}
    }
  }

  /**
   * Returns a function that delegates to the {@link Interner#intern} method of the given interner.
   *
   * @since 8.0
   */
  public static <E> Function<E, E> asFunction(Interner<E> interner) {
    return new InternerFunction<>(checkNotNull(interner));
  }

  private static class InternerFunction<E> implements Function<E, E> {

    private final Interner<E> interner;

  }

  public void testAsFunction_simplistic() {
    String canonical = "a";
    String not = new String("a");

    Function<String, String> internerFunction =
        Interners.asFunction(Interners.<String>newStrongInterner());

    assertSame(canonical, internerFunction.apply(canonical));
    assertSame(canonical, internerFunction.apply(not));
  }

  public void testNullPointerExceptions() {

class Promise<T extends @Nullable Object> implements IThenable<T> {

  @JsFunction
  interface PromiseExecutorCallbackFn<T extends @Nullable Object> {
    @JsFunction
    interface ResolveCallbackFn<T extends @Nullable Object> {
      void onInvoke(T value);
    }

    @JsFunction
    interface RejectCallbackFn {
      void onInvoke(Object error);
    }

   */
  public abstract String escape(String string);

  private final Function<String, String> asFunction = this::escape;

  /** Returns a {@link Function} that invokes {@link #escape(String)} on this escaper. */
  public final Function<String, String> asFunction() {
    return asFunction;
  }

  }

  public void testAsFunction_simplistic() {
    String canonical = "a";
    String not = new String("a");

    Function<String, String> internerFunction =
        Interners.asFunction(Interners.<String>newStrongInterner());

    assertSame(canonical, internerFunction.apply(canonical));
    assertSame(canonical, internerFunction.apply(not));
  }

  public void testNullPointerExceptions() {

      }
    }
  }

  /**
   * Returns a function that delegates to the {@link Interner#intern} method of the given interner.
   *
   * @since 8.0
   */
  public static <E> Function<E, E> asFunction(Interner<E> interner) {
    return new InternerFunction<>(checkNotNull(interner));
  }

  private static class InternerFunction<E> implements Function<E, E> {

    private final Interner<E> interner;