member method for specific class

main.cpp

#include <iostream>
#include <type_traits>

class Foo;
class Bar;

class API {
public:
    template<typename T>
    void call(const T &obj) {
        static_assert(std::is_same<Foo, T>::value, "allow only Foo");
        printf("api call\n");
    }
};

class Foo {
public:
    void call() {
        API api;
        api.call(*this);
    }
    
};


class Bar {
    void call() {
        API api;
        // compile fail, if not commented
        api.call(*this);
    }
};


int main()
{
    printf("member method for specific class\n");
    return 0;
}