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Unbreak upcasting

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This commit is contained in:
Michael Goulet 2022-11-10 23:49:42 +00:00
parent 6e6c49e7ce
commit 4f978dbaf9
2 changed files with 7 additions and 3 deletions
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4
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
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@ -779,7 +779,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
match (source.kind(), target.kind()) {
// Trait+Kx+'a -> Trait+Ky+'b (upcasts).
(&ty::Dynamic(ref data_a, _, ty::Dyn), &ty::Dynamic(ref data_b, _, ty::Dyn)) => {
(&ty::Dynamic(ref data_a, _, dyn_a), &ty::Dynamic(ref data_b, _, dyn_b))
if dyn_a == dyn_b =>
{
// Upcast coercions permit several things:
//
// 1. Dropping auto traits, e.g., `Foo + Send` to `Foo`

6
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View File

@ -919,7 +919,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let mut nested = vec![];
match (source.kind(), target.kind()) {
// Trait+Kx+'a -> Trait+Ky+'b (auto traits and lifetime subtyping).
(&ty::Dynamic(ref data_a, r_a, ty::Dyn), &ty::Dynamic(ref data_b, r_b, ty::Dyn)) => {
(&ty::Dynamic(ref data_a, r_a, dyn_a), &ty::Dynamic(ref data_b, r_b, dyn_b))
if dyn_a == dyn_b =>
{
// See `assemble_candidates_for_unsizing` for more info.
// We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
let iter = data_a
@ -938,7 +940,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.map(ty::Binder::dummy),
);
let existential_predicates = tcx.mk_poly_existential_predicates(iter);
let source_trait = tcx.mk_dynamic(existential_predicates, r_b, ty::Dyn);
let source_trait = tcx.mk_dynamic(existential_predicates, r_b, dyn_a);
// Require that the traits involved in this upcast are **equal**;
// only the **lifetime bound** is changed.