@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault
class CompactHashSet<E extends @Nullable Object> extends AbstractSet<E> implements Serializable {
  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**

      Class<?> rawClass = (Class<?>) parameterizedType.getRawType();
      TypeVariable<?>[] vars = rawClass.getTypeParameters();
      Type[] typeArgs = parameterizedType.getActualTypeArguments();
      checkState(vars.length == typeArgs.length);
      for (int i = 0; i < vars.length; i++) {
        map(new TypeVariableKey(vars[i]), typeArgs[i]);
      }
      visit(rawClass);
      visit(parameterizedType.getOwnerType());

       * StackOverflowError, OutOfMemoryError (e.g., from allocating ExecutionException), or
       * something. Try to treat it like a RuntimeException. If we overflow the stack again, the
       * resulting Error will propagate upward up to the root call to set().
       */
      setException(e);
      return;
    }

    T transformResult;
    try {
      transformResult = doTransform(localFunction, sourceResult);

@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault
class CompactHashSet<E extends @Nullable Object> extends AbstractSet<E> implements Serializable {
  // TODO(user): cache all field accesses in local vars

  /** Creates an empty {@code CompactHashSet} instance. */
  public static <E extends @Nullable Object> CompactHashSet<E> create() {
    return new CompactHashSet<>();
  }

  /**