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Revert #92191 Prefer projection candidates instead of param_env candidates for Sized predicates

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This commit is contained in:
Jack Huey 2022-04-30 21:00:57 -04:00
parent 76d4862fdd
commit 8e31cdefc4
5 changed files with 64 additions and 17 deletions
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4
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View file

@ -175,9 +175,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let needs_infer = stack.obligation.predicate.has_infer_types_or_consts();
let sized_predicate = self.tcx().lang_items().sized_trait()
== Some(stack.obligation.predicate.skip_binder().def_id());
// If there are STILL multiple candidates, we can further
// reduce the list by dropping duplicates -- including
// resolving specializations.
@ -186,7 +183,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
while i < candidates.len() {
let is_dup = (0..candidates.len()).filter(|&j| i != j).any(|j| {
self.candidate_should_be_dropped_in_favor_of(
sized_predicate,
&candidates[i],
&candidates[j],
needs_infer,

20
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -1553,7 +1553,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
/// See the comment for "SelectionCandidate" for more details.
fn candidate_should_be_dropped_in_favor_of(
&mut self,
sized_predicate: bool,
victim: &EvaluatedCandidate<'tcx>,
other: &EvaluatedCandidate<'tcx>,
needs_infer: bool,
@ -1625,16 +1624,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// Drop otherwise equivalent non-const fn pointer candidates
(FnPointerCandidate { .. }, FnPointerCandidate { is_const: false }) => true,
// If obligation is a sized predicate or the where-clause bound is
// global, prefer the projection or object candidate. See issue
// #50825 and #89352.
(ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
sized_predicate || is_global(cand)
}
(ParamCandidate(ref cand), ObjectCandidate(_) | ProjectionCandidate(_)) => {
!(sized_predicate || is_global(cand))
}
// Global bounds from the where clause should be ignored
// here (see issue #50825). Otherwise, we have a where
// clause so don't go around looking for impls.
@ -1650,8 +1639,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
| BuiltinCandidate { .. }
| TraitAliasCandidate(..),
| TraitAliasCandidate(..)
| ObjectCandidate(_)
| ProjectionCandidate(_),
) => !is_global(cand),
(ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(cand)
}
(
ImplCandidate(_)
| ClosureCandidate