tag example

tag.cpp

struct Class1
{
    using Tag = Tag1;
};

struct Class1B
{
    using Tag = Tag1;
};


struct Class2
{
    using Tag = Tag2;
};

template<typename T>
void f(T obj)
{
    f_impl(T::Tag, obj);
}

template<typename T>
void f_impl(Tag1, T obj)
{
}

template<typename T>
void f_impl(Tag2, T obj)
{
}