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Descriptive error when users try to combine RPITIT/AFIT with specialization

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This commit is contained in:
Michael Goulet 2023-02-28 02:03:26 +00:00
parent 6290ae92b2
commit ecac8fd5af
7 changed files with 83 additions and 65 deletions
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24
compiler/rustc_trait_selection/src/traits/project.rs
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@ -1307,25 +1307,8 @@ fn assemble_candidate_for_impl_trait_in_trait<'cx, 'tcx>(
let _ = selcx.infcx.commit_if_ok(|_| {
match selcx.select(&obligation.with(tcx, trait_predicate)) {
Ok(Some(super::ImplSource::UserDefined(data))) => {
let Ok(leaf_def) = specialization_graph::assoc_def(tcx, data.impl_def_id, trait_fn_def_id) else {
return Err(());
};
// Only reveal a specializable default if we're past type-checking
// and the obligation is monomorphic, otherwise passes such as
// transmute checking and polymorphic MIR optimizations could
// get a result which isn't correct for all monomorphizations.
if leaf_def.is_final()
|| (obligation.param_env.reveal() == Reveal::All
&& !selcx
.infcx
.resolve_vars_if_possible(obligation.predicate.trait_ref(tcx))
.still_further_specializable())
{
candidate_set.push_candidate(ProjectionCandidate::ImplTraitInTrait(data));
Ok(())
} else {
Err(())
}
candidate_set.push_candidate(ProjectionCandidate::ImplTraitInTrait(data));
Ok(())
}
Ok(None) => {
candidate_set.mark_ambiguous();
@ -2216,7 +2199,8 @@ fn confirm_impl_trait_in_trait_candidate<'tcx>(
Ok(assoc_ty) => assoc_ty,
Err(guar) => return Progress::error(tcx, guar),
};
if !leaf_def.item.defaultness(tcx).has_value() {
// We don't support specialization for RPITITs anyways... yet.
if !leaf_def.is_final() {
return Progress { term: tcx.ty_error_misc().into(), obligations };
}