trait X<'a, T>
where
    for<'b> T: X<'b, T>,
    for<'b> <T as X<'b, T>>::U: Clone,
{
    type U: ?Sized;
    fn f(x: &<T as X<'_, T>>::U) {
        <<T as X<'_, T>>::U>::clone(x);
    }
}

impl<S, T> X<'_, (T,)> for (S,) {
    type U = str;
    //~^ ERROR the trait bound `str: Clone` is not satisfied
}

pub fn main() {
    <(i32,) as X<(i32,)>>::f("abc");
}