: symbols: holds ${JSON.stringify(odd)}, not a name; put the name in quotes`);
+      }
       return {
         src: p.srcRel,
         url: p.permalink,
         title: fm.title,
         parent: fm.parent,
-        symbols: fm.symbols == null ? null : [].concat(fm.symbols).map(String),
+        symbols: fm.symbols == null ? null : [].concat(fm.symbols),
         excludeFromDocs: fm.exclude_from_docs == null ? null : [].concat(fm.exclude_from_docs).map(String),
         headings: headingsOf(p.renderedContent),
       };
diff --git a/docs/Documentation/Authoring.md b/docs/Documentation/Authoring.md
index 6171ba4e1..24f80958a 100644
--- a/docs/Documentation/Authoring.md
+++ b/docs/Documentation/Authoring.md
@@ -286,7 +286,9 @@ symbols: [_HiddenModule]
 ---
 ```
 
-On a statement page the first name is the statement and the rest are its keywords; on an operator page each is an operator of its own --- the comparison operators page lists `["=", "<>", "<", "<=", ">", ">="]`, quoted, because a bare `>` is YAML syntax. Only two pages need it today. A page in a package folder that gives the index no entry at all is named after the build's summary.
+On a statement page the first name is the statement and the rest are its keywords; on an operator page each is an operator of its own --- the comparison operators page lists `["=", "<>", "<", "<=", ">", ">="]`, quoted, because a bare `>` is YAML syntax. Quote `True`, `False` and `Null` as well: YAML reads them bare as a boolean and as no value, and the build refuses an entry that is not a name. Only two pages need it today. A page in a package folder that gives the index no entry at all is named after the build's summary.
+
+Two summary pages outside the package folders are read too, and their `symbols:` list names the page's `##` sections: each intrinsic type of [Data Types](../../Reference/Data-Types), and each keyword of [Literal Keywords](../../Reference/Literal-Keywords) (`["Nothing", "Null", "Empty", "True", "False"]`). A name with no `##` heading of its own fails the build.
 
 ## Index entries for the site search
 
diff --git a/docs/Documentation/Tools-Compiler.md b/docs/Documentation/Tools-Compiler.md
index 7ab15bd73..2ad8b486a 100644
--- a/docs/Documentation/Tools-Compiler.md
+++ b/docs/Documentation/Tools-Compiler.md
@@ -296,7 +296,7 @@ Exit codes: **0** every assertion held, **1** an assertion failed, **2** the tes
     node scripts/impexp.mjs settings|licence|changelog|readme <project>
     node scripts/impexp.mjs --self-test
 
-Standalone `.twinproj` / `.twinpack` unpacker and packer, with the compiler executable's own command line: the same six commands, the project file first, and `--overwrite` required to replace anything. `scripts/impexp.py` is the same tool, run as `python scripts/impexp.py ...`, and `scripts/impexp/` is a third edition, a twinBASIC console program that runs as `impexp_win32.exe ...`. The three editions print the same output, give the same exit codes and write byte-identical project files, which [`check_impexp_parity.mjs`](Tools-Toolchain-Tests#check-impexp-parity) checks. The Node edition needs Node 18+ and the Python edition Python 3.6+; the twinBASIC edition needs Windows and nothing else at run time, and reads and writes its paths as Unicode. None has dependencies. `--self-test` needs only the program, runs the same 20 tests in all three, and adds a round trip of `indexer/sample.twinpack` when it can find that file: the Node and Python editions look in `indexer/` beside their own `scripts/` folder, and the twinBASIC edition in each folder above the exe, then in each folder above the current folder.
+Standalone `.twinproj` / `.twinpack` unpacker and packer, with the compiler executable's own command line: the same six commands, the project file first, and `--overwrite` required to replace anything. `scripts/impexp.py` is the same tool, run as `python scripts/impexp.py ...`, and `scripts/impexp/` is a third edition, a twinBASIC console program that runs as `impexp_win32.exe ...`. An argument that holds a double quote, which is what Windows makes of a folder in quotes that ends with a backslash (`"C:\out\" --overwrite` arrives as `C:\out" --overwrite`), is refused with exit code 2 and the command it meant, without the backslash and after the program as it was run, ready to copy; it is not repaired, because the compiler executable reads `"C:\out\"` as the folder. The three editions print the same output, give the same exit codes and write byte-identical project files, which [`check_impexp_parity.mjs`](Tools-Toolchain-Tests#check-impexp-parity) checks. The Node edition needs Node 18+ and the Python edition Python 3.6+; the twinBASIC edition needs Windows and nothing else at run time, and reads and writes its paths as Unicode. None has dependencies. `--self-test` needs only the program, runs the same 21 tests in all three, and adds a round trip of `indexer/sample.twinpack` when it can find that file: the Node and Python editions look in `indexer/` beside their own `scripts/` folder, and the twinBASIC edition in each folder above the exe, then in each folder above the current folder.
 
 The twinBASIC edition exists for readers who have twinBASIC and neither Node nor Python. It is laid out as [`imagestrip`](Tools-IDE#imagestrip) is: `scripts/impexp/src/` is an exported project tree, and `scripts/impexp/impexp.twinproj` is the project file packed from it, which opens in the IDE. Both are checked out byte for byte (`.gitattributes`). After a change to `src/`, pack it again:
 
diff --git a/docs/Documentation/Tools-Defects.md b/docs/Documentation/Tools-Defects.md
index 057eea17f..ef9f36513 100644
--- a/docs/Documentation/Tools-Defects.md
+++ b/docs/Documentation/Tools-Defects.md
@@ -157,7 +157,7 @@ Exit codes: **0** the sample ran, or, with `--docs`, no fence differs and none r
     node scripts/errors.mjs write [<file.yml>...]
     node scripts/errors.mjs messages [--runtime tb|win64|vb6|vba64]... [--ide <path>] [--vb6 <path>] [--keep]
 
-Measures the run-time errors each documented procedure raises, and writes each reference page's Common Errors section from them. The errors are data, not prose: a YAML file per area under `errors/` lists, for each page, the cases that raise each error and the cases that must raise nothing, and `errors/messages.yml` gives each number's message: the one `Err.Description` gives once the error is raised, and the one `Error$(number)` gives, where the two differ. The format is in `WIP.Errors.md`. Each twinBASIC build is compared with its counterpart: 32-bit twinBASIC with VB6, 64-bit twinBASIC with 64-bit VBA. A case can run under a *harness*, the code of `errors/harnesses/<name>.bas`, one source for twinBASIC, VB6 and VBA, which the probe calls before and after the case: the `clock` harness replaces the system's clock setters in the probe's own process, so a case that sets `Date` or `Time` is measured, and the value it would set checked, without the clock being changed; `registry` removes what a case writes under the VB settings key; `dialog` answers each box `MsgBox` or `InputBox` shows the moment it opens, and refuses one that would open on another desktop; `keys` records the keys `SendKeys` would send and sends none; and `window` gives `AppActivate` a window of the probe to activate. VB6 builds a probe with cases under `dialog` without Unattended Execution, which would write the box to the event log in place of showing it. A file is named as it is in `errors/`; with none named, every file there is used. `--only <regex>` keeps the pages whose path under `docs/` matches.
+Measures the run-time errors each documented procedure raises, and writes each reference page's Common Errors section from them. The errors are data, not prose: a YAML file per area under `errors/` lists, for each page, the cases that raise each error and the cases that must raise nothing, and `errors/messages.yml` gives each number's message: the one `Err.Description` gives once the error is raised, and the one `Error$(number)` gives, where the two differ. The format is in `WIP.Errors.md`. Each twinBASIC build is compared with its counterpart: 32-bit twinBASIC with VB6, 64-bit twinBASIC with 64-bit VBA. A case can run under a *harness*, the code of `errors/harnesses/<name>.bas`, one source for twinBASIC, VB6 and VBA, which the probe calls before and after the case: the `clock` harness replaces the system's clock setters in the probe's own process, so a case that sets `Date` or `Time` is measured, and the value it would set checked, without the clock being changed; `registry` removes what a case writes under the VB settings key; `dialog` answers each box `MsgBox` or `InputBox` shows the moment it opens, and refuses one that would open on another desktop; `keys` records the keys `SendKeys` would send and sends none; `window` gives `AppActivate` a window of the probe to activate; and `files` runs a case in a folder of its own under the temporary folder, made the current directory and filled with a few files, and deletes it afterwards, so a case that copies, deletes or changes files touches nothing else. VB6 builds a probe with cases under `dialog` without Unattended Execution, which would write the box to the event log in place of showing it. A file is named as it is in `errors/`; with none named, every file there is used. `--only <regex>` keeps the pages whose path under `docs/` matches.
 
 | Command | Effect |
 |---|---|
diff --git a/docs/Features/Packages/Import-export tool.md b/docs/Features/Packages/Import-export tool.md
index cf5ae57b8..4420befbc 100644
--- a/docs/Features/Packages/Import-export tool.md	
+++ b/docs/Features/Packages/Import-export tool.md	
@@ -73,11 +73,21 @@ comes first. The verb says what happens to it: `export` takes source out of the
 | `--help` | prints the usage | no | yes |
 
 ```batch
-twinBASIC_win32.exe export "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject\"
+twinBASIC_win32.exe export "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject"
 node impexp.mjs import MyProject.twinproj MyProject --overwrite
 impexp_win32.exe import MyProject.twinproj MyProject --overwrite
 ```
 
+> [!NOTE]
+> Do not end a folder name in quotes with a backslash when running the script. The script
+> splits its command line by the Windows rule that a backslash before a quote makes the quote
+> part of the argument, so `"C:\Projects\MyProject\" --overwrite` reaches it as one argument,
+> `C:\Projects\MyProject" --overwrite`. No Windows file name can hold a double quote, so the
+> script refuses any argument that holds one, exits with code `2`, and prints the command
+> without the backslash, ready to copy. The tB executable splits its command line by its own
+> rule and takes the folder with or without the backslash, although its usage message shows
+> one. `"C:\Projects\MyProject"` works with both.
+
 A package is a project file too: every folder under the installation's `packages\` holds one,
 named `package.twinproj`, so every command works on packages as well.
 
@@ -117,6 +127,7 @@ message that names only `export` and `import`; given no arguments at all, it doe
 | A `.twinpack` file for `export` or `import` | not accepted, see below | accepted |
 | A project that embeds a package | `import` fails, see below | packed |
 | Paths | folders need backslashes, and `export` needs a full path, with backslashes, to the project | any form |
+| A folder in quotes that ends with a backslash, `"C:\out\"` | accepted | refused, and the command without the backslash printed; see the note under [Usage](#usage) |
 | `export` refused because `--overwrite` is missing | writes the files that were not there yet | writes nothing |
 | Files in the folder that the project does not hold | left in place, with no warning | left in place, and listed in a warning |
 | A `.git` folder | packed by `import`, and written back by `export` | skipped by both |
@@ -220,7 +231,7 @@ The steps, in order:
    commit leaves the changes out. The script refuses the whole export, and exits `3`.
 
    ```batch
-   twinBASIC_win32.exe export "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject\src\" --overwrite > tb.log
+   twinBASIC_win32.exe export "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject\src" --overwrite > tb.log
    find "... DONE" tb.log > nul || exit /b 1
    ```
 
@@ -238,7 +249,7 @@ The steps, in order:
    comes first, as in every command:
 
    ```batch
-   twinBASIC_win32.exe import "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject\src\" --overwrite > tb.log
+   twinBASIC_win32.exe import "C:\Projects\MyProject.twinproj" "C:\Projects\MyProject\src" --overwrite > tb.log
    find "... DONE" tb.log > nul || exit /b 1
    ```
 
diff --git a/docs/Reference/Categories.md b/docs/Reference/Categories.md
index 4332aa593..9de23a2c5 100644
--- a/docs/Reference/Categories.md
+++ b/docs/Reference/Categories.md
@@ -200,7 +200,7 @@ Procedures:
 * [GetObject](../tB/Modules/Interaction/GetObject) - obtain a reference to an Automation object loaded from a file or already running
 * [CallByName](../tB/Modules/Interaction/CallByName) - invoke a method or property on an object dynamically by name
 * [CallByDispId](../tB/Modules/Interaction/CallByDispId) - invoke a method or property on an object dynamically by IDispatch dispatch ID (twinBASIC addition)
-* [CreateGUID](../tB/Modules/HiddenModule/CreateGUID) - generate a fresh GUID and return it as a registry-formatted string
+* [CreateGUID](../tB/Modules/HiddenModule/CreateGUID) - generate a fresh GUID and return it as a string
 * [vbaCastObj](../tB/Modules/HiddenModule/vbaCastObj) - reinterpret an object as another COM interface (a typed `QueryInterface`)
 * [vbaObjSet](../tB/Modules/HiddenModule/vbaObjSet), [vbaObjSetAddref](../tB/Modules/HiddenModule/vbaObjSetAddref) - assign a raw object pointer to an **Object** variable, with or without addref
 * [vbaObjAddref](../tB/Modules/HiddenModule/vbaObjAddref) - increment the COM reference count of the object at a given address
diff --git a/docs/Reference/Data-Types.md b/docs/Reference/Data-Types.md
index c32650f9b..6856eeaad 100644
--- a/docs/Reference/Data-Types.md
+++ b/docs/Reference/Data-Types.md
@@ -143,6 +143,7 @@ A date literal is a date, a time of day, or both, between number signs (`#`). Th
 ## See Also
 
 - [New Data Types](../Features/Language/Data-Types) -- **LongLong**, **LongPtr**, and **Decimal** in depth
+- [Literal Keywords](Literal-Keywords) -- **Nothing**, **Null**, **Empty**, **True** and **False**
 - [Enumerations](Enumerations) -- index of all enumeration types across all packages
 - [VbVarType](../tB/Modules/Constants/VbVarType) -- **Variant** subtype tag constants
 - [CDec](../tB/Modules/Conversion/CDec), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr) -- conversion functions for the three extended numeric types
diff --git a/docs/Reference/Default/VBA/Collection/Add.md b/docs/Reference/Default/VBA/Collection/Add.md
index 5d062d49e..438f2c113 100644
--- a/docs/Reference/Default/VBA/Collection/Add.md
+++ b/docs/Reference/Default/VBA/Collection/Add.md
@@ -28,9 +28,34 @@ Syntax: *object*.**Add** *item* [ **,** *key* ] [ **,** *before* ] [ **,** *afte
 
 If neither *before* nor *after* is specified, the new item is added at the end of the collection.
 
-Whether *before* or *after* is a string expression or a numeric expression, it must refer to an existing member of the collection, or an error occurs.
+> [!NOTE]
+> A *before* of one more than **Count** adds the item at the end, and an *after* of 0 adds it at the start. VB6 and 64-bit VBA raise error 9, *Subscript out of range*, for both.
 
-An error also occurs if a specified *key* duplicates the *key* for an existing member of the collection. Key comparison is governed by the [**KeyCompareMode**](KeyCompareMode) property.
+Key comparison is governed by the [**KeyCompareMode**](KeyCompareMode) property.
+
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [457 (`&H1C9`)](tb:Errors#457), *This key is already associated with an element of this collection* | *key* is already the key of an item in the collection, as [**KeyCompareMode**](KeyCompareMode) compares keys (by default `"A"` and `"a"` are the same key) |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *key* is not a **String**: a number, **True**, **Null**, an object, **Nothing** or an array<br>*before* or *after* is -1, **True** or **Empty**<br>*before* or *after* is a **Currency**, **Decimal** or **Date** value<br>*before* or *after* is **Null**, an object or **Nothing**, and the collection is not empty |
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | both *before* and *after* are given<br>*before* or *after* is given and the collection is empty<br>*before* or *after* is a string that is not the key of an item |
+| [9 (`&H9`)](tb:Errors#9), *Subscript out of range* | *before* is a number that, rounded, is less than 1 or greater than **Count** + 1, or *after* one that is less than 0 or greater than **Count**<br>*before* or *after* is a number outside the **Long** range |
+
+> [!NOTE] BETA 1010
+> When *key* is **Empty**, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *before* or *after* is -1, **True** or **Empty**, VB6 and 64-bit VBA raise error [9 (`&H9`)](tb:Errors#9), *Subscript out of range*, instead.
+
+> [!NOTE] BETA 1010
+> When *before* or *after* is a **Currency**, **Decimal** or **Date** value, VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When *before* or *after* is a number outside the **Long** range, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Collection/Exists.md b/docs/Reference/Default/VBA/Collection/Exists.md
index 3716a12ea..8792e2262 100644
--- a/docs/Reference/Default/VBA/Collection/Exists.md
+++ b/docs/Reference/Default/VBA/Collection/Exists.md
@@ -23,6 +23,15 @@ Syntax: *object*.**Exists(** *key* **)**
 
 Key comparison is governed by the [**KeyCompareMode**](KeyCompareMode) property.
 
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *key* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/Collection/Item.md b/docs/Reference/Default/VBA/Collection/Item.md
index 777373973..8cb264288 100644
--- a/docs/Reference/Default/VBA/Collection/Item.md
+++ b/docs/Reference/Default/VBA/Collection/Item.md
@@ -17,8 +17,6 @@ Syntax: *object*.**Item(** *index* **)**
 *index*
 : *required* An expression that specifies the position of a member of the collection. If a numeric expression, *index* must be a number from 1 to the value of the collection's [**Count**](Count) property. If a string expression, *index* must correspond to the *key* argument specified when the member referred to was added to the collection.
 
-If *index* is a number that does not match the position of any member of the collection, run-time error 9 (*Subscript out of range*) occurs. If *index* is a string that does not match the key of any member, run-time error 5 (*Invalid procedure call or argument*) occurs. If *index* is neither a number nor a string, an error also occurs.
-
 To test for a key without raising an error, use [**Exists**](Exists).
 
 **Item** is the default member of a **Collection** object. Therefore, the following lines of code are equivalent:
@@ -31,6 +29,25 @@ Debug.Print MyCollection.Item(1)
 
 Key comparison is governed by the [**KeyCompareMode**](KeyCompareMode) property.
 
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [9 (`&H9`)](tb:Errors#9), *Subscript out of range* | *index* is a number that, rounded, is less than 1 or greater than **Count**, and the collection is not empty<br>the collection is empty and *index* is not a string<br>*index* is **Null**, an object, **Nothing**, an array, an error value or a number outside the **Long** range, and the collection is not empty<br>*index* is a **Currency**, **Decimal** or **Date** value |
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *index* is a string that is not the key of an item |
+
+> [!NOTE] BETA 1010
+> When the collection is empty and *index* is not a string, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *index* is **Null**, an object, **Nothing**, an array, an error value or a number outside the **Long** range, and the collection is not empty, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*, instead.
+
+> [!NOTE] BETA 1010
+> When *index* is a **Currency**, **Decimal** or **Date** value, VB6 and 64-bit VBA raise no error.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Item** method to retrieve a reference to an object in a collection. Assuming `Birthdays` is a **Collection** object, the following code retrieves references to the objects representing Bill Smith's birthday and Adam Smith's birthday, using the keys `"SmithBill"` and `"SmithAdam"` as the *index* arguments.
diff --git a/docs/Reference/Default/VBA/Collection/KeyCompareMode.md b/docs/Reference/Default/VBA/Collection/KeyCompareMode.md
index 078f7f676..231a410ee 100644
--- a/docs/Reference/Default/VBA/Collection/KeyCompareMode.md
+++ b/docs/Reference/Default/VBA/Collection/KeyCompareMode.md
@@ -32,7 +32,18 @@ The *compare* argument settings are:
 
 The default comparison mode is **vbTextCompare**, whatever the module's **Option Compare** setting, so a new **Collection** matches keys as VBA's does.
 
-The mode can be changed only while the collection holds no item added with a key. Once one has been added, setting a different mode raises run-time error 5, *Can't change KeyCompareMode once keyed items have been added to the collection*, and the mode stays as it was. Items added without a key do not prevent the change, and neither do keyed items that have since been removed. Setting the mode the collection already has raises no error. A *compare* value other than **vbBinaryCompare** or **vbTextCompare** raises run-time error 5, *Invalid procedure call or argument*.
+The mode can be changed only while the collection holds no item added with a key. Items added without a key do not prevent the change, and neither do keyed items that have since been removed or cleared. Setting the mode the collection already has is allowed at any time.
+
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *compare* is not **vbBinaryCompare** or **vbTextCompare** after rounding |
+| [5 (`&H5`)](tb:Errors#5), *Can't change KeyCompareMode once keyed items have been added to the collection* | the mode is changed while the collection holds an item added with a key; the mode stays as it was |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *compare* is **Null** |
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Collection/KeyCountHint.md b/docs/Reference/Default/VBA/Collection/KeyCountHint.md
index c05e2887b..20d44ce19 100644
--- a/docs/Reference/Default/VBA/Collection/KeyCountHint.md
+++ b/docs/Reference/Default/VBA/Collection/KeyCountHint.md
@@ -27,6 +27,15 @@ Setting **KeyCountHint** is optional. It is most effective when set before any i
 
 The hint affects only keyed items (those added with a **Key** argument); items added without a key are unaffected.
 
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *hint* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/Collection/Remove.md b/docs/Reference/Default/VBA/Collection/Remove.md
index a59584985..9f8e45f75 100644
--- a/docs/Reference/Default/VBA/Collection/Remove.md
+++ b/docs/Reference/Default/VBA/Collection/Remove.md
@@ -17,12 +17,26 @@ Syntax: *object*.**Remove(** *index* **)**
 *index*
 : *required* An expression that specifies the member of the collection to remove. If a numeric expression, *index* must be a number from 1 to the value of the collection's [**Count**](Count) property. If a string expression, *index* must correspond to the *key* argument specified when the member was added to the collection.
 
-If *index* doesn't match an existing member of the collection, an error occurs.
-
 When an item is removed, the indexes of subsequent items decrease by one. Take this into account when iterating over a collection while removing items --- see the example below.
 
 Key comparison is governed by the [**KeyCompareMode**](KeyCompareMode) property.
 
+<!-- errors: generated from errors/VBA.Collection.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [9 (`&H9`)](tb:Errors#9), *Subscript out of range* | *index* is a number that, rounded, is less than 1 or greater than **Count**, and the collection is not empty<br>*index* is **Null**, an object, **Nothing**, an array or a number outside the **Long** range, and the collection is not empty<br>*index* is a **Currency**, **Decimal** or **Date** value |
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *index* is a string that is not the key of an item<br>the collection is empty |
+
+> [!NOTE] BETA 1010
+> When *index* is **Null**, an object, **Nothing**, an array or a number outside the **Long** range, and the collection is not empty, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*, instead.
+
+> [!NOTE] BETA 1010
+> When *index* is a **Currency**, **Decimal** or **Date** value, VB6 and 64-bit VBA raise no error.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Remove** method to remove every object from a **Collection** named `MyClasses`. Because items are reindexed automatically, the first item is removed on each iteration of the loop.
diff --git a/docs/Reference/Default/VBA/ErrObject/Description.md b/docs/Reference/Default/VBA/ErrObject/Description.md
index ca71d2e9e..a14ec859e 100644
--- a/docs/Reference/Default/VBA/ErrObject/Description.md
+++ b/docs/Reference/Default/VBA/ErrObject/Description.md
@@ -23,6 +23,15 @@ When generating a user-defined error, assign a short description of the error to
 > [!WARNING] BETA 1010
 > For a number that has no built-in message, **Raise** without a *description* leaves **Description** as an empty string, a Windows system message or `Automation error`, depending on the number, and raises no error. VBA and VB6 place `Application-defined or object-defined error` there. [**Raise**](Raise) has the table.
 
+<!-- errors: generated from errors/VBA.ErrObject.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *errorDescription* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example assigns a user-defined message to the **Description** property of the **Err** object.
diff --git a/docs/Reference/Default/VBA/ErrObject/HelpContext.md b/docs/Reference/Default/VBA/ErrObject/HelpContext.md
index b97677188..f6ef00da4 100644
--- a/docs/Reference/Default/VBA/ErrObject/HelpContext.md
+++ b/docs/Reference/Default/VBA/ErrObject/HelpContext.md
@@ -22,6 +22,10 @@ If both **HelpFile** and **HelpContext** are empty, the value of [**Number**](Nu
 
 Write routines to handle typical errors. When programming with an object, the object's Help file can improve error handling or display a meaningful message to the user when an error isn't recoverable.
 
+<!-- bug: err-helpfile-helpcontext-codegen -->
+> [!NOTE] BETA 1010
+> A statement that assigns **HelpContext**, such as `Err.HelpContext = 5`, compiles, but the build fails with a code-generation error in the procedure that holds it. [**Raise**](Raise) sets **HelpContext** without the problem, and so does an assignment through a variable declared **As Object** that holds **Err**.
+
 ### Example
 
 This example uses the **HelpContext** property of the **Err** object to show the Help topic for the `Overflow` error.
diff --git a/docs/Reference/Default/VBA/ErrObject/HelpFile.md b/docs/Reference/Default/VBA/ErrObject/HelpFile.md
index d5bdb4fde..97db54911 100644
--- a/docs/Reference/Default/VBA/ErrObject/HelpFile.md
+++ b/docs/Reference/Default/VBA/ErrObject/HelpFile.md
@@ -20,6 +20,10 @@ If a Help file is specified in **HelpFile**, it is automatically called when the
 
 Write routines to handle typical errors. When programming with an object, the object's Help file can improve error handling or display a meaningful message to the user when an error isn't recoverable.
 
+<!-- bug: err-helpfile-helpcontext-codegen -->
+> [!NOTE] BETA 1010
+> A statement that assigns **HelpFile**, such as `Err.HelpFile = "MyHelp.chm"`, compiles, but the build fails with a code-generation error in the procedure that holds it. [**Raise**](Raise) sets **HelpFile** without the problem, and so does an assignment through a variable declared **As Object** that holds **Err**.
+
 ### Example
 
 This example uses the **HelpFile** property of the **Err** object to start the Help system.
diff --git a/docs/Reference/Default/VBA/ErrObject/Number.md b/docs/Reference/Default/VBA/ErrObject/Number.md
index e5087426b..3225b71b7 100644
--- a/docs/Reference/Default/VBA/ErrObject/Number.md
+++ b/docs/Reference/Default/VBA/ErrObject/Number.md
@@ -22,6 +22,22 @@ When returning a user-defined error from an object, set **Err.Number** by adding
 Err.Raise Number:=vbObjectError + 1051, Source:="SomeClass"
 ```
 
+> [!NOTE]
+> **Number** accepts a number above 65535. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*, for one.
+
+<!-- bug: err-raise-hresult-mapping -->
+> [!NOTE] BETA 1010
+> **Number** keeps an **HRESULT** assigned to it as it is. VB6 and 64-bit VBA store the VB error of the same meaning for the ones that [**Raise**](Raise) turns into VB errors: after `Err.Number = &H80070057`, **Number** is 5 there, and in twinBASIC it is -2147024809.
+
+<!-- errors: generated from errors/VBA.ErrObject.yml by scripts/errors.mjs write; edit the data, not this section -->
+## Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *errorNumber* is **Null** |
+
+<!-- /errors -->
+
 ## Example
 
 The first example illustrates a typical use of the **Number** property in an error-handling routine.
diff --git a/docs/Reference/Default/VBA/ErrObject/Raise.md b/docs/Reference/Default/VBA/ErrObject/Raise.md
index 6ff1bd20c..80c2cda08 100644
--- a/docs/Reference/Default/VBA/ErrObject/Raise.md
+++ b/docs/Reference/Default/VBA/ErrObject/Raise.md
@@ -37,7 +37,10 @@ When *description* is omitted, **Description** depends on *number*:
 | 747 or more | the Windows system message for that number when there is one, as for 1001 (`Recursion too deep; the stack overflowed.`), and otherwise `Automation error` |
 | negative | the Windows system message for that value as an **HRESULT** when there is one, and otherwise `Automation error` |
 
-A *description* of an empty string gives an empty **Description** for every number. The system messages are in the language of the system and differ between Windows versions; `Automation error` is the only text of the table that does not come from the system. A number above 65535 is accepted.
+A *description* of an empty string gives an empty **Description** for every number. The system messages are in the language of the system and differ between Windows versions; `Automation error` is the only text of the table that does not come from the system.
+
+> [!NOTE]
+> **Raise** accepts a *number* above 65535 and raises that number. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*, for one.
 
 When the error is raised in a method of a class and the caller handles it, an empty **Description** reaches the caller as `Application-defined or object-defined error`. The other texts arrive unchanged.
 
@@ -47,8 +50,45 @@ When the error is raised in a method of a class and the caller handles it, an em
 > [!NOTE] BETA 1010
 > An error that a class member raises with a constant *number*, such as `Err.Raise 380`, reaches a caller that called the member late-bound --- through an **Object** variable or [**CallByName**](../Interaction/CallByName) --- as error -2147352567 (`&H80020009`), *Exception occurred.*, not as 380. VB6 raises 380. The number arrives unchanged when the member passes it in a variable, as in `Err.Raise Number`, and in every early-bound call.
 
+<!-- bug: err-raise-hresult-mapping -->
+> [!NOTE] BETA 1010
+> **Raise** raises an **HRESULT** *number* as it is. VB6 and 64-bit VBA raise many **HRESULT**s as the VB error of the same meaning instead, including these:
+>
+> | *number* | VB6 and 64-bit VBA raise |
+> |---|---|
+> | `&H80070057` (`E_INVALIDARG`) | 5 |
+> | `&H8007000E` (`E_OUTOFMEMORY`) | 7 |
+> | `&H80070005` (`E_ACCESSDENIED`), `&H80030005` (`STG_E_ACCESSDENIED`) | 70 |
+> | `&H80004001` (`E_NOTIMPL`) | 445 |
+> | `&H80004002` (`E_NOINTERFACE`) | 430 |
+> | `&H80004004` (`E_ABORT`) | 287 |
+> | `&H80020003` (`DISP_E_MEMBERNOTFOUND`), `&H80020006` (`DISP_E_UNKNOWNNAME`) | 438 |
+> | `&H80020005` (`DISP_E_TYPEMISMATCH`) | 13 |
+> | `&H80020008` (`DISP_E_BADVARTYPE`) | 458 |
+> | `&H8002000A` (`DISP_E_OVERFLOW`) | 6 |
+> | `&H8002000B` (`DISP_E_BADINDEX`) | 9 |
+> | `&H8002000E` (`DISP_E_BADPARAMCOUNT`) | 450 |
+> | `&H80020011` (`DISP_E_NOTACOLLECTION`) | 451 |
+> | `&H80030002` (`STG_E_FILENOTFOUND`) | 432 |
+> | `&H80030003` (`STG_E_PATHNOTFOUND`) | 76 |
+> | `&H80030070` (`STG_E_MEDIUMFULL`) | 61 |
+> | `&H80040154` (`REGDB_E_CLASSNOTREG`), `&H80040112` (`CLASS_E_NOTLICENSED`), `&H800401E3` (`MK_E_UNAVAILABLE`), `&H800401F3` (`CO_E_CLASSSTRING`) | 429 |
+> | `&H800A0001` to `&H800AFFFF`, a VB error as an **HRESULT** | its low 16 bits: 5 for `&H800A0005`, 53 for `&H800A0035` |
+>
+> They keep others as they are, such as `&H80004005` (`E_FAIL`), `&H80020009` (`DISP_E_EXCEPTION`) and `&H80070002`. A handler that tests for a VB number, such as 5, does not recognise the **HRESULT** that twinBASIC raises.
+
 **Raise** is preferred over the [**Error**](../../Core/Error) statement when generating run-time errors, particularly inside class modules: the **Err** object holds richer information than the **Error** statement can supply. With **Raise** the source that generated the error can be specified in the [**Source**](Source) property, online Help for the error can be referenced through [**HelpFile**](HelpFile) and [**HelpContext**](HelpContext), and so on.
 
+<!-- errors: generated from errors/VBA.ErrObject.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *number* is 0 after rounding, or **Empty** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | an argument is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Raise** method of the **Err** object to generate an error from inside an Automation object with the programmatic ID `MyProj.MyObject`.
diff --git a/docs/Reference/Default/VBA/ErrObject/ReturnHResult.md b/docs/Reference/Default/VBA/ErrObject/ReturnHResult.md
index 61ffce9a8..3d34d4286 100644
--- a/docs/Reference/Default/VBA/ErrObject/ReturnHResult.md
+++ b/docs/Reference/Default/VBA/ErrObject/ReturnHResult.md
@@ -17,17 +17,23 @@ Syntax: **Err**.**ReturnHResult** **=** *value*
 
 A calling procedure can then use [**LastHresult**](LastHresult) to read the positive HRESULT that was returned from the method. Set **ReturnHResult** only when needed, typically just before the method exit point, so that the intended HRESULT is the one that's actually returned.
 
+<!-- bug: err-helpfile-helpcontext-codegen -->
+> [!NOTE] BETA 1010
+> Assigning **ReturnHResult** in a procedure of a module, rather than in a method of a class, compiles, but the build fails with a code-generation error in that procedure.
+
 ### Example
 
 This example demonstrates setting a non-failure HRESULT upon successfully completing a method within a COM object.
 
 ```tb check_build
-Function MyMethod() As Variant
-    ' ... perform method actions here ...
-
-    ' Indicate success with a specific non-failure HRESULT.
-    Err.ReturnHResult = 123
-End Function
+Class MyObject
+    Public Function MyMethod() As Variant
+        ' ... perform method actions here ...
+
+        ' Indicate success with a specific non-failure HRESULT.
+        Err.ReturnHResult = 123
+    End Function
+End Class
 ```
 
 After the method completes, the caller can read **Err.LastHresult** to retrieve this specific HRESULT value.
diff --git a/docs/Reference/Default/VBA/ErrObject/Source.md b/docs/Reference/Default/VBA/ErrObject/Source.md
index a4d97c1eb..9d6696eff 100644
--- a/docs/Reference/Default/VBA/ErrObject/Source.md
+++ b/docs/Reference/Default/VBA/ErrObject/Source.md
@@ -27,6 +27,15 @@ When an error occurs that twinBASIC raises itself, such as a division by zero, *
 > [!WARNING] BETA 1010
 > It does not fill in **Source**, and raises no error. VBA and VB6 fill it in automatically with the name of the project, for an error that the runtime raises and for **Raise** without a source argument. A program that reads **Err.Source** to find where an error came from gets an empty string.
 
+<!-- errors: generated from errors/VBA.ErrObject.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *errorSource* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example assigns the programmatic ID of an Automation object to the variable `myObjectID`, and then assigns that to the **Source** property of the **Err** object when it generates an error with the [**Raise**](Raise) method.
diff --git a/docs/Reference/Default/VBA/FileSystem/ChDir.md b/docs/Reference/Default/VBA/FileSystem/ChDir.md
index 6ccb91652..ac81296b1 100644
--- a/docs/Reference/Default/VBA/FileSystem/ChDir.md
+++ b/docs/Reference/Default/VBA/FileSystem/ChDir.md
@@ -24,9 +24,6 @@ ChDir "D:\TMP" ' Make "D:\TMP" the current folder.
 ChDrive "D"    ' Make "D" the current drive. 
 ```
 
-> [!NOTE] BETA 1010
-> **ChDir** raises run-time error -2147467259 (`&H80004005`) for a *path* that does not exist, where VB6 raises 76 (*Path not found*).
-
 <!--
 On Linux MacOS, the default drive always changes to the drive specified in *path*. Full path specifications begin with the volume name, and relative paths begin with a colon (**:**). **ChDir** resolves any aliases specified in the path: 
 
@@ -42,6 +39,19 @@ On MacOS, the default drive name is "HD" and portions of the pathname are separa
 
 -->
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *path* names no folder that exists, which includes a file, a drive that does not exist, a zero-length string, and a name with a wildcard or a character a name cannot hold |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *path* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *path* names no folder that exists, which includes a file, a drive that does not exist, a zero-length string, and a name with a wildcard or a character a name cannot hold, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **ChDir** statement to change the current directory or folder.
diff --git a/docs/Reference/Default/VBA/FileSystem/ChDrive.md b/docs/Reference/Default/VBA/FileSystem/ChDrive.md
index 4d50f80e1..e302dce80 100644
--- a/docs/Reference/Default/VBA/FileSystem/ChDrive.md
+++ b/docs/Reference/Default/VBA/FileSystem/ChDrive.md
@@ -16,6 +16,22 @@ Syntax: **ChDrive** *drive*
 *drive*
 : *required* A string expression that specifies an existing drive. If *drive* is a zero-length string (""), the current drive doesn't change. If the *drive* argument is a multiple-character string, **ChDrive** uses only the first letter.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *drive* starts with a letter that no drive has<br>*drive* starts with a digit, a space or a punctuation character |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *drive* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *drive* starts with a letter that no drive has, VB6 and 64-bit VBA raise error [68 (`&H44`)](tb:Errors#68), *Device unavailable*, instead.
+
+> [!NOTE] BETA 1010
+> When *drive* starts with a digit, a space or a punctuation character, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
+
 ### See Also
 
 - [ChDir](ChDir), [MkDir](MkDir), and [RmDir](RmDir) statements
diff --git a/docs/Reference/Default/VBA/FileSystem/CurDir.md b/docs/Reference/Default/VBA/FileSystem/CurDir.md
index 0a6855b73..b1d948842 100644
--- a/docs/Reference/Default/VBA/FileSystem/CurDir.md
+++ b/docs/Reference/Default/VBA/FileSystem/CurDir.md
@@ -20,6 +20,9 @@ Syntax: **CurDir** [ **(** *drive* **)** ]
 *drive*
 : *optional* String expression that specifies an existing drive. If no drive is specified or if *drive* is a zero-length string (`""`), **CurDir** returns the path for the current drive.
 
+> [!NOTE]
+> A *drive* that is not a **String**, such as a number or a **Boolean**, is converted to one, as in **ChDrive**, in both **CurDir** and **CurDir$**: `CurDir(5)` looks for drive 5. VB6 and 64-bit VBA raise error 13, *Type mismatch*, for it.
+
 ### Example
 
 This example uses the **CurDir** function to return the current path.
@@ -58,6 +61,25 @@ MyPath = CurDir$("C")  ' Returns "C:\WINDOWS\SYSTEM".
 MyPath = CurDir$("D")  ' Returns "D:\EXCEL".
 ```
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *drive* starts with a letter that no drive has<br>*drive* starts with a digit, a space or a punctuation character |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *drive* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *drive* starts with a letter that no drive has, VB6 and 64-bit VBA raise error [68 (`&H44`)](tb:Errors#68), *Device unavailable*, instead.
+
+> [!NOTE] BETA 1010
+> When *drive* starts with a digit, a space or a punctuation character, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *drive* is **Null**, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*, instead.
+
+<!-- /errors -->
+
 ### See Also
 
 - [ChDir](ChDir), [ChDrive](ChDrive) statements
diff --git a/docs/Reference/Default/VBA/FileSystem/Dir.md b/docs/Reference/Default/VBA/FileSystem/Dir.md
index 30a513e43..38ef572b8 100644
--- a/docs/Reference/Default/VBA/FileSystem/Dir.md
+++ b/docs/Reference/Default/VBA/FileSystem/Dir.md
@@ -19,6 +19,9 @@ Syntax: **Dir** [ **(** *pathname* [ **,** *attributes* ] **)** ]
 *attributes*
 : *optional* Constant or numeric expression, whose sum specifies file attributes. If omitted, returns files that match *pathname* but have no attributes.
 
+> [!NOTE]
+> **Dir** ignores a bit of *attributes* that the table below does not list, so -1 returns every kind of entry, as 23 (**vbReadOnly** + **vbHidden** + **vbSystem** + **vbDirectory**) does. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*, for any value above 63 or below 0. A *pathname* that is not a **String**, such as a number or a **Boolean**, is converted to one, as in **ChDir**: `Dir(5)` looks for a file named 5. VB6 and 64-bit VBA raise error 13, *Type mismatch*, for it.
+
 The *attributes* argument settings are:
 
 | Constant        | Value | Description                                                                              |
@@ -34,13 +37,35 @@ The *attributes* argument settings are:
 
 The first call to **Dir** must specify *pathname*, or an error occurs. When file attributes are also specified, *pathname* must be included.
 
-**Dir** returns the first file name that matches *pathname*. To get any additional file names that match *pathname*, call **Dir** again with no arguments. When no more file names match, **Dir** returns a zero-length string (`""`). After a zero-length string is returned, subsequent calls must specify *pathname*, or an error occurs.
+**Dir** returns the first file name that matches *pathname*. To get any additional file names that match *pathname*, call **Dir** again with no arguments. When no more file names match, **Dir** returns a zero-length string (`""`). After a zero-length string is returned, the next call must specify *pathname*.
 
 A new *pathname* can be specified without first retrieving all of the file names that match the current *pathname*. However, **Dir** cannot be called recursively. Calling **Dir** with the **vbDirectory** attribute does not continually return subdirectories.
 
 > [!TIP]
 > Because file names are retrieved in case-insensitive order on Windows, consider storing returned file names in an array and sorting the array.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | **Dir** is called without *pathname* after it has returned a zero-length string<br>*pathname* names a file and ends in a backslash<br>a name in *pathname* is longer than 255 characters |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* is **Null**<br>*attributes* is **Null** |
+
+> [!NOTE] BETA 1010
+> When **Dir** is called without *pathname* after it has returned a zero-length string, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* names a file and ends in a backslash, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When a name in *pathname* is longer than 255 characters, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* is **Null**, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*, instead.
+
+<!-- /errors -->
+
 ### See Also
 
 - [ChDir](ChDir), [ChDrive](ChDrive), [MkDir](MkDir), [RmDir](RmDir) statements
diff --git a/docs/Reference/Default/VBA/FileSystem/EOF.md b/docs/Reference/Default/VBA/FileSystem/EOF.md
index 557dbf00d..f5692d577 100644
--- a/docs/Reference/Default/VBA/FileSystem/EOF.md
+++ b/docs/Reference/Default/VBA/FileSystem/EOF.md
@@ -24,8 +24,18 @@ The **EOF** function returns **False** until the end of the file has been reache
 
 With files opened for **Binary** access, an attempt to read through the file by using the **Input** function until **EOF** returns **True** generates an error. Use the [LOF](LOF) and **Loc** functions instead of **EOF** when reading binary files with **Input**, or use **Get** when using the **EOF** function. With files opened for **Output**, **EOF** always returns **True**.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *filenumber* is not the number of an open file |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *filenumber* is **Null** |
+
 > [!NOTE] BETA 1010
-> **EOF** raises run-time error -2147467259 (`&H80004005`) for a *filenumber* that is not open, where VB6 raises 52 (*Bad file name or number*).
+> When *filenumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/FileAttr.md b/docs/Reference/Default/VBA/FileSystem/FileAttr.md
index 73b184a29..861a445c7 100644
--- a/docs/Reference/Default/VBA/FileSystem/FileAttr.md
+++ b/docs/Reference/Default/VBA/FileSystem/FileAttr.md
@@ -19,9 +19,6 @@ Syntax: **FileAttr(** *filenumber* **,** *returntype* **)**
 *returntype*
 : *required* **Integer** indicating the type of information to return. Must be **1** to return the file access mode.
 
-> [!NOTE] BETA 1010
-> **FileAttr** raises run-time error -2147467259 (`&H80004005`) for a *filenumber* that is not open, where VB6 raises 52 (*Bad file name or number*).
-
 ### Return Values
 
 The following return values indicate the file access mode:
@@ -34,6 +31,22 @@ The following return values indicate the file access mode:
 | **Append** | 8     |
 | **Binary** | 32    |
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *filenumber* is not the number of an open file<br>*returntype* is not 1, after rounding |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *filenumber* or *returntype* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *filenumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *returntype* is not 1, after rounding, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **FileAttr** function to return the file mode of an open file.
diff --git a/docs/Reference/Default/VBA/FileSystem/FileCopy.md b/docs/Reference/Default/VBA/FileSystem/FileCopy.md
index 959cd12c8..dc7443b6c 100644
--- a/docs/Reference/Default/VBA/FileSystem/FileCopy.md
+++ b/docs/Reference/Default/VBA/FileSystem/FileCopy.md
@@ -19,7 +19,39 @@ Syntax: **FileCopy** *source*, *destination*
 *destination*
 : *required* String expression that specifies the target file name. The *destination* may include directory or folder, and drive.
 
-**FileCopy** raises run-time error 55 (*File already open*) when *source* is a file that is currently open for **Append**. A file that is open for **Input** is copied without an error, and so is a file that is closed.
+A *source* that the program has open is copied when it is open for reading only: **For Input**, or with **Access Read** in any mode, and not locked against reading.
+
+> [!NOTE]
+> VB6 and 64-bit VBA copy an open *source* only when it is open **For Input** and not locked against reading, and raise error 55, *File already open*, for one open with **Access Read** in another mode.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [53 (`&H35`)](tb:Errors#53), *File not found* | *source* does not exist |
+| [76 (`&H4C`)](tb:Errors#76), *Path not found* | the folder or drive named in *source* or *destination* does not exist, or *destination* ends in a backslash |
+| [55 (`&H37`)](tb:Errors#55), *File already open* | *source* is open with write access or locked against reading, or *destination* is open<br>*destination* names the same file as *source*<br>*source* is open **For Input** with **Lock Read** |
+| [70 (`&H46`)](tb:Errors#70), *Permission denied* | *source* is a folder, or *destination* is a folder or a read-only or hidden file |
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *source* or *destination* is a zero-length string<br>*source* or *destination* holds a wildcard or a character a file name cannot hold |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *source* or *destination* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *destination* names the same file as *source*, VB6 and 64-bit VBA raise error [70 (`&H46`)](tb:Errors#70), *Permission denied*, instead.
+
+> [!NOTE] BETA 1010
+> When *source* is open **For Input** with **Lock Read**, VB6 and 64-bit VBA raise error [70 (`&H46`)](tb:Errors#70), *Permission denied*, instead.
+
+> [!NOTE] BETA 1010
+> When *source* is a folder, or *destination* is a folder or a read-only or hidden file, VB6 and 64-bit VBA raise error [75 (`&H4B`)](tb:Errors#75), *Path/File access error*, instead.
+
+> [!NOTE] BETA 1010
+> When *source* or *destination* is a zero-length string, VB6 and 64-bit VBA raise error [75 (`&H4B`)](tb:Errors#75), *Path/File access error*, instead.
+
+> [!NOTE] BETA 1010
+> When *source* or *destination* holds a wildcard or a character a file name cannot hold, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/FileDateTime.md b/docs/Reference/Default/VBA/FileSystem/FileDateTime.md
index 16483bf03..28b7702f3 100644
--- a/docs/Reference/Default/VBA/FileSystem/FileDateTime.md
+++ b/docs/Reference/Default/VBA/FileSystem/FileDateTime.md
@@ -16,8 +16,31 @@ Syntax: **FileDateTime(** *pathname* **)**
 *pathname*
 : *required* String expression that specifies a file name. The *pathname* may include the directory or folder, and the drive.
 
