helper macro to convert applicable data into an auto_list equivalent

to_list.cpp

#include <utility>
#include <iterator>
#include <array>
#include <string_view>

//

template <auto...>
struct auto_list
{};

//

namespace detail
{
	template <auto S, auto... Is>
	auto constexpr to_list(std::index_sequence<Is...>)
	{ return auto_list<(*S)[Is]...>{}; }

	auto constexpr size(char const *const str)
	{
		auto i = std::size_t{};
		while (str[i] != '\0') ++i;
		return i;
	}
}

#define TO_LIST(var) \
[&]() \
{ \
	using detail::size; \
	using std::size; \
	static auto constexpr tmp = var; \
	return detail::to_list<&tmp>(std::make_index_sequence<size(var)>{}); \
}();

//

int main()
{
	auto list1 = TO_LIST("abc");
	static_assert(list1);

	auto constexpr str = "def";
	auto list2 = TO_LIST(str);
	static_assert(list2);

	auto constexpr arr = std::array{ 1, 2, 3 };
	auto list3 = TO_LIST(arr);	
	static_assert(list3);

	auto constexpr view = std::string_view{ "456" };
	auto list4 = TO_LIST(view);
	static_assert(list4);
}