Don't take iterable path in ArrayFrom if items[@@iterator] is null

src/harmony-array.js

 // Copyright 2013 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;
 
@@ skipping 124 matching lines @@
   if (mapping) {
     if (!IS_SPEC_FUNCTION(mapfn)) {
       throw MakeTypeError('called_non_callable', [ mapfn ]);
     } else if (IS_NULL_OR_UNDEFINED(receiver)) {
       receiver = %GetDefaultReceiver(mapfn) || receiver;
     } else if (!IS_SPEC_OBJECT(receiver) && %IsSloppyModeFunction(mapfn)) {
       receiver = ToObject(receiver);
     }
   }
 
-  var iterable = ToIterable(items);
+  var iterable = GetMethod(items, symbolIterator);
   var k;
   var result;
   var mappedValue;
   var nextValue;
 
   if (!IS_UNDEFINED(iterable)) {
     result = %IsConstructor(this) ? new this() : [];
 
+    var iterator = GetIterator(items, iterable);
+
     k = 0;
-    for (nextValue of items) {
-      if (mapping) mappedValue = %_CallFunction(receiver, nextValue, k, mapfn);
-      else mappedValue = nextValue;
+    while (true) {
+      var next = iterator.next();
+
+      if (!IS_OBJECT(next)) {
+        throw MakeTypeError("iterator_result_not_an_object", [next]);
+      }
+
+      if (next.done) {
+        result.length = k;
+        return result;
+      }
+
+      nextValue = next.value;
+      if (mapping) {
+        mappedValue = %_CallFunction(receiver, nextValue, k, mapfn);
+      } else {
+        mappedValue = nextValue;
+      }
       %AddElement(result, k++, mappedValue, NONE);
     }
-
-    result.length = k;
-    return result;
   } else {
     var len = ToLength(items.length);
     result = %IsConstructor(this) ? new this(len) : new $Array(len);
 
     for (k = 0; k < len; ++k) {
       nextValue = items[k];
-      if (mapping) mappedValue = %_CallFunction(receiver, nextValue, k, mapfn);
-      else mappedValue = nextValue;
+      if (mapping) {
+        mappedValue = %_CallFunction(receiver, nextValue, k, mapfn);
+      } else {
+        mappedValue = nextValue;
+      }
       %AddElement(result, k, mappedValue, NONE);
     }
 
     result.length = k;
     return result;
   }
 }
 
 // ES6, draft 05-22-14, section 22.1.2.3
 function ArrayOf() {
@@ skipping 34 matching lines @@
 
   // Set up the non-enumerable functions on the Array prototype object.
   InstallFunctions($Array.prototype, DONT_ENUM, $Array(
     "find", ArrayFind,
     "findIndex", ArrayFindIndex,
     "fill", ArrayFill
   ));
 }
 
 HarmonyArrayExtendArrayPrototype();