How to use generic template function to handle objects with different members?

I have looked around a while for a solution to this, however, I might not know the exact definition or language syntax of what I am trying to accomplish, so I decided to post.

I have certain objects/structs like so:

struct A
{
  char myChar;
  bool hasArray = false;
};

template <uint8_t ARRAY_LEN>
struct AA : public A
{
  hasArray = true;
  uint8_t myArray[ARRAY_LEN];
};

I want to create a generic function that can take in both of these object types and to perform common work as well as specific work for the derived struct AA. Something like the following:

template <typename T>
void func(T (&m)) 
{
  if (T.hasArray)
  {
    // do some processing with m.myArray
    std::cout << sizeof(m.myArray) << std::endl;
    // ...
  }
  // common processing
  std::cout << "myChar: " << m.myChar << std::endl;
};

I want to be able to call the function like so:

A a;
AA aa;
func(a);   // compiler error, this would not work as no array member
func(aa);  // this works

Granted this is just an example that illustrates my intent, but it sums up what I would like to do. The actual code is a lot more complex and involved many more objects. I know I can overload, but I want to know if there is a way to do it with one generic function? Also note that I understand why the compiler complains with the sample code I would like to know if there is a workaround or some other c++ functionality that I am missing. I would not like to do any type casting... - Using c++11 and GCC 4.8.5