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Rollup merge of #103328 - compiler-errors:trivial-false-const-sugg, r=jackh726

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Do not suggest trivially false const predicates

Pass through constness to `predicate_can_apply` and don't suggest other impls if it's satisfied but not const.

Fixes #103267
This commit is contained in:
Matthias Krüger 2022-10-23 08:14:30 +02:00 • committed by GitHub
commit 1a077420f8
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GPG key ID: 4AEE18F83AFDEB23
13 changed files with 7 additions and 66 deletions
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12
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View file

@ -764,6 +764,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
self.suggest_borrowing_for_object_cast(&mut err, &root_obligation, *concrete_ty, *obj_ty);
}
let mut unsatisfied_const = false;
if trait_predicate.is_const_if_const() && obligation.param_env.is_const() {
let non_const_predicate = trait_ref.without_const();
let non_const_obligation = Obligation {
@ -773,6 +774,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
recursion_depth: obligation.recursion_depth,
};
if self.predicate_may_hold(&non_const_obligation) {
unsatisfied_const = true;
err.span_note(
span,
&format!(
@ -924,7 +926,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
}
} else if !trait_ref.has_non_region_infer()
&& self.predicate_can_apply(obligation.param_env, trait_ref)
&& self.predicate_can_apply(obligation.param_env, trait_predicate)
{
// If a where-clause may be useful, remind the
// user that they can add it.
@ -939,7 +941,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
None,
obligation.cause.body_id,
);
} else if !suggested {
} else if !suggested && !unsatisfied_const {
// Can't show anything else useful, try to find similar impls.
let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
if !self.report_similar_impl_candidates(
@ -1436,7 +1438,7 @@ trait InferCtxtPrivExt<'tcx> {
fn predicate_can_apply(
&self,
param_env: ty::ParamEnv<'tcx>,
pred: ty::PolyTraitRef<'tcx>,
pred: ty::PolyTraitPredicate<'tcx>,
) -> bool;
fn note_obligation_cause(&self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>);
@ -2511,7 +2513,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
fn predicate_can_apply(
&self,
param_env: ty::ParamEnv<'tcx>,
pred: ty::PolyTraitRef<'tcx>,
pred: ty::PolyTraitPredicate<'tcx>,
) -> bool {
struct ParamToVarFolder<'a, 'tcx> {
infcx: &'a InferCtxt<'tcx>,
@ -2555,7 +2557,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
let obligation = Obligation::new(
ObligationCause::dummy(),
param_env,
cleaned_pred.without_const().to_predicate(selcx.tcx()),
cleaned_pred.to_predicate(selcx.tcx()),
);
self.predicate_may_hold(&obligation)