rust borrow and move

extern crate core;#[deriving(Show)]
struct Foo {
    f : Box<int>
}fn main(){
    let mut a = Foo {f: box 0};
    let y : &Foo;    // out(&a);
    {
        let b = Foo {f: box 10};
        // b does not live long enough
        // can not y = &b;        let  c = & mut a;        // a borrowed by c
        //a.f = box 11;        // c moved by y
        y = c;        println!("{}", c.f);        // cannot move out of `c` because it is borrowed
        //let c1 = c;
    }
    //a.f = box 11;
    println!("{}", y.f);
}fn out(v: &Foo) {
    // borrow
    println!("{}", v);
}fn test2(){
    let mut a:  Box<int> = box 1;
    // shared borrow
    let b = &a;
    let c = b;
    println!("{}", *b);
}