Upgrade Symbol implementation to match current ES6 behavior.

src/runtime.js

 // Copyright 2006-2008 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 63 matching lines @@
         if (IS_BOOLEAN(y)) return %NumberEquals(%ToNumber(x), %ToNumber(y));
         if (IS_NULL_OR_UNDEFINED(y)) return 1;  // not equal
         y = %ToPrimitive(y, NO_HINT);
       }
     } else if (IS_SYMBOL(x)) {
       while (true) {
         if (IS_SYMBOL(y)) return %_ObjectEquals(x, y) ? 0 : 1;
         if (!IS_SPEC_OBJECT(y)) return 1;  // not equal
         y = %ToPrimitive(y, NO_HINT);
       }
+    } else if (IS_SYMBOL_WRAPPER(x) && IS_SYMBOL_WRAPPER(y)) {
+      return %_ObjectEquals(x, y) ? 0 : 1;
     } else if (IS_BOOLEAN(x)) {
       if (IS_BOOLEAN(y)) return %_ObjectEquals(x, y) ? 0 : 1;
       if (IS_NULL_OR_UNDEFINED(y)) return 1;
       if (IS_NUMBER(y)) return %NumberEquals(%ToNumber(x), y);
       if (IS_STRING(y)) return %NumberEquals(%ToNumber(x), %ToNumber(y));
       if (IS_SYMBOL(y)) return 1;  // not equal
       // y is object.
       x = %ToNumber(x);
       y = %ToPrimitive(y, NO_HINT);
     } else if (IS_NULL_OR_UNDEFINED(x)) {
@@ skipping 401 matching lines @@
    -------------------------------------
 */
 
 // ECMA-262, section 9.1, page 30. Use null/undefined for no hint,
 // (1) for number hint, and (2) for string hint.
 function ToPrimitive(x, hint) {
   // Fast case check.
   if (IS_STRING(x)) return x;
   // Normal behavior.
   if (!IS_SPEC_OBJECT(x)) return x;
-  if (IS_SYMBOL_WRAPPER(x)) return %_ValueOf(x);
+  if (IS_SYMBOL_WRAPPER(x)) throw MakeTypeError('symbol_to_primitive', []);
   if (hint == NO_HINT) hint = (IS_DATE(x)) ? STRING_HINT : NUMBER_HINT;
   return (hint == NUMBER_HINT) ? %DefaultNumber(x) : %DefaultString(x);
 }
 
 
 // ECMA-262, section 9.2, page 30
 function ToBoolean(x) {
   if (IS_BOOLEAN(x)) return x;
   if (IS_STRING(x)) return x.length != 0;
   if (x == null) return false;
@@ skipping 26 matching lines @@
   return (IS_NULL(x)) ? 0 : ToNumber(%DefaultNumber(x));
 }
 
 
 // ECMA-262, section 9.8, page 35.
 function ToString(x) {
   if (IS_STRING(x)) return x;
   if (IS_NUMBER(x)) return %_NumberToString(x);
   if (IS_BOOLEAN(x)) return x ? 'true' : 'false';
   if (IS_UNDEFINED(x)) return 'undefined';
+  if (IS_SYMBOL(x)) throw %MakeTypeError('symbol_to_string', []);
   return (IS_NULL(x)) ? 'null' : %ToString(%DefaultString(x));
 }
 
 function NonStringToString(x) {
   if (IS_NUMBER(x)) return %_NumberToString(x);
   if (IS_BOOLEAN(x)) return x ? 'true' : 'false';
   if (IS_UNDEFINED(x)) return 'undefined';
   return (IS_NULL(x)) ? 'null' : %ToString(%DefaultString(x));
 }
 
 
 // ES6 symbols
 function ToName(x) {
   return IS_SYMBOL(x) ? x : %ToString(x);
 }
 
 
 // ECMA-262, section 9.9, page 36.
 function ToObject(x) {
   if (IS_STRING(x)) return new $String(x);
-  if (IS_SYMBOL(x)) return new $Symbol(x);
+  if (IS_SYMBOL(x)) return new $SymbolWrapper(x);
   if (IS_NUMBER(x)) return new $Number(x);
   if (IS_BOOLEAN(x)) return new $Boolean(x);
   if (IS_NULL_OR_UNDEFINED(x) && !IS_UNDETECTABLE(x)) {
     throw %MakeTypeError('undefined_or_null_to_object', []);
   }
   return x;
 }
 
 
 // ECMA-262, section 9.4, page 34.
@@ skipping 86 matching lines @@
   return i;
 }
 
 
 // NOTE: Setting the prototype for Array must take place as early as
 // possible due to code generation for array literals.  When
 // generating code for a array literal a boilerplate array is created
 // that is cloned when running the code.  It is essential that the
 // boilerplate gets the right prototype.
 %FunctionSetPrototype($Array, new $Array(0));