struct stupidCastTest {
    float* data;

    operator float* () {
        return data;
    }

    float& operator [] (long idx) {
        return data[idx];
    }
}

int main () {
    stupidCastTest instance;
    instance.data = new float[10];
    instance[3] = 5; // by logic it would call the overloaded operator,
                     // but ISO says it is not clear whether it should
                     // call ((float*)instance)[3] or instance[3].
    return 0;
}