change usages of type_of to bound_type_of

compiler/rustc_trait_selection/src/traits/specialize/mod.rs

@@ -455,7 +455,13 @@ pub(crate) fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Opti
         w.push('>');
     }
 
-    write!(w, " {} for {}", trait_ref.print_only_trait_path(), tcx.type_of(impl_def_id)).unwrap();
+    write!(
+        w,
+        " {} for {}",
+        trait_ref.print_only_trait_path(),
+        tcx.bound_type_of(impl_def_id).subst_identity()
+    )
+    .unwrap();
 
     // The predicates will contain default bounds like `T: Sized`. We need to
     // remove these bounds, and add `T: ?Sized` to any untouched type parameters.