{"ast_node_type":"other","tokens":[{"end":80,"kind":"keyword","start":0,"text":"(_,"}]}
            (_, &ty::Alias(ty::Opaque, ..)) => (enable_subtyping(a, false)?, b),
            (&ty::Alias(ty::Opaque, ..), _) => (a, enable_subtyping(b, true)?),
            _ => unreachable!(