Revert "Track field types."

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index dae7d51b6a1195117f87dcc108944324a1701cc7..aaa03203ae444987ec954edb1d4e19012e0791c5 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -73,23 +73,6 @@ MUST_USE_RESULT static MaybeObject* CreateJSValue(JSFunction* constructor,
 }
 
 
-Handle<HeapType> Object::OptimalType(Isolate* isolate,
-                                     Representation representation) {
-  if (!FLAG_track_field_types) return HeapType::Any(isolate);
-  if (representation.IsNone()) return HeapType::None(isolate);
-  if (representation.IsHeapObject() && IsHeapObject()) {
-    // We can track only JavaScript objects with stable maps.
-    Handle<Map> map(HeapObject::cast(this)->map(), isolate);
-    if (map->is_stable() &&
-        map->instance_type() >= FIRST_NONCALLABLE_SPEC_OBJECT_TYPE &&
-        map->instance_type() <= LAST_NONCALLABLE_SPEC_OBJECT_TYPE) {
-      return HeapType::Class(map, isolate);
-    }
-  }
-  return HeapType::Any(isolate);
-}
-
-
 MaybeObject* Object::ToObject(Context* native_context) {
   if (IsNumber()) {
     return CreateJSValue(native_context->number_function(), this);
@@ -1464,9 +1447,7 @@ void Map::PrintGeneralization(FILE* file,
                               int descriptors,
                               bool constant_to_field,
                               Representation old_representation,
-                              Representation new_representation,
-                              HeapType* old_field_type,
-                              HeapType* new_field_type) {
+                              Representation new_representation) {
   PrintF(file, "[generalizing ");
   constructor_name()->PrintOn(file);
   PrintF(file, "] ");
@@ -1476,19 +1457,13 @@ void Map::PrintGeneralization(FILE* file,
   } else {
     PrintF(file, "{symbol %p}", static_cast<void*>(name));
   }
-  PrintF(file, ":");
   if (constant_to_field) {
-    PrintF(file, "c");
+    PrintF(file, ":c->f");
   } else {
-    PrintF(file, "%s", old_representation.Mnemonic());
-    PrintF(file, "{");
-    old_field_type->TypePrint(file, HeapType::SEMANTIC_DIM);
-    PrintF(file, "}");
-  }
-  PrintF(file, "->%s", new_representation.Mnemonic());
-  PrintF(file, "{");
-  new_field_type->TypePrint(file, HeapType::SEMANTIC_DIM);
-  PrintF(file, "}");
+    PrintF(file, ":%s->%s",
+           old_representation.Mnemonic(),
+           new_representation.Mnemonic());
+  }
   PrintF(file, " (");
   if (strlen(reason) > 0) {
     PrintF(file, "%s", reason);
@@ -1880,12 +1855,10 @@ static Handle<Object> NewStorageFor(Isolate* isolate,
 static Handle<Map> CopyAddFieldDescriptor(Handle<Map> map,
                                           Handle<Name> name,
                                           int index,
-                                          Handle<HeapType> field_type,
                                           PropertyAttributes attributes,
                                           Representation representation,
                                           TransitionFlag flag) {
-  FieldDescriptor new_field_desc(name, index, field_type,
-                                 attributes, representation);
+  FieldDescriptor new_field_desc(name, index, attributes, representation);
   Handle<Map> new_map = Map::CopyAddDescriptor(map, &new_field_desc, flag);
   int unused_property_fields = map->unused_property_fields() - 1;
   if (unused_property_fields < 0) {
@@ -1922,14 +1895,11 @@ void JSObject::AddFastProperty(Handle<JSObject> object,
   // Compute the new index for new field.
   int index = object->map()->NextFreePropertyIndex();
 
-  // Compute the optimal representation for the new field.
+  // Allocate new instance descriptors with (name, index) added
   if (object->IsJSContextExtensionObject()) value_type = FORCE_TAGGED;
   Representation representation = value->OptimalRepresentation(value_type);
-
   Handle<Map> new_map = CopyAddFieldDescriptor(
-      handle(object->map()), name, index,
-      value->OptimalType(isolate, representation),
-      attributes, representation, flag);
+      handle(object->map()), name, index, attributes, representation, flag);
 
   JSObject::MigrateToMap(object, new_map);
 
