Rust pop Cons list

use crate::List::{Cons, Nil};

#[derive(Debug)]
enum List {
    Cons(i32, Box<List>),
    Nil,
}

fn main() {
    let mut list = Cons(1, Box::new(Cons(2, Box::new(Cons(3, Box::new(Nil))))));

    println!("The first value is: {}.", list.pop().unwrap());
    println!("The second value is: {}.", list.pop().unwrap());
}

impl List {
    fn pop(&mut self) -> Option<i32> {
        let old_list = (self, Nil);
        match old_list {
            Cons(value, tail) => {
                *self = *tail;
                Some(value)
            }
            Nil => None,
        }
    }
}