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Don't resolve generic instances if they may be shadowed by dyn

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This commit is contained in:
Michael Goulet 2023-08-21 22:39:34 +00:00
parent 55ce976e06
commit a30ad3a5a6
8 changed files with 144 additions and 20 deletions
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25
compiler/rustc_ty_utils/src/instance.rs
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@ -141,11 +141,34 @@ fn resolve_associated_item<'tcx>(
false
}
};
if !eligible {
return Ok(None);
}
// HACK: We may have overlapping `dyn Trait` built-in impls and
// user-provided blanket impls. Detect that case here, and return
// ambiguity.
//
// This should not affect totally monomorphized contexts, only
// resolve calls that happen polymorphically, such as the mir-inliner
// and const-prop (and also some lints).
let self_ty = rcvr_args.type_at(0);
if !self_ty.is_known_rigid() {
let predicates = tcx
.predicates_of(impl_data.impl_def_id)
.instantiate(tcx, impl_data.args)
.predicates;
let sized_def_id = tcx.lang_items().sized_trait();
// If we find a `Self: Sized` bound on the item, then we know
// that `dyn Trait` can certainly never apply here.
if !predicates.into_iter().filter_map(ty::Clause::as_trait_clause).any(|clause| {
Some(clause.def_id()) == sized_def_id
&& clause.skip_binder().self_ty() == self_ty
}) {
return Ok(None);
}
}
// Any final impl is required to define all associated items.
if !leaf_def.item.defaultness(tcx).has_value() {
let guard = tcx.sess.delay_span_bug(