error[E0502]: cannot borrow `*ptr` as immutable because it is also borrowed as mutable
  --> $DIR/borrowck-closures-use-after-free.rs:22:8
   |
LL |   let mut test = |foo: &Foo| {
   |                  ----------- mutable borrow occurs here
LL |     ptr = box Foo { x: ptr.x + 1 };
   |                        --- first borrow occurs due to use of `ptr` in closure
LL |   };
LL |   test(&*ptr);
   |   ---- ^^^^^ immutable borrow occurs here
   |   |
   |   mutable borrow later used by call

error: aborting due to previous error

For more information about this error, try `rustc --explain E0502`.