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::AtExt;
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)
21 try_normalize_mir_const_after_erasing_regions: |tcx, goal| {
22 try_normalize_after_erasing_regions(tcx, goal)
28 fn try_normalize_after_erasing_regions<'tcx, T: TypeFoldable<'tcx> + PartialEq + Copy>(
30 goal: ParamEnvAnd<'tcx, T>,
31 ) -> Result<T, NoSolution> {
32 let ParamEnvAnd { param_env, value } = goal;
33 tcx.infer_ctxt().enter(|infcx| {
34 let cause = ObligationCause::dummy();
35 match infcx.at(&cause, param_env).normalize(value) {
36 Ok(Normalized { value: normalized_value, obligations: normalized_obligations }) => {
37 // We don't care about the `obligations`; they are
38 // always only region relations, and we are about to
39 // erase those anyway:
41 normalized_obligations.iter().find(|p| not_outlives_predicate(p.predicate)),
45 let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
46 // It's unclear when `resolve_vars` would have an effect in a
47 // fresh `InferCtxt`. If this assert does trigger, it will give
49 debug_assert_eq!(normalized_value, resolved_value);
50 let erased = infcx.tcx.erase_regions(resolved_value);
51 debug_assert!(!erased.needs_infer(), "{:?}", erased);
54 Err(NoSolution) => Err(NoSolution),
59 fn not_outlives_predicate<'tcx>(p: ty::Predicate<'tcx>) -> bool {
60 match p.kind().skip_binder() {
61 ty::PredicateKind::RegionOutlives(..) | ty::PredicateKind::TypeOutlives(..) => false,
62 ty::PredicateKind::Trait(..)
63 | ty::PredicateKind::Projection(..)
64 | ty::PredicateKind::WellFormed(..)
65 | ty::PredicateKind::ObjectSafe(..)
66 | ty::PredicateKind::ClosureKind(..)
67 | ty::PredicateKind::Subtype(..)
68 | ty::PredicateKind::Coerce(..)
69 | ty::PredicateKind::ConstEvaluatable(..)
70 | ty::PredicateKind::ConstEquate(..)
71 | ty::PredicateKind::TypeWellFormedFromEnv(..) => true,