Template Specialization with Template for Static Function - c++

Question

I have a template that inherits from another template, with itself as the second template's template parameter. The inherited template defines a static function:
template<class T> class A
{
public:
static void foo();
};
template<class T> class B : public A<B>
{
};
Now I want to implement the static function for the class A specialized with B, but with B not specialized. But I can't figure out how to declare the template. I'm not even sure if this is possible. My first try was:
template<class T> void A<B<T>>::foo()
{
}
But this gives the error:
"Nested name specifier 'A<B<T>>::" for declaration does not refer into a class, class template or class template partial specialization"
I've tried different things like adding "template<>" in front but none of those worked. I am able to compile this:
template<> void A<B<int>>::foo()
{
}
As well as this:
template<class T> void A<T>::foo()
{
}
Is this an attempt at partial specialization? My first impression is no (there are no templates with multiple parameters where I want to specialize one of them). Rather, I want to specialize a template with another template that is not specialized. Is this possible, and if so what is the proper syntax?

Answer 1

This is indeed partial specialization. You cannot partially specialize just a method, you must partially specialize the whole class. See this answer. You might try implementing foo in a separate helper struct and partially specializing that struct instead.
Here is an example using a helper struct.
#include <iostream>
template<class T> struct t_helper
{
static void foo()
{
std::cout << "Not B<T>\n";
}
};
template<class T> class A
{
public:
static void foo() {
t_helper<T>::foo();
}
};
template<class T> class B {};
// Specialize the behavior of A<T>::foo() for all B types
template<class T>
struct t_helper<B<T>>
{
static void foo()
{
std::cout << "Is B<T>\n";
}
};
int main()
{
A<int>::foo(); // Prints "Not B<T>\n"
A<B<int>>::foo(); // Prints "Is B<T>\n"
return 0;
}