@Override
          protected char[] escapeUnsafe(char c) {
            return ("{" + c + "}").toCharArray();
          }
        };
    EscaperAsserts.assertBasic(wrappingEscaper);
    // '[' and '@' lie either side of [A-Z].
    assertEquals("{[}FOO{@}BAR{]}", wrappingEscaper.escape("[FOO@BAR]"));
  }

  public void testSafeRange_maxLessThanMin() throws IOException {
    // Basic escaping of unsafe chars (wrap them in {,}'s)

       * instance.
       */
      super("");
    }

    @Override
    Comparable<?> endpoint() {
      throw new IllegalStateException("range unbounded on this side");
    }

    @Override
    boolean isLessThan(Comparable<?> value) {
      return true;
    }

    @Override
    BoundType typeAsLowerBound() {
      throw new IllegalStateException();
    }

   * class documentation above). This method is <i>generally expected</i>, but not absolutely
   * required, to have the following properties:
   *
   * <ul>
   *   <li>Its execution does not cause any observable side effects.
   *   <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal
   *       Objects.equal}{@code (a, b)} implies that {@code predicate.apply(a) ==
   *       predicate.apply(b))}.
   * </ul>

          @Override
          protected char[] escapeUnsafe(char c) {
            return ("{" + c + "}").toCharArray();
          }
        };
    EscaperAsserts.assertBasic(wrappingEscaper);
    // '[' and '@' lie either side of [A-Z].
    assertEquals("{[}FOO{@}BAR{]}", wrappingEscaper.escape("[FOO@BAR]"));
  }

  public void testSafeRange_maxLessThanMin() throws IOException {
    // Basic escaping of unsafe chars (wrap them in {,}'s)

   * class documentation above). This method is <i>generally expected</i>, but not absolutely
   * required, to have the following properties:
   *
   * <ul>
   *   <li>Its execution does not cause any observable side effects.
   *   <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal
   *       Objects.equal}{@code (a, b)} implies that {@code predicate.apply(a) ==
   *       predicate.apply(b))}.
   * </ul>

   *     then this is not logically a {@code Converter} at all, and should just implement {@link
   *     Function}.
   */
  @ForOverride
  protected abstract A doBackward(B b);

  // API (consumer-side) methods

  /**
   * Returns a representation of {@code a} as an instance of type {@code B}.
   *
   * @return the converted value; is null <i>if and only if</i> {@code a} is null
   */
  @CheckForNull

          protected char[] escapeUnsafe(int c) {
            return ("{" + (char) c + "}").toCharArray();
          }
        };
    EscaperAsserts.assertBasic(wrappingEscaper);
    // '[' and '@' lie either side of [A-Z].
    assertEquals("{[}FOO{@}BAR{]}", wrappingEscaper.escape("[FOO@BAR]"));
  }

  public void testDeleteUnsafeChars() throws IOException {
    UnicodeEscaper deletingEscaper =

       * need to clear our reference to the TimeoutFuture is the reason we use a *static* nested
       * class with a manual reference back to the "containing" class.)
       *
       * This has the nice-ish side effect of limiting reentrancy: run() calls
       * timeoutFuture.setException() calls run(). That reentrancy would already be harmless, since
       * timeoutFuture can be set (and delegate cancelled) only once. (And "set only once" is

 * for any {@link Object}. Also offers basic text processing methods based on this function.
 * Implementations are strongly encouraged to be side-effect-free and immutable.
 *
 * <p>Throughout the documentation of this class, the phrase "matching character" is used to mean
 * "any {@code char} value {@code c} for which {@code this.matches(c)} returns {@code true}".
 *

      label: 3. What would that same code look like if we added your feature?
    validations:
      required: true

  - type: markdown
    attributes:
      value: >
        Comparing two approaches to a use case side by side can make it easier to examine the
        differences between them.


        Additionally, it's very useful to us if you can provide a "straw API" — what the