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Don't try to add nested predicate to Rustdoc auto-trait ParamEnv

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Fixes #80233

We already have logic in `evaluate_predicates` that tries to add
unimplemented predicates to our `ParamEnv`. Trying to add a predicate
that already holds can lead to errors later on, since projection
will prefer trait candidates from the `ParamEnv` to predicates from an
impl.
This commit is contained in:
Aaron Hill 2020-12-20 21:07:13 -05:00
parent b0e5c7d1fe
commit f2d7c05db0
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2 changed files with 41 additions and 6 deletions
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10
compiler/rustc_trait_selection/src/traits/auto_trait.rs
View file

@ -642,12 +642,10 @@ impl AutoTraitFinder<'tcx> {
let bound_predicate = predicate.bound_atom();
match bound_predicate.skip_binder() {
ty::PredicateAtom::Trait(p, _) => {
if self.is_param_no_infer(p.trait_ref.substs)
&& !only_projections
&& is_new_pred
{
self.add_user_pred(computed_preds, predicate);
}
// Add this to `predicates` so that we end up calling `select`
// with it. If this predicate ends up being unimplemented,
// then `evaluate_predicates` will handle adding it the `ParamEnv`
// if possible.
predicates.push_back(bound_predicate.rebind(p));
}
ty::PredicateAtom::Projection(p) => {