How to automatically convert strongly typed enum into int?
As others have said, you can’t have an implicit conversion, and that’s by-design. If you want you can avoid the need to specify the underlying type in the cast. template <typename E> constexpr typename std::underlying_type<E>::type to_underlying(E e) noexcept { return static_cast<typename std::underlying_type<E>::type>(e); } std::cout << foo(to_underlying(b::B2)) << std::endl;