foreign_class!(class DropCounter {
self_type DropCounter;
constructor DropCounter::default() -> DropCounter;
});
foreign_class!(class LongOperation {
self_type LongOperation;
constructor new(drop_counter: &DropCounter) -> LongOperation;
fn mf(&self, drop_counter: &DropCounter);
fn f(drop_counter: &DropCounter);
fn mf2(&self, drop_counter: &DropCounter) -> i32;
fn f2(drop_counter: &DropCounter) -> i32;
});