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Clone the candidates and match-pairs lazilly, instead of eagerly.

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This commit is contained in:
Niko Matsakis 2015-11-10 05:24:25 -05:00
parent 87358728a4
commit 61884e5543
1 changed files with 17 additions and 17 deletions
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34
src/librustc_mir/build/matches/test.rs
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@ -288,14 +288,15 @@ impl<'a,'tcx> Builder<'a,'tcx> {
test_outcome: usize,
candidate: &Candidate<'pat, 'tcx>)
-> Option<Candidate<'pat, 'tcx>> {
let candidate = candidate.clone();
let match_pairs = candidate.match_pairs;
let result = self.match_pairs_under_assumption(test_lvalue,
test_kind,
test_outcome,
match_pairs);
&candidate.match_pairs);
match result {
Some(match_pairs) => Some(Candidate { match_pairs: match_pairs, ..candidate }),
Some(match_pairs) => Some(Candidate { match_pairs: match_pairs,
bindings: candidate.bindings.clone(),
guard: candidate.guard.clone(),
arm_index: candidate.arm_index }),
None => None,
}
}
@ -306,21 +307,20 @@ impl<'a,'tcx> Builder<'a,'tcx> {
test_lvalue: &Lvalue<'tcx>,
test_kind: &TestKind<'tcx>,
test_outcome: usize,
match_pairs: Vec<MatchPair<'pat, 'tcx>>)
match_pairs: &[MatchPair<'pat, 'tcx>])
-> Option<Vec<MatchPair<'pat, 'tcx>>> {
let mut result = vec![];
for match_pair in match_pairs {
// if the match pair is testing a different lvalue, it
// is unaffected by this test.
if match_pair.lvalue != *test_lvalue {
result.push(match_pair);
continue;
}
// if this test doesn't tell us anything about this match-pair, then hang onto it.
if !self.test_informs_match_pair(&match_pair, test_kind, test_outcome) {
result.push(match_pair);
// If the match pair is either:
// (1) testing a different lvalue; or,
// (2) the test doesn't tell us anything about this match-pair,
// then we have to retain it as for after the test is complete.
if
match_pair.lvalue != *test_lvalue || // (1)
!self.test_informs_match_pair(match_pair, test_kind, test_outcome) // (2)
{
result.push(match_pair.clone());
continue;
}
@ -445,7 +445,7 @@ impl<'a,'tcx> Builder<'a,'tcx> {
/// observed that `option` has the discriminant `Ok`, then the
/// second arm cannot apply.
pub fn consequent_match_pairs_under_assumption<'pat>(&mut self,
match_pair: MatchPair<'pat, 'tcx>,
match_pair: &MatchPair<'pat, 'tcx>,
test_kind: &TestKind<'tcx>,
test_outcome: usize)
-> Option<Vec<MatchPair<'pat, 'tcx>>> {
@ -511,7 +511,7 @@ impl<'a,'tcx> Builder<'a,'tcx> {
PatternKind::Binding { .. } |
PatternKind::Leaf { .. } |
PatternKind::Deref { .. } => {
self.error_simplifyable(&match_pair)
self.error_simplifyable(match_pair)
}
}
}