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make check less conservative and add explanation

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This commit is contained in:
Deadbeef 2021-07-27 09:51:57 +08:00
parent 54d4fc245a
commit 2931a9df2f
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GPG Key ID: 027DF9338862ADDD
3 changed files with 24 additions and 11 deletions
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14
compiler/rustc_trait_selection/src/traits/fulfill.rs
View File

@ -649,7 +649,12 @@ fn process_trait_obligation(
if obligation.predicate.is_global() {
// no type variables present, can use evaluation for better caching.
// FIXME: consider caching errors too.
if infcx.predicate_must_hold_considering_regions(obligation) {
//
// If the predicate is considered const, then we cannot use this because
// it will cause false negatives in the ui tests.
if !self.selcx.is_predicate_const(obligation.predicate)
&& infcx.predicate_must_hold_considering_regions(obligation)
{
debug!(
"selecting trait at depth {} evaluated to holds",
obligation.recursion_depth
@ -703,7 +708,12 @@ fn process_projection_obligation(
if obligation.predicate.is_global() {
// no type variables present, can use evaluation for better caching.
// FIXME: consider caching errors too.
if self.selcx.infcx().predicate_must_hold_considering_regions(obligation) {
//
// If the predicate is considered const, then we cannot use this because
// it will cause false negatives in the ui tests.
if !self.selcx.is_predicate_const(obligation.predicate)
&& self.selcx.infcx().predicate_must_hold_considering_regions(obligation)
{
return ProcessResult::Changed(vec![]);
} else {
tracing::debug!("Does NOT hold: {:?}", obligation);

9
compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs
View File

@ -1,6 +1,3 @@
use rustc_hir as hir;
use rustc_middle::ty::PredicateKind;
use crate::infer::canonical::OriginalQueryValues;
use crate::infer::InferCtxt;
use crate::traits::{
@ -49,12 +46,6 @@ fn predicate_must_hold_considering_regions(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool {
if let PredicateKind::Trait(pred) = obligation.predicate.kind().skip_binder() {
if let hir::Constness::Const = pred.constness {
// do not evaluate to holds when we have a const predicate.
return false;
}
}
self.evaluate_obligation_no_overflow(obligation).must_apply_considering_regions()
}

12
compiler/rustc_trait_selection/src/traits/select/mod.rs
View File

@ -316,6 +316,18 @@ pub fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
/// returns `true` if the predicate is considered `const` to
/// this selection context.
pub fn is_predicate_const(&self, pred: ty::Predicate<'_>) -> bool {
match pred.kind().skip_binder() {
ty::PredicateKind::Trait(ty::TraitPredicate {
constness: hir::Constness::Const,
..
}) if self.const_impls_required => true,
_ => false,
}
}
///////////////////////////////////////////////////////////////////////////
// Selection
//