demonstrate that plain cons moves the value it receives.

rust/pointers.rs

}
mod list_with_box {
    #[deriving(Show)]
    #[deriving(Clone, Show)]
    pub enum List<A> {
        Nil,
        Cons(A, Box<List<A>>)
        println!("\nlist_with_box:");
        let l: List<int> = cons(1, cons(2, Nil));
        // must be cloned before use as parameter to cons, which moves it
        let l2 = l.clone();
        println!("l = {}", l);
        println!("cons(3, l) = {:?}", cons(3, l));
        println!("cons(3, l)  = {:?}", cons(3, l));
        println!("cons(4, l2) = {:?}", cons(4, l2));
        // println!("cons_with_ref(3, &l) = {:?}", cons_with_ref(3, &l));
        //                                                        // ^    "use of moved value: `l`"