{"ast_node_type":"other","tokens":[{"end":95,"kind":"keyword","start":0,"text":"assert_eq!(a,"}]}
        assert_eq!(a, b); // we are misusing TypeRelation here; both LHS and RHS ought to be ==
    ) -> RelateResult<'tcx, ty::Region<'tcx>> {
        self.record_variance(a, self.ambient_variance);