[es6] implement spread calls

src/harmony-spread.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';
+
+var SpreadArguments;
+var SpreadIterable;
+
+
+function SetupSpreadHelpers() {
+  %CheckIsBootstrapping();
+
+  if (SpreadArguments) return;
+
+  SpreadArguments = function spreadArguments() {
+    var count = %_ArgumentsLength();
+    var args = new InternalArray();
+
+    for (var i = 0; i < count; ++i) {
+      var array = %_Arguments(i);
+      var length = array.length;
+      for (var j = 0; j < length; ++j) {
+        args.push(array[j]);
+      }
+    }
+
+    return args;
+  }
+
+  SpreadIterable = function spreadIterable(collection) {
+    if (IS_NULL_OR_UNDEFINED(collection)) {

[arv (Not doing code reviews), 2015/03/30 22:19:49]

Isn't this is already tested by for-of?

[caitp (gmail), 2015/03/30 22:38:12]

at the time I wrote it, it was a reference error trying to get Symbol.iterator
from null/undefined --- it might be a better error now

+      throw MakeTypeError("not_iterable", [collection]);
+    }
+
+    var args = new InternalArray();
+    for (var value of collection) {
+      args.push(value);
+    }
+    return args;
+  }
+}
+
+SetupSpreadHelpers();