The following code doesn't compile.

struct A {};
struct B {};
class Base
{
public:
   virtual void method( A param ) { }
   virtual void method( B param ) = 0;
};

class Derived : public Base
{
public:
   //using Base::method;
   void method( B param ) { }
};

int main()
{
   Derived derived;
   derived.method(A());
}

The compiler can't find the overload of method() that has an A parameter. The 'fix' is to add a using declaration in the derived class. My question is why. What is the rational for a weird language rule like this?

I verified the error in both GCC and Comeau, so I assume this isn't a compiler bug but a feature of the language. Comeau at least gives me this warning:

"ComeauTest.c", line 10: warning: overloaded virtual function "Base::method" is
          only partially overridden in class "Derived"
  class Derived : public Base
        ^