Make DescriptorArray::IsMoreGeneralThan() and DescriptorArray::Merge() compatible again.

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 8502 matching lines @@
 
   for (int descriptor = verbatim; descriptor < valid; descriptor++) {
     PropertyDetails details = GetDetails(descriptor);
     PropertyDetails other_details = other->GetDetails(descriptor);
     if (!other_details.representation().fits_into(details.representation())) {
       return false;
     }
     if (details.type() == CONSTANT) {
       if (other_details.type() != CONSTANT) return false;
       if (GetValue(descriptor) != other->GetValue(descriptor)) return false;
+    } else if (details.type() == FIELD && other_details.type() == FIELD) {
+      if (!other->GetFieldType(descriptor)->NowIs(GetFieldType(descriptor))) {
+        return false;
+      }
     }
   }
 
   return true;
 }
 
 
 // We need the whiteness witness since sort will reshuffle the entries in the
 // descriptor array. If the descriptor array were to be black, the shuffling
 // would move a slot that was already recorded as pointing into an evacuation
@@ skipping 8895 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal