enum Mylist {
  Empty,
  Cons(i32, std::rc::Rc<Mylist>)
}

impl Mylist {
  fn new() -> std::rc::Rc<Mylist>
  {
    std::rc::Rc::new(Mylist::Empty)
  }

  fn append(val: i32, l: std::rc::Rc<Mylist>) -> std::rc::Rc<Mylist>
  {
    std::rc::Rc::new(Mylist::Cons(val, l))
  }
}

impl Drop for Mylist {
  fn drop(&mut self)
  {
    if let Mylist::Cons(v, _) = self {
      println!("Node with value {} is being destroyed!", v) 
    } else {
      println!("An empty list is being destroyed!") 
    }
  }
}

fn main()
{
  let l1 = Mylist::new();
  let l2 = Mylist::append(6, l1.clone());

  {
    let l3 = Mylist::append(7, l2.clone());

    if let Mylist::Cons(v, _) = *l3 {
      println!("l3: {}", v);
    } else {
      println!("l3 is empty!") 
    }
  }

  if let Mylist::Cons(v, tail) = &*(l2.clone()) {
    println!("l2: {}", v);
    if let Mylist::Cons(v1, _) = &*tail.clone() {
      println!("l2's tail: {}", v1);
    } else {
      println!("l2's tail is empty!") 
    };
  } else {
    println!("l2 is empty!") 
  };
}