error[E0499]: cannot borrow `x` as mutable more than once at a time
   --> $DIR/issue-11715.rs:100:18
    |
99  |     let y = &mut x;
    |                  - first mutable borrow occurs here
100 |     let z = &mut x;
    |                  ^ second mutable borrow occurs here
101 | }
    | - first borrow ends here

error: aborting due to previous error