error[E0597]: `z` does not live long enough
  --> $DIR/issue-46471-1.rs:4:9
   |
LL |         let mut z = 0;
   |             ----- binding `z` declared here
LL |         &mut z
   |         ^^^^^^ borrowed value does not live long enough
LL |     };
   |     - `z` dropped here while still borrowed

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0597`.