Use for-of loops in collection constructors

src/collection.js

 // Copyright 2012 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.
 
 "use strict";
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Array = global.Array;
 
 var $Set = global.Set;
 var $Map = global.Map;
 
 
 // -------------------------------------------------------------------
 // Harmony Set
 
 function SetConstructor(iterable) {
   if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['Set']);
   }
 
-  var iter, adder;
-
-  if (!IS_NULL_OR_UNDEFINED(iterable)) {
-    adder = this.add;
-    if (!IS_SPEC_FUNCTION(adder)) {
-      throw MakeTypeError('property_not_function', ['add', this]);
-    }
-    iter = GetIterator(iterable);
-  }
-
   %_SetInitialize(this);
 
-  if (IS_UNDEFINED(iter)) return;
+  if (!IS_NULL_OR_UNDEFINED(iterable)) {
+    var adder = this.add;
+    if (!IS_SPEC_FUNCTION(adder)) {
+      throw MakeTypeError('property_not_function', ['add', this]);
+    }
 
-  var next, done;
-  while (!(next = iter.next()).done) {
-    if (!IS_SPEC_OBJECT(next)) {
-      throw MakeTypeError('iterator_result_not_an_object', [next]);
+    for (var value of iterable) {
+      %_CallFunction(this, value, adder);
     }
-    %_CallFunction(this, next.value, adder);
   }
 }
 
 
 function SetAddJS(key) {
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.add', this]);
   }
   // Normalize -0 to +0 as required by the spec.
@@ skipping 100 matching lines @@
 
 
 // -------------------------------------------------------------------
 // Harmony Map
 
 function MapConstructor(iterable) {
   if (!%_IsConstructCall()) {
     throw MakeTypeError('constructor_not_function', ['Map']);
   }
 
-  var iter, adder;
-
-  if (!IS_NULL_OR_UNDEFINED(iterable)) {
-    adder = this.set;
-    if (!IS_SPEC_FUNCTION(adder)) {
-      throw MakeTypeError('property_not_function', ['set', this]);
-    }
-    iter = GetIterator(iterable);
-  }
-
   %_MapInitialize(this);
 
-  if (IS_UNDEFINED(iter)) return;
+  if (!IS_NULL_OR_UNDEFINED(iterable)) {
+    var adder = this.set;
+    if (!IS_SPEC_FUNCTION(adder)) {
+      throw MakeTypeError('property_not_function', ['set', this]);
+    }
 
-  var next, done, nextItem;
-  while (!(next = iter.next()).done) {
-    if (!IS_SPEC_OBJECT(next)) {
-      throw MakeTypeError('iterator_result_not_an_object', [next]);
+    for (var nextItem of iterable) {
+      if (!IS_SPEC_OBJECT(nextItem)) {
+        throw MakeTypeError('iterator_value_not_an_object', [nextItem]);
+      }
+      %_CallFunction(this, nextItem[0], nextItem[1], adder);
     }
-    nextItem = next.value;
-    if (!IS_SPEC_OBJECT(nextItem)) {
-      throw MakeTypeError('iterator_value_not_an_object', [nextItem]);
-    }
-    %_CallFunction(this, nextItem[0], nextItem[1], adder);
   }
 }
 
 
 function MapGetJS(key) {
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.get', this]);
   }
   return %_MapGet(this, key);
@@ skipping 98 matching lines @@
     "get", MapGetJS,
     "set", MapSetJS,
     "has", MapHasJS,
     "delete", MapDeleteJS,
     "clear", MapClearJS,
     "forEach", MapForEach
   ));
 }
 
 SetUpMap();