overriding virtual function return type differs and is not covariant

Question

Ah, SO came back just in time.

I am getting a strange error:

 \'B::blah\': overriding virtual function return type differs and is not covariant from          


        

Answer 1

The blah method have to return A::Inner in all cases -- if you think of the reason it is quite simple. A instance of B could easily be case to the base class A. Now if anybody calls blah on A (the base class which object should it return? Inner2 or Inner?