example:

#include <cstdio>

class Dummy {};

template<typename T>
class IsDummy { public: enum { Value = 0, }; };
template<>
class IsDummy<Dummy> { public: enum { Value = 1, }; };

template<typename T, int isDummy = IsDummy<T>::Value>
class Wrapper { };
template<typename T>
class Wrapper<T, 1> {
public:
    typedef T Value;
};

static void func(Dummy *) {}
static void func(const char *) {}

class Object0 {
public:
    template<typename T>
    operator T *(void) const {return NULL;}
};

class Object1 {
public:
    template<typename T>
    operator typename Wrapper<T>::Value *(void) const {return NULL;}
};

int main(int argc, char **argv)
{
    Object0 o0;
    func(o0);  // <= ambiguous
    Object1 o1;
    func(o1);  // <= no matching function
    return 0;
}

what i want to do:

• make func(o0) and func(o1) matches func(Dummy *) only (and any further class specialized by IsDummy<>), but not for func(const char *)
• compatible for cpp03 (which does not support partial specialization for functions (operator T() function) )

what happens:

• func(o0) would cause ambiguous
• func(o1) would cause no matching function