3 files changed, 26 insertions, 13 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 270b90fa6b2..120545c8e5d 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -722,7 +722,14 @@ pub(super) fn check_specialization_validity<'tcx>(
     let result = opt_result.unwrap_or(Ok(()));
 
     if let Err(parent_impl) = result {
-        report_forbidden_specialization(tcx, impl_item, parent_impl);
+        if !tcx.is_impl_trait_in_trait(impl_item) {
+            report_forbidden_specialization(tcx, impl_item, parent_impl);
+        } else {
+            tcx.sess.delay_span_bug(
+                DUMMY_SP,
+                format!("parent item: {:?} not marked as default", parent_impl),
+            );
+        }
     }
 }
 
@@ -1485,7 +1492,9 @@ fn opaque_type_cycle_error(
                 }
 
                 for closure_def_id in visitor.closures {
-                    let Some(closure_local_did) = closure_def_id.as_local() else { continue; };
+                    let Some(closure_local_did) = closure_def_id.as_local() else {
+                        continue;
+                    };
                     let typeck_results = tcx.typeck(closure_local_did);
 
                     let mut label_match = |ty: Ty<'_>, span| {
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 97a3e01c52a..acd0bcd8e5c 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -22,7 +22,7 @@ use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_session::lint;
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 use std::fmt;
 
 use crate::errors;
@@ -338,7 +338,17 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
 
                 Scope::TraitRefBoundary { .. } => {
                     // We should only see super trait lifetimes if there is a `Binder` above
-                    assert!(supertrait_bound_vars.is_empty());
+                    // though this may happen when we call `poly_trait_ref_binder_info` with
+                    // an (erroneous, #113423) associated return type bound in an impl header.
+                    if !supertrait_bound_vars.is_empty() {
+                        self.tcx.sess.delay_span_bug(
+                            DUMMY_SP,
+                            format!(
+                                "found supertrait lifetimes without a binder to append \
+                                them to: {supertrait_bound_vars:?}"
+                            ),
+                        );
+                    }
                     break (vec![], BinderScopeType::Normal);
                 }
 
diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index 49aee6b59a2..066e7449189 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -7,7 +7,7 @@ use rustc_arena::DroplessArena;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, CrateVariancesMap, ImplTraitInTraitData, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
 use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
 use std::ops::ControlFlow;
 
@@ -59,13 +59,6 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
         DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder => {
             return variance_of_opaque(tcx, item_def_id);
         }
-        DefKind::AssocTy => {
-            if let Some(ImplTraitInTraitData::Trait { .. }) =
-                tcx.opt_rpitit_info(item_def_id.to_def_id())
-            {
-                return variance_of_opaque(tcx, item_def_id);
-            }
-        }
         _ => {}
     }
 
@@ -125,7 +118,8 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
                 // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) check whether this is necessary
                 // at all for RPITITs.
                 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                    if self.tcx.is_impl_trait_in_trait(*def_id) =>
+                    if self.tcx.is_impl_trait_in_trait(*def_id)
+                        && !self.tcx.lower_impl_trait_in_trait_to_assoc_ty() =>
                 {
                     self.visit_opaque(*def_id, substs)
                 }