#![allow(bad_style, unused)]#![warn(unused_must_use)]

use ::core::{any::Any, fmt::Debug};

trait MyAny : Any + 'static {
    /// trait method (!= an inherent method of dyn Any)
    fn downcast_ref_Foo (self: &'_ Self)
      -> Option<&'_ Foo>
    ;
}
impl MyAny for Foo
{
    fn downcast_ref_Foo (self: &'_ Self)
      -> Option<&'_ Foo>
    {
        Some(self)
    }
}

#[derive(Debug)]
struct Foo {
    bar: u8
}

trait Component : MyAny + Debug {}

impl Component for Foo {}

fn main ()
{
    let foo: Box<dyn Component> = Box::new(Foo { bar: 0 });
    let x: Option<&Foo> = foo.downcast_ref_Foo();

    println!("{:?}", foo);
    println!("{:?}", x);
}