parse method
Parses the input and returns a result wrapped in Result if successful,
null
otherwise.
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) {
final r3 = end.fastParse(state);
if (r3) {
return r2;
}
}
}
state.pos = pos;
return null;
}