Differing return type for virtual functions

Question

A virtual function\'s return type should be the same type that is in base class, or covariant. But why do we have this restriction?

Answer 1

Because of the nonsense that would ensue:

struct foo
{
    virtual int get() const { return 0; }
};

struct bar : foo
{
    std::string get() const { return "this certainly isn't an int"; }
};

int main()
{
    bar b;
    foo* f = &b;

    int result = f->get(); // int, right? ...right?
}

It isn't sensible to have a derived class return something completely unrelated.