fn main() {
    let u = {x: 10, y: @{a: 20}};
    let mut {x: x, y: @{a: a}} = u;
    x = 100;
    a = 100;
    assert (x == 100);
    assert (a == 100);
    assert (u.x == 10);
    assert (u.y.a == 20);
}