[es6] implement spread calls

src/harmony-spread.js

+// Copyright 2015 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;

[Dmitry Lomov (no reviews), 2015/04/02 07:53:33]

Why this 'if' is needed?

[caitp (gmail), 2015/04/02 14:18:48]

I wrote it this way to be able to share it with the spread-elements patch, but
I'll worry about that later

+
+  SpreadArguments = function spreadArguments() {

[Dmitry Lomov (no reviews), 2015/04/02 07:53:33]

These functions will be eagerly compiled at snapshot-building time. To avoid
this, please move them outside the SetupSpreadHelper.

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