C ++ check types at compile time

Question

I read the Bjarne Stroustrup FAQ in C ++ and read about type parameter restrictions and how to force certain restrictions to be applied at compile time without getting ridiculous template errors, and appeared in this example:

 template<class T1, class T2> 
    struct Can_copy {
        static void constraints(T1 a, T2 b) { T2 c = a; b = a; }
        Can_copy() { 
            void(*p)(T1, T2) = constraints;
        }
    };

However, I'm not quite sure how this shows up at compile time? What is the use of constraint assignment for a function pointer? Is this a kind of implicit constraint call?

Sorry if this is an obvious question, literally only read C ++ for two days, but had experience in other languages.

Answer 1

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