Function to_string

11.11-usingEnum1/main.cpp:14–24

#if __cpp_using_enum
constexpr std::string_view to_string(Permission permission)
{
  switch(permission) {
    using enum Permission;  // #A New use of using
    case Read: return "Read";
    case Write: return "Write";
    case Execute: return "Execute";
  }

  return "unknown";
}

int main()
{