// run-pass



pub fn main() {
    let v: Vec<isize> = vec![10, 20];
    assert_eq!(v[0], 10);
    assert_eq!(v[1], 20);
    let mut x: usize = 0;
    assert_eq!(v[x], 10);
    assert_eq!(v[x + 1], 20);
    x = x + 1;
    assert_eq!(v[x], 20);
    assert_eq!(v[x - 1], 10);
}