deref.rs

use std::ops::Deref;

struct T {
    x: isize,
}

impl T {
    fn from(x: isize) -> Self {
        T { x }
    }
}

impl Deref for T {
    type Target = isize;

    fn deref(&self) -> &isize {
        &self.x
    }
}

fn print_num(v: &isize) {
    println!("{}", v);
}

fn main() {
    let t = T::from(42);
    print_num(&t);
}