update implicit open unions

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
       - uses: roc-lang/setup-roc@cbe782d6f165b89c87d99f50a59ac4f5f73b4427 # ratchet:roc-lang/setup-roc@v0.3.0
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
       - name: Install Rust toolchain
         run: |
           rustup toolchain install "${{ needs.rust-version.outputs.version }}" --profile minimal --target x86_64-unknown-linux-musl --component llvm-tools-preview
@@ -63,7 +63,7 @@ jobs:
       - uses: roc-lang/setup-roc@cbe782d6f165b89c87d99f50a59ac4f5f73b4427 # ratchet:roc-lang/setup-roc@v0.3.0
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
       - name: Install Rust toolchain
         shell: bash
         run: |
@@ -108,7 +108,7 @@ jobs:
       - uses: roc-lang/setup-roc@cbe782d6f165b89c87d99f50a59ac4f5f73b4427 # ratchet:roc-lang/setup-roc@v0.3.0
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
       - name: Install Rust toolchain
         shell: bash
         run: |

.github/workflows/deploy-docs.yml

@@ -40,7 +40,7 @@ jobs:
         uses: roc-lang/setup-roc@bd311e2fb815a3d2255f7ee14a922f0b736e020b
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
 
       - name: Restore released docs
         env:

.github/workflows/release.yml

@@ -114,7 +114,7 @@ jobs:
         uses: roc-lang/setup-roc@bd311e2fb815a3d2255f7ee14a922f0b736e020b
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
 
       - name: Install Zig
         uses: mlugg/setup-zig@8d6198c65fb0feaa111df26e6b467fea8345e46f
@@ -215,7 +215,7 @@ jobs:
         uses: roc-lang/setup-roc@bd311e2fb815a3d2255f7ee14a922f0b736e020b
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
 
       - name: Install Rust
         shell: bash
@@ -260,7 +260,7 @@ jobs:
         uses: roc-lang/setup-roc@bd311e2fb815a3d2255f7ee14a922f0b736e020b
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
 
       - name: Create docs staging tree
         run: mkdir -p docs-site
@@ -408,7 +408,7 @@ jobs:
         uses: roc-lang/setup-roc@bd311e2fb815a3d2255f7ee14a922f0b736e020b
         with:
           version: nightly-new-compiler
-          nightly-tag: nightly-2026-09-04-c125b82
+          nightly-tag: nightly-2026-09-22-e494788
 
       - name: Download release metadata
         uses: actions/download-artifact@v8

examples/file-size.roc

@@ -19,7 +19,7 @@ main! = |args| {
 	Ok({})
 }
 
-path_argument : List(OsStr) -> Try(Path, [MissingPathArgument, ..])
+path_argument : List(OsStr) -> Try(Path, [MissingPathArgument])
 path_argument = |args|
 	match args {
 		[first, ..] => Ok(Path.from_os_str(first))

examples/http-client.roc

@@ -87,4 +87,8 @@ reject_invalid_utf8! = || {
 }
 
 write_line! : Str => Try({}, _)
-write_line! = |message| Stdout.line!(message)
+write_line! = |message|
+	match Stdout.line!(message) {
+		Ok(value) => Ok(value)
+		Err(StdoutErr(err)) => Err(StdoutErr(err))
+	}

platform/Cmd.roc

@@ -45,7 +45,7 @@ Cmd :: {
 	## ```roc
 	## Cmd.exec!("echo", ["hello world"])?
 	## ```
-	exec! : OsStr, List(OsStr) => Try({}, [ExecFailed({ command : Str, exit_code : I32 }), FailedToGetExitCode({ command : Str, err : IOErr }), ..])
+	exec! : OsStr, List(OsStr) => Try({}, [ExecFailed({ command : Str, exit_code : I32 }), FailedToGetExitCode({ command : Str, err : IOErr })])
 	exec! = |program, arguments| {
 		command = "${OsStr.display(program)} ${Str.join_with(arguments.map(OsStr.display), " ")}"
 
