factory: parenthesize for-of expression when necessary (microsoft#34229)

ajafff · RyanCavanaugh · commit 45d0ef94410f · 2019-10-17T10:17:33.000-07:00
Fixes: microsoft#33856
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
@@ -1811,7 +1811,7 @@ namespace ts {
         const node = <ForOfStatement>createSynthesizedNode(SyntaxKind.ForOfStatement);
         node.awaitModifier = awaitModifier;
         node.initializer = initializer;
-        node.expression = expression;
+        node.expression = isCommaSequence(expression) ? createParen(expression) : expression;
         node.statement = asEmbeddedStatement(statement);
         return node;
     }
diff --git a/tests/baselines/reference/nullishCoalescingOperator12.js b/tests/baselines/reference/nullishCoalescingOperator12.js
@@ -0,0 +1,10 @@
+//// [nullishCoalescingOperator12.ts]
+const obj: { arr: any[] } = { arr: [] };
+for (const i of obj?.arr ?? []) { }
+
+
+//// [nullishCoalescingOperator12.js]
+"use strict";
+var _a, _b;
+const obj = { arr: [] };
+for (const i of (_b = (_a = obj) === null || _a === void 0 ? void 0 : _a.arr, (_b !== null && _b !== void 0 ? _b : []))) { }
diff --git a/tests/baselines/reference/nullishCoalescingOperator12.symbols b/tests/baselines/reference/nullishCoalescingOperator12.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/conformance/expressions/nullishCoalescingOperator/nullishCoalescingOperator12.ts ===
+const obj: { arr: any[] } = { arr: [] };
+>obj : Symbol(obj, Decl(nullishCoalescingOperator12.ts, 0, 5))
+>arr : Symbol(arr, Decl(nullishCoalescingOperator12.ts, 0, 12))
+>arr : Symbol(arr, Decl(nullishCoalescingOperator12.ts, 0, 29))
+
+for (const i of obj?.arr ?? []) { }
+>i : Symbol(i, Decl(nullishCoalescingOperator12.ts, 1, 10))
+>obj?.arr : Symbol(arr, Decl(nullishCoalescingOperator12.ts, 0, 12))
+>obj : Symbol(obj, Decl(nullishCoalescingOperator12.ts, 0, 5))
+>arr : Symbol(arr, Decl(nullishCoalescingOperator12.ts, 0, 12))
+
diff --git a/tests/baselines/reference/nullishCoalescingOperator12.types b/tests/baselines/reference/nullishCoalescingOperator12.types
@@ -0,0 +1,16 @@
+=== tests/cases/conformance/expressions/nullishCoalescingOperator/nullishCoalescingOperator12.ts ===
+const obj: { arr: any[] } = { arr: [] };
+>obj : { arr: any[]; }
+>arr : any[]
+>{ arr: [] } : { arr: never[]; }
+>arr : never[]
+>[] : never[]
+
+for (const i of obj?.arr ?? []) { }
+>i : any
+>obj?.arr ?? [] : any[]
+>obj?.arr : any[]
+>obj : { arr: any[]; }
+>arr : any[]
+>[] : never[]
+
diff --git a/tests/cases/conformance/expressions/nullishCoalescingOperator/nullishCoalescingOperator12.ts b/tests/cases/conformance/expressions/nullishCoalescingOperator/nullishCoalescingOperator12.ts
@@ -0,0 +1,5 @@
+// @strict: true
+// @target: ES2015
+
+const obj: { arr: any[] } = { arr: [] };
+for (const i of obj?.arr ?? []) { }

Original file line number	Diff line number	Diff line change
`@@ -1811,7 +1811,7 @@ namespace ts {`
`1811`	`1811`	`const node = <ForOfStatement>createSynthesizedNode(SyntaxKind.ForOfStatement);`
`1812`	`1812`	`node.awaitModifier = awaitModifier;`
`1813`	`1813`	`node.initializer = initializer;`
`1814`		`- node.expression = expression;`
	`1814`	`+ node.expression = isCommaSequence(expression) ? createParen(expression) : expression;`
`1815`	`1815`	`node.statement = asEmbeddedStatement(statement);`
`1816`	`1816`	`return node;`
`1817`	`1817`	`}`