Don't add a note for implementing a trait if its inner type is erroneous

1 files changed, 20 insertions, 15 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 515f3a34988..8835f2cc1b9 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -371,23 +371,28 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
                     if !candidate_set.ambiguous && no_candidates_apply {
                         let trait_ref = stack.obligation.predicate.skip_binder().trait_ref;
-                        let self_ty = trait_ref.self_ty();
-                        let (trait_desc, self_desc) = with_no_trimmed_paths!({
-                            let trait_desc = trait_ref.print_only_trait_path().to_string();
-                            let self_desc = if self_ty.has_concrete_skeleton() {
-                                Some(self_ty.to_string())
+                        if !trait_ref.references_error() {
+                            let self_ty = trait_ref.self_ty();
+                            let (trait_desc, self_desc) = with_no_trimmed_paths!({
+                                let trait_desc = trait_ref.print_only_trait_path().to_string();
+                                let self_desc = if self_ty.has_concrete_skeleton() {
+                                    Some(self_ty.to_string())
+                                } else {
+                                    None
+                                };
+                                (trait_desc, self_desc)
+                            });
+                            let cause = if let Conflict::Upstream = conflict {
+                                IntercrateAmbiguityCause::UpstreamCrateUpdate {
+                                    trait_desc,
+                                    self_desc,
+                                }
                             } else {
-                                None
+                                IntercrateAmbiguityCause::DownstreamCrate { trait_desc, self_desc }
                             };
-                            (trait_desc, self_desc)
-                        });
-                        let cause = if let Conflict::Upstream = conflict {
-                            IntercrateAmbiguityCause::UpstreamCrateUpdate { trait_desc, self_desc }
-                        } else {
-                            IntercrateAmbiguityCause::DownstreamCrate { trait_desc, self_desc }
-                        };
-                        debug!(?cause, "evaluate_stack: pushing cause");
-                        self.intercrate_ambiguity_causes.as_mut().unwrap().insert(cause);
+                            debug!(?cause, "evaluate_stack: pushing cause");
+                            self.intercrate_ambiguity_causes.as_mut().unwrap().insert(cause);
+                        }
                     }
                 }
             }