#![feature(nll)]

use std::cell::UnsafeCell;
use std::rc::Rc;

type Invariant<T> = UnsafeCell<T>;
type Covariant<T> = T;

type Wrapper<T> = Invariant<T>;
//type Wrapper<T> = Covariant<T>;

trait AsSelf<'slf> {
    type Ref: ?Sized;

    fn as_self(&'slf self) -> &Self::Ref;
}

struct Foo<'a>(Wrapper<&'a str>);

impl<'slf, 'd: 'slf> AsSelf<'slf> for Foo<'d> {
    type Ref = Foo<'slf>;

    fn as_self(&'slf self) -> &'d Self::Ref {
        self
    }
}