[Rust] Borrowing demo (with error)

fn main() {
    let mut v = vec![1, 2, 3];

    // Try to modify vec in-place
    square_each(& v);

    println!("{}", v[1]);
}

fn square_each(v: & Vec<i32>) {
    for e in v.iter_mut() {
        *e = (*e) * (*e);
    }
}