@@ -72,7 +72,7 @@ Cmd :: {
 	##     .env("RUST_BACKTRACE", "1")
 	##     .exec_cmd!()?
 	## ```
-	exec_cmd! : Cmd => Try({}, [ExecCmdFailed({ command : Str, exit_code : I32 }), FailedToGetExitCode({ command : Str, err : IOErr }), ..])
+	exec_cmd! : Cmd => Try({}, [ExecCmdFailed({ command : Str, exit_code : I32 }), FailedToGetExitCode({ command : Str, err : IOErr })])
 	exec_cmd! = |cmd| {
 		command = to_str(cmd)
 		exit_code = exec_exit_code!(cmd)?
@@ -98,7 +98,7 @@ Cmd :: {
 	##
 	## Stdout.line!("Echo output: ${cmd_output.stdout_utf8}")?
 	## ```
-	exec_output! : Cmd => Try({ stdout_utf8 : Str, stderr_utf8_lossy : Str }, [StdoutContainsInvalidUtf8({ cmd_str : Str, err : [BadUtf8({ problem : _, index : U64 })] }), NonZeroExitCode({ command : Str, exit_code : I32, stdout_utf8_lossy : Str, stderr_utf8_lossy : Str }), FailedToGetExitCode({ command : Str, err : IOErr }), ..])
+	exec_output! : Cmd => Try({ stdout_utf8 : Str, stderr_utf8_lossy : Str }, [StdoutContainsInvalidUtf8({ cmd_str : Str, err : [BadUtf8({ problem : _, index : U64 })] }), NonZeroExitCode({ command : Str, exit_code : I32, stdout_utf8_lossy : Str, stderr_utf8_lossy : Str }), FailedToGetExitCode({ command : Str, err : IOErr })])
 	exec_output! = |cmd| {
 		cmd_str = to_str(cmd)
 		exec_try = Host.cmd_exec_output!(to_host_cmd(cmd))
@@ -136,7 +136,7 @@ Cmd :: {
 	##
 	## Stdout.line!("${Str.inspect(cmd_output)}")? # {stderr_bytes: [], stdout_bytes: [72, 105, 10]}
 	## ```
-	exec_output_bytes! : Cmd => Try({ stderr_bytes : List(U8), stdout_bytes : List(U8) }, [NonZeroExitCodeB({ exit_code : I32, stdout_bytes : List(U8), stderr_bytes : List(U8) }), FailedToGetExitCodeB(IOErr), ..])
+	exec_output_bytes! : Cmd => Try({ stderr_bytes : List(U8), stdout_bytes : List(U8) }, [NonZeroExitCodeB({ exit_code : I32, stdout_bytes : List(U8), stderr_bytes : List(U8) }), FailedToGetExitCodeB(IOErr)])
 	exec_output_bytes! = |cmd| {
 		exec_try = Host.cmd_exec_output!(to_host_cmd(cmd))
 
@@ -164,7 +164,7 @@ Cmd :: {
 	## ```roc
 	## exit_code = Cmd.new("cat").arg("non_existent.txt").exec_exit_code!()?
 	## ```
-	exec_exit_code! : Cmd => Try(I32, [FailedToGetExitCode({ command : Str, err : IOErr }), ..])
+	exec_exit_code! : Cmd => Try(I32, [FailedToGetExitCode({ command : Str, err : IOErr })])
 	exec_exit_code! = |cmd| {
 		command = to_str(cmd)
 

platform/Env.roc

@@ -33,7 +33,7 @@ Env :: [].{
 	## Reads the given environment variable.
 	##
 	## Returns `Err(VarNotFound(name))` if the variable is not set.
-	var! : OsStr => Try(OsStr, [VarNotFound(OsStr), EnvErr(IOErr), ..])
+	var! : OsStr => Try(OsStr, [VarNotFound(OsStr), EnvErr(IOErr)])
 	var! = |name|
 		match Host.env_var!(OsStr.to_raw(name)) {
 			Ok(raw) => Ok(OsStr.from_raw(raw))
@@ -42,7 +42,7 @@ Env :: [].{
 		}
 
