* That statement compiles only if {@link FluentIterable#concat concat(aIterable, bIterable)}
   * returns a {@link FluentIterable} of elements of an anonymous type whose supertypes are the <a
   * href="https://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.9">intersection</a> of
   * the supertypes of {@code A} and the supertypes of {@code B}.
   */