anchor.diff:   * List backed by 32-bit unsigned integers.
    */
   class _FbUint32List extends _FbList<int> {
  -  List<int> _items;
  -
     _FbUint32List(BufferPointer bp) : super(bp);
   
     @override
     int operator [](int i) {
  -    _items ??= new List<int>(length);
  -    int item = _items[i];
  -    if (item == null) {
  -      item = bp._getUint32(4 + 4 * i);
  -      _items[i] = item;
  -    }
  -    return item;
  +    return bp._getUint32(4 + 4 * i);
     }
   }
   
  
positive.code:   bool operator [](int i) {
      int index = i ~/ 8;
      int mask = 1 << i % 8;
      return uint8List[index] & mask != 0;
    }
  
    @override
    void operator []=(int i, bool e) =>
        throw new StateError('Attempt to modify immutable list');
  }
  
  /**
   * The list backed by 64-bit values - Uint64 length and Float64.
   */
  class _FbFloat64List extends _FbList<double> {
    List<double> _items;
  
    _FbFloat64List(BufferPointer bp) : super(bp);
  
    @override
    double operator [](int i) {
      _items ??= new List<double>(length);
      double item = _items[i];
      if (item == null) {
        BufferPointer ref = bp._advance(8 + 8 * i);
        item = ref._getFloat64();
        _items[i] = item;
      }
      return item;
    }
  }
  
  
negative.code:  * List of booleans backed by 8-bit unsigned integers.
   */
  class _FbBoolList extends Object with ListMixin<bool> implements List<bool> {
    final BufferPointer bp;
    int _length;
  
    _FbBoolList(this.bp);
  
    @override
    int get length {
      if (_length == null) {
        int byteLength = bp._getUint32();
        _length = (byteLength - 1) * 8 - _getByte(byteLength - 1);
      }
      return _length;
    }
  