BitField<
    Creates a bit field of all zeros.
The given length must be at most 62.
Implementation
BitField(this._length)
  : assert(_length <= _smiBits),
    _bits = _allZeros;Creates a bit field of all zeros.
The given length must be at most 62.
BitField(this._length)
  : assert(_length <= _smiBits),
    _bits = _allZeros;