fix(compiler): alias shadowed names in switch init statements

compiler/lowering.go

@@ -9275,10 +9275,11 @@ const taglessSwitchValue = "(true as boolean)"
 func (o *LoweringOwner) lowerSwitchStmt(ctx lowerFileContext, stmt *ast.SwitchStmt) ([]loweredStmt, []Diagnostic) {
 	var diagnostics []Diagnostic
 	var init []loweredStmt
+	var prelude []loweredStmt
 	if stmt.Init != nil {
-		lowered, initDiagnostics := o.lowerStmt(ctx, stmt.Init)
+		var initDiagnostics []Diagnostic
+		ctx, prelude, init, initDiagnostics = o.lowerSwitchInit(ctx, stmt.Init)
 		diagnostics = append(diagnostics, initDiagnostics...)
-		init = append(init, lowered...)
 	}
 
 	value := taglessSwitchValue
@@ -9361,7 +9362,25 @@ func (o *LoweringOwner) lowerSwitchStmt(ctx lowerFileContext, stmt *ast.SwitchSt
 		return []loweredStmt{lowered}, diagnostics
 	}
 	init = append(init, lowered)
-	return []loweredStmt{{children: init}}, diagnostics
+	return append(prelude, loweredStmt{children: init}), diagnostics
+}
+
+// lowerSwitchInit lowers the init statement of a switch or type switch, as
+// lowerStmt does for an if init. A short declaration that redeclares a name
+// its initializer reads, as in switch pos, err := f(pos), saves the outer
+// value in prelude, to emit before the block of the switch. It returns the
+// context for the rest of the switch, in which the new names are visible.
+func (o *LoweringOwner) lowerSwitchInit(
+	ctx lowerFileContext,
+	init ast.Stmt,
+) (lowerFileContext, []loweredStmt, []loweredStmt, []Diagnostic) {
+	initCtx := ctx
+	var prelude []loweredStmt
+	if stmtCtx, nextCtx, aliasPrelude, ok := o.lowerShortDeclStatementContext(ctx, init); ok {
+		initCtx, ctx, prelude = stmtCtx, nextCtx, aliasPrelude
+	}
+	lowered, diagnostics := o.lowerStmt(initCtx, init)
+	return ctx, prelude, lowered, diagnostics
 }
 
 // splitSwitchFallthrough returns the statements of a case body without its
@@ -9429,8 +9448,11 @@ func constantComparableType(ctx lowerFileContext, expr ast.Expr) string {
 func (o *LoweringOwner) lowerTypeSwitchStmt(ctx lowerFileContext, stmt *ast.TypeSwitchStmt) ([]loweredStmt, []Diagnostic) {
 	var lowered []loweredStmt
 	var diagnostics []Diagnostic
+	var prelude []loweredStmt
 	if stmt.Init != nil {
-		init, initDiagnostics := o.lowerStmt(ctx, stmt.Init)
+		var init []loweredStmt
+		var initDiagnostics []Diagnostic
+		ctx, prelude, init, initDiagnostics = o.lowerSwitchInit(ctx, stmt.Init)
 		diagnostics = append(diagnostics, initDiagnostics...)
 		lowered = append(lowered, init...)
 	}
@@ -9500,7 +9522,7 @@ func (o *LoweringOwner) lowerTypeSwitchStmt(ctx lowerFileContext, stmt *ast.Type
 		switchIR.site = o.lowerTypeSwitchSite(ctx, switchIR)
 	}
 	lowered = append(lowered, loweredStmt{typeSwitch: switchIR})
-	return lowered, diagnostics
+	return append(prelude, lowered...), diagnostics
 }
 
 // lowerTypeSwitchSite returns the hoisted runtime site of a type switch whose

tests/tests/shadow_define_init/expected.log

@@ -0,0 +1,6 @@
+switchInit: 2
+ifInit: 2
+block: 2
+single: 4
+forInit: 3
+typeSwitchInit: 5

tests/tests/shadow_define_init/shadow_define_init.go

@@ -0,0 +1,69 @@
+package main
+
+func next(n int) (int, error) {
+	return n + 1, nil
+}
+
+// switchInit redeclares pos in a switch init from the outer pos.
+func switchInit(pos int) int {
+	switch pos, err := next(pos); err {
+	case nil:
+		return pos
+	}
+	return -1
+}
+
+// ifInit redeclares pos in an if init from the outer pos.
+func ifInit(pos int) int {
+	if pos, err := next(pos); err == nil {
+		return pos
+	}
+	return -1
+}
+
+// block redeclares pos in a nested block from the outer pos.
+func block(pos int) int {
+	{
+		pos, err := next(pos)
+		if err == nil {
+			return pos
+		}
+	}
+	return -1
+}
+
+// single redeclares pos with a single value in a switch init.
+func single(pos int) int {
+	switch pos := pos * 2; pos {
+	case 4:
+		return pos
+	}
+	return -1
+}
+
+// forInit redeclares i in a for init from the outer i.
+func forInit(i int) int {
+	sum := 0
+	for i := i; i < 3; i++ {
+		sum += i
+	}
+	return sum
+}
+
+// typeSwitchInit redeclares v in a type switch init from the outer v.
+func typeSwitchInit(v any) int {
+	switch v, ok := v.(int); any(ok).(type) {
+	case bool:
+		return v
+	}
+	return -1
+}
+
+func main() {
+	println("switchInit:", switchInit(1))
+	println("ifInit:", ifInit(1))
+	println("block:", block(1))
+	println("single:", single(2))
+	println("forInit:", forInit(1))
+	println("typeSwitchInit:", typeSwitchInit(5))
+}

