checkNotNull(collection);
    return (collection instanceof EnumSet)
        ? EnumSet.complementOf((EnumSet<E>) collection)
        : makeComplementByHand(collection, type);
  }

  @J2ktIncompatible
  @GwtIncompatible
  private static <E extends Enum<E>> EnumSet<E> makeComplementByHand(
      Collection<E> collection, Class<E> type) {
    EnumSet<E> result = EnumSet.allOf(type);

  }

  private static <E extends @Nullable Object> Collection<E> typePreservingCollection(
      Collection<E> collection, @CheckForNull Object mutex) {
    if (collection instanceof SortedSet) {
      return sortedSet((SortedSet<E>) collection, mutex);
    }
    if (collection instanceof Set) {
      return set((Set<E>) collection, mutex);
    }
    if (collection instanceof List) {

  }

  private static <E extends @Nullable Object> Collection<E> typePreservingCollection(
      Collection<E> collection, @CheckForNull Object mutex) {
    if (collection instanceof SortedSet) {
      return sortedSet((SortedSet<E>) collection, mutex);
    }
    if (collection instanceof Set) {
      return set((Set<E>) collection, mutex);
    }
    if (collection instanceof List) {

  /**
   * Adds all elements in {@code iterator} to {@code collection}. The iterator will be left
   * exhausted: its {@code hasNext()} method will return {@code false}.
   *
   * @return {@code true} if {@code collection} was modified as a result of this operation
   */
  @CanIgnoreReturnValue
  public static <T extends @Nullable Object> boolean addAll(
      Collection<T> addTo, Iterator<? extends T> iterator) {
    checkNotNull(addTo);

import javax.inject.Named;
import javax.inject.Singleton;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Field;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;

      Iterable<? extends ListenableFuture<? extends T>> futures) {
    final Collection<ListenableFuture<? extends T>> collection;
    if (futures instanceof Collection) {
      collection = (Collection<ListenableFuture<? extends T>>) futures;
    } else {
      collection = ImmutableList.copyOf(futures);
    }
    return (ListenableFuture<? extends T>[]) collection.toArray(new ListenableFuture<?>[0]);
  }

/**
 * A {@link NavigableMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> as with any sorted collection, you are strongly advised not to use a {@link
 * Comparator} or {@link Comparable} type whose comparison behavior is <i>inconsistent with

      Iterable<? extends ListenableFuture<? extends T>> futures) {
    final Collection<ListenableFuture<? extends T>> collection;
    if (futures instanceof Collection) {
      collection = (Collection<ListenableFuture<? extends T>>) futures;
    } else {
      collection = ImmutableList.copyOf(futures);
    }
    return (ListenableFuture<? extends T>[]) collection.toArray(new ListenableFuture<?>[0]);
  }

                    problems);
        }
    }

    private void validateUniqueRepositoryIds(
            boolean isPluginRepository,
            Collection<Repository> pomRepositories,
            Collection<Repository> externalRepositories,
            String externalRepositoriesSource,
            ModelProblemCollector problems) {
        for (Repository externalRepository : externalRepositories) {

import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static java.util.Collections.emptySet;
import static java.util.Collections.singleton;
import static java.util.Collections.singletonList;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;