The result of the following code I think should print “FUNC_TYPE::TYPE1 A&& “, but it doesn’t。And it reported an error。

“Error LNK2019: Unresolved external symbol ‘public: void* __cdecl A::dispatch<0, int, class A>(int, class A)’ (??dispatch@dispatch@0A@HVA@@@A@@QEAAPEAXHV0@@Z)”

#include <iostream>
enum class FUNC_TYPE {
    TYPE1,
    TYPE2
};
class A {
public:
    template<FUNC_TYPE type, typename... T>
    static void* __dispatch(A* a, T&& ...t) {
        return a->dispatch<type,T...>(std::forward<T>(t)...);
    }

    template<FUNC_TYPE tag, typename... T>
    void* dispatch(T... t);
};
template<>
void* A::dispatch<FUNC_TYPE::TYPE1>(int i, A&& a) {
    std::cout << "FUNC_TYPE::TYPE1 A&& " << i << std::endl;
    return nullptr;
}
template<>
void* A::dispatch<FUNC_TYPE::TYPE1>(int i, A& a) {
    std::cout << "FUNC_TYPE::TYPE1 A& " << i << std::endl;
    return nullptr;
}
A get() {
    return A();
}
int main() {
    A a;
    A::__dispatch<FUNC_TYPE::TYPE1>(&a, 1, get());
}

What changes need to be made to ensure it works correctly?

And this is C++. Which concept does this pertain to? Are there any recommended materials for further reading?