Small clean up of E0277 message logic

Author: estebank

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -4769,21 +4769,15 @@ pub(super) fn get_explanation_based_on_obligation<'tcx>(
         } else {
             String::new()
         };
-        match ty_desc {
-            Some(desc) => format!(
-                "{}the trait `{}` is not implemented for {} `{}`{post}",
-                pre_message,
-                trait_predicate.print_modifiers_and_trait_path(),
-                desc,
-                tcx.short_ty_string(trait_ref.skip_binder().self_ty(), &mut None),
-            ),
-            None => format!(
-                "{}the trait `{}` is not implemented for `{}`{post}",
-                pre_message,
-                trait_predicate.print_modifiers_and_trait_path(),
-                tcx.short_ty_string(trait_ref.skip_binder().self_ty(), &mut None),
-            ),
-        }
+        let desc = match ty_desc {
+            Some(desc) => format!(" {desc}"),
+            None => String::new(),
+        };
+        format!(
+            "{pre_message}the trait `{}` is not implemented for{desc} `{}`{post}",
+            trait_predicate.print_modifiers_and_trait_path(),
+            tcx.short_ty_string(trait_ref.skip_binder().self_ty(), &mut None),
+        )
     }
 }