#include <array>

// globally:
template<typename T> 
using enum_traits = decltype(get_enum_traits(T{}));

// inside the macro:
#define DEFINE_ENUM(Name, ...) \
    /* define "enum class Name" ... */ \
    enum class Name { __VA_ARGS__ }; \
    struct Name##_type_traits { \
         static constexpr std::array<Name,1> values{{ Name{} }}; \
    }; \
    Name##_type_traits get_enum_traits(Name); // does not need implementation
    
    
namespace foo {
    DEFINE_ENUM(Foo, Value1, Value2);
}

int main( ) {
    for (auto e: enum_traits<foo::Foo>::values)
    {}
}