error[E0503]: cannot use `x` because it was mutably borrowed
  --> $DIR/borrowck-non-exhaustive.rs:12:11
   |
LL |     let y = &mut x;
   |             ------ `x` is borrowed here
LL |     match x {
   |           ^ use of borrowed `x`
...
LL |     drop(y);
   |          - borrow later used here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0503`.