@@ -2375,11 +2345,9 @@ void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map) {
 void JSObject::GeneralizeFieldRepresentation(Handle<JSObject> object,
                                              int modify_index,
                                              Representation new_representation,
-                                             Handle<HeapType> new_field_type,
                                              StoreMode store_mode) {
   Handle<Map> new_map = Map::GeneralizeRepresentation(
-      handle(object->map()), modify_index, new_representation,
-      new_field_type, store_mode);
+      handle(object->map()), modify_index, new_representation, store_mode);
   if (object->map() == *new_map) return;
   return MigrateToMap(object, new_map);
 }
@@ -2400,22 +2368,16 @@ Handle<Map> Map::CopyGeneralizeAllRepresentations(Handle<Map> map,
                                                   StoreMode store_mode,
                                                   PropertyAttributes attributes,
                                                   const char* reason) {
-  Isolate* isolate = map->GetIsolate();
   Handle<Map> new_map = Copy(map);
 
   DescriptorArray* descriptors = new_map->instance_descriptors();
-  int length = descriptors->number_of_descriptors();
-  for (int i = 0; i < length; i++) {
-    descriptors->SetRepresentation(i, Representation::Tagged());
-    if (descriptors->GetDetails(i).type() == FIELD) {
-      descriptors->SetValue(i, HeapType::Any());
-    }
-  }
+  descriptors->InitializeRepresentations(Representation::Tagged());
 
   // Unless the instance is being migrated, ensure that modify_index is a field.
   PropertyDetails details = descriptors->GetDetails(modify_index);
   if (store_mode == FORCE_FIELD && details.type() != FIELD) {
-    FieldDescriptor d(handle(descriptors->GetKey(modify_index), isolate),
+    FieldDescriptor d(handle(descriptors->GetKey(modify_index),
+                             map->GetIsolate()),
                       new_map->NumberOfFields(),
                       attributes,
                       Representation::Tagged());
@@ -2428,15 +2390,11 @@ Handle<Map> Map::CopyGeneralizeAllRepresentations(Handle<Map> map,
   }
 
   if (FLAG_trace_generalization) {
-    HeapType* field_type = (details.type() == FIELD)
-        ? map->instance_descriptors()->GetFieldType(modify_index)
-        : NULL;
     map->PrintGeneralization(stdout, reason, modify_index,
                         new_map->NumberOfOwnDescriptors(),
                         new_map->NumberOfOwnDescriptors(),
                         details.type() == CONSTANT && store_mode == FORCE_FIELD,
-                        details.representation(), Representation::Tagged(),
-                        field_type, HeapType::Any());
+                        Representation::Tagged(), Representation::Tagged());
   }
   return new_map;
 }
@@ -2501,8 +2459,6 @@ Map* Map::FindRootMap() {
 Map* Map::FindUpdatedMap(int verbatim,
                          int length,
                          DescriptorArray* descriptors) {
-  DisallowHeapAllocation no_allocation;
-
   // This can only be called on roots of transition trees.
   ASSERT(GetBackPointer()->IsUndefined());
 
@@ -2537,8 +2493,6 @@ Map* Map::FindUpdatedMap(int verbatim,
 Map* Map::FindLastMatchMap(int verbatim,
                            int length,
                            DescriptorArray* descriptors) {
-  DisallowHeapAllocation no_allocation;
-
   // This can only be called on roots of transition trees.
   ASSERT(GetBackPointer()->IsUndefined());
 
@@ -2554,17 +2508,13 @@ Map* Map::FindLastMatchMap(int verbatim,
     Map* next = transitions->GetTarget(transition);
     DescriptorArray* next_descriptors = next->instance_descriptors();
 
+    if (next_descriptors->GetValue(i) != descriptors->GetValue(i)) break;
+
     PropertyDetails details = descriptors->GetDetails(i);
     PropertyDetails next_details = next_descriptors->GetDetails(i);
     if (details.type() != next_details.type()) break;
     if (details.attributes() != next_details.attributes()) break;
     if (!details.representation().Equals(next_details.representation())) break;
-    if (next_details.type() == FIELD) {
-      if (!descriptors->GetFieldType(i)->NowIs(
-              next_descriptors->GetFieldType(i))) break;
-    } else {
-      if (descriptors->GetValue(i) != next_descriptors->GetValue(i)) break;
-    }
 
     current = next;
   }
@@ -2572,87 +2522,6 @@ Map* Map::FindLastMatchMap(int verbatim,
 }
 
