// We need to test with two input futures since ExecutionList.execute
    // doesn't catch Errors and we cannot depend on the order that our
    // transformations run. (So it is possible that the Error being thrown
    // could prevent our second transformations from running).
    SettableFuture<Integer> exceptionInput = SettableFuture.create();
    ListenableFuture<Integer> exceptionComposedFuture =

      /*
       * requireNonNull is safe because propertyNames contains only non-null elements.
       *
       * Accordingly, we have it annotated as returning `Enumeration<? extends Object>` in our
       * prototype checker's JDK. However, the checker still sees the return type as plain
       * `Enumeration<?>`, probably because of one of the following two bugs (and maybe those two

    // We need to test with two input futures since ExecutionList.execute
    // doesn't catch Errors and we cannot depend on the order that our
    // transformations run. (So it is possible that the Error being thrown
    // could prevent our second transformations from running).
    SettableFuture<Integer> exceptionInput = SettableFuture.create();
    ListenableFuture<Integer> exceptionComposedFuture =

   * map are also in this queue, and that all elements not in the queue are not in the map.
   *
   * <p>The benefits of creating our own queue are that (1) we can replace elements in the middle of
   * the queue as part of copyWriteEntry, and (2) the contains method is highly optimized for the
   * current model.
   */

   * map are also in this queue, and that all elements not in the queue are not in the map.
   *
   * <p>The benefits of creating our own queue are that (1) we can replace elements in the middle of
   * the queue as part of copyWriteEntry, and (2) the contains method is highly optimized for the
   * current model.
   */

                    /* This is a key point. This is where we set the "tree" of this file which
                     * is like changing the rug out from underneath our feet.
                     */