ref also doesn't work.

rust/pointers.rs

@@ -46,6 +46,7 @@ mod list_with_box {
    //         Nil => Cons(x, box Nil),
    //         _ => Cons(x, box *xs)
    //                       // ^    "cannot move out of dereference of `&`-pointer"
    //                       // same with `ref l => Cons(x, box *l)`
    //     }
    // }