add interceptors which do not mask existing properties

src/lookup-inl.h

 // Copyright 2014 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.
 
 #ifndef V8_LOOKUP_INL_H_
 #define V8_LOOKUP_INL_H_
 
 #include "src/lookup.h"
 
 namespace v8 {
@@ skipping 13 matching lines @@
       // Always lookup behind the JSGlobalProxy into the JSGlobalObject, even
       // when not checking other hidden prototypes.
       !map->IsJSGlobalProxyMap()) {
     return NULL;
   }
 
   return next;
 }
 
 
-LookupIterator::State LookupIterator::LookupInHolder(Map* map,
-                                                     JSReceiver* holder) {
+LookupIterator::State LookupIterator::LookupInHolder(Map* const map,
+                                                     JSReceiver* const holder) {
   STATIC_ASSERT(INTERCEPTOR == BEFORE_PROPERTY);
   DisallowHeapAllocation no_gc;
+  if (interceptor_state_ == InterceptorState::kProcessNonMasking) {
+    return LookupNonMaskingInterceptorInHolder(map, holder);
+  }
   switch (state_) {
     case NOT_FOUND:
       if (map->IsJSProxyMap()) return JSPROXY;
       if (map->is_access_check_needed() &&
           !isolate_->IsInternallyUsedPropertyName(name_)) {
         return ACCESS_CHECK;
       }
     // Fall through.
     case ACCESS_CHECK:
-      if (check_interceptor() && map->has_named_interceptor()) {
+      if (check_interceptor() && map->has_named_interceptor() &&
+          !SkipInterceptor(JSObject::cast(holder))) {
         return INTERCEPTOR;
       }
     // Fall through.
     case INTERCEPTOR:
       if (map->is_dictionary_map()) {
         NameDictionary* dict = JSObject::cast(holder)->property_dictionary();
         number_ = dict->FindEntry(name_);
         if (number_ == NameDictionary::kNotFound) return NOT_FOUND;
         property_details_ = dict->DetailsAt(number_);
         if (holder->IsGlobalObject()) {
@@ skipping 17 matching lines @@
     case ACCESSOR:
     case DATA:
       return NOT_FOUND;
     case JSPROXY:
     case TRANSITION:
       UNREACHABLE();
   }
   UNREACHABLE();
   return state_;
 }
+
+
+LookupIterator::State LookupIterator::LookupNonMaskingInterceptorInHolder(
+    Map* const map, JSReceiver* const holder) {
+  switch (state_) {
+    case NOT_FOUND:
+      if (map->is_access_check_needed() &&
+          !isolate_->IsInternallyUsedPropertyName(name_)) {

[Toon Verwaest, 2015/03/11 14:09:35]

You don't need these, given that you had to have access to the entire chain to
get here.

+        return ACCESS_CHECK;
+      }
+    // Fall through.
+    case ACCESS_CHECK:
+      if (check_interceptor() && map->has_named_interceptor() &&
+          !SkipInterceptor(JSObject::cast(holder))) {
+        return INTERCEPTOR;
+      }
+    // Fall through.
+    default:
+      return NOT_FOUND;
+  }
+  UNREACHABLE();
+  return state_;
+}
 }
 }  // namespace v8::internal
 
 #endif  // V8_LOOKUP_INL_H_