 
-Map* Map::FindFieldOwner(int descriptor) {
-  DisallowHeapAllocation no_allocation;
-  ASSERT_EQ(FIELD, instance_descriptors()->GetDetails(descriptor).type());
-  Map* result = this;
-  while (true) {
-    Object* back = result->GetBackPointer();
-    if (back->IsUndefined()) break;
-    Map* parent = Map::cast(back);
-    if (parent->NumberOfOwnDescriptors() <= descriptor) break;
-    result = parent;
-  }
-  return result;
-}
-
-
-void Map::UpdateDescriptor(int descriptor_number, Descriptor* desc) {
-  DisallowHeapAllocation no_allocation;
-  if (HasTransitionArray()) {
-    TransitionArray* transitions = this->transitions();
-    for (int i = 0; i < transitions->number_of_transitions(); ++i) {
-      transitions->GetTarget(i)->UpdateDescriptor(descriptor_number, desc);
-    }
-  }
-  instance_descriptors()->Replace(descriptor_number, desc);;
-}
-
-
-// static
-Handle<HeapType> Map::GeneralizeFieldType(Handle<HeapType> old_field_type,
-                                          Handle<HeapType> new_field_type,
-                                          Isolate* isolate) {
-  if (new_field_type->NowIs(old_field_type)) return old_field_type;
-  if (old_field_type->NowIs(new_field_type)) return new_field_type;
-  return HeapType::Any(isolate);
-}
-
-
-// static
-void Map::GeneralizeFieldType(Handle<Map> map,
-                              int modify_index,
-                              Handle<HeapType> new_field_type) {
-  Isolate* isolate = map->GetIsolate();
-  Handle<Map> field_owner(map->FindFieldOwner(modify_index), isolate);
-  Handle<DescriptorArray> descriptors(
-      field_owner->instance_descriptors(), isolate);
-
-  // Check if we actually need to generalize the field type at all.
-  Handle<HeapType> old_field_type(
-      descriptors->GetFieldType(modify_index), isolate);
-  if (new_field_type->NowIs(old_field_type)) {
-    ASSERT(Map::GeneralizeFieldType(old_field_type,
-                                    new_field_type,
-                                    isolate)->NowIs(old_field_type));
-    return;
-  }
-
-  // Determine the generalized new field type.
-  new_field_type = Map::GeneralizeFieldType(
-      old_field_type, new_field_type, isolate);
-
-  PropertyDetails details = descriptors->GetDetails(modify_index);
-  FieldDescriptor d(handle(descriptors->GetKey(modify_index), isolate),
-                    descriptors->GetFieldIndex(modify_index),
-                    new_field_type,
-                    details.attributes(),
-                    details.representation());
-  field_owner->UpdateDescriptor(modify_index, &d);
-  field_owner->dependent_code()->DeoptimizeDependentCodeGroup(
-      isolate, DependentCode::kFieldTypeGroup);
-
-  if (FLAG_trace_generalization) {
-    map->PrintGeneralization(
-        stdout, "field type generalization",
-        modify_index, map->NumberOfOwnDescriptors(),
-        map->NumberOfOwnDescriptors(), false,
-        details.representation(), details.representation(),
-        *old_field_type, *new_field_type);
-  }
-}
-
-
 // Generalize the representation of the descriptor at |modify_index|.
 // This method rewrites the transition tree to reflect the new change. To avoid
 // high degrees over polymorphism, and to stabilize quickly, on every rewrite
@@ -2674,7 +2543,6 @@ void Map::GeneralizeFieldType(Handle<Map> map,
 Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
                                           int modify_index,
                                           Representation new_representation,
-                                          Handle<HeapType> new_field_type,
                                           StoreMode store_mode) {
   Handle<DescriptorArray> old_descriptors(old_map->instance_descriptors());
   PropertyDetails old_details = old_descriptors->GetDetails(modify_index);
@@ -2687,28 +2555,11 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
   if (old_representation.IsNone() &&
       !new_representation.IsNone() &&
       !new_representation.IsDouble()) {
-    ASSERT(old_details.type() == FIELD);
-    ASSERT(old_descriptors->GetFieldType(modify_index)->NowIs(
-            HeapType::None()));
-    if (FLAG_trace_generalization) {
-      old_map->PrintGeneralization(
-          stdout, "uninitialized field",
-          modify_index, old_map->NumberOfOwnDescriptors(),
-          old_map->NumberOfOwnDescriptors(), false,
-          old_representation, new_representation,
-          old_descriptors->GetFieldType(modify_index), *new_field_type);
-    }
     old_descriptors->SetRepresentation(modify_index, new_representation);
-    old_descriptors->SetValue(modify_index, *new_field_type);
-    return old_map;
-  }
-
-  if (new_representation.Equals(old_representation) &&
-      old_details.type() == FIELD) {
-    Map::GeneralizeFieldType(old_map, modify_index, new_field_type);
     return old_map;
   }
 
