Upgrade Symbol implementation to match current ES6 behavior.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 2a949ae8d1df89a0794780b25e66706698a34b40..a1673cbf216710193405d45dd809a03bc23b8b94 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -80,6 +80,8 @@ function EQUALS(y) {
         if (!IS_SPEC_OBJECT(y)) return 1;  // not equal
         y = %ToPrimitive(y, NO_HINT);
       }
+    } else if (IS_SYMBOL_WRAPPER(x) && IS_SYMBOL_WRAPPER(y)) {

[rossberg, 2014/02/14 10:55:30]

This should be subsumed by the default case below.

[sof, 2014/02/14 14:20:02]

Yes. I noticed we were unnecessarily calling ToPrimitive() in two cases
involving symbol values, so added explicit checks. (This matters now that Symbol
wrappers throw on ToPrimitive().)

The spec hasn't changed here, so simply not correct as-was.

+      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;
@@ -501,7 +503,7 @@ function ToPrimitive(x, hint) {
   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);
 }
@@ -548,6 +550,7 @@ function ToString(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));
 }
 
@@ -555,6 +558,7 @@ function NonStringToString(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));
 }
 
@@ -568,9 +572,9 @@ function ToName(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_NUMBER(x)) return new $Number(x);
   if (IS_BOOLEAN(x)) return new $Boolean(x);
+  if (IS_SYMBOL(x)) return %NewSymbolWrapper(x);
   if (IS_NULL_OR_UNDEFINED(x) && !IS_UNDETECTABLE(x)) {
     throw %MakeTypeError('undefined_or_null_to_object', []);
   }