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Rollup merge of #69022 - ljedrz:traits_tweak_vecs, r=petrochenkov

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traits: preallocate 2 Vecs of known initial size

The 2 preallocations are pretty obvious; both vectors will be as big as or larger than the collections they are created from.

In `WfPredicates::normalize` the change from a functional style improves readability and should be perf-friendly, too.
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Dylan DPC 2020-02-11 16:36:59 +01:00 committed by GitHub
commit d8b4abc4ad
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2 changed files with 5 additions and 4 deletions
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2
src/librustc/traits/select.rs
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@ -3472,7 +3472,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// that order.
let predicates = tcx.predicates_of(def_id);
assert_eq!(predicates.parent, None);
let mut obligations = Vec::new();
let mut obligations = Vec::with_capacity(predicates.predicates.len());
for (predicate, _) in predicates.predicates {
let predicate = normalize_with_depth_to(
self,

7
src/librustc/traits/wf.rs
View File

@ -143,14 +143,15 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
let cause = self.cause(traits::MiscObligation);
let infcx = &mut self.infcx;
let param_env = self.param_env;
let mut obligations = Vec::new();
self.out.iter().inspect(|pred| assert!(!pred.has_escaping_bound_vars())).for_each(|pred| {
let mut obligations = Vec::with_capacity(self.out.len());
for pred in &self.out {
assert!(!pred.has_escaping_bound_vars());
let mut selcx = traits::SelectionContext::new(infcx);
let i = obligations.len();
let value =
traits::normalize_to(&mut selcx, param_env, cause.clone(), pred, &mut obligations);
obligations.insert(i, value);
});
}
obligations
}