MSVC support

[HDAKFD]

Apparently this doesn't work on MSVC.

Did u test it on MSVC back then when you created this since now it does not work. I checked that COUNTER works just fine but the fameta::counter can't get past the start index with any given number.

MSVC:

LLVM Clang:

Code for that:

[mittorn]

I've immplemented same counter, but compatible with msvc.
It uses same method as unconstexpr-cpp20, but works in most of c++17 compilers (gcc7+, clang5+, all c++17 msvc versions)

template <typename T>
struct Counter
{
	template <int I>
	struct Flag
	{
		template<typename F>
		friend constexpr bool Check(Flag, F);
	};

	template<int I>
	struct MarkFlag
	{
		template<typename F>
		friend constexpr bool Check(Flag<I>, F) { return false; }
	};

	template <int I, typename F, bool = Check(Flag<I>{}, F{})>
	constexpr static bool IsMarked(int) { return true; }

	template <int I, typename F>
	constexpr static bool IsMarked(float) { return false; }

	template <typename F>  struct WrapT{};

	template<typename F, int I = 0>
	constexpr static  int Inc()
	{
		if constexpr (IsMarked<I, WrapT<F>>(0)) return Inc<F, I+1>();
		else return I + sizeof(MarkFlag<I>) - 1;
	};

};

// use lambda as unique type
#define CounterInc(T) []{constexpr auto unq = []{}; return Counter<T>::Inc<decltype(unq)>();}()

This does not generate warnings for non-template friend injection
I using lambda for unique identifier, this targets c++17. Maybe this will work on pre-c++17 compilers with unique types or line constants if replace Inc() by SFINAE
Main difference is passing unique type to friend injection template and splitting flag check from increment
I have not implemented binary search, but hope it's possible