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use crate::infer::InferCtxt;
use crate::traits::query::evaluate_obligation::InferCtxtExt;
use crate::traits::{ObligationCause, PredicateObligation};
use rustc_infer::traits::TraitEngine;
use rustc_middle::ty::{self, ToPredicate};
pub(crate) fn update<'tcx, T>(
engine: &mut T,
infcx: &InferCtxt<'tcx>,
obligation: &PredicateObligation<'tcx>,
) where
T: TraitEngine<'tcx>,
{
// (*) binder skipped
if let ty::PredicateKind::Trait(tpred) = obligation.predicate.kind().skip_binder()
&& let Some(ty) = infcx.shallow_resolve(tpred.self_ty()).ty_vid().map(|t| infcx.root_var(t))
&& infcx.tcx.lang_items().sized_trait().map_or(false, |st| st != tpred.trait_ref.def_id)
{
let new_self_ty = infcx.tcx.types.unit;
let trait_ref = ty::TraitRef {
substs: infcx.tcx.mk_substs_trait(new_self_ty, &tpred.trait_ref.substs[1..]),
..tpred.trait_ref
};
// Then construct a new obligation with Self = () added
// to the ParamEnv, and see if it holds.
let o = rustc_infer::traits::Obligation::new(
ObligationCause::dummy(),
obligation.param_env,
obligation
.predicate
.kind()
.rebind(
// (*) binder moved here
ty::PredicateKind::Trait(ty::TraitPredicate {
trait_ref,
constness: tpred.constness,
polarity: tpred.polarity,
})
)
.to_predicate(infcx.tcx),
);
// Don't report overflow errors. Otherwise equivalent to may_hold.
if let Ok(result) = infcx.probe(|_| infcx.evaluate_obligation(&o)) && result.may_apply() {
engine.relationships().entry(ty).or_default().self_in_trait = true;
}
}
if let ty::PredicateKind::Projection(predicate) = obligation.predicate.kind().skip_binder() {
// If the projection predicate (Foo::Bar == X) has X as a non-TyVid,
// we need to make it into one.
if let Some(vid) = predicate.term.ty().and_then(|ty| ty.ty_vid()) {
debug!("relationship: {:?}.output = true", vid);
engine.relationships().entry(vid).or_default().output = true;
}
}
}
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