+  int descriptors = old_map->NumberOfOwnDescriptors();
   Handle<Map> root_map(old_map->FindRootMap());
 
   // Check the state of the root map.
@@ -2724,7 +2575,6 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
         old_details.attributes(), "root modification");
   }
 
-  int descriptors = old_map->NumberOfOwnDescriptors();
   Map* raw_updated = root_map->FindUpdatedMap(
       verbatim, descriptors, *old_descriptors);
   if (raw_updated == NULL) {
@@ -2754,7 +2604,6 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
   ASSERT(store_mode == ALLOW_AS_CONSTANT ||
          new_descriptors->GetDetails(modify_index).type() == FIELD);
 
-  Isolate* isolate = new_descriptors->GetIsolate();
   old_representation =
       new_descriptors->GetDetails(modify_index).representation();
   Representation updated_representation =
@@ -2762,13 +2611,6 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
   if (!updated_representation.Equals(old_representation)) {
     new_descriptors->SetRepresentation(modify_index, updated_representation);
   }
-  if (new_descriptors->GetDetails(modify_index).type() == FIELD) {
-    Handle<HeapType> field_type(
-        new_descriptors->GetFieldType(modify_index), isolate);
-    new_field_type = Map::GeneralizeFieldType(
-        field_type, new_field_type, isolate);
-    new_descriptors->SetValue(modify_index, *new_field_type);
-  }
 
   Handle<Map> split_map(root_map->FindLastMatchMap(
       verbatim, descriptors, *new_descriptors));
@@ -2783,21 +2625,11 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
       old_descriptors->GetKey(descriptor), *new_descriptors);
 
   if (FLAG_trace_generalization) {
-    PropertyDetails old_details = old_descriptors->GetDetails(modify_index);
-    PropertyDetails new_details = new_descriptors->GetDetails(modify_index);
-    Handle<HeapType> old_field_type = (old_details.type() == FIELD)
-        ? handle(old_descriptors->GetFieldType(modify_index), isolate)
-        : HeapType::Constant(handle(old_descriptors->GetValue(modify_index),
-                                    isolate), isolate);
-    Handle<HeapType> new_field_type = (new_details.type() == FIELD)
-        ? handle(new_descriptors->GetFieldType(modify_index), isolate)
-        : HeapType::Constant(handle(new_descriptors->GetValue(modify_index),
-                                    isolate), isolate);
     old_map->PrintGeneralization(
         stdout, "", modify_index, descriptor, descriptors,
-        old_details.type() == CONSTANT && store_mode == FORCE_FIELD,
-        old_details.representation(), new_details.representation(),
-        *old_field_type, *new_field_type);
+        old_descriptors->GetDetails(modify_index).type() == CONSTANT &&
+            store_mode == FORCE_FIELD,
+        old_representation, updated_representation);
   }
 
   // Add missing transitions.
@@ -2813,13 +2645,13 @@ Handle<Map> Map::GeneralizeRepresentation(Handle<Map> old_map,
 