+<!-- bug: filesystem-argument-checks -->
+> [!WARNING] BETA 1010
+> Given a *pathname* with a wildcard (`*` or `?`) that matches a file or a folder, **FileDateTime** returns the date and time of the first match, which may be a hidden file or a folder, and raises no error. VB6 and 64-bit VBA raise error 52, *Bad file name or number*.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold<br>the folder or drive named in *pathname* does not exist<br>*pathname* holds a wildcard that matches no file or folder |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* is **Null** |
+
+> [!NOTE] BETA 1010
+> When no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
 > [!NOTE] BETA 1010
-> **FileDateTime** raises run-time error -2147467259 (`&H80004005`) for a file that does not exist, where VB6 raises 53 (*File not found*).
+> When the folder or drive named in *pathname* does not exist, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard that matches no file or folder, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard that matches a file or folder, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/FileLen.md b/docs/Reference/Default/VBA/FileSystem/FileLen.md
index cfc7a212d..3669cb238 100644
--- a/docs/Reference/Default/VBA/FileSystem/FileLen.md
+++ b/docs/Reference/Default/VBA/FileSystem/FileLen.md
@@ -21,8 +21,31 @@ If the specified file is open when the **FileLen** function is called, the value
 > [!NOTE]
 > Use the [LOF](LOF) function to obtain the length of an open file.
 
+<!-- bug: filesystem-argument-checks -->
+> [!WARNING] BETA 1010
+> Given a *pathname* with a wildcard (`*` or `?`) that matches a file or a folder, **FileLen** returns the length of the first match, which may be a hidden file, or a folder, whose length is 0, and raises no error. VB6 and 64-bit VBA raise error 52, *Bad file name or number*.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold<br>the folder or drive named in *pathname* does not exist<br>*pathname* holds a wildcard that matches no file or folder |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* is **Null** |
+
+> [!NOTE] BETA 1010
+> When no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
 > [!NOTE] BETA 1010
-> **FileLen** raises run-time error -2147467259 (`&H80004005`) for a file that does not exist, where VB6 raises 53 (*File not found*).
+> When the folder or drive named in *pathname* does not exist, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard that matches no file or folder, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard that matches a file or folder, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/FreeFile.md b/docs/Reference/Default/VBA/FileSystem/FreeFile.md
index a447f832f..146258015 100644
--- a/docs/Reference/Default/VBA/FileSystem/FreeFile.md
+++ b/docs/Reference/Default/VBA/FileSystem/FreeFile.md
@@ -18,6 +18,19 @@ Syntax: **FreeFile** [ **(** *rangenumber* **)** ]
 
 Use **FreeFile** to supply a file number that is not already in use.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | every file number from 1 to 255 is in use |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rangenumber* is **Null** |
+
+> [!NOTE] BETA 1010
+> When every file number from 1 to 255 is in use, VB6 and 64-bit VBA raise error [67 (`&H43`)](tb:Errors#67), *Too many files*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **FreeFile** function to return the next available file number. Five files are opened for output within the loop, and some sample data is written to each.
diff --git a/docs/Reference/Default/VBA/FileSystem/GetAttr.md b/docs/Reference/Default/VBA/FileSystem/GetAttr.md
index b899624e7..37205b989 100644
--- a/docs/Reference/Default/VBA/FileSystem/GetAttr.md
+++ b/docs/Reference/Default/VBA/FileSystem/GetAttr.md
@@ -16,9 +16,6 @@ Syntax: **GetAttr(** *pathname* **)**
 *pathname*
 : *required* String expression that specifies a file name. The *pathname* may include the directory or folder, and the drive.
 
-> [!NOTE] BETA 1010
-> **GetAttr** raises run-time error -2147467259 (`&H80004005`) for a *pathname* that does not exist. VB6 raises 53 (*File not found*), or 76 (*Path not found*) when the folder does not exist.
-
 ### Return Values
 
 The value returned by **GetAttr** is the sum of the following attribute values:
@@ -41,6 +38,28 @@ Result = GetAttr(FName) And vbArchive
 
 A nonzero value is returned if the Archive attribute is set.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no file or folder has the name *pathname*, or it is a zero-length string<br>the folder or drive named in *pathname* does not exist<br>*pathname* holds a wildcard<br>*pathname* holds a character a name cannot hold, or names a file with a backslash at its end |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* is **Null** |
+
+> [!NOTE] BETA 1010
+> When no file or folder has the name *pathname*, or it is a zero-length string, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
+> [!NOTE] BETA 1010
+> When the folder or drive named in *pathname* does not exist, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a character a name cannot hold, or names a file with a backslash at its end, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **GetAttr** function to determine the attributes of a file and directory or folder.
diff --git a/docs/Reference/Default/VBA/FileSystem/Input.md b/docs/Reference/Default/VBA/FileSystem/Input.md
index 12b12d219..0b2635202 100644
--- a/docs/Reference/Default/VBA/FileSystem/Input.md
+++ b/docs/Reference/Default/VBA/FileSystem/Input.md
@@ -30,6 +30,31 @@ For files opened for **Binary** access, an attempt to read through the file usin
 > [!NOTE]
 > Use [**InputB**](InputB) for byte data contained within text files. With **InputB**, *Number* specifies the number of bytes to return rather than the number of characters.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *Number* is more characters than are left in a file open for **Input**<br>the file is open for **Output**, **Append** or **Random**<br>*Number* is negative, after rounding<br>*FileNumber* is not the number of an open file<br>*Number* is 0, after rounding |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Number* or *FileNumber* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *Number* is more characters than are left in a file open for **Input**, VB6 and 64-bit VBA raise error [62 (`&H3E`)](tb:Errors#62), *Input past end of file*, instead.
+
+> [!NOTE] BETA 1010
+> When the file is open for **Output**, **Append** or **Random**, VB6 and 64-bit VBA raise error [54 (`&H36`)](tb:Errors#54), *Bad file mode*, instead.
+
+> [!NOTE] BETA 1010
+> When *Number* is negative, after rounding, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *FileNumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *Number* is 0, after rounding, VB6 and 64-bit VBA raise no error.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Input** function to read one character at a time from a file and print it to the [Debug Console](../../IDE/Debugging/Debug-Console). *TESTFILE* is assumed to be a text file with a few lines of sample data.
diff --git a/docs/Reference/Default/VBA/FileSystem/InputB.md b/docs/Reference/Default/VBA/FileSystem/InputB.md
index e146a12fc..03eaea785 100644
--- a/docs/Reference/Default/VBA/FileSystem/InputB.md
+++ b/docs/Reference/Default/VBA/FileSystem/InputB.md
@@ -25,6 +25,28 @@ Syntax:
 
 The bytes are packed into the result without any character-set translation; the **String** form simply reinterprets the byte run as a UTF-16 string for storage.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *Number* is more bytes than are left in a file open for **Input**<br>the file is open for **Output**, **Append** or **Random**<br>*Number* is negative, after rounding<br>*FileNumber* is not the number of an open file |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Number* or *FileNumber* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *Number* is more bytes than are left in a file open for **Input**, VB6 and 64-bit VBA raise error [62 (`&H3E`)](tb:Errors#62), *Input past end of file*, instead.
+
+> [!NOTE] BETA 1010
+> When the file is open for **Output**, **Append** or **Random**, VB6 and 64-bit VBA raise error [54 (`&H36`)](tb:Errors#54), *Bad file mode*, instead.
+
+> [!NOTE] BETA 1010
+> When *Number* is negative, after rounding, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *FileNumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/FileSystem/Kill.md b/docs/Reference/Default/VBA/FileSystem/Kill.md
index fc03b7894..463baff3e 100644
--- a/docs/Reference/Default/VBA/FileSystem/Kill.md
+++ b/docs/Reference/Default/VBA/FileSystem/Kill.md
@@ -18,18 +18,35 @@ Syntax: **Kill** *pathname*
 
 **Kill** supports the use of multiple-character (`*`) and single-character (`?`) wildcards to specify multiple files.
 
-An error occurs when **Kill** is used to delete an open file.
-
-> [!NOTE] BETA 1010
-> Each of these failures of **Kill** raises run-time error -2147467259 (`&H80004005`), where VB6 raises the numbered error shown:
->
-> - 53 (*File not found*) when no file matches *pathname*;
-> - 75 (*Path/File access error*) for a read-only file;
-> - 55 (*File already open*) for a file that is open.
+<!-- bug: kill-hidden-system-files -->
+> [!WARNING] BETA 1010
+> **Kill** deletes a hidden or a system file, whether *pathname* names it or a wildcard matches it, and raises no error. VB6 and 64-bit VBA never delete such a file: they raise error 53, *File not found*, when *pathname* matches only hidden or system files, and otherwise delete the other files a wildcard matches and leave these.
 
 > [!NOTE]
 > To delete directories, use the [**RmDir**](RmDir) statement.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no file matches *pathname*, which includes a folder, a folder or drive that does not exist, and a zero-length string<br>the file, or a file a wildcard matches, is read-only<br>the file, or a file a wildcard matches, is open |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* is **Null** |
+
+> [!NOTE] BETA 1010
+> When no file matches *pathname*, which includes a folder, a folder or drive that does not exist, and a zero-length string, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
+> [!NOTE] BETA 1010
+> When the file, or a file a wildcard matches, is read-only, VB6 and 64-bit VBA raise error [75 (`&H4B`)](tb:Errors#75), *Path/File access error*, instead.
+
+> [!NOTE] BETA 1010
+> When the file, or a file a wildcard matches, is open, VB6 and 64-bit VBA raise error [55 (`&H37`)](tb:Errors#55), *File already open*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* names a hidden or system file, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*; twinBASIC raises none.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Kill** statement to delete a file from a disk.
diff --git a/docs/Reference/Default/VBA/FileSystem/LOF.md b/docs/Reference/Default/VBA/FileSystem/LOF.md
index 70b312c25..6bb21e135 100644
--- a/docs/Reference/Default/VBA/FileSystem/LOF.md
+++ b/docs/Reference/Default/VBA/FileSystem/LOF.md
@@ -19,8 +19,18 @@ Syntax: **LOF(** *filenumber* **)**
 > [!NOTE]
 > Use the **FileLen** function to obtain the length of a file that is not open.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *filenumber* is not the number of an open file |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *filenumber* is **Null** |
+
 > [!NOTE] BETA 1010
-> **LOF** raises run-time error -2147467259 (`&H80004005`) for a *filenumber* that is not open, where VB6 raises 52 (*Bad file name or number*).
+> When *filenumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/Loc.md b/docs/Reference/Default/VBA/FileSystem/Loc.md
index 632d1232c..f56831619 100644
--- a/docs/Reference/Default/VBA/FileSystem/Loc.md
+++ b/docs/Reference/Default/VBA/FileSystem/Loc.md
@@ -26,8 +26,18 @@ The return value depends on the file access mode:
 | **Sequential** | Current byte position in the file divided by 128.           |
 | **Binary**     | Position of the last byte read or written.                  |
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *filenumber* is not the number of an open file |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *filenumber* is **Null** |
+
 > [!NOTE] BETA 1010
-> **Loc** raises run-time error -2147467259 (`&H80004005`) for a *filenumber* that is not open, where VB6 raises 52 (*Bad file name or number*).
+> When *filenumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/MkDir.md b/docs/Reference/Default/VBA/FileSystem/MkDir.md
index 6e8e8a2b9..a81e44017 100644
--- a/docs/Reference/Default/VBA/FileSystem/MkDir.md
+++ b/docs/Reference/Default/VBA/FileSystem/MkDir.md
@@ -16,8 +16,21 @@ Syntax: **MkDir** *path*
 *path*
 : A string expression that identifies the directory or folder to be created. The *path* may include the drive. If no drive is specified, **MkDir** creates the new directory or folder on the current drive.
 
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *path* already exists, as a folder or as a file<br>the folder or drive that would hold *path* does not exist, or *path* is a zero-length string or a name a folder cannot have |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *path* is **Null** |
+
 > [!NOTE] BETA 1010
-> **MkDir** raises run-time error -2147467259 (`&H80004005`) when it fails. VB6 raises 75 (*Path/File access error*) when *path* already exists, and 76 (*Path not found*) when the folder that would hold it does not exist.
+> When *path* already exists, as a folder or as a file, VB6 and 64-bit VBA raise error [75 (`&H4B`)](tb:Errors#75), *Path/File access error*, instead.
+
+> [!NOTE] BETA 1010
+> When the folder or drive that would hold *path* does not exist, or *path* is a zero-length string or a name a folder cannot have, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+<!-- /errors -->
 
 ### See Also
 
diff --git a/docs/Reference/Default/VBA/FileSystem/RmDir.md b/docs/Reference/Default/VBA/FileSystem/RmDir.md
index 8ddbffa69..37e7674e7 100644
--- a/docs/Reference/Default/VBA/FileSystem/RmDir.md
+++ b/docs/Reference/Default/VBA/FileSystem/RmDir.md
@@ -16,10 +16,23 @@ Syntax: **RmDir** *path*
 *path*
 : A string expression that identifies the directory or folder to be removed. The *path* may include the drive. If no drive is specified, **RmDir** removes the directory or folder on the current drive.
 
-An error occurs when **RmDir** is used on a directory or folder containing files. Use the [**Kill**](Kill) statement to delete all files before attempting to remove a directory or folder.
+**RmDir** removes only an empty folder. To remove a folder that holds files, delete them first with the [**Kill**](Kill) statement.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no folder has the name *path*, which includes a file, a zero-length string, and a name with a wildcard or a character a name cannot hold<br>the folder holds a file or a folder, or it is the current directory |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *path* is **Null** |
 
 > [!NOTE] BETA 1010
-> **RmDir** raises run-time error -2147467259 (`&H80004005`) when it fails. VB6 raises 75 (*Path/File access error*) for a folder that holds files, and 76 (*Path not found*) for one that does not exist.
+> When no folder has the name *path*, which includes a file, a zero-length string, and a name with a wildcard or a character a name cannot hold, VB6 and 64-bit VBA raise error [76 (`&H4C`)](tb:Errors#76), *Path not found*, instead.
+
+> [!NOTE] BETA 1010
+> When the folder holds a file or a folder, or it is the current directory, VB6 and 64-bit VBA raise error [75 (`&H4B`)](tb:Errors#75), *Path/File access error*, instead.
+
+<!-- /errors -->
 
 ### See Also
 
diff --git a/docs/Reference/Default/VBA/FileSystem/Seek.md b/docs/Reference/Default/VBA/FileSystem/Seek.md
index 2594f86e1..36e99799f 100644
--- a/docs/Reference/Default/VBA/FileSystem/Seek.md
+++ b/docs/Reference/Default/VBA/FileSystem/Seek.md
@@ -41,10 +41,23 @@ Syntax: **Seek** [ **#** ] *filenumber*, *position*
 
 Record numbers specified in [Get](../../Core/Get) and [Put](../../Core/Put) statements override file positioning performed by **Seek**.
 
-Performing a file-write operation after a **Seek** operation beyond the end of a file extends the file. Attempting a **Seek** to a negative or zero position causes an error.
+Performing a file-write operation after a **Seek** operation beyond the end of a file extends the file.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *filenumber* is not the number of an open file<br>the statement's *position* is less than 1, after rounding |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *filenumber* or *position* is **Null** |
 
 > [!NOTE] BETA 1010
-> The **Seek** function and statement raise run-time error -2147467259 (`&H80004005`) for a *filenumber* that is not open, where VB6 raises 52 (*Bad file name or number*). The statement raises the same error for a *position* of 0, where VB6 raises 63 (*Bad record number*).
+> When *filenumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When the statement's *position* is less than 1, after rounding, VB6 and 64-bit VBA raise error [63 (`&H3F`)](tb:Errors#63), *Bad record number*, instead.
+
+<!-- /errors -->
 
 ### Examples
 
diff --git a/docs/Reference/Default/VBA/FileSystem/SetAttr.md b/docs/Reference/Default/VBA/FileSystem/SetAttr.md
index 6cb02ad31..52c0aa38f 100644
--- a/docs/Reference/Default/VBA/FileSystem/SetAttr.md
+++ b/docs/Reference/Default/VBA/FileSystem/SetAttr.md
@@ -31,13 +31,35 @@ The *attributes* settings are:
 | **vbSystem**   | 4     | System file.                        |
 | **vbArchive**  | 32    | File has changed since last backup. |
 
+**SetAttr** passes *attributes* to Windows as it is, so it sets any attribute Windows lets a program set, such as 256 (temporary) or 8192 (not indexed), and raises an error where Windows refuses. A bit that Windows ignores, such as **vbDirectory** (16) on a file, is left out.
+
+> [!NOTE]
+> VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*, for *attributes* that are not a sum of the values in the table, and for **vbDirectory** on a folder.
+
 **SetAttr** sets the attributes of a file that is open, whatever mode it is open in, without an error.
 
+<!-- bug: setattr-open-file-no-error -->
 > [!WARNING] BETA 1010
-> This differs from VB6, which raises run-time error 55 (*File already open*) for a file open for **Output**, **Append**, **Binary** or **Random**, and leaves its attributes unchanged. VB6 sets them only for a file open for **Input**. So twinBASIC can make a file read-only while the program still has it open for writing.
+> This differs from VB6 and 64-bit VBA, which raise run-time error 55 (*File already open*) for a file open for **Output**, **Append**, **Binary** or **Random**, and leave its attributes unchanged. They set them only for a file open for **Input**. So twinBASIC can make a file read-only while the program still has it open for writing.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | no file or folder has the name *pathname*, which includes one in a folder or drive that does not exist, a zero-length string, and a name with a character a name cannot hold<br>*pathname* holds a wildcard |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *pathname* or *attributes* is **Null** |
 
 > [!NOTE] BETA 1010
-> **SetAttr** raises run-time error -2147467259 (`&H80004005`) for a file that does not exist, where VB6 raises 53 (*File not found*).
+> When no file or folder has the name *pathname*, which includes one in a folder or drive that does not exist, a zero-length string, and a name with a character a name cannot hold, VB6 and 64-bit VBA raise error [53 (`&H35`)](tb:Errors#53), *File not found*, instead.
+
+> [!NOTE] BETA 1010
+> When *pathname* holds a wildcard, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When the file is open for **Output**, **Append**, **Binary** or **Random**, VB6 and 64-bit VBA raise error [55 (`&H37`)](tb:Errors#55), *File already open*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/Width.md b/docs/Reference/Default/VBA/FileSystem/Width.md
index 013cfaa4d..eb79e5bdd 100644
--- a/docs/Reference/Default/VBA/FileSystem/Width.md
+++ b/docs/Reference/Default/VBA/FileSystem/Width.md
@@ -18,7 +18,30 @@ Syntax: **Width #** *FileNumber* **,** *Width*
 : *required* The file number used to open the file.
 
 *Width*
-: *required* A numeric expression in the range 0--255, inclusive, indicating how many characters appear on a line before a new line is started. If *Width* equals `0`, there is no limit to the length of a line. The default is `0`.
+: *required* An **Integer** in the range 0--32,767, inclusive, indicating how many characters appear on a line before a new line is started. If *Width* equals `0`, there is no limit to the length of a line. The default is `0`.
+
+> [!NOTE]
+> VB6 and 64-bit VBA take a *Width* from 0 to 255 only, and raise error 5, *Invalid procedure call or argument*, for one above 255.
+
+<!-- bug: filesystem-argument-checks -->
+> [!WARNING] BETA 1010
+> A negative *Width* raises no error, and **Print #** then starts a new line before each item after the first. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- errors: generated from errors/VBA.FileSystem.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *FileNumber* is not the number of an open file |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Width* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *FileNumber* is not the number of an open file, VB6 and 64-bit VBA raise error [52 (`&H34`)](tb:Errors#52), *Bad file name or number*, instead.
+
+> [!NOTE] BETA 1010
+> When *Width* is negative, after rounding, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/FileSystem/index.md b/docs/Reference/Default/VBA/FileSystem/index.md
index 625e028d4..447e3dbae 100644
--- a/docs/Reference/Default/VBA/FileSystem/index.md
+++ b/docs/Reference/Default/VBA/FileSystem/index.md
@@ -35,7 +35,7 @@ Loop
 
 ## Copying and deleting
 
-[**FileCopy**](FileCopy) copies one file to another, and [**Kill**](Kill) deletes files matching a wildcard pattern. Both operate by pathname. **Kill** raises a run-time error when asked to delete a file that is open, and **FileCopy** raises one for a file that is open for **Append**.
+[**FileCopy**](FileCopy) copies one file to another, and [**Kill**](Kill) deletes files matching a wildcard pattern. Both operate by pathname. **Kill** raises a run-time error when asked to delete a file that is open, and **FileCopy** raises one for a file that is open with write access.
 
 ```tb check_build
 FileCopy "C:\Data\report.xlsx", "C:\Backup\report.xlsx"
diff --git a/docs/Reference/Default/VBA/Financial/DDB.md b/docs/Reference/Default/VBA/Financial/DDB.md
index 5bbb6aab9..16603d64d 100644
--- a/docs/Reference/Default/VBA/Financial/DDB.md
+++ b/docs/Reference/Default/VBA/Financial/DDB.md
@@ -28,12 +28,34 @@ Syntax: **DDB(** *cost*, *salvage*, *life*, *period* [ **,** *factor* ] **)**
 
 The double-declining balance method computes depreciation at an accelerated rate. Depreciation is highest in the first period and decreases in successive periods.
 
-The *life* and *period* arguments must be expressed in the same units. For example, if *life* is given in months, *period* must also be given in months. All arguments must be positive numbers.
+The *life* and *period* arguments must be expressed in the same units. For example, if *life* is given in months, *period* must also be given in months.
+
+<!-- VBA: twinBASIC, VB6 and 64-bit VBA take a negative or zero cost and a zero salvage (Common Errors lists what they refuse). All arguments must be positive numbers. -->
 
 The **DDB** function uses the following formula to calculate depreciation for a given period:
 
 Depreciation / *period* = ((*cost* - *salvage*) * *factor*) / *life*
 
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *life* is 0 or less, *period* is 0 or less or greater than *life*, *salvage* is less than 0, or *factor* is 0 or less (**Empty** and **True** included)<br>*life* is greater than 0 and less than 1 |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *factor* is not a number or a string that holds one<br>*factor* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *cost*, *salvage*, *life* or *period* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *life* is 0 or less, *period* is 0 or less or greater than *life*, *salvage* is less than 0, or *factor* is 0 or less (**Empty** and **True** included), VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *life* is greater than 0 and less than 1, VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When *factor* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **DDB** function to return the depreciation of an asset for a specified period given the initial cost (`InitCost`), the salvage value at the end of the asset's useful life (`SalvageVal`), the total life of the asset in years (`LifeTime`), and the period in years for which the depreciation is calculated (`Depr`).
diff --git a/docs/Reference/Default/VBA/Financial/FV.md b/docs/Reference/Default/VBA/Financial/FV.md
index cdeb06a8b..9e058b7fc 100644
--- a/docs/Reference/Default/VBA/Financial/FV.md
+++ b/docs/Reference/Default/VBA/Financial/FV.md
@@ -15,7 +15,7 @@ Syntax: **FV(** *rate*, *nper*, *pmt* [ **,** *pv* [ **,** *type* ] ] **)**
 : *required* **Double** specifying interest rate per period. For example, for a car loan at an annual percentage rate (APR) of 10 percent with monthly payments, the rate per period is 0.1/12, or 0.0083.
 
 *nper*
-: *required* **Integer** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
+: *required* **Double** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
 
 *pmt*
 : *required* **Double** specifying payment to be made each period. Payments usually contain principal and interest that doesn't change over the life of the annuity.
@@ -32,6 +32,24 @@ The *rate* and *nper* arguments must be calculated by using payment periods expr
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *rate* is -1 and *nper* is less than 0 |
+| [6 (`&H6`)](tb:Errors#6), *Overflow* | the result is beyond the range of a **Double** |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *pv* or *type* is a string that is not a number, or an error value<br>*pv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *nper* or *pmt* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *rate* is -1 and *nper* is less than 0, VB6 raises error [11 (`&HB`)](tb:Errors#11), *Division by zero*, instead; 64-bit VBA raises error [6 (`&H6`)](tb:Errors#6), *Overflow*, instead.
+
+> [!NOTE] BETA 1010
+> When *pv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **FV** function to return the future value of an investment given the percentage rate that accrues per period (`APR / 12`), the total number of payments (`TotPmts`), the payment (`Payment`), the current value of the investment (`PVal`), and a number that indicates whether the payment is made at the beginning or end of the payment period (`PayType`). Note that because `Payment` represents cash paid out, it's a negative number.
diff --git a/docs/Reference/Default/VBA/Financial/IPmt.md b/docs/Reference/Default/VBA/Financial/IPmt.md
index 1261f42ac..17fb20a0b 100644
--- a/docs/Reference/Default/VBA/Financial/IPmt.md
+++ b/docs/Reference/Default/VBA/Financial/IPmt.md
@@ -35,6 +35,30 @@ The *rate* and *nper* arguments must be calculated by using payment periods expr
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+<!-- bug: financial-argument-checks -->
+> [!WARNING] BETA 1010
+> Given a *per* of 0 or less, or of *nper* + 1 or more, **IPmt** returns a value computed for that period, outside the annuity, and raises no error. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *nper* is 0 or less |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *per*, *nper* or *pv* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *per* is 0 or less, or *nper* + 1 or more, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *nper* is 0 or less, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **IPmt** function to calculate how much of a payment is interest when all the payments are of equal value. Given are the interest percentage rate per period (`APR / 12`), the payment period for which the interest portion is desired (`Period`), the total number of payments (`TotPmts`), the present value or principal of the loan (`PVal`), the future value of the loan (`FVal`), and a number that indicates whether the payment is due at the beginning or end of the payment period (`PayType`).
diff --git a/docs/Reference/Default/VBA/Financial/IRR.md b/docs/Reference/Default/VBA/Financial/IRR.md
index e347124b7..80b083f7c 100644
--- a/docs/Reference/Default/VBA/Financial/IRR.md
+++ b/docs/Reference/Default/VBA/Financial/IRR.md
@@ -21,7 +21,29 @@ The internal rate of return is the interest rate received for an investment cons
 
 The **IRR** function uses the order of values within the array to interpret the order of payments and receipts. The payment and receipt values must be in the correct sequence. The cash flow for each period doesn't have to be fixed, as it is for an annuity.
 
-**IRR** is calculated by iteration. Starting with the value of *guess*, **IRR** cycles through the calculation until the result is accurate to within 0.00001 percent. If **IRR** can't find a result after 20 tries, it fails.
+**IRR** is calculated by iteration. Starting with the value of *guess*, **IRR** cycles through the calculation until the result is accurate to within 0.00001 percent, and fails if it finds none in 20 tries.
+
+<!-- bug: financial-array-arguments -->
+> [!WARNING] BETA 1010
+> Given an array that has never been sized (`Dim A() As Double` with no **ReDim**, or one emptied by **Erase**), **IRR** ends the program with an access violation, in a 32-bit and a 64-bit build. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *values* has no element less than 0 or none greater than 0, or **IRR** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included) |
+| [-2147418113 (`&H8000FFFF`)](tb:Errors#-2147418113), *Catastrophic failure* | *values* has more than one dimension |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *guess* is a string that is not a number |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *guess* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *values* has no element less than 0 or none greater than 0, or **IRR** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included), VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *values* has more than one dimension, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Financial/MIRR.md b/docs/Reference/Default/VBA/Financial/MIRR.md
index e36352bed..1e088baf1 100644
--- a/docs/Reference/Default/VBA/Financial/MIRR.md
+++ b/docs/Reference/Default/VBA/Financial/MIRR.md
@@ -12,7 +12,10 @@ Returns a **Double** specifying the modified internal rate of return for a serie
 Syntax: **MIRR(** *values()*, *finance_rate*, *reinvest_rate* **)**
 
 *values()*
-: *required* Array of **Double** specifying cash flow values. The array must contain at least one negative value (a payment) and one positive value (a receipt).
+: *required* Array of **Double** specifying cash flow values, at least one of them negative (a payment).
+<!-- VBA: twinBASIC, VB6 and 64-bit VBA take values with no positive element (Common Errors lists what they refuse).
+The array must contain at least one negative value (a payment) and one positive value (a receipt).
+-->
 
 *finance_rate*
 : *required* **Double** specifying interest rate paid as the cost of financing.
@@ -26,6 +29,33 @@ The *finance_rate* and *reinvest_rate* arguments are percentages expressed as de
 
 The **MIRR** function uses the order of values within the array to interpret the order of payments and receipts. The payment and receipt values must be in the correct sequence.
 
+<!-- bug: financial-array-arguments -->
+> [!WARNING] BETA 1010
+> Given an array that has never been sized (`Dim A() As Double` with no **ReDim**, or one emptied by **Erase**), **MIRR** ends the program with an access violation, in a 32-bit and a 64-bit build. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- bug: financial-argument-checks -->
+> [!WARNING] BETA 1010
+> **MIRR** returns a value and raises no error for arguments VB6 and 64-bit VBA refuse. Given *values* with one element it returns -1, and given a *finance_rate* or *reinvest_rate* of -1 it returns a rate; VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*. Given *values* with no element less than 0 it returns infinity or NaN (not a number); VB6 and 64-bit VBA raise error 11, *Division by zero*.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147418113 (`&H8000FFFF`)](tb:Errors#-2147418113), *Catastrophic failure* | *values* has more than one dimension |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *finance_rate* or *reinvest_rate* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *values* has one element, or *finance_rate* or *reinvest_rate* is -1, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *values* has no element less than 0, VB6 and 64-bit VBA raise error [11 (`&HB`)](tb:Errors#11), *Division by zero*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *values* has more than one dimension, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **MIRR** function to return the modified internal rate of return for a series of cash flows contained in the array `Values()`. `LoanAPR` represents the financing interest, and `InvAPR` represents the interest rate received on reinvestment.
diff --git a/docs/Reference/Default/VBA/Financial/NPV.md b/docs/Reference/Default/VBA/Financial/NPV.md
index 59b449ae0..7b6979115 100644
--- a/docs/Reference/Default/VBA/Financial/NPV.md
+++ b/docs/Reference/Default/VBA/Financial/NPV.md
@@ -15,7 +15,10 @@ Syntax: **NPV(** *rate*, *values()* **)**
 : *required* **Double** specifying discount rate over the length of the period, expressed as a decimal.
 
 *values()*
-: *required* Array of **Double** specifying cash flow values. The array must contain at least one negative value (a payment) and one positive value (a receipt).
+: *required* Array of **Double** specifying cash flow values.
+<!-- VBA: twinBASIC, VB6 and 64-bit VBA take values with no negative or no positive element, and an array of one element.
+The array must contain at least one negative value (a payment) and one positive value (a receipt).
+-->
 
 The net present value of an investment is the current value of a future series of payments and receipts.
 
@@ -27,6 +30,30 @@ The net present value calculation is based on future cash flows. If the first ca
 
 The **NPV** function is similar to the [**PV**](PV) function (present value) except that the **PV** function allows cash flows to begin either at the end or the beginning of a period. Unlike the variable **NPV** cash flow values, **PV** cash flows must be fixed throughout the investment.
 
+<!-- bug: financial-array-arguments -->
+> [!WARNING] BETA 1010
+> Given an array that has never been sized (`Dim A() As Double` with no **ReDim**, or one emptied by **Erase**), **NPV** ends the program with an access violation, in a 32-bit and a 64-bit build. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- bug: financial-argument-checks -->
+> [!WARNING] BETA 1010
+> Given a *rate* of -1, **NPV** returns NaN (not a number) and raises no error. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147418113 (`&H8000FFFF`)](tb:Errors#-2147418113), *Catastrophic failure* | *values* has more than one dimension |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *rate* is -1, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *values* has more than one dimension, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **NPV** function to return the net present value for a series of cash flows contained in the array `Values()`. `RetRate` represents the fixed internal rate of return.
diff --git a/docs/Reference/Default/VBA/Financial/NPer.md b/docs/Reference/Default/VBA/Financial/NPer.md
index 35ae42e8d..2061e3db8 100644
--- a/docs/Reference/Default/VBA/Financial/NPer.md
+++ b/docs/Reference/Default/VBA/Financial/NPer.md
@@ -30,6 +30,34 @@ An annuity is a series of fixed cash payments made over a period of time. An ann
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [6 (`&H6`)](tb:Errors#6), *Overflow* | *rate* and *pmt* are of opposite signs, as in a loan or a savings plan, and a number of periods exists<br>no number of periods exists, as when *pmt* does not cover the interest, or *rate* is -1 and *pmt* is greater than 0 |
+| [11 (`&HB`)](tb:Errors#11), *Division by zero* | *pmt* is 0 and *rate* is not 0, or *rate* is -1 and *pmt* is less than 0 |
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *rate* and *pmt* are both 0 |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *pmt* or *pv* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *rate* and *pmt* are of opposite signs, as in a loan or a savings plan, and a number of periods exists, VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When no number of periods exists, as when *pmt* does not cover the interest, or *rate* is -1 and *pmt* is greater than 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *pmt* is 0 and *rate* is not 0, or *rate* is -1 and *pmt* is less than 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *rate* and *pmt* are both 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **NPer** function to return the number of periods during which payments must be made to pay off a loan whose value is contained in `PVal`. Also provided are the interest percentage rate per period (`APR / 12`), the payment (`Payment`), the future value of the loan (`FVal`), and a number that indicates whether the payment is due at the beginning or end of the payment period (`PayType`).
diff --git a/docs/Reference/Default/VBA/Financial/PPmt.md b/docs/Reference/Default/VBA/Financial/PPmt.md
index 3aef96032..3d971bee1 100644
--- a/docs/Reference/Default/VBA/Financial/PPmt.md
+++ b/docs/Reference/Default/VBA/Financial/PPmt.md
@@ -15,10 +15,10 @@ Syntax: **PPmt(** *rate*, *per*, *nper*, *pv* [ **,** *fv* [ **,** *type* ] ] **
 : *required* **Double** specifying interest rate per period. For example, for a car loan at an annual percentage rate (APR) of 10 percent with monthly payments, the rate per period is 0.1/12, or 0.0083.
 
 *per*
-: *required* **Integer** specifying payment period in the range 1 through *nper*.
+: *required* **Double** specifying payment period in the range 1 through *nper*.
 
 *nper*
-: *required* **Integer** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
+: *required* **Double** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
 
 *pv*
 : *required* **Double** specifying present value, or value today, of a series of future payments or receipts. For example, when borrowing money to buy a car, the loan amount is the present value to the lender of the monthly car payments to be made.
@@ -35,6 +35,34 @@ The *rate* and *nper* arguments must be calculated using payment periods express
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+<!-- bug: financial-argument-checks -->
+> [!WARNING] BETA 1010
+> Given a *per* of 0 or less, or of *nper* + 1 or more, **PPmt** returns a value computed for that period, outside the annuity, and raises no error. VB6 and 64-bit VBA raise error 5, *Invalid procedure call or argument*.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [11 (`&HB`)](tb:Errors#11), *Division by zero* | *nper* is 0 |
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *nper* is less than 0 |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *per*, *nper* or *pv* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *per* is 0 or less, or *nper* + 1 or more, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *nper* is 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *nper* is less than 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **PPmt** function to calculate how much of a payment for a specific period is principal when all the payments are of equal value. Given are the interest percentage rate per period (`APR / 12`), the payment period for which the principal portion is desired (`Period`), the total number of payments (`TotPmts`), the present value or principal of the loan (`PVal`), the future value of the loan (`FVal`), and a number that indicates whether the payment is due at the beginning or end of the payment period (`PayType`).
diff --git a/docs/Reference/Default/VBA/Financial/PV.md b/docs/Reference/Default/VBA/Financial/PV.md
index 7fafe5912..0eaa48ad5 100644
--- a/docs/Reference/Default/VBA/Financial/PV.md
+++ b/docs/Reference/Default/VBA/Financial/PV.md
@@ -15,7 +15,7 @@ Syntax: **PV(** *rate*, *nper*, *pmt* [ **,** *fv* [ **,** *type* ] ] **)**
 : *required* **Double** specifying interest rate per period. For example, for a car loan at an annual percentage rate (APR) of 10 percent with monthly payments, the rate per period is 0.1/12, or 0.0083.
 
 *nper*
-: *required* **Integer** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
+: *required* **Double** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
 
 *pmt*
 : *required* **Double** specifying payment to be made each period. Payments usually contain principal and interest that doesn't change over the life of the annuity.
@@ -32,6 +32,33 @@ The *rate* and *nper* arguments must be calculated using payment periods express
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+> [!NOTE]
+> **PV** raises error 11, *Division by zero*, for a result beyond the range of a **Double**, as 64-bit VBA does. VB6 returns infinity.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *rate* is -1 and *nper* is 0<br>*rate* is -1 and *nper* is greater than 0<br>*rate* is -1 and *nper* is less than 0 |
+| [11 (`&HB`)](tb:Errors#11), *Division by zero* | the result is beyond the range of a **Double** |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *nper* or *pmt* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *rate* is -1 and *nper* is 0, VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When *rate* is -1 and *nper* is greater than 0, VB6 raises no error; 64-bit VBA raises error [11 (`&HB`)](tb:Errors#11), *Division by zero*, instead.
+
+> [!NOTE] BETA 1010
+> When *rate* is -1 and *nper* is less than 0, VB6 raises no error; 64-bit VBA raises error [6 (`&H6`)](tb:Errors#6), *Overflow*, instead.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 In this example, the **PV** function returns the present value of an $1,000,000 annuity that will provide $50,000 a year for the next 20 years. Provided are the expected annual percentage rate (`APR`), the total number of payments (`TotPmts`), the amount of each payment (`YrIncome`), the total future value of the investment (`FVal`), and a number that indicates whether each payment is made at the beginning or end of the payment period (`PayType`). Note that `YrIncome` is a negative number because it represents cash paid out from the annuity each year.
diff --git a/docs/Reference/Default/VBA/Financial/Pmt.md b/docs/Reference/Default/VBA/Financial/Pmt.md
index d4a0ba01e..bbee33c0b 100644
--- a/docs/Reference/Default/VBA/Financial/Pmt.md
+++ b/docs/Reference/Default/VBA/Financial/Pmt.md
@@ -15,7 +15,7 @@ Syntax: **Pmt(** *rate*, *nper*, *pv* [ **,** *fv* [ **,** *type* ] ] **)**
 : *required* **Double** specifying interest rate per period. For example, for a car loan at an annual percentage rate (APR) of 10 percent with monthly payments, the rate per period is 0.1/12, or 0.0083.
 
 *nper*
-: *required* **Integer** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
+: *required* **Double** specifying total number of payment periods in the annuity. For example, monthly payments on a four-year car loan total 4 * 12 (or 48) payment periods.
 
 *pv*
 : *required* **Double** specifying present value (or lump sum) that a series of payments to be paid in the future is worth now. For example, when borrowing money to buy a car, the loan amount is the present value to the lender of the monthly car payments to be made.
@@ -32,6 +32,28 @@ The *rate* and *nper* arguments must be calculated by using payment periods expr
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [6 (`&H6`)](tb:Errors#6), *Overflow* | *rate* is -1 and *type* is 1 or more |
+| [11 (`&HB`)](tb:Errors#11), *Division by zero* | *rate* is -2 and *nper* is an even number<br>*nper* is 0 and *rate* is not 0 |
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *nper* and *rate* are both 0 |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *rate*, *nper* or *pv* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *nper* is 0 and *rate* is not 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *nper* and *rate* are both 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
+
 ### Example
 
 This example uses the **Pmt** function to return the monthly payment for a loan over a fixed period. Given are the interest percentage rate per period (`APR / 12`), the total number of payments (`TotPmts`), the present value or principal of the loan (`PVal`), the future value of the loan (`FVal`), and a number that indicates whether the payment is due at the beginning or end of the payment period (`PayType`).
diff --git a/docs/Reference/Default/VBA/Financial/Rate.md b/docs/Reference/Default/VBA/Financial/Rate.md
index b4deadee3..07ef7cdea 100644
--- a/docs/Reference/Default/VBA/Financial/Rate.md
+++ b/docs/Reference/Default/VBA/Financial/Rate.md
@@ -33,7 +33,44 @@ An annuity is a series of fixed cash payments made over a period of time. An ann
 
 For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
 
-**Rate** is calculated by iteration. Starting with the value of *guess*, **Rate** cycles through the calculation until the result is accurate to within 0.00001 percent. If **Rate** can't find a result after 20 tries, it fails. If the default 10 percent fails, try a different value for *guess*.
+**Rate** is calculated by iteration. Starting with the value of *guess*, **Rate** cycles through the calculation until the result is accurate to within 0.00001 percent, and fails if it finds none in 20 tries. If it fails from the default of 10 percent, try a different value for *guess*.
+
+<!-- bug: rate-fails -->
+> [!WARNING] BETA 1010
+> Given a lump sum (a *pmt* of 0) over an even number of periods, **Rate** can return a rate below -1 and raise no error: `Rate(2, 0, 100, -121)` and `Rate(4, 0, 100, -146.41)` return -2.1. VB6 returns 0.1.
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | a rate exists (twinBASIC finds one only for a few annuities, none of them with a *pmt* other than 0)<br>**Rate** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included), or *nper* is 0 or less<br>*nper* is less than 1 and the result is beyond the range of a **Double** |
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *nper* is less than 1 and *pmt* is 0 |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *fv* or *type* is a string that is not a number<br>*fv* or *type* is **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *nper*, *pmt* or *pv* is **Null** |
+
+> [!NOTE] BETA 1010
+> When a rate exists (twinBASIC finds one only for a few annuities, none of them with a *pmt* other than 0), VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When **Rate** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included), or *nper* is 0 or less, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When *nper* is less than 1 and the result is beyond the range of a **Double**, VB6 and 64-bit VBA raise error [6 (`&H6`)](tb:Errors#6), *Overflow*, instead.
+
+> [!NOTE] BETA 1010
+> When *nper* is less than 1 and *pmt* is 0, VB6 and 64-bit VBA raise no error.
+
+> [!NOTE] BETA 1010
+> When *guess* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *guess* is a string that is not a number, or an error value, VB6 and 64-bit VBA raise error [13 (`&HD`)](tb:Errors#13), *Type mismatch*; twinBASIC raises none.
+
+> [!NOTE] BETA 1010
+> When *fv* or *type* is **Null**, VB6 and 64-bit VBA raise error [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Financial/SLN.md b/docs/Reference/Default/VBA/Financial/SLN.md
index 96fd92dcc..3814a1818 100644
--- a/docs/Reference/Default/VBA/Financial/SLN.md
+++ b/docs/Reference/Default/VBA/Financial/SLN.md
@@ -20,7 +20,25 @@ Syntax: **SLN(** *cost*, *salvage*, *life* **)**
 *life*
 : *required* **Double** specifying length of the useful life of the asset.
 
-The depreciation period must be expressed in the same unit as the *life* argument. All arguments must be positive numbers.
+The depreciation period must be expressed in the same unit as the *life* argument.
+
+<!-- VBA: twinBASIC, VB6 and 64-bit VBA take a negative or zero cost or salvage, and a negative life (Common Errors lists what they refuse). All arguments must be positive numbers. -->
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *life* is 0 |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *cost*, *salvage* or *life* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *life* is 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+> [!NOTE] BETA 1010
+> When the result is beyond the range of a **Double** (twinBASIC returns infinity), 64-bit VBA raises error [6 (`&H6`)](tb:Errors#6), *Overflow*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Financial/SYD.md b/docs/Reference/Default/VBA/Financial/SYD.md
index 00f084ce6..e7f414cc3 100644
--- a/docs/Reference/Default/VBA/Financial/SYD.md
+++ b/docs/Reference/Default/VBA/Financial/SYD.md
@@ -23,7 +23,22 @@ Syntax: **SYD(** *cost*, *salvage*, *life*, *period* **)**
 *period*
 : *required* **Double** specifying period for which asset depreciation is calculated.
 
-The *life* and *period* arguments must be expressed in the same units. For example, if *life* is given in months, *period* must also be given in months. All arguments must be positive numbers.
+The *life* and *period* arguments must be expressed in the same units. For example, if *life* is given in months, *period* must also be given in months.
+
+<!-- VBA: twinBASIC, VB6 and 64-bit VBA take a negative or zero cost and a zero salvage (Common Errors lists what they refuse). All arguments must be positive numbers. -->
+
+<!-- errors: generated from errors/VBA.Financial.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *life* is 0 or less, *period* is 0 or less or greater than *life*, or *salvage* is less than 0 |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *cost*, *salvage*, *life* or *period* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *life* is 0 or less, *period* is 0 or less or greater than *life*, or *salvage* is less than 0, VB6 and 64-bit VBA raise error [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument*, instead.
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/Financial/index.md b/docs/Reference/Default/VBA/Financial/index.md
index bfc4e4467..ec8046099 100644
--- a/docs/Reference/Default/VBA/Financial/index.md
+++ b/docs/Reference/Default/VBA/Financial/index.md
@@ -23,7 +23,7 @@ Monthly = -Pmt(APR / 12, 30 * 12, 200000)   ' fixed monthly payment on a 30-year
 
 ## Variable cash flows
 
-For investments whose cash flows vary period to period, three functions take an array of values rather than a single payment amount. [**NPV**](NPV) returns the net present value of the cash flows discounted at a chosen rate; [**IRR**](IRR) returns the internal rate of return --- the discount rate that would make **NPV** zero; and [**MIRR**](MIRR) returns the modified internal rate of return, where outflows and reinvested inflows are discounted at separate rates. The order of values within the array is significant --- element *i* is the cash flow for period *i* --- and the array must contain at least one negative entry (a payment) and one positive entry (a receipt). Like **Rate**, both **IRR** and **MIRR** are computed iteratively and accept an optional *guess*.
+For investments whose cash flows vary period to period, three functions take an array of values rather than a single payment amount. [**NPV**](NPV) returns the net present value of the cash flows discounted at a chosen rate; [**IRR**](IRR) returns the internal rate of return --- the discount rate that would make **NPV** zero; and [**MIRR**](MIRR) returns the modified internal rate of return, where outflows and reinvested inflows are discounted at separate rates. The order of values within the array is significant --- element *i* is the cash flow for period *i* --- and for **IRR** the array must contain at least one negative entry (a payment) and one positive entry (a receipt). Like **Rate**, **IRR** is computed iteratively and accepts an optional *guess*.
 
