#![feature(box_syntax,unboxed_closures)] fn to_fn_mut>(f: F) -> F { f } fn to_fn_once>(f: F) -> F { f } pub fn main() { let bar: Box<_> = box 3; let _g = to_fn_mut(|| { let _h = to_fn_once(move || -> isize { *bar }); //~ ERROR cannot move out of }); }