#[derive(Debug)]
struct Testing {
    v: Vec<i32>
}

fn sub(a: Box<Testing>) {
    println!("sub: {:?}", a);
}

fn main() {
    let y = Testing{v: vec![1,2,3]};
    let x = Box::new(y);
    sub(x);
    // Can't reference x after here.
    println!("main: {:?}", y);
}