 ```tb check_build
 Dim CashFlows(0 To 4) As Double
diff --git a/docs/Reference/Default/VBA/HiddenModule/AddClassInstanceFlag.md b/docs/Reference/Default/VBA/HiddenModule/AddClassInstanceFlag.md
index a24be04e7..1aa8bc923 100644
--- a/docs/Reference/Default/VBA/HiddenModule/AddClassInstanceFlag.md
+++ b/docs/Reference/Default/VBA/HiddenModule/AddClassInstanceFlag.md
@@ -56,6 +56,16 @@ The function is provided for code generated in debug mode. It uses special inter
 > [!NOTE] BETA 1010
 > A procedure that calls **InternalGetReturnAddress** fails code generation in a 64-bit build, with or without LLVM, and the project does not build.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Flag* is **Null** |
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *ClassInstance* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [StackOffset](StackOffset), [StackArgsSize](StackArgsSize) functions
diff --git a/docs/Reference/Default/VBA/HiddenModule/AllocMem.md b/docs/Reference/Default/VBA/HiddenModule/AllocMem.md
index 04ddfe79e..1e5d93439 100644
--- a/docs/Reference/Default/VBA/HiddenModule/AllocMem.md
+++ b/docs/Reference/Default/VBA/HiddenModule/AllocMem.md
@@ -15,7 +15,15 @@ Syntax: **AllocMem(** *BytesToAlloc* **)** **As LongPtr**
 
 The contents of the new block are unspecified. Release the block with [**FreeMem**](FreeMem) when no longer needed; passing the address to anything else (e.g. a Win32 `HeapFree`) will not work, since the block is owned by the twinBASIC runtime's heap.
 
-If the allocation fails, **AllocMem** raises a run-time error.
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147024882 (`&H8007000E`)](tb:Errors#-2147024882), *Not enough memory resources are available to complete this operation.* | *BytesToAlloc* is 0 or less<br>in a 32-bit build, there is not enough memory for the block (2,000,000,000 bytes, for one) |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *BytesToAlloc* is **Null** |
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md b/docs/Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md
index 51d9e9bdc..31dd91af0 100644
--- a/docs/Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md
+++ b/docs/Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md
@@ -18,6 +18,23 @@ Syntax: **ConvertIconToBitmap(** *IconPicture* [ **,** *BackColor* ] **)** **As
 
 The returned picture is a fresh bitmap-typed **stdole.StdPicture** with the icon rasterised on top of the chosen background. The original icon picture is unchanged.
 
+<!-- bug: nothing-argument-crashes -->
+> [!WARNING] BETA 1010
+> An *IconPicture* of **Nothing** ends the program with an access violation, in a 32-bit and a 64-bit build alike.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *IconPicture* is not an icon: a bitmap, a picture with no image, or an object that is not a picture |
+| [5 (`&H5`)](tb:Errors#5), *Invalid procedure call or argument* | *BackColor*'s high byte is other than 0, 1, 2 or &H80 (-1, for one), or it is a system colour above &H8000001E |
+| [13 (`&HD`)](tb:Errors#13), *Type mismatch* | *BackColor* is a string that does not hold a number |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *BackColor* is **Null** |
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *IconPicture* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/HiddenModule/CreateGUID.md b/docs/Reference/Default/VBA/HiddenModule/CreateGUID.md
index 87d101086..c48056614 100644
--- a/docs/Reference/Default/VBA/HiddenModule/CreateGUID.md
+++ b/docs/Reference/Default/VBA/HiddenModule/CreateGUID.md
@@ -6,11 +6,11 @@ permalink: /tB/Modules/HiddenModule/CreateGUID
 # CreateGUID
 {: .no_toc }
 
-Generates a fresh GUID and returns it as a registry-formatted string.
+Generates a fresh GUID and returns it as a string.
 
 Syntax: **CreateGUID()** **As String**
 
-The result is a fresh, unique GUID in the form `{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}` --- the same format used by **InterfaceId**, **ClassId**, and the like. Each call returns a different value.
+The result is a fresh, unique GUID of 36 characters in the form `xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`, without braces --- the form the **InterfaceId** and **ClassId** attributes take. Each call returns a different value.
 
 This is a thin wrapper over the operating system's GUID generator (`CoCreateGuid` on Windows). The resulting GUID is suitable for use as an interface or class identifier; it is not, however, a cryptographically random number --- do not use it where unpredictability matters.
 
@@ -18,7 +18,7 @@ This is a thin wrapper over the operating system's GUID generator (`CoCreateGuid
 
 ```tb check_build
 Debug.Print CreateGUID()
-' {2A1B6F2C-4D9F-4D5E-9C8A-EE9C8B5F3DCE}
+' 2A1B6F2C-4D9F-4D5E-9C8A-EE9C8B5F3DCE
 ```
 
 ### See Also
diff --git a/docs/Reference/Default/VBA/HiddenModule/CreateStdPictureFromHandle.md b/docs/Reference/Default/VBA/HiddenModule/CreateStdPictureFromHandle.md
index 3dd8ad61b..4bbe1b7bc 100644
--- a/docs/Reference/Default/VBA/HiddenModule/CreateStdPictureFromHandle.md
+++ b/docs/Reference/Default/VBA/HiddenModule/CreateStdPictureFromHandle.md
@@ -21,6 +21,19 @@ Syntax: **CreateStdPictureFromHandle(** *Handle* **,** *Type* **,** *TakeOwnersh
 
 The result is a regular **stdole.StdPicture** equivalent to one returned by **LoadPicture**, suitable for assignment to a **Picture** property.
 
+With `vbPicTypeBitmap`, *Handle* is not checked: 0, or a handle that is not a bitmap's, gives a picture and raises nothing.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *Handle* is not of the kind *Type* names: 0 for an icon, or a bitmap for an icon, a metafile or an enhanced metafile |
+| [-2147418113 (`&H8000FFFF`)](tb:Errors#-2147418113), *Catastrophic failure* | *Type* is less than 0 or greater than 4 |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | an argument is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [PictureToByteArray](PictureToByteArray) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/Eval.md b/docs/Reference/Default/VBA/HiddenModule/Eval.md
index 3db1f4345..f206541c3 100644
--- a/docs/Reference/Default/VBA/HiddenModule/Eval.md
+++ b/docs/Reference/Default/VBA/HiddenModule/Eval.md
@@ -17,6 +17,30 @@ A fresh [**TbExpressionService**](../TbExpressionService/) is built for every ca
 
 For repeated evaluation of the same source, or for expressions that need to see application objects, construct the service explicitly and reuse a compiled [**ITbExpression**](../TbExpressionService/#itbexpression-interface).
 
+<!-- bug: expression-service-dangling-tokens -->
+> [!WARNING] BETA 1010
+> Some malformed expressions are not refused: the part that cannot be read is left out, and no error is raised. `Eval("2 +")`, `Eval("2 Mod")`, `Eval("(2")` and `Eval("2)")` each return 2.
+
+<!-- bug: expression-service-error-numbers -->
+> [!NOTE] BETA 1010
+> **Eval** raises -2147467259 for any error inside the expression: the error's own number and description are lost. `Eval("1 / 0")` raises -2147467259, not 11.
+
+> [!NOTE] BETA 1010
+> **Eval** also raises -2147467259 for an expression whose value is an **Error** value, such as `Eval("CVErr(5)")`, and for **Len** of **Null**, which outside an expression returns **Null**.
+
+> [!NOTE] BETA 1010
+> In a built program, the first error the expression service raises has the description *Automation error*, and every later one *Unspecified error*. In a run from the IDE, every one has the description *Automation error*.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *Expression* is a zero-length string or is not an expression, or it names something the standard library does not have<br>evaluating *Expression* raises an error, whatever its number: division by zero, an overflow, a type mismatch, an argument a function refuses<br>the value of *Expression* is an **Error** value, or *Expression* calls **Len** with **Null** |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Expression* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/HiddenModule/FreeMem.md b/docs/Reference/Default/VBA/HiddenModule/FreeMem.md
index 8266b9a82..8bb76d498 100644
--- a/docs/Reference/Default/VBA/HiddenModule/FreeMem.md
+++ b/docs/Reference/Default/VBA/HiddenModule/FreeMem.md
@@ -13,7 +13,16 @@ Syntax: **FreeMem** *MemPointer*
 *MemPointer*
 : *required* **LongPtr**. The address returned by a previous call to [**AllocMem**](AllocMem).
 
-The pointer is invalid after the call returns. Passing a pointer that did not come from **AllocMem** --- including zero, or one that has already been freed --- has undefined behaviour.
+The pointer is invalid after the call returns. Passing a pointer that did not come from **AllocMem**, or one that has already been freed, has undefined behaviour. A *MemPointer* of 0 does nothing.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *MemPointer* is **Null** |
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetDeclaredTypeIid.md b/docs/Reference/Default/VBA/HiddenModule/GetDeclaredTypeIid.md
index 163cd412f..7ea1730b8 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetDeclaredTypeIid.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetDeclaredTypeIid.md
@@ -15,14 +15,12 @@ Syntax: **GetDeclaredTypeIid(Of** *T* **)()** **As String**
 
 The IID is returned in registry format (`{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}`). The lookup happens at compile time and the result is stored in the generated code as a string literal --- there is no run-time call.
 
-Useful when calling [**vbaCastObj**](vbaCastObj) or any API that takes an interface IID as a string.
+Useful with any API that takes an interface ID as a string. [**vbaCastObj**](vbaCastObj) does not: it takes the address of a **GUID** structure.
 
 ### Example
 
 ```tb check_build
-Dim SomeObj As Object
-Dim Iid As String = GetDeclaredTypeIid(Of stdole.IPicture)()
-Dim AsPic As IUnknown = vbaCastObj(SomeObj, Iid)
+Debug.Print GetDeclaredTypeIid(Of stdole.IPicture)()    ' {7BF80980-BF32-101A-8BBB-00AA00300CAB}
 ```
 
 ### See Also
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetInheritedOwner.md b/docs/Reference/Default/VBA/HiddenModule/GetInheritedOwner.md
index c2ecd5b77..6f611abc1 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetInheritedOwner.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetInheritedOwner.md
@@ -15,6 +15,19 @@ Syntax: **GetInheritedOwner(** *Value* **)** **As Object**
 
 For controls that participate in a control-container hierarchy, the inherited owner is the topmost owning object that supplies ambient settings --- typically the form. Returns **Nothing** when no inherited owner is set.
 
+<!-- bug: nothing-argument-crashes -->
+> [!WARNING] BETA 1010
+> A *Value* of **Nothing**, or an object that is not a control, ends the program with an access violation: **Nothing** and a **Collection** in a 32-bit and a 64-bit build, a **Scripting.Dictionary** in a 64-bit build.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example reads the topmost container of a control and reports its type.
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetMem1.md b/docs/Reference/Default/VBA/HiddenModule/GetMem1.md
index 15c004d7a..e4f211e38 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetMem1.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetMem1.md
@@ -18,6 +18,15 @@ Syntax: **GetMem1** *Address* **,** *retVal*
 
 The address is read directly with no bounds or alignment check. Reading from an address that does not belong to the process, or from one that has been freed, will crash the host.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build check_run
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetMem2.md b/docs/Reference/Default/VBA/HiddenModule/GetMem2.md
index 663234d8d..d53feeefb 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetMem2.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetMem2.md
@@ -18,6 +18,15 @@ Syntax: **GetMem2** *Address* **,** *retVal*
 
 The bytes are interpreted in the host's native byte order --- little-endian on x86 and x64. The address is read directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes a 16-bit value to a buffer and reads it back with **GetMem2**.
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetMem4.md b/docs/Reference/Default/VBA/HiddenModule/GetMem4.md
index 884a0a405..de1ca8ebf 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetMem4.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetMem4.md
@@ -18,6 +18,15 @@ Syntax: **GetMem4** *Address* **,** *retVal*
 
 The bytes are interpreted in the host's native byte order --- little-endian on x86 and x64. The address is read directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes a 32-bit value to a buffer and reads it back with **GetMem4**.
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetMem8.md b/docs/Reference/Default/VBA/HiddenModule/GetMem8.md
index 9babccec0..ba062c592 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetMem8.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetMem8.md
@@ -20,6 +20,15 @@ Syntax: **GetMem8** *Address* **,** *retVal*
 
 The address is read directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes an 8-byte value to a buffer and reads it back with **GetMem8**.
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetMemPtr.md b/docs/Reference/Default/VBA/HiddenModule/GetMemPtr.md
index 8bb60ab29..d58480c89 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetMemPtr.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetMemPtr.md
@@ -18,6 +18,15 @@ Syntax: **GetMemPtr** *Address* **,** *retVal*
 
 The number of bytes read matches the host's pointer width --- four bytes in 32-bit builds, eight bytes in 64-bit builds. The bytes are interpreted in the host's native byte order. The address is read directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetNameFromDispID.md b/docs/Reference/Default/VBA/HiddenModule/GetNameFromDispID.md
index 32ae0737a..144e1a25b 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetNameFromDispID.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetNameFromDispID.md
@@ -31,14 +31,7 @@ Debug.Print GetNameFromDispID(Table, 2)     ' Count
 Debug.Print GetNameFromDispID(Table, -4)    ' _NewEnum
 ```
 
-The call raises an error when no name can be returned:
-
-| Case | Error |
-|------|-------|
-| *Object* is **Nothing** | -2147467261, *Invalid pointer* |
-| *Object* has no type information (a **Collection**, for one) | -2147467263, *Not implemented* |
-| A member of a twinBASIC class has no such ID | 5, *Invalid procedure call or argument* |
-| A member of a type-library object, such as a **Scripting.Dictionary**, has no such ID | -2147319765, *Element not found.* |
+The call raises an error when no name can be returned; [Common Errors](#common-errors) lists them. For an object of a class that twinBASIC compiles, a *DispID* that is no member's raises error 5, *Invalid procedure call or argument*, and -4 raises -2147319765, *Element not found.*, when the class has no enumerator member.
 
 The **VB** package's **PropertyPage** calls it when the property sheet asks a page to edit a property by dispatch ID, to find the property's name.
 
@@ -65,6 +58,20 @@ Sub EditProperty(ByVal Control As Object, ByVal PropertyDispId As Long)
 End Sub
 ```
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467261 (`&H80004003`)](tb:Errors#-2147467261), *Invalid pointer* | *Object* is **Nothing** |
+| [-2147467263 (`&H80004001`)](tb:Errors#-2147467263), *Not implemented* | **GetNameFromDispID** is given an object that has no type information, such as a **Collection** |
+| [-2147467262 (`&H80004002`)](tb:Errors#-2147467262), *No such interface supported* | **GetNameFromDispID** is given an object that does not support **IDispatch**, such as a **TbExpressionService**<br>**ShowPropertyPageEditor** is given an object that has no property pages |
+| [-2147319765 (`&H8002802B`)](tb:Errors#-2147319765), *Element not found.* | **GetNameFromDispID** is given an object described by a type library, such as a **Scripting.Dictionary**, and a *DispID* that is no member's |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Caption* or *DispID* is **Null** |
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *Object* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [PropertyPage](../../Packages/VB/PropertyPage/) class
diff --git a/docs/Reference/Default/VBA/HiddenModule/GetShortcutTextByEnum.md b/docs/Reference/Default/VBA/HiddenModule/GetShortcutTextByEnum.md
index 2aaac071c..54755b887 100644
--- a/docs/Reference/Default/VBA/HiddenModule/GetShortcutTextByEnum.md
+++ b/docs/Reference/Default/VBA/HiddenModule/GetShortcutTextByEnum.md
@@ -15,6 +15,15 @@ Syntax: **GetShortcutTextByEnum(** *ShortcutEnumId* **)** **As String**
 
 The returned string is the user-facing label for the shortcut --- e.g. `"Ctrl+S"`, `"Ctrl+Shift+P"`, `"F5"` --- formatted in the system UI language. Returns an empty string for an unknown identifier.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *ShortcutEnumId* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [RuntimeCreateGetMessageHook](RuntimeCreateGetMessageHook) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange32.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange32.md
index 0b270de49..730afcc06 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange32.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange32.md
@@ -21,6 +21,15 @@ Syntax: **InterlockedCompareExchange32(** *Target* **,** *NewValue* **,** *OldVa
 
 The compare-and-swap happens as one atomic operation. The return value is the value that was in *Target* at the start of the call --- equal to *OldValueCompare* on success, anything else on failure (in which case *Target* is left unchanged). Wraps the Win32 `InterlockedCompareExchange` intrinsic.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *NewValue* or *OldValueCompare* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [InterlockedCompareExchange64](InterlockedCompareExchange64) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange64.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange64.md
index 96b3503b6..7c3c853c4 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange64.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchange64.md
@@ -21,6 +21,15 @@ Syntax: **InterlockedCompareExchange64(** *Target* **,** *NewValue* **,** *OldVa
 
 The compare-and-swap happens as one atomic operation. The return value is the value that was in *Target* at the start of the call --- equal to *OldValueCompare* on success, anything else on failure (in which case *Target* is left unchanged). Wraps the Win32 `InterlockedCompareExchange64` intrinsic.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *NewValue* or *OldValueCompare* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [InterlockedCompareExchange32](InterlockedCompareExchange32) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchangePointer.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchangePointer.md
index 8687610ba..53804149f 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchangePointer.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedCompareExchangePointer.md
@@ -21,6 +21,15 @@ Syntax: **InterlockedCompareExchangePointer(** *Target* **,** *NewValue* **,** *
 
 The compare-and-swap happens as one atomic operation. The return value is the value that was in *Target* at the start of the call --- equal to *OldValueCompare* on success, anything else on failure (in which case *Target* is left unchanged). Wraps the Win32 `InterlockedCompareExchangePointer` intrinsic.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *NewValue* or *OldValueCompare* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedDecrement32.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedDecrement32.md
index 863c3ecb8..15b7335ef 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedDecrement32.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedDecrement32.md
@@ -13,7 +13,7 @@ Syntax: **InterlockedDecrement32(** *Target* **)** **As Long**
 *Target*
 : *required* **Long**. The 32-bit variable to decrement, passed by reference.
 
-The read, subtract, and write happen as one atomic operation. The return value is the post-decrement value of *Target* --- testing against zero is the canonical way to spot the last release of a refcounted resource. Wraps the Win32 `InterlockedDecrement` intrinsic.
+The read, subtract, and write happen as one atomic operation. The return value is the post-decrement value of *Target* --- testing against zero is the canonical way to spot the last release of a refcounted resource. Wraps the Win32 `InterlockedDecrement` intrinsic. No overflow error is raised: decrementing -2,147,483,648 gives 2,147,483,647.
 
 ### See Also
 
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedExchangePointer.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedExchangePointer.md
index 5cf89038f..81041a781 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedExchangePointer.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedExchangePointer.md
@@ -18,6 +18,15 @@ Syntax: **InterlockedExchangePointer(** *Target* **,** *NewValue* **)** **As Lon
 
 The store and the read of the prior value happen as a single atomic operation, observable by other threads as either fully-before or fully-after the call. Wraps the Win32 `InterlockedExchangePointer` intrinsic.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *NewValue* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [InterlockedCompareExchangePointer](InterlockedCompareExchangePointer) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/InterlockedIncrement32.md b/docs/Reference/Default/VBA/HiddenModule/InterlockedIncrement32.md
index dd5ba5ebe..4cf1a58ed 100644
--- a/docs/Reference/Default/VBA/HiddenModule/InterlockedIncrement32.md
+++ b/docs/Reference/Default/VBA/HiddenModule/InterlockedIncrement32.md
@@ -13,7 +13,7 @@ Syntax: **InterlockedIncrement32(** *Target* **)** **As Long**
 *Target*
 : *required* **Long**. The 32-bit variable to increment, passed by reference.
 
-The read, add, and write happen as one atomic operation. The return value is the post-increment value of *Target*. Wraps the Win32 `InterlockedIncrement` intrinsic.
+The read, add, and write happen as one atomic operation. The return value is the post-increment value of *Target*. Wraps the Win32 `InterlockedIncrement` intrinsic. No overflow error is raised: incrementing 2,147,483,647 gives -2,147,483,648.
 
 ### See Also
 
diff --git a/docs/Reference/Default/VBA/HiddenModule/PictureToByteArray.md b/docs/Reference/Default/VBA/HiddenModule/PictureToByteArray.md
index dc5d1171c..3632bb907 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PictureToByteArray.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PictureToByteArray.md
@@ -15,7 +15,17 @@ Syntax: **PictureToByteArray(** *Picture* **)** **As Variant**
 
 The result is a **Variant** wrapping a `Byte()` array containing the bytes the picture would write to a stream via **IPersistStream**. The companion deserialiser is the global **LoadPicture**, which accepts a byte array as input and returns a fresh picture.
 
-Returns an empty array if *Picture* is **Nothing**.
+If *Picture* is **Nothing**, the result is a **Byte** array with no elements and no bounds: [**UBound**](../Information/UBound) of it raises error 9, *Subscript out of range*.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467262 (`&H80004002`)](tb:Errors#-2147467262), *No such interface supported* | *Picture* is an object that is not a picture |
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *Picture* is **Null** |
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/HiddenModule/PutMem1.md b/docs/Reference/Default/VBA/HiddenModule/PutMem1.md
index 9f9944162..f70320c1b 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PutMem1.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PutMem1.md
@@ -18,6 +18,15 @@ Syntax: **PutMem1** *Address* **,** *Value*
 
 The address is written directly with no bounds or alignment check. Writing to an address that does not belong to the process, or one that points into read-only memory, will crash the host.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* or *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes a single byte to a buffer and reads it back.
diff --git a/docs/Reference/Default/VBA/HiddenModule/PutMem2.md b/docs/Reference/Default/VBA/HiddenModule/PutMem2.md
index 6840bf067..c15e0ee41 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PutMem2.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PutMem2.md
@@ -18,6 +18,15 @@ Syntax: **PutMem2** *Address* **,** *Value*
 
 The bytes are written in the host's native byte order --- little-endian on x86 and x64. The address is written directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* or *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes a 16-bit value to a buffer and reads it back.
diff --git a/docs/Reference/Default/VBA/HiddenModule/PutMem4.md b/docs/Reference/Default/VBA/HiddenModule/PutMem4.md
index 15eb18875..696ec3453 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PutMem4.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PutMem4.md
@@ -18,6 +18,15 @@ Syntax: **PutMem4** *Address* **,** *Value*
 
 The bytes are written in the host's native byte order --- little-endian on x86 and x64. The address is written directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* or *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes a 32-bit value to a buffer and reads it back.
diff --git a/docs/Reference/Default/VBA/HiddenModule/PutMem8.md b/docs/Reference/Default/VBA/HiddenModule/PutMem8.md
index 5b73ebcf5..35c9e46aa 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PutMem8.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PutMem8.md
@@ -20,6 +20,15 @@ Syntax: **PutMem8** *Address* **,** *Value*
 
 The address is written directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* or *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example writes an 8-byte value to a buffer and reads it back.
diff --git a/docs/Reference/Default/VBA/HiddenModule/PutMemPtr.md b/docs/Reference/Default/VBA/HiddenModule/PutMemPtr.md
index f6859b90c..e832b843a 100644
--- a/docs/Reference/Default/VBA/HiddenModule/PutMemPtr.md
+++ b/docs/Reference/Default/VBA/HiddenModule/PutMemPtr.md
@@ -18,6 +18,15 @@ Syntax: **PutMemPtr** *Address* **,** *Value*
 
 The number of bytes written matches the host's pointer width --- four bytes in 32-bit builds, eight bytes in 64-bit builds. The bytes are written in the host's native byte order. The address is written directly with no bounds or alignment check.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* or *Value* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example stores a pointer in a buffer and reads it back.
diff --git a/docs/Reference/Default/VBA/HiddenModule/RegisterMessage.md b/docs/Reference/Default/VBA/HiddenModule/RegisterMessage.md
index ff4233074..0615e5b1b 100644
--- a/docs/Reference/Default/VBA/HiddenModule/RegisterMessage.md
+++ b/docs/Reference/Default/VBA/HiddenModule/RegisterMessage.md
@@ -27,6 +27,17 @@ Syntax: *hook*.**RegisterMessage** *ParentHWND* **,** *Mode* **,** *MessageType*
 
 The subscription is recorded but does not start firing until [**Start**](Start) is called on the hook. Existing subscriptions are not disturbed by adding new ones.
 
+**RegisterMessage** checks none of its arguments: a window that does not exist, a *Mode* that is not one of the three values, and the same subscription given twice are accepted.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *ParentHWND*, *Mode* or *MessageType* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build inherits=Form
diff --git a/docs/Reference/Default/VBA/HiddenModule/RuntimeCreateGetMessageHook.md b/docs/Reference/Default/VBA/HiddenModule/RuntimeCreateGetMessageHook.md
index 76202d2a1..a06eadfd0 100644
--- a/docs/Reference/Default/VBA/HiddenModule/RuntimeCreateGetMessageHook.md
+++ b/docs/Reference/Default/VBA/HiddenModule/RuntimeCreateGetMessageHook.md
@@ -12,6 +12,10 @@ Syntax: **RuntimeCreateGetMessageHook()** **As IGetMessageHook**
 
 The returned hook starts dormant. Subscribe a callback for one or more message types with [**RegisterMessage**](RegisterMessage), then call [**Start**](Start) to activate the subscriptions and [**Stop**](Stop) to remove them.
 
+<!-- bug: nothing-argument-crashes -->
+> [!WARNING] BETA 1010
+> Assigning the result to a **Variant** without **Set**, as in `V = RuntimeCreateGetMessageHook()`, ends the program with an access violation, in a 32-bit and a 64-bit build alike. Assign it with **Set**, or to a variable declared **As IGetMessageHook**.
+
 ### Example
 
 ```tb check_build inherits=Form
diff --git a/docs/Reference/Default/VBA/HiddenModule/SetThreadGlobalErrorTrap.md b/docs/Reference/Default/VBA/HiddenModule/SetThreadGlobalErrorTrap.md
index 4cf8af3de..e3facbbdc 100644
--- a/docs/Reference/Default/VBA/HiddenModule/SetThreadGlobalErrorTrap.md
+++ b/docs/Reference/Default/VBA/HiddenModule/SetThreadGlobalErrorTrap.md
@@ -17,6 +17,15 @@ The trap supplements ordinary `On Error` handling: it sees errors that escape th
 
 Only one trap is active per thread; setting a new one replaces the previous.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *CallbackAddress* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [On Error](../../Core/On-Error) statement
diff --git a/docs/Reference/Default/VBA/HiddenModule/index.md b/docs/Reference/Default/VBA/HiddenModule/index.md
index 5ebd18c49..0509839ae 100644
--- a/docs/Reference/Default/VBA/HiddenModule/index.md
+++ b/docs/Reference/Default/VBA/HiddenModule/index.md
@@ -32,7 +32,7 @@ FreeMem Buffer
 
 ## Object references and casting
 
-[**vbaObjAddref**](vbaObjAddref), [**vbaObjSet**](vbaObjSet), and [**vbaObjSetAddref**](vbaObjSetAddref) manipulate COM reference counts directly. [**vbaCastObj**](vbaCastObj) returns the object reinterpreted as another COM interface, given its IID. [**CreateGUID**](CreateGUID) generates a fresh GUID and returns it as a registry-formatted string.
+[**vbaObjAddref**](vbaObjAddref), [**vbaObjSet**](vbaObjSet), and [**vbaObjSetAddref**](vbaObjSetAddref) manipulate COM reference counts directly. [**vbaCastObj**](vbaCastObj) returns the object reinterpreted as another COM interface, given its IID. [**CreateGUID**](CreateGUID) generates a fresh GUID and returns it as a string.
 
 ## Atomic operations
 
@@ -65,7 +65,7 @@ Five members are declared **Hidden** and **Restricted**, so IntelliSense lists l
 - [AddClassInstanceFlag](AddClassInstanceFlag) -- sets a flag on a class instance
 - [AllocMem](AllocMem) -- allocates a block of native memory and returns its address
 - [ConvertIconToBitmap](ConvertIconToBitmap) -- converts an icon picture to a bitmap picture
-- [CreateGUID](CreateGUID) -- generates a fresh GUID and returns it as a registry-formatted string
+- [CreateGUID](CreateGUID) -- generates a fresh GUID and returns it as a string
 - [CreateStdPictureFromHandle](CreateStdPictureFromHandle) -- wraps a GDI bitmap or icon handle in an **stdole.StdPicture**
 - [Emit](Emit) -- injects custom **Byte** values into the codegen stream of the enclosing procedure
 - [EmitAny](EmitAny) -- injects custom typed values into the codegen stream of the enclosing procedure
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaCastObj.md b/docs/Reference/Default/VBA/HiddenModule/vbaCastObj.md
index 23e670206..e2a17b0a0 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaCastObj.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaCastObj.md
@@ -6,7 +6,7 @@ permalink: /tB/Modules/HiddenModule/vbaCastObj
 # vbaCastObj
 {: .no_toc }
 
-Returns an object reinterpreted as another COM interface, given its IID, or **Nothing** if the object does not implement that interface.
+Returns an object reinterpreted as another COM interface, given its IID.
 
 Syntax: **vbaCastObj(** *Obj* **,** *IID* **)** **As IUnknown**
 
@@ -14,20 +14,49 @@ Syntax: **vbaCastObj(** *Obj* **,** *IID* **)** **As IUnknown**
 : *required* **stdole.IUnknown**. The object to cast.
 
 *IID*
-: *required* **Any**. The interface ID to query for --- accepted as a 16-byte **GUID** structure or as a **String** in registry format (`{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}`).
+: *required* **Any**. The address of the interface ID to query for: a 16-byte **GUID** structure, its address given with [**VarPtr**](../Information/VarPtr).
 
-A direct wrapper over **IUnknown::QueryInterface**: the object is asked whether it implements the requested interface, and if so a reference to that interface is returned. If not, **Nothing** is returned.
+A direct wrapper over **IUnknown::QueryInterface**, as VB6's runtime function `__vbaCastObj` is: the object is asked whether it implements the requested interface, and if so a reference to that interface is returned. If not, error 13, *Type mismatch*, is raised. If *Obj* is **Nothing**, the result is **Nothing**.
+
+*IID* is read as the address of a **GUID**. A **String** is not converted: its text is not an interface ID, as `"{00000000-0000-0000-C000-000000000046}"` is not. A **GUID** variable passed itself, rather than its address, ends a 32-bit program with an access violation.
+
+<!-- bug: vbacastobj-no-type-mismatch -->
+> [!WARNING] BETA 1010
+> **vbaCastObj** raises no error when *Obj* does not have the interface, or when *IID* is a **String**: it returns **Nothing**.
+
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [424 (`&H1A8`)](tb:Errors#424), *Object required* | *Obj* is **Null** |
+
+> [!NOTE] BETA 1010
+> When *Obj* does not have the interface *IID* names, or *IID* is a **String**, whose text is not read as an interface ID, VB6 raises error [13 (`&HD`)](tb:Errors#13), *Type mismatch*; twinBASIC raises none.
+
+<!-- /errors -->
 
 ### Example
 
+This example asks an object for **IPicture**, whose interface ID is `{7BF80980-BF32-101A-8BBB-00AA00300CAB}`.
+
 ```tb check_build
-Const IID_IPicture As String = "{7BF80980-BF32-101A-8BBB-00AA00300CAB}"
+Private Type InterfaceGuid
+    Data1 As Long
+    Data2 As Integer
+    Data3 As Integer
+    Data4(0 To 7) As Byte
+End Type
 
