#![deny(bare_trait_objects, elided_lifetimes_in_paths)]

use ::std::*;

struct Callback /* = */ (
    Box<dyn FnMut() + 'static>,
);

impl Callback {
    #[inline]
    fn new (callback: impl FnMut() + 'static) -> Self
    {
        Self(Box::new(callback))
    }

    #[allow(non_snake_case)]
    #[inline]
    fn as_FnMut (self: &'_ mut Self) -> &'_ mut (dyn FnMut() + 'static)
    {
        ops::DerefMut::deref_mut(self)
    }
}

impl ops::Deref for Callback {
    type Target = dyn FnMut() + 'static;

    #[inline]
    fn deref (self: &'_ Self) -> &'_ Self::Target
    {
        &*self.0
    }
}

impl ops::DerefMut for Callback {
    #[inline]
    fn deref_mut (self: &'_ mut Self) -> &'_ mut Self::Target
    {
        &mut *self.0
    }
}

fn test (callback: &'_ mut Callback)
{
    let callback = callback.as_FnMut();

    callback();
    callback();
    callback();
    (&mut *callback)();
}

fn main ()
{
    let mut callback = {
        let mut cnt = 0;
        Callback::new(move || {
            cnt += 1;
            println!("Test {}", cnt);
        })
    };
    test(&mut callback);
}