Private conversion function leads to "ambiguous default conversion" error (C ++)

First, a tiny example demonstrating the problem:

struct Bar {
    enum Baz {aa, bb, cc};
    Baz baz_;

    operator Baz() const { return baz_; }
    private:
        template<typename T> operator T() const;
};

int main() {
    Bar bar;
    switch (bar) {
        case Bar::aa:
            break;
        case Bar::bb:
            break;
        case Bar::cc:
            break;
        default:
            break;
    }
    return 0;
}

Compiling this code with g ++ 4.7.0 gives the following error:

foo.cpp: In function ‘int main()’:
foo.cpp:12:16: error: ambiguous default type conversion from ‘Bar’
foo.cpp:12:16: error:   candidate conversions include ‘template<class T> Bar::operator T() const’

I understand that since the struct object is "enabled", the compiler will try to find the conversion function for an integer or enumerated type. I explicitly provide a public function to convert to the enum type Bar :: Baz and would like to use it.

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, ( 100%) g++ 4.6.

edit: , , .