No metaprogramming needed.
class A {
using XPtr = void (A::*)();
std::vector<XPtr> x_calls;
std::set<std::type_index> x_types;
template <typename B> void X() { ... }
public:
template <typename B> void M() {
bool is_new = x_types.insert(std::type_index(typeid(B))).second;
if (is_new)
x_calls.push_back(&A::X<B>);
...
}
void Z() {
for (auto&& ptr : x_calls) {
(this->*ptr)();
}
}
};