 	## Reads the given environment variable as a string if its native value is valid text.
-	var_str! : OsStr => Try(Str, [VarNotFound(OsStr), EnvErr(IOErr), InvalidStr(U64), ..])
+	var_str! : OsStr => Try(Str, [VarNotFound(OsStr), EnvErr(IOErr), InvalidStr(U64)])
 	var_str! = |name|
 		match var!(name) {
 			Ok(value) =>
@@ -58,7 +58,7 @@ Env :: [].{
 	## from the environment.
 	##
 	## Returns `Err(CwdUnavailable)` if the cwd cannot be determined.
-	cwd! : () => Try(Path.Path, [CwdUnavailable, ..])
+	cwd! : () => Try(Path.Path, [CwdUnavailable])
 	cwd! = ||
 		match Host.env_cwd!() {
 			Ok(raw) => Ok(Path.from_raw(raw))
@@ -69,15 +69,15 @@ Env :: [].{
 	##
 	## Returns `Err(InvalidCwd(err))` when the path cannot be used as a working
 	## directory. The process-wide change remains in effect until changed again.
-	set_cwd! : Path.Path => Try({}, [InvalidCwd(IOErr), ..])
+	set_cwd! : Path.Path => Try({}, [InvalidCwd(IOErr)])
 	set_cwd! = |path|
 		Host.env_set_cwd!(Path.to_raw(path))
 			.map_err(|err| InvalidCwd(err))
 
 	## Gets the path to the currently-running executable.
 	##
 	## Returns `Err(ExePathUnavailable)` if the path cannot be determined.
-	exe_path! : () => Try(Path.Path, [ExePathUnavailable, ..])
+	exe_path! : () => Try(Path.Path, [ExePathUnavailable])
 	exe_path! = ||
 		match Host.env_exe_path!() {
 			Ok(raw) => Ok(Path.from_raw(raw))
@@ -90,7 +90,7 @@ Env :: [].{
 	## another value. Unlike [`exe_path!`](#exe_path!), it is returned as an
 	## [`OsStr`](OsStr), preserving the value exactly without treating it as a path.
 	## Returns `Err(ProgramNameUnavailable)` if the launcher supplied no first argument.
-	program_name! : () => Try(OsStr, [ProgramNameUnavailable, ..])
+	program_name! : () => Try(OsStr, [ProgramNameUnavailable])
 	program_name! = ||
 		match Host.env_program_name!() {
 			Ok(raw) => Ok(OsStr.from_raw(raw))
@@ -99,16 +99,16 @@ Env :: [].{
 
 	## Atomically create a private directory in the system temporary directory.
 	## The caller owns cleanup. Unix directories have mode 0700.
-	create_temp_dir! : () => Try(Path.Path, [TempDirErr(IOErr), ..])
+	create_temp_dir! : () => Try(Path.Path, [TempDirErr(IOErr)])
 	create_temp_dir! = || create_temp_dir_with_prefix!("roc-")
 
 	## Create a private temporary directory with a filename prefix.
-	create_temp_dir_with_prefix! : Str => Try(Path.Path, [TempDirErr(IOErr), ..])
+	create_temp_dir_with_prefix! : Str => Try(Path.Path, [TempDirErr(IOErr)])
 	create_temp_dir_with_prefix! = |prefix| create_temp_dir_in!(temp_dir!(), prefix)
 
 	## Create a private temporary directory under an existing parent directory.
 	## Prefixes cannot contain separators, colons, NUL, or be `.` or `..`.
-	create_temp_dir_in! : Path.Path, Str => Try(Path.Path, [TempDirErr(IOErr), ..])
+	create_temp_dir_in! : Path.Path, Str => Try(Path.Path, [TempDirErr(IOErr)])
 	create_temp_dir_in! = |parent, prefix|
 		Host.env_create_temp_dir!(Path.to_raw(parent), prefix).map_ok(Path.from_raw).map_err(|err| TempDirErr(err))
 
@@ -122,7 +122,7 @@ Env :: [].{
 	## 	Path.read_utf8!(file)
 	## })?
 	## ```
-	with_temp_dir! : (Path.Path => Try(a, err)) => Try(a, [TempDirErr(IOErr), CallbackErr(err), CleanupErr(IOErr, Path.Path), CallbackAndCleanupErr(err, IOErr, Path.Path), ..])
+	with_temp_dir! : (Path.Path => Try(a, err)) => Try(a, [TempDirErr(IOErr), CallbackErr(err), CleanupErr(IOErr, Path.Path), CallbackAndCleanupErr(err, IOErr, Path.Path)])
 	with_temp_dir! = |callback!| {
 		path = create_temp_dir!()?
 		result = callback!(path)

