[es6] don't "replace" Object.prototype.toString for --harmony-tostring

src/v8natives.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file relies on the fact that the following declarations have been made
 // in runtime.js:
 // var $Object = global.Object;
 // var $Boolean = global.Boolean;
 // var $Number = global.Number;
 // var $Function = global.Function;
@@ skipping 198 matching lines @@
     "eval", GlobalEval
   ));
 }
 
 SetUpGlobal();
 
 
 // ----------------------------------------------------------------------------
 // Object
 
-var DefaultObjectToString = NoSideEffectsObjectToString;
+var DefaultObjectToString = ObjectToString;
 // ECMA-262 - 15.2.4.2
 function NoSideEffectsObjectToString() {
   if (IS_UNDEFINED(this) && !IS_UNDETECTABLE(this)) return "[object Undefined]";
   if (IS_NULL(this)) return "[object Null]";
   return "[object " + %_ClassOf(TO_OBJECT_INLINE(this)) + "]";
 }
 
 
+function ObjectToString() {
+  if (IS_UNDEFINED(this) && !IS_UNDETECTABLE(this)) return "[object Undefined]";
+  if (IS_NULL(this)) return "[object Null]";
+  var O = TO_OBJECT_INLINE(this);
+  var builtinTag = %_ClassOf(O);
+  var tag;
+
+  // TODO(caitp): cannot wait to get rid of this flag :>
+  if (harmony_tostring) {
+    var tag = O[symbolToStringTag];
+    if (!IS_STRING(tag)) {
+      tag = builtinTag;
+    }
+  } else {
+    tag = builtinTag;
+  }
+
+  return `[object ${tag}]`;
+}
+
+
 // ECMA-262 - 15.2.4.3
 function ObjectToLocaleString() {
   CHECK_OBJECT_COERCIBLE(this, "Object.prototype.toLocaleString");
   return this.toString();
 }
 
 
 // ECMA-262 - 15.2.4.4
 function ObjectValueOf() {
   return TO_OBJECT_INLINE(this);
@@ skipping 1165 matching lines @@
 function SetUpObject() {
   %CheckIsBootstrapping();
 
   %SetNativeFlag($Object);
   %SetCode($Object, ObjectConstructor);
 
   %AddNamedProperty($Object.prototype, "constructor", $Object, DONT_ENUM);
 
   // Set up non-enumerable functions on the Object.prototype object.
   InstallFunctions($Object.prototype, DONT_ENUM, $Array(
-    "toString", NoSideEffectsObjectToString,
+    "toString", ObjectToString,
     "toLocaleString", ObjectToLocaleString,
     "valueOf", ObjectValueOf,
     "hasOwnProperty", ObjectHasOwnProperty,
     "isPrototypeOf", ObjectIsPrototypeOf,
     "propertyIsEnumerable", ObjectPropertyIsEnumerable,
     "__defineGetter__", ObjectDefineGetter,
     "__lookupGetter__", ObjectLookupGetter,
     "__defineSetter__", ObjectDefineSetter,
     "__lookupSetter__", ObjectLookupSetter
   ));
@@ skipping 469 matching lines @@
   }
   if (!IS_SPEC_FUNCTION(method)) {
     throw MakeTypeError('not_iterable', [obj]);
   }
   var iterator = %_CallFunction(obj, method);
   if (!IS_SPEC_OBJECT(iterator)) {
     throw MakeTypeError('not_an_iterator', [iterator]);
   }
   return iterator;
 }