Is it possible to specialize a template using a member enum?

Question

struct Bar {
  enum { Special = 4 };
};

template struct Foo {};
template struct Foo {};

U

Answer 1

The type of a non-type template argument cannot depend on a template parameter of a partial specialization.

ISO C++03 14.5.4/9 says

A partially specialized non-type argument expression shall not involve a template parameter of the partial specialization except when the argument expression is a simple identifier.

template  struct A {};
template  struct A {}; //error
template  struct B {};
template  struct B {};     //OK

So something like this is illegal template struct Foo {}; because T::Special depends on T

The usage is also illegal. You have provided one template argument but you need to provide two.