import time

struct St {
mut:
    a int
}

fn (shared x St) f(shared y St, shared z St) {
    for _ in 0 .. 101 {
        lock x, y {
            tmp := y.a
            y.a = x.a
            x.a = tmp
        }
    }
    lock z {
        z.a--
    }
}

fn test_shared_receiver_lock() {
    shared x := &St{
        a: 5
    }
    shared y := &St{
        a: 7
    }
    shared z := &St{
        a: 1
    }
    spawn x.f(shared y, shared z)
    for _ in 0 .. 100 {
        lock x, y {
            tmp := x.a
            x.a = y.a
            y.a = tmp
        }
    }
    // the following would be a good application for a channel
    for finished := false; true; {
        rlock z {
            finished = z.a == 0
        }
        if finished {
            break
        }
        time.sleep(100 * time.millisecond)
    }
    rlock x, y {
        assert x.a == 7 && y.a == 5
    }
}