parse method

Implementation

@override
Result<String>? parse(State<StringReader> state) {
  final input = state.input;
  if (state.pos < input.length) {
    final c = input.readChar(state.pos);
    state.pos += input.count;
    return Result(String.fromCharCode(c));
  }

  return state.fail(ErrorUnexpectedEndOfInput());
}