parse method

Implementation

@override
Result<O2>? parse(State<I> state) {
  final pos = state.pos;
  final r1 = start.fastParse(state);
  if (r1) {
    final r2 = p.parse(state);
    if (r2 != null) {
      return r2;
    }

    state.pos = pos;
  }

  return null;
}