src/test/run-pass/writealias.rs

// -*- rust -*-
type point = {x: int, y: int, mut z: int};

fn f(p: &mut point) { p.z = 13; }

fn main() {
    let mut x: point = {x: 10, y: 11, mut z: 12};
    f(&mut x);
    assert (x.z == 13);
}