[parser] Fix bug in for-of desugaring.

test/mjsunit/es6/iterator-close.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 function* g() { yield 42; return 88 };
 
 
 // Return method is "undefined".
 {
@@ skipping 948 matching lines @@
   log = [];
   assertThrowsEquals(() => {
     (([x]) => x)(g())
   }, 23);
   assertEquals([[]], log);
 }
 
 
 // Next method throws.
 {
+  let closed = false;
   g.prototype.next = () => { throw 666; };
-  g.prototype.return = () => { assertUnreachable() };
+  g.prototype.return = () => { closed = true; };
 
 
   assertThrowsEquals(() => {
     for (var x of g()) {}
   }, 666);
 
   assertThrowsEquals(() => {
     for (let x of g()) {}
   }, 666);
 
@@ skipping 37 matching lines @@
     const [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     (([...x]) => x)(g());
   }, 666);
+
+
+  assertFalse(closed);
 }
 
 
 // Value throws.
 {
+  let closed = false;
   g.prototype.next = () => ({get value() {throw 666}});
-  g.prototype.return = () => { assertUnreachable() };
+  g.prototype.return = () => { closed = true; };
 
 
   assertThrowsEquals(() => {
     for (var x of g()) {}
   }, 666);
 
   assertThrowsEquals(() => {
     for (let x of g()) {}
   }, 666);
 
@@ skipping 37 matching lines @@
     const [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     (([...x]) => x)(g());
   }, 666);
+
+
+  assertFalse(closed);
 }
 
 
 // Done throws.
 {
+  let closed = false;
   g.prototype.next = () => ({get done() {throw 666}});
-  g.prototype.return = () => { assertUnreachable() };
+  g.prototype.return = () => { closed = true; };
 
 
   assertThrowsEquals(() => {
     for (var x of g()) {}
   }, 666);
 
   assertThrowsEquals(() => {
     for (let x of g()) {}
   }, 666);
 
@@ skipping 37 matching lines @@
     const [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     [...x] = g();
   }, 666);
 
   assertThrowsEquals(() => {
     (([...x]) => x)(g());
   }, 666);
+
+
+  assertFalse(closed);
 }
 
 
 // Nested loops.
 {
   function* g1() { yield 1; yield 2; throw 3; }
   function* g2() { yield -1; yield -2; throw -3; }
 
   assertDoesNotThrow(() => {
     for (let x of g1()) {
@@ skipping 195 matching lines @@
   })());
 
   assertEquals(42, (() => {
     for (let x of g()) return 42;
   })());
 
   assertThrowsEquals(() => {
     for (let x of g()) throw 42;
   }, 42);
 }