type Counter {
    value: i32,
    fn increment(self: mutref<Self>) -> i32 {
        self.value = self.value + 1
        return self.value
    }
}

interface Incrementable<T: Type> {
    fn increment(self: mutref<T>) -> i32
}

fn bump<T: Incrementable<T>>(value: mutref<T>) -> i32 {
    return T.increment(value)
}

pub fn main(world: World) -> Void raises {
    var counter: Counter = Counter { value: 41 }
    if bump<Counter>(&mut counter) == 42 {
        check world.out.write("static interface mutref ok\n")
    } else {
        check world.out.write("static interface mutref broke\n")
    }
}