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use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::traits::query::NoSolution;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, ParamEnvAnd, TyCtxt, TypeFoldable, TypeVisitableExt};
use rustc_trait_selection::traits::query::normalize::QueryNormalizeExt;
use rustc_trait_selection::traits::{Normalized, ObligationCause};
use std::sync::atomic::Ordering;
pub(crate) fn provide(p: &mut Providers) {
*p = Providers {
try_normalize_generic_arg_after_erasing_regions: |tcx, goal| {
debug!("try_normalize_generic_arg_after_erasing_regions(goal={:#?}", goal);
tcx.sess
.perf_stats
.normalize_generic_arg_after_erasing_regions
.fetch_add(1, Ordering::Relaxed);
try_normalize_after_erasing_regions(tcx, goal)
},
..*p
};
}
fn try_normalize_after_erasing_regions<'tcx, T: TypeFoldable<TyCtxt<'tcx>> + PartialEq + Copy>(
tcx: TyCtxt<'tcx>,
goal: ParamEnvAnd<'tcx, T>,
) -> Result<T, NoSolution> {
let ParamEnvAnd { param_env, value } = goal;
let infcx = tcx.infer_ctxt().build();
let cause = ObligationCause::dummy();
match infcx.at(&cause, param_env).query_normalize(value) {
Ok(Normalized { value: normalized_value, obligations: normalized_obligations }) => {
// We don't care about the `obligations`; they are
// always only region relations, and we are about to
// erase those anyway:
// This has been seen to fail in RL, so making it a non-debug assertion to better catch
// those cases.
assert_eq!(
normalized_obligations.iter().find(|p| not_outlives_predicate(p.predicate)),
None,
);
let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
// It's unclear when `resolve_vars` would have an effect in a
// fresh `InferCtxt`. If this assert does trigger, it will give
// us a test case.
debug_assert_eq!(normalized_value, resolved_value);
let erased = infcx.tcx.erase_regions(resolved_value);
debug_assert!(!erased.needs_infer(), "{erased:?}");
Ok(erased)
}
Err(NoSolution) => Err(NoSolution),
}
}
fn not_outlives_predicate(p: ty::Predicate<'_>) -> bool {
match p.kind().skip_binder() {
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(..))
| ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..)) => false,
ty::PredicateKind::Clause(ty::Clause::Trait(..))
| ty::PredicateKind::Clause(ty::Clause::Projection(..))
| ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
| ty::PredicateKind::AliasEq(..)
| ty::PredicateKind::WellFormed(..)
| ty::PredicateKind::ObjectSafe(..)
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::Subtype(..)
| ty::PredicateKind::Coerce(..)
| ty::PredicateKind::ConstEvaluatable(..)
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::TypeWellFormedFromEnv(..) => true,
}
}
|
