anchor.diff:        _init(_index.length << 1, _hashMask >> 1, _data, _usedData);
       }
     }
  -  
  +
     void clear() {
       if (!isEmpty) {
         _init(_index.length, _hashMask);
       }
     }
  -  
  +
     void _init(int size, int hashMask, [List oldData, int oldUsed]) {
       _index = new Uint32List(size);
       _hashMask = hashMask;
  
positive.code:       i = _HashBase._nextProbe(i, sizeMask);
        pair = _index[i];
      }
      return _data;    
    }
  
    E lookup(Object key) {
      var k = _getKeyOrData(key);
      return identical(_data, k) ? null : k;
    }
    
    bool contains(Object key) => !identical(_data, _getKeyOrData(key));
  
    bool remove(Object key) {
  
negative.code:       }
      }
    }
  
    void _insert(K key, V value, int hashPattern, int i) {
      if (_usedData == _data.length) {
        _rehash();
  