#![feature(box_syntax)] fn f(mut y: Box) { *y = 5; assert_eq!(*y, 5); } fn g() { let frob = |mut q: Box| { *q = 2; assert_eq!(*q, 2); }; let w = box 37; frob(w); } pub fn main() { let z = box 17; f(z); g(); }