// Recursive type using boxes
enum List {
    Cons(i32, Box<List>),
    Nil,
}

struct MyBox<T>(T);

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> {
        MyBox(x)
    }
}

use std::ops::Deref;

impl<T> Deref for MyBox<T> {
    type Target = T;

    fn deref(&self) -> &T {
        &self.0
    }
}

fn main() {
    // Storing `i32` value on heap
    let b = Box::new(5);
    println!("b = {}", b);

    use crate::List::{Cons, Nil};
    let list = Cons(1, Box::new(Cons(2, Box::new(Cons(3, Box::new(Nil))))));

    // Dereferencing
    let x = 5;
    let y = &x;

    assert_eq!(5, x);
    assert_eq!(5, *y);

    let x = 5;
    let y = Box::new(x);

    assert_eq!(5, x);
    assert_eq!(5, *y);

    let x = 5;
    let y = MyBox::new(x);

    assert_eq!(5, x);
    assert_eq!(5, *y); // `*y` is equivalent to `*(y.deref())`

    fn hello(name: &str) {
        println!("Hello, {}", name);
    }

    // Deref coercion
    let m = MyBox::new(String::from("Rust"));
    // `&MyBox<String>` -> `&String` -> `&str`
    hello(&m);
    // `m`: MyBox<String>, `*m`: String, `(*m)[..]`: str, `&(*m)[..]`: &str
    hello(&(*m)[..]);
}