Correctly check for-in and for-of loop for invalid left-hand side

packages/babel-parser/src/parser/statement.js

@@ -519,21 +519,11 @@ export default class StatementParser extends ExpressionParser {
       this.parseVar(init, true, kind);
       this.finishNode(init, "VariableDeclaration");
 
-      if (this.match(tt._in) || this.isContextual("of")) {
-        if (init.declarations.length === 1) {
-          const declaration = init.declarations[0];
-          const isForInInitializer =
-            kind === "var" &&
-            declaration.init &&
-            declaration.id.type != "ObjectPattern" &&
-            declaration.id.type != "ArrayPattern" &&
-            !this.isContextual("of");
-          if (this.state.strict && isForInInitializer) {
-            this.raise(this.state.start, "for-in initializer in strict mode");
-          } else if (isForInInitializer || !declaration.init) {
-            return this.parseForIn(node, init, awaitAt);
-          }
-        }
+      if (
+        (this.match(tt._in) || this.isContextual("of")) &&
+        init.declarations.length === 1
+      ) {
+        return this.parseForIn(node, init, awaitAt);
       }
       if (awaitAt > -1) {
         this.unexpected(awaitAt);
@@ -938,18 +928,36 @@ export default class StatementParser extends ExpressionParser {
 
   parseForIn(
     node: N.ForInOf,
-    init: N.VariableDeclaration,
+    init: N.VariableDeclaration | N.AssignmentPattern,
     awaitAt: number,
   ): N.ForInOf {
-    const type = this.match(tt._in) ? "ForInStatement" : "ForOfStatement";
-    if (awaitAt > -1) {
-      this.eatContextual("of");
+    const isForIn = this.match(tt._in);
+    this.next();
+
+    if (isForIn) {
+      if (awaitAt > -1) this.unexpected(awaitAt);
     } else {
-      this.next();
-    }
-    if (type === "ForOfStatement") {
       node.await = awaitAt > -1;
     }
+
+    if (
+      init.type === "VariableDeclaration" &&
+      init.declarations[0].init != null &&
+      (!isForIn ||
+        this.state.strict ||
+        init.kind !== "var" ||
+        init.declarations[0].id.type !== "Identifier")
+    ) {
+      this.raise(
+        init.start,
+        `${
+          isForIn ? "for-in" : "for-of"
+        } loop variable declaration may not have an initializer`,
+      );
+    } else if (init.type === "AssignmentPattern") {
+      this.raise(init.start, "Invalid left-hand side in for-loop");
+    }
+
     node.left = init;
     node.right = this.parseExpression();
     this.expect(tt.parenR);
@@ -966,7 +974,7 @@ export default class StatementParser extends ExpressionParser {
     this.scope.exit();
     this.state.labels.pop();
 
-    return this.finishNode(node, type);
+    return this.finishNode(node, isForIn ? "ForInStatement" : "ForOfStatement");
   }
 
   // Parse a list of variable declarations.

packages/babel-parser/test/fixtures/es2015/for-in/bare-initializer/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Invalid left-hand side in for-loop (2:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-in/const-initializer/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:17)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-in/let-initializer/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:15)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-in/strict-initializer/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "for-in initializer in strict mode (2:15)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (2:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-in/var-arraybindingpattern-initializer/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:17)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-in/var-objectbindingpattern-initializer/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:17)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/for-of/bare-initializer/input.js

@@ -0,0 +1,2 @@
+var a;
+for (a = 0 of {});

packages/babel-parser/test/fixtures/es2015/for-of/bare-initializer/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Invalid left-hand side in for-loop (2:5)"
+}

packages/babel-parser/test/fixtures/es2015/uncategorised/109/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:16)"
-}
+  "throws": "for-of loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/uncategorised/235/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:16)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2015/uncategorised/236/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:16)"
-}
+  "throws": "for-of loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/es2018/async-generators/for-await-no-in/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token (2:19)"
-}
+  "throws": "Unexpected token (2:6)"
+}

packages/babel-parser/test/fixtures/esprima/es2015-for-of/invalid-const-init/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:17)"
-}
+  "throws": "for-of loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/esprima/es2015-for-of/invalid-let-init/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:15)"
-}
+  "throws": "for-of loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/esprima/es2015-for-of/invalid-var-init/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:15)"
-}
+  "throws": "for-of loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/esprima/es2015-lexical-declaration/invalid_const_forin/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:17)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/fixtures/esprima/es2015-lexical-declaration/invalid_let_forin/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Unexpected token, expected \";\" (1:15)"
-}
+  "throws": "for-in loop variable declaration may not have an initializer (1:5)"
+}

packages/babel-parser/test/helpers/runFixtureTests.js

@@ -131,6 +131,12 @@ function runTest(test, parseFunction) {
       if (err.message === opts.throws) {
         return;
       } else {
+        /*
+        const fn = path.dirname(test.expect.loc) + "/options.json";
+        test.options = test.options || {};
+        test.options.throws = err.message;
+        fs.writeFileSync(fn, JSON.stringify(test.options, null, "  "));
+        */
         err.message =
           "Expected error message: " +
           opts.throws +

scripts/tests/test262/test262_whitelist.txt

@@ -1,5 +1,3 @@
-annexB/language/statements/for-in/bare-initializer.js(default)
-annexB/language/statements/for-in/bare-initializer.js(strict mode)
 built-ins/RegExp/property-escapes/binary-property-with-value-ASCII_-_F-negated.js(default)
 built-ins/RegExp/property-escapes/binary-property-with-value-ASCII_-_F-negated.js(strict mode)
 built-ins/RegExp/property-escapes/binary-property-with-value-ASCII_-_F.js(default)