Remove redundant check

Author: mu001999

compiler/rustc_passes/src/dead.rs

@@ -378,13 +378,16 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 }
                 hir::ItemKind::ForeignMod { .. } => {}
                 hir::ItemKind::Trait(..) => {
-                    // mark dependent traits live
                     for impl_def_id in self.tcx.all_impls(item.owner_id.to_def_id()) {
                         if let Some(local_def_id) = impl_def_id.as_local()
                             && let ItemKind::Impl(impl_ref) =
                                 self.tcx.hir().expect_item(local_def_id).kind
                         {
+                            // skip items
+                            // mark dependent traits live
                             intravisit::walk_generics(self, impl_ref.generics);
+                            // mark dependent parameters live
+                            intravisit::walk_path(self, impl_ref.of_trait.unwrap().path);
                         }
                     }
 
@@ -396,15 +399,16 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 // mark corresponing ImplTerm live
                 let def_id = trait_item.owner_id.to_def_id();
                 if let Some(trait_def_id) = self.tcx.trait_of_item(def_id) {
-                    // for assoc fn without self, mark the trait live
+                    // mark the trait live
                     self.check_def_id(trait_def_id);
 
                     for impl_def in self.tcx.all_impls(trait_def_id) {
                         if let Some(impl_def_id) = impl_def.as_local()
                             && let ItemKind::Impl(impl_ref) =
                                 self.tcx.hir().expect_item(impl_def_id).kind
                         {
-                            self.check_def_id(impl_def);
+                            // mark self_ty live
+                            intravisit::walk_ty(self, impl_ref.self_ty);
                             for impl_item in impl_ref.items {
                                 if Some(def_id) == impl_item.trait_item_def_id {
                                     self.check_def_id(impl_item.id.owner_id.to_def_id());