1 use rustc_infer::infer::TyCtxtInferExt;
2 use rustc_middle::traits::query::NoSolution;
3 use rustc_middle::ty::query::Providers;
4 use rustc_middle::ty::{self, ParamEnvAnd, TyCtxt, TypeFoldable};
5 use rustc_trait_selection::traits::query::normalize::QueryNormalizeExt;
6 use rustc_trait_selection::traits::{Normalized, ObligationCause};
7 use std::sync::atomic::Ordering;
9 pub(crate) fn provide(p: &mut Providers) {
11 try_normalize_generic_arg_after_erasing_regions: |tcx, goal| {
12 debug!("try_normalize_generic_arg_after_erasing_regions(goal={:#?}", goal);
16 .normalize_generic_arg_after_erasing_regions
17 .fetch_add(1, Ordering::Relaxed);
19 try_normalize_after_erasing_regions(tcx, goal)
25 fn try_normalize_after_erasing_regions<'tcx, T: TypeFoldable<'tcx> + PartialEq + Copy>(
27 goal: ParamEnvAnd<'tcx, T>,
28 ) -> Result<T, NoSolution> {
29 let ParamEnvAnd { param_env, value } = goal;
30 let infcx = tcx.infer_ctxt().build();
31 let cause = ObligationCause::dummy();
32 match infcx.at(&cause, param_env).query_normalize(value) {
33 Ok(Normalized { value: normalized_value, obligations: normalized_obligations }) => {
34 // We don't care about the `obligations`; they are
35 // always only region relations, and we are about to
36 // erase those anyway:
37 // This has been seen to fail in RL, so making it a non-debug assertion to better catch
40 normalized_obligations.iter().find(|p| not_outlives_predicate(p.predicate)),
44 let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
45 // It's unclear when `resolve_vars` would have an effect in a
46 // fresh `InferCtxt`. If this assert does trigger, it will give
48 debug_assert_eq!(normalized_value, resolved_value);
49 let erased = infcx.tcx.erase_regions(resolved_value);
50 debug_assert!(!erased.needs_infer(), "{erased:?}");
53 Err(NoSolution) => Err(NoSolution),
57 fn not_outlives_predicate(p: ty::Predicate<'_>) -> bool {
58 match p.kind().skip_binder() {
59 ty::PredicateKind::Clause(ty::Clause::RegionOutlives(..))
60 | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..)) => false,
61 ty::PredicateKind::Clause(ty::Clause::Trait(..))
62 | ty::PredicateKind::Clause(ty::Clause::Projection(..))
63 | ty::PredicateKind::WellFormed(..)
64 | ty::PredicateKind::ObjectSafe(..)
65 | ty::PredicateKind::ClosureKind(..)
66 | ty::PredicateKind::Subtype(..)
67 | ty::PredicateKind::Coerce(..)
68 | ty::PredicateKind::ConstEvaluatable(..)
69 | ty::PredicateKind::ConstEquate(..)
70 | ty::PredicateKind::Ambiguous
71 | ty::PredicateKind::TypeWellFormedFromEnv(..) => true,