fix(43879): forbid async in the left hand in a for-of statement (#43886)

Author: a-tarasyuk

src/compiler/checker.ts

@@ -41471,6 +41471,12 @@ namespace ts {
                 }
             }
 
+            if (isForOfStatement(forInOrOfStatement) && !(forInOrOfStatement.flags & NodeFlags.AwaitContext) &&
+                isIdentifier(forInOrOfStatement.initializer) && forInOrOfStatement.initializer.escapedText === "async") {
+                grammarErrorOnNode(forInOrOfStatement.initializer, Diagnostics.The_left_hand_side_of_a_for_of_statement_may_not_be_async);
+                return false;
+            }
+
             if (forInOrOfStatement.initializer.kind === SyntaxKind.VariableDeclarationList) {
                 const variableList = <VariableDeclarationList>forInOrOfStatement.initializer;
                 if (!checkGrammarVariableDeclarationList(variableList)) {

src/compiler/diagnosticMessages.json

@@ -319,6 +319,10 @@
         "category": "Error",
         "code": 1105
     },
+    "The left-hand side of a 'for...of' statement may not be 'async'.": {
+        "category": "Error",
+        "code": 1106
+    },
     "Jump target cannot cross function boundary.": {
         "category": "Error",
         "code": 1107

tests/baselines/reference/for-inStatementsAsyncIdentifier.js

@@ -0,0 +1,8 @@
+//// [for-inStatementsAsyncIdentifier.ts]
+var async;
+for (async in { a: 1, b: 2 }) {}
+
+
+//// [for-inStatementsAsyncIdentifier.js]
+var async;
+for (async in { a: 1, b: 2 }) { }

tests/baselines/reference/for-inStatementsAsyncIdentifier.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/conformance/statements/for-inStatements/for-inStatementsAsyncIdentifier.ts ===
+var async;
+>async : Symbol(async, Decl(for-inStatementsAsyncIdentifier.ts, 0, 3))
+
+for (async in { a: 1, b: 2 }) {}
+>async : Symbol(async, Decl(for-inStatementsAsyncIdentifier.ts, 0, 3))
+>a : Symbol(a, Decl(for-inStatementsAsyncIdentifier.ts, 1, 15))
+>b : Symbol(b, Decl(for-inStatementsAsyncIdentifier.ts, 1, 21))
+

tests/baselines/reference/for-inStatementsAsyncIdentifier.types

@@ -0,0 +1,12 @@
+=== tests/cases/conformance/statements/for-inStatements/for-inStatementsAsyncIdentifier.ts ===
+var async;
+>async : any
+
+for (async in { a: 1, b: 2 }) {}
+>async : any
+>{ a: 1, b: 2 } : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+

tests/baselines/reference/parserForOfStatement22.errors.txt

@@ -0,0 +1,9 @@
+tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement22.ts(2,6): error TS1106: The left-hand side of a 'for...of' statement may not be 'async'.
+
+
+==== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement22.ts (1 errors) ====
+    var async;
+    for (async of [1, 2]) {}
+         ~~~~~
+!!! error TS1106: The left-hand side of a 'for...of' statement may not be 'async'.
+    

tests/baselines/reference/parserForOfStatement22.js

@@ -0,0 +1,8 @@
+//// [parserForOfStatement22.ts]
+var async;
+for (async of [1, 2]) {}
+
+
+//// [parserForOfStatement22.js]
+var async;
+for (async of [1, 2]) { }

tests/baselines/reference/parserForOfStatement22.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement22.ts ===
+var async;
+>async : Symbol(async, Decl(parserForOfStatement22.ts, 0, 3))
+
+for (async of [1, 2]) {}
+>async : Symbol(async, Decl(parserForOfStatement22.ts, 0, 3))
+

tests/baselines/reference/parserForOfStatement22.types

@@ -0,0 +1,10 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement22.ts ===
+var async;
+>async : any
+
+for (async of [1, 2]) {}
+>async : any
+>[1, 2] : number[]
+>1 : 1
+>2 : 2
+

tests/baselines/reference/parserForOfStatement23.js

@@ -0,0 +1,12 @@
+//// [parserForOfStatement23.ts]
+async function foo(x: any) {
+    var async;
+    for await (async of x) {}
+}
+
+
+//// [parserForOfStatement23.js]
+async function foo(x) {
+    var async;
+    for await (async of x) { }
+}

tests/baselines/reference/parserForOfStatement23.symbols

@@ -0,0 +1,13 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement23.ts ===
+async function foo(x: any) {
+>foo : Symbol(foo, Decl(parserForOfStatement23.ts, 0, 0))
+>x : Symbol(x, Decl(parserForOfStatement23.ts, 0, 19))
+
+    var async;
+>async : Symbol(async, Decl(parserForOfStatement23.ts, 1, 7))
+
+    for await (async of x) {}
+>async : Symbol(async, Decl(parserForOfStatement23.ts, 1, 7))
+>x : Symbol(x, Decl(parserForOfStatement23.ts, 0, 19))
+}
+

tests/baselines/reference/parserForOfStatement23.types

@@ -0,0 +1,13 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement23.ts ===
+async function foo(x: any) {
+>foo : (x: any) => Promise<void>
+>x : any
+
+    var async;
+>async : any
+
+    for await (async of x) {}
+>async : any
+>x : any
+}
+

tests/baselines/reference/parserForOfStatement24.js

@@ -0,0 +1,9 @@
+//// [parserForOfStatement24.ts]
+var async;
+for ((async) of [1, 2]);
+
+
+//// [parserForOfStatement24.js]
+var async;
+for ((async) of [1, 2])
+    ;

tests/baselines/reference/parserForOfStatement24.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement24.ts ===
+var async;
+>async : Symbol(async, Decl(parserForOfStatement24.ts, 0, 3))
+
+for ((async) of [1, 2]);
+>async : Symbol(async, Decl(parserForOfStatement24.ts, 0, 3))
+

tests/baselines/reference/parserForOfStatement24.types

@@ -0,0 +1,11 @@
+=== tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement24.ts ===
+var async;
+>async : any
+
+for ((async) of [1, 2]);
+>(async) : any
+>async : any
+>[1, 2] : number[]
+>1 : 1
+>2 : 2
+

tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement22.ts

@@ -0,0 +1,4 @@
+// @target: esnext
+
+var async;
+for (async of [1, 2]) {}

tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement23.ts

@@ -0,0 +1,6 @@
+// @target: esnext
+
+async function foo(x: any) {
+    var async;
+    for await (async of x) {}
+}

tests/cases/conformance/parser/ecmascript6/Iterators/parserForOfStatement24.ts

@@ -0,0 +1,4 @@
+// @target: esnext
+
+var async;
+for ((async) of [1, 2]);

tests/cases/conformance/statements/for-inStatements/for-inStatementsAsyncIdentifier.ts

@@ -0,0 +1,4 @@
+// @target: esnext
+
+var async;
+for (async in { a: 1, b: 2 }) {}