concept Bla {
  new Ref<Bla> ref;
}

svoid test_cset_with_Ref() {
  Bla a = unlisted Bla();
  Bla b = unlisted Bla();
  cset(a, ref := b);
  assertSame(a.ref!, b);
  assertEqualsVerbose(ll(a), findBackRefs Bla(b));
  cset(a, ref := null);
  assertNull(a.ref!); // make sure the Ref object itself is not deleted
  assertEqualsVerbose(ll(), findBackRefs Bla(b)); // test that back ref is gone
}