Re: Conversion operators and private inheritance

Hello,
I`ve run into situation when conversion operator to the parent class
provided by the child class (private inheritance is used) is not found by
compiler. Consider the following example :

class A {};
class B : public A {};
class C : private B {
public:
    // By default, "A" base class is not available for the
    // outside non-friend classes and functions. Make it accessible
    // for others
    operator A& () {return *this;}};

void doSomething (const A&) {}

int main (int argc, char** argv){
    C instC;
    // Attempt 1, most obvious. causes compiler error
    doSomething (instC.operator A&());
    // Attempt 2. Causes compiler error
    doSomething (instC);
    // Attempt 3. Fine
    doSomething (instC.C::operator A&());
    return 0;

}

Compiler output (gcc 4.4.1) :

gcc_private_inheritance.cpp: In function ?int main(int, char**)?:
gcc_private_inheritance.cpp:2: error: ?class A? is inaccessible
gcc_private_inheritance.cpp:13: error: within this context
gcc_private_inheritance.cpp:15: error: ?A? is an inaccessible base of ?C

Let`s don`t discuss the sanity of this inheritance scheme / need for
conversion operator :)

So can anyone explain why conversion operator is not found in (1) and (2) ?