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Rollup merge of #143307 - compiler-errors:fast-path-nitpicks, r=lcnr

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Fast path nitpicks

Miscellaneous commits that I didn't really want to fold into anything else.

Fixes one theoretical bug with the fast path not considering polarity for `T: !Sized` bounds.
This commit is contained in:
Jacob Pratt
2025-07-04 05:47:24 +02:00
committed by GitHub
parent 826d4bc858 91c53c97a9
commit 9de211b95a
5 changed files with 31 additions and 24 deletions
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14
compiler/rustc_trait_selection/src/traits/query/type_op/prove_predicate.rs
View File

@@ -21,19 +21,9 @@ impl<'tcx> super::QueryTypeOp<'tcx> for ProvePredicate<'tcx> {
if let ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(term)) =
key.value.predicate.kind().skip_binder()
&& term.is_trivially_wf(tcx)
{
match term.as_type()?.kind() {
ty::Param(_)
| ty::Bool
| ty::Char
| ty::Int(_)
| ty::Float(_)
| ty::Str
| ty::Uint(_) => {
return Some(());
}
_ => {}
}
return Some(());
}
None

7
compiler/rustc_trait_selection/src/traits/util.rs
View File

@@ -368,16 +368,17 @@ pub fn sizedness_fast_path<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
// Proving `Sized`/`MetaSized`, very often on "obviously sized" types like
// `&T`, accounts for about 60% percentage of the predicates we have to prove. No need to
// canonicalize and all that for such cases.
if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_ref)) =
if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) =
predicate.kind().skip_binder()
&& trait_pred.polarity == ty::PredicatePolarity::Positive
{
let sizedness = match tcx.as_lang_item(trait_ref.def_id()) {
let sizedness = match tcx.as_lang_item(trait_pred.def_id()) {
Some(LangItem::Sized) => SizedTraitKind::Sized,
Some(LangItem::MetaSized) => SizedTraitKind::MetaSized,
_ => return false,
};
if trait_ref.self_ty().has_trivial_sizedness(tcx, sizedness) {
if trait_pred.self_ty().has_trivial_sizedness(tcx, sizedness) {
debug!("fast path -- trivial sizedness");
return true;
}