ES6 symbols: Allow symbols as property names

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 328 matching lines @@
 
 
 
 /* -----------------------------
    - - -   H e l p e r s   - - -
    -----------------------------
 */
 
 // ECMA-262, section 11.4.1, page 46.
 function DELETE(key, strict) {
-  return %DeleteProperty(%ToObject(this), %ToString(key), strict);
+  return %DeleteProperty(%ToObject(this), %ToName(key), strict);
 }
 
 
 // ECMA-262, section 11.8.7, page 54.
 function IN(x) {
   if (!IS_SPEC_OBJECT(x)) {
     throw %MakeTypeError('invalid_in_operator_use', [this, x]);
   }
   return %_IsNonNegativeSmi(this) ?
-    %HasElement(x, this) : %HasProperty(x, %ToString(this));
+    %HasElement(x, this) : %HasProperty(x, %ToName(this));
 }
 
 
 // ECMA-262, section 11.8.6, page 54. To make the implementation more
 // efficient, the return value should be zero if the 'this' is an
 // instance of F, and non-zero if not. This makes it possible to avoid
 // an expensive ToBoolean conversion in the generated code.
 function INSTANCE_OF(F) {
   var V = this;
   if (!IS_SPEC_FUNCTION(F)) {
@@ skipping 19 matching lines @@
 
   // Return whether or not O is in the prototype chain of V.
   return %IsInPrototypeChain(O, V) ? 0 : 1;
 }
 
 
 // Filter a given key against an object by checking if the object
 // has a property with the given key; return the key as a string if
 // it has. Otherwise returns 0 (smi). Used in for-in statements.
 function FILTER_KEY(key) {
-  var string = %ToString(key);
+  var string = %ToName(key);
   if (%HasProperty(this, string)) return string;
   return 0;
 }
 
 
 function CALL_NON_FUNCTION() {
   var delegate = %GetFunctionDelegate(this);
   if (!IS_FUNCTION(delegate)) {
     throw %MakeTypeError('called_non_callable', [typeof this]);
   }
@@ skipping 146 matching lines @@
 }
 
 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_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('null_to_object', []);
   }
   return x;
 }
@@ skipping 82 matching lines @@
   throw %MakeTypeError('cannot_convert_to_primitive', []);
 }
 
 
 // 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));