error: invalid fragment specifier `foo` --> $DIR/macro-invalid-fragment-spec.rs:2:6 | LL | ($x:foo) => () | ^^^^^^ | = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis` error: aborting due to 1 previous error