use std::{
    pin::Pin,
    task::{Context, Poll},
};

trait FnOnce1 {
    type Output;
}

impl<T, R> FnOnce1 for T
where
    T: FnOnce() -> R,
{
    type Output = R;
}
struct Map<F>(F);

impl<F, T> Future for Map<F>
where
    F: FnOnce1<Output = T>,
{
    type Output = T;

    fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<T> {
        loop {}
    }
}

fn take_output<Fut: Future>(_: Pin<&mut Fut>) -> Fut::Output {
    loop {}
}

fn main() {
    let mut bazz = Map(async || ());
    let mut barr = async { Bazz {} };

    let mut _fut0 = unsafe { Pin::new_unchecked(&mut bazz) };
    let mut _fut1 = unsafe { Pin::new_unchecked(&mut barr) };
    || {
        take_output(_fut0.as_mut());
        take_output(_fut1.as_mut());
    };
}

// 1
// 2

#[derive(proc_macro_thing::MyMacro)]
#[helper]
struct Bazz {}