// { dg-do compile }// GROUPS passed old-aborttypedef int element;class Pix {public:    Pix();    Pix(const Pix&);    // Friend functions so that v == x works as does x == v works    friend int operator==(void *v, const Pix& x) // { dg-error "previously" }    { return v == index; }  // { dg-error "from this location" }    // ??? should be operator!=    friend int operator==(void *v, const Pix& x) // { dg-error "redefinition" }    { return v != index; }private://    friend class List<T>;    element *index; // { dg-error "invalid use of non-static data member" }};