#[derive(PartialEq, Eq, Hash)]
pub struct Key<T> {
    user_data: usize,
    _p: std::marker::PhantomData<fn(T)>,
}
impl<T> Unpin for Key<T> {}
impl<T> Clone for Key<T> {
    fn clone(&self) -> Self {
        *self
    }
}
impl<T> Copy for Key<T> {}
impl<T> Key<T> {
    pub unsafe fn new(user_data: usize) -> Self {
        Self {
            user_data,
            _p: std::marker::PhantomData,
        }
    }
}
impl<T> std::ops::Deref for Key<T> {
    type Target = usize;
    fn deref(&self) -> &Self::Target {
        &self.user_data
    }
}
impl<T> std::fmt::Debug for Key<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Key({})", self.user_data)
    }
}