static <C extends Collection<S>> C assertDoesntContainIC(C c, S y) {
  ret assertDoesntContainIC(null, c, y);
}

static <C extends Collection<S>> C assertDoesntContainIC(S msg, C c, S y) {
  if (cic(c, y))
    fail((msg != null ? msg + ": " : "") + y + " contained in " + c);
  ret c;
}

ifclass Symbol
static <C extends Collection<Symbol>> C assertDoesntContainIC(C c, Symbol y) {
  ret assertDoesntContainIC(null, c, y);
}

static <C extends Collection<Symbol>> C assertDoesntContainIC(S msg, C c, Symbol y) {
  if (cic(c, y))
    fail((msg != null ? msg + ": " : "") + y + " contained in " + c);
  ret c;
}
endif

Began life as a copy of #1012661