static <E> Collector<E, ?, ImmutableList<E>> toImmutableList() {
    return (Collector) TO_IMMUTABLE_LIST;
  }

  // Sets

  @SuppressWarnings({"rawtypes", "unchecked"})
  static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }

  static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(
      Comparator<? super E> comparator) {

   * collector without breaking j2cl?
   */
  private static final Collector<Object, ?, Optional<Object>> TO_OPTIONAL =
      Collector.of(
          ToOptionalState::new,
          ToOptionalState::add,
          ToOptionalState::combine,
          ToOptionalState::getOptional,
          Collector.Characteristics.UNORDERED);

  /**

  @SuppressWarnings({"rawtypes", "unchecked"})
  static <E> Collector<E, ?, ImmutableList<E>> toImmutableList() {
    return (Collector) TO_IMMUTABLE_LIST;
  }

  // Sets

  @SuppressWarnings({"rawtypes", "unchecked"})
  static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }

  static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(

  private final BiPredicate<? super R, ? super R> equivalence;

  private CollectorTester(
      Collector<T, A, R> collector, BiPredicate<? super R, ? super R> equivalence) {
    this.collector = checkNotNull(collector);
    this.equivalence = checkNotNull(equivalence);
  }

  /**
   * Different orderings for combining the elements of an input array, which must all produce the
   * same result.
   */

  }

  public void testToImmutableEnumMap() {
    Collector<Entry<AnEnum, Integer>, ?, ImmutableMap<AnEnum, Integer>> collector =
        Maps.toImmutableEnumMap(Entry::getKey, Entry::getValue);
    Equivalence<ImmutableMap<AnEnum, Integer>> equivalence =
        Equivalence.equals().<Entry<AnEnum, Integer>>pairwise().onResultOf(ImmutableMap::entrySet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(

		}
	}

	// Prepare to register the collectors. Other than `MetricGroup` collectors,
	// we also have standard collectors like `ProcessCollector` and `GoCollector`.

	// Create all Non-`MetricGroup` collectors here.
	collectors := map[collectorPath]prometheus.Collector{
		systemProcessCollectorPath: collectors.NewProcessCollector(collectors.ProcessCollectorOpts{
			ReportErrors: true,
		}),

    Collector<Cell<String, String, Integer>, ?, ImmutableTable<String, String, Integer>> collector =
        TableCollectors.toImmutableTable(Cell::getRowKey, Cell::getColumnKey, t -> null);
    try {
      Stream.of(immutableCell("one", "uno", 1)).collect(collector);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    collector =

        collector.setSource("SOURCE_PROBLEM2");
        collector.add(null, "PROBLEM2", -1, -1, null);

        collector.setSource("SOURCE_PROBLEM3");
        collector.add(null, "PROBLEM3", -1, -1, null);

        assertEquals("", collector.getProblems().get(0).getSource());
        assertEquals("SOURCE_PROBLEM2", collector.getProblems().get(1).getSource());

            jumpExpressions = jumpExpressions,
            hasJumps = collector.hasJumps,
            hasEscapingJumps = graphIndex.computeHasEscapingJumps(firDefaultStatement, collector),
            hasMultipleJumpKinds = collector.hasMultipleJumpKinds,
            hasMultipleJumpTargets = graphIndex.computeHasMultipleJumpTargets(collector),
            variableReassignments = collector.variableReassignments
        )
    }

    // As it's basically a DAG traversal, we can keep a queue instead of making recursive calls.
    val allFiles = this
    val filesQueueToAnalyze = ArrayDeque(allFiles)
    val collector = InlineFunctionsCollector(allFiles.first().project, reifiedInlineFunctionsOnly = false) { declaration ->
        val containingFile = declaration.containingKtFile
        if (allFiles.add(containingFile)) {