#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(phantom_variance_markers)]
use core::marker::{PhantomCovariant, variance};
struct BoundFn<F, P, R>
where
    F: Fn(P) -> R,
{
    function: F,
    parameter: P,
    return_value: PhantomCovariant<R>,
}
fn main() {
    let bound_fn = BoundFn {
        function: core::convert::identity,
        parameter: 5u8,
        return_value: variance(),
    };
}