-Dim Pic As Object = LoadPicture("logo.bmp")
-Dim AsPicture As IUnknown = vbaCastObj(Pic, IID_IPicture)
-If Not AsPicture Is Nothing Then
-    ' Use AsPicture as an IPicture.
-End If
+Function AsPicture(ByVal Obj As Object) As IUnknown
+    Dim Iid As InterfaceGuid
+    Iid.Data1 = &H7BF80980
+    Iid.Data2 = &HBF32
+    Iid.Data3 = &H101A
+    Iid.Data4(0) = &H8B: Iid.Data4(1) = &HBB: Iid.Data4(2) = &H00: Iid.Data4(3) = &HAA
+    Iid.Data4(4) = &H00: Iid.Data4(5) = &H30: Iid.Data4(6) = &H0C: Iid.Data4(7) = &HAB
+    Set AsPicture = vbaCastObj(Obj, VarPtr(Iid))    ' error 13 if Obj is not a picture
+End Function
 ```
 
 ### See Also
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytes.md b/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytes.md
index 59c3c1e03..2d7b30035 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytes.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytes.md
@@ -21,6 +21,15 @@ Syntax: **vbaCopyBytes(** *Length* **,** *Dest* **,** *Src* **)** **As LongPtr**
 
 The behaviour for overlapping ranges is unspecified --- use a temporary buffer if the ranges may overlap. The return value is *Dest* (the same address that was passed in), provided as a convenience for chaining.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | an argument is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 ```tb check_build
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytesZero.md b/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytesZero.md
index f8314ff38..d3b754a4f 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytesZero.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaCopyBytesZero.md
@@ -21,6 +21,15 @@ Syntax: **vbaCopyBytesZero(** *Length* **,** *Dest* **,** *Src* **)** **As LongP
 
 Equivalent to a [**vbaCopyBytes**](vbaCopyBytes) followed by a memory clear of the source. Useful when moving an owning resource (a BSTR, an interface pointer) without leaving a duplicate behind. The return value is *Dest*.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | an argument is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example copies four bytes from one buffer to another, then confirms the source is zeroed.
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaObjAddref.md b/docs/Reference/Default/VBA/HiddenModule/vbaObjAddref.md
index 4e74473e3..c69f74b76 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaObjAddref.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaObjAddref.md
@@ -17,6 +17,15 @@ The reference count of the object is incremented by one. The runtime does not va
 
 This is a low-level primitive. Ordinary code does not need it --- assigning to an **Object** variable already addrefs.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *Address* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [vbaObjSet](vbaObjSet) function
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaObjSet.md b/docs/Reference/Default/VBA/HiddenModule/vbaObjSet.md
index 5d056e5d6..7093cb24e 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaObjSet.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaObjSet.md
@@ -20,6 +20,15 @@ This is the move-without-addref primitive --- used to wrap a freshly-handed-out
 
 The return value mirrors the assigned pointer.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *SrcObjPtr* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [vbaObjSetAddref](vbaObjSetAddref) function -- copy-with-addref counterpart
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaObjSetAddref.md b/docs/Reference/Default/VBA/HiddenModule/vbaObjSetAddref.md
index 5badda60a..6603f0a79 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaObjSetAddref.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaObjSetAddref.md
@@ -20,6 +20,15 @@ This is the copy-with-addref primitive --- equivalent to a regular `Set DstObjec
 
 The return value mirrors the assigned pointer.
 
+<!-- errors: generated from errors/VBA.HiddenModule.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *SrcObjPtr* is **Null** |
+
+<!-- /errors -->
+
 ### See Also
 
 - [vbaObjSet](vbaObjSet) function -- move-without-addref counterpart
diff --git a/docs/Reference/Default/VBA/HiddenModule/vbaRefVarAry.md b/docs/Reference/Default/VBA/HiddenModule/vbaRefVarAry.md
index 416516103..cbc96f8c9 100644
--- a/docs/Reference/Default/VBA/HiddenModule/vbaRefVarAry.md
+++ b/docs/Reference/Default/VBA/HiddenModule/vbaRefVarAry.md
@@ -15,7 +15,7 @@ Syntax: **vbaRefVarAry(** *Variant* **)** **As LongPtr**
 
 The returned address is the location of the **SAFEARRAY*** field inside the **Variant** --- that is, the dereference yields the **SAFEARRAY** pointer that the **Variant** wraps. Useful when calling Win32 APIs that expect to receive or fill a **SAFEARRAY** through a `VARIANT*` argument.
 
-If *Variant* does not contain an array, the result is undefined.
+If *Variant* does not contain an array, the result is undefined, and no error is raised.
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinder.md b/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinder.md
index d5c6f85fc..e595e9efd 100644
--- a/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinder.md
+++ b/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinder.md
@@ -22,6 +22,10 @@ Use **AddCustomBinder** when [**AddCustomBinderObject**](AddCustomBinderObject)
 
 The engine calls [**Bind**](Bind) on each registered custom binder during compilation, once per unresolved symbol. The first binder that returns a non-**Nothing** result wins. Multiple custom binders can be registered with one service, and they are consulted in registration order.
 
+<!-- bug: nothing-argument-crashes -->
+> [!WARNING] BETA 1010
+> A *customBinder* of **Nothing** ends the program with an access violation, in a 32-bit and a 64-bit build alike.
+
 ### Example
 
 This example registers a class instance as both a property source (via [**AddCustomBinderObject**](AddCustomBinderObject) with [**IsAppObject**](./#IsAppObject)) and a custom binder. Bare symbols in the expression are first looked up as members of `Me` via the property source; whatever isn't matched there falls through to `Me.Bind`, which can resolve it dynamically --- for example, against a live recordset.
diff --git a/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinderObject.md b/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinderObject.md
index cc3ebb5e6..c0840774c 100644
--- a/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinderObject.md
+++ b/docs/Reference/Default/VBA/TbExpressionService/AddCustomBinderObject.md
@@ -28,6 +28,19 @@ Member resolution is performed by name through the standard COM/IDispatch protoc
 
 Multiple objects can be bound to the same service, each under its own *name*. They are consulted in the order they were added.
 
+<!-- bug: nothing-argument-crashes -->
+> [!WARNING] BETA 1010
+> An *object* of **Nothing** ends the program with an access violation, in a 32-bit and a 64-bit build alike.
+
+<!-- errors: generated from errors/VBA.TbExpressionService.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *name* or *flags* is **Null** |
+
+<!-- /errors -->
+
 ### Example
 
 This example exposes the host's report object so that an expression can refer to its properties either by qualified name or by bare name.
diff --git a/docs/Reference/Default/VBA/TbExpressionService/Compile.md b/docs/Reference/Default/VBA/TbExpressionService/Compile.md
index ec1d6197e..9a386c3c8 100644
--- a/docs/Reference/Default/VBA/TbExpressionService/Compile.md
+++ b/docs/Reference/Default/VBA/TbExpressionService/Compile.md
@@ -20,11 +20,28 @@ Syntax: *service*.**Compile(** *expression* **)**
 
 The return value is an [**ITbExpression**](./#itbexpression-interface). Calling [**Evaluate**](Evaluate) on it runs the expression and produces the current value; the same instance can be evaluated as many times as needed.
 
-Symbols referenced in *expression* --- function names, object members, properties --- are resolved against the binders registered with *service* at the time of the call. At least one binder must be registered before **Compile** is called; the most common starting point is [**AddStdLibraryBinder**](AddStdLibraryBinder), which exposes the standard runtime library.
+Symbols referenced in *expression* --- function names, object members, properties --- are resolved against the binders registered with *service* at the time of the call. Without a binder only an expression that names nothing compiles, such as `"1 + 1"`; the most common starting point is [**AddStdLibraryBinder**](AddStdLibraryBinder), which exposes the standard runtime library.
 
 Compilation is the relatively expensive step; evaluation reuses the compiled form. When a piece of source text will be used for repeated evaluation --- a formula column refreshed every row, a watch expression sampled in a debugger --- compile it once and keep the **ITbExpression** around.
 
-If *expression* is malformed, or references a symbol that no registered binder can resolve, **Compile** raises a run-time error.
+An expression that compiles can still fail when it is evaluated: `"1 / 0"` compiles, and [**Evaluate**](Evaluate) raises the error.
+
+<!-- bug: expression-service-dangling-tokens -->
+> [!WARNING] BETA 1010
+> Some malformed expressions are not refused: the part that cannot be read is left out, and no error is raised. `"2 +"`, `"2 Mod"`, `"(2"` and `"2)"` each compile to an expression whose value is 2.
+
+> [!NOTE] BETA 1010
+> In a built program, the first error the expression service raises has the description *Automation error*, and every later one *Unspecified error*. In a run from the IDE, every one has the description *Automation error*.
+
+<!-- errors: generated from errors/VBA.TbExpressionService.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | *expression* is a zero-length string or is not an expression<br>*expression* names something that no registered binder resolves (any name, when no binder is registered), or calls a function with the wrong number of arguments |
+| [94 (`&H5E`)](tb:Errors#94), *Invalid use of Null* | *expression* is **Null** |
+
+<!-- /errors -->
 
 ### Example
 
diff --git a/docs/Reference/Default/VBA/TbExpressionService/Evaluate.md b/docs/Reference/Default/VBA/TbExpressionService/Evaluate.md
index 4edfd31a0..268389e28 100644
--- a/docs/Reference/Default/VBA/TbExpressionService/Evaluate.md
+++ b/docs/Reference/Default/VBA/TbExpressionService/Evaluate.md
@@ -21,6 +21,23 @@ Each call re-runs the expression against the current state of its bindings. If t
 
 A run-time error raised inside the expression --- division by zero, type mismatch, an invalid call into a bound object --- propagates out of **Evaluate** like any other run-time error.
 
+<!-- bug: expression-service-error-numbers -->
+> [!NOTE] BETA 1010
+> **Evaluate** raises -2147467259 for any error inside the expression: the error's own number and description are lost. `"1 / 0"` raises -2147467259, not 11, and a **Scripting.Dictionary**'s **Add** of a key it holds raises -2147467259, not 457.
+
+> [!NOTE] BETA 1010
+> In a built program, the first error the expression service raises has the description *Automation error*, and every later one *Unspecified error*. In a run from the IDE, every one has the description *Automation error*. An error of a bound object's member has the description *Automation error* in both.
+
+<!-- errors: generated from errors/VBA.TbExpressionService.yml by scripts/errors.mjs write; edit the data, not this section -->
+### Common Errors
+
+| Error | When |
+|---|---|
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Unspecified error* | evaluating the expression raises an error, whatever its number: division by zero, a type mismatch, an argument a function refuses<br>the expression calls a member of a bound object that the object does not have, or with the wrong number of arguments |
+| [-2147467259 (`&H80004005`)](tb:Errors#-2147467259), *Automation error* | a member of a bound object that the expression calls raises an error, whatever its number |
+
+<!-- /errors -->
+
 ### Example
 
 This example compiles an expression that references a property on the host object via [**AddCustomBinderObject**](AddCustomBinderObject), then evaluates it twice with the property having different values.
diff --git a/docs/Reference/Glossary.md b/docs/Reference/Glossary.md
index f37538912..5cf6bc3a3 100644
--- a/docs/Reference/Glossary.md
+++ b/docs/Reference/Glossary.md
@@ -282,7 +282,7 @@ A library of routines loaded and linked into applications at run time. DLLs are
 
 ## Empty
 
-Indicates that no beginning value has been assigned to a [**Variant**](#variant-data-type) variable. An **Empty** variable is represented as 0 in a numeric context or a zero-length string (`""`) in a string context.
+Indicates that no beginning value has been assigned to a [**Variant**](#variant-data-type) variable. An **Empty** variable is represented as 0 in a numeric context or a zero-length string (`""`) in a string context. See [**Empty**](../Reference/Literal-Keywords#empty).
 
 ## enumerated constant
 
@@ -469,7 +469,7 @@ Note that the named arguments don't have to appear in the normal positional orde
 
 ## Null
 
-A value indicating that a variable contains no valid data. **Null** is the result of an explicit assignment of **Null** to a variable or any operation between expressions that contain **Null**.
+A value indicating that a variable contains no valid data. **Null** is the result of an explicit assignment of **Null** to a variable or any operation between expressions that contain **Null**. See [**Null**](../Reference/Literal-Keywords#null).
 
 ## numeric data type
 
diff --git a/docs/Reference/Literal-Keywords.md b/docs/Reference/Literal-Keywords.md
new file mode 100644
index 000000000..801d13716
--- /dev/null
+++ b/docs/Reference/Literal-Keywords.md
@@ -0,0 +1,124 @@
+---
+title: Literal Keywords
+parent: Reference Section
+nav_order: 10.5
+has_toc: false
+permalink: /Reference/Literal-Keywords
+symbols: ["Nothing", "Null", "Empty", "True", "False"]
+vba_attribution: true
+---
+
+# Literal Keywords
+
+**Nothing**, **Null**, **Empty**, **True** and **False** are keywords that stand for fixed values. They are part of the language, available in every module without a reference, and cannot be assigned to or declared again.
+
+| Keyword | Value | Type it belongs to | Test for it with |
+|---------|-------|--------------------|------------------|
+| [**Nothing**](#nothing) | a reference to no object | an object type | [**Is**](../tB/Core/Is) or [**IsNot**](../tB/Core/IsNot) |
+| [**Null**](#null) | no valid data | **Variant** | [**IsNull**](../tB/Modules/Information/IsNull) |
+| [**Empty**](#empty) | nothing assigned yet | **Variant** | [**IsEmpty**](../tB/Modules/Information/IsEmpty) |
+| [**True**](#true) | -1 | **Boolean** | the value itself, or [**CBool**](../tB/Modules/Conversion/CBool) |
+| [**False**](#false) | 0 | **Boolean** | the value itself, or [**CBool**](../tB/Modules/Conversion/CBool) |
+
+---
+
+## Nothing
+
+**Nothing** is the object reference that refers to no object. A variable declared **As Object**, or as a class or an interface, holds **Nothing** until an object is assigned to it. [**VarType**](../tB/Modules/Information/VarType) of **Nothing** is **vbObject** (9), [**TypeName**](../tB/Modules/Information/TypeName) is `Nothing`, and [**ObjPtr**](../tB/Modules/Information/ObjPtr) is 0.
+
+**Nothing** is assigned with [**Set**](../tB/Core/Set): `Set Items = Nothing`. This releases the variable's reference. Several variables can refer to one object, and the object is destroyed when the last of them is set to **Nothing** or goes out of scope. A property or method called through a variable that holds **Nothing** raises error [91](tb:Errors#91), *Object variable or With block variable not set*.
+
+Test for it with [**Is**](../tB/Core/Is), `Items Is Nothing`, or with twinBASIC's [**IsNot**](../tB/Core/IsNot), `Items IsNot Nothing`. Two more forms are twinBASIC's own: an initializer in a declaration, `Dim Items As Collection = Nothing`, needs no **Set**, and [**ByVal Nothing**](../Features/Language/Pointers#byval-nothing) passes a null pointer for a **ByRef** interface parameter.
+
+> [!NOTE] BETA 1010
+> **Nothing** assigned without **Set** to a variable that is not an object or a **Variant**, such as `Count = Nothing` for a **Long**, and **Nothing** compared with `=` or `<>`, such as `If Obj = Nothing`, compile and raise error [91](tb:Errors#91) when they run. VB6 and 64-bit VBA refuse them when they compile, with *Invalid use of object*.
+
+> [!WARNING] BETA 1010
+> A **Variant** assigned **Nothing** without **Set**, `v = Nothing`, holds **Nothing**, as after `Set v = Nothing`, and no error is raised. VB6 and 64-bit VBA raise error [91](tb:Errors#91) and leave the **Variant** **Empty**.
+
+[**Object**](../tB/Core/Object#assigning) describes assigning and comparing object references.
+
+```tb check_run
+Dim Items As Collection
+Debug.Print Items Is Nothing        ' True
+Debug.Print TypeName(Items)         ' Nothing
+Set Items = New Collection
+Debug.Print Items Is Nothing        ' False
+Set Items = Nothing
+Debug.Print ObjPtr(Items)           ' 0
+```
+
+---
+
+## Null
+
+**Null** is a **Variant** value that means the variable holds no valid data, such as a field of a database record that has no value. [**VarType**](../tB/Modules/Information/VarType) of **Null** is **vbNull** (1), and [**TypeName**](../tB/Modules/Information/TypeName) is `Null`. Only a **Variant** can hold it: assigning **Null** to a variable of another type raises error [94](tb:Errors#94), *Invalid use of Null*, and `Set` of a **Variant** that holds it to an object variable raises error [424](tb:Errors#424), *Object required*.
+
+**Null** passes through most expressions. An arithmetic expression or a comparison with a **Null** operand is **Null**, so `v = Null` is never **True**: test for it with [**IsNull**](../tB/Modules/Information/IsNull). The `&` operator treats **Null** as an empty string. `Null And False` is **False** and `Null Or True` is **True**, because the other operand decides the result; any other logical operation with **Null** is **Null**. An `If` condition that is **Null** counts as **False**. Many functions return **Null** when an argument is **Null**, and their `$` forms raise error 94; a function's page lists what it raises.
+
+```tb check_run
+Dim v As Variant
+v = Null
+Debug.Print IsNull(v * 2)           ' True
+Debug.Print IsNull(v = Null)        ' True
+Debug.Print "[" & v & "]"           ' []
+Debug.Print v And False             ' False
+Debug.Print v Or True               ' True
+If v Then
+    Debug.Print "then"
+Else
+    Debug.Print "else"              ' else
+End If
+```
+
+---
+
+## Empty
+
+**Empty** is the value of a **Variant** that has not been assigned. [**VarType**](../tB/Modules/Information/VarType) of **Empty** is **vbEmpty** (0), and [**TypeName**](../tB/Modules/Information/TypeName) is `Empty`. Assigning **Empty** to a **Variant** returns it to that state.
+
+**Empty** counts as 0 in a numeric expression and as an empty string in a string expression, so `Empty = 0` and `Empty = ""` are both **True**, and `Empty + 1` is the **Integer** 1. Assigned to a variable of another type, it gives that type's default value: 0, an empty string, or **False**. Test for it with [**IsEmpty**](../tB/Modules/Information/IsEmpty).
+
+[**Variant**](../tB/Core/Variant#empty-null-and-error-values) describes **Empty** and **Null** together with the error values a **Variant** can hold.
+
+```tb check_run
+Dim v As Variant
+Debug.Print IsEmpty(v)              ' True
+Debug.Print v = ""                  ' True
+Debug.Print TypeName(v + 1)         ' Integer
+v = 5
+v = Empty
+Debug.Print IsEmpty(v)              ' True
+```
+
+---
+
+## True
+
+**True** is the **Boolean** value -1, with every bit set. A comparison that holds gives **True**, and `If`, `While` and `Do` run their **True** branch for any number but 0. A number is not equal to **True** unless it is -1 itself: `5 = True` is **False**, although `CBool(5)` is **True**. In arithmetic **True** counts as the **Integer** -1, and [**CStr**](../tB/Modules/Conversion/CStr) gives `True`.
+
+---
+
+## False
+
+**False** is the **Boolean** value 0. It is the default value of a **Boolean** variable, and the result of a comparison that does not hold. In arithmetic it counts as the **Integer** 0, and [**CStr**](../tB/Modules/Conversion/CStr) gives `False`.
+
+[**Boolean**](../tB/Core/Boolean#conversions) describes how numbers and strings convert to **True** and **False**.
+
+```tb check_run
+Debug.Print CInt(True)              ' -1
+Debug.Print True + True             ' -2
+Debug.Print 5 = True                ' False
+Debug.Print CBool(5)                ' True
+Debug.Print CStr(False)             ' False
+```
+
+---
+
+## See Also
+
+- [Data Types](Data-Types) -- the types these values belong to
+- [Variant](../tB/Core/Variant), [Object](../tB/Core/Object), [Boolean](../tB/Core/Boolean) data types
+- [IsNull](../tB/Modules/Information/IsNull), [IsEmpty](../tB/Modules/Information/IsEmpty), [IsObject](../tB/Modules/Information/IsObject) functions
+- [Set](../tB/Core/Set) statement
+- [Is](../tB/Core/Is), [IsNot](../tB/Core/IsNot) operators
diff --git a/docs/Reference/Procedures and Functions.md b/docs/Reference/Procedures and Functions.md
index f254cff61..80f4d2fb2 100644
--- a/docs/Reference/Procedures and Functions.md	
+++ b/docs/Reference/Procedures and Functions.md	
@@ -46,7 +46,7 @@ permalink: /Reference/Procedures-and-Functions
 - [CompilerVersion](../tB/Modules/Compilation/CompilerVersion) -- returns the twinBASIC compiler version number
 - [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap) -- converts an icon picture to a bitmap picture
 - [Cos](../tB/Modules/Math/Cos) -- returns the cosine of an angle
-- [CreateGUID](../tB/Modules/HiddenModule/CreateGUID) -- generates a fresh GUID and returns it as a registry-formatted string
+- [CreateGUID](../tB/Modules/HiddenModule/CreateGUID) -- generates a fresh GUID and returns it as a string
 - [CreateObject](../tB/Modules/Interaction/CreateObject) -- creates a new instance of a COM/Automation object
 - [CreateStdPictureFromHandle](../tB/Modules/HiddenModule/CreateStdPictureFromHandle) -- wraps a GDI bitmap or icon handle in an **stdole.StdPicture**
 - [CSng](../tB/Modules/Conversion/CSng) -- coerces an expression to a **Single**
diff --git a/docs/Reference/Run-time-Errors.md b/docs/Reference/Run-time-Errors.md
index 40b868843..05ab539a5 100644
--- a/docs/Reference/Run-time-Errors.md
+++ b/docs/Reference/Run-time-Errors.md
@@ -35,6 +35,10 @@ The message is the one that **Err.Description** gives for the error once it is r
 > [!NOTE] BETA 1010
 > For a number from 1 to 65535 that has no message of its own, **Error** gives *Application-defined or object-defined error* in twinBASIC and VB6. After `Err.Raise` of such a number, **Err.Description** in VB6 is that same text; in twinBASIC it is empty for a number below 747, and for 747 and above it is the Windows system message of that number, such as *Page fault was a transition fault.* for 747.
 
+<!-- bug: err-raise-hresult-mapping -->
+> [!NOTE] BETA 1010
+> `Err.Raise` of an HRESULT that has a VB error of the same meaning, such as `&H80070057` (`E_INVALIDARG`), raises the HRESULT in twinBASIC. VB6 and 64-bit VBA raise the VB error instead, 5 for that one. [**Raise**](../tB/Modules/ErrObject/Raise) lists them.
+
 ## Error numbers
 
 The messages are those of twinBASIC 32-bit and VB6, which agree for every number from 1 to 65535. *Listed by* links to the number's line under [Pages that list each error](#pages-that-list-each-error), which names the pages whose Common Errors section lists it, in alphabetical order.
@@ -44,13 +48,13 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | Error | Message | Listed by |
 |---|---|---|
 | **3**{: #3 } (`&H3`) | *Return without GoSub* | --- |
-| **5**{: #5 } (`&H5`) | *Invalid procedure call or argument* | [38 pages](#listed-5) |
-| **6**{: #6 } (`&H6`) | *Overflow* | [24 pages](#listed-6) |
+| **5**{: #5 } (`&H5`) | *Invalid procedure call or argument* | [46 pages](#listed-5) |
+| **6**{: #6 } (`&H6`) | *Overflow* | [27 pages](#listed-6) |
 | **7**{: #7 } (`&H7`) | *Out of memory* | --- |
-| **9**{: #9 } (`&H9`) | *Subscript out of range* | [4 pages](#listed-9) |
+| **9**{: #9 } (`&H9`) | *Subscript out of range* | [7 pages](#listed-9) |
 | **10**{: #10 } (`&HA`) | *This array is fixed or temporarily locked* | --- |
-| **11**{: #11 } (`&HB`) | *Division by zero* | --- |
-| **13**{: #13 } (`&HD`) | *Type mismatch* | [39 pages](#listed-13) |
+| **11**{: #11 } (`&HB`) | *Division by zero* | [4 pages](#listed-11) |
+| **13**{: #13 } (`&HD`) | *Type mismatch* | [50 pages](#listed-13) |
 | **14**{: #14 } (`&HE`) | *Out of string space* | --- |
 | **16**{: #16 } (`&H10`) | *Expression too complex* | --- |
 | **17**{: #17 } (`&H11`) | *Can't perform requested operation* | --- |
@@ -63,9 +67,9 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | **49**{: #49 } (`&H31`) | *Bad DLL calling convention* | --- |
 | **51**{: #51 } (`&H33`) | *Internal error* | --- |
 | **52**{: #52 } (`&H34`) | *Bad file name or number* | --- |
-| **53**{: #53 } (`&H35`) | *File not found* | --- |
+| **53**{: #53 } (`&H35`) | *File not found* | [1 page](#listed-53) |
 | **54**{: #54 } (`&H36`) | *Bad file mode* | --- |
-| **55**{: #55 } (`&H37`) | *File already open* | --- |
+| **55**{: #55 } (`&H37`) | *File already open* | [1 page](#listed-55) |
 | **57**{: #57 } (`&H39`) | *Device I/O error* | --- |
 | **58**{: #58 } (`&H3A`) | *File already exists* | --- |
 | **59**{: #59 } (`&H3B`) | *Bad record length* | --- |
@@ -74,15 +78,15 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | **63**{: #63 } (`&H3F`) | *Bad record number* | --- |
 | **67**{: #67 } (`&H43`) | *Too many files* | --- |
 | **68**{: #68 } (`&H44`) | *Device unavailable* | --- |
-| **70**{: #70 } (`&H46`) | *Permission denied* | --- |
+| **70**{: #70 } (`&H46`) | *Permission denied* | [1 page](#listed-70) |
 | **71**{: #71 } (`&H47`) | *Disk not ready* | --- |
 | **74**{: #74 } (`&H4A`) | *Can't rename with different drive* | --- |
 | **75**{: #75 } (`&H4B`) | *Path/File access error* | --- |
-| **76**{: #76 } (`&H4C`) | *Path not found* | --- |
+| **76**{: #76 } (`&H4C`) | *Path not found* | [1 page](#listed-76) |
 | **91**{: #91 } (`&H5B`) | *Object variable or With block variable not set* | [2 pages](#listed-91) |
 | **92**{: #92 } (`&H5C`) | *For loop not initialized* | --- |
 | **93**{: #93 } (`&H5D`) | *Invalid pattern string* | --- |
-| **94**{: #94 } (`&H5E`) | *Invalid use of Null* | [100 pages](#listed-94) |
+| **94**{: #94 } (`&H5E`) | *Invalid use of Null* | [172 pages](#listed-94) |
 | **96**{: #96 } (`&H60`) | *Unable to sink events of object because the object is already firing events to the maximum number of event receivers that it supports* | --- |
 | **97**{: #97 } (`&H61`) | *Can not call friend function on object which is not an instance of defining class* | --- |
 | **98**{: #98 } (`&H62`) | *A property or method call cannot include a reference to a private object, either as an argument or as a return value* | --- |
@@ -99,7 +103,7 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | **394**{: #394 } (`&H18A`) | *Get not supported (write-only property)* | --- |
 | **422**{: #422 } (`&H1A6`) | *Property not found* | --- |
 | **423**{: #423 } (`&H1A7`) | *Property or method not found* | --- |
-| **424**{: #424 } (`&H1A8`) | *Object required* | --- |
+| **424**{: #424 } (`&H1A8`) | *Object required* | [6 pages](#listed-424) |
 | **429**{: #429 } (`&H1AD`) | *ActiveX component can't create object* | --- |
 | **430**{: #430 } (`&H1AE`) | *Class does not support Automation or does not support expected interface* | --- |
 | **432**{: #432 } (`&H1B0`) | *File name or class name not found during Automation operation* | --- |
@@ -118,7 +122,7 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | **453**{: #453 } (`&H1C5`) | *Specified DLL function not found* | --- |
 | **454**{: #454 } (`&H1C6`) | *Code resource not found* | --- |
 | **455**{: #455 } (`&H1C7`) | *Code resource lock error* | --- |
-| **457**{: #457 } (`&H1C9`) | *This key is already associated with an element of this collection* | --- |
+| **457**{: #457 } (`&H1C9`) | *This key is already associated with an element of this collection* | [1 page](#listed-457) |
 | **458**{: #458 } (`&H1CA`) | *Variable uses an Automation type not supported in Visual Basic* | --- |
 | **459**{: #459 } (`&H1CB`) | *Object or class does not support the set of events* | --- |
 | **460**{: #460 } (`&H1CC`) | *Invalid clipboard format* | --- |
@@ -130,38 +134,63 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 | **735**{: #735 } (`&H2DF`) | *Can't save file to TEMP* | --- |
 | **744**{: #744 } (`&H2E8`) | *Search text not found* | --- |
 | **746**{: #746 } (`&H2EA`) | *Replacements too long* | --- |
-| **-2147467262**{: #-2147467262 } (`&H80004002`) | *No such interface supported*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147467262) |
-| **-2147467259**{: #-2147467259 } (`&H80004005`) | *Unspecified error*; **Error** gives *Application-defined or object-defined error* | [20 pages](#listed--2147467259) |
+| **-2147467263**{: #-2147467263 } (`&H80004001`) | *Not implemented*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147467263) |
+| **-2147467262**{: #-2147467262 } (`&H80004002`) | *No such interface supported*; **Error** gives *Application-defined or object-defined error* | [3 pages](#listed--2147467262) |
+| **-2147467261**{: #-2147467261 } (`&H80004003`) | *Invalid pointer*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147467261) |
+| **-2147467259**{: #-2147467259 } (`&H80004005`) | *Unspecified error*; **Error** gives *Application-defined or object-defined error* | [56 pages](#listed--2147467259) |
+| **-2147418113**{: #-2147418113 } (`&H8000FFFF`) | *Catastrophic failure*; **Error** gives *Application-defined or object-defined error* | [4 pages](#listed--2147418113) |
 | **-2147352567**{: #-2147352567 } (`&H80020009`) | *Exception occurred.*; **Error** gives *Application-defined or object-defined error* | [2 pages](#listed--2147352567) |
 | **-2147352562**{: #-2147352562 } (`&H8002000E`) | *Invalid number of parameters.*; **Error** gives *Application-defined or object-defined error* | [2 pages](#listed--2147352562) |
 | **-2147352559**{: #-2147352559 } (`&H80020011`) | *Does not support a collection.*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147352559) |
 | **-2147348207**{: #-2147348207 } (`&H80021111`) | *Automation error*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147348207) |
+| **-2147319765**{: #-2147319765 } (`&H8002802B`) | *Element not found.*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147319765) |
 | **-2147221164**{: #-2147221164 } (`&H80040154`) | *Class not registered*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147221164) |
 | **-2147221021**{: #-2147221021 } (`&H800401E3`) | *Operation unavailable*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147221021) |
 | **-2147221020**{: #-2147221020 } (`&H800401E4`) | *Invalid syntax*; **Error** gives *Application-defined or object-defined error* | [2 pages](#listed--2147221020) |
 | **-2147221014**{: #-2147221014 } (`&H800401EA`) | *Moniker cannot open file*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147221014) |
 | **-2147221005**{: #-2147221005 } (`&H800401F3`) | *Invalid class string*; **Error** gives *Application-defined or object-defined error* | [2 pages](#listed--2147221005) |
+| **-2147024882**{: #-2147024882 } (`&H8007000E`) | *Not enough memory resources are available to complete this operation.*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147024882) |
 | **-2147023174**{: #-2147023174 } (`&H800706BA`) | *The RPC server is unavailable.*; **Error** gives *Application-defined or object-defined error* | [1 page](#listed--2147023174) |
 
 ## Pages that list each error
 
-**5**{: #listed-5 } (`&H5`): [Array](../tB/Modules/Information/Array), [Asc](../tB/Modules/Strings/Asc), [Chr](../tB/Modules/Strings/Chr), [CreateObject](../tB/Modules/Interaction/CreateObject), [CVErr](../tB/Modules/Conversion/CVErr), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateSerial](../tB/Modules/DateTime/DateSerial), [Filter](../tB/Modules/Strings/Filter), [Format](../tB/Modules/Strings/Format), [FormatCurrency](../tB/Modules/Strings/FormatCurrency), [FormatDateTime](../tB/Modules/Strings/FormatDateTime), [FormatNumber](../tB/Modules/Strings/FormatNumber), [FormatPercent](../tB/Modules/Strings/FormatPercent), [GetObject](../tB/Modules/Interaction/GetObject), [InStr](../tB/Modules/Strings/InStr), [InStrRev](../tB/Modules/Strings/InStrRev), [Join](../tB/Modules/Strings/Join), [Left](../tB/Modules/Strings/Left), [Log](../tB/Modules/Math/Log), [Mid](../tB/Modules/Strings/Mid), [MonthName](../tB/Modules/Strings/MonthName), [QBColor](../tB/Modules/Information/QBColor), [Replace](../tB/Modules/Strings/Replace), [RGB](../tB/Modules/Information/RGB), [RGBA](../tB/Modules/Information/RGBA), [Right](../tB/Modules/Strings/Right), [Round](../tB/Modules/Math/Round), [Space](../tB/Modules/Strings/Space), [Split](../tB/Modules/Strings/Split), [Sqr](../tB/Modules/Math/Sqr), [StrComp](../tB/Modules/Strings/StrComp), [StrConv](../tB/Modules/Strings/StrConv), [String](../tB/Modules/Strings/String), [TranslateColor](../tB/Modules/Information/TranslateColor), [Weekday](../tB/Modules/DateTime/Weekday), [WeekdayName](../tB/Modules/Strings/WeekdayName)
+**5**{: #listed-5 } (`&H5`): [Add](../tB/Modules/Collection/Add), [Array](../tB/Modules/Information/Array), [Asc](../tB/Modules/Strings/Asc), [Chr](../tB/Modules/Strings/Chr), [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap), [CreateObject](../tB/Modules/Interaction/CreateObject), [CVErr](../tB/Modules/Conversion/CVErr), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateSerial](../tB/Modules/DateTime/DateSerial), [Filter](../tB/Modules/Strings/Filter), [Format](../tB/Modules/Strings/Format), [FormatCurrency](../tB/Modules/Strings/FormatCurrency), [FormatDateTime](../tB/Modules/Strings/FormatDateTime), [FormatNumber](../tB/Modules/Strings/FormatNumber), [FormatPercent](../tB/Modules/Strings/FormatPercent), [FV](../tB/Modules/Financial/FV), [GetObject](../tB/Modules/Interaction/GetObject), [InStr](../tB/Modules/Strings/InStr), [InStrRev](../tB/Modules/Strings/InStrRev), [Item](../tB/Modules/Collection/Item), [Join](../tB/Modules/Strings/Join), [KeyCompareMode](../tB/Modules/Collection/KeyCompareMode), [Left](../tB/Modules/Strings/Left), [Log](../tB/Modules/Math/Log), [Mid](../tB/Modules/Strings/Mid), [MonthName](../tB/Modules/Strings/MonthName), [QBColor](../tB/Modules/Information/QBColor), [Raise](../tB/Modules/ErrObject/Raise), [Rate](../tB/Modules/Financial/Rate), [Remove](../tB/Modules/Collection/Remove), [Replace](../tB/Modules/Strings/Replace), [RGB](../tB/Modules/Information/RGB), [RGBA](../tB/Modules/Information/RGBA), [Right](../tB/Modules/Strings/Right), [Round](../tB/Modules/Math/Round), [Space](../tB/Modules/Strings/Space), [Split](../tB/Modules/Strings/Split), [Sqr](../tB/Modules/Math/Sqr), [StrComp](../tB/Modules/Strings/StrComp), [StrConv](../tB/Modules/Strings/StrConv), [String](../tB/Modules/Strings/String), [TranslateColor](../tB/Modules/Information/TranslateColor), [Weekday](../tB/Modules/DateTime/Weekday), [WeekdayName](../tB/Modules/Strings/WeekdayName)
+
+**6**{: #listed-6 } (`&H6`): [Abs](../tB/Modules/Math/Abs), [Bin](../tB/Modules/Conversion/Bin), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [Choose](../tB/Modules/Interaction/Choose), [Chr](../tB/Modules/Strings/Chr), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [CSng](../tB/Modules/Conversion/CSng), [CType](../tB/Modules/Conversion/CType), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [Exp](../tB/Modules/Math/Exp), [FV](../tB/Modules/Financial/FV), [Hex](../tB/Modules/Conversion/Hex), [InputBox](../tB/Modules/Interaction/InputBox), [NPer](../tB/Modules/Financial/NPer), [Oct](../tB/Modules/Conversion/Oct), [Pmt](../tB/Modules/Financial/Pmt), [Val](../tB/Modules/Conversion/Val), [ValDec](../tB/Modules/Conversion/ValDec)
+
+**9**{: #listed-9 } (`&H9`): [Add](../tB/Modules/Collection/Add), [Array](../tB/Modules/Information/Array), [Item](../tB/Modules/Collection/Item), [LBound](../tB/Modules/Information/LBound), [ReDim](../tB/Core/ReDim), [Remove](../tB/Modules/Collection/Remove), [UBound](../tB/Modules/Information/UBound)
+
+**11**{: #listed-11 } (`&HB`): [NPer](../tB/Modules/Financial/NPer), [Pmt](../tB/Modules/Financial/Pmt), [PPmt](../tB/Modules/Financial/PPmt), [PV](../tB/Modules/Financial/PV)
+
+**13**{: #listed-13 } (`&HD`): [Add](../tB/Modules/Collection/Add), [Bin](../tB/Modules/Conversion/Bin), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap), [CSng](../tB/Modules/Conversion/CSng), [CType](../tB/Modules/Conversion/CType), [CVDate](../tB/Modules/Conversion/CVDate), [Date](../tB/Modules/DateTime/Date), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateValue](../tB/Modules/DateTime/DateValue), [Day](../tB/Modules/DateTime/Day), [DDB](../tB/Modules/Financial/DDB), [Filter](../tB/Modules/Strings/Filter), [FV](../tB/Modules/Financial/FV), [Hex](../tB/Modules/Conversion/Hex), [Hour](../tB/Modules/DateTime/Hour), [If](../tB/Modules/Interaction/If), [IIf](../tB/Modules/Interaction/IIf), [IPmt](../tB/Modules/Financial/IPmt), [IRR](../tB/Modules/Financial/IRR), [Join](../tB/Modules/Strings/Join), [LBound](../tB/Modules/Information/LBound), [Minute](../tB/Modules/DateTime/Minute), [Month](../tB/Modules/DateTime/Month), [NPer](../tB/Modules/Financial/NPer), [Oct](../tB/Modules/Conversion/Oct), [Pmt](../tB/Modules/Financial/Pmt), [PPmt](../tB/Modules/Financial/PPmt), [PV](../tB/Modules/Financial/PV), [Rate](../tB/Modules/Financial/Rate), [ReDim](../tB/Core/ReDim), [Second](../tB/Modules/DateTime/Second), [Switch](../tB/Modules/Interaction/Switch), [Time](../tB/Modules/DateTime/Time), [TimeValue](../tB/Modules/DateTime/TimeValue), [UBound](../tB/Modules/Information/UBound), [Val](../tB/Modules/Conversion/Val), [Weekday](../tB/Modules/DateTime/Weekday), [Year](../tB/Modules/DateTime/Year)
+
+**53**{: #listed-53 } (`&H35`): [FileCopy](../tB/Modules/FileSystem/FileCopy)
 
-**6**{: #listed-6 } (`&H6`): [Abs](../tB/Modules/Math/Abs), [Bin](../tB/Modules/Conversion/Bin), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [Choose](../tB/Modules/Interaction/Choose), [Chr](../tB/Modules/Strings/Chr), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [CSng](../tB/Modules/Conversion/CSng), [CType](../tB/Modules/Conversion/CType), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [Exp](../tB/Modules/Math/Exp), [Hex](../tB/Modules/Conversion/Hex), [InputBox](../tB/Modules/Interaction/InputBox), [Oct](../tB/Modules/Conversion/Oct), [Val](../tB/Modules/Conversion/Val), [ValDec](../tB/Modules/Conversion/ValDec)
+**55**{: #listed-55 } (`&H37`): [FileCopy](../tB/Modules/FileSystem/FileCopy)
 
-**9**{: #listed-9 } (`&H9`): [Array](../tB/Modules/Information/Array), [LBound](../tB/Modules/Information/LBound), [ReDim](../tB/Core/ReDim), [UBound](../tB/Modules/Information/UBound)
+**70**{: #listed-70 } (`&H46`): [FileCopy](../tB/Modules/FileSystem/FileCopy)
 
-**13**{: #listed-13 } (`&HD`): [Bin](../tB/Modules/Conversion/Bin), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [CSng](../tB/Modules/Conversion/CSng), [CType](../tB/Modules/Conversion/CType), [CVDate](../tB/Modules/Conversion/CVDate), [Date](../tB/Modules/DateTime/Date), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateValue](../tB/Modules/DateTime/DateValue), [Day](../tB/Modules/DateTime/Day), [Filter](../tB/Modules/Strings/Filter), [Hex](../tB/Modules/Conversion/Hex), [Hour](../tB/Modules/DateTime/Hour), [If](../tB/Modules/Interaction/If), [IIf](../tB/Modules/Interaction/IIf), [Join](../tB/Modules/Strings/Join), [LBound](../tB/Modules/Information/LBound), [Minute](../tB/Modules/DateTime/Minute), [Month](../tB/Modules/DateTime/Month), [Oct](../tB/Modules/Conversion/Oct), [ReDim](../tB/Core/ReDim), [Second](../tB/Modules/DateTime/Second), [Switch](../tB/Modules/Interaction/Switch), [Time](../tB/Modules/DateTime/Time), [TimeValue](../tB/Modules/DateTime/TimeValue), [UBound](../tB/Modules/Information/UBound), [Val](../tB/Modules/Conversion/Val), [Weekday](../tB/Modules/DateTime/Weekday), [Year](../tB/Modules/DateTime/Year)
+**76**{: #listed-76 } (`&H4C`): [FileCopy](../tB/Modules/FileSystem/FileCopy)
 
 **91**{: #listed-91 } (`&H5B`): [RaiseEventByName](../tB/Modules/Interaction/RaiseEventByName), [RaiseEventByName2](../tB/Modules/Interaction/RaiseEventByName2)
 
-**94**{: #listed-94 } (`&H5E`): [AppActivate](../tB/Modules/Interaction/AppActivate), [Asc](../tB/Modules/Strings/Asc), [Atn](../tB/Modules/Math/Atn), [Bin](../tB/Modules/Conversion/Bin), [Calendar](../tB/Modules/DateTime/Calendar), [CallByDispId](../tB/Modules/Interaction/CallByDispId), [CallByName](../tB/Modules/Interaction/CallByName), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [Choose](../tB/Modules/Interaction/Choose), [Chr](../tB/Modules/Strings/Chr), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [Cos](../tB/Modules/Math/Cos), [CreateObject](../tB/Modules/Interaction/CreateObject), [CSng](../tB/Modules/Conversion/CSng), [CStr](../tB/Modules/Conversion/CStr), [CType](../tB/Modules/Conversion/CType), [CVErr](../tB/Modules/Conversion/CVErr), [Date](../tB/Modules/DateTime/Date), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateSerial](../tB/Modules/DateTime/DateSerial), [DateValue](../tB/Modules/DateTime/DateValue), [DeleteSetting](../tB/Modules/Interaction/DeleteSetting), [Environ](../tB/Modules/Interaction/Environ), [Error function](../tB/Modules/Conversion/Error), [Exp](../tB/Modules/Math/Exp), [Filter](../tB/Modules/Strings/Filter), [Format](../tB/Modules/Strings/Format), [FormatCurrency](../tB/Modules/Strings/FormatCurrency), [FormatDateTime](../tB/Modules/Strings/FormatDateTime), [FormatNumber](../tB/Modules/Strings/FormatNumber), [FormatPercent](../tB/Modules/Strings/FormatPercent), [GetAllSettings](../tB/Modules/Interaction/GetAllSettings), [GetObject](../tB/Modules/Interaction/GetObject), [GetSetting](../tB/Modules/Interaction/GetSetting), [Hex](../tB/Modules/Conversion/Hex), [InputBox](../tB/Modules/Interaction/InputBox), [InStr](../tB/Modules/Strings/InStr), [InStrRev](../tB/Modules/Strings/InStrRev), [Join](../tB/Modules/Strings/Join), [LBound](../tB/Modules/Information/LBound), [LCase](../tB/Modules/Strings/LCase), [Left](../tB/Modules/Strings/Left), [Log](../tB/Modules/Math/Log), [LTrim](../tB/Modules/Strings/LTrim), [MacID](../tB/Modules/Conversion/MacID), [Mid](../tB/Modules/Strings/Mid), [MonthName](../tB/Modules/Strings/MonthName), [MsgBox](../tB/Modules/Interaction/MsgBox), [Oct](../tB/Modules/Conversion/Oct), [QBColor](../tB/Modules/Information/QBColor), [Randomize](../tB/Modules/Math/Randomize), [Replace](../tB/Modules/Strings/Replace), [RGB](../tB/Modules/Information/RGB), [RGB_B](../tB/Modules/Information/RGB_B), [RGB_G](../tB/Modules/Information/RGB_G), [RGB_R](../tB/Modules/Information/RGB_R), [RGBA](../tB/Modules/Information/RGBA), [RGBA_A](../tB/Modules/Information/RGBA_A), [Right](../tB/Modules/Strings/Right), [Rnd](../tB/Modules/Math/Rnd), [Round](../tB/Modules/Math/Round), [RTrim](../tB/Modules/Strings/RTrim), [SaveSetting](../tB/Modules/Interaction/SaveSetting), [SendKeys](../tB/Modules/Interaction/SendKeys), [Sgn](../tB/Modules/Math/Sgn), [Shell](../tB/Modules/Interaction/Shell), [ShiftRotateLeft](../tB/Modules/Math/ShiftRotateLeft), [ShiftRotateRight](../tB/Modules/Math/ShiftRotateRight), [ShiftUnsignedRight](../tB/Modules/Math/ShiftUnsignedRight), [Sin](../tB/Modules/Math/Sin), [Space](../tB/Modules/Strings/Space), [Split](../tB/Modules/Strings/Split), [Sqr](../tB/Modules/Math/Sqr), [Str](../tB/Modules/Conversion/Str), [StrComp](../tB/Modules/Strings/StrComp), [StrConv](../tB/Modules/Strings/StrConv), [String](../tB/Modules/Strings/String), [StrReverse](../tB/Modules/Strings/StrReverse), [Tan](../tB/Modules/Math/Tan), [Time](../tB/Modules/DateTime/Time), [TimeSerial](../tB/Modules/DateTime/TimeSerial), [TimeValue](../tB/Modules/DateTime/TimeValue), [TranslateColor](../tB/Modules/Information/TranslateColor), [Trim](../tB/Modules/Strings/Trim), [UBound](../tB/Modules/Information/UBound), [UCase](../tB/Modules/Strings/UCase), [Val](../tB/Modules/Conversion/Val), [ValDec](../tB/Modules/Conversion/ValDec), [Weekday](../tB/Modules/DateTime/Weekday), [WeekdayName](../tB/Modules/Strings/WeekdayName)
