//
          // addListener has thrown an exception! SetFuture.run can't throw any exceptions so this
          // must have been caused by addListener itself. The most likely explanation is a
          // misconfigured mock. Try to switch to Failure.
          Failure failure;
          try {
            failure = new Failure(t);
          } catch (Exception | Error oomMostLikely) { // sneaky checked exception

   *
   * <p><i>Performance notes:</i> while the cartesian product of sets of size {@code m, n, p} is a
   * set of size {@code m x n x p}, its actual memory consumption is much smaller. When the
   * cartesian set is constructed, the input sets are merely copied. Only as the resulting set is
   * iterated are the individual lists created, and these are not retained after iteration.
   *

    @Override
    public String toString() {
      return "Ordering.arbitrary()";
    }

    /*
     * We need to be able to mock identityHashCode() calls for tests, because it
     * can take 1-10 seconds to find colliding objects. Mocking frameworks that
     * can do magic to mock static method calls still can't do so for a system
     * class, so we need the indirection. In production, Hotspot should still

    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    /**
     * If the specified collection is backed by an ObjectCountHashMap, it will be much more
     * efficient to iterate over it by index rather than an entry iterator, which will need to
     * allocate an object for each entry, so we check for that.
     */
    @CheckForNull

    }

    @Override
    public @NonNull T next() {
      T result = valueOrNull;
      valueOrNull = null;
      // We put the common case first, even though it's unlikely to matter if the code is run much:
      // https://shipilev.net/jvm/anatomy-quarks/28-frequency-based-code-layout/
      if (result != null) {
        return result;
      }
      throw new NoSuchElementException();
    }
  }