The answer is being debated at the moment in c++ papers and building on experience from other languages with extensive compile time evaluators like D. One thing that is happening is that we will get compile time exceptions (a paper for that is aiming to add this to the language in c++29 has come out) which may help us in reporting problems. Which will be important as there is also a lot of papers and talk about an extension of reflection allowing for better output generation which as far as I know was deferred until reflection had been accepted.

But there is also good news that with the advent of JIT like components for compile time evaluation in progress and the like of CLion having the beginnings of a compile debugger in combination with concepts there is a chance some help is available and on the way.

However right now you have to rely on compiler errors and static_asserts which is not ideal of course.