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Normalize when finding trait object candidates

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This commit is contained in:
Matthew Jasper 2020-10-08 21:52:40 +01:00
parent 6c43a64931
commit 50dde2e4d8
5 changed files with 107 additions and 66 deletions
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24
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -1174,7 +1174,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
if let ty::PredicateAtom::Trait(pred, _) = bound_predicate.skip_binder() {
let bound = bound_predicate.rebind(pred.trait_ref);
if self.infcx.probe(|_| {
match self.match_projection(
match self.match_normalize_trait_ref(
obligation,
bound,
placeholder_trait_predicate.trait_ref,
@ -1202,7 +1202,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
/// Equates the trait in `obligation` with trait bound. If the two traits
/// can be equated and the normalized trait bound doesn't contain inference
/// variables or placeholders, the normalized bound is returned.
fn match_projection(
fn match_normalize_trait_ref(
&mut self,
obligation: &TraitObligation<'tcx>,
trait_bound: ty::PolyTraitRef<'tcx>,
@ -1352,10 +1352,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| BuiltinUnsizeCandidate
| BuiltinCandidate { .. }
| TraitAliasCandidate(..)
| ObjectCandidate
| ObjectCandidate(_)
| ProjectionCandidate(_),
) => !is_global(cand),
(ObjectCandidate | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
(ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(cand)
@ -1376,20 +1376,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
is_global(cand) && other.evaluation.must_apply_modulo_regions()
}
(ProjectionCandidate(i), ProjectionCandidate(j)) => {
(ProjectionCandidate(i), ProjectionCandidate(j))
| (ObjectCandidate(i), ObjectCandidate(j)) => {
// Arbitrarily pick the lower numbered candidate for backwards
// compatibility reasons. Don't let this affect inference.
i < j && !needs_infer
}
(ObjectCandidate, ObjectCandidate) => bug!("Duplicate object candidate"),
(ObjectCandidate, ProjectionCandidate(_))
| (ProjectionCandidate(_), ObjectCandidate) => {
(ObjectCandidate(_), ProjectionCandidate(_))
| (ProjectionCandidate(_), ObjectCandidate(_)) => {
bug!("Have both object and projection candidate")
}
// Arbitrarily give projection and object candidates priority.
(
ObjectCandidate | ProjectionCandidate(_),
ObjectCandidate(_) | ProjectionCandidate(_),
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
@ -1409,7 +1409,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| BuiltinUnsizeCandidate
| BuiltinCandidate { .. }
| TraitAliasCandidate(..),
ObjectCandidate | ProjectionCandidate(_),
ObjectCandidate(_) | ProjectionCandidate(_),
) => false,
(&ImplCandidate(other_def), &ImplCandidate(victim_def)) => {
@ -1885,9 +1885,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
/// Normalize `where_clause_trait_ref` and try to match it against
/// `obligation`. If successful, return any predicates that
/// result from the normalization. Normalization is necessary
/// because where-clauses are stored in the parameter environment
/// unnormalized.
/// result from the normalization.
fn match_where_clause_trait_ref(
&mut self,
obligation: &TraitObligation<'tcx>,