// Creating a stack closure which references a box and then // transferring ownership of the box before invoking the stack // closure results in a crash. fn twice(x: Box<usize>) -> usize { *x * 2 } fn invoke<F>(f: F) where F: FnOnce() -> usize { f(); } fn main() { let x : Box<usize> = Box::new(9); let sq = || { *x * *x }; twice(x); //~ ERROR: cannot move out of invoke(sq); }