[es6] support rest parameters in arrow functions (alternative)

test/mjsunit/harmony/rest-params.js

 // Copyright 2014 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.
 
-// Flags: --harmony-rest-parameters
+// Flags: --harmony-rest-parameters --harmony-arrow-functions
 
 (function testRestIndex() {
   assertEquals(5, (function(...args) { return args.length; })(1,2,3,4,5));
   assertEquals(4, (function(a, ...args) { return args.length; })(1,2,3,4,5));
   assertEquals(3, (function(a, b, ...args) { return args.length; })(1,2,3,4,5));
   assertEquals(2, (function(a, b, c, ...args) {
                       return args.length; })(1,2,3,4,5));
   assertEquals(1, (function(a, b, c, d, ...args) {
                       return args.length; })(1,2,3,4,5));
   assertEquals(0, (function(a, b, c, d, e, ...args) {
@@ skipping 143 matching lines @@
   function sloppyF(a, ...rest) {
     arguments[0] = 1;
     assertEquals(3, a);
     arguments[1] = 2;
     assertArrayEquals([4, 5], rest);
   }
   sloppyF(3, 4, 5);
 })();
 
 
-/* TODO(caitp): support arrow functions (blocked on spread operator support)
 (function testRestParamsArrowFunctions() {
   "use strict";
 
   var fn = (a, b, ...c) => c;
   assertEquals([], fn());
   assertEquals([], fn(1, 2));
   assertEquals([3], fn(1, 2, 3));
   assertEquals([3, 4], fn(1, 2, 3, 4));
   assertEquals([3, 4, 5], fn(1, 2, 3, 4, 5));
   assertThrows("var x = ...y => y;", SyntaxError);
   assertEquals([], ((...args) => args)());
   assertEquals([1,2,3], ((...args) => args)(1,2,3));
-})();*/
+})();