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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::subst::GenericArg;
use rustc_middle::ty::{self, ParamEnvAnd, TyCtxt, TypeFoldable};
use rustc_trait_selection::traits::query::normalize::AtExt;
use rustc_trait_selection::traits::{Normalized, ObligationCause};
use std::sync::atomic::Ordering;
crate fn provide(p: &mut Providers) {
*p = Providers { normalize_generic_arg_after_erasing_regions, ..*p };
}
fn normalize_generic_arg_after_erasing_regions<'tcx>(
tcx: TyCtxt<'tcx>,
goal: ParamEnvAnd<'tcx, GenericArg<'tcx>>,
) -> GenericArg<'tcx> {
debug!("normalize_generic_arg_after_erasing_regions(goal={:#?})", goal);
let ParamEnvAnd { param_env, value } = goal;
tcx.sess.perf_stats.normalize_generic_arg_after_erasing_regions.fetch_add(1, Ordering::Relaxed);
tcx.infer_ctxt().enter(|infcx| {
let cause = ObligationCause::dummy();
match infcx.at(&cause, param_env).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:
debug_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);
erased
}
Err(NoSolution) => bug!("could not fully normalize `{:?}`", value),
}
})
}
fn not_outlives_predicate(p: &ty::Predicate<'tcx>) -> bool {
match p.skip_binders() {
ty::PredicateAtom::RegionOutlives(..) | ty::PredicateAtom::TypeOutlives(..) => false,
ty::PredicateAtom::Trait(..)
| ty::PredicateAtom::Projection(..)
| ty::PredicateAtom::WellFormed(..)
| ty::PredicateAtom::ObjectSafe(..)
| ty::PredicateAtom::ClosureKind(..)
| ty::PredicateAtom::Subtype(..)
| ty::PredicateAtom::ConstEvaluatable(..)
| ty::PredicateAtom::ConstEquate(..)
| ty::PredicateAtom::TypeWellFormedFromEnv(..) => true,
}
}
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