foreigner_class!(class Boo {
    self_type Boo;
    constructor create_boo() -> Arc<Mutex<Boo>>;
    method Boo::test(&self, _: bool) -> f32;
    method Boo::set_a(&mut self, _: i32);
});

foreigner_class!(class Moo {
    self_type Moo;
    constructor TestPathAndResult::empty() -> Result<Moo, String>;
    method TestPathAndResult::get_boo(&self) -> Arc<Mutex<Boo>>; alias getBoo;
});