> But C++20 adds support for enum classes It seems to work fine with `enum class` under C++11 ? your code works almost inchanged in g++ 4.7. I don't see anythi

> But C++20 adds support for enum classes It seems to work fine with `enum class` under C++11 ? your code works almost inchanged in g++ 4.7. I don't see anything here : https://en.cppreference.com/w/cpp/language/template_parameters#Non-type_template_parameter https://en.cppreference.com/w/cpp/language/template_paramete... that adds specific support for that in C++20