error[E0308]: mismatched types
  --> $DIR/issue-29084.rs:4:13
   |
LL |         bar(&mut $d);
   |             ^^^^^^^ expected `u8`, found `&mut u8`
...
LL |     foo!(0u8);
   |     ---------- in this macro invocation

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.