error: in expressions, `_` can only be used on the left-hand side of an assignment --> $DIR/underscore.rs:6:9 | LL | _ | ^ `_` not allowed here | ::: $DIR/main.rs:5:5 | LL | underscore!(); | ------------- in this macro invocation | = note: this error originates in the macro `underscore` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error