Make instanceof and Object.getPrototypeOf work for proxies, plus a few other tweaks.

src/v8natives.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 381 matching lines @@
     desc.setSet(set);
   }
 
   if (IsInconsistentDescriptor(desc)) {
     throw MakeTypeError("value_and_accessor", [obj]);
   }
   return desc;
 }
 
 
+// For Harmony proxies.
+function ToCompletePropertyDescriptor(obj) {
+  var desc = ToPropertyDescriptor(obj)
+  if (IsGenericDescriptor(desc) || IsDataDescriptor(desc)) {
+    if (!("value" in desc)) desc.value = undefined

[Kevin Millikin (Chromium), 2011/06/01 15:14:31]

undefined ==> void 0

+    if (!("writable" in desc)) desc.writable = false
+  } else {
+    // Is accessor descriptor.
+    if (!("get" in desc)) desc.get = undefined
+    if (!("set" in desc)) desc.set = undefined
+  }
+  if (!("enumerable" in desc)) desc.enumerable = false
+  if (!("configurable" in desc)) desc.configurable = false
+  return desc
+}
+
+
 function PropertyDescriptor() {
   // Initialize here so they are all in-object and have the same map.
   // Default values from ES5 8.6.1.
   this.value_ = void 0;
   this.hasValue_ = false;
   this.writable_ = false;
   this.hasWritable_ = false;
   this.enumerable_ = false;
   this.hasEnumerable_ = false;
   this.configurable_ = false;
@@ skipping 128 matching lines @@
   }
   desc.setEnumerable(desc_array[ENUMERABLE_INDEX]);
   desc.setConfigurable(desc_array[CONFIGURABLE_INDEX]);
 
   return desc;
 }
 
 
 // ES5 section 8.12.2.
 function GetProperty(obj, p) {
+  if (%IsJSProxy(obj)) {
+    var handler = %GetHandler(obj)
+    var getProperty = handler.getPropertyDescriptor
+    if (IS_UNDEFINED(getProperty))
+      throw MakeTypeError("handler_trap_missing",
+                          [handler, "getPropertyDescriptor"])
+    var descriptor = getProperty.call(handler, p)
+    if (IS_UNDEFINED(descriptor)) return descriptor
+    var desc = ToCompletePropertyDescriptor(descriptor)
+    if (!desc.configurable)
+      throw MakeTypeError("proxy_prop_not_configurable",
+                          [handler, "getPropertyDescriptor", p, descriptor])
+    return desc
+  }
   var prop = GetOwnProperty(obj);
   if (!IS_UNDEFINED(prop)) return prop;
-  var proto = obj.__proto__;
+  var proto = %GetPrototype(obj);
   if (IS_NULL(proto)) return void 0;
   return GetProperty(proto, p);
 }
 
 
 // ES5 section 8.12.6
 function HasProperty(obj, p) {
+  if (%IsJSProxy(obj)) {
+    var handler = %GetHandler(obj)
+    var has = handler.has
+    if (IS_UNDEFINED(has)) has = DerivedHasTrap
+    return ToBoolean(has.call(handler, obj, p))
+  }
   var desc = GetProperty(obj, p);
   return IS_UNDEFINED(desc) ? false : true;
 }
 
 
 // ES5 section 8.12.1.
 function GetOwnProperty(obj, p) {
   // GetOwnProperty returns an array indexed by the constants
   // defined in macros.py.
   // If p is not a property on obj undefined is returned.
@@ skipping 168 matching lines @@
     }
   }
   return true;
 }
 
 
 // ES5 section 15.2.3.2.
 function ObjectGetPrototypeOf(obj) {
   if (!IS_SPEC_OBJECT(obj))
     throw MakeTypeError("obj_ctor_property_non_object", ["getPrototypeOf"]);
-  return obj.__proto__;
+  return %GetPrototype(obj);
 }
 
 
 // ES5 section 15.2.3.3
 function ObjectGetOwnPropertyDescriptor(obj, p) {
   if (!IS_SPEC_OBJECT(obj))
     throw MakeTypeError("obj_ctor_property_non_object", ["getOwnPropertyDescriptor"]);
   var desc = GetOwnProperty(obj, p);
   return FromPropertyDescriptor(desc);
 }
@@ skipping 555 matching lines @@
 // ----------------------------------------------------------------------------
 
 function SetupFunction() {
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetupFunction();