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Allow dropping dyn principal

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This commit is contained in:
Michael Goulet 2023-08-09 00:31:26 +00:00 • committed by Maybe Lapkin
parent 3a85d3fa78
commit e3800a1a04
10 changed files with 83 additions and 35 deletions
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2
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
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@ -1018,7 +1018,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// #2 (region bounds).
let principal_def_id_a = a_data.principal_def_id();
let principal_def_id_b = b_data.principal_def_id();
if principal_def_id_a == principal_def_id_b {
if principal_def_id_a == principal_def_id_b || principal_def_id_b.is_none() {
// We may upcast to auto traits that are either explicitly listed in
// the object type's bounds, or implied by the principal trait ref's
// supertraits.

4
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -1153,6 +1153,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
let iter = data_a
.principal()
.filter(|_| {
// optionally drop the principal, if we're unsizing to no principal
data_b.principal().is_some()
})
.map(|b| b.map_bound(ty::ExistentialPredicate::Trait))
.into_iter()
.chain(