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Avoid storing the ImplPolarity and Constness next to a TraitRef and use TraitPredicate instead

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This commit is contained in:
Oli Scherer
2021-10-25 14:29:54 +00:00
committed by Deadbeef
parent d161cc2071
commit a848c4ba3f
11 changed files with 59 additions and 53 deletions
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38
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@@ -1089,10 +1089,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate((
ty::ConstnessAnd { constness: ty::BoundConstness::ConstIfConst, .. },
_,
)) => {}
ParamCandidate(trait_pred)
if trait_pred.skip_binder().constness
== ty::BoundConstness::ConstIfConst => {}
// auto trait impl
AutoImplCandidate(..) => {}
// generator, this will raise error in other places
@@ -1474,7 +1473,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// Check if a bound would previously have been removed when normalizing
// the param_env so that it can be given the lowest priority. See
// #50825 for the motivation for this.
let is_global = |cand: &ty::PolyTraitRef<'tcx>| {
let is_global = |cand: &ty::PolyTraitPredicate<'tcx>| {
cand.is_global(self.infcx.tcx) && !cand.has_late_bound_regions()
};
@@ -1507,25 +1506,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| ConstDropCandidate,
) => false,
(
ParamCandidate((other, other_polarity)),
ParamCandidate((victim, victim_polarity)),
) => {
let same_except_bound_vars = other.value.skip_binder()
== victim.value.skip_binder()
&& other.constness == victim.constness
&& other_polarity == victim_polarity
&& !other.value.skip_binder().has_escaping_bound_vars();
(ParamCandidate(other), ParamCandidate(victim)) => {
let same_except_bound_vars = other.skip_binder().trait_ref
== victim.skip_binder().trait_ref
&& other.skip_binder().constness == victim.skip_binder().constness
&& other.skip_binder().polarity == victim.skip_binder().polarity
&& !other.skip_binder().trait_ref.has_escaping_bound_vars();
if same_except_bound_vars {
// See issue #84398. In short, we can generate multiple ParamCandidates which are
// the same except for unused bound vars. Just pick the one with the fewest bound vars
// or the current one if tied (they should both evaluate to the same answer). This is
// probably best characterized as a "hack", since we might prefer to just do our
// best to *not* create essentially duplicate candidates in the first place.
other.value.bound_vars().len() <= victim.value.bound_vars().len()
} else if other.value == victim.value
&& victim.constness == ty::BoundConstness::NotConst
&& other_polarity == victim_polarity
other.bound_vars().len() <= victim.bound_vars().len()
} else if other.skip_binder().trait_ref == victim.skip_binder().trait_ref
&& victim.skip_binder().constness == ty::BoundConstness::NotConst
&& other.skip_binder().polarity == victim.skip_binder().polarity
{
// Drop otherwise equivalent non-const candidates in favor of const candidates.
true
@@ -1555,11 +1551,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| TraitAliasCandidate(..)
| ObjectCandidate(_)
| ProjectionCandidate(_),
) => !is_global(&cand.0.value),
) => !is_global(cand),
(ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(&cand.0.value)
is_global(cand)
}
(
ImplCandidate(_)
@@ -1575,7 +1571,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(&cand.0.value) && other.evaluation.must_apply_modulo_regions()
is_global(cand) && other.evaluation.must_apply_modulo_regions()
}
(ProjectionCandidate(i), ProjectionCandidate(j))