ES6 symbols: enable symbols as weak map keys

src/collection.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 179 matching lines @@
     return new $WeakMap();
   }
 }
 
 
 function WeakMapGet(key) {
   if (!IS_WEAKMAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['WeakMap.prototype.get', this]);
   }
-  if (!IS_SPEC_OBJECT(key)) {
+  if (!(IS_SPEC_OBJECT(key) || IS_SYMBOL(key))) {
     throw %MakeTypeError('invalid_weakmap_key', [this, key]);
   }
   return %WeakMapGet(this, key);
 }
 
 
 function WeakMapSet(key, value) {
   if (!IS_WEAKMAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['WeakMap.prototype.set', this]);
   }
-  if (!IS_SPEC_OBJECT(key)) {
+  if (!(IS_SPEC_OBJECT(key) || IS_SYMBOL(key))) {
     throw %MakeTypeError('invalid_weakmap_key', [this, key]);
   }
   return %WeakMapSet(this, key, value);
 }
 
 
 function WeakMapHas(key) {
   if (!IS_WEAKMAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['WeakMap.prototype.has', this]);
   }
-  if (!IS_SPEC_OBJECT(key)) {
+  if (!(IS_SPEC_OBJECT(key) || IS_SYMBOL(key))) {
     throw %MakeTypeError('invalid_weakmap_key', [this, key]);
   }
   return %WeakMapHas(this, key);
 }
 
 
 function WeakMapDelete(key) {
   if (!IS_WEAKMAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['WeakMap.prototype.delete', this]);
   }
-  if (!IS_SPEC_OBJECT(key)) {
+  if (!(IS_SPEC_OBJECT(key) || IS_SYMBOL(key))) {
     throw %MakeTypeError('invalid_weakmap_key', [this, key]);
   }
   return %WeakMapDelete(this, key);
 }
 
 // -------------------------------------------------------------------
 
 (function () {
   %CheckIsBootstrapping();
 
@@ skipping 31 matching lines @@
   %SetProperty($WeakMap.prototype, "constructor", $WeakMap, DONT_ENUM);
 
   // Set up the non-enumerable functions on the WeakMap prototype object.
   InstallFunctions($WeakMap.prototype, DONT_ENUM, $Array(
     "get", WeakMapGet,
     "set", WeakMapSet,
     "has", WeakMapHas,
     "delete", WeakMapDelete
   ));
 })();