error[E0507]: cannot move out of captured outer variable in an `FnMut` closure
  --> $DIR/borrowck-move-by-capture.rs:9:29
   |
LL |     let bar: Box<_> = box 3;
   |         --- captured outer variable
LL |     let _g = to_fn_mut(|| {
LL |         let _h = to_fn_once(move || -> isize { *bar });
   |                             ^^^^^^^^^^^^^^^^ cannot move out of captured outer variable in an `FnMut` closure

error: aborting due to previous error

For more information about this error, try `rustc --explain E0507`.