62 lines
2.6 KiB
Rust
62 lines
2.6 KiB
Rust
use rustc_infer::infer::TyCtxtInferExt;
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use rustc_middle::traits::query::NoSolution;
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::subst::GenericArg;
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use rustc_middle::ty::{self, ParamEnvAnd, TyCtxt, TypeFoldable};
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use rustc_trait_selection::traits::query::normalize::AtExt;
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use rustc_trait_selection::traits::{Normalized, ObligationCause};
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use std::sync::atomic::Ordering;
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crate fn provide(p: &mut Providers) {
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*p = Providers { normalize_generic_arg_after_erasing_regions, ..*p };
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}
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fn normalize_generic_arg_after_erasing_regions<'tcx>(
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tcx: TyCtxt<'tcx>,
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goal: ParamEnvAnd<'tcx, GenericArg<'tcx>>,
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) -> GenericArg<'tcx> {
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debug!("normalize_generic_arg_after_erasing_regions(goal={:#?})", goal);
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let ParamEnvAnd { param_env, value } = goal;
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tcx.sess.perf_stats.normalize_generic_arg_after_erasing_regions.fetch_add(1, Ordering::Relaxed);
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tcx.infer_ctxt().enter(|infcx| {
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let cause = ObligationCause::dummy();
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match infcx.at(&cause, param_env).normalize(value) {
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Ok(Normalized { value: normalized_value, obligations: normalized_obligations }) => {
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// We don't care about the `obligations`; they are
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// always only region relations, and we are about to
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// erase those anyway:
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debug_assert_eq!(
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normalized_obligations.iter().find(|p| not_outlives_predicate(&p.predicate)),
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None,
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);
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let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
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// It's unclear when `resolve_vars` would have an effect in a
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// fresh `InferCtxt`. If this assert does trigger, it will give
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// us a test case.
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debug_assert_eq!(normalized_value, resolved_value);
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let erased = infcx.tcx.erase_regions(resolved_value);
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debug_assert!(!erased.needs_infer(), "{:?}", erased);
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erased
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}
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Err(NoSolution) => bug!("could not fully normalize `{:?}`", value),
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}
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})
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}
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fn not_outlives_predicate(p: &ty::Predicate<'tcx>) -> bool {
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match p.skip_binders() {
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ty::PredicateAtom::RegionOutlives(..) | ty::PredicateAtom::TypeOutlives(..) => false,
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ty::PredicateAtom::Trait(..)
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| ty::PredicateAtom::Projection(..)
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| ty::PredicateAtom::WellFormed(..)
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| ty::PredicateAtom::ObjectSafe(..)
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| ty::PredicateAtom::ClosureKind(..)
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| ty::PredicateAtom::Subtype(..)
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| ty::PredicateAtom::ConstEvaluatable(..)
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| ty::PredicateAtom::ConstEquate(..)
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| ty::PredicateAtom::TypeWellFormedFromEnv(..) => true,
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}
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}
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