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Make MatcherPos not derive Clone.

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It's only used in one place, and there we clone and then make a bunch of
modifications. It's clearer if we duplicate more explicitly, and there's
a symmetry now between `sequence()` and `empty_sequence()`.
This commit is contained in:
Nicholas Nethercote 2022-03-31 13:50:30 +11:00
parent f68a0449ed
commit c6fedd4f10
1 changed files with 24 additions and 8 deletions
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32
compiler/rustc_expand/src/mbe/macro_parser.rs
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@ -132,7 +132,6 @@ struct Parent<'tt> {
/// <--------------> first submatcher; three tts, zero metavars
/// <--------------------------> top-level matcher; two tts, one metavar
/// ```
#[derive(Clone)]
struct MatcherPos<'tt> {
/// The tokens that make up the current matcher. When we are within a `Sequence` or `Delimited`
/// submatcher, this is just the contents of that submatcher.
@ -177,6 +176,25 @@ impl<'tt> MatcherPos<'tt> {
}
}
fn empty_sequence(
parent_mp: &MatcherPos<'tt>,
seq: &'tt SequenceRepetition,
empty_matches: Lrc<NamedMatchVec>,
) -> Self {
let mut mp = MatcherPos {
tts: parent_mp.tts,
idx: parent_mp.idx + 1,
matches: parent_mp.matches.clone(), // a cheap clone
seq_depth: parent_mp.seq_depth,
match_cur: parent_mp.match_cur + seq.num_captures,
kind: parent_mp.kind.clone(), // an expensive clone
};
for idx in parent_mp.match_cur..parent_mp.match_cur + seq.num_captures {
mp.push_match(idx, MatchedSeq(empty_matches.clone()));
}
mp
}
fn sequence(
parent_mp: Box<MatcherPos<'tt>>,
seq: &'tt SequenceRepetition,
@ -468,13 +486,11 @@ impl<'tt> TtParser<'tt> {
let op = seq.kleene.op;
if op == mbe::KleeneOp::ZeroOrMore || op == mbe::KleeneOp::ZeroOrOne {
// Allow for the possibility of zero matches of this sequence.
let mut new_mp = mp.clone();
new_mp.match_cur += seq.num_captures;
new_mp.idx += 1;
for idx in mp.match_cur..mp.match_cur + seq.num_captures {
new_mp.push_match(idx, MatchedSeq(self.empty_matches.clone()));
}
self.cur_mps.push(new_mp);
self.cur_mps.push(box MatcherPos::empty_sequence(
&*mp,
&seq,
self.empty_matches.clone(),
));
}
// Allow for the possibility of one or more matches of this sequence.