C++ Multiple Inheritance : Function Mismatch?

C++ won't allow me to construct an object of type SymIntPoly and call f() on it. Below are the classes and the structure.

template<typename T>
struct SymPoly
{
    T f() { retu this->x; }
};

struct IntPoly
{
    int x;
    virtual int f() = 0;
};

struct SymIntPoly : public IntPoly, public SymPoly<int>
{
};

I do not know about compilers, but I feel that the compiler does not treat the two functions as the same functions (ie. they do not have the same inteal signature?)

The use case is that SymPoly