rule method

Implementation

@override
Parser<Rule> rule() => super.rule().map((each) {
  scope.clear();
  final head = each[0];
  final rest = each[1];
  if (rest == null) {
    return Rule(head, const True());
  }
  final List terms = rest[1];
  if (terms.isEmpty) {
    return Rule(head, const True());
  } else if (terms.length == 1) {
    return Rule(head, terms[0]);
  } else {
    return Rule(head, Conjunction(terms.cast()));
  }
});