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Update implied_outlives_bounds to properly register implied bounds behind normalization

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This commit is contained in:
Jack Huey 2022-09-11 04:27:25 -04:00
parent 1a663c0f53
commit 0637b6b471
4 changed files with 62 additions and 43 deletions
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89
compiler/rustc_traits/src/implied_outlives_bounds.rs
View file

@ -70,48 +70,61 @@ fn compute_implied_outlives_bounds<'tcx>(
let obligations = wf::obligations(ocx.infcx, param_env, CRATE_DEF_ID, 0, arg, DUMMY_SP)
.unwrap_or_default();
// While these predicates should all be implied by other parts of
// the program, they are still relevant as they may constrain
// inference variables, which is necessary to add the correct
// implied bounds in some cases, mostly when dealing with projections.
ocx.register_obligations(
obligations.iter().filter(|o| o.predicate.has_non_region_infer()).cloned(),
);
// From the full set of obligations, just filter down to the
// region relationships.
outlives_bounds.extend(obligations.into_iter().filter_map(|obligation| {
for obligation in obligations {
debug!(?obligation);
assert!(!obligation.has_escaping_bound_vars());
match obligation.predicate.kind().no_bound_vars() {
None => None,
Some(pred) => match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(..))
| ty::PredicateKind::Subtype(..)
| ty::PredicateKind::Coerce(..)
| ty::PredicateKind::Clause(ty::Clause::Projection(..))
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::ObjectSafe(..)
| ty::PredicateKind::ConstEvaluatable(..)
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
ty::PredicateKind::WellFormed(arg) => {
wf_args.push(arg);
None
// While these predicates should all be implied by other parts of
// the program, they are still relevant as they may constrain
// inference variables, which is necessary to add the correct
// implied bounds in some cases, mostly when dealing with projections.
//
// Another important point here: we only register `Projection`
// predicates, since otherwise we might register outlives
// predicates containing inference variables, and we don't
// learn anything new from those.
if obligation.predicate.has_non_region_infer() {
match obligation.predicate.kind().skip_binder() {
ty::PredicateKind::Clause(ty::Clause::Projection(..)) => {
ocx.register_obligation(obligation.clone());
}
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(
ty::OutlivesPredicate(r_a, r_b),
)) => Some(ty::OutlivesPredicate(r_a.into(), r_b)),
ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
ty_a,
r_b,
))) => Some(ty::OutlivesPredicate(ty_a.into(), r_b)),
},
_ => {}
}
}
}));
let pred = match obligation.predicate.kind().no_bound_vars() {
None => continue,
Some(pred) => pred,
};
match pred {
ty::PredicateKind::Clause(ty::Clause::Trait(..))
| ty::PredicateKind::Subtype(..)
| ty::PredicateKind::Coerce(..)
| ty::PredicateKind::Clause(ty::Clause::Projection(..))
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::ObjectSafe(..)
| ty::PredicateKind::ConstEvaluatable(..)
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::TypeWellFormedFromEnv(..) => {}
// We need to search through *all* WellFormed predicates
ty::PredicateKind::WellFormed(arg) => {
wf_args.push(arg);
}
// We need to register region relationships
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(ty::OutlivesPredicate(
r_a,
r_b,
))) => outlives_bounds.push(ty::OutlivesPredicate(r_a.into(), r_b)),
ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
ty_a,
r_b,
))) => outlives_bounds.push(ty::OutlivesPredicate(ty_a.into(), r_b)),
}
}
}
// This call to `select_all_or_error` is necessary to constrain inference variables, which we

1
compiler/rustc_traits/src/lib.rs
View file

@ -4,6 +4,7 @@
#![deny(rustc::untranslatable_diagnostic)]
#![deny(rustc::diagnostic_outside_of_impl)]
#![feature(let_chains)]
#![feature(drain_filter)]
#![recursion_limit = "256"]
#[macro_use]