error[E0505]: cannot move out of `x` because it is borrowed
  --> $DIR/borrowck-unary-move.rs:3:10
   |
LL | fn foo(x: Box<isize>) -> isize {
   |        - binding `x` declared here
LL |     let y = &*x;
   |             --- borrow of `*x` occurs here
LL |     free(x);
   |          ^ move out of `x` occurs here
LL |     *y
   |     -- borrow later used here
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL -     let y = &*x;
LL +     let y = &x.clone();
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0505`.