platform/Http.roc

@@ -27,7 +27,7 @@ Http :: [].{
 	## request = Request.from_method(GET).with_uri("https://www.roc-lang.org")
 	## response = Http.send!(request)?
 	## ```
-	send! : Request => Try(Response, [InvalidUrl(Url.ParseErr), HttpErr(TransportErr), ..])
+	send! : Request => Try(Response, [InvalidUrl(Url.ParseErr), HttpErr(TransportErr)])
 	send! = |request| {
 		url = Url.parse(Request.uri(request)) ? InvalidUrl
 		canonical_url = Url.without_fragment(url)
@@ -41,7 +41,7 @@ Http :: [].{
 	##
 	## This uses Roc's builtin JSON encoder, so the value's type determines the
 	## encoder through static dispatch.
-	with_json_body : Request, _ => Try(Request, [JsonErr(_), ..])
+	with_json_body : Request, _ => Try(Request, [JsonErr(_)])
 	with_json_body = |request, value| {
 		body = Json.to_str_try(value) ? JsonErr
 
@@ -53,7 +53,7 @@ Http :: [].{
 	}
 
 	## Encode a value as JSON, attach it to the request body, and send it.
-	send_json! : Request, _ => Try(Response, [JsonErr(_), InvalidUrl(Url.ParseErr), HttpErr(TransportErr), ..])
+	send_json! : Request, _ => Try(Response, [JsonErr(_), InvalidUrl(Url.ParseErr), HttpErr(TransportErr)])
 	send_json! = |request, value| {
 		json_request = with_json_body(request, value)?
 
@@ -68,7 +68,7 @@ Http :: [].{
 	## ```roc
 	## hello_str = Http.get_utf8!("http://localhost:8000")?
 	## ```
-	get_utf8! : Url.Url => Try(Str, [BadBody(Str), InvalidUrl(Url.ParseErr), HttpErr(TransportErr), ..])
+	get_utf8! : Url.Url => Try(Str, [BadBody(Str), InvalidUrl(Url.ParseErr), HttpErr(TransportErr)])
 	get_utf8! = |url| {
 		response = send!(Request.from_method(GET).with_uri(Url.to_str(url)))?
 		body = Str.from_utf8(Response.body(response)) ? |_| BadBody("get_utf8!: response body was not valid UTF-8")
@@ -80,7 +80,7 @@ Http :: [].{
 	##
 	## This uses Roc's builtin JSON parser, so the expected result type
 	## determines the parser through static dispatch.
-	decode_json_response : Response => Try(_, [BadBody(Str), JsonErr(_), ..])
+	decode_json_response : Response => Try(_, [BadBody(Str), JsonErr(_)])
 	decode_json_response = |response| {
 		body = Str.from_utf8(Response.body(response)) ? |_| BadBody("decode_json_response: response body was not valid UTF-8")
 		decoded = Json.parse(body) ? JsonErr
@@ -97,7 +97,7 @@ Http :: [].{
 	## payload : Try({ foo : Str }, _)
 	## payload = Http.get!("http://localhost:8000")
 	## ```
-	get! : Url.Url => Try(_, [BadBody(Str), InvalidUrl(Url.ParseErr), HttpErr(TransportErr), JsonErr(_), ..])
+	get! : Url.Url => Try(_, [BadBody(Str), InvalidUrl(Url.ParseErr), HttpErr(TransportErr), JsonErr(_)])
 	get! = |url| {
 		response = send!(Request.from_method(GET).with_uri(Url.to_str(url)))?
 

platform/Locale.roc

@@ -91,9 +91,9 @@ Locale :: { raw : Str }.{
 	## `POSIX` locales are not language tags and are ignored.
 	##
 	## Returns `Err(NotAvailable)` if the locale cannot be determined.
-	get! : () => Try(Locale, [NotAvailable, ..])
+	get! : () => Try(Locale, [NotAvailable])
 	get! = || {
-		raw = widen_locale_err(Host.locale_get!())?
+		raw = Host.locale_get!()?
 		Ok(Locale.{ raw })
 	}
 
@@ -213,13 +213,6 @@ parse_err_to_str = |err|
 		SubtagTooLong => "Locale subtags must be at most 8 characters"
 	}
 
-widen_locale_err : Try(a, [NotAvailable]) -> Try(a, [NotAvailable, ..])
-widen_locale_err = |result|
-	match result {
-		Ok(value) => Ok(value)
-		Err(NotAvailable) => Err(NotAvailable)
-	}
-
 expect
 	match Locale.parse("en-US") {
 		Ok(locale) => Locale.to_str(locale) == "en-US"