single expression helper for compile-time enforced constexpr function evaluation possible?

Question

@cyberpunk_ is trying to achieve something and made some questions about it but all the chase boils down to this:

Is it possible to build a tool to enforce compile-ti

Answer 1

Use std::integral_constant:

int x = std::integral_constant::value;
f(std::integral_constant::value);

This code will not compile if g(n) is not evaluated at compile-time.