struct Lock{
	private{
		field _:NoDrop;
		field _:NoCopy;
	}

	method enter(self:out Lock){
		*self = {};
	}

	method leave(self:in Lock){
		unsafe{
			drop(*self);
		}
	}

}




function foo(){
	var lock:Lock;

	lock.enter();

	lock.leave();
}