anchor.diff:    // NOTE: When maps are deserialized, their _index and _hashMask is regenerated
     // lazily by _regenerateIndex.
     // TODO(koda): Consider also using null _index for tiny, linear-search tables.
  -  Uint32List _index;
  +  Uint32List _index = new Uint32List(_HashBase._INITIAL_INDEX_SIZE);
   
     // Cached in-place mask for the hash pattern component. 
  -  int _hashMask;
  +  int _hashMask = _HashBase._indexSizeToHashMask(_HashBase._INITIAL_INDEX_SIZE);
   
     // Fixed-length list of keys (set) or key/value at even/odd indices (map).
     List _data;
  
positive.code:   V remove(Object o) => _validKey(o) ? super.remove(o) : null;
  
    _CompactLinkedCustomHashMap(this._equality, this._hasher, validKey)
        : _validKey = (validKey != null) ? validKey : new _TypeTest<K>().test {
      _index = new Uint32List(_HashBase._INITIAL_INDEX_SIZE);
      _hashMask = _HashBase._indexSizeToHashMask(_HashBase._INITIAL_INDEX_SIZE);
      _data = new List(_HashBase._INITIAL_INDEX_SIZE);
    }
  }
  
  // Iterates through _data[_offset + _step], _data[_offset + 2*_step], ...
  
negative.code:     with _HashBase, _OperatorEqualsAndHashCode, SetMixin<E>
      implements LinkedHashSet<E> {
  
    _CompactLinkedHashSet() : super(_HashBase._INITIAL_INDEX_SIZE >> 1) {
      assert(_HashBase._UNUSED_PAIR == 0);
    }
  
    int get length => _usedData - _deletedKeys;
  