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.
   */

   * 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);

  /**

        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());

   * 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);

  /**

import java.util.function.Supplier;
import java.util.stream.Collector;
import org.checkerframework.checker.nullness.qual.Nullable;

/** Collectors utilities for {@code common.collect.Table} internals. */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class TableCollectors {

  static <T extends @Nullable Object, R, C, V>
      Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(

    return Collector.of(
        (Supplier<ImmutableTable.Builder<R, C, V>>) ImmutableTable.Builder::new,
        (builder, t) ->
            builder.put(rowFunction.apply(t), columnFunction.apply(t), valueFunction.apply(t)),
        ImmutableTable.Builder::combine,
        ImmutableTable.Builder::build);
  }

  static <T extends @Nullable Object, R, C, V>
      Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(

        val collector = InlineFunctionsCollector(project, analyzeOnlyReifiedInlineFunctions) { declaration ->
            if (!analyzedElements.contains(declaration)) {
                nextInlineFunctions.add(declaration)
            }
        }
        val propertyAccessor = InlineDelegatedPropertyAccessorsAnalyzer(analysisContext, collector)

        element.accept(object : KtTreeVisitorVoid() {

    // 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)) {

     */
    @Override
    public TransformerContext initialize(ModelBuildingRequest request, ModelProblemCollector collector) {
        // We must assume the TransformerContext was created using this.newTransformerContextBuilder()
        DefaultModelProblemCollector problems = (DefaultModelProblemCollector) collector;
        return new TransformerContext() {

            @Override
            public Path locate(Path path) {

     */
    @Override
    public ModelTransformerContext initialize(ModelBuilderRequest request, ModelProblemCollector collector) {
        // We must assume the TransformerContext was created using this.newTransformerContextBuilder()
        DefaultModelProblemCollector problems = (DefaultModelProblemCollector) collector;
        return new ModelTransformerContext() {

            @Override
            public Path locate(Path path) {