type L2<'a, 'b> = fn(&'a ()) -> &'b ();
fn foo<'a>(x: L2<'a, 'static>) -> L2<'static, 'a> {
    x
}
fn bar<'a: 'b, 'b>(x: L2<'a, 'a>) -> L2<'static, 'b> {
    x
}