{"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"(ty::Contravariant,"}]}
        (ty::Contravariant, ty::Contravariant) => ty::Contravariant,
        // Otherwise, co + co = co, contra + contra = contra.
        (ty::Covariant, ty::Covariant) => ty::Covariant,