{"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"///"}]}
    /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
    /// empty lifetime with a universe -- the idea is that we don't
    /// Therefore, the `'empty` in a universe `U` is less than all