struct Foo<'a, 'b: 'a>(&'a &'b ());
impl<'a, 'b> Foo<'a, 'b> {
fn xmute(a: &'b ()) -> &'a () {
unreachable!()
}
pub fn foo<'a, 'b>(u: &'b ()) -> &'a () {
Foo::xmute(u) //~ ERROR lifetime may not live long enough
fn main() {}