Allow users of the V8 API to distinguish between unset and undefined HiddenValues

src/objects.cc

 // Copyright 2013 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 4716 matching lines @@
   return hash;
 }
 
 
 Object* JSObject::GetHiddenProperty(Name* key) {
   ASSERT(key->IsUniqueName());
   if (IsJSGlobalProxy()) {
     // For a proxy, use the prototype as target object.
     Object* proxy_parent = GetPrototype();
     // If the proxy is detached, return undefined.
-    if (proxy_parent->IsNull()) return GetHeap()->undefined_value();
+    if (proxy_parent->IsNull()) return GetHeap()->the_hole_value();
     ASSERT(proxy_parent->IsJSGlobalObject());
     return JSObject::cast(proxy_parent)->GetHiddenProperty(key);
   }
   ASSERT(!IsJSGlobalProxy());
   MaybeObject* hidden_lookup =
       GetHiddenPropertiesHashTable(ONLY_RETURN_INLINE_VALUE);
   Object* inline_value = hidden_lookup->ToObjectUnchecked();
 
   if (inline_value->IsSmi()) {
     // Handle inline-stored identity hash.
     if (key == GetHeap()->identity_hash_string()) {
       return inline_value;
     } else {
-      return GetHeap()->undefined_value();
+      return GetHeap()->the_hole_value();
     }
   }
 
-  if (inline_value->IsUndefined()) return GetHeap()->undefined_value();
+  if (inline_value->IsUndefined()) return GetHeap()->the_hole_value();
 
   ObjectHashTable* hashtable = ObjectHashTable::cast(inline_value);
   Object* entry = hashtable->Lookup(key);
-  if (entry->IsTheHole()) return GetHeap()->undefined_value();
   return entry;
 }
 
 
 Handle<Object> JSObject::SetHiddenProperty(Handle<JSObject> obj,
                                            Handle<Name> key,
                                            Handle<Object> value) {
   CALL_HEAP_FUNCTION(obj->GetIsolate(),
                      obj->SetHiddenProperty(*key, *value),
                      Object);
@@ skipping 10985 matching lines @@
   return static_cast<Type*>(type_raw());
 }
 
 
 void PropertyCell::set_type(Type* type, WriteBarrierMode ignored) {
   set_type_raw(type, ignored);
 }
 
 
 } }  // namespace v8::internal