Unimplemented core issue 1769: Catching a thrown derived class by reference to base clas

Core 1769, involving a resolution which states that derived classes can be thrown and caught by catch clauses denoting an unambiguous base, has not been implemented. #include <assert.h> struct BaseClass {     int i;     BaseClass() : i(0) { }     BaseClass(int ii) : i(ii) { }     BaseClass(const BaseClass& r) : i(r.i) { } }; class DerivedClass : BaseClass {     int ib;   public:     DerivedClass(const DerivedClass& r) : BaseClass(r.ib), ib(r.ib) { }     DerivedClass(const BaseClass&) : BaseClass(999), ib(999) { }     DerivedClass(int ii); }; DerivedClass thrown_base (1); DerivedClass::DerivedClass(int ii) : BaseClass(ii), ib(ii) { } int main() {     try {         throw thrown_base;         return 999;     }     catch(const BaseClass &k) { }     catch(...) { assert(false); } // Assertion fails at runtime due to core issue 1769     return 0; }