Function Formatter

12.19-constevalParmCheck1/main.cpp:122–146

template<typename T, class... Args>
constexpr void Formatter(string&          buffer,
                         std::string_view v,
                         const T&         t,
                         const Args&... args)
{
  using PT = std::remove_cv_t<T>;

  if constexpr(std::is_same_v<int, PT>) {
    if('d' != v[0]) { throw int{3}; }
    buffer.append(itoa(t));

  } else if constexpr(std::is_convertible_v<PT, std::string_view>) {
    if('s' != v[0]) { throw int{4}; }
    buffer.append(t);

  } else {
    throw int{6};
  }

  v.remove_prefix(1);

  if constexpr(sizeof...(Args) > 0) {
    Formatter<Args...>(buffer, v, args...);
  }
}

template<class... Args>
struct basic_format_string {