Auto merge of #98264 - compiler-errors:missing-arg-placeholder, r=jackh726

Make missing argument placeholder more obvious that it's a placeholder

Use `/* ty */` instead of `{ty}`, since people might be misled into thinking that this is valid syntax, and not just a diagnostic placeholder.

Fixes #96880

compiler/rustc_typeck/src/check/fn_ctxt/checks.rs

@@ -955,8 +955,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let input_ty = self.resolve_vars_if_possible(expected_ty);
                         if input_ty.is_unit() {
                             "()".to_string()
+                        } else if !input_ty.is_ty_var() {
+                            format!("/* {} */", input_ty)
                         } else {
-                            format!("{{{}}}", input_ty)
+                            "/* value */".to_string()
                         }
                     };
                     suggestion += &suggestion_text;