Simplify the LookupIterator

src/lookup.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_H_
 #define V8_LOOKUP_H_
 
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects.h"
@@ skipping 16 matching lines @@
     HIDDEN = kHidden | kInterceptor,
     PROTOTYPE_CHAIN_SKIP_INTERCEPTOR = kHidden | kPrototypeChain,
     PROTOTYPE_CHAIN = kHidden | kPrototypeChain | kInterceptor
   };
 
   enum State {
     ACCESS_CHECK,
     INTERCEPTOR,
     JSPROXY,
     NOT_FOUND,
-    UNKNOWN,  // Dictionary-mode holder map without a holder.
     ACCESSOR,
     DATA,
     TRANSITION,
     // Set state_ to BEFORE_PROPERTY to ensure that the next lookup will be a
     // PROPERTY lookup.
     BEFORE_PROPERTY = INTERCEPTOR
   };
 
   LookupIterator(Handle<Object> receiver, Handle<Name> name,
                  Configuration configuration = PROTOTYPE_CHAIN)
       : configuration_(ComputeConfiguration(configuration, name)),
         state_(NOT_FOUND),
         property_details_(NONE, NORMAL, Representation::None()),
         isolate_(name->GetIsolate()),
         name_(name),
-        maybe_receiver_(receiver),
+        receiver_(receiver),
         number_(DescriptorArray::kNotFound) {
-    Handle<JSReceiver> root = GetRoot();
-    holder_map_ = handle(root->map(), isolate_);
-    maybe_holder_ = root;
+    holder_ = GetRoot();
+    holder_map_ = handle(holder_->map(), isolate_);
     Next();
   }
 
   LookupIterator(Handle<Object> receiver, Handle<Name> name,
                  Handle<JSReceiver> holder,
                  Configuration configuration = PROTOTYPE_CHAIN)
       : configuration_(ComputeConfiguration(configuration, name)),
         state_(NOT_FOUND),
         property_details_(NONE, NORMAL, Representation::None()),
         isolate_(name->GetIsolate()),
         name_(name),
         holder_map_(holder->map(), isolate_),
-        maybe_receiver_(receiver),
-        maybe_holder_(holder),
+        receiver_(receiver),
+        holder_(holder),
         number_(DescriptorArray::kNotFound) {
     Next();
   }
 
   Isolate* isolate() const { return isolate_; }
   State state() const { return state_; }
   Handle<Name> name() const { return name_; }
 
   bool IsFound() const { return state_ != NOT_FOUND; }
   void Next();
   void NotFound() {
     has_property_ = false;
     state_ = NOT_FOUND;
   }
 
   Factory* factory() const { return isolate_->factory(); }
-  Handle<Object> GetReceiver() const {
-    return maybe_receiver_.ToHandleChecked();
-  }
+  Handle<Object> GetReceiver() const { return receiver_; }
   Handle<JSObject> GetStoreTarget() const;
   bool is_dictionary_holder() const { return holder_map_->is_dictionary_map(); }
   Handle<Map> transition_map() const {
     DCHECK_EQ(TRANSITION, state_);
     return transition_map_;
   }
   template <class T>
   Handle<T> GetHolder() const {
     DCHECK(IsFound());
-    return Handle<T>::cast(maybe_holder_.ToHandleChecked());
+    return Handle<T>::cast(holder_);
   }
   Handle<JSReceiver> GetRoot() const;
   bool HolderIsReceiverOrHiddenPrototype() const;
 
   /* ACCESS_CHECK */
   bool HasAccess(v8::AccessType access_type) const;
 
   /* PROPERTY */
   void PrepareForDataProperty(Handle<Object> value);
   void PrepareTransitionToDataProperty(Handle<Object> value,
@@ skipping 36 matching lines @@
  private:
   Handle<Map> GetReceiverMap() const;
 
   MUST_USE_RESULT inline JSReceiver* NextHolder(Map* map);
   inline State LookupInHolder(Map* map, JSReceiver* holder);
   Handle<Object> FetchValue() const;
   void ReloadPropertyInformation();
 
   bool IsBootstrapping() const;
 
-  // Methods that fetch data from the holder ensure they always have a holder.
-  // This means the receiver needs to be present as opposed to just the receiver
-  // map. Other objects in the prototype chain are transitively guaranteed to be
-  // present via the receiver map.
-  bool is_guaranteed_to_have_holder() const {
-    return !maybe_receiver_.is_null();
-  }
   bool check_hidden() const { return (configuration_ & kHidden) != 0; }
   bool check_interceptor() const {
     return !IsBootstrapping() && (configuration_ & kInterceptor) != 0;
   }
   bool check_prototype_chain() const {
     return (configuration_ & kPrototypeChain) != 0;
   }
   int descriptor_number() const {
     DCHECK(has_property_);
     DCHECK(!holder_map_->is_dictionary_map());
@@ skipping 17 matching lines @@
   // If configuration_ becomes mutable, update
   // HolderIsReceiverOrHiddenPrototype.
   Configuration configuration_;
   State state_;
   bool has_property_;
   PropertyDetails property_details_;
   Isolate* isolate_;
   Handle<Name> name_;
   Handle<Map> holder_map_;
   Handle<Map> transition_map_;
-  MaybeHandle<Object> maybe_receiver_;
-  MaybeHandle<JSReceiver> maybe_holder_;
+  Handle<Object> receiver_;
+  Handle<JSReceiver> holder_;
 
   int number_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOOKUP_H_