anchor.diff:    _CompactLinkedHashSet() {
       assert(_HashBase._UNUSED_PAIR == 0);
       _index = new Uint32List(_HashBase._INITIAL_INDEX_SIZE);
  +    _hashMask = _HashBase._indexSizeToHashMask(_HashBase._INITIAL_INDEX_SIZE);
       _data = new List(_HashBase._INITIAL_INDEX_SIZE >> 1);
     }
   
  
positive.code:     with MapMixin<K, V>, _LinkedHashMapMixin<K, V>, _HashBase,
           _IdenticalAndIdentityHashCode
      implements LinkedHashMap<K, V> {
  }
  
  class _CompactLinkedCustomHashMap<K, V> extends _HashFieldBase
  
negative.code:     int pair = _index[i];
      while (pair != _HashBase._UNUSED_PAIR) {
        if (pair == _HashBase._DELETED_PAIR) {
          if (firstDeleted < 0) {
            firstDeleted = i;
          }
        } else {
  