problems with polymorphism and inheritance with templates

This code:

template<class T>
class Foo
{
public:
    T* member;
};

class Base
{
};

typedef Foo<Base> BaseFoo;

class Derived
{
};

typedef Foo<Derived> DerivedFoo;

int main(int argc, char** argv)
{
    DerivedFoo* dfoo = new DerivedFoo();
    BaseFoo* bfoo = dfoo;
    return 0;
}

doesn't compile, the compiler says "cannot convert ?DerivedFoo*? to
?BaseFoo*? in initialization". How can I fix it? Of course, this one works:

    Derived* derived = new Derived();
    Base* base = derived;

I know that something similiar (but not really the same) is possible,
because shared_ptr can do it, e.g. this one compiles with g++ 4.3.2:

#include <tr1/memory>

using namespace std::tr1;

class Base
{
};

typedef shared_ptr<Base> BasePtr;

class Derived : public Base
{
};

typedef shared_ptr<Derived> DerivedPtr;

int main(int argc, char** argv)
{
    DerivedPtr dptr(new Derived());
    BasePtr bptr = dptr;
    return 0;
}

--
Frank Buss, http://www.frank-buss.de
piano and more: http://www.youtube.com/user/frankbuss

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