Also in the new solver

3 files changed, 27 insertions, 18 deletions

diff --git a/compiler/rustc_next_trait_solver/src/delegate.rs b/compiler/rustc_next_trait_solver/src/delegate.rs
index 4ba54a2e0bf..2d2d50e62f9 100644
--- a/compiler/rustc_next_trait_solver/src/delegate.rs
+++ b/compiler/rustc_next_trait_solver/src/delegate.rs
@@ -95,7 +95,10 @@ pub trait SolverDelegate: Deref<Target = <Self as SolverDelegate>::Infcx> + Size
         goal_trait_ref: ty::TraitRef<Self::Interner>,
         trait_assoc_def_id: <Self::Interner as Interner>::DefId,
         impl_def_id: <Self::Interner as Interner>::DefId,
-    ) -> Result<Option<<Self::Interner as Interner>::DefId>, NoSolution>;
+    ) -> Result<
+        Option<<Self::Interner as Interner>::DefId>,
+        <Self::Interner as Interner>::ErrorGuaranteed,
+    >;
 
     fn is_transmutable(
         &self,
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index 8c74490e0e0..91ad24bff67 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -950,7 +950,7 @@ where
         goal_trait_ref: ty::TraitRef<I>,
         trait_assoc_def_id: I::DefId,
         impl_def_id: I::DefId,
-    ) -> Result<Option<I::DefId>, NoSolution> {
+    ) -> Result<Option<I::DefId>, I::ErrorGuaranteed> {
         self.delegate.fetch_eligible_assoc_item(goal_trait_ref, trait_assoc_def_id, impl_def_id)
     }
 
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
index f5ecfea5408..76cbe5758b2 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
@@ -244,20 +244,7 @@ where
                     .map(|pred| goal.with(cx, pred)),
             );
 
-            // In case the associated item is hidden due to specialization, we have to
-            // return ambiguity this would otherwise be incomplete, resulting in
-            // unsoundness during coherence (#105782).
-            let Some(target_item_def_id) = ecx.fetch_eligible_assoc_item(
-                goal_trait_ref,
-                goal.predicate.def_id(),
-                impl_def_id,
-            )?
-            else {
-                return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
-            };
-
-            let error_response = |ecx: &mut EvalCtxt<'_, D>, msg: &str| {
-                let guar = cx.delay_bug(msg);
+            let error_response = |ecx: &mut EvalCtxt<'_, D>, guar| {
                 let error_term = match goal.predicate.alias.kind(cx) {
                     ty::AliasTermKind::ProjectionTy => Ty::new_error(cx, guar).into(),
                     ty::AliasTermKind::ProjectionConst => Const::new_error(cx, guar).into(),
@@ -267,8 +254,24 @@ where
                 ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
             };
 
+            // In case the associated item is hidden due to specialization, we have to
+            // return ambiguity this would otherwise be incomplete, resulting in
+            // unsoundness during coherence (#105782).
+            let target_item_def_id = match ecx.fetch_eligible_assoc_item(
+                goal_trait_ref,
+                goal.predicate.def_id(),
+                impl_def_id,
+            ) {
+                Ok(Some(target_item_def_id)) => target_item_def_id,
+                Ok(None) => {
+                    return ecx
+                        .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
+                }
+                Err(guar) => return error_response(ecx, guar),
+            };
+
             if !cx.has_item_definition(target_item_def_id) {
-                return error_response(ecx, "missing item");
+                return error_response(ecx, cx.delay_bug("missing item"));
             }
 
             let target_container_def_id = cx.parent(target_item_def_id);
@@ -292,7 +295,10 @@ where
             )?;
 
             if !cx.check_args_compatible(target_item_def_id, target_args) {
-                return error_response(ecx, "associated item has mismatched arguments");
+                return error_response(
+                    ecx,
+                    cx.delay_bug("associated item has mismatched arguments"),
+                );
             }
 
             // Finally we construct the actual value of the associated type.