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Rollup merge of #114828 - compiler-errors:next-solver-probe-upcasting, r=lcnr

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Probe when assembling upcast candidates so they don't step on eachother's toes in new solver

Lack of a probe causes one candidate to disqualify the other due to inference side-effects.

r? lcnr
This commit is contained in:
Guillaume Gomez 2023-08-15 14:29:49 +02:00 • committed by GitHub
commit 47bdda2b45
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4 changed files with 27 additions and 13 deletions
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22
compiler/rustc_trait_selection/src/solve/trait_goals.rs
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@ -552,16 +552,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
self.walk_vtable(
a_principal.with_self_ty(tcx, a_ty),
|ecx, new_a_principal, _, vtable_vptr_slot| {
if let Ok(resp) = ecx.consider_builtin_upcast_to_principal(
goal,
a_data,
a_region,
b_data,
b_region,
Some(new_a_principal.map_bound(|trait_ref| {
ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
})),
) {
if let Ok(resp) = ecx.probe_candidate("dyn upcast").enter(|ecx| {
ecx.consider_builtin_upcast_to_principal(
goal,
a_data,
a_region,
b_data,
b_region,
Some(new_a_principal.map_bound(|trait_ref| {
ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
})),
)
}) {
responses
.push((resp, BuiltinImplSource::TraitUpcasting { vtable_vptr_slot }));
}