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Update the macro parser to allow at most once repetitions for ? Kleene

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This commit is contained in:
Mark Mansi 2018-01-18 19:30:15 -06:00
parent 760879bc88
commit bb8110c1fc
1 changed files with 22 additions and 16 deletions
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38
src/libsyntax/ext/tt/macro_parser.rs
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@ -486,8 +486,8 @@ fn inner_parse_loop(
match item.top_elts.get_tt(idx) {
// Need to descend into a sequence
TokenTree::Sequence(sp, seq) => {
if seq.op == quoted::KleeneOp::ZeroOrMore {
// Examine the case where there are 0 matches of this sequence
// Examine the case where there are 0 matches of this sequence
if seq.op == quoted::KleeneOp::ZeroOrMore || seq.op == quoted::KleeneOp::ZeroOrOne {
let mut new_item = item.clone();
new_item.match_cur += seq.num_captures;
new_item.idx += 1;
@ -497,20 +497,26 @@ fn inner_parse_loop(
cur_items.push(new_item);
}
// Examine the case where there is at least one match of this sequence
let matches = create_matches(item.matches.len());
cur_items.push(Box::new(MatcherPos {
stack: vec![],
sep: seq.separator.clone(),
idx: 0,
matches,
match_lo: item.match_cur,
match_cur: item.match_cur,
match_hi: item.match_cur + seq.num_captures,
up: Some(item),
sp_lo: sp.lo(),
top_elts: Tt(TokenTree::Sequence(sp, seq)),
}));
// For ZeroOrMore and OneOrMore, we want to examine the case were there is at
// least one match. For ZeroOrOne, we only want the case where there is exactly
// one match.
if (seq.op == quoted::KleeneOp::ZeroOrOne && seq.num_captures == 1) ||
seq.op != quoted::KleeneOp::ZeroOrOne {
let matches = create_matches(item.matches.len());
cur_items.push(Box::new(MatcherPos {
stack: vec![],
sep: seq.separator.clone(),
idx: 0,
matches,
match_lo: item.match_cur,
match_cur: item.match_cur,
match_hi: item.match_cur + seq.num_captures,
up: Some(item),
sp_lo: sp.lo(),
top_elts: Tt(TokenTree::Sequence(sp, seq)),
}));
}
}
// We need to match a metavar (but the identifier is invalid)... this is an error