+**94**{: #listed-94 } (`&H5E`): [AddClassInstanceFlag](../tB/Modules/HiddenModule/AddClassInstanceFlag), [AddCustomBinderObject](../tB/Modules/TbExpressionService/AddCustomBinderObject), [AllocMem](../tB/Modules/HiddenModule/AllocMem), [AppActivate](../tB/Modules/Interaction/AppActivate), [Asc](../tB/Modules/Strings/Asc), [Atn](../tB/Modules/Math/Atn), [Bin](../tB/Modules/Conversion/Bin), [Calendar](../tB/Modules/DateTime/Calendar), [CallByDispId](../tB/Modules/Interaction/CallByDispId), [CallByName](../tB/Modules/Interaction/CallByName), [CBool](../tB/Modules/Conversion/CBool), [CByte](../tB/Modules/Conversion/CByte), [CCur](../tB/Modules/Conversion/CCur), [CDate](../tB/Modules/Conversion/CDate), [CDbl](../tB/Modules/Conversion/CDbl), [CDec](../tB/Modules/Conversion/CDec), [ChDir](../tB/Modules/FileSystem/ChDir), [ChDrive](../tB/Modules/FileSystem/ChDrive), [Choose](../tB/Modules/Interaction/Choose), [Chr](../tB/Modules/Strings/Chr), [CInt](../tB/Modules/Conversion/CInt), [CLng](../tB/Modules/Conversion/CLng), [CLngLng](../tB/Modules/Conversion/CLngLng), [CLngPtr](../tB/Modules/Conversion/CLngPtr), [Compile](../tB/Modules/TbExpressionService/Compile), [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap), [Cos](../tB/Modules/Math/Cos), [CreateObject](../tB/Modules/Interaction/CreateObject), [CreateStdPictureFromHandle](../tB/Modules/HiddenModule/CreateStdPictureFromHandle), [CSng](../tB/Modules/Conversion/CSng), [CStr](../tB/Modules/Conversion/CStr), [CType](../tB/Modules/Conversion/CType), [CurDir](../tB/Modules/FileSystem/CurDir), [CVErr](../tB/Modules/Conversion/CVErr), [Date](../tB/Modules/DateTime/Date), [DateAdd](../tB/Modules/DateTime/DateAdd), [DateDiff](../tB/Modules/DateTime/DateDiff), [DatePart](../tB/Modules/DateTime/DatePart), [DateSerial](../tB/Modules/DateTime/DateSerial), [DateValue](../tB/Modules/DateTime/DateValue), [DDB](../tB/Modules/Financial/DDB), [DeleteSetting](../tB/Modules/Interaction/DeleteSetting), [Description](../tB/Modules/ErrObject/Description), [Dir](../tB/Modules/FileSystem/Dir), [Environ](../tB/Modules/Interaction/Environ), [EOF](../tB/Modules/FileSystem/EOF), [Error function](../tB/Modules/Conversion/Error), [Eval](../tB/Modules/HiddenModule/Eval), [Exists](../tB/Modules/Collection/Exists), [Exp](../tB/Modules/Math/Exp), [FileAttr](../tB/Modules/FileSystem/FileAttr), [FileCopy](../tB/Modules/FileSystem/FileCopy), [FileDateTime](../tB/Modules/FileSystem/FileDateTime), [FileLen](../tB/Modules/FileSystem/FileLen), [Filter](../tB/Modules/Strings/Filter), [Format](../tB/Modules/Strings/Format), [FormatCurrency](../tB/Modules/Strings/FormatCurrency), [FormatDateTime](../tB/Modules/Strings/FormatDateTime), [FormatNumber](../tB/Modules/Strings/FormatNumber), [FormatPercent](../tB/Modules/Strings/FormatPercent), [FreeFile](../tB/Modules/FileSystem/FreeFile), [FreeMem](../tB/Modules/HiddenModule/FreeMem), [FV](../tB/Modules/Financial/FV), [GetAllSettings](../tB/Modules/Interaction/GetAllSettings), [GetAttr](../tB/Modules/FileSystem/GetAttr), [GetMem1](../tB/Modules/HiddenModule/GetMem1), [GetMem2](../tB/Modules/HiddenModule/GetMem2), [GetMem4](../tB/Modules/HiddenModule/GetMem4), [GetMem8](../tB/Modules/HiddenModule/GetMem8), [GetMemPtr](../tB/Modules/HiddenModule/GetMemPtr), [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID), [GetObject](../tB/Modules/Interaction/GetObject), [GetSetting](../tB/Modules/Interaction/GetSetting), [GetShortcutTextByEnum](../tB/Modules/HiddenModule/GetShortcutTextByEnum), [Hex](../tB/Modules/Conversion/Hex), [Input, Input$](../tB/Modules/FileSystem/Input), [InputB, InputB$](../tB/Modules/FileSystem/InputB), [InputBox](../tB/Modules/Interaction/InputBox), [InStr](../tB/Modules/Strings/InStr), [InStrRev](../tB/Modules/Strings/InStrRev), [InterlockedCompareExchange32](../tB/Modules/HiddenModule/InterlockedCompareExchange32), [InterlockedCompareExchange64](../tB/Modules/HiddenModule/InterlockedCompareExchange64), [InterlockedCompareExchangePointer](../tB/Modules/HiddenModule/InterlockedCompareExchangePointer), [InterlockedExchangePointer](../tB/Modules/HiddenModule/InterlockedExchangePointer), [IPmt](../tB/Modules/Financial/IPmt), [IRR](../tB/Modules/Financial/IRR), [Join](../tB/Modules/Strings/Join), [KeyCompareMode](../tB/Modules/Collection/KeyCompareMode), [KeyCountHint](../tB/Modules/Collection/KeyCountHint), [Kill](../tB/Modules/FileSystem/Kill), [LBound](../tB/Modules/Information/LBound), [LCase](../tB/Modules/Strings/LCase), [Left](../tB/Modules/Strings/Left), [Loc](../tB/Modules/FileSystem/Loc), [LOF](../tB/Modules/FileSystem/LOF), [Log](../tB/Modules/Math/Log), [LTrim](../tB/Modules/Strings/LTrim), [MacID](../tB/Modules/Conversion/MacID), [Mid](../tB/Modules/Strings/Mid), [MIRR](../tB/Modules/Financial/MIRR), [MkDir](../tB/Modules/FileSystem/MkDir), [MonthName](../tB/Modules/Strings/MonthName), [MsgBox](../tB/Modules/Interaction/MsgBox), [NPer](../tB/Modules/Financial/NPer), [NPV](../tB/Modules/Financial/NPV), [Number](../tB/Modules/ErrObject/Number), [Oct](../tB/Modules/Conversion/Oct), [Pmt](../tB/Modules/Financial/Pmt), [PPmt](../tB/Modules/Financial/PPmt), [PutMem1](../tB/Modules/HiddenModule/PutMem1), [PutMem2](../tB/Modules/HiddenModule/PutMem2), [PutMem4](../tB/Modules/HiddenModule/PutMem4), [PutMem8](../tB/Modules/HiddenModule/PutMem8), [PutMemPtr](../tB/Modules/HiddenModule/PutMemPtr), [PV](../tB/Modules/Financial/PV), [QBColor](../tB/Modules/Information/QBColor), [Raise](../tB/Modules/ErrObject/Raise), [Randomize](../tB/Modules/Math/Randomize), [Rate](../tB/Modules/Financial/Rate), [RegisterMessage](../tB/Modules/HiddenModule/RegisterMessage), [Replace](../tB/Modules/Strings/Replace), [RGB](../tB/Modules/Information/RGB), [RGB_B](../tB/Modules/Information/RGB_B), [RGB_G](../tB/Modules/Information/RGB_G), [RGB_R](../tB/Modules/Information/RGB_R), [RGBA](../tB/Modules/Information/RGBA), [RGBA_A](../tB/Modules/Information/RGBA_A), [Right](../tB/Modules/Strings/Right), [RmDir](../tB/Modules/FileSystem/RmDir), [Rnd](../tB/Modules/Math/Rnd), [Round](../tB/Modules/Math/Round), [RTrim](../tB/Modules/Strings/RTrim), [SaveSetting](../tB/Modules/Interaction/SaveSetting), [Seek](../tB/Modules/FileSystem/Seek), [SendKeys](../tB/Modules/Interaction/SendKeys), [SetAttr](../tB/Modules/FileSystem/SetAttr), [SetThreadGlobalErrorTrap](../tB/Modules/HiddenModule/SetThreadGlobalErrorTrap), [Sgn](../tB/Modules/Math/Sgn), [Shell](../tB/Modules/Interaction/Shell), [ShiftRotateLeft](../tB/Modules/Math/ShiftRotateLeft), [ShiftRotateRight](../tB/Modules/Math/ShiftRotateRight), [ShiftUnsignedRight](../tB/Modules/Math/ShiftUnsignedRight), [Sin](../tB/Modules/Math/Sin), [SLN](../tB/Modules/Financial/SLN), [Source](../tB/Modules/ErrObject/Source), [Space](../tB/Modules/Strings/Space), [Split](../tB/Modules/Strings/Split), [Sqr](../tB/Modules/Math/Sqr), [Str](../tB/Modules/Conversion/Str), [StrComp](../tB/Modules/Strings/StrComp), [StrConv](../tB/Modules/Strings/StrConv), [String](../tB/Modules/Strings/String), [StrReverse](../tB/Modules/Strings/StrReverse), [SYD](../tB/Modules/Financial/SYD), [Tan](../tB/Modules/Math/Tan), [Time](../tB/Modules/DateTime/Time), [TimeSerial](../tB/Modules/DateTime/TimeSerial), [TimeValue](../tB/Modules/DateTime/TimeValue), [TranslateColor](../tB/Modules/Information/TranslateColor), [Trim](../tB/Modules/Strings/Trim), [UBound](../tB/Modules/Information/UBound), [UCase](../tB/Modules/Strings/UCase), [Val](../tB/Modules/Conversion/Val), [ValDec](../tB/Modules/Conversion/ValDec), [vbaCopyBytes](../tB/Modules/HiddenModule/vbaCopyBytes), [vbaCopyBytesZero](../tB/Modules/HiddenModule/vbaCopyBytesZero), [vbaObjAddref](../tB/Modules/HiddenModule/vbaObjAddref), [vbaObjSet](../tB/Modules/HiddenModule/vbaObjSet), [vbaObjSetAddref](../tB/Modules/HiddenModule/vbaObjSetAddref), [Weekday](../tB/Modules/DateTime/Weekday), [WeekdayName](../tB/Modules/Strings/WeekdayName), [Width](../tB/Modules/FileSystem/Width)
+
+**424**{: #listed-424 } (`&H1A8`): [AddClassInstanceFlag](../tB/Modules/HiddenModule/AddClassInstanceFlag), [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap), [GetInheritedOwner](../tB/Modules/HiddenModule/GetInheritedOwner), [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID), [PictureToByteArray](../tB/Modules/HiddenModule/PictureToByteArray), [vbaCastObj](../tB/Modules/HiddenModule/vbaCastObj)
 
 **438**{: #listed-438 } (`&H1B6`): [CallByDispId](../tB/Modules/Interaction/CallByDispId), [CallByName](../tB/Modules/Interaction/CallByName)
 
-**-2147467262**{: #listed--2147467262 } (`&H80004002`): [GetObject](../tB/Modules/Interaction/GetObject)
+**457**{: #listed-457 } (`&H1C9`): [Add](../tB/Modules/Collection/Add)
+
+**-2147467263**{: #listed--2147467263 } (`&H80004001`): [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID)
+
+**-2147467262**{: #listed--2147467262 } (`&H80004002`): [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID), [GetObject](../tB/Modules/Interaction/GetObject), [PictureToByteArray](../tB/Modules/HiddenModule/PictureToByteArray)
+
+**-2147467261**{: #listed--2147467261 } (`&H80004003`): [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID)
 
-**-2147467259**{: #listed--2147467259 } (`&H80004005`): [AppActivate](../tB/Modules/Interaction/AppActivate), [Calendar](../tB/Modules/DateTime/Calendar), [CallByDispId](../tB/Modules/Interaction/CallByDispId), [CallByName](../tB/Modules/Interaction/CallByName), [Date](../tB/Modules/DateTime/Date), [DeleteSetting](../tB/Modules/Interaction/DeleteSetting), [Environ](../tB/Modules/Interaction/Environ), [GetAllSettings](../tB/Modules/Interaction/GetAllSettings), [GetObject](../tB/Modules/Interaction/GetObject), [GetSetting](../tB/Modules/Interaction/GetSetting), [InputBox](../tB/Modules/Interaction/InputBox), [LBound](../tB/Modules/Information/LBound), [MsgBox](../tB/Modules/Interaction/MsgBox), [Partition](../tB/Modules/Interaction/Partition), [ReDim](../tB/Core/ReDim), [SaveSetting](../tB/Modules/Interaction/SaveSetting), [Shell](../tB/Modules/Interaction/Shell), [Switch](../tB/Modules/Interaction/Switch), [Time](../tB/Modules/DateTime/Time), [UBound](../tB/Modules/Information/UBound)
+**-2147467259**{: #listed--2147467259 } (`&H80004005`): [AppActivate](../tB/Modules/Interaction/AppActivate), [Calendar](../tB/Modules/DateTime/Calendar), [CallByDispId](../tB/Modules/Interaction/CallByDispId), [CallByName](../tB/Modules/Interaction/CallByName), [ChDir](../tB/Modules/FileSystem/ChDir), [ChDrive](../tB/Modules/FileSystem/ChDrive), [Compile](../tB/Modules/TbExpressionService/Compile), [ConvertIconToBitmap](../tB/Modules/HiddenModule/ConvertIconToBitmap), [CreateStdPictureFromHandle](../tB/Modules/HiddenModule/CreateStdPictureFromHandle), [CurDir](../tB/Modules/FileSystem/CurDir), [Date](../tB/Modules/DateTime/Date), [DDB](../tB/Modules/Financial/DDB), [DeleteSetting](../tB/Modules/Interaction/DeleteSetting), [Dir](../tB/Modules/FileSystem/Dir), [Environ](../tB/Modules/Interaction/Environ), [EOF](../tB/Modules/FileSystem/EOF), [Eval](../tB/Modules/HiddenModule/Eval), [Evaluate](../tB/Modules/TbExpressionService/Evaluate), [FileAttr](../tB/Modules/FileSystem/FileAttr), [FileCopy](../tB/Modules/FileSystem/FileCopy), [FileDateTime](../tB/Modules/FileSystem/FileDateTime), [FileLen](../tB/Modules/FileSystem/FileLen), [FreeFile](../tB/Modules/FileSystem/FreeFile), [GetAllSettings](../tB/Modules/Interaction/GetAllSettings), [GetAttr](../tB/Modules/FileSystem/GetAttr), [GetObject](../tB/Modules/Interaction/GetObject), [GetSetting](../tB/Modules/Interaction/GetSetting), [Input, Input$](../tB/Modules/FileSystem/Input), [InputB, InputB$](../tB/Modules/FileSystem/InputB), [InputBox](../tB/Modules/Interaction/InputBox), [IPmt](../tB/Modules/Financial/IPmt), [IRR](../tB/Modules/Financial/IRR), [Kill](../tB/Modules/FileSystem/Kill), [LBound](../tB/Modules/Information/LBound), [Loc](../tB/Modules/FileSystem/Loc), [LOF](../tB/Modules/FileSystem/LOF), [MkDir](../tB/Modules/FileSystem/MkDir), [MsgBox](../tB/Modules/Interaction/MsgBox), [NPer](../tB/Modules/Financial/NPer), [Partition](../tB/Modules/Interaction/Partition), [Pmt](../tB/Modules/Financial/Pmt), [PPmt](../tB/Modules/Financial/PPmt), [PV](../tB/Modules/Financial/PV), [Rate](../tB/Modules/Financial/Rate), [ReDim](../tB/Core/ReDim), [RmDir](../tB/Modules/FileSystem/RmDir), [SaveSetting](../tB/Modules/Interaction/SaveSetting), [Seek](../tB/Modules/FileSystem/Seek), [SetAttr](../tB/Modules/FileSystem/SetAttr), [Shell](../tB/Modules/Interaction/Shell), [SLN](../tB/Modules/Financial/SLN), [Switch](../tB/Modules/Interaction/Switch), [SYD](../tB/Modules/Financial/SYD), [Time](../tB/Modules/DateTime/Time), [UBound](../tB/Modules/Information/UBound), [Width](../tB/Modules/FileSystem/Width)
+
+**-2147418113**{: #listed--2147418113 } (`&H8000FFFF`): [CreateStdPictureFromHandle](../tB/Modules/HiddenModule/CreateStdPictureFromHandle), [IRR](../tB/Modules/Financial/IRR), [MIRR](../tB/Modules/Financial/MIRR), [NPV](../tB/Modules/Financial/NPV)
 
 **-2147352567**{: #listed--2147352567 } (`&H80020009`): [CallByName](../tB/Modules/Interaction/CallByName), [SendKeys](../tB/Modules/Interaction/SendKeys)
 
@@ -171,6 +200,8 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 
 **-2147348207**{: #listed--2147348207 } (`&H80021111`): [Tan](../tB/Modules/Math/Tan)
 
+**-2147319765**{: #listed--2147319765 } (`&H8002802B`): [GetNameFromDispID](../tB/Modules/HiddenModule/GetNameFromDispID)
+
 **-2147221164**{: #listed--2147221164 } (`&H80040154`): [CreateObject](../tB/Modules/Interaction/CreateObject)
 
 **-2147221021**{: #listed--2147221021 } (`&H800401E3`): [GetObject](../tB/Modules/Interaction/GetObject)
@@ -181,6 +212,8 @@ The messages are those of twinBASIC 32-bit and VB6, which agree for every number
 
 **-2147221005**{: #listed--2147221005 } (`&H800401F3`): [CreateObject](../tB/Modules/Interaction/CreateObject), [GetObject](../tB/Modules/Interaction/GetObject)
 
+**-2147024882**{: #listed--2147024882 } (`&H8007000E`): [AllocMem](../tB/Modules/HiddenModule/AllocMem)
+
 **-2147023174**{: #listed--2147023174 } (`&H800706BA`): [CreateObject](../tB/Modules/Interaction/CreateObject)
 
 <!-- /errors-index -->
diff --git a/docs/Reference/index.md b/docs/Reference/index.md
index cbccd3b35..7dbfc68d5 100644
--- a/docs/Reference/index.md
+++ b/docs/Reference/index.md
@@ -16,6 +16,7 @@ The reference is organized into three layers: the language constructs the compil
 - [**Operators**](Reference/Operators) -- arithmetic, comparison, logical, bitwise, and twinBASIC's added operators
 - [**Enumerations**](Reference/Enumerations) -- index of all {{tbdocs:enumerations}} enumeration types across all {{tbdocs:packages}} packages, grouped by package and A--Z
 - [**Data Types**](Reference/Data-Types) -- storage size, range, and suffix for every intrinsic type (**Boolean** through **Variant**)
+- [**Literal Keywords**](Reference/Literal-Keywords) -- **Nothing**, **Null**, **Empty**, **True** and **False**
 - [**Compiler Constants**](Reference/Compiler-Constants) -- the `#If` symbols the compiler recognises
 - [**Run-time Errors**](Reference/Run-time-Errors) -- every trappable error number with its message, and the pages that list it
 - [**Attributes**](../tB/Core/Attributes) -- `[Description(...)]`, `[COMCreatable(...)]`, and the rest of the attribute syntax
diff --git a/docs/_book.yml b/docs/_book.yml
index 379d104b5..ab424c0ae 100644
--- a/docs/_book.yml
+++ b/docs/_book.yml
@@ -352,6 +352,11 @@ parts:
         no_outline_entry: true
         no_heading_shift: true
         outline_closed: true
+      - title: Literal Keywords
+        page: /Reference/Literal-Keywords
+        no_outline_entry: true
+        no_heading_shift: true
+        outline_closed: true
       - title: Compiler Constants
         page: /Reference/Compiler-Constants
         no_outline_entry: true
diff --git a/errors/VBA.Collection.yml b/errors/VBA.Collection.yml
new file mode 100644
index 000000000..beadc33c6
--- /dev/null
+++ b/errors/VBA.Collection.yml
@@ -0,0 +1,308 @@
+# The VBA Collection class. Format: WIP.Errors.md.
+beta: 1010
+pages:
+  Reference/Default/VBA/Collection/Add.md:
+    rows:
+      - error: 457
+        when: "*key* is already the key of an item in the collection, as [**KeyCompareMode**](KeyCompareMode) compares keys (by default `\"A\"` and `\"a\"` are the same key)"
+        cases:
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, "a"' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, "A"' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, ""', run: 'C.Add 2, ""' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, "a", "z"' }
+      - error: 13
+        when: "*key* is not a **String**: a number, **True**, **Null**, an object, **Nothing** or an array"
+        cases:
+          - { decl: Dim C As New Collection, run: 'C.Add 1, Null' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, 5' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, 5.5' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, True' }
+          - { decl: "Dim C As New Collection\nDim D As New Collection", run: 'C.Add 1, D' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, Nothing' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, Array("a")' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, Null, "z"' }
+      - error: 0
+        when: "*key* is **Empty**"
+        vb6: 13
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, run: "C.Add 1, Empty\nIf C.Count = 1 And UBound(C.Keys) = -1 Then Err.Clear Else Err.Raise 1001", only: tb }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, Empty' }
+      - error: 5
+        when: "both *before* and *after* are given"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 1, 1' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, "b", "a", "a"' }
+      - error: 5
+        when: "*before* or *after* is given and the collection is empty"
+        cases:
+          - { decl: Dim C As New Collection, run: 'C.Add 1, , 1' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, , , 1' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, , 0' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, , , 0' }
+          - { decl: Dim C As New Collection, run: 'C.Add 1, "a", 1' }
+          - { decl: Dim C As New Collection, run: 'C.Add 2, , -1' }
+          - { decl: Dim C As New Collection, run: 'C.Add 2, , Null' }
+          - { decl: Dim C As New Collection, run: 'C.Add 2, , "a"' }
+          - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Remove 1", run: 'C.Add 2, , 1' }
+      - error: 5
+        when: "*before* or *after* is a string that is not the key of an item"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , ""' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, , "b"' }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, , , "b"' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , "1"' }
+      - error: 9
+        when: "*before* is a number that, rounded, is less than 1 or greater than **Count** + 1, or *after* one that is less than 0 or greater than **Count**"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 0' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 0.5' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , -2' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , -2' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , 2' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , 1.5' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 2147483647' }
+          - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", run: 'C.Add 3, , 4' }
+          - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", run: 'C.Add 3, , , 3' }
+      - error: 13
+        when: "*before* or *after* is -1, **True** or **Empty**"
+        vb6: 9
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , -1' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , -1' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , True' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , Empty' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , Empty' }
+      - error: 13
+        when: "*before* or *after* is a **Currency**, **Decimal** or **Date** value"
+        vb6: 0
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CCur(1)' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , CCur(1)' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CDec(1)' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CDate(1)' }
+      - error: 9
+        when: "*before* or *after* is a number outside the **Long** range"
+        vb6: 13
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 2147483648#' }
+      - error: 13
+        when: "*before* or *after* is **Null**, an object or **Nothing**, and the collection is not empty"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , Null' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , Null' }
+          - { decl: "Dim C As New Collection\nDim D As New Collection", setup: C.Add 1, run: 'C.Add 2, , D' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , Nothing' }
+    quiet:
+      - { decl: Dim C As New Collection, run: C.Add 1 }
+      - { decl: Dim C As New Collection, run: 'C.Add 1, ""' }
+      - { decl: Dim C As New Collection, run: C.Add Null }
+      - { decl: Dim C As New Collection, run: C.Add Nothing }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , 1' }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , , 1' }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, , "A"' }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: 'C.Add 2, , , "a"' }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "1"', run: 'C.Add 2, , "1"' }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CInt(1)' }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CSng(1)' }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CByte(1)' }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: 'C.Add 2, , CLngLng(1)', only: [tb, vba64] }
+      - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", run: 'C.Add 3, , 1.5' }
+      # an extension (owner, 2026-10-28): before Count + 1 adds at the end, after 0 at the
+      # start; VB6 and 64-bit VBA raise 9 (the page's NOTE)
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: "C.Add 2, , 2\nIf C(2) <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: "C.Add 2, , 1.5\nIf C(2) <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", run: "C.Add 3, , 3\nIf C(3) <> 3 Then Err.Raise 1001", only: tb }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: "C.Add 2, , , 0\nIf C(1) <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", run: "C.Add 3, , , 0.4\nIf C(1) <> 3 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/Collection/Item.md:
+    rows:
+      - error: 9
+        when: "*index* is a number that, rounded, is less than 1 or greater than **Count**, and the collection is not empty"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(0) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(2) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(-1) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(0.5) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(1.5) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(Empty) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(True) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: 'C.Item(#1/1/2000#)' }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(-2147483648#) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CCur(0)) }
+      - error: 9
+        when: "the collection is empty and *index* is not a string"
+        vb6: 5
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, expr: C.Item(1) }
+          - { decl: Dim C As New Collection, expr: C.Item(0) }
+          - { decl: Dim C As New Collection, expr: C.Item(-1) }
+          - { decl: Dim C As New Collection, expr: C.Item(Null) }
+          - { decl: Dim C As New Collection, expr: C.Item(Empty) }
+          - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Remove 1", expr: C.Item(1) }
+      - error: 9
+        when: "*index* is **Null**, an object, **Nothing**, an array, an error value or a number outside the **Long** range, and the collection is not empty"
+        vb6: 13
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(Null) }
+          - { decl: "Dim C As New Collection\nDim D As New Collection", setup: C.Add 1, expr: C.Item(D) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(Nothing) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(Array(1)) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CVErr(1)) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(2147483648#) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(-2147483649#) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(1E+300) }
+      - error: 9
+        when: "*index* is a **Currency**, **Decimal** or **Date** value"
+        vb6: 0
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CCur(1)) }
+          - { decl: "Dim C As New Collection\nDim N As Currency", setup: "C.Add 1\nN = 1", expr: C.Item(N) }
+          - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", expr: C.Item(CCur(2)) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CDec(1)) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CDate(1)) }
+      - error: 5
+        when: "*index* is a string that is not the key of an item"
+        cases:
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', expr: C.Item("b") }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', expr: C.Item("") }
+          - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item("1") }
+          - { decl: Dim C As New Collection, expr: C.Item("b") }
+    quiet:
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(1) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C(1) }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', expr: C.Item("a") }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', expr: C.Item("A") }
+      - { decl: Dim C As New Collection, setup: "C.Add 1\nC.Add 2", expr: C.Item(1.5) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CByte(1)) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CInt(1)) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CLng(1)) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CSng(1)) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CDbl(1)) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: C.Item(CLngLng(1)), only: [tb, vba64] }
+  Reference/Default/VBA/Collection/Remove.md:
+    rows:
+      - error: 9
+        when: "*index* is a number that, rounded, is less than 1 or greater than **Count**, and the collection is not empty"
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 0 }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 2 }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove -1 }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 0.5 }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 1.5 }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove Empty }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove True }
+      - error: 5
+        when: "*index* is a string that is not the key of an item"
+        cases:
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.Remove "b" }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.Remove "" }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove "1" }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: "C.Remove \"a\"\nC.Remove \"a\"" }
+      - error: 5
+        when: "the collection is empty"
+        cases:
+          - { decl: Dim C As New Collection, run: C.Remove 1 }
+          - { decl: Dim C As New Collection, run: C.Remove 0 }
+          - { decl: Dim C As New Collection, run: C.Remove -1 }
+          - { decl: Dim C As New Collection, run: C.Remove Null }
+          - { decl: Dim C As New Collection, run: C.Remove Empty }
+          - { decl: Dim C As New Collection, run: C.Remove "a" }
+      - error: 9
+        when: "*index* is **Null**, an object, **Nothing**, an array or a number outside the **Long** range, and the collection is not empty"
+        vb6: 13
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove Null }
+          - { decl: "Dim C As New Collection\nDim D As New Collection", setup: C.Add 1, run: C.Remove D }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove Nothing }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove Array(1) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 2147483648# }
+      - error: 9
+        when: "*index* is a **Currency**, **Decimal** or **Date** value"
+        vb6: 0
+        bug: collection-index-checks
+        cases:
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CCur(1) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CDec(1) }
+          - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CDate(1) }
+    quiet:
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove 1 }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.Remove "A" }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CInt(1) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CSng(1) }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: C.Remove CLngLng(1), only: [tb, vba64] }
+  Reference/Default/VBA/Collection/Count.md:
+    quiet:
+      - { decl: Dim C As New Collection, expr: C.Count }
+  Reference/Default/VBA/Collection/Clear.md:
+    quiet:
+      - { decl: Dim C As New Collection, run: C.Clear, only: tb }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: "C.Clear\nC.Add 2, \"a\"", only: tb }
+  Reference/Default/VBA/Collection/Exists.md:
+    rows:
+      - error: 94
+        when: "*key* is **Null**"
+        cases:
+          - { decl: Dim C As New Collection, expr: C.Exists(Null), only: tb }
+    quiet:
+      - { decl: Dim C As New Collection, expr: C.Exists("a"), only: tb }
+      - { decl: Dim C As New Collection, expr: C.Exists(""), only: tb }
+      - { decl: Dim C As New Collection, expr: C.Exists(Empty), only: tb }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "1"', run: "If Not C.Exists(1) Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/Collection/Items.md:
+    quiet:
+      - { decl: Dim C As New Collection, expr: UBound(C.Items), only: tb }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: "Result = C.Items\nResult = Result(0)", only: tb }
+  Reference/Default/VBA/Collection/Keys.md:
+    quiet:
+      - { decl: Dim C As New Collection, expr: UBound(C.Keys), only: tb }
+      - { decl: Dim C As New Collection, setup: C.Add 1, expr: UBound(C.Keys), only: tb }
+  Reference/Default/VBA/Collection/KeyCompareMode.md:
+    rows:
+      - error: 5
+        when: "*compare* is not **vbBinaryCompare** or **vbTextCompare** after rounding"
+        cases:
+          - { decl: Dim C As New Collection, run: C.KeyCompareMode = 2, only: tb }
+          - { decl: Dim C As New Collection, run: C.KeyCompareMode = -1, only: tb }
+          - { decl: Dim C As New Collection, run: C.KeyCompareMode = 1033, only: tb }
+          - { decl: Dim C As New Collection, run: C.KeyCompareMode = 1.5, only: tb }
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.KeyCompareMode = 2, only: tb }
+      - error: 5
+        when: "the mode is changed while the collection holds an item added with a key; the mode stays as it was"
+        message: "Can't change KeyCompareMode once keyed items have been added to the collection"
+        cases:
+          - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.KeyCompareMode = 0, only: tb }
+          - { decl: Dim C As New Collection, setup: "C.KeyCompareMode = 0\nC.Add 1, \"a\"", run: C.KeyCompareMode = 1, only: tb }
+      - error: 94
+        when: "*compare* is **Null**"
+        cases:
+          - { decl: Dim C As New Collection, run: C.KeyCompareMode = Null, only: tb }
+    quiet:
+      - { decl: Dim C As New Collection, expr: C.KeyCompareMode, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCompareMode = 0, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCompareMode = 1, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCompareMode = 0.5, only: tb }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.KeyCompareMode = 1, only: tb }
+      - { decl: Dim C As New Collection, setup: C.Add 1, run: C.KeyCompareMode = 0, only: tb }
+      - { decl: Dim C As New Collection, setup: "C.Add 1, \"a\"\nC.Remove 1", run: C.KeyCompareMode = 0, only: tb }
+      - { decl: Dim C As New Collection, setup: "C.Add 1, \"a\"\nC.Clear", run: C.KeyCompareMode = 0, only: tb }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: "C.KeyCompareMode = 0\nErr.Clear\nIf C.KeyCompareMode <> 1 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/Collection/KeyCountHint.md:
+    rows:
+      - error: 94
+        when: "*hint* is **Null**"
+        cases:
+          - { decl: Dim C As New Collection, run: C.KeyCountHint = Null, only: tb }
+    quiet:
+      - { decl: Dim C As New Collection, expr: C.KeyCountHint, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCountHint = 0, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCountHint = 100, only: tb }
+      - { decl: Dim C As New Collection, run: C.KeyCountHint = -1, only: tb }
+      - { decl: Dim C As New Collection, setup: 'C.Add 1, "a"', run: C.KeyCountHint = 100, only: tb }
diff --git a/errors/VBA.Compilation.yml b/errors/VBA.Compilation.yml
new file mode 100644
index 000000000..dfa3db489
--- /dev/null
+++ b/errors/VBA.Compilation.yml
@@ -0,0 +1,31 @@
+# The VBA Compilation module. Format: WIP.Errors.md.
+# Every case is `only: tb`: VB6 and VBA have none of these procedures. Each member is a
+# compile-time intrinsic or a hint to the compiler, and raises nothing at run time.
+beta: 1010
+pages:
+  Reference/Default/VBA/Compilation/CompilerVersion.md:
+    quiet:
+      - { run: "If CompilerVersion() < 1010 Then Err.Raise 1001", only: tb }
+      - { expr: CompilerVersion, only: tb }
+  Reference/Default/VBA/Compilation/CurrentComponentCLSID.md:
+    quiet:
+      - { expr: CurrentComponentCLSID(), only: tb }
+  Reference/Default/VBA/Compilation/CurrentComponentName.md:
+    quiet:
+      - { run: "If CurrentComponentName() <> \"Probe\" Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/Compilation/CurrentProcedureName.md:
+    quiet:
+      - { expr: CurrentProcedureName(), only: tb }
+  Reference/Default/VBA/Compilation/CurrentProjectName.md:
+    quiet:
+      - { expr: CurrentProjectName(), only: tb }
+  Reference/Default/VBA/Compilation/CurrentSourceFile.md:
+    quiet:
+      - { expr: CurrentSourceFile(), only: tb }
+  Reference/Default/VBA/Compilation/ProcessorArchitecture.md:
+    quiet:
+      - { run: "If ProcessorArchitecture() <> vbArchWin32 And ProcessorArchitecture() <> vbArchWin64 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/Compilation/UnrollLoop.md:
+    quiet:
+      - { decl: "Dim I As Long\nDim N As Long", run: "For I = 1 To 3\nUnrollLoop 4\nN = N + 1\nNext\nIf N <> 3 Then Err.Raise 1001", only: tb }
+      - { decl: "Dim I As Long\nDim N As Long", run: "Do While I < 3\nUnrollLoop\nI = I + 1\nLoop\nIf I <> 3 Then Err.Raise 1001", only: tb }
diff --git a/errors/VBA.ErrObject.yml b/errors/VBA.ErrObject.yml
new file mode 100644
index 000000000..70fb2c7d3
--- /dev/null
+++ b/errors/VBA.ErrObject.yml
@@ -0,0 +1,124 @@
+# The VBA ErrObject class (the Err object). Format: WIP.Errors.md.
+# A case that raises the number it was asked to raise, or that sets Number, clears Err when
+# Number is that number, so that it reports 0; a runtime that raises or keeps another
+# number reports that one. HelpFile, HelpContext and ReturnHResult have no cases: assigning
+# them fails twinBASIC's build (bugs/err-helpfile-helpcontext-codegen).
+beta: 1010
+pages:
+  Reference/Default/VBA/ErrObject/Raise.md:
+    rows:
+      - error: 5
+        when: "*number* is 0 after rounding, or **Empty**"
+        cases:
+          - { run: Err.Raise 0 }
+          - { run: Err.Raise 0.4 }
+          - { run: Err.Raise 0.5 }
+          - { run: Err.Raise Empty }
+          - { run: Err.Raise "0" }
+      - error: 94
+        when: "an argument is **Null**"
+        cases:
+          - { run: Err.Raise Null }
+          - { run: "Err.Raise 5, Null" }
+          - { run: "Err.Raise 5, , Null" }
+          - { run: "Err.Raise 5, , , Null" }
+          - { run: "Err.Raise 5, , , , Null" }
+    quiet:
+      # an extension (owner, 2026-10-28): VB6 and 64-bit VBA raise 5 (the page's NOTE)
+      - { run: "Err.Raise 65536\nIf Err.Number = 65536 Then Err.Clear", only: tb }
+      - { run: "Err.Raise 100000\nIf Err.Number = 100000 Then Err.Clear", only: tb }
+      - { run: "Err.Raise 2147483647\nIf Err.Number = 2147483647 Then Err.Clear", only: tb }
+      - { run: "Err.Raise 1\nIf Err.Number = 1 Then Err.Clear" }
+      - { run: "Err.Raise 65535\nIf Err.Number = 65535 Then Err.Clear" }
+      - { run: "Err.Raise -1\nIf Err.Number = -1 Then Err.Clear" }
+      - { run: "Err.Raise True\nIf Err.Number = -1 Then Err.Clear" }
+      - { run: "Err.Raise -2147483648#\nIf Err.Number = -2147483648# Then Err.Clear" }
+      - { run: "Err.Raise vbObjectError + 513\nIf Err.Number = vbObjectError + 513 Then Err.Clear" }
+      - { run: "Err.Raise 5, 7\nIf Err.Number = 5 Then Err.Clear" }
+      - { run: "Err.Raise 5, , 7\nIf Err.Number = 5 Then Err.Clear" }
+      - { run: "Err.Raise 5, , , , 1.5\nIf Err.Number = 5 Then Err.Clear" }
+      - { run: "Err.Raise 5, , , , -1\nIf Err.Number = 5 Then Err.Clear" }
+      # HRESULTs that every runtime raises as given
+      - { run: "Err.Raise &H80004005\nIf Err.Number = &H80004005 Then Err.Clear" }
+      - { run: "Err.Raise &H80020009\nIf Err.Number = &H80020009 Then Err.Clear" }
+      - { run: "Err.Raise &H80070002\nIf Err.Number = &H80070002 Then Err.Clear" }
+      - { run: "Err.Raise &H8000FFFF\nIf Err.Number = &H8000FFFF Then Err.Clear" }
+      - { run: "Err.Raise &H80004003\nIf Err.Number = &H80004003 Then Err.Clear" }
+      - { run: "Err.Raise vbObjectError\nIf Err.Number = vbObjectError Then Err.Clear" }
+      # HRESULTs that VB6 and 64-bit VBA raise as a VB number (the page's NOTE)
+      - { run: "Err.Raise &H80070057\nIf Err.Number = &H80070057 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H8007000E\nIf Err.Number = &H8007000E Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80070005\nIf Err.Number = &H80070005 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80004001\nIf Err.Number = &H80004001 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80004002\nIf Err.Number = &H80004002 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80004004\nIf Err.Number = &H80004004 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80020003\nIf Err.Number = &H80020003 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80020005\nIf Err.Number = &H80020005 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80020006\nIf Err.Number = &H80020006 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80020008\nIf Err.Number = &H80020008 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H8002000A\nIf Err.Number = &H8002000A Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H8002000B\nIf Err.Number = &H8002000B Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H8002000E\nIf Err.Number = &H8002000E Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80020011\nIf Err.Number = &H80020011 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80030002\nIf Err.Number = &H80030002 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80030003\nIf Err.Number = &H80030003 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80030005\nIf Err.Number = &H80030005 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80030070\nIf Err.Number = &H80030070 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80040112\nIf Err.Number = &H80040112 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H80040154\nIf Err.Number = &H80040154 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800401E3\nIf Err.Number = &H800401E3 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800401F3\nIf Err.Number = &H800401F3 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800A0005\nIf Err.Number = &H800A0005 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800A0035\nIf Err.Number = &H800A0035 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800A01A8\nIf Err.Number = &H800A01A8 Then Err.Clear", only: tb }
+      - { run: "Err.Raise &H800AFFFF\nIf Err.Number = &H800AFFFF Then Err.Clear", only: tb }
+  Reference/Default/VBA/ErrObject/Number.md:
+    rows:
+      - error: 94
+        when: "*errorNumber* is **Null**"
+        cases:
+          - { run: Err.Number = Null }
+    quiet:
+      # an extension (owner, 2026-10-28): VB6 and 64-bit VBA raise 5 (the page's NOTE)
+      - { run: "Err.Number = 65536\nIf Err.Number = 65536 Then Err.Clear", only: tb }
+      - { run: "Err.Number = 2147483647\nIf Err.Number = 2147483647 Then Err.Clear", only: tb }
+      - { run: Err.Number = 0 }
+      - { run: Err.Number = 0.4 }
+      - { run: "Err.Number = 5\nIf Err.Number = 5 Then Err.Clear" }
+      - { run: "Err.Number = 65535\nIf Err.Number = 65535 Then Err.Clear" }
+      - { run: "Err.Number = -1\nIf Err.Number = -1 Then Err.Clear" }
+      - { run: "Err.Number = vbObjectError + 513\nIf Err.Number = vbObjectError + 513 Then Err.Clear" }
+      - { run: "Err.Number = &H80004005\nIf Err.Number = &H80004005 Then Err.Clear" }
+      # HRESULTs that VB6 and 64-bit VBA store as a VB number (the page's NOTE)
+      - { run: "Err.Number = &H80070057\nIf Err.Number = &H80070057 Then Err.Clear", only: tb }
+      - { run: "Err.Number = &H80004001\nIf Err.Number = &H80004001 Then Err.Clear", only: tb }
+      - { run: "Err.Number = &H800A0035\nIf Err.Number = &H800A0035 Then Err.Clear", only: tb }
+  Reference/Default/VBA/ErrObject/Description.md:
+    rows:
+      - error: 94
+        when: "*errorDescription* is **Null**"
+        cases:
+          - { run: Err.Description = Null }
+    quiet:
+      - { run: Err.Description = "x" }
+      - { run: Err.Description = "" }
+      - { run: Err.Description = 5 }
+  Reference/Default/VBA/ErrObject/Source.md:
+    rows:
+      - error: 94
+        when: "*errorSource* is **Null**"
+        cases:
+          - { run: Err.Source = Null }
+    quiet:
+      - { run: Err.Source = "x" }
+      - { run: Err.Source = 5 }
+  Reference/Default/VBA/ErrObject/LastDllError.md:
+    quiet:
+      - Err.LastDllError
+  Reference/Default/VBA/ErrObject/LastHresult.md:
+    quiet:
+      - { expr: Err.LastHresult, only: tb }
+  Reference/Default/VBA/ErrObject/Clear.md:
+    quiet:
+      - { run: Err.Clear }
+      - { run: "Err.Raise 5\nErr.Clear" }
diff --git a/errors/VBA.FileSystem.yml b/errors/VBA.FileSystem.yml
new file mode 100644
index 000000000..8148aaa42
--- /dev/null
+++ b/errors/VBA.FileSystem.yml
@@ -0,0 +1,894 @@
+# The VBA FileSystem module. Format: WIP.Errors.md. Every case runs under the files harness, in a
+# folder of its own that is the current directory: a.txt (10 bytes), empty.txt, ro.txt
+# (read-only), hid.txt (hidden), the empty folder sub, and full, which holds f.txt.
+beta: 1010
+pages:
+  Reference/Default/VBA/FileSystem/ChDir.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*path* names no folder that exists, which includes a file, a drive that does not exist, a zero-length string, and a name with a wildcard or a character a name cannot hold"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'ChDir "nosuch"' }
+          - { run: 'ChDir "nosub\deeper"' }
+          - { run: 'ChDir ""' }
+          - { run: 'ChDir " "' }
+          - { run: 'ChDir "a.txt"' }
+          - { run: 'ChDir files_NoDrive & ":\"' }
+          - { run: 'ChDir files_NoDrive & ":\x"' }
+          - { run: 'ChDir String(300, "a")' }
+          - { run: 'ChDir "*"' }
+          - { run: 'ChDir "su?"' }
+          - { run: 'ChDir "a<b"' }
+          - { run: 'ChDir 5' }
+      - error: 94
+        when: "*path* is **Null**"
+        cases:
+          - { run: 'ChDir Null' }
+    quiet:
+      - { run: 'ChDir "sub": files_Expect CurDir$ = files_Dir & "\sub"' }
+      - { run: 'ChDir "sub\": files_Expect CurDir$ = files_Dir & "\sub"' }
+      - { run: 'ChDir "..": files_Expect CurDir$ <> files_Dir' }
+      - { run: 'ChDir files_Dir & "\full": files_Expect CurDir$ = files_Dir & "\full"' }
+  Reference/Default/VBA/FileSystem/ChDrive.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*drive* starts with a letter that no drive has"
+        vb6: 68
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'ChDrive files_NoDrive' }
+          - { run: 'ChDrive files_NoDrive & ":\"' }
+      - error: -2147467259
+        when: "*drive* starts with a digit, a space or a punctuation character"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'ChDrive "1"' }
+          - { run: 'ChDrive " "' }
+          - { run: 'ChDrive "?"' }
+          - { run: 'ChDrive "\"' }
+          - { run: 'ChDrive "@"' }
+          - { run: 'ChDrive "["' }
+          - { run: 'ChDrive 5' }
+      - error: 94
+        when: "*drive* is **Null**"
+        cases:
+          - { run: 'ChDrive Null' }
+    quiet:
+      - { run: 'ChDrive ""' }
+      - { run: 'ChDrive Empty' }
+      - { run: 'ChDrive Left$(files_Dir, 1)' }
+      - { run: 'ChDrive LCase$(Left$(files_Dir, 1))' }
+      - { run: 'ChDrive Left$(files_Dir, 1) & "xyz"' }
+      - { run: 'ChDrive Left$(files_Dir, 3)' }
+  Reference/Default/VBA/FileSystem/CurDir.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*drive* starts with a letter that no drive has"
+        vb6: 68
+        bug: file-errors-unspecified
+        cases:
+          - CurDir(files_NoDrive)
+          - CurDir$(files_NoDrive)
+      - error: -2147467259
+        when: "*drive* starts with a digit, a space or a punctuation character"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - CurDir("1")
+          - CurDir(" ")
+          - CurDir("?")
+          - CurDir("@")
+          - CurDir$("1")
+          - { expr: CurDir(5), only: tb }
+      - error: 94
+        when: "*drive* is **Null**"
+        vb6: 13
+        bug: filesystem-argument-checks
+        cases:
+          - CurDir(Null)
+          - CurDir$(Null)
+    quiet:
+      - CurDir
+      - CurDir("")
+      - CurDir$
+      - CurDir$("")
+      - CurDir(Left$(files_Dir, 1))
+      - CurDir(LCase$(Left$(files_Dir, 1)) & "xyz")
+      - { decl: Dim S As String, setup: 'S = Left$(files_Dir, 1)', expr: CurDir(S) }
+      - { decl: Dim V As Variant, setup: 'V = Left$(files_Dir, 1)', expr: CurDir(V) }
+      - { run: 'files_Expect CurDir = files_Dir' }
+  Reference/Default/VBA/FileSystem/Dir.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "**Dir** is called without *pathname* after it has returned a zero-length string"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Result = Dir("nosuch.txt")', expr: Dir() }
+          - { setup: 'Result = Dir("nosuch.txt")', expr: Dir }
+          - { setup: 'Result = Dir("a.txt")', run: 'Result = Dir(): Result = Dir()' }
+      - error: -2147467259
+        when: "*pathname* names a file and ends in a backslash"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - Dir("a.txt\")
+      - error: -2147467259
+        when: "a name in *pathname* is longer than 255 characters"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - Dir(String(256, "a"))
+          - Dir(String(300, "a"))
+      - error: 94
+        when: "*pathname* is **Null**"
+        vb6: 13
+        bug: filesystem-argument-checks
+        cases:
+          - Dir(Null)
+          - 'Dir(Null, 0)'
+      - error: 94
+        when: "*attributes* is **Null**"
+        cases:
+          - 'Dir("a.txt", Null)'
+    quiet:
+      - { run: 'files_Expect Dir("a.txt") = "a.txt"' }
+      - { run: 'files_Expect Dir("nosuch.txt") = ""' }
+      - { setup: 'Result = Dir("a.txt")', run: 'files_Expect Dir() = ""' }
+      - Dir("")
+      - 'Dir("", 8)'
+      - 'Dir("*.txt", 8)'
+      - 'Dir("*", 16)'
+      - 'Dir("*", 32)'
+      - 'Dir("*", 63)'
+      - Dir("nosub\*")
+      - Dir(files_NoDrive & ":\*")
+      - Dir("a<b")
+      - Dir("sub")
+      - 'Dir("sub", 16)'
+      - Dir(files_Dir & "\")
+      - Dir("sub\")
+      - { run: 'files_Expect Dir("hid.txt") = ""' }
+      - { run: 'files_Expect Dir("hid.txt", 2) = "hid.txt"' }
+      - { run: 'files_Expect Dir("*", -1) = Dir("*", 23)', only: tb }
+      - { run: 'files_Expect Dir("*", 64) = Dir("*", 0)', only: tb }
+      - { run: 'files_Expect Dir("h*", -1) = "hid.txt"', only: tb }
+      - { expr: 'Dir("*", 128)', only: tb }
+      - { expr: 'Dir("*", 256)', only: tb }
+      - { expr: 'Dir("*", 1024)', only: tb }
+      - { expr: 'Dir("*", 2147483647)', only: tb }
+      - { setup: 'MkDir "5"', run: 'files_Expect Dir(5, 16) = "5"', only: tb }
+      - { expr: Dir(True), only: tb }
+      - { expr: Dir(5.5), only: tb }
+  Reference/Default/VBA/FileSystem/EOF.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*filenumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - EOF(99)
+          - EOF(0)
+          - EOF(-1)
+          - EOF(256)
+          - EOF(512)
+          - { setup: 'Open "a.txt" For Input As #1', run: "Close #1\nResult = EOF(1)" }
+      - error: 94
+        when: "*filenumber* is **Null**"
+        cases:
+          - EOF(Null)
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect Not EOF(1)' }
+      - { setup: 'Open "empty.txt" For Input As #1', run: 'files_Expect EOF(1)' }
+      - { setup: 'Open "a.txt" For Output As #1', expr: EOF(1) }
+      - { setup: 'Open "a.txt" For Append As #1', expr: EOF(1) }
