Conversion, operator overloading

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Hello all,

recently I got a problem related to conversion and operator overloading.
With the code below

class A {};
A operator +(const A& lhs, const A& rhs) { ... };

class B {
public:
    operator A() { ... }
    operator int() { ... }
};

int main() {
    B ba, bb;
    ba + bb; // error

    short val = (short) ba;

    return 0;
}

I got the error from gcc:
error: ambiguous overload for ?operator+? in ?ba + bb?
note: candidates are: operator+(int, int) <built-in>
note: A operator+(const A&, const A&)

I'm wondering how I can get rid of the error. Specifically, how can I
make the compiler not consider the built-in type when considering
operator overloading? The code in main is sort of legacy code, and can't
be changed, but we are free to play with class A and B.

Thanks,
TS

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