static void assertNotEqualsVerbose(O x, O y) {
  assertNotEqualsVerbose((S) null, x, y);
}

static void assertNotEqualsVerbose(S msg, O x, O y) {
  if (eq(x, y))
    fail((msg != null ? msg + ": " : "") + (x));
  else
    print("OK: " + (y) + " != " + (x));
}