fn describe(x: &dyn std::any::Any) {
    match x {
        x if x.is::<i32>() => {
            if let Some(val) = x.downcast_ref::<i32>() {
                match val {
                    1 => println!("one"),
                    2 => println!("two"),
                    _ => println!("an integer"),
                }
            }
        }
        x if x.is::<&str>() => {
            println!("a string");
        }
        _ => {
            println!("something else");
        }
    }
}

fn main() {
    describe(&1);
    describe(&2);
    describe(&"hello");
    describe(&vec![1, 2, 3]);
}