+      - { setup: 'Open "a.txt" For Binary As #1', expr: EOF(1) }
+      - { setup: 'Open "a.txt" For Random As #1 Len = 4', expr: EOF(1) }
+      - { setup: 'Open "a.txt" For Input As #300', expr: EOF(300) }
+  Reference/Default/VBA/FileSystem/FileAttr.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*filenumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - 'FileAttr(99, 1)'
+          - 'FileAttr(0, 1)'
+          - 'FileAttr(99, 0)'
+      - error: -2147467259
+        when: "*returntype* is not 1, after rounding"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, 2)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, 0)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, 3)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, -1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, 1.6)' }
+      - error: 94
+        when: "*filenumber* or *returntype* is **Null**"
+        cases:
+          - 'FileAttr(Null, 1)'
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'FileAttr(1, Null)' }
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect FileAttr(1, 1) = 1' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect FileAttr(1, 1.4) = 1' }
+      - { setup: 'Open "a.txt" For Output As #1', run: 'files_Expect FileAttr(1, 1) = 2' }
+      - { setup: 'Open "a.txt" For Random As #1', run: 'files_Expect FileAttr(1, 1) = 4' }
+      - { setup: 'Open "a.txt" For Append As #1', run: 'files_Expect FileAttr(1, 1) = 8' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'files_Expect FileAttr(1, 1) = 32' }
+  Reference/Default/VBA/FileSystem/FileCopy.md:
+    harness: files
+    rows:
+      - error: 53
+        when: "*source* does not exist"
+        cases:
+          - { run: 'FileCopy "nosuch.txt", "b.txt"' }
+      - error: 76
+        when: "the folder or drive named in *source* or *destination* does not exist, or *destination* ends in a backslash"
+        cases:
+          - { run: 'FileCopy "nosub\a.txt", "b.txt"' }
+          - { run: 'FileCopy "a.txt", "nosub\b.txt"' }
+          - { run: 'FileCopy files_NoDrive & ":\a.txt", "b.txt"' }
+          - { run: 'FileCopy "a.txt", files_NoDrive & ":\a.txt"' }
+          - { run: 'FileCopy "a.txt", "sub\"' }
+      - error: 55
+        when: "*source* is open with write access or locked against reading, or *destination* is open"
+        cases:
+          - { setup: 'Open "a.txt" For Binary Access Read Lock Read Write As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Append As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Output As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Binary As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Random As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Binary Access Write As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "a.txt" For Binary Access Read Write As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "b.txt" For Output As #1', run: 'FileCopy "a.txt", "b.txt"' }
+          - { setup: 'Open "empty.txt" For Input As #1', run: 'FileCopy "a.txt", "empty.txt"' }
+          - { setup: 'Open "empty.txt" For Binary Access Read As #1', run: 'FileCopy "a.txt", "empty.txt"' }
+      - error: 55
+        when: "*destination* names the same file as *source*"
+        vb6: 70
+        bug: filecopy-error-numbers
+        cases:
+          - { run: 'FileCopy "a.txt", "a.txt"' }
+          - { run: 'FileCopy "a.txt", "A.TXT"' }
+          - { run: 'FileCopy "a.txt", ".\a.txt"' }
+      - error: 55
+        when: "*source* is open **For Input** with **Lock Read**"
+        vb6: 70
+        bug: filecopy-error-numbers
+        cases:
+          - { setup: 'Open "a.txt" For Input Lock Read As #1', run: 'FileCopy "a.txt", "b.txt"' }
+      - error: 70
+        when: "*source* is a folder, or *destination* is a folder or a read-only or hidden file"
+        vb6: 75
+        bug: filecopy-error-numbers
+        cases:
+          - { run: 'FileCopy "sub", "b.txt"' }
+          - { run: 'FileCopy "full", "b.txt"' }
+          - { run: 'FileCopy "a.txt", "sub"' }
+          - { run: 'FileCopy "a.txt", "ro.txt"' }
+          - { run: 'FileCopy "a.txt", "hid.txt"' }
+      - error: -2147467259
+        when: "*source* or *destination* is a zero-length string"
+        vb6: 75
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'FileCopy "", "b.txt"' }
+          - { run: 'FileCopy "a.txt", ""' }
+      - error: -2147467259
+        when: "*source* or *destination* holds a wildcard or a character a file name cannot hold"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'FileCopy "*.txt", "b.txt"' }
+          - { run: 'FileCopy "a.tx?", "b.txt"' }
+          - { run: 'FileCopy "a.txt", "b*.txt"' }
+          - { run: 'FileCopy "a.txt", "a<b"' }
+      - error: 94
+        when: "*source* or *destination* is **Null**"
+        cases:
+          - { run: 'FileCopy Null, "b.txt"' }
+          - { run: 'FileCopy "a.txt", Null' }
+    quiet:
+      - { run: 'FileCopy "a.txt", "b.txt": files_Expect FileLen("b.txt") = 10' }
+      - { run: 'FileCopy "a.txt", "sub\b.txt": files_Expect FileLen("sub\b.txt") = 10' }
+      - { run: 'FileCopy "a.txt", "empty.txt": files_Expect FileLen("empty.txt") = 10' }
+      - { run: 'FileCopy "ro.txt", "b.txt": files_Expect FileLen("b.txt") = 1' }
+      - { run: 'FileCopy "a.txt", "ro.txt": Err.Clear: files_Expect FileLen("ro.txt") = 1' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'FileCopy "a.txt", "b.txt": files_Expect FileLen("b.txt") = 10' }
+      - { setup: 'Open "a.txt" For Input Shared As #1', run: 'FileCopy "a.txt", "b.txt"' }
+      - { setup: 'Open "a.txt" For Binary Access Read As #1', run: 'FileCopy "a.txt", "b.txt": files_Expect FileLen("b.txt") = 10', only: tb }
+      - { setup: 'Open "a.txt" For Binary Access Read Shared As #1', run: 'FileCopy "a.txt", "b.txt"', only: tb }
+      - { setup: 'Open "a.txt" For Random Access Read As #1', run: 'FileCopy "a.txt", "b.txt"', only: tb }
+      - { setup: 'Open "a.txt" For Binary Access Read Lock Write As #1', run: 'FileCopy "a.txt", "b.txt"', only: tb }
+  Reference/Default/VBA/FileSystem/FileDateTime.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - FileDateTime("nosuch.txt")
+          - FileDateTime("")
+          - FileDateTime("sub\")
+          - FileDateTime("a<b")
+          - FileDateTime(String(300, "a"))
+      - error: -2147467259
+        when: "the folder or drive named in *pathname* does not exist"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - FileDateTime("nosub\a.txt")
+          - FileDateTime(files_NoDrive & ":\a.txt")
+      - error: -2147467259
+        when: "*pathname* holds a wildcard that matches no file or folder"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - FileDateTime("z*")
+          - FileDateTime("a?txt")
+      - error: 0
+        when: "*pathname* holds a wildcard that matches a file or folder"
+        vb6: 52
+        bug: filesystem-argument-checks
+        cases:
+          - FileDateTime("*.txt")
+          - FileDateTime("e*")
+          - FileDateTime("a.tx?")
+          - FileDateTime("su*")
+      - error: 94
+        when: "*pathname* is **Null**"
+        cases:
+          - FileDateTime(Null)
+    quiet:
+      - FileDateTime("a.txt")
+      - FileDateTime("A.TXT")
+      - FileDateTime("sub")
+      - FileDateTime("hid.txt")
+      - FileDateTime(files_Dir & "\a.txt")
+      - { setup: 'Open "a.txt" For Output As #1', expr: FileDateTime("a.txt") }
+  Reference/Default/VBA/FileSystem/FileLen.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no file or folder has the name *pathname*, which includes a zero-length string, a folder named with a backslash at its end, and a name with a character a name cannot hold"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - FileLen("nosuch.txt")
+          - FileLen("")
+          - FileLen("sub\")
+          - FileLen("a<b")
+          - FileLen(String(300, "a"))
+      - error: -2147467259
+        when: "the folder or drive named in *pathname* does not exist"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - FileLen("nosub\a.txt")
+          - FileLen(files_NoDrive & ":\a.txt")
+      - error: -2147467259
+        when: "*pathname* holds a wildcard that matches no file or folder"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - FileLen("z*")
+          - FileLen("a?txt")
+      - error: 0
+        when: "*pathname* holds a wildcard that matches a file or folder"
+        vb6: 52
+        bug: filesystem-argument-checks
+        cases:
+          - FileLen("*.txt")
+          - FileLen("e*")
+          - FileLen("a.tx?")
+          - FileLen("?.txt")
+          - FileLen("su*")
+          - FileLen("h*")
+      - error: 94
+        when: "*pathname* is **Null**"
+        cases:
+          - FileLen(Null)
+    quiet:
+      - { run: 'files_Expect FileLen("a.txt") = 10' }
+      - { run: 'files_Expect FileLen("A.TXT") = 10' }
+      - { run: 'files_Expect FileLen("empty.txt") = 0' }
+      - { run: 'files_Expect FileLen(files_Dir & "\a.txt") = 10' }
+      - FileLen("sub")
+      - FileLen("hid.txt")
+      - { setup: 'Open "a.txt" For Append As #1: Print #1, "x"', run: 'files_Expect FileLen("a.txt") = 10' }
+  Reference/Default/VBA/FileSystem/FreeFile.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "every file number from 1 to 255 is in use"
+        vb6: 67
+        bug: file-errors-unspecified
+        cases:
+          - { decl: Dim I As Long, setup: 'For I = 1 To 255: Open "f" & I For Output As #I: Next', expr: FreeFile }
+          - { decl: Dim I As Long, setup: 'For I = 1 To 255: Open "f" & I For Output As #I: Next', expr: FreeFile(0) }
+      - error: 94
+        when: "*rangenumber* is **Null**"
+        cases:
+          - FreeFile(Null)
+    quiet:
+      - { run: 'files_Expect FreeFile = 1' }
+      - { run: 'files_Expect FreeFile() = 1' }
+      - { run: 'files_Expect FreeFile(0) = 1' }
+      - { run: 'files_Expect FreeFile(0.5) = 1' }
+      - { run: 'files_Expect FreeFile(1) = 256' }
+      - { run: 'files_Expect FreeFile(1.5) = 256' }
+      - { run: 'files_Expect FreeFile(2) = 256' }
+      - { run: 'files_Expect FreeFile(-1) = 256' }
+      - { run: 'files_Expect FreeFile("1") = 256' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'files_Expect FreeFile = 2' }
+      - { decl: Dim I As Long, setup: 'For I = 1 To 255: Open "f" & I For Output As #I: Next', run: 'files_Expect FreeFile(1) = 256' }
+  Reference/Default/VBA/FileSystem/GetAttr.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no file or folder has the name *pathname*, or it is a zero-length string"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - GetAttr("nosuch.txt")
+          - GetAttr("")
+          - GetAttr(String(300, "a"))
+      - error: -2147467259
+        when: "the folder or drive named in *pathname* does not exist"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - GetAttr("nosub\a.txt")
+          - GetAttr(files_NoDrive & ":\a.txt")
+          - GetAttr(files_NoDrive & ":\")
+      - error: -2147467259
+        when: "*pathname* holds a wildcard"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - GetAttr("*.txt")
+          - GetAttr("a?txt")
+          - GetAttr("a.tx?")
+      - error: -2147467259
+        when: "*pathname* holds a character a name cannot hold, or names a file with a backslash at its end"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - GetAttr("a<b")
+          - GetAttr("a.txt\")
+      - error: 94
+        when: "*pathname* is **Null**"
+        cases:
+          - GetAttr(Null)
+    quiet:
+      - { run: 'files_Expect GetAttr("ro.txt") = 1' }
+      - { run: 'files_Expect GetAttr("hid.txt") = 2' }
+      - { run: 'files_Expect GetAttr("sub") = 16' }
+      - { run: 'files_Expect GetAttr("sub\") = 16' }
+      - { run: 'files_Expect 16 = (GetAttr(files_Dir & "\") And 16)' }
+      - GetAttr("a.txt")
+      - { setup: 'Open "a.txt" For Output As #1', expr: GetAttr("a.txt") }
+  Reference/Default/VBA/FileSystem/Input.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*Number* is more characters than are left in a file open for **Input**"
+        vb6: 62
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(11, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input$(11, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Result = Input(10, #1): Result = Input(1, #1)' }
+          - { setup: 'Open "empty.txt" For Input As #1', expr: 'Input(1, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 100: Result = Input(1, #1)' }
+      - error: -2147467259
+        when: "the file is open for **Output**, **Append** or **Random**"
+        vb6: 54
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Output As #1', expr: 'Input(1, #1)' }
+          - { setup: 'Open "a.txt" For Append As #1', expr: 'Input(1, #1)' }
+          - { setup: 'Open "a.txt" For Random As #1 Len = 4', expr: 'Input(1, #1)' }
+      - error: -2147467259
+        when: "*Number* is negative, after rounding"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(-1, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(-0.6, #1)' }
+          - { setup: 'Open "a.txt" For Binary As #1', expr: 'Input(-1, #1)' }
+      - error: -2147467259
+        when: "*FileNumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - 'Input(1, #99)'
+          - 'Input$(1, #99)'
+          - 'Input(1, #0)'
+      - error: -2147467259
+        when: "*Number* is 0, after rounding"
+        vb6: 0
+        bug: filesystem-argument-checks
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(0, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input$(0, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(0.4, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(-0.4, #1)' }
+          - { setup: 'Open "empty.txt" For Input As #1', expr: 'Input(0, #1)' }
+          - { setup: 'Open "a.txt" For Binary As #1', expr: 'Input(0, #1)' }
+      - error: 94
+        when: "*Number* or *FileNumber* is **Null**"
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(Null, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input$(Null, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'Input(1, Null)' }
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect Input(1, #1) = "a"' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect Input(10, #1) = "abc" & vbCrLf & "def" & vbCrLf' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect Input$(3, 1) = "abc"' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'files_Expect Input(11, #1) = "abc" & vbCrLf & "def" & vbCrLf' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'Result = Input(10, #1): files_Expect Input(1, #1) = ""' }
+      - { setup: 'Open "a.txt" For Binary As #1', expr: 'Input(1000000, #1)' }
+      - { setup: 'Open "a.txt" For Binary Access Write As #1', expr: 'Input(1, #1)' }
+  Reference/Default/VBA/FileSystem/InputB.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*Number* is more bytes than are left in a file open for **Input**"
+        vb6: 62
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(11, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB$(11, #1)' }
+          - { setup: 'Open "empty.txt" For Input As #1', expr: 'InputB(1, #1)' }
+      - error: -2147467259
+        when: "the file is open for **Output**, **Append** or **Random**"
+        vb6: 54
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Output As #1', expr: 'InputB(1, #1)' }
+          - { setup: 'Open "a.txt" For Append As #1', expr: 'InputB(1, #1)' }
+          - { setup: 'Open "a.txt" For Random As #1 Len = 4', expr: 'InputB(1, #1)' }
+      - error: -2147467259
+        when: "*Number* is negative, after rounding"
+        vb6: 5
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(-1, #1)' }
+      - error: -2147467259
+        when: "*FileNumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - 'InputB(1, #99)'
+          - 'InputB$(1, #99)'
+      - error: 94
+        when: "*Number* or *FileNumber* is **Null**"
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(Null, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB$(Null, #1)' }
+          - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(1, Null)' }
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(1, #1)' }
+      - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(10, #1)' }
+      - { setup: 'Open "a.txt" For Input As #1', expr: 'InputB(0, #1)' }
+      - { setup: 'Open "a.txt" For Binary As #1', expr: 'InputB(10, #1)' }
+      - { setup: 'Open "a.txt" For Binary As #1', expr: 'InputB(11, #1)' }
+  Reference/Default/VBA/FileSystem/Kill.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no file matches *pathname*, which includes a folder, a folder or drive that does not exist, and a zero-length string"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'Kill "nosuch.txt"' }
+          - { run: 'Kill "*.zzz"' }
+          - { run: 'Kill "sub"' }
+          - { run: 'Kill "full"' }
+          - { run: 'Kill "sub\"' }
+          - { run: 'Kill ""' }
+          - { run: 'Kill "nosub\a.txt"' }
+          - { run: 'Kill "nosub\*"' }
+          - { run: 'Kill files_NoDrive & ":\a.txt"' }
+          - { run: 'Kill "a<b"' }
+      - error: -2147467259
+        when: "the file, or a file a wildcard matches, is read-only"
+        vb6: 75
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'Kill "ro.txt"' }
+          - { run: 'Kill "*.txt"' }
+      - error: -2147467259
+        when: "the file, or a file a wildcard matches, is open"
+        vb6: 55
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Kill "a.txt"' }
+          - { setup: 'Open "a.txt" For Output As #1', run: 'Kill "a.txt"' }
+          - { setup: 'Open "a.txt" For Binary As #1', run: 'Kill "a.txt"' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Kill "A.TXT"' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Kill files_Dir & "\a.txt"' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Kill "a.tx?"' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Kill "*.txt"' }
+      - error: 0
+        when: "*pathname* names a hidden or system file"
+        vb6: 53
+        bug: kill-hidden-system-files
+        cases:
+          - { run: 'Kill "hid.txt"' }
+          - { run: 'Kill "h*"' }
+          - { setup: 'SetAttr "a.txt", vbSystem', run: 'Kill "a.txt"' }
+          - { setup: 'SetAttr "a.txt", vbHidden + vbSystem', run: 'Kill "a.txt"' }
+      - error: 94
+        when: "*pathname* is **Null**"
+        cases:
+          - { run: 'Kill Null' }
+    quiet:
+      - { run: 'Kill "a.txt": files_Expect files_Attr("a.txt") = -1' }
+      - { run: 'Kill "A.TXT": files_Expect files_Attr("a.txt") = -1' }
+      - { setup: 'SetAttr "a.txt", vbArchive', run: 'Kill "a.txt": files_Expect files_Attr("a.txt") = -1' }
+      - { run: 'Kill "full\*": files_Expect files_Attr("full\f.txt") = -1' }
+      - { run: 'Kill "*.txt": Err.Clear: files_Expect files_Attr("a.txt") = -1 And files_Attr("empty.txt") = -1 And files_Attr("ro.txt") <> -1' }
+      - { setup: 'Open "a.txt" For Input As #1: Close #1', run: 'Kill "a.txt"' }
+      - { setup: 'SetAttr "ro.txt", vbNormal: SetAttr "hid.txt", vbNormal', run: 'Kill "*.txt": files_Expect files_Attr("ro.txt") = -1' }
+  Reference/Default/VBA/FileSystem/LOF.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*filenumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - LOF(99)
+          - LOF(0)
+          - LOF(-1)
+          - LOF(512)
+      - error: 94
+        when: "*filenumber* is **Null**"
+        cases:
+          - LOF(Null)
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect LOF(1) = 10' }
+      - { setup: 'Open "a.txt" For Output As #1', run: 'files_Expect LOF(1) = 0' }
+      - { setup: 'Open "a.txt" For Append As #1', run: 'files_Expect LOF(1) = 10' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'files_Expect LOF(1) = 10' }
+      - { setup: 'Open "a.txt" For Random As #1', run: 'files_Expect LOF(1) = 10' }
+  Reference/Default/VBA/FileSystem/Loc.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*filenumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - Loc(99)
+          - Loc(0)
+          - Loc(-1)
+          - Loc(512)
+      - error: 94
+        when: "*filenumber* is **Null**"
+        cases:
+          - Loc(Null)
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', expr: Loc(1) }
+      - { setup: 'Open "a.txt" For Output As #1', expr: Loc(1) }
+      - { setup: 'Open "a.txt" For Append As #1', expr: Loc(1) }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'Result = Input(3, #1): files_Expect Loc(1) = 3' }
+      - { setup: 'Open "a.txt" For Random As #1', expr: Loc(1) }
+  Reference/Default/VBA/FileSystem/MkDir.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*path* already exists, as a folder or as a file"
+        vb6: 75
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'MkDir "sub"' }
+          - { run: 'MkDir "a.txt"' }
+          - { run: 'MkDir "."' }
+      - error: -2147467259
+        when: "the folder or drive that would hold *path* does not exist, or *path* is a zero-length string or a name a folder cannot have"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'MkDir "nosub\new"' }
+          - { run: 'MkDir files_NoDrive & ":\new"' }
+          - { run: 'MkDir ""' }
+          - { run: 'MkDir " "' }
+          - { run: 'MkDir "a<b"' }
+          - { run: 'MkDir "a*b"' }
+          - { run: 'MkDir String(300, "a")' }
+      - error: 94
+        when: "*path* is **Null**"
+        cases:
+          - { run: 'MkDir Null' }
+    quiet:
+      - { run: 'MkDir "new": files_Expect files_Attr("new") = 16' }
+      - { run: 'MkDir "new\": files_Expect files_Attr("new") = 16' }
+      - { run: 'MkDir "sub\new": files_Expect files_Attr("sub\new") = 16' }
+      - { run: 'MkDir files_Dir & "\new": files_Expect files_Attr("new") = 16' }
+      - { run: 'MkDir 5: files_Expect files_Attr("5") = 16' }
+  Reference/Default/VBA/FileSystem/Reset.md:
+    harness: files
+    quiet:
+      - { run: Reset }
+      - { run: "Reset\nReset" }
+      - { setup: 'Open "a.txt" For Input As #1', run: "Reset\nKill \"a.txt\"" }
+      - { setup: 'Open "b.txt" For Output As #2', run: "Reset\nOpen \"b.txt\" For Output As #3" }
+      - { setup: 'Open "b.txt" For Output As #1: Print #1, "x"', run: "Reset\nfiles_Expect FileLen(\"b.txt\") = 3" }
+      - { setup: 'Open "b.txt" For Output As #300: Print #300, "x"', run: "Reset\nfiles_Expect FileLen(\"b.txt\") = 3" }
+  Reference/Default/VBA/FileSystem/RmDir.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no folder has the name *path*, which includes a file, a zero-length string, and a name with a wildcard or a character a name cannot hold"
+        vb6: 76
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'RmDir "nosuch"' }
+          - { run: 'RmDir "nosub\x"' }
+          - { run: 'RmDir files_NoDrive & ":\x"' }
+          - { run: 'RmDir "a.txt"' }
+          - { run: 'RmDir ""' }
+          - { run: 'RmDir "*"' }
+          - { run: 'RmDir "su?"' }
+          - { run: 'RmDir "a<b"' }
+      - error: -2147467259
+        when: "the folder holds a file or a folder, or it is the current directory"
+        vb6: 75
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'RmDir "full"' }
+          - { setup: 'MkDir "sub\new"', run: 'RmDir "sub"' }
+          - { run: 'RmDir "."' }
+          - { run: 'RmDir files_Dir' }
+          - { run: 'ChDir "sub": RmDir files_Dir & "\sub"' }
+      - error: 94
+        when: "*path* is **Null**"
+        cases:
+          - { run: 'RmDir Null' }
+    quiet:
+      - { run: 'RmDir "sub": files_Expect files_Attr("sub") = -1' }
+      - { run: 'RmDir "sub\": files_Expect files_Attr("sub") = -1' }
+      - { run: 'RmDir files_Dir & "\sub": files_Expect files_Attr("sub") = -1' }
+      - { run: 'Kill "full\f.txt": RmDir "full": files_Expect files_Attr("full") = -1' }
+  Reference/Default/VBA/FileSystem/Seek.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*filenumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - Seek(99)
+          - Seek(0)
+          - { run: 'Seek #99, 1' }
+          - { run: 'Seek #0, 1' }
+      - error: -2147467259
+        when: "the statement's *position* is less than 1, after rounding"
+        vb6: 63
+        bug: file-errors-unspecified
+        cases:
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 0' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, -1' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 0.4' }
+          - { setup: 'Open "a.txt" For Random As #1 Len = 4', run: 'Seek #1, 0' }
+          - { setup: 'Open "a.txt" For Output As #1', run: 'Seek #1, 0' }
+          - { setup: 'Open "a.txt" For Binary As #1', run: 'Seek #1, 0' }
+      - error: 94
+        when: "*filenumber* or *position* is **Null**"
+        cases:
+          - Seek(Null)
+          - { run: 'Seek #Null, 1' }
+          - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, Null' }
+    quiet:
+      - { setup: 'Open "a.txt" For Input As #1', run: 'files_Expect Seek(1) = 1' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 1' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 0.6: files_Expect Seek(1) = 1' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 100: files_Expect EOF(1)' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'Seek #1, 2147483647' }
+      - { setup: 'Open "a.txt" For Random As #1 Len = 4', run: 'Seek #1, 100' }
+      - { setup: 'Open "a.txt" For Output As #1', run: 'Seek #1, 5' }
+      - { setup: 'Open "a.txt" For Append As #1', run: 'Seek #1, 1' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'Seek #1, 2147483647' }
+  Reference/Default/VBA/FileSystem/SetAttr.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "no file or folder has the name *pathname*, which includes one in a folder or drive that does not exist, a zero-length string, and a name with a character a name cannot hold"
+        vb6: 53
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'SetAttr "nosuch.txt", vbReadOnly' }
+          - { run: 'SetAttr "nosub\a.txt", vbReadOnly' }
+          - { run: 'SetAttr files_NoDrive & ":\a.txt", vbReadOnly' }
+          - { run: 'SetAttr "", vbReadOnly' }
+          - { run: 'SetAttr "a<b", vbReadOnly' }
+      - error: -2147467259
+        when: "*pathname* holds a wildcard"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'SetAttr "*.txt", vbReadOnly' }
+      - error: 0
+        when: "the file is open for **Output**, **Append**, **Binary** or **Random**"
+        vb6: 55
+        bug: setattr-open-file-no-error
+        cases:
+          - { setup: 'Open "a.txt" For Output As #1', run: 'SetAttr "a.txt", vbReadOnly' }
+          - { setup: 'Open "a.txt" For Append As #1', run: 'SetAttr "a.txt", vbReadOnly' }
+          - { setup: 'Open "a.txt" For Binary As #1', run: 'SetAttr "a.txt", vbReadOnly' }
+          - { setup: 'Open "a.txt" For Random As #1', run: 'SetAttr "a.txt", vbReadOnly' }
+      - error: 94
+        when: "*pathname* or *attributes* is **Null**"
+        cases:
+          - { run: 'SetAttr Null, vbReadOnly' }
+          - { run: 'SetAttr "a.txt", Null' }
+    quiet:
+      - { run: 'SetAttr "a.txt", vbReadOnly: files_Expect files_Attr("a.txt") = 1' }
+      - { run: 'SetAttr "a.txt", vbNormal: files_Expect files_Attr("a.txt") = 128' }
+      - { run: 'SetAttr "a.txt", vbHidden: files_Expect files_Attr("a.txt") = 2' }
+      - { run: 'SetAttr "a.txt", vbSystem: files_Expect files_Attr("a.txt") = 4' }
+      - { run: 'SetAttr "a.txt", vbArchive: files_Expect files_Attr("a.txt") = 32' }
+      - { run: 'SetAttr "a.txt", 39: files_Expect files_Attr("a.txt") = 39' }
+      - { run: 'SetAttr "a.txt", 1.4: files_Expect files_Attr("a.txt") = 1' }
+      - { run: 'SetAttr "ro.txt", vbNormal: files_Expect files_Attr("ro.txt") = 128' }
+      - { run: 'SetAttr "sub", vbNormal: files_Expect files_Attr("sub") = 16' }
+      - { run: 'SetAttr "sub", vbReadOnly: files_Expect files_Attr("sub") = 17' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'SetAttr "a.txt", vbReadOnly' }
+      - { run: 'SetAttr "a.txt", vbDirectory: files_Expect files_Attr("a.txt") = 128', only: tb }
+      - { run: 'SetAttr "a.txt", vbVolume + vbReadOnly: files_Expect files_Attr("a.txt") = 1', only: tb }
+      - { run: 'SetAttr "a.txt", 256: files_Expect files_Attr("a.txt") = 256', only: tb }
+      - { run: 'SetAttr "a.txt", 8192: files_Expect files_Attr("a.txt") = 8192', only: tb }
+      - { run: 'SetAttr "a.txt", 39 + 8192: files_Expect files_Attr("a.txt") = 39 + 8192', only: tb }
+      - { run: 'SetAttr "a.txt", -1', only: tb }
+      - { run: 'SetAttr "sub", vbDirectory: files_Expect files_Attr("sub") = 16', only: tb }
+  Reference/Default/VBA/FileSystem/Width.md:
+    harness: files
+    rows:
+      - error: -2147467259
+        when: "*FileNumber* is not the number of an open file"
+        vb6: 52
+        bug: file-errors-unspecified
+        cases:
+          - { run: 'Width #99, 5' }
+          - { run: 'Width #0, 5' }
+      - error: 0
+        when: "*Width* is negative, after rounding"
+        vb6: 5
+        bug: filesystem-argument-checks
+        cases:
+          - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, -1' }
+          - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, -0.6' }
+          - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, -32768' }
+      - error: 94
+        when: "*Width* is **Null**"
+        cases:
+          - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, Null' }
+    quiet:
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 5' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 0' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, -0.4' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 255' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 255.4' }
+      - { setup: 'Open "a.txt" For Input As #1', run: 'Width #1, 5' }
+      - { setup: 'Open "a.txt" For Append As #1', run: 'Width #1, 5' }
+      - { setup: 'Open "a.txt" For Binary As #1', run: 'Width #1, 5' }
+      - { setup: 'Open "a.txt" For Random As #1', run: 'Width #1, 5' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 3: Print #1, "ab"; "cd"; "ef";: Close #1: files_Expect FileLen("b.txt") = 10' }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 255.6', only: tb }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 32767', only: tb }
+      - { setup: 'Open "b.txt" For Output As #1', run: 'Width #1, 300: Print #1, String(200, "a"); String(200, "a");: Close #1: files_Expect FileLen("b.txt") = 402', only: tb }
diff --git a/errors/VBA.Financial.yml b/errors/VBA.Financial.yml
new file mode 100644
index 000000000..6fd856999
--- /dev/null
+++ b/errors/VBA.Financial.yml
@@ -0,0 +1,775 @@
+# The VBA Financial module. Format: WIP.Errors.md.
+beta: 1010
+pages:
+  Reference/Default/VBA/Financial/DDB.md:
+    rows:
+      - error: -2147467259
+        when: "*life* is 0 or less, *period* is 0 or less or greater than *life*, *salvage* is less than 0, or *factor* is 0 or less (**Empty** and **True** included)"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - DDB(1000, 100, 0, 1)
+          - DDB(1000, 100, -5, 1)
+          - DDB(1000, 100, 5, 0)
+          - DDB(1000, 100, 5, -1)
+          - DDB(1000, 100, 5, 5.0000001)
+          - DDB(1000, 100, 5, 6)
+          - DDB(1000, -100, 5, 1)
+          - DDB(1000, 100, 5, 1, 0)
+          - DDB(1000, 100, 5, 1, -1)
+          - DDB(1000, 100, 5, 1, Empty)
+          - DDB(1000, 100, 5, 1, True)
+      - error: -2147467259
+        when: "*life* is greater than 0 and less than 1"
+        vb6: 0
+        bug: financial-argument-checks
+        cases:
+          - DDB(1000, 100, 0.5, 0.5)
+          - DDB(1000, 100, 0.9, 0.9)
+          - DDB(1000, 100, 0.999999, 0.1)
+      - error: 13
+        when: "*factor* is not a number or a string that holds one"
+        cases:
+          - DDB(1000, 100, 5, 1, "abc")
+          - DDB(1000, 100, 5, 1, CVErr(5))
+          - DDB(1000, 100, 5, 1, Array(1))
+      - error: 13
+        when: "*factor* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - DDB(1000, 100, 5, 1, Null)
+      - error: 94
+        when: "*cost*, *salvage*, *life* or *period* is **Null**"
+        cases:
+          - DDB(Null, 100, 5, 1)
+          - DDB(1000, Null, 5, 1)
+          - DDB(1000, 100, Null, 1)
+          - DDB(1000, 100, 5, Null)
+    quiet:
+      - DDB(1000, 100, 5, 1)
+      - DDB(1000, 100, 5, 5)
+      - DDB(1000, 100, 5, 0.5)
+      - DDB(1000, 100, 1, 1)
+      - DDB(1000, 100, 1, 0.5)
+      - DDB(1000, 100, 1.5, 1)
+      - DDB(-1000, 100, 5, 1)
+      - DDB(100, 1000, 5, 1)
+      - DDB(0, 0, 5, 1)
+      - DDB(1000, 100, 5, 1, 1)
+      - DDB(1000, 100, 5, 1, 0.5)
+      - DDB(1000, 100, 5, 1, 10)
+      - DDB(1000, 100, 5, 1, 1E+300)
+      - DDB(1000, 100, 5, 1, "3")
+  Reference/Default/VBA/Financial/FV.md:
+    rows:
+      - error: 5
+        when: "*rate* is -1 and *nper* is less than 0"
+        vb6: 11
+        vba64: 6
+        bug: financial-argument-checks
+        cases:
+          - FV(-1, -1, -100)
+          - FV(-1, -1, 0)
+          - FV(-1, -2, -100)
+          - FV(-1, -0.5, -100)
+          - FV(-1, -1, -100, 0, 1)
+      - error: 6
+        when: the result is beyond the range of a **Double**
+        cases:
+          - FV(10, 1000, -100)
+          - FV(1, 2000, -100)
+          - FV(-0.5, -2000, -100)
+          - FV(1E+300, 2, -100)
+      - error: 13
+        when: "*pv* or *type* is a string that is not a number, or an error value"
+        cases:
+          - FV(0.01, 10, -100, "abc")
+          - FV(0.01, 10, -100, 0, "abc")
+          - FV(0.01, 10, -100, CVErr(5))
+      - error: 13
+        when: "*pv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - FV(0.01, 10, -100, Null)
+          - FV(0.01, 10, -100, 0, Null)
+      - error: 94
+        when: "*rate*, *nper* or *pmt* is **Null**"
+        cases:
+          - FV(Null, 10, -100)
+          - FV(0.01, Null, -100)
+          - FV(0.01, 10, Null)
+    quiet:
+      - FV(0.01, 10, -100)
+      - FV(0, 10, -100)
+      - FV(-1, 10, -100)
+      - FV(-2, 10, -100)
+      - FV(-1, 0, -100)
+      - FV(0.01, 0, -100)
+      - FV(0.01, -10, -100)
+      - FV(0.01, 10.5, -100)
+      - FV(0.01, 10, -100, 1000)
+      - FV(0.01, 10, -100, Empty)
+      - FV(0.01, 10, -100, "5")
+      - FV(0.01, 10, -100, 0, 1)
+      - FV(0.01, 10, -100, 0, 2)
+      - FV(0.01, 10, -100, 0, -1)
+      - FV(0.01, 10, -100, 0, 0.5)
+      - FV(0.01, 10, -100, 0, True)
+      - FV(0.01, 10, -100, 0, Empty)
+      - FV(0.01, 10, -100, 0, "1")
+  Reference/Default/VBA/Financial/IPmt.md:
+    rows:
+      - error: 0
+        when: "*per* is 0 or less, or *nper* + 1 or more"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - IPmt(0.01, 0, 10, 1000)
+          - IPmt(0.01, -1, 10, 1000)
+          - IPmt(0.01, 11, 10, 1000)
+          - IPmt(0.01, 11.5, 10.5, 1000)
+          - IPmt(0.01, 1.5, 0.5, 1000)
+      - error: -2147467259
+        when: "*nper* is 0 or less"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - IPmt(0.01, 1, 0, 1000)
+          - IPmt(0.01, 1, -10, 1000)
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - IPmt(0.01, 1, 10, 1000, "abc")
+          - IPmt(0.01, 1, 10, 1000, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - IPmt(0.01, 1, 10, 1000, Null)
+          - IPmt(0.01, 1, 10, 1000, 0, Null)
+      - error: 94
+        when: "*rate*, *per*, *nper* or *pv* is **Null**"
+        cases:
+          - IPmt(Null, 1, 10, 1000)
+          - IPmt(0.01, Null, 10, 1000)
+          - IPmt(0.01, 1, Null, 1000)
+          - IPmt(0.01, 1, 10, Null)
+    quiet:
+      - IPmt(0.01, 1, 10, 1000)
+      - IPmt(0.01, 10, 10, 1000)
+      - IPmt(0.01, 1E-10, 10, 1000)
+      - IPmt(0.01, 0.5, 10, 1000)
+      - IPmt(0.01, 10.5, 10, 1000)
+      - IPmt(0.01, 10.9999999, 10, 1000)
+      - IPmt(0.01, 1, 10.5, 1000)
+      - IPmt(0.01, 11.4, 10.5, 1000)
+      - IPmt(0.01, 1.4, 0.5, 1000)
+      - IPmt(0, 1, 10, 1000)
+      - IPmt(-1, 1, 10, 1000)
+      - IPmt(-1, 2, 10, 1000)
+      - IPmt(0.01, 1, 10, 1000, 100)
+      - IPmt(0.01, 1, 10, 1000, 0, 1)
+      - IPmt(0.01, 1, 10, 1000, 0, 2)
+      - IPmt(0.01, 1, 10, 1000, 0, -1)
+      - IPmt(0.01, 1, 10, 1000, 0, 0.5)
+  Reference/Default/VBA/Financial/IRR.md:
+    rows:
+      - error: -2147467259
+        when: "*values* has no element less than 0 or none greater than 0, or **IRR** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included)"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - decl: Dim A(1) As Double
+            setup: "A(0) = 100\nA(1) = 110"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = -110"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            expr: IRR(A)
+          - decl: Dim A(0) As Double
+            setup: A(0) = -100
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 0"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = 0\nA(1) = 110"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 1E+300"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 0.0000001"
+            expr: IRR(A)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 110"
+            expr: IRR(A, -1)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 110"
+            expr: IRR(A, -2)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 110"
+            expr: IRR(A, 100)
+      - error: -2147418113
+        when: "*values* has more than one dimension"
+        vb6: 5
+        bug: financial-array-arguments
+        cases:
+          - decl: Dim A(1, 1) As Double
+            setup: "A(0, 0) = -100\nA(1, 0) = 110\nA(0, 1) = -100\nA(1, 1) = 110"
+            expr: IRR(A)
+      - error: 13
+        when: "*guess* is a string that is not a number"
+        cases:
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 110"
+            expr: IRR(A, "abc")
+      - error: 94
+        when: "*guess* is **Null**"
+        cases:
+          - decl: Dim A(1) As Double
+            setup: "A(0) = -100\nA(1) = 110"
+            expr: IRR(A, Null)
+    quiet:
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = 110"
+        expr: IRR(A)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: IRR(A)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = 110\nA(1) = -100"
+        expr: IRR(A)
+      - decl: Dim A(1 To 2) As Double
+        setup: "A(1) = -100\nA(2) = 110"
+        expr: IRR(A)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = 110"
+        expr: IRR(A, 0)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = 110"
+        expr: IRR(A, -0.99)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = 110"
+        expr: IRR(A, Empty)
+  Reference/Default/VBA/Financial/MIRR.md:
+    rows:
+      - error: 0
+        when: "*values* has one element, or *finance_rate* or *reinvest_rate* is -1"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - decl: Dim A(0) As Double
+            setup: A(0) = -100
+            expr: MIRR(A, 0.1, 0.1)
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: MIRR(A, -1, 0.1)
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: MIRR(A, 0.1, -1)
+      - error: 0
+        when: "*values* has no element less than 0"
+        vb6: 11
+        bug: financial-argument-checks
+        cases:
+          - decl: Dim A(1) As Double
+            setup: "A(0) = 100\nA(1) = 110"
+            expr: MIRR(A, 0.1, 0.1)
+          - decl: Dim A(1) As Double
+            expr: MIRR(A, 0.1, 0.1)
+          - decl: Dim A(1) As Double
+            setup: "A(0) = 0\nA(1) = 110"
+            expr: MIRR(A, 0.1, 0.1)
+      - error: -2147418113
+        when: "*values* has more than one dimension"
+        vb6: 5
+        bug: financial-array-arguments
+        cases:
+          - decl: Dim A(1, 1) As Double
+            setup: "A(0, 0) = -100\nA(1, 0) = 110\nA(0, 1) = -100\nA(1, 1) = 110"
+            expr: MIRR(A, 0.1, 0.1)
+      - error: 94
+        when: "*finance_rate* or *reinvest_rate* is **Null**"
+        cases:
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: MIRR(A, Null, 0.1)
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: MIRR(A, 0.1, Null)
+    quiet:
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: MIRR(A, 0.1, 0.1)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = -110"
+        expr: MIRR(A, 0.1, 0.1)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = 0"
+        expr: MIRR(A, 0.1, 0.1)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = 110\nA(1) = -100"
+        expr: MIRR(A, 0.1, 0.1)
+      - decl: Dim A(1 To 3) As Double
+        setup: "A(1) = -100\nA(2) = 50\nA(3) = 60"
+        expr: MIRR(A, 0.1, 0.1)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: MIRR(A, -2, -2)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: MIRR(A, -0.9999, 0.1)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: MIRR(A, 0, 0)
+  Reference/Default/VBA/Financial/NPV.md:
+    rows:
+      - error: 0
+        when: "*rate* is -1"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: NPV(-1, A)
+      - error: -2147418113
+        when: "*values* has more than one dimension"
+        vb6: 5
+        bug: financial-array-arguments
+        cases:
+          - decl: Dim A(1, 1) As Double
+            setup: "A(0, 0) = -100\nA(1, 0) = 110\nA(0, 1) = -100\nA(1, 1) = 110"
+            expr: NPV(0.1, A)
+      - error: 94
+        when: "*rate* is **Null**"
+        cases:
+          - decl: Dim A(2) As Double
+            setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+            expr: NPV(Null, A)
+    quiet:
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: NPV(0.1, A)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = 100\nA(1) = 110"
+        expr: NPV(0.1, A)
+      - decl: Dim A(1) As Double
+        setup: "A(0) = -100\nA(1) = -110"
+        expr: NPV(0.1, A)
+      - decl: Dim A(1) As Double
+        expr: NPV(0.1, A)
+      - decl: Dim A(0) As Double
+        setup: A(0) = -100
+        expr: NPV(0.1, A)
+      - decl: Dim A(1 To 3) As Double
+        setup: "A(1) = -100\nA(2) = 50\nA(3) = 60"
+        expr: NPV(0.1, A)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: NPV(0, A)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: NPV(-2, A)
+      - decl: Dim A(2) As Double
+        setup: "A(0) = -100\nA(1) = 50\nA(2) = 60"
+        expr: NPV(-0.9999999, A)
+  Reference/Default/VBA/Financial/NPer.md:
+    rows:
+      - error: 6
+        when: "*rate* and *pmt* are of opposite signs, as in a loan or a savings plan, and a number of periods exists"
+        vb6: 0
+        bug: nper-opposite-signs-overflow
+        cases:
+          - NPer(0.01, -100, 1000)
+          - NPer(0.05, -100, 1000)
+          - NPer(0.01, -200, 1000)
+          - NPer(0.1 / 12, -500, 20000)
+          - NPer(0.01, -100, 1000, 100)
+          - NPer(0.01, -100, 1000, 0, 1)
+          - NPer(0.01, -100, 1000, 0, 2)
+          - NPer(0.01, -100, 0, 1000)
+          - NPer(0.01, -100, -1000)
+          - NPer(-0.5, 100, -1000)
+      - error: 6
+        when: "no number of periods exists, as when *pmt* does not cover the interest, or *rate* is -1 and *pmt* is greater than 0"
+        vb6: 5
+        bug: nper-opposite-signs-overflow
+        cases:
+          - NPer(0.01, -1, 1000)
+          - NPer(-2, -100, 1000)
+          - NPer(-1, 100, -1000)
+      - error: 11
+        when: "*pmt* is 0 and *rate* is not 0, or *rate* is -1 and *pmt* is less than 0"
+        vb6: 5
+        bug: nper-opposite-signs-overflow
+        cases:
+          - NPer(0.01, 0, 1000)
+          - NPer(0.01, 0, 0)
+          - NPer(-1, -100, 1000)
+          - NPer(-1, -100, 1000, 0, 1)
+      - error: -2147467259
+        when: "*rate* and *pmt* are both 0"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - NPer(0, 0, 1000)
+          - NPer(0, 0, 0)
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - NPer(0.01, -100, 1000, "abc")
+          - NPer(0.01, -100, 1000, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - NPer(0.01, -100, 1000, Null)
+          - NPer(0.01, -100, 1000, 0, Null)
+      - error: 94
+        when: "*rate*, *pmt* or *pv* is **Null**"
+        cases:
+          - NPer(Null, -100, 1000)
+          - NPer(0.01, Null, 1000)
+          - NPer(0.01, -100, Null)
+    quiet:
+      - NPer(0.01, 100, 1000)
+      - NPer(0.01, 100, -1000)
+      - NPer(0.05, 100, -1000)
+      - NPer(0.01, 100, -1000, 100)
+      - NPer(0.01, 100, -1000, -100)
+      - NPer(0.01, 100, -1000, 0, 1)
+      - NPer(0.01, 100, -1000, 0, 2)
+      - NPer(0.01, 100, 0, -1000)
+      - NPer(0, -100, 1000)
+      - NPer(-0.5, -100, 1000)
+  Reference/Default/VBA/Financial/PPmt.md:
+    rows:
+      - error: 0
+        when: "*per* is 0 or less, or *nper* + 1 or more"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - PPmt(0.01, 0, 10, 1000)
+          - PPmt(0.01, -1, 10, 1000)
+          - PPmt(0.01, 11, 10, 1000)
+      - error: 11
+        when: "*nper* is 0"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - PPmt(0.01, 1, 0, 1000)
+      - error: -2147467259
+        when: "*nper* is less than 0"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - PPmt(0.01, 1, -10, 1000)
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - PPmt(0.01, 1, 10, 1000, "abc")
+          - PPmt(0.01, 1, 10, 1000, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - PPmt(0.01, 1, 10, 1000, Null)
+          - PPmt(0.01, 1, 10, 1000, 0, Null)
+      - error: 94
+        when: "*rate*, *per*, *nper* or *pv* is **Null**"
+        cases:
+          - PPmt(Null, 1, 10, 1000)
+          - PPmt(0.01, Null, 10, 1000)
+          - PPmt(0.01, 1, Null, 1000)
+          - PPmt(0.01, 1, 10, Null)
+    quiet:
+      - PPmt(0.01, 1, 10, 1000)
+      - PPmt(0.01, 10, 10, 1000)
+      - PPmt(0.01, 0.5, 10, 1000)
+      - PPmt(0.01, 10.5, 10, 1000)
+      - PPmt(0.01, 1, 10.5, 1000)
+      - PPmt(0.01, 1, 0.5, 1000)
+      - PPmt(0, 1, 10, 1000)
+      - PPmt(-1, 1, 10, 1000)
+      - PPmt(0.01, 1, 10, 1000, 100)
+      - PPmt(0.01, 1, 10, 1000, 0, 2)
+      - PPmt(0.01, 1, 10, 1000, 0, -1)
+      - PPmt(0.01, 1, 10, 1000, 0, 0.5)
+  Reference/Default/VBA/Financial/PV.md:
+    rows:
+      - error: -2147467259
+        when: "*rate* is -1 and *nper* is 0"
+        vb6: 0
+        bug: financial-argument-checks
+        cases:
+          - PV(-1, 0, -100)
+      - error: -2147467259
+        when: "*rate* is -1 and *nper* is greater than 0"
+        vb6: 0
+        vba64: 11
+        bug: financial-argument-checks
+        cases:
+          - PV(-1, 10, -100)
+          - PV(-1, 1, -100)
+          - PV(-1, 10, 0, 100)
+      - error: -2147467259
+        when: "*rate* is -1 and *nper* is less than 0"
+        vb6: 0
+        vba64: 6
+        bug: financial-argument-checks
+        cases:
+          - PV(-1, -1, -100)
+      - error: 11
+        when: "the result is beyond the range of a **Double**"
+        # An extension (owner, 2026-10-28): as 64-bit VBA; VB6 returns infinity (a NOTE in the prose).
+        cases:
+          - { expr: 'PV(-0.99999999, 1000, -100)', only: [tb, vba64] }
+          - { expr: 'PV(-0.5, 2000, -100)', only: [tb, vba64] }
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - PV(0.01, 10, -100, "abc")
