how to create specialization of method inherited from class template instantiation-CodePudding

I have a base class template and a class deriving from an instantiation of it:

template<typename T>
class Bar
{
   template <T t>
   void Foo();
};

class Derived : public Bar<int> {};

How should one implement Derived::Foo<0>() for example? when trying this out:

template<>
void Derived::Foo<0>() { /* impl.. */}

i get the following compile error:

template-id 'Foo<0>' for 'Derived::Foo()' does not match any template declaration.

CodePudding user response：

You cannot specialize it in the descendant; you can only add a signature that'll serve as an overload and delegate as necessary:

template<typename T>
class Bar
{
   template <T t>
   void Foo();
};

class Derived : public Bar<int> {
   using Base = Bar<int>;

   template <int t>
   void Foo()
   {
      if constexpr(t == 0) {
         /* impl... */
      } else {
         Base::Foo<t>();
      }
   }
};

Since the ADL / Koenig lookup of a class does not include template base class(es), I'd not expect any issues during overload resolution if you do it this way.