The following code is (in my mind, at least) valid and should not generate
any errors:

#include <iostream>
#include <iomanip>

using namespace std;

template <typename T>
class Outer
{
public:
    class Inner
    {
    public:
        Inner();
    };
};

template <typename T>
Outer<T>::Inner::Inner()
{
    cout << "Inner constructor" << endl;
}

template <typename T>
class Derived : public Outer<T>::Inner
{
public:
    Derived();
};

template <typename T>
Derived<T>::Derived()
: Outer<T>::Inner()
{
    cout << "Derived constructor" << endl;
}

int main()
{
    Derived<int> obj;
    return 0;
}

Contrary to *my* beliefs, however, Visual C++ 6.0 SP3 complains that
Outer<int>::Inner::Inner() is an unresolved external reference.

Curiously, the above code compiles and links if I move the definition of
Outer<int>::Inner::Inner() inside the class declaration (as opposed to
defining it externally, as I have above). The code also compiles if the
classes are not defined by templates.

So is my code correct and Visual C++ wrong (my theory) -- or is there some
subtle secret about deriving from classes declared inside templates?

- Scott Robert Ladd


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