error[E0308]: mismatched types --> $DIR/issue-12997-2.rs:8:1 | LL | fn bar(x: isize) { } | ^^^^^^^^^^^^^^^^^^^^ expected `isize`, found `&mut Bencher` | = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error For more information about this error, try `rustc --explain E0308`.