tests/tests/shadow_define_init/shadow_define_init.gs.ts

@@ -0,0 +1,114 @@
+// Generated file based on shadow_define_init.go
+// Updated when compliance tests are re-run, DO NOT EDIT!
+
+import * as $ from "@goscript/builtin/index.js"
+
+export function next(n: number): [number, $.GoError] {
+	return [n + 1, null]
+}
+
+export function switchInit(pos: number): number {
+	let __goscriptShadow0 = pos
+	{
+		let __goscriptTuple0: any = next(__goscriptShadow0)
+		let __goscriptShadow1: number = __goscriptTuple0[0]
+		let err: $.GoError = __goscriptTuple0[1]
+		let __goscriptSwitch0 = err
+		switch ((true as boolean)) {
+			case __goscriptSwitch0 == null:
+			{
+				return __goscriptShadow1
+				break
+			}
+		}
+	}
+	return -1
+}
+
+export function ifInit(pos: number): number {
+	let __goscriptShadow2 = pos
+	{
+		let __goscriptTuple1: any = next(__goscriptShadow2)
+		let __goscriptShadow3: number = __goscriptTuple1[0]
+		let err: $.GoError = __goscriptTuple1[1]
+		if (err == null) {
+			return __goscriptShadow3
+		}
+	}
+	return -1
+}
+
+export function block(pos: number): number {
+	{
+		let __goscriptShadow4 = pos
+		let __goscriptTuple2: any = next(__goscriptShadow4)
+		let __goscriptShadow5: number = __goscriptTuple2[0]
+		let err: $.GoError = __goscriptTuple2[1]
+		if (err == null) {
+			return __goscriptShadow5
+		}
+	}
+	return -1
+}
+
+export function single(pos: number): number {
+	let __goscriptShadow6 = pos
+	{
+		let __goscriptShadow7 = __goscriptShadow6 * 2
+		switch (__goscriptShadow7) {
+			case 4:
+			{
+				return __goscriptShadow7
+				break
+			}
+		}
+	}
+	return -1
+}
+
+export function forInit(i: number): number {
+	let sum = 0
+	{
+		let __goscriptShadow8 = i
+		for (let __goscriptShadow9 = __goscriptShadow8; __goscriptShadow9 < 3; __goscriptShadow9++) {
+			sum += __goscriptShadow9
+		}
+	}
+	return sum
+}
+
+export function typeSwitchInit(v: any): number {
+	let __goscriptShadow10 = v
+	let __goscriptTuple3: any = $.typeAssertTuple<number>(__goscriptShadow10, /* @__PURE__ */ $.basicType("int"))
+	let __goscriptShadow11: number = __goscriptTuple3[0]
+	let ok: boolean = __goscriptTuple3[1]
+	{
+		const __goscriptTypeSwitchValue = ok
+		switch ($.typeSwitchCase(__goscriptTypeSwitchValue, __goscriptStatic0())) {
+			case 0:
+				{
+					return __goscriptShadow11
+				}
+				break
+		}
+	}
+	return -1
+}
+
+export async function main(): globalThis.Promise<void> {
+	await $.println("switchInit:", switchInit(1))
+	await $.println("ifInit:", ifInit(1))
+	await $.println("block:", block(1))
+	await $.println("single:", single(2))
+	await $.println("forInit:", forInit(1))
+	await $.println("typeSwitchInit:", typeSwitchInit($.basicInterfaceValue(5, "int")))
+}
+
+var __goscriptStatic0$value: any
+function __goscriptStatic0(): any {
+	return __goscriptStatic0$value ??= ($.typeSwitchSite([/* @__PURE__ */ $.basicType("bool")]))
+}
+
+if ($.isMainScript(import.meta)) {
+	await main()
+}

tests/tests/shadow_define_init/tsconfig.json

@@ -0,0 +1,25 @@
+{
+  "compilerOptions": {
+    "paths": {
+      "*": [
+        "./*"
+      ],
+      "@go/github.com/s4wave/goscript/*": [
+        "../../../*"
+      ],
+      "@goscript/*": [
+        "../../../tests/tests/shadow_define_init/run/output/@goscript/*",
+        "../../../gs/*",
+        "../../../tests/deps/*"
+      ],
+      "@goscript/github.com/s4wave/goscript/tests/tests/shadow_define_init/*": [
+        "./*"
+      ]
+    }
+  },
+  "extends": "../../../tests/tsconfig.base.json",
+  "include": [
+    "index.ts",
+    "shadow_define_init.gs.ts"
+  ]
+}