concept __IndirectlyReadableImpl = // exposition only
    requires(const In in) {
      typename std::iter_value_t<In>;
      typename std::iter_reference_t<In>;
      typename std::iter_rvalue_reference_t<In>;
      { *in } -> std::same_as<std::iter_reference_t<In>>;
      { ranges::iter_move(in) } -> std::same_as<std::iter_rvalue_reference_t<In>>;
    } &&
    std::common_reference_with<
      std::iter_reference_t<In>&&, std::iter_value_t<In>&
    > &&
    std::common_reference_with<
      std::iter_reference_t<In>&&, std::iter_rvalue_reference_t<In>&&
    > &&
    std::common_reference_with<
      std::iter_rvalue_reference_t<In>&&, const std::iter_value_t<In>&

>;