std::basic_format_args::get(C++20)

basic_format_arg<Context>
  get(std::size_t i) const noexcept; // (1) C++20
constexpr basic_format_arg<Context>
  get(std::size_t i) const noexcept; // (1) C++26

namespace std {
  template<class Context>
  class basic_format_args {
    std::size_t size_;
    const basic_format_arg<Context>* data_;

  public:
    basic_format_arg<Context> get(std::size_t i) const noexcept
    {
      return i < size_ ? data_[i] : basic_format_arg<Context>();
    }
  };
}