+          - PV(0.01, 10, -100, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - PV(0.01, 10, -100, Null)
+          - PV(0.01, 10, -100, 0, Null)
+      - error: 94
+        when: "*rate*, *nper* or *pmt* is **Null**"
+        cases:
+          - PV(Null, 10, -100)
+          - PV(0.01, Null, -100)
+          - PV(0.01, 10, Null)
+    quiet:
+      - PV(0.01, 10, -100)
+      - PV(0, 10, -100)
+      - PV(-2, 10, -100)
+      - PV(0.01, 0, -100)
+      - PV(0, 0, -100)
+      - PV(0.01, -10, -100)
+      - PV(0.01, 10.5, -100)
+      - PV(0.01, 10, -100, 1000)
+      - PV(0.01, 10, -100, 0, 2)
+      - PV(0.01, 10, -100, 0, -1)
+      - PV(0.01, 10, -100, 0, 0.5)
+  Reference/Default/VBA/Financial/Pmt.md:
+    rows:
+      - error: 6
+        when: "*rate* is -1 and *type* is 1 or more"
+        cases:
+          - Pmt(-1, 10, 1000, 0, 1)
+          - Pmt(-1, 10, 1000, 0, 2)
+      - error: 11
+        when: "*rate* is -2 and *nper* is an even number"
+        cases:
+          - Pmt(-2, 10, 1000)
+      - error: 11
+        when: "*nper* is 0 and *rate* is not 0"
+        vb6: 5
+        bug: financial-argument-checks
+        cases:
+          - Pmt(0.01, 0, 1000)
+          - Pmt(-1, 0, 1000)
+      - error: -2147467259
+        when: "*nper* and *rate* are both 0"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - Pmt(0, 0, 1000)
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - Pmt(0.01, 10, 1000, "abc")
+          - Pmt(0.01, 10, 1000, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - Pmt(0.01, 10, 1000, Null)
+          - Pmt(0.01, 10, 1000, 0, Null)
+      - error: 94
+        when: "*rate*, *nper* or *pv* is **Null**"
+        cases:
+          - Pmt(Null, 10, 1000)
+          - Pmt(0.01, Null, 1000)
+          - Pmt(0.01, 10, Null)
+    quiet:
+      - Pmt(0.01, 10, 1000)
+      - Pmt(0, 10, 1000)
+      - Pmt(0.01, -10, 1000)
+      - Pmt(0.01, 10.5, 1000)
+      - Pmt(0.01, 0.5, 1000)
+      - Pmt(-1, 10, 1000)
+      - Pmt(-2, 3, 1000)
+      - Pmt(-1, 10, 1000, 0, 0.5)
+      - Pmt(-0.5, 10, 1000, 0, 2)
+      - Pmt(0.01, 10, 0)
+      - Pmt(0.01, 10, 1000, 100)
+      - Pmt(0.01, 10, 1000, 0, 2)
+      - Pmt(0.01, 10, 1000, 0, -1)
+      - Pmt(0.01, 10, 1000, 0, 0.5)
+  Reference/Default/VBA/Financial/Rate.md:
+    rows:
+      - error: -2147467259
+        when: "a rate exists (twinBASIC finds one only for a few annuities, none of them with a *pmt* other than 0)"
+        vb6: 0
+        bug: rate-fails
+        cases:
+          - Rate(10, -100, 800)
+          - Rate(10, -100, 1100)
+          - Rate(48, -500, 20000)
+          - Rate(360, -600, 100000)
+          - Rate(1, -110, 100)
+          - Rate(2, -60, 100)
+          - Rate(1, -100, 1000)
+          - Rate(10, 100, -800)
+          - Rate(10, -100, 0, 1200)
+          - Rate(10, 0, 1000, -2000)
+          - Rate(10, 0, -1000, 2000)
+          - Rate(0.5, -100, 10)
+          - Rate(10, -100, 800, 0, 1)
+          - Rate(10, -100, 800, 0, 2)
+          - Rate(10, -100, 800, 0, 0.5)
+          - Rate(10, -100, 800, 0, 0, 0.04)
+          - Rate(10, -100, 800, 0, 0, 0)
+          - Rate(10, -100, 800, 0, 0, Empty)
+      - error: -2147467259
+        when: "**Rate** finds no result in 20 tries from *guess* (a *guess* of -1 or less, or far from the result, included), or *nper* is 0 or less"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - Rate(10, -100, 1000)
+          - Rate(10, 100, 1000)
+          - Rate(10, -100, -1000)
+          - Rate(10, 0, 0)
+          - Rate(0, -100, 1000)
+          - Rate(-10, -100, 1000)
+          - Rate(10, -100, 800, 0, 0, -1)
+          - Rate(10, -100, 800, 0, 0, -2)
+          - Rate(10, -100, 800, 0, 0, 100)
+      - error: -2147467259
+        when: "*nper* is less than 1 and the result is beyond the range of a **Double**"
+        vb6: 6
+        bug: argument-errors-unspecified-error
+        cases:
+          - Rate(0.5, -100, 1000)
+          - Rate(0.9, -100, 1000)
+      - error: 5
+        when: "*nper* is less than 1 and *pmt* is 0"
+        vb6: 0
+        bug: rate-fails
+        cases:
+          - Rate(0.5, 0, 100, -110)
+          - Rate(0.9, 0, 100, -110)
+      - error: 0
+        when: "*guess* is **Null**"
+        vb6: 94
+        bug: rate-fails
+        cases:
+          - Rate(1, 0, 100, -110, 0, Null)
+      - error: 0
+        when: "*guess* is a string that is not a number, or an error value"
+        vb6: 13
+        bug: rate-fails
+        cases:
+          - Rate(1, 0, 100, -110, 0, "abc")
+          - Rate(1, 0, 100, -110, 0, CVErr(5))
+      - error: 13
+        when: "*fv* or *type* is a string that is not a number"
+        cases:
+          - Rate(10, -100, 800, "abc")
+          - Rate(10, -100, 800, 0, "abc")
+      - error: 13
+        when: "*fv* or *type* is **Null**"
+        vb6: 94
+        bug: financial-null-optional-argument
+        cases:
+          - Rate(1, 0, 100, -110, Null)
+          - Rate(10, -100, 800, 0, Null)
+      - error: 94
+        when: "*nper*, *pmt* or *pv* is **Null**"
+        cases:
+          - Rate(Null, -100, 800)
+          - Rate(10, Null, 800)
+          - Rate(10, -100, Null)
+    quiet:
+      - Rate(1, 0, 100, -110)
+      - Rate(2, 0, 100, -121)
+      - Rate(1, 0, 100, -110, 1)
+      - Rate(1, 0, 100, -110, 0, Empty)
+      - Rate(1, 0, 100, -110, 0, -1)
+      - Rate(1, 0, 100, -110, 0, 100)
+  Reference/Default/VBA/Financial/SLN.md:
+    rows:
+      - error: -2147467259
+        when: "*life* is 0"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - SLN(1000, 100, 0)
+          - SLN(0, 0, 0)
+      - error: 0
+        when: "the result is beyond the range of a **Double** (twinBASIC returns infinity)"
+        vba64: 6
+        bug: financial-argument-checks
+        cases:
+          - SLN(1000, 100, 1E-308)
+          - SLN(1E+308, -1E+308, 1)
+          - SLN(1E+308, -1E+308, 1E-308)
+      - error: 94
+        when: "*cost*, *salvage* or *life* is **Null**"
+        cases:
+          - SLN(Null, 100, 5)
+          - SLN(1000, Null, 5)
+          - SLN(1000, 100, Null)
+    quiet:
+      - SLN(1000, 100, 5)
+      - SLN(1000, 100, -5)
+      - SLN(1000, 100, 0.5)
+      - SLN(-1000, 100, 5)
+      - SLN(1000, -100, 5)
+      - SLN(100, 1000, 5)
+      - SLN(0, 0, 5)
+      - SLN(Empty, Empty, 5)
+  Reference/Default/VBA/Financial/SYD.md:
+    rows:
+      - error: -2147467259
+        when: "*life* is 0 or less, *period* is 0 or less or greater than *life*, or *salvage* is less than 0"
+        vb6: 5
+        bug: argument-errors-unspecified-error
+        cases:
+          - SYD(1000, 100, 0, 1)
+          - SYD(1000, 100, -5, 1)
+          - SYD(1000, 100, 5, 0)
+          - SYD(1000, 100, 5, -1)
+          - SYD(1000, 100, 5, 5.0000001)
+          - SYD(1000, 100, 5, 5.5)
+          - SYD(1000, 100, 5, 6)
+          - SYD(1000, -100, 5, 1)
+      - error: 94
+        when: "*cost*, *salvage*, *life* or *period* is **Null**"
+        cases:
+          - SYD(Null, 100, 5, 1)
+          - SYD(1000, Null, 5, 1)
+          - SYD(1000, 100, Null, 1)
+          - SYD(1000, 100, 5, Null)
+    quiet:
+      - SYD(1000, 100, 5, 1)
+      - SYD(1000, 100, 5, 5)
+      - SYD(1000, 100, 5, 0.5)
+      - SYD(1000, 100, 0.5, 0.5)
+      - SYD(1000, 100, 2.5, 1)
+      - SYD(-1000, 100, 5, 1)
+      - SYD(100, 1000, 5, 1)
+      - SYD(0, 0, 5, 1)
diff --git a/errors/VBA.HiddenModule.yml b/errors/VBA.HiddenModule.yml
new file mode 100644
index 000000000..4e4319e92
--- /dev/null
+++ b/errors/VBA.HiddenModule.yml
@@ -0,0 +1,552 @@
+# The VBA (Default) module, _HiddenModule. Format: WIP.Errors.md.
+# Every case is `only: tb`: VB6 and VBA have none of these procedures.
+# No case for what crashes (an access violation, 32-bit and 64-bit; the pages' WARNINGs):
+# ConvertIconToBitmap of Nothing, GetInheritedOwner of Nothing or of an object that is not a
+# control, a Let of RuntimeCreateGetMessageHook's result into a Variant, an address of 0 to the
+# GetMem, PutMem and vbaCopyBytes procedures, AddClassInstanceFlag of -1.
+# No case for GetNameFromDispID on an object of a twinBASIC class (5), which the probe module
+# cannot declare: the page states it in its prose. InternalGetReturnAddress fails a 64-bit
+# build, Emit and EmitAny write machine code, ShowPropertyPageEditor given a control shows a
+# box: none has a case.
+# Eval's row of errors raised while evaluating is bugs/expression-service-error-numbers (its
+# other -2147467259 rows are in no entry), and the crashes
+# bugs/nothing-argument-crashes.
+beta: 1010
+pages:
+  Reference/Default/VBA/HiddenModule/AddClassInstanceFlag.md:
+    rows:
+      - error: 94
+        when: "*Flag* is **Null**"
+        cases:
+          - { decl: Dim C As New Collection, run: "AddClassInstanceFlag C, Null", only: tb }
+          - { decl: Dim C As New Collection, run: "RemoveClassInstanceFlag C, Null", only: tb }
+      - error: 424
+        when: "*ClassInstance* is **Null**"
+        cases:
+          - { run: "AddClassInstanceFlag Null, 2048", only: tb }
+          - { run: "RemoveClassInstanceFlag Null, 2048", only: tb }
+    quiet:
+      - { run: "AddClassInstanceFlag Nothing, 2048", only: tb }
+      - { run: "RemoveClassInstanceFlag Nothing, 2048", only: tb }
+  Reference/Default/VBA/HiddenModule/AllocMem.md:
+    rows:
+      - error: -2147024882
+        when: "*BytesToAlloc* is 0 or less"
+        cases:
+          - { decl: Dim P As LongPtr, run: "P = AllocMem(0)\nIf P <> 0 Then FreeMem P", only: tb }
+          - { decl: Dim P As LongPtr, run: "P = AllocMem(-1)\nIf P <> 0 Then FreeMem P", only: tb }
+          - { decl: Dim P As LongPtr, run: "P = AllocMem(-2147483648#)\nIf P <> 0 Then FreeMem P", only: tb }
+      - error: -2147024882
+        when: "in a 32-bit build, there is not enough memory for the block (2,000,000,000 bytes, for one)"
+        win64: 0
+        cases:
+          - { decl: Dim P As LongPtr, run: "P = AllocMem(2000000000)\nIf P <> 0 Then FreeMem P", only: tb }
+      - error: 94
+        when: "*BytesToAlloc* is **Null**"
+        cases:
+          - { decl: Dim P As LongPtr, run: "P = AllocMem(Null)\nIf P <> 0 Then FreeMem P", only: tb }
+    quiet:
+      - { decl: Dim P As LongPtr, run: "P = AllocMem(1)\nIf P = 0 Then Err.Raise 1001\nFreeMem P", only: tb }
+      - { decl: Dim P As LongPtr, run: "P = AllocMem(16)\nIf P = 0 Then Err.Raise 1001\nFreeMem P", only: tb }
+  Reference/Default/VBA/HiddenModule/FreeMem.md:
+    rows:
+      - error: 94
+        when: "*MemPointer* is **Null**"
+        cases:
+          - { run: FreeMem Null, only: tb }
+    quiet:
+      - { run: FreeMem 0, only: tb }
+      - { decl: Dim P As LongPtr, setup: P = AllocMem(16), run: FreeMem P, only: tb }
+  Reference/Default/VBA/HiddenModule/ConvertIconToBitmap.md:
+    harness: native
+    rows:
+      - error: -2147467259
+        when: "*IconPicture* is not an icon: a bitmap, a picture with no image, or an object that is not a picture"
+        cases:
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeBitmap, False))", only: tb }
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(0, vbPicTypeNone, False))", only: tb }
+          - { expr: ConvertIconToBitmap(LoadPicture()), only: tb }
+          - { expr: ConvertIconToBitmap(New Collection), only: tb }
+      - error: 5
+        when: "*BackColor*'s high byte is other than 0, 1, 2 or &H80 (-1, for one), or it is a system colour above &H8000001E"
+        cases:
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), -1)", only: tb }
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H3000000)", only: tb }
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H8000001F)", only: tb }
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H800000FF)", only: tb }
+      - error: 13
+        when: "*BackColor* is a string that does not hold a number"
+        cases:
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), \"abc\")", only: tb }
+      - error: 94
+        when: "*BackColor* is **Null**"
+        cases:
+          - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), Null)", only: tb }
+      - error: 424
+        when: "*IconPicture* is **Null**"
+        cases:
+          - { expr: ConvertIconToBitmap(Null), only: tb }
+    quiet:
+      - { run: "If ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False)).Type <> vbPicTypeBitmap Then Err.Raise 1001", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &HFFFFFF)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H80000005)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H8000001E)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H1000000)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), &H2000000)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), \"255\")", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), Empty)", only: tb }
+      - { expr: "ConvertIconToBitmap(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False), 1.5)", only: tb }
+  Reference/Default/VBA/HiddenModule/CreateStdPictureFromHandle.md:
+    harness: native
+    rows:
+      - error: -2147467259
+        when: "*Handle* is not of the kind *Type* names: 0 for an icon, or a bitmap for an icon, a metafile or an enhanced metafile"
+        cases:
+          - { expr: "CreateStdPictureFromHandle(0, vbPicTypeIcon, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeIcon, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeMetafile, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeEMetafile, False)", only: tb }
+      - error: -2147418113
+        when: "*Type* is less than 0 or greater than 4"
+        cases:
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), -1, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), 5, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), 99, False)", only: tb }
+      - error: 94
+        when: "an argument is **Null**"
+        cases:
+          - { expr: "CreateStdPictureFromHandle(Null, vbPicTypeBitmap, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), Null, False)", only: tb }
+          - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeBitmap, Null)", only: tb }
+    quiet:
+      - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeBitmap, False)", only: tb }
+      - { expr: "CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False)", only: tb }
+      - { run: "If CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeBitmap, True).Type <> vbPicTypeBitmap Then Err.Raise 1001\nnative_Keep", only: tb }
+      - { expr: "CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeNone, False)", only: tb }
+      - { expr: "CreateStdPictureFromHandle(0, vbPicTypeNone, False)", only: tb }
+      # a bitmap handle is not checked
+      - { run: "If CreateStdPictureFromHandle(0, vbPicTypeBitmap, False).Handle <> 0 Then Err.Raise 1001", only: tb }
+      - { expr: "CreateStdPictureFromHandle(12345, vbPicTypeBitmap, False)", only: tb }
+      - { expr: "CreateStdPictureFromHandle(native_Icon(), vbPicTypeBitmap, False)", only: tb }
+  Reference/Default/VBA/HiddenModule/PictureToByteArray.md:
+    harness: native
+    rows:
+      - error: -2147467262
+        when: "*Picture* is an object that is not a picture"
+        cases:
+          - { expr: PictureToByteArray(New Collection), only: tb }
+      - error: 424
+        when: "*Picture* is **Null**"
+        cases:
+          - { expr: PictureToByteArray(Null), only: tb }
+    quiet:
+      # Nothing gives a Byte array with no bounds: UBound raises 9 (the page says so)
+      - { run: "Result = PictureToByteArray(Nothing)\nIf VarType(Result) <> vbArray + vbByte Then Err.Raise 1001", only: tb }
+      - { run: "Result = PictureToByteArray(Nothing)\nResult = UBound(Result)\nIf Err.Number = 9 Then Err.Clear", only: tb }
+      - { expr: PictureToByteArray(LoadPicture()), only: tb }
+      - { run: "Result = PictureToByteArray(CreateStdPictureFromHandle(native_Bitmap(), vbPicTypeBitmap, False))\nIf UBound(Result) < 0 Then Err.Raise 1001", only: tb }
+      - { expr: "PictureToByteArray(CreateStdPictureFromHandle(native_Icon(), vbPicTypeIcon, False))", only: tb }
+  Reference/Default/VBA/HiddenModule/CreateGUID.md:
+    quiet:
+      - { run: "Result = CreateGUID()\nIf Len(Result) <> 36 Or Mid$(Result, 9, 1) <> \"-\" Then Err.Raise 1001", only: tb }
+      - { run: "If CreateGUID() = CreateGUID() Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/Eval.md:
+    harness: expression
+    rows:
+      - error: -2147467259
+        when: "*Expression* is a zero-length string or is not an expression, or it names something the standard library does not have"
+        cases:
+          - { expr: 'Eval("")', only: tb }
+          - { expr: 'Eval(" ")', only: tb }
+          - { expr: Eval(Empty), only: tb }
+          - { expr: 'Eval("1 2")', only: tb }
+          - { expr: 'Eval("""abc")', only: tb }
+          - { expr: 'Eval("Dim x")', only: tb }
+          - { expr: 'Eval("Err.Raise 5")', only: tb }
+          - { expr: 'Eval("New Collection")', only: tb }
+          - { expr: 'Eval("Foo")', only: tb }
+          - { expr: 'Eval("Foo(1)")', only: tb }
+          - { expr: 'Eval("x = 1")', only: tb }
+          - { expr: 'Eval("Sqr()")', only: tb }
+          - { expr: 'Eval("Sqr(1, 2)")', only: tb }
+      - error: -2147467259
+        when: "evaluating *Expression* raises an error, whatever its number: division by zero, an overflow, a type mismatch, an argument a function refuses"
+        cases:
+          - { expr: 'Eval("1 / 0")', only: tb }
+          - { expr: 'Eval("1 \ 0")', only: tb }
+          - { expr: 'Eval("1 Mod 0")', only: tb }
+          - { expr: 'Eval("2 ^ 2000")', only: tb }
+          - { expr: 'Eval("CInt(40000)")', only: tb }
+          - { expr: 'Eval("CInt(""abc"")")', only: tb }
+          - { expr: 'Eval("Sqr(-1)")', only: tb }
+          - { expr: 'Eval("Mid(""abc"", 0)")', only: tb }
+          - { expr: 'Eval("Array(1, 2)(5)")', only: tb }
+      - error: -2147467259
+        when: "the value of *Expression* is an **Error** value, or *Expression* calls **Len** with **Null**"
+        cases:
+          - { expr: 'Eval("CVErr(5)")', only: tb }
+          - { expr: 'Eval("Len(Null)")', only: tb }
+      - error: 94
+        when: "*Expression* is **Null**"
+        cases:
+          - { expr: Eval(Null), only: tb }
+    quiet:
+      - { run: "If Eval(\"2 * (Sqr(4) + 1)\") <> 6 Then Err.Raise 1001", only: tb }
+      - { run: "If Eval(\"UCase(\"\"hello\"\")\") <> \"HELLO\" Then Err.Raise 1001", only: tb }
+      - { run: "If Not IsNull(Eval(\"Null + 1\")) Then Err.Raise 1001", only: tb }
+      - { run: "If Not IsNull(Eval(\"Mid(Null, 1)\")) Then Err.Raise 1001", only: tb }
+      - { run: "If Eval(\"IsError(CVErr(5))\") <> True Then Err.Raise 1001", only: tb }
+      - { expr: 'Eval("Nothing")', only: tb }
+      - { run: "If Eval(12) <> 12 Then Err.Raise 1001", only: tb }
+      # a bug: a dangling operator or parenthesis is ignored (bugs/expression-service-dangling-tokens; the page's WARNING)
+      - { run: "If Eval(\"2 +\") <> 2 Then Err.Raise 1001", only: tb }
+      - { run: "If Eval(\"2 Mod\") <> 2 Then Err.Raise 1001", only: tb }
+      - { run: "If Eval(\"(2\") <> 2 Then Err.Raise 1001", only: tb }
+      - { run: "If Eval(\"2)\") <> 2 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredMinEnumValue.md:
+    harness: native
+    quiet:
+      - { run: "If GetDeclaredMinEnumValue(Of native_Kind)() <> -3 Then Err.Raise 1001", only: tb }
+      - { expr: GetDeclaredMinEnumValue(Of VbMsgBoxResult)(), only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredMaxEnumValue.md:
+    harness: native
+    quiet:
+      - { run: "If GetDeclaredMaxEnumValue(Of native_Kind)() <> 7 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredTypeClsid.md:
+    quiet:
+      - { expr: GetDeclaredTypeClsid(Of stdole.StdPicture)(), only: tb }
+      - { expr: GetDeclaredTypeClsid(Of Collection)(), only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredTypeEventIid.md:
+    quiet:
+      - { expr: GetDeclaredTypeEventIid(Of stdole.StdPicture)(), only: tb }
+      - { expr: GetDeclaredTypeEventIid(Of Collection)(), only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredTypeIid.md:
+    quiet:
+      - { expr: GetDeclaredTypeIid(Of stdole.IPicture)(), only: tb }
+  Reference/Default/VBA/HiddenModule/GetDeclaredTypeProgId.md:
+    quiet:
+      - { expr: GetDeclaredTypeProgId(Of stdole.StdPicture)(), only: tb }
+      - { expr: GetDeclaredTypeProgId(Of Collection)(), only: tb }
+  Reference/Default/VBA/HiddenModule/GetInheritedOwner.md:
+    rows:
+      - error: 424
+        when: "*Value* is **Null**"
+        cases:
+          - { expr: GetInheritedOwner(Null), only: tb }
+  Reference/Default/VBA/HiddenModule/GetMem1.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { decl: Dim B As Byte, run: "GetMem1 Null, B", only: tb }
+    quiet:
+      - { decl: "Dim S As String\nDim B As Byte", setup: S = "A", run: "GetMem1 StrPtr(S), B\nIf B <> 65 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetMem2.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { decl: Dim I As Integer, run: "GetMem2 Null, I", only: tb }
+    quiet:
+      - { decl: "Dim S As String\nDim I As Integer", setup: S = "A", run: "GetMem2 StrPtr(S), I\nIf I <> 65 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetMem4.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { decl: Dim L As Long, run: "GetMem4 Null, L", only: tb }
+    quiet:
+      - { decl: "Dim S As String\nDim L As Long", setup: S = "AB", run: "GetMem4 StrPtr(S), L\nIf L <> &H420041 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetMem8.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { decl: Dim C As Currency, run: "GetMem8 Null, C", only: tb }
+    quiet:
+      - { decl: "Dim A As Currency\nDim C As Currency", setup: A = 1000000@, run: "GetMem8 VarPtr(A), C\nIf C <> A Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetMemPtr.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { decl: Dim P As LongPtr, run: "GetMemPtr Null, P", only: tb }
+    quiet:
+      - { decl: "Dim A As LongPtr\nDim P As LongPtr", setup: A = 12345, run: "GetMemPtr VarPtr(A), P\nIf P <> 12345 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/PutMem1.md:
+    rows:
+      - error: 94
+        when: "*Address* or *Value* is **Null**"
+        cases:
+          - { run: "PutMem1 Null, 1", only: tb }
+          - { decl: Dim P As LongPtr, setup: P = AllocMem(8), run: "PutMem1 P, Null\nFreeMem P", only: tb }
+    quiet:
+      - { decl: "Dim P As LongPtr\nDim B As Byte", setup: P = AllocMem(8), run: "PutMem1 P, 255\nGetMem1 P, B\nFreeMem P\nIf B <> 255 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/PutMem2.md:
+    rows:
+      - error: 94
+        when: "*Address* or *Value* is **Null**"
+        cases:
+          - { run: "PutMem2 Null, 1", only: tb }
+          - { decl: Dim P As LongPtr, setup: P = AllocMem(8), run: "PutMem2 P, Null\nFreeMem P", only: tb }
+    quiet:
+      - { decl: "Dim P As LongPtr\nDim I As Integer", setup: P = AllocMem(8), run: "PutMem2 P, -2\nGetMem2 P, I\nFreeMem P\nIf I <> -2 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/PutMem4.md:
+    rows:
+      - error: 94
+        when: "*Address* or *Value* is **Null**"
+        cases:
+          - { run: "PutMem4 Null, 1", only: tb }
+          - { decl: Dim P As LongPtr, setup: P = AllocMem(8), run: "PutMem4 P, Null\nFreeMem P", only: tb }
+    quiet:
+      - { decl: "Dim P As LongPtr\nDim L As Long", setup: P = AllocMem(8), run: "PutMem4 P, &HDEADBEEF\nGetMem4 P, L\nFreeMem P\nIf L <> &HDEADBEEF Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/PutMem8.md:
+    rows:
+      - error: 94
+        when: "*Address* or *Value* is **Null**"
+        cases:
+          - { run: "PutMem8 Null, 1", only: tb }
+          - { decl: Dim P As LongPtr, setup: P = AllocMem(8), run: "PutMem8 P, Null\nFreeMem P", only: tb }
+    quiet:
+      - { decl: "Dim P As LongPtr\nDim C As Currency", setup: P = AllocMem(8), run: "PutMem8 P, 1000000@\nGetMem8 P, C\nFreeMem P\nIf C <> 1000000@ Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/PutMemPtr.md:
+    rows:
+      - error: 94
+        when: "*Address* or *Value* is **Null**"
+        cases:
+          - { run: "PutMemPtr Null, 1", only: tb }
+          - { decl: Dim P As LongPtr, setup: P = AllocMem(8), run: "PutMemPtr P, Null\nFreeMem P", only: tb }
+    quiet:
+      - { decl: "Dim P As LongPtr\nDim Q As LongPtr", setup: P = AllocMem(8), run: "PutMemPtr P, 12345\nGetMemPtr P, Q\nFreeMem P\nIf Q <> 12345 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/GetNameFromDispID.md:
+    rows:
+      - error: -2147467261
+        when: "*Object* is **Nothing**"
+        cases:
+          - { expr: "GetNameFromDispID(Nothing, 0)", only: tb }
+          - { run: "ShowPropertyPageEditor \"x\", Nothing, 0", harness: dialog, only: tb }
+      - error: -2147467263
+        when: "**GetNameFromDispID** is given an object that has no type information, such as a **Collection**"
+        cases:
+          - { expr: "GetNameFromDispID(New Collection, 0)", only: tb }
+          - { expr: "GetNameFromDispID(Err, 0)", only: tb }
+          - { expr: "GetNameFromDispID(New PropertyBag, 0)", only: tb }
+      - error: -2147467262
+        when: "**GetNameFromDispID** is given an object that does not support **IDispatch**, such as a **TbExpressionService**"
+        cases:
+          - { expr: "GetNameFromDispID(New TbExpressionService, 0)", only: tb }
+          - { expr: "GetNameFromDispID(App, 0)", only: tb }
+          - { expr: "GetNameFromDispID(Screen, 0)", only: tb }
+      - error: -2147467262
+        when: "**ShowPropertyPageEditor** is given an object that has no property pages"
+        cases:
+          - { run: "ShowPropertyPageEditor \"x\", New Collection, 0", harness: dialog, only: tb }
+          - { run: "ShowPropertyPageEditor \"x\", CreateObject(\"Scripting.Dictionary\"), 0", harness: dialog, only: tb }
+      - error: -2147319765
+        when: "**GetNameFromDispID** is given an object described by a type library, such as a **Scripting.Dictionary**, and a *DispID* that is no member's"
+        cases:
+          - { expr: "GetNameFromDispID(CreateObject(\"Scripting.Dictionary\"), 999)", only: tb }
+          - { expr: "GetNameFromDispID(New StdFont, 99999)", only: tb }
+      - error: 94
+        when: "*Caption* or *DispID* is **Null**"
+        cases:
+          - { expr: "GetNameFromDispID(CreateObject(\"Scripting.Dictionary\"), Null)", only: tb }
+          - { run: "ShowPropertyPageEditor Null, CreateObject(\"Scripting.Dictionary\"), 0", harness: dialog, only: tb }
+          - { run: "ShowPropertyPageEditor \"x\", CreateObject(\"Scripting.Dictionary\"), Null", harness: dialog, only: tb }
+      - error: 424
+        when: "*Object* is **Null**"
+        cases:
+          - { expr: "GetNameFromDispID(Null, 0)", only: tb }
+          - { run: "ShowPropertyPageEditor \"x\", Null, 0", harness: dialog, only: tb }
+    quiet:
+      - { run: "If GetNameFromDispID(CreateObject(\"Scripting.Dictionary\"), 0) <> \"Item\" Then Err.Raise 1001", only: tb }
+      - { run: "If GetNameFromDispID(CreateObject(\"Scripting.Dictionary\"), 2) <> \"Count\" Then Err.Raise 1001", only: tb }
+      - { run: "If GetNameFromDispID(CreateObject(\"Scripting.Dictionary\"), -4) <> \"_NewEnum\" Then Err.Raise 1001", only: tb }
+      - { expr: "GetNameFromDispID(New StdFont, 0)", only: tb }
+  Reference/Default/VBA/HiddenModule/GetShortcutTextByEnum.md:
+    rows:
+      - error: 94
+        when: "*ShortcutEnumId* is **Null**"
+        cases:
+          - { expr: GetShortcutTextByEnum(Null), only: tb }
+    quiet:
+      - { run: "If GetShortcutTextByEnum(-1) <> \"\" Then Err.Raise 1001", only: tb }
+      - { expr: GetShortcutTextByEnum(0), only: tb }
+      - { expr: GetShortcutTextByEnum(2147483647), only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedCompareExchange32.md:
+    rows:
+      - error: 94
+        when: "*NewValue* or *OldValueCompare* is **Null**"
+        cases:
+          - { decl: Dim T As Long, expr: "InterlockedCompareExchange32(T, Null, 0)", only: tb }
+          - { decl: Dim T As Long, expr: "InterlockedCompareExchange32(T, 5, Null)", only: tb }
+    quiet:
+      - { decl: Dim T As Long, run: "Result = InterlockedCompareExchange32(T, 5, 0)\nIf T <> 5 Or Result <> 0 Then Err.Raise 1001", only: tb }
+      - { decl: Dim T As Long, setup: T = 1, run: "Result = InterlockedCompareExchange32(T, 5, 0)\nIf T <> 1 Or Result <> 1 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedCompareExchange64.md:
+    rows:
+      - error: 94
+        when: "*NewValue* or *OldValueCompare* is **Null**"
+        cases:
+          - { decl: Dim T As LongLong, expr: "InterlockedCompareExchange64(T, Null, 0)", only: tb }
+          - { decl: Dim T As LongLong, expr: "InterlockedCompareExchange64(T, 5, Null)", only: tb }
+    quiet:
+      - { decl: Dim T As LongLong, run: "Result = InterlockedCompareExchange64(T, 5, 0)\nIf T <> 5 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedCompareExchangePointer.md:
+    rows:
+      - error: 94
+        when: "*NewValue* or *OldValueCompare* is **Null**"
+        cases:
+          - { decl: Dim T As LongPtr, expr: "InterlockedCompareExchangePointer(T, Null, 0)", only: tb }
+          - { decl: Dim T As LongPtr, expr: "InterlockedCompareExchangePointer(T, 5, Null)", only: tb }
+    quiet:
+      - { decl: Dim T As LongPtr, run: "Result = InterlockedCompareExchangePointer(T, 5, 0)\nIf T <> 5 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedExchangePointer.md:
+    rows:
+      - error: 94
+        when: "*NewValue* is **Null**"
+        cases:
+          - { decl: Dim T As LongPtr, expr: "InterlockedExchangePointer(T, Null)", only: tb }
+    quiet:
+      - { decl: Dim T As LongPtr, run: "Result = InterlockedExchangePointer(T, 7)\nIf T <> 7 Or Result <> 0 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedIncrement32.md:
+    quiet:
+      - { decl: Dim T As Long, run: "Result = InterlockedIncrement32(T)\nIf T <> 1 Or Result <> 1 Then Err.Raise 1001", only: tb }
+      # no overflow: the largest Long wraps to the smallest
+      - { decl: Dim T As Long, setup: T = 2147483647, run: "Result = InterlockedIncrement32(T)\nIf T <> -2147483648# Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/InterlockedDecrement32.md:
+    quiet:
+      - { decl: Dim T As Long, run: "Result = InterlockedDecrement32(T)\nIf T <> -1 Or Result <> -1 Then Err.Raise 1001", only: tb }
+      # no overflow: the smallest Long wraps to the largest
+      - { decl: Dim T As Long, setup: T = -2147483648#, run: "Result = InterlockedDecrement32(T)\nIf T <> 2147483647 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/RegisterMessage.md:
+    harness: native
+    rows:
+      - error: 94
+        when: "*ParentHWND*, *Mode* or *MessageType* is **Null**"
+        cases:
+          - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage Null, AllDescendants, &H100, AddressOf native_Handler", only: tb }
+          - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), Null, &H100, AddressOf native_Handler", only: tb }
+          - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), AllDescendants, Null, AddressOf native_Handler", only: tb }
+    quiet:
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), AllDescendants, &H100, AddressOf native_Handler\nH.Start\nH.Stop", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), ExactWindow, &H100, AddressOf native_Handler\nH.RegisterMessage native_Window(), ExactWindow, &H100, AddressOf native_Handler\nH.Start\nH.Stop", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.Start\nH.RegisterMessage native_Window(), DirectChildren, &H100, AddressOf native_Handler\nH.Stop", only: tb }
+      # nothing is checked when a subscription is registered
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage 0, AllDescendants, &H100, AddressOf native_Handler", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage 12345, AllDescendants, &H100, AddressOf native_Handler", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), 0, &H100, AddressOf native_Handler", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), 8, &H100, AddressOf native_Handler", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), -1, &H100, AddressOf native_Handler", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.RegisterMessage native_Window(), AllDescendants, -1, AddressOf native_Handler", only: tb }
+  Reference/Default/VBA/HiddenModule/Start.md:
+    harness: native
+    quiet:
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: "H.Start\nH.Stop", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: "Set H = RuntimeCreateGetMessageHook()\nH.RegisterMessage native_Window(), AllDescendants, &H100, AddressOf native_Handler", run: "H.Start\nH.Start\nH.Stop", only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: "Set H = RuntimeCreateGetMessageHook()\nH.RegisterMessage native_Window(), ExactWindow, &H100, AddressOf native_Handler", run: "H.Start\nnative_End\nH.Stop", only: tb }
+  Reference/Default/VBA/HiddenModule/Stop.md:
+    harness: native
+    quiet:
+      - { decl: Dim H As IGetMessageHook, setup: Set H = RuntimeCreateGetMessageHook(), run: H.Stop, only: tb }
+      - { decl: Dim H As IGetMessageHook, setup: "Set H = RuntimeCreateGetMessageHook()\nH.RegisterMessage native_Window(), AllDescendants, &H100, AddressOf native_Handler", run: "H.Stop\nH.Start\nH.Stop\nH.Stop\nH.Start\nH.Stop", only: tb }
+  Reference/Default/VBA/HiddenModule/RuntimeCreateGetMessageHook.md:
+    quiet:
+      - { decl: Dim H As IGetMessageHook, run: "Set H = RuntimeCreateGetMessageHook()\nIf H Is Nothing Then Err.Raise 1001", only: tb }
+      - { decl: Dim V As Variant, run: "Set V = RuntimeCreateGetMessageHook()", only: tb }
+      - { run: RuntimeCreateGetMessageHook, only: tb }
+  Reference/Default/VBA/HiddenModule/SetThreadGlobalErrorTrap.md:
+    rows:
+      - error: 94
+        when: "*CallbackAddress* is **Null**"
+        cases:
+          - { run: SetThreadGlobalErrorTrap Null, only: tb }
+    quiet:
+      - { run: SetThreadGlobalErrorTrap 0, only: tb }
+  Reference/Default/VBA/HiddenModule/StackArgsSize.md:
+    quiet:
+      - { expr: StackArgsSize(), only: tb }
+  Reference/Default/VBA/HiddenModule/StackOffset.md:
+    quiet:
+      - { expr: StackOffset(Result), only: tb }
+  Reference/Default/VBA/HiddenModule/UnprotectedAccess.md:
+    quiet:
+      - { decl: "Dim C As New Collection\nDim O As Object", run: "Set O = UnprotectedAccess(C)\nIf O.Count <> 0 Then Err.Raise 1001", only: tb }
+      - { decl: "Dim C As Collection\nDim O As Object", run: "Set O = UnprotectedAccess(C)", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaAryMove.md:
+    quiet:
+      - { decl: "Dim A() As Long\nDim B() As Long", setup: ReDim B(3), run: "vbaAryMove A, B\nIf UBound(A) <> 3 Then Err.Raise 1001\nResult = UBound(B)\nIf Err.Number = 9 Then Err.Clear Else Err.Raise 1001", only: tb }
+      - { decl: "Dim A() As Long\nDim B() As Long", setup: ReDim A(3), run: "vbaAryMove A, B\nResult = UBound(A)\nIf Err.Number = 9 Then Err.Clear Else Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaCastObj.md:
+    harness: native
+    rows:
+      - error: 424
+        when: "*Obj* is **Null**"
+        cases:
+          - { expr: "vbaCastObj(Null, native_StdIid(0))", only: tb }
+      # VB6's own __vbaCastObj (msvbvm60) raises 13 for both; twinBASIC returns Nothing
+      - error: 0
+        when: "*Obj* does not have the interface *IID* names, or *IID* is a **String**, whose text is not read as an interface ID"
+        vb6: 13
+        bug: vbacastobj-no-type-mismatch
+        cases:
+          - { run: "If Not vbaCastObj(New Collection, native_StdIid(&H12345)) Is Nothing Then Err.Raise 1001", only: tb }
+          - { run: 'If Not vbaCastObj(New Collection, "{00000000-0000-0000-C000-000000000046}") Is Nothing Then Err.Raise 1001', only: tb }
+          - { run: 'If Not vbaCastObj(New Collection, "abc") Is Nothing Then Err.Raise 1001', only: tb }
+    quiet:
+      - { run: "If vbaCastObj(New Collection, native_StdIid(0)) Is Nothing Then Err.Raise 1001", only: tb }
+      - { run: "If vbaCastObj(New Collection, native_StdIid(&H20400)) Is Nothing Then Err.Raise 1001", only: tb }
+      - { run: "If Not vbaCastObj(Nothing, native_StdIid(0)) Is Nothing Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaCopyBytes.md:
+    rows:
+      - error: 94
+        when: "an argument is **Null**"
+        cases:
+          - { expr: "vbaCopyBytes(Null, 0, 0)", only: tb }
+          - { expr: "vbaCopyBytes(0, Null, 0)", only: tb }
+          - { expr: "vbaCopyBytes(0, 0, Null)", only: tb }
+    quiet:
+      - { expr: "vbaCopyBytes(0, 0, 0)", only: tb }
+      - { decl: "Dim P As LongPtr\nDim L As Long", setup: "P = AllocMem(8)\nPutMem4 P + 4, 77", run: "Result = vbaCopyBytes(4, P, P + 4)\nGetMem4 P, L\nFreeMem P\nIf L <> 77 Or Result <> P Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaCopyBytesZero.md:
+    rows:
+      - error: 94
+        when: "an argument is **Null**"
+        cases:
+          - { expr: "vbaCopyBytesZero(Null, 0, 0)", only: tb }
+          - { expr: "vbaCopyBytesZero(0, Null, 0)", only: tb }
+          - { expr: "vbaCopyBytesZero(0, 0, Null)", only: tb }
+    quiet:
+      - { expr: "vbaCopyBytesZero(0, 0, 0)", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaObjAddref.md:
+    rows:
+      - error: 94
+        when: "*Address* is **Null**"
+        cases:
+          - { run: vbaObjAddref Null, only: tb }
+    quiet:
+      - { run: vbaObjAddref 0, only: tb }
+  Reference/Default/VBA/HiddenModule/vbaObjSet.md:
+    rows:
+      - error: 94
+        when: "*SrcObjPtr* is **Null**"
+        cases:
+          - { decl: Dim O As IUnknown, expr: "vbaObjSet(O, Null)", only: tb }
+    quiet:
+      - { decl: Dim O As IUnknown, run: "Result = vbaObjSet(O, 0)\nIf Not O Is Nothing Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaObjSetAddref.md:
+    rows:
+      - error: 94
+        when: "*SrcObjPtr* is **Null**"
+        cases:
+          - { decl: Dim O As IUnknown, expr: "vbaObjSetAddref(O, Null)", only: tb }
+    quiet:
+      - { decl: Dim O As IUnknown, run: "Result = vbaObjSetAddref(O, 0)\nIf Not O Is Nothing Then Err.Raise 1001", only: tb }
+      - { decl: "Dim O As IUnknown\nDim C As New Collection", run: "Result = vbaObjSetAddref(O, ObjPtr(C))\nIf Not O Is C Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/HiddenModule/vbaRefVarAry.md:
+    quiet:
+      - { decl: "Dim V As Variant\nDim P As LongPtr", setup: "V = Array(1, 2)", run: "GetMemPtr vbaRefVarAry(V), P\nIf P = 0 Then Err.Raise 1001", only: tb }
+      # a Variant that holds no array raises nothing
+      - { decl: Dim V As Variant, setup: V = 5, expr: vbaRefVarAry(V), only: tb }
+      - { decl: Dim V As Variant, expr: vbaRefVarAry(V), only: tb }
+      - { decl: Dim V As Variant, setup: V = Null, expr: vbaRefVarAry(V), only: tb }
diff --git a/errors/VBA.TbExpressionService.yml b/errors/VBA.TbExpressionService.yml
new file mode 100644
index 000000000..87b48f1c4
--- /dev/null
+++ b/errors/VBA.TbExpressionService.yml
@@ -0,0 +1,119 @@
+# The VBA TbExpressionService class, with ITbExpression. Format: WIP.Errors.md.
+# Every case is `only: tb`: VB6 and VBA have none of these. Every page runs under the
+# expression harness, which spends the first error of the process (WIP.Errors.md).
+# Evaluate's -2147467259 rows are bugs/expression-service-error-numbers: when it is fixed, an
+# error raised while evaluating reaches the caller unchanged. Compile's rows and the harness are
+# in no entry (the owner: the entry asks only for errors to pass through unchanged).
+# No case for AddCustomBinder or Bind, which need a class implementing ITbCustomBinder that
+# the probe module cannot declare, nor for AddCustomBinder Nothing and AddCustomBinderObject
+# with an object of Nothing, which crash (an access violation, 32-bit and 64-bit; the pages'
+# WARNINGs).
+beta: 1010
+pages:
+  Reference/Default/VBA/TbExpressionService/Compile.md:
+    harness: expression
+    rows:
+      - error: -2147467259
+        when: "*expression* is a zero-length string or is not an expression"
+        cases:
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("1 2")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("1 + * 2")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile(")")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("Sqr(4")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("""abc")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("Err.Raise 5")', only: tb }
+      - error: -2147467259
+        when: "*expression* names something that no registered binder resolves (any name, when no binder is registered), or calls a function with the wrong number of arguments"
+        cases:
+          - { decl: Dim S As New TbExpressionService, expr: 'S.Compile("Sqr(2)")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("Foo")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("D.Count")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: 'S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary")', expr: 'S.Compile("Count")', only: tb }
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("Sqr(1, 2)")', only: tb }
+      - error: 94
+        when: "*expression* is **Null**"
+        cases:
+          - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: S.Compile(Null), only: tb }
+    quiet:
+      - { decl: Dim S As New TbExpressionService, run: "If S.Compile(\"1 + 1\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
+      # an error in evaluating is raised by Evaluate, not by Compile
+      - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("1 / 0")', only: tb }
+      - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, expr: 'S.Compile("CInt(""abc"")")', only: tb }
+      # a bug: a dangling operator or parenthesis is ignored (bugs/expression-service-dangling-tokens; the page's WARNING)
+      - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, run: "If S.Compile(\"2 +\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, run: "If S.Compile(\"(2\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim S As New TbExpressionService, setup: S.AddStdLibraryBinder, run: "If S.Compile(\"2)\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
+  Reference/Default/VBA/TbExpressionService/Evaluate.md:
+    harness: expression
+    rows:
+      - error: -2147467259
+        when: "evaluating the expression raises an error, whatever its number: division by zero, a type mismatch, an argument a function refuses"
+        cases:
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression"
+            setup: "S.AddStdLibraryBinder\nSet E = S.Compile(\"1 / 0\")"
+            expr: E.Evaluate()
+            only: tb
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression"
+            setup: "S.AddStdLibraryBinder\nSet E = S.Compile(\"CInt(\"\"abc\"\")\")"
+            expr: E.Evaluate()
+            only: tb
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression"
+            setup: "S.AddStdLibraryBinder\nSet E = S.Compile(\"Sqr(-1)\")"
+            expr: E.Evaluate()
+            only: tb
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression"
+            setup: "S.AddStdLibraryBinder\nSet E = S.Compile(\"Mid(\"\"abc\"\", 0)\")"
+            expr: E.Evaluate()
+            only: tb
+      - error: -2147467259
+        when: "the expression calls a member of a bound object that the object does not have, or with the wrong number of arguments"
+        cases:
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression\nDim D As Object"
+            setup: "Set D = CreateObject(\"Scripting.Dictionary\")\nS.AddCustomBinderObject \"D\", D\nSet E = S.Compile(\"D.Nope\")"
+            expr: E.Evaluate()
+            only: tb
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression\nDim D As Object"
+            setup: "Set D = CreateObject(\"Scripting.Dictionary\")\nS.AddCustomBinderObject \"D\", D\nSet E = S.Compile(\"D.Item(1, 2)\")"
+            expr: E.Evaluate()
+            only: tb
+      - error: -2147467259
+        when: "a member of a bound object that the expression calls raises an error, whatever its number"
+        message: Automation error
+        cases:
+          - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression\nDim D As Object"
+            setup: "Set D = CreateObject(\"Scripting.Dictionary\")\nD.Add 1, 1\nS.AddCustomBinderObject \"D\", D\nSet E = S.Compile(\"D.Add(1, 2)\")"
+            expr: E.Evaluate()
+            only: tb
+    quiet:
+      - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression\nDim D As Object"
+        setup: "Set D = CreateObject(\"Scripting.Dictionary\")\nS.AddCustomBinderObject \"D\", D\nSet E = S.Compile(\"D.Count\")"
+        run: "If E.Evaluate() <> 0 Then Err.Raise 1001\nD.Add 1, 1\nIf E.Evaluate() <> 1 Then Err.Raise 1001"
+        only: tb
+      # the compiled expression keeps the service and the bound object alive
+      - decl: "Dim S As New TbExpressionService\nDim E As ITbExpression\nDim D As Object"
+        setup: "Set D = CreateObject(\"Scripting.Dictionary\")\nS.AddCustomBinderObject \"D\", D\nSet E = S.Compile(\"D.Count\")\nSet D = Nothing\nSet S = Nothing"
+        expr: E.Evaluate()
+        only: tb
+  Reference/Default/VBA/TbExpressionService/AddCustomBinderObject.md:
+    harness: expression
+    rows:
+      - error: 94
+        when: "*name* or *flags* is **Null**"
+        cases:
+          - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject Null, CreateObject("Scripting.Dictionary")', only: tb }
+          - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary"), Null', only: tb }
+    quiet:
+      - { decl: Dim S As New TbExpressionService, run: "S.AddCustomBinderObject \"D\", CreateObject(\"Scripting.Dictionary\"), IsAppObject\nIf S.Compile(\"Count\").Evaluate() <> 0 Then Err.Raise 1001", only: tb }
+      - { decl: Dim S As New TbExpressionService, run: "S.AddCustomBinderObject \"C\", New Collection\nIf S.Compile(\"C.Count\").Evaluate() <> 0 Then Err.Raise 1001", only: tb }
+      # neither the name nor the flags are checked, and a name may be given twice
+      - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject "", CreateObject("Scripting.Dictionary")', only: tb }
+      - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject "1x", CreateObject("Scripting.Dictionary")', only: tb }
+      - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary"), 2', only: tb }
+      - { decl: Dim S As New TbExpressionService, run: 'S.AddCustomBinderObject "D", CreateObject("Scripting.Dictionary"), -1', only: tb }
+      - { decl: Dim S As New TbExpressionService, run: "S.AddCustomBinderObject \"D\", CreateObject(\"Scripting.Dictionary\")\nS.AddCustomBinderObject \"D\", New Collection\nResult = S.Compile(\"D.Count\").Evaluate()", only: tb }
