@VisibleForTesting
  static UUnionType create(UExpression... typeAlternatives) {
    return create(ImmutableList.copyOf(typeAlternatives));
  }
@Test
  public void serialization() {
    SerializableTester.reserializeAndAssert(
        UUnionType.create(
            UClassIdent.create("java.lang.IllegalArgumentException"),
            UClassIdent.create("java.lang.IllegalStateException")));
  }