My first sound unsafe code lol

i_can_write_unsafe_ma.rs

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

enum Either<T, U> {
    A(T),
    B(U),
}

impl<T, U> AsyncRead for Either<T, U>
where
    T: AsyncRead,
    U: AsyncRead,
{
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context,
        buf: &mut [u8],
    ) -> Poll<tokio::io::Result<usize>> {
        let either = unsafe { Pin::into_inner_unchecked(self) };
        match either {
            Either::A(reader) => {
                AsyncRead::poll_read(unsafe { Pin::new_unchecked(reader) }, cx, buf)
            }
            Either::B(reader) => {
                AsyncRead::poll_read(unsafe { Pin::new_unchecked(reader) }, cx, buf)
            }
        }
    }
}