assertThat(onlyPresent).containsExactly(2);
  }

  private static Optional<Integer> getSomeOptionalInt() {
    return Optional.of(1);
  }

  private static FluentIterable<? extends Number> getSomeNumbers() {
    return FluentIterable.from(ImmutableList.<Number>of());
  }

  /*
   * The following tests demonstrate the shortcomings of or() and test that the casting workaround

   *
   * {@snippet :
   * Optional<Integer> optionalInt = getSomeOptionalInt();
   * Number value = optionalInt.or(0.5); // error
   *
   * FluentIterable<? extends Number> numbers = getSomeNumbers();
   * Optional<? extends Number> first = numbers.first();
   * Number value = first.or(0.5); // error
   * }
   *
   * <p>As a workaround, it is always safe to cast an {@code Optional<? extends T>} to {@code

   *
   * {@snippet :
   * Optional<Integer> optionalInt = getSomeOptionalInt();
   * Number value = optionalInt.or(0.5); // error
   *
   * FluentIterable<? extends Number> numbers = getSomeNumbers();
   * Optional<? extends Number> first = numbers.first();
   * Number value = first.or(0.5); // error
   * }
   *
   * <p>As a workaround, it is always safe to cast an {@code Optional<? extends T>} to {@code