Invalid explicitly-specified argument for template parameter which is constexpr

Question

I have a static_loop construct like this

template  void static_loop(F&& f) {
    static_assert(n <= 8 &a         


        

Answer 1

Change

template 
constexpr size_t tupleSize(T) { return tuple_size_v; }

to:

template 
constexpr size_t tupleSize(T const&) { return tuple_size_v; }

That is, take the argument by reference to const, not by value. As-is, you're trying to copy a non-constexpr tuple in a constant expression - that can't work. By reference is fine since you're not actually reading the tuple.