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Rollup merge of #121853 - lcnr:normalizes_to-polarity, r=compiler-errors

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normalizes-to: handle negative impls

necessary to build the stage 2 compiler in #121848 😁

r? `@compiler-errors`
This commit is contained in:
Matthias Krüger 2024-03-01 17:51:33 +01:00 committed by GitHub
commit ff22925e50
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2 changed files with 38 additions and 3 deletions
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19
compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
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@ -162,15 +162,28 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
let tcx = ecx.tcx();
let goal_trait_ref = goal.predicate.alias.trait_ref(tcx);
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let impl_trait_header = tcx.impl_trait_header(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
if !drcx.args_may_unify(goal_trait_ref.args, impl_trait_ref.skip_binder().args) {
if !drcx.args_may_unify(
goal.predicate.trait_ref(tcx).args,
impl_trait_header.skip_binder().trait_ref.args,
) {
return Err(NoSolution);
}
// We have to ignore negative impls when projecting.
let impl_polarity = impl_trait_header.skip_binder().polarity;
match impl_polarity {
ty::ImplPolarity::Negative => return Err(NoSolution),
ty::ImplPolarity::Reservation => {
unimplemented!("reservation impl for trait with assoc item: {:?}", goal)
}
ty::ImplPolarity::Positive => {}
};
ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
let impl_args = ecx.fresh_args_for_item(impl_def_id);
let impl_trait_ref = impl_trait_ref.instantiate(tcx, impl_args);
let impl_trait_ref = impl_trait_header.instantiate(tcx, impl_args).trait_ref;
ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;

22
tests/ui/traits/negative-impls/negative-impl-normalizes-to.rs Normal file
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@ -0,0 +1,22 @@
//@ revisions: current next
//@[next] compile-flags: -Znext-solver
//@ check-pass
// Check that negative impls for traits with associated types
// do not result in an ICE when trying to normalize.
#![feature(negative_impls)]
trait Trait {
type Assoc;
}
struct Local<T>(T);
impl !Trait for Local<u32> {}
impl Trait for Local<i32> {
type Assoc = i32;
}
trait NoOverlap {}
impl<T: Trait<Assoc = u32>> NoOverlap for T {}
impl<T> NoOverlap for Local<T> {}
fn main() {}