gcc/testsuite/g++.old-deja/g++.jason/overload1.C

// { dg-do assemble  }
// Bug: g++ thinks there is a conversion from void * to B *.

struct A {
  operator void* ();
};

struct B: public A { };

void bar (A& a) {
  B* bp = (B*)a;		// { dg-error "11:invalid cast" } 
}