 // Generalize the representation of all FIELD descriptors.
 Handle<Map> Map::GeneralizeAllFieldRepresentations(
-    Handle<Map> map) {
+    Handle<Map> map,
+    Representation new_representation) {
   Handle<DescriptorArray> descriptors(map->instance_descriptors());
-  for (int i = 0; i < map->NumberOfOwnDescriptors(); ++i) {
-    if (descriptors->GetDetails(i).type() == FIELD) {
-      map = GeneralizeRepresentation(map, i, Representation::Tagged(),
-                                     HeapType::Any(map->GetIsolate()),
-                                     FORCE_FIELD);
+  for (int i = 0; i < map->NumberOfOwnDescriptors(); i++) {
+    PropertyDetails details = descriptors->GetDetails(i);
+    if (details.type() == FIELD) {
+      map = GeneralizeRepresentation(map, i, new_representation, FORCE_FIELD);
     }
   }
   return map;
@@ -3958,9 +3790,7 @@ void JSObject::MigrateInstance(Handle<JSObject> object) {
   // transition that matches the object. This achieves what is needed.
   Handle<Map> original_map(object->map());
   GeneralizeFieldRepresentation(
-      object, 0, Representation::None(),
-      HeapType::None(object->GetIsolate()),
-      ALLOW_AS_CONSTANT);
+      object, 0, Representation::None(), ALLOW_AS_CONSTANT);
   object->map()->set_migration_target(true);
   if (FLAG_trace_migration) {
     object->PrintInstanceMigration(stdout, *original_map, object->map());
@@ -3989,7 +3819,7 @@ MaybeHandle<Object> JSObject::SetPropertyUsingTransition(
   Handle<Map> transition_map(lookup->GetTransitionTarget());
   int descriptor = transition_map->LastAdded();
 
-  Handle<DescriptorArray> descriptors(transition_map->instance_descriptors());
+  DescriptorArray* descriptors = transition_map->instance_descriptors();
   PropertyDetails details = descriptors->GetDetails(descriptor);
 
   if (details.type() == CALLBACKS || attributes != details.attributes()) {
@@ -4006,19 +3836,17 @@ MaybeHandle<Object> JSObject::SetPropertyUsingTransition(
   // Keep the target CONSTANT if the same value is stored.
   // TODO(verwaest): Also support keeping the placeholder
   // (value->IsUninitialized) as constant.
-  if (!lookup->CanHoldValue(value)) {
-    Representation field_representation = value->OptimalRepresentation();
-    Handle<HeapType> field_type = value->OptimalType(
-        lookup->isolate(), field_representation);
-    transition_map = Map::GeneralizeRepresentation(
-        transition_map, descriptor,
-        field_representation, field_type, FORCE_FIELD);
+  if (!lookup->CanHoldValue(value) ||
+      (details.type() == CONSTANT &&
+       descriptors->GetValue(descriptor) != *value)) {
+    transition_map = Map::GeneralizeRepresentation(transition_map,
+        descriptor, value->OptimalRepresentation(), FORCE_FIELD);
   }
 
   JSObject::MigrateToMap(object, transition_map);
 
   // Reload.
-  descriptors = handle(transition_map->instance_descriptors());
+  descriptors = transition_map->instance_descriptors();
   details = descriptors->GetDetails(descriptor);
 
   if (details.type() != FIELD) return value;
@@ -4040,13 +3868,11 @@ MaybeHandle<Object> JSObject::SetPropertyUsingTransition(
 static void SetPropertyToField(LookupResult* lookup,
                                Handle<Object> value) {
   Representation representation = lookup->representation();
-  if (lookup->type() == CONSTANT || !lookup->CanHoldValue(value)) {
-    Representation field_representation = value->OptimalRepresentation();
-    Handle<HeapType> field_type = value->OptimalType(
-        lookup->isolate(), field_representation);
+  if (!lookup->CanHoldValue(value) ||
+      lookup->type() == CONSTANT) {
     JSObject::GeneralizeFieldRepresentation(handle(lookup->holder()),
                                             lookup->GetDescriptorIndex(),
-                                            field_representation, field_type,
+                                            value->OptimalRepresentation(),
                                             FORCE_FIELD);
     DescriptorArray* desc = lookup->holder()->map()->instance_descriptors();
     int descriptor = lookup->GetDescriptorIndex();
@@ -4082,8 +3908,7 @@ static void ConvertAndSetLocalProperty(LookupResult* lookup,
   int descriptor_index = lookup->GetDescriptorIndex();
   if (lookup->GetAttributes() == attributes) {
     JSObject::GeneralizeFieldRepresentation(
-        object, descriptor_index, Representation::Tagged(),
-        HeapType::Any(lookup->isolate()), FORCE_FIELD);
+        object, descriptor_index, Representation::Tagged(), FORCE_FIELD);
   } else {
     Handle<Map> old_map(object->map());
     Handle<Map> new_map = Map::CopyGeneralizeAllRepresentations(old_map,
@@ -7071,13 +6896,7 @@ Handle<Map> Map::CopyReplaceDescriptors(Handle<Map> map,
     map->set_transitions(*transitions);
     result->SetBackPointer(*map);
   } else {
-    int length = descriptors->number_of_descriptors();
-    for (int i = 0; i < length; i++) {
-      descriptors->SetRepresentation(i, Representation::Tagged());
-      if (descriptors->GetDetails(i).type() == FIELD) {
-        descriptors->SetValue(i, HeapType::Any());
-      }
-    }
+    descriptors->InitializeRepresentations(Representation::Tagged());
   }
 
