Allow init-less destructing bindings in for/in and for/of

src/statement.js

@@ -364,7 +364,7 @@ pp.parseForIn = function(node, init) {
 
 // Parse a list of variable declarations.
 
-pp.parseVar = function(node, noIn, kind) {
+pp.parseVar = function(node, isFor, kind) {
   node.declarations = []
   node.kind = kind.keyword
   for (;;) {
@@ -372,10 +372,10 @@ pp.parseVar = function(node, noIn, kind) {
     decl.id = this.parseBindingAtom()
     this.checkLVal(decl.id, true)
     if (this.eat(tt.eq)) {
-      decl.init = this.parseMaybeAssign(noIn)
+      decl.init = this.parseMaybeAssign(isFor)
     } else if (kind === tt._const && !(this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of")))) {
       this.unexpected()
-    } else if (decl.id.type != "Identifier") {
+    } else if (decl.id.type != "Identifier" && !(isFor && (this.type === tt._in || this.isContextual("of")))) {
       this.raise(this.lastTokEnd, "Complex binding patterns require an initialization value")
     } else {
       decl.init = null

test/tests-harmony.js

@@ -15522,6 +15522,47 @@ test("[x,,] = 1", {
   ]
 }, {ecmaVersion: 6});
 
+test("for (var [name, value] in obj) {}", {
+  body: [
+    {
+      left: {
+        declarations: [
+          {
+            id: {
+              elements: [
+                {
+                  name: "name",
+                  type: "Identifier"
+                },
+                {
+                  name: "value",
+                  type: "Identifier"
+                }
+              ],
+              type: "ArrayPattern"
+            },
+            init: null,
+            type: "VariableDeclarator"
+          }
+        ],
+        kind: "var",
+        type: "VariableDeclaration"
+      },
+      right: {
+        name: "obj",
+        type: "Identifier"
+      },
+      body: {
+        body: [],
+        type: "BlockStatement"
+      },
+      type: "ForInStatement"
+    }
+  ],
+  sourceType: "script",
+  type: "Program"
+}, {ecmaVersion: 6})
+
 testFail("let [x]", "Complex binding patterns require an initialization value (1:7)", {ecmaVersion: 6})
 testFail("var [x]", "Complex binding patterns require an initialization value (1:7)", {ecmaVersion: 6})
 testFail("var _𖫵 = 11;", "Unexpected character '𖫵' (1:5)", {ecmaVersion: 6});