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

1 files changed, 4 insertions, 20 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index d542240be9b..013db2edb39 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -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 };
     }