   return result;
@@ -8266,27 +8085,16 @@ Handle<DescriptorArray> DescriptorArray::Merge(Handle<Map> left_map,
         (left_details.type() == CONSTANT &&
          right_details.type() == CONSTANT &&
          left->GetValue(descriptor) != right->GetValue(descriptor))) {
-      ASSERT(left_details.type() == CONSTANT || left_details.type() == FIELD);
-      ASSERT(right_details.type() == CONSTANT || right_details.type() == FIELD);
       Representation representation = left_details.representation().generalize(
           right_details.representation());
-      Handle<HeapType> left_type = (left_details.type() == FIELD)
-          ? handle(left->GetFieldType(descriptor), isolate)
-          : left->GetValue(descriptor)->OptimalType(isolate, representation);
-      Handle<HeapType> right_type = (right_details.type() == FIELD)
-          ? handle(right->GetFieldType(descriptor), isolate)
-          : right->GetValue(descriptor)->OptimalType(isolate, representation);
-      Handle<HeapType> field_type = Map::GeneralizeFieldType(
-          left_type, right_type, isolate);
-      FieldDescriptor d(handle(left->GetKey(descriptor), isolate),
+      FieldDescriptor d(handle(left->GetKey(descriptor)),
                         current_offset++,
-                        field_type,
                         right_details.attributes(),
                         representation);
       result->Set(descriptor, &d);
     } else {
-      Descriptor d(handle(right->GetKey(descriptor), isolate),
-                   handle(right->GetValue(descriptor), isolate),
+      Descriptor d(handle(right->GetKey(descriptor)),
+                   handle(right->GetValue(descriptor), right->GetIsolate()),
                    right_details);
       result->Set(descriptor, &d);
     }
@@ -8295,27 +8103,16 @@ Handle<DescriptorArray> DescriptorArray::Merge(Handle<Map> left_map,
   // |valid| -> |new_size|
   for (; descriptor < new_size; descriptor++) {
     PropertyDetails right_details = right->GetDetails(descriptor);
-    if (right_details.type() == FIELD) {
-      FieldDescriptor d(handle(right->GetKey(descriptor), isolate),
+    if (right_details.type() == FIELD ||
+        (store_mode == FORCE_FIELD && descriptor == modify_index)) {
+      FieldDescriptor d(handle(right->GetKey(descriptor)),
                         current_offset++,
-                        handle(right->GetFieldType(descriptor), isolate),
                         right_details.attributes(),
                         right_details.representation());
       result->Set(descriptor, &d);
-    } else if (store_mode == FORCE_FIELD && descriptor == modify_index) {
-      ASSERT_EQ(CONSTANT, right_details.type());
-      Representation field_representation = right_details.representation();
-      Handle<HeapType> field_type = right->GetValue(descriptor)->OptimalType(
-          isolate, field_representation);
-      FieldDescriptor d(handle(right->GetKey(descriptor), isolate),
-                        current_offset++,
-                        field_type,
-                        right_details.attributes(),
-                        field_representation);
-      result->Set(descriptor, &d);
     } else {
-      Descriptor d(handle(right->GetKey(descriptor), isolate),
-                   handle(right->GetValue(descriptor), isolate),
+      Descriptor d(handle(right->GetKey(descriptor)),
+                   handle(right->GetValue(descriptor), right->GetIsolate()),
                    right_details);
       result->Set(descriptor, &d);
     }