{"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"(&ty::Alias(ty::Opaque,"}]}
            (&ty::Alias(ty::Opaque, ..), _) => (a, enable_subtyping(b, true)?),
        let (a, b) = match (a.kind(), b.kind()) {
            (_, &ty::Alias(ty::Opaque, ..)) => (enable_subtyping(a, false)?, b),