Fix issue 386, a bug in JSObject::ReplaceSlowProperty with constant transitio...

src/objects.h

 // Copyright 2006-2009 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 2015 matching lines @@
   // Returns the value at entry.
   Object* ValueAt(int entry) { return get(EntryToIndex(entry)+1); }
 
   // Set the value for entry.
   void ValueAtPut(int entry, Object* value) {
     set(EntryToIndex(entry)+1, value);
   }
 
   // Returns the property details for the property at entry.
   PropertyDetails DetailsAt(int entry) {
+    ASSERT(entry >= 0);  // Not found is -1, which is not caught by get().
     return PropertyDetails(Smi::cast(get(EntryToIndex(entry) + 2)));
   }
 
   // Set the details for entry.
   void DetailsAtPut(int entry, PropertyDetails value) {
     set(EntryToIndex(entry) + 2, value.AsSmi());
   }
 
   // Remove all entries were key is a number and (from <= key && key < to).
   void RemoveNumberEntries(uint32_t from, uint32_t to);
@@ skipping 2406 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_