C++ - circular dependence (using inner type of subclass in templated base class)

Question

I run into problem with circular dependence in a templated class. There is a code sample:

template <typename T> struct A 
{
  typedef typename T::C D;
  //typename T::C c;
};

struct B : public A<B>
{
  struct C {};
};

When I try to instantiate B, I get a compiler error: 'C' is not a member of 'B' (MSVC) or Invalid use of incomplete type 'struct B' (GCC).
What is the best way to change the sample to get it to work?

Answer 1

struct B_base { struct C {}; };
strucr B : A<B_base>, B_base { };