Spec adjustments for well-known symbols

src/symbol.js

 // Copyright 2013 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 47 matching lines @@
   if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
     throw MakeTypeError(
       'incompatible_method_receiver', ["Symbol.prototype.valueOf", this]);
   }
   return %_ValueOf(this);
 }
 
 
 function GetSymbolRegistry() {
   var registry = %SymbolRegistry();
-  if (!('internal' in registry)) {
+  if (IS_UNDEFINED(registry.internal)) {
     registry.internal = {__proto__: null};
     registry.for = {__proto__: null};
     registry.keyFor = {__proto__: null};
   }
   return registry;
 }
 
 
 function InternalSymbol(key) {
   var registry = GetSymbolRegistry();
-  if (!(key in registry.internal)) {
+  if (IS_UNDEFINED(registry.internal[key])) {
     registry.internal[key] = %CreateSymbol(key);
   }
   return registry.internal[key];
 }
 
 
 function SymbolFor(key) {
   key = TO_STRING_INLINE(key);
   var registry = GetSymbolRegistry();
-  if (!(key in registry.for)) {
+  if (IS_UNDEFINED(registry.for[key])) {
     var symbol = %CreateSymbol(key);
     registry.for[key] = symbol;
     registry.keyFor[symbol] = key;
   }
   return registry.for[key];
 }
 
 
 function SymbolKeyFor(symbol) {
   if (!IS_SYMBOL(symbol)) {
@@ skipping 11 matching lines @@
   }
 
   // TODO(arv): Proxies use a shared trap for String and Symbol keys.
 
   return ObjectGetOwnPropertyKeys(obj, true);
 }
 
 
 //-------------------------------------------------------------------
 
-var symbolCreate = InternalSymbol("@@create");
-var symbolHasInstance = InternalSymbol("@@hasInstance");
-var symbolIsConcatSpreadable = InternalSymbol("@@isConcatSpreadable");
-var symbolIsRegExp = InternalSymbol("@@isRegExp");
-var symbolIterator = InternalSymbol("@@iterator");
-var symbolToStringTag = InternalSymbol("@@toStringTag");
-var symbolUnscopables = InternalSymbol("@@unscopables");
+var symbolCreate = InternalSymbol("Symbol.create");
+var symbolHasInstance = InternalSymbol("Symbol.hasInstance");
+var symbolIsConcatSpreadable = InternalSymbol("Symbol.isConcatSpreadable");
+var symbolIsRegExp = InternalSymbol("Symbol.isRegExp");
+var symbolIterator = InternalSymbol("Symbol.iterator");
+var symbolToStringTag = InternalSymbol("Symbol.toStringTag");
+var symbolUnscopables = InternalSymbol("Symbol.unscopables");
 
 
 //-------------------------------------------------------------------
 
 function SetUpSymbol() {
   %CheckIsBootstrapping();
 
   %SetCode($Symbol, SymbolConstructor);
   %FunctionSetPrototype($Symbol, new $Object());
 
-  %SetProperty($Symbol, "create", symbolCreate, DONT_ENUM);
-  %SetProperty($Symbol, "hasInstance", symbolHasInstance, DONT_ENUM);
-  %SetProperty($Symbol, "isConcatSpreadable",
-      symbolIsConcatSpreadable, DONT_ENUM);
-  %SetProperty($Symbol, "isRegExp", symbolIsRegExp, DONT_ENUM);
-  %SetProperty($Symbol, "iterator", symbolIterator, DONT_ENUM);
-  %SetProperty($Symbol, "toStringTag", symbolToStringTag, DONT_ENUM);
-  %SetProperty($Symbol, "unscopables", symbolUnscopables, DONT_ENUM);
+  InstallConstants($Symbol, $Array(
+    "create", symbolCreate,
+    "hasInstance", symbolHasInstance,
+    "isConcatSpreadable", symbolIsConcatSpreadable,
+    "isRegExp", symbolIsRegExp,
+    "iterator", symbolIterator,
+    "toStringTag", symbolToStringTag,
+    "unscopables", symbolUnscopables
+  ));
   InstallFunctions($Symbol, DONT_ENUM, $Array(
     "for", SymbolFor,
     "keyFor", SymbolKeyFor
   ));
 
   %SetProperty($Symbol.prototype, "constructor", $Symbol, DONT_ENUM);
   InstallFunctions($Symbol.prototype, DONT_ENUM, $Array(
     "toString", SymbolToString,
     "valueOf", SymbolValueOf
   ));
 }
 
 SetUpSymbol();
 
 
 function ExtendObject() {
   %CheckIsBootstrapping();
 
   InstallFunctions($Object, DONT_ENUM, $Array(
     "getOwnPropertySymbols", ObjectGetOwnPropertySymbols
   ));
 }
 
 ExtendObject();