+  Reference/Default/VBA/TbExpressionService/AddStdLibraryBinder.md:
+    harness: expression
+    quiet:
+      - { decl: Dim S As New TbExpressionService, run: "S.AddStdLibraryBinder\nIf S.Compile(\"Sqr(4)\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
+      - { decl: Dim S As New TbExpressionService, run: "S.AddStdLibraryBinder\nS.AddStdLibraryBinder\nIf S.Compile(\"Sqr(4)\").Evaluate() <> 2 Then Err.Raise 1001", only: tb }
diff --git a/errors/harnesses/expression.bas b/errors/harnesses/expression.bas
new file mode 100644
index 000000000..f2fc14d9c
--- /dev/null
+++ b/errors/harnesses/expression.bas
@@ -0,0 +1,19 @@
+' The expression harness, for twinBASIC only: every case that uses it is `only: tb`, since VB6
+' and VBA have no Eval and no TbExpressionService.
+' In a built exe the first error the expression service raises in a process has the
+' description "Automation error", and every later one "Unspecified error" (BETA 1010; the
+' pages' NOTEs). expression_Begin raises that first one once, and clears it, so that what a
+' case reports does not depend on which case runs first.
+
+Private Sub expression_Begin()
+    Static Done As Boolean
+    If Done Then Exit Sub
+    Done = True
+    Dim V As Variant
+    On Error Resume Next
+    V = Eval("1 2")
+    Err.Clear
+End Sub
+
+Private Sub expression_End()
+End Sub
diff --git a/errors/harnesses/files.bas b/errors/harnesses/files.bas
new file mode 100644
index 000000000..cd4f4ce4e
--- /dev/null
+++ b/errors/harnesses/files.bas
@@ -0,0 +1,164 @@
+' The files harness, for twinBASIC, VB6 and VBA alike: every case that touches the file system
+' runs in a folder of its own. files_Begin makes the folder files_Dir, tbdocsErrorsProbe and the
+' process id under the temporary folder (the four runtimes run at once), fills it with the
+' fixtures below and makes it the current directory, so that a case names its files relatively
+' ("a.txt"). files_End closes every file the case left open, puts the current directory back,
+' and deletes the folder with everything in it, read-only, hidden and system files included.
+' The error the case raised is kept: files_End raises it again, with its description.
+'
+' The fixtures: a.txt (abc, CR LF, def, CR LF: 10 bytes), empty.txt (0 bytes), ro.txt (x,
+' read-only), hid.txt (x, hidden), the empty folder sub, and the folder full holding f.txt (x).
+'
+' files_Begin raises 1003 when it cannot make the folder or make it current, and the case is
+' then skipped (its setup failed), so that no case runs with a relative name in another folder.
+' The folder and the files are made with Windows' own calls, never with a statement under test,
+' except the fixtures' contents, written with Open and Print #. Nothing is deleted outside
+' files_Dir: files_Clear refuses a path that does not end in the folder's own name.
+'
+' files_Attr(name) is GetFileAttributesW of a name, -1 when it does not exist;
+' files_Expect Cond raises 1001 when Cond is False and the case has raised nothing;
+' files_NoDrive is a drive letter no drive has. VBA7 is true in twinBASIC and in VBA 7; VB6
+' compiles only the #Else branch.
+
+#If VBA7 Then
+Private Declare PtrSafe Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare PtrSafe Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As LongPtr) As Long
+Private Declare PtrSafe Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As LongPtr, ByVal Security As LongPtr) As Long
+Private Declare PtrSafe Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As LongPtr) As Long
+Private Declare PtrSafe Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As LongPtr, ByVal Attributes As Long) As Long
+Private Declare PtrSafe Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As LongPtr, ByVal Data As LongPtr) As LongPtr
+Private Declare PtrSafe Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As LongPtr, ByVal Data As LongPtr) As Long
+Private Declare PtrSafe Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As LongPtr) As Long
+Private Declare PtrSafe Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare PtrSafe Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
+#Else
+Private Declare Function files_GetCurrentProcessId Lib "kernel32" Alias "GetCurrentProcessId" () As Long
+Private Declare Function files_GetTempPath Lib "kernel32" Alias "GetTempPathW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectoryW" (ByVal Size As Long, ByVal Buffer As Long) As Long
+Private Declare Function files_SetCurrentDirectory Lib "kernel32" Alias "SetCurrentDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_CreateDirectory Lib "kernel32" Alias "CreateDirectoryW" (ByVal Path As Long, ByVal Security As Long) As Long
+Private Declare Function files_RemoveDirectory Lib "kernel32" Alias "RemoveDirectoryW" (ByVal Path As Long) As Long
+Private Declare Function files_DeleteFile Lib "kernel32" Alias "DeleteFileW" (ByVal Path As Long) As Long
+Private Declare Function files_GetFileAttributes Lib "kernel32" Alias "GetFileAttributesW" (ByVal Path As Long) As Long
+Private Declare Function files_SetFileAttributes Lib "kernel32" Alias "SetFileAttributesW" (ByVal Path As Long, ByVal Attributes As Long) As Long
+Private Declare Function files_FindFirstFile Lib "kernel32" Alias "FindFirstFileW" (ByVal Pattern As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindNextFile Lib "kernel32" Alias "FindNextFileW" (ByVal Find As Long, ByVal Data As Long) As Long
+Private Declare Function files_FindClose Lib "kernel32" Alias "FindClose" (ByVal Find As Long) As Long
+Private Declare Function files_GetLogicalDrives Lib "kernel32" Alias "GetLogicalDrives" () As Long
+Private Declare Sub files_CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Dest As Long, ByVal Source As Long, ByVal Length As Long)
+#End If
+
+' The current directory before the case, put back by files_End.
+Private files_Saved As String
+
+Private Function files_Name() As String
+    files_Name = "tbdocsErrorsProbe" & files_GetCurrentProcessId()
+End Function
+
+' The case's folder: the temporary folder's path, with no backslash at its end.
+Private Function files_Dir() As String
+    Dim B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetTempPath(1024, StrPtr(B))
+    B = Left$(B, N)
+    If Right$(B, 1) = "\" Then B = Left$(B, Len(B) - 1)
+    files_Dir = B & "\" & files_Name()
+End Function
+
+Private Function files_Attr(ByVal Path As String) As Long
+    files_Attr = files_GetFileAttributes(StrPtr(Path))
+End Function
+
+Private Sub files_Expect(ByVal Cond As Boolean)
+    If Err.Number <> 0 Then Exit Sub
+    If Not Cond Then Err.Raise 1001, , "files_Expect: not as expected"
+End Sub
+
+' A drive letter that no drive has, from Z down.
+Private Function files_NoDrive() As String
+    Dim Mask As Long, I As Long
+    Mask = files_GetLogicalDrives()
+    For I = 25 To 3 Step -1
+        If (Mask And (2 ^ I)) = 0 Then files_NoDrive = Chr$(65 + I): Exit Function
+    Next
+End Function
+
+' Deletes Path and everything in it, whatever their attributes.
+Private Sub files_DeleteTree(ByVal Path As String)
+    Dim Data(0 To 599) As Byte, Pattern As String, Nm As String, Attr As Long, N As Long
+    Dim H As Variant, Names() As String, Dirs() As Boolean, Count As Long, I As Long
+    ReDim Names(0 To 15): ReDim Dirs(0 To 15)
+    Pattern = Path & "\*"
+    H = files_FindFirstFile(StrPtr(Pattern), VarPtr(Data(0)))
+    If H <> -1 Then
+        Do
+            Nm = String$(260, vbNullChar)
+            files_CopyMemory StrPtr(Nm), VarPtr(Data(44)), 520
+            N = InStr(Nm, vbNullChar)
+            If N > 0 Then Nm = Left$(Nm, N - 1)
+            files_CopyMemory VarPtr(Attr), VarPtr(Data(0)), 4
+            If Nm <> "." And Nm <> ".." Then
+                If Count > UBound(Names) Then ReDim Preserve Names(0 To Count * 2): ReDim Preserve Dirs(0 To Count * 2)
+                Names(Count) = Nm
+                Dirs(Count) = (Attr And 16) <> 0 And (Attr And &H400) = 0
+                Count = Count + 1
+            End If
+        Loop While files_FindNextFile(H, VarPtr(Data(0))) <> 0
+        files_FindClose H
+    End If
+    For I = 0 To Count - 1
+        Nm = Path & "\" & Names(I)
+        files_SetFileAttributes StrPtr(Nm), 128
+        If Dirs(I) Then files_DeleteTree Nm Else files_DeleteFile StrPtr(Nm)
+    Next
+    files_SetFileAttributes StrPtr(Path), 128
+    files_RemoveDirectory StrPtr(Path)
+End Sub
+
+' Closes every file, puts the current directory back and deletes the folder.
+Private Sub files_Clear()
+    Dim D As String
+    Close
+    If Len(files_Saved) Then files_SetCurrentDirectory StrPtr(files_Saved)
+    D = files_Dir()
+    If Right$(D, Len(files_Name()) + 1) <> "\" & files_Name() Then Exit Sub
+    If files_Attr(D) <> -1 Then files_DeleteTree D
+End Sub
+
+Private Sub files_Make(ByVal Path As String, ByVal Contents As String, ByVal Attr As Long)
+    Dim F As Integer
+    F = FreeFile
+    Open Path For Output As #F
+    Print #F, Contents;
+    Close #F
+    If Attr <> 0 Then files_SetFileAttributes StrPtr(Path), Attr
+End Sub
+
+Private Sub files_Begin()
+    Dim D As String, B As String, N As Long
+    B = String$(1024, vbNullChar)
+    N = files_GetCurrentDirectory(1024, StrPtr(B))
+    files_Saved = Left$(B, N)
+    files_Clear
+    D = files_Dir()
+    If files_CreateDirectory(StrPtr(D), 0) = 0 Then Err.Raise 1003, , "files_Begin: cannot make " & D: Exit Sub
+    If files_SetCurrentDirectory(StrPtr(D)) = 0 Then Err.Raise 1003, , "files_Begin: cannot enter " & D: Exit Sub
+    files_Make D & "\a.txt", "abc" & vbCrLf & "def" & vbCrLf, 0
+    files_Make D & "\empty.txt", "", 0
+    files_Make D & "\ro.txt", "x", 1
+    files_Make D & "\hid.txt", "x", 2
+    files_CreateDirectory StrPtr(D & "\sub"), 0
+    files_CreateDirectory StrPtr(D & "\full"), 0
+    files_Make D & "\full\f.txt", "x", 0
+End Sub
+
+Private Sub files_End()
+    Dim N As Long, D As String
+    N = Err.Number: D = Err.Description
+    files_Clear
+    If N <> 0 Then Err.Raise N, , D
+End Sub
diff --git a/errors/harnesses/native.bas b/errors/harnesses/native.bas
new file mode 100644
index 000000000..36bb9bb93
--- /dev/null
+++ b/errors/harnesses/native.bas
@@ -0,0 +1,79 @@
+' The native harness, for twinBASIC only: the procedures of the (Default) module that take a
+' GDI handle, a window or a callback get them from here. Every case that uses it is
+' `only: tb`, since VB6 and VBA have none of those procedures, so this file may use
+' twinBASIC's own syntax (GetMessageHookHelper).
+' native_Begin creates a hidden STATIC window of the probe's own thread, native_Window, and
+' native_End destroys it and every bitmap native_Bitmap made that a case did not give away.
+' native_Icon is the shared IDI_APPLICATION icon, which is never destroyed.
+' native_Handler is a GetMessageHookHelper.GetMessageHandler that does nothing.
+' native_StdIid is the address of a standard COM interface ID.
+
+Private Declare PtrSafe Function native_CreateWindowExA Lib "user32" Alias "CreateWindowExA" (ByVal Ex As Long, ByVal Cls As String, ByVal Title As String, ByVal Style As Long, ByVal X As Long, ByVal Y As Long, ByVal W As Long, ByVal H As Long, ByVal Parent As LongPtr, ByVal Menu As LongPtr, ByVal Inst As LongPtr, ByVal P As LongPtr) As LongPtr
+Private Declare PtrSafe Function native_DestroyWindow Lib "user32" Alias "DestroyWindow" (ByVal H As LongPtr) As Long
+Private Declare PtrSafe Function native_LoadIconW Lib "user32" Alias "LoadIconW" (ByVal Inst As LongPtr, ByVal Name As LongPtr) As LongPtr
+Private Declare PtrSafe Function native_CreateBitmap Lib "gdi32" Alias "CreateBitmap" (ByVal W As Long, ByVal H As Long, ByVal Planes As Long, ByVal Bits As Long, ByVal Data As LongPtr) As LongPtr
+Private Declare PtrSafe Function native_DeleteObject Lib "gdi32" Alias "DeleteObject" (ByVal H As LongPtr) As Long
+
+' An enumeration for GetDeclaredMinEnumValue and GetDeclaredMaxEnumValue.
+Private Enum native_Kind
+    native_Low = -3
+    native_Mid = 0
+    native_High = 7
+End Enum
+
+Private Type native_GUID
+    Data1 As Long
+    Data2 As Integer
+    Data3 As Integer
+    Data4(0 To 7) As Byte
+End Type
+
+Private native_Hwnd As LongPtr
+Private native_Bitmaps As New Collection
+Private native_Iid As native_GUID
+
+' The address of the interface ID {Data1-0000-0000-C000-000000000046}, for vbaCastObj:
+' 0 is IUnknown's, &H20400 IDispatch's.
+Private Function native_StdIid(ByVal Data1 As Long) As LongPtr
+    native_Iid.Data1 = Data1
+    native_Iid.Data4(0) = &HC0
+    native_Iid.Data4(7) = &H46
+    native_StdIid = VarPtr(native_Iid)
+End Function
+
+Private Function native_Window() As LongPtr
+    native_Window = native_Hwnd
+End Function
+
+Private Function native_Icon() As LongPtr
+    native_Icon = native_LoadIconW(0, 32512)
+End Function
+
+' A 2 x 2 bitmap, deleted by native_End unless native_Keep says a picture owns it.
+Private Function native_Bitmap() As LongPtr
+    native_Bitmap = native_CreateBitmap(2, 2, 1, 32, 0)
+    native_Bitmaps.Add native_Bitmap
+End Function
+
+' The last bitmap made belongs to a picture now (TakeOwnership True): native_End leaves it.
+Private Sub native_Keep()
+    native_Bitmaps.Remove native_Bitmaps.Count
+End Sub
+
+Private Function native_Handler(ByRef Msg As GetMessageHookHelper.HookMSG) As LongPtr
+    native_Handler = 0
+End Function
+
+Private Sub native_Begin()
+    native_Hwnd = native_CreateWindowExA(0, "STATIC", "tbdocsErrorsProbe", 0, 0, 0, 100, 100, 0, 0, 0, 0)
+End Sub
+
+Private Sub native_End()
+    Dim H As Variant
+    For Each H In native_Bitmaps
+        native_DeleteObject H
+    Next
+    Set native_Bitmaps = New Collection
+    If native_Hwnd <> 0 Then native_DestroyWindow native_Hwnd
+    native_Hwnd = 0
+End Sub
diff --git a/errors/messages.yml b/errors/messages.yml
index 74872955e..4b7925142 100644
--- a/errors/messages.yml
+++ b/errors/messages.yml
@@ -101,6 +101,9 @@
 -2147467262:
   raised: No such interface supported
   error: Application-defined or object-defined error
+-2147418113:
+  raised: Catastrophic failure
+  error: Application-defined or object-defined error
 -2147352567:
   raised: Exception occurred.
   error: Application-defined or object-defined error
@@ -128,3 +131,15 @@
 -2147023174:
   raised: The RPC server is unavailable.
   error: Application-defined or object-defined error
+-2147024882:
+  raised: Not enough memory resources are available to complete this operation.
+  error: Application-defined or object-defined error
+-2147467263:
+  raised: Not implemented
+  error: Application-defined or object-defined error
+-2147467261:
+  raised: Invalid pointer
+  error: Application-defined or object-defined error
+-2147319765:
+  raised: Element not found.
+  error: Application-defined or object-defined error
diff --git a/scripts/check_impexp_parity.mjs b/scripts/check_impexp_parity.mjs
index aef4dfa10..f1a7c3196 100644
--- a/scripts/check_impexp_parity.mjs
+++ b/scripts/check_impexp_parity.mjs
@@ -157,8 +157,24 @@ const COMMANDS = [
   { args: ["export", "sample", "sample.twinpack"], exit: 2, why: "the arguments in the wrong order" },
   { args: ["bogus", "sample.twinpack"], exit: 2, why: "an unknown command" },
   { args: ["export", "sample.twinpack", "sample", "--bogus"], exit: 2, why: "an unknown option" },
+  {
+    args: ["export", "sample.twinpack", 'out x" --overwrite'],
+    exit: 2,
+    program: true,
+    why: 'what Windows makes of "out x\\" --overwrite',
+  },
+  { args: ['export"'], exit: 2, why: "a double quote, and no command to suggest" },
 ];
 
+// The line after "The command meant is:" starts with the program, which each
+// edition names as it was run; `program` compares the rest of the line.
+function withoutProgram(stderr) {
+  return stderr.replace(
+    /(The command meant is:\n {9}).*? (export|import|settings|licence|changelog|readme)(?= |$)/m,
+    "$1<program> $2",
+  );
+}
+
 // The first Python 3.6+ on PATH, as [command, ...args, version], or null.
 function findPython() {
   const candidates = [["python3"], ["python"]];
@@ -349,6 +365,13 @@ try {
     const label = `impexp ${c.args.join(" ")}${c.why ? ` (${c.why})` : ""}`;
     for (const dir of dirs) c.setup?.(dir);
     const results = await Promise.all(editions.map((e, i) => run(e, c.args, dirs[i])));
+    if (c.program) {
+      for (const r of results) {
+        const normal = withoutProgram(r.stderr);
+        if (normal === r.stderr) problems.push(`${label}: no command to copy in ${JSON.stringify(r.stderr)}`);
+        r.stderr = normal;
+      }
+    }
     if (results.some((r) => r.status !== c.exit)) {
       const codes = editions.map((e, i) => `${results[i].status} from ${e.name}`);
       problems.push(`${label}: exit ${codes.join(", ")}, not ${c.exit}`);
diff --git a/scripts/check_symbol_index.mjs b/scripts/check_symbol_index.mjs
index 838c95539..ee73bf541 100644
--- a/scripts/check_symbol_index.mjs
+++ b/scripts/check_symbol_index.mjs
@@ -29,7 +29,7 @@
 import { readFile } from "node:fs/promises";
 import { GUARDED_SRC } from "../builder/baseline.mjs";
 import { checkSymbolBaseline } from "../builder/symbol-baseline.mjs";
-import { deriveSymbolIndex, headingsOf, serializeSymbolIndex } from "../builder/symbols.mjs";
+import { deriveSymbolIndex, headingsOf, serializeSymbolIndex, symbolPages } from "../builder/symbols.mjs";
 import { exitOnCrash, parseCli, printHelpAndExit, withUsageError } from "../lib/cli.mjs";
 import { baselineFixture, createProbes } from "./lib/gate-probes.mjs";
 import { apiSnapshot, isPublicType, logicalLinesRaw, parseSources, parseTwin, projectNameOf } from "./lib/twin-api.mjs";
@@ -1842,6 +1842,10 @@ const pages = [
     [h(1, "Data Types", "data-types"), h(2, "Quick reference", "quick-reference"), h(2, "Long", "long"),
       h(2, "Overflow", "overflow"), h(2, "String", "string"), h(3, "Fixed-length strings", "fixed-length-strings")],
     { symbols: ["Long", "String"] }),
+  page("Reference/Literal-Keywords.md", "/Reference/Literal-Keywords", "Literal Keywords", "Reference Section",
+    [h(1, "Nothing, Null, Empty, True and False", "nothing-null-empty-true-and-false"), h(2, "Nothing", "nothing"),
+      h(2, "Null", "null"), h(3, "Null in expressions", "null-in-expressions")],
+    { symbols: ["Nothing", "Null"] }),
 ];
 
 const r = deriveSymbolIndex({ pages, api });
@@ -1940,10 +1944,64 @@ check(
   show(r.interfaces),
 );
 check(
-  "only /tB/ pages and the data types page are read",
-  !r.symbols.some((s) => !s.url.startsWith("/tB/") && !s.url.startsWith("/Reference/Data-Types#")) &&
-    !find("Guide").length,
+  "only /tB/ pages and the two summary pages are read",
+  !r.symbols.some(
+    (s) =>
+      !s.url.startsWith("/tB/") &&
+      !s.url.startsWith("/Reference/Data-Types#") &&
+      !s.url.startsWith("/Reference/Literal-Keywords#"),
+  ) && !find("Guide").length,
 );
+check(
+  "a literal keyword is the language's, a keyword at the ## heading its symbols: entry names",
+  show(find("Nothing")) ===
+    show([
+      { name: "Nothing", package: null, container: null, kind: "keyword", url: "/Reference/Literal-Keywords#nothing" },
+    ]) &&
+    urlOf("Null").join() === "/Reference/Literal-Keywords#null" &&
+    !find("Literal").length,
+  show(r.symbols.filter((s) => s.url.startsWith("/Reference/Literal-Keywords"))),
+);
+{
+  const broken = pages.map((p) =>
+    p.src === "Reference/Literal-Keywords.md" ? { ...p, symbols: ["Nothing", "Empty"] } : p,
+  );
+  let error = null;
+  try {
+    deriveSymbolIndex({ pages: broken, api });
+  } catch (e) {
+    error = e;
+  }
+  check(
+    "a keyword the literal keywords page names without its ## heading fails",
+    /Literal-Keywords\.md names Empty/.test(String(error?.message)),
+    String(error?.message),
+  );
+}
+{
+  // An unquoted True, False or Null in symbols: is YAML's boolean or null, not a name.
+  const built = (symbols) => ({
+    srcRel: "Reference/Literal-Keywords.md",
+    permalink: "/Reference/Literal-Keywords",
+    frontmatter: { title: "Literal Keywords", symbols },
+    renderedContent: '<h2 id="true">True</h2>',
+  });
+  let error = null;
+  try {
+    symbolPages([built(["Nothing", true, null])]);
+  } catch (e) {
+    error = e;
+  }
+  check(
+    "a symbols: entry that YAML read as a boolean or null fails, naming the page",
+    /Literal-Keywords\.md: symbols: holds true, not a name/.test(String(error?.message)),
+    String(error?.message),
+  );
+  check(
+    "a symbols: list of quoted names passes as written",
+    show(symbolPages([built(["Nothing", "True"])])[0].symbols) === show(["Nothing", "True"]),
+  );
+}
 check(
   "a data type is the language's, at the ## heading its symbols: entry names",
   show(find("Long")) ===
diff --git a/scripts/impexp.mjs b/scripts/impexp.mjs
index 7942e1827..73547aba6 100644
--- a/scripts/impexp.mjs
+++ b/scripts/impexp.mjs
@@ -980,6 +980,40 @@ function selfTest() {
       eq(commandLineError("readme", ["P.twinproj"]), null, "readme P.twinproj");
     });
 
+    test("A double quote in an argument is answered with the command it meant", () => {
+      const why = [
+        "ERROR: an argument holds a double quote, which no Windows file name can hold:",
+        '         C:\\my out" --overwrite',
+        '       A backslash just before a closing quote, as in "C:\\out\\", makes Windows keep',
+        "       the quote in the argument, and the rest of the command line runs into it.",
+      ];
+      const meant = "       Leave the backslash off the end of a name in quotes. The command meant is:";
+      eq(quoteMistake(["export", "P.twinproj", "tree", "--overwrite"], "impexp"), null, "no quote");
+      eq(
+        quoteMistake(["export", "P.twinproj", 'C:\\my out" --overwrite'], "impexp"),
+        [...why, meant, '         impexp export P.twinproj "C:\\my out" --overwrite'].join("\n"),
+        "a folder in quotes",
+      );
+      const last = (argv) => quoteMistake(argv, "impexp").split("\n").at(-1);
+      eq(
+        last(["export", "P.twinproj", 'out\\" --overwrite']),
+        "         impexp export P.twinproj out --overwrite",
+        "two backslashes",
+      );
+      eq(
+        last(["export", "P.twinproj", 'C:" --overwrite']),
+        "         impexp export P.twinproj C:\\ --overwrite",
+        "a drive",
+      );
+      eq(
+        last(["import", 'C:\\a b\\P.twinproj" tree']),
+        '         impexp import "C:\\a b\\P.twinproj" tree',
+        "the project",
+      );
+      eq(last(['export"']), "       Leave the backslash off the end of a name in quotes.", "nothing to suggest");
+      eq(quoteMistake(['export"'], "impexp").split("\n").length, 5, "no command when it would be refused");
+    });
+
     test("The exit code says why a command failed, and that it warned", () => {
       eq(Object.values(EXIT).join(), "0,1,2,3,4,5,6", "the documented codes");
       refused(() => readProject(at("nowhere.twinproj")), /does not exist/, "missing");
@@ -1097,27 +1131,99 @@ function usageError(message) {
   return EXIT.usage;
 }
 
-function main(argv) {
-  const opts = { overwrite: false };
-  const words = [];
-  let help = false,
-    runSelfTest = false;
+// The options and the words of a command line, and what is wrong with it, or
+// null. An unknown option is wrong even after --help.
+function parseCommandLine(argv) {
+  const c = { overwrite: false, help: false, selfTest: false, words: [], problem: null };
   for (const a of argv) {
-    if (a === "--overwrite") opts.overwrite = true;
-    else if (a === "--self-test") runSelfTest = true;
-    else if (a === "--help" || a === "-h") help = true;
-    else if (/^-./.test(a)) return usageError(`unknown option: ${a}`);
-    else words.push(a);
+    if (a === "--overwrite") c.overwrite = true;
+    else if (a === "--self-test") c.selfTest = true;
+    else if (a === "--help" || a === "-h") c.help = true;
+    else if (/^-./.test(a)) return { ...c, problem: `unknown option: ${a}` };
+    else c.words.push(a);
+  }
+  if (c.help) return c;
+  if (c.selfTest) return c.words.length ? { ...c, problem: "--self-test takes no other arguments" } : c;
+  const [verb, ...args] = c.words;
+  c.problem = commandLineError(verb, args);
+  return c;
+}
+
+// An argument as it is typed at a command prompt: in quotes when it holds a
+// space or a character cmd.exe reads.
+function shellWord(a) {
+  return a === "" || /[ \t&|<>^()%!,;=]/.test(a) ? `"${a}"` : a;
+}
+
+// The error for a command line that holds a double quote, or null. Windows
+// splits a command line so that a backslash just before a quote keeps the quote
+// in the argument: `"C:\out\" --overwrite` arrives as one argument,
+// `C:\out" --overwrite`. No Windows file name holds a double quote, so an
+// argument that does is this mistake. The command it meant is each such
+// argument's text before the quote, less the backslashes at its end, followed by
+// the words the quote swallowed; it is shown, after `program`, only when it
+// passes the checks a command line must pass. The arguments are not repaired
+// here: the tB executable reads `"C:\out\"` as the folder, and a reader who
+// learnt that the script repairs it would expect the same of every program.
+function quoteMistake(argv, program) {
+  const bad = argv.find((a) => a.includes('"'));
+  if (bad === undefined) return null;
+  const meant = [];
+  for (const a of argv) {
+    const q = a.indexOf('"');
+    if (q < 0) {
+      meant.push(a);
+      continue;
+    }
+    let head = a.slice(0, q).replace(/\\+$/, "");
+    if (/^[A-Za-z]:$/.test(head)) head += "\\";
+    if (head !== "") meant.push(head);
+    for (const w of a
+      .slice(q + 1)
+      .replaceAll('"', " ")
+      .split(/[ \t]+/))
+      if (w !== "") meant.push(w);
+  }
+  const lines = [
+    "ERROR: an argument holds a double quote, which no Windows file name can hold:",
+    `         ${bad}`,
+    '       A backslash just before a closing quote, as in "C:\\out\\", makes Windows keep',
+    "       the quote in the argument, and the rest of the command line runs into it.",
+  ];
+  if (parseCommandLine(meant).problem === null) {
+    lines.push("       Leave the backslash off the end of a name in quotes. The command meant is:");
+    lines.push(`         ${program} ${meant.map(shellWord).join(" ")}`);
+  } else {
+    lines.push("       Leave the backslash off the end of a name in quotes.");
+  }
+  return lines.join("\n");
+}
+
+// How this script was run, for a command to copy: node and the script, by its
+// path from the current folder when it is under it.
+function programText() {
+  const script = process.argv[1];
+  const rel = path.relative(process.cwd(), script);
+  const shown = rel !== "" && !rel.startsWith("..") && !path.isAbsolute(rel) ? rel : script;
+  return `${path.parse(process.execPath).name} ${shellWord(shown)}`;
+}
+
+function main(argv) {
+  const mistake = quoteMistake(argv, programText());
+  if (mistake !== null) {
+    console.error(mistake);
+    return EXIT.usage;
   }
-  if (help) {
+  const c = parseCommandLine(argv);
+  if (c.problem) return usageError(c.problem);
+  if (c.help) {
     console.log(USAGE);
     return 0;
   }
-  if (runSelfTest) return words.length ? usageError("--self-test takes no other arguments") : selfTest();
+  if (c.selfTest) return selfTest();
+  const opts = { overwrite: c.overwrite };
 
-  const [verb, ...args] = words;
-  const problem = commandLineError(verb, args);
-  if (problem) return usageError(problem);
+  const [verb, ...args] = c.words;
   const [project, folder] = args;
 
   if (verb === "export" || verb === "import") {
diff --git a/scripts/impexp.py b/scripts/impexp.py
index b238246d7..35b267950 100644
--- a/scripts/impexp.py
+++ b/scripts/impexp.py
@@ -945,6 +945,36 @@ def t_command_line():
         test('A command line in the wrong shape is refused before anything is read',
              t_command_line)
 
+        def t_quote_mistake():
+            why = [
+                'ERROR: an argument holds a double quote, which no Windows file name can hold:',
+                '         C:\\my out" --overwrite',
+                '       A backslash just before a closing quote, as in "C:\\out\\", makes Windows keep',
+                '       the quote in the argument, and the rest of the command line runs into it.',
+            ]
+            meant = '       Leave the backslash off the end of a name in quotes. The command meant is:'
+            eq(quote_mistake(['export', 'P.twinproj', 'tree', '--overwrite'], 'impexp'), None,
+               'no quote')
+            eq(quote_mistake(['export', 'P.twinproj', 'C:\\my out" --overwrite'], 'impexp'),
+               '\n'.join(why + [meant,
+                                '         impexp export P.twinproj "C:\\my out" --overwrite']),
+               'a folder in quotes')
+
+            def last(argv):
+                return quote_mistake(argv, 'impexp').split('\n')[-1]
+            eq(last(['export', 'P.twinproj', 'out\\" --overwrite']),
+               '         impexp export P.twinproj out --overwrite', 'two backslashes')
+            eq(last(['export', 'P.twinproj', 'C:" --overwrite']),
+               '         impexp export P.twinproj C:\\ --overwrite', 'a drive')
+            eq(last(['import', 'C:\\a b\\P.twinproj" tree']),
+               '         impexp import "C:\\a b\\P.twinproj" tree', 'the project')
+            eq(last(['export"']), '       Leave the backslash off the end of a name in quotes.',
+               'nothing to suggest')
+            eq(len(quote_mistake(['export"'], 'impexp').split('\n')), 5,
+               'no command when it would be refused')
+        test('A double quote in an argument is answered with the command it meant',
+             t_quote_mistake)
+
         def t_exit_codes():
             eq(','.join(str(v) for v in EXIT.values()), '0,1,2,3,4,5,6',
                'the documented codes')
@@ -1091,34 +1121,110 @@ def _usage_error(message):
     return EXIT['usage']
 
 
-def main(argv):
-    overwrite = False
-    words = []
-    show_help = run_self_test = False
+def parse_command_line(argv):
+    """The options and the words of a command line, and what is wrong with it.
+
+    A dict of overwrite, help, self_test, words and problem, which is None when
+    nothing is. An unknown option is wrong even after --help.
+    """
+    c = dict(overwrite=False, help=False, self_test=False, words=[], problem=None)
     for a in argv:
         if a == '--overwrite':
-            overwrite = True
+            c['overwrite'] = True
         elif a == '--self-test':
-            run_self_test = True
+            c['self_test'] = True
         elif a in ('--help', '-h'):
-            show_help = True
+            c['help'] = True
         elif len(a) > 1 and a.startswith('-'):
-            return _usage_error(f'unknown option: {a}')
+            c['problem'] = f'unknown option: {a}'
+            return c
         else:
-            words.append(a)
-    if show_help:
+            c['words'].append(a)
+    if c['help']:
+        return c
+    if c['self_test']:
+        if c['words']:
+            c['problem'] = '--self-test takes no other arguments'
+        return c
+    words = c['words']
+    c['problem'] = command_line_error(words[0] if words else None, words[1:])
+    return c
+
+
+def _shell_word(a):
+    """An argument as it is typed at a command prompt: in quotes when it holds
+    a space or a character cmd.exe reads."""
+    return f'"{a}"' if a == '' or re.search(r'[ \t&|<>^()%!,;=]', a) else a
+
+
+def quote_mistake(argv, program):
+    """The error for a command line that holds a double quote, or None.
+
+    Windows splits a command line so that a backslash just before a quote
+    keeps the quote in the argument: `"C:\\out\\" --overwrite` arrives as one
+    argument, `C:\\out" --overwrite`. No Windows file name holds a double
+    quote, so an argument that does is this mistake. The command it meant is
+    each such argument's text before the quote, less the backslashes at its
+    end, followed by the words the quote swallowed; it is shown, after
+    `program`, only when it passes the checks a command line must pass. The
+    arguments are not repaired here: the tB executable reads `"C:\\out\\"` as
+    the folder, and a reader who learnt that the script repairs it would
+    expect the same of every program.
+    """
+    bad = next((a for a in argv if '"' in a), None)
+    if bad is None:
+        return None
+    meant = []
+    for a in argv:
+        q = a.find('"')
+        if q < 0:
+            meant.append(a)
+            continue
+        head = re.sub(r'\\+$', '', a[:q])
+        if re.fullmatch(r'[A-Za-z]:', head):
+            head += '\\'
+        if head:
+            meant.append(head)
+        meant.extend(w for w in re.split(r'[ \t]+', a[q + 1:].replace('"', ' ')) if w)
+    lines = [
+        'ERROR: an argument holds a double quote, which no Windows file name can hold:',
+        f'         {bad}',
+        '       A backslash just before a closing quote, as in "C:\\out\\", makes Windows keep',
+        '       the quote in the argument, and the rest of the command line runs into it.',
+    ]
+    if parse_command_line(meant)['problem'] is None:
+        lines.append('       Leave the backslash off the end of a name in quotes. The command meant is:')
+        lines.append(f'         {program} ' + ' '.join(_shell_word(w) for w in meant))
+    else:
+        lines.append('       Leave the backslash off the end of a name in quotes.')
+    return '\n'.join(lines)
+
+
+def _program_text():
+    """How this script was run, for a command to copy: the interpreter and the
+    script as it was named."""
+    name = os.path.splitext(os.path.basename(sys.executable))[0] or 'python'
+    return f'{name} {_shell_word(sys.argv[0])}'
+
+
+def main(argv):
+    mistake = quote_mistake(argv, _program_text())
+    if mistake is not None:
+        _err(mistake)
+        return EXIT['usage']
+    c = parse_command_line(argv)
+    if c['problem']:
+        return _usage_error(c['problem'])
+    if c['help']:
         _out(USAGE)
         return 0
-    if run_self_test:
-        if words:
-            return _usage_error('--self-test takes no other arguments')
+    if c['self_test']:
         return _self_test()
+    overwrite = c['overwrite']
 
-    verb = words[0] if words else None
+    words = c['words']
+    verb = words[0]
     args = words[1:]
-    problem = command_line_error(verb, args)
-    if problem:
-        return _usage_error(problem)
     project = args[0]
     folder = args[1] if len(args) > 1 else None
 
diff --git a/scripts/impexp/impexp.twinproj b/scripts/impexp/impexp.twinproj
index 49a61f60b..b362d8afb 100644
Binary files a/scripts/impexp/impexp.twinproj and b/scripts/impexp/impexp.twinproj differ
diff --git a/scripts/impexp/src/Sources/MainModule.twin b/scripts/impexp/src/Sources/MainModule.twin
index 9c05e3021..bafa1d6fa 100644
--- a/scripts/impexp/src/Sources/MainModule.twin
+++ b/scripts/impexp/src/Sources/MainModule.twin
@@ -7,6 +7,11 @@ Module MainModule
     Private Declare PtrSafe Function GetConsoleMode Lib "kernel32" (ByVal hConsoleHandle As LongPtr, ByRef lpMode As Long) As Long
     Private Declare PtrSafe Function WriteConsoleW Lib "kernel32" (ByVal hConsoleOutput As LongPtr, ByVal lpBuffer As LongPtr, ByVal nNumberOfCharsToWrite As Long, ByRef lpNumberOfCharsWritten As Long, ByVal lpReserved As LongPtr) As Long
     Private Declare PtrSafe Function WriteFile Lib "kernel32" (ByVal hFile As LongPtr, ByVal lpBuffer As LongPtr, ByVal nNumberOfBytesToWrite As Long, ByRef lpNumberOfBytesWritten As Long, ByVal lpOverlapped As LongPtr) As Long
+    Private Declare PtrSafe Function GetCommandLineW Lib "kernel32" () As LongPtr
+    Private Declare PtrSafe Function CommandLineToArgvW Lib "shell32" (ByVal lpCmdLine As LongPtr, ByRef pNumArgs As Long) As LongPtr
+    Private Declare PtrSafe Function LocalFree Lib "kernel32" (ByVal hMem As LongPtr) As LongPtr
+    Private Declare PtrSafe Function lstrlenW Lib "kernel32" (ByVal lpString As LongPtr) As Long
+    Private Declare PtrSafe Sub RtlMoveMemory Lib "kernel32" (ByVal Destination As LongPtr, ByVal Source As LongPtr, ByVal Length As LongPtr)
 
     Private Const STD_OUTPUT_HANDLE As Long = -11
     Private Const STD_ERROR_HANDLE As Long = -12
@@ -103,8 +108,11 @@ Module MainModule
         End If
     End Sub
 
-    Public Function Run(ByVal argv As Collection) As Long
-        Dim overwrite As Boolean, help As Boolean, selfTesting As Boolean, words As New Collection, a As Variant
+    ' Reads the options of a command line into the flags and its other words into words, and
+    ' returns what is wrong with it, or "". An unknown option is wrong even after --help.
+    Private Function ParseCommandLine(ByVal argv As Collection, ByRef overwrite As Boolean, ByRef help As Boolean, _
+            ByRef selfTesting As Boolean, ByVal words As Collection) As String
+        Dim a As Variant
         For Each a In argv
             If a = "--overwrite" Then
                 overwrite = True
@@ -113,31 +121,128 @@ Module MainModule
             ElseIf a = "--help" Or a = "-h" Then
                 help = True
             ElseIf Len(a) > 1 And Left$(a, 1) = "-" Then
-                Run = UsageError("unknown option: " & a)
+                ParseCommandLine = "unknown option: " & a
                 Exit Function
             Else
                 words.Add a
             End If
         Next
-        If help Then
-            WriteOut Usage()
+        If help Then Exit Function
+        If selfTesting Then
+            If words.Count > 0 Then ParseCommandLine = "--self-test takes no other arguments"
             Exit Function
         End If
-        If selfTesting Then
-            If words.Count > 0 Then
-                Run = UsageError("--self-test takes no other arguments")
+        ParseCommandLine = CommandLineError(words)
+    End Function
+
+    ' An argument as it is typed at a command prompt: in quotes when it holds a space or a
+    ' character cmd.exe reads.
+    Private Function ShellWord(ByVal a As String) As String
+        Dim i As Long
+        ShellWord = a
+        If Len(a) = 0 Then
+            ShellWord = """"""
+            Exit Function
+        End If
+        For i = 1 To Len(a)
+            If InStr(" " & vbTab & "&|<>^()%!,;=", Mid$(a, i, 1)) > 0 Then
+                ShellWord = """" & a & """"
+                Exit Function
+            End If
+        Next
+    End Function
+
+    ' The error for a command line that holds a double quote, or "". Windows splits a command
+    ' line so that a backslash just before a quote keeps the quote in the argument:
+    ' "C:\out\" --overwrite arrives as one argument, C:\out" --overwrite. No Windows file name
+    ' holds a double quote, so an argument that does is this mistake. The command it meant is each
+    ' such argument's text before the quote, less the backslashes at its end, followed by the
+    ' words the quote swallowed; it is shown, after program, only when it passes the checks a
+    ' command line must pass. The arguments are not repaired here: the tB executable reads
+    ' "C:\out\" as the folder, and a reader who learnt that the script repairs it would expect
+    ' the same of every program.
+    Public Function QuoteMistake(ByVal argv As Collection, ByVal program As String) As String
+        Dim a As Variant, bad As String, found As Boolean, meant As New Collection, q As Long, head As String
+        Dim w As Variant, text As String
+        For Each a In argv
+            q = InStr(a, """")
+            If q = 0 Then
+                meant.Add a
             Else
-                Run = SelfTest.RunAll()
+                If Not found Then
+                    bad = a
+                    found = True
+                End If
+                head = Left$(a, q - 1)
+                Do While Right$(head, 1) = "\"
+                    head = Left$(head, Len(head) - 1)
+                Loop
+                If head Like "[A-Za-z]:" Then head = head & "\"
+                If Len(head) > 0 Then meant.Add head
+                For Each w In Split(Replace(Replace(Mid$(a, q + 1), """", " "), vbTab, " "), " ")
+                    If Len(w) > 0 Then meant.Add w
+                Next
             End If
+        Next
+        If Not found Then Exit Function
+
+        text = Join(Array( _
+            "ERROR: an argument holds a double quote, which no Windows file name can hold:", _
+            "         " & bad, _
+            "       A backslash just before a closing quote, as in ""C:\out\"", makes Windows keep", _
+            "       the quote in the argument, and the rest of the command line runs into it."), vbLf)
+        Dim overwrite As Boolean, help As Boolean, selfTesting As Boolean, words As New Collection, line As String
+        If Len(ParseCommandLine(meant, overwrite, help, selfTesting, words)) = 0 Then
+            line = "         " & program
+            For Each w In meant
+                line = line & " " & ShellWord(w)
+            Next
+            text = text & vbLf & "       Leave the backslash off the end of a name in quotes. The command meant is:" & vbLf & line
+        Else
+            text = text & vbLf & "       Leave the backslash off the end of a name in quotes."
+        End If
+        QuoteMistake = text
+    End Function
+
+    ' How this program was run, for a command to copy: its name as the command line gives it.
+    Private Function ProgramText() As String
+        Dim argv As LongPtr, argc As Long, p As LongPtr, n As Long, s As String
+        argv = CommandLineToArgvW(GetCommandLineW(), argc)
+        If argv = 0 Then
+            ProgramText = "impexp"
             Exit Function
         End If
+        RtlMoveMemory VarPtr(p), argv, LenB(p)
+        n = lstrlenW(p)
+        s = String$(n, vbNullChar)
+        If n > 0 Then RtlMoveMemory StrPtr(s), p, 2 * n
+        LocalFree argv
+        ProgramText = ShellWord(s)
+    End Function
 
+    Public Function Run(ByVal argv As Collection) As Long
+        Dim overwrite As Boolean, help As Boolean, selfTesting As Boolean, words As New Collection
         Dim problem As String
-        problem = CommandLineError(words)
+        problem = QuoteMistake(argv, ProgramText())
+        If Len(problem) > 0 Then
+            WriteErr problem
+            Run = Impexp.EXIT_USAGE
+            Exit Function
+        End If
+        problem = ParseCommandLine(argv, overwrite, help, selfTesting, words)
         If Len(problem) > 0 Then
             Run = UsageError(problem)
             Exit Function
         End If
+        If help Then
+            WriteOut Usage()
+            Exit Function
+        End If
+        If selfTesting Then
+            Run = SelfTest.RunAll()
+            Exit Function
+        End If
+
         Dim verb As String, project As String, folder As String
         verb = words(1)
         project = words(2)
diff --git a/scripts/impexp/src/Sources/SelfTest.twin b/scripts/impexp/src/Sources/SelfTest.twin
index 83aa574eb..18874d787 100644
--- a/scripts/impexp/src/Sources/SelfTest.twin
+++ b/scripts/impexp/src/Sources/SelfTest.twin
@@ -57,15 +57,16 @@ Module SelfTest
         RunOne "Import converts LF to CRLF in code files only", 15
         RunOne "The printing commands read the documents at the root", 16
         RunOne "A command line in the wrong shape is refused before anything is read", 17
-        RunOne "The exit code says why a command failed, and that it warned", 18
+        RunOne "A double quote in an argument is answered with the command it meant", 18
+        RunOne "The exit code says why a command failed, and that it warned", 19
 
         ' The documentation repository's own sample, when run from a checkout.
         mSample = FindSample()
         If Len(mSample) = 0 Then
             MainModule.WriteOut "  [SKIP] sample.twinpack -- only in a checkout of the documentation repository"
         Else
-            RunOne "Parse sample.twinpack", 19
-            RunOne "sample.twinpack survives export, import and export again", 20
+            RunOne "Parse sample.twinpack", 20
+            RunOne "sample.twinpack survives export, import and export again", 21
         End If
     End Sub
 
@@ -90,9 +91,10 @@ Module SelfTest
             Case 15: ImportConvertsLineEndings
             Case 16: PrintingCommandsReadDocuments
             Case 17: CommandLineWrongShape
-            Case 18: ExitCodes
-            Case 19: ParseSample
-            Case 20: SampleSurvivesRoundTrip
+            Case 18: QuoteMistakeAnswers
+            Case 19: ExitCodes
+            Case 20: ParseSample
+            Case 21: SampleSurvivesRoundTrip
         End Select
         MainModule.WriteOut "  [PASS] " & name
         mPassed = mPassed + 1
@@ -406,6 +408,31 @@ Module SelfTest
         EqS MainModule.CommandLineError(WordsOf(Array("readme", "P.twinproj"))), "", "readme P.twinproj"
     End Sub
 
+    Private Sub QuoteMistakeAnswers()
+        Dim why As String, meant As String
+        why = Join(Array( _
+            "ERROR: an argument holds a double quote, which no Windows file name can hold:", _
+            "         C:\my out"" --overwrite", _
+            "       A backslash just before a closing quote, as in ""C:\out\"", makes Windows keep", _
+            "       the quote in the argument, and the rest of the command line runs into it."), vbLf)
+        meant = "       Leave the backslash off the end of a name in quotes. The command meant is:"
+        EqS MainModule.QuoteMistake(WordsOf(Array("export", "P.twinproj", "tree", "--overwrite")), "impexp"), "", "no quote"
+        EqS MainModule.QuoteMistake(WordsOf(Array("export", "P.twinproj", "C:\my out"" --overwrite")), "impexp"), _
+            why & vbLf & meant & vbLf & "         impexp export P.twinproj ""C:\my out"" --overwrite", "a folder in quotes"
+        EqS LastLine(Array("export", "P.twinproj", "out\"" --overwrite")), "         impexp export P.twinproj out --overwrite", "two backslashes"
+        EqS LastLine(Array("export", "P.twinproj", "C:"" --overwrite")), "         impexp export P.twinproj C:\ --overwrite", "a drive"
+        EqS LastLine(Array("import", "C:\a b\P.twinproj"" tree")), "         impexp import ""C:\a b\P.twinproj"" tree", "the project"
+        EqS LastLine(Array("export""")), "       Leave the backslash off the end of a name in quotes.", "nothing to suggest"
+        EqN UBound(Split(MainModule.QuoteMistake(WordsOf(Array("export""")), "impexp"), vbLf)) + 1, 5, "no command when it would be refused"
+    End Sub
+
+    ' The last line of what QuoteMistake says about a command line.
+    Private Function LastLine(ByVal line As Variant) As String
+        Dim lines() As String
+        lines = Split(MainModule.QuoteMistake(WordsOf(line), "impexp"), vbLf)
+        LastLine = lines(UBound(lines))
+    End Function
+
     Private Sub ExitCodes()
         Dim number As Long, description As String, r As Outcome
         EqS Impexp.EXIT_DONE & "," & Impexp.EXIT_FAILED & "," & Impexp.EXIT_USAGE & "," & Impexp.EXIT_EXISTS & "," & _