4 #![allow(unused_variables)]
5 #![feature(box_syntax)]
7 use std::io::{self, Write};
13 #[derive(Copy, Clone)]
19 impl Trait for Struct {
25 fn foo(mut a: Box<dyn Write>) {}
28 let a = Struct { x: 1, y: 2 };
29 let b: Box<dyn Trait> = Box::new(a);
31 let c: &dyn Trait = &a;
34 let out = io::stdout();