*     the {@link ExecutionException} thrown by {@code input.get()} or, if {@code get()} throws a
   *     different kind of exception, that exception itself. To avoid hiding bugs and other
   *     unrecoverable errors, callers should prefer more specific types, avoiding {@code
   *     Throwable.class} in particular.
   * @param fallback the {@link Function} to be called if the input fails with the expected

   * full range of <a
   * href="https://docs.oracle.com/javase/9/docs/api/java/util/Formatter.html#syntax">format
   * specifiers</a>, and alert you to usage errors by throwing {@link
   * java.util.IllegalFormatException}.
   *
   * <p>In certain cases, such as outputting debugging information or constructing a message to be

   *
   * <p>This is guaranteed to return zero if the dataset contains only exactly one finite value. It
   * is not guaranteed to return zero when the dataset consists of the same value multiple times,
   * due to numerical errors. However, it is guaranteed never to return a negative result.
   *
   * <h3>Non-finite values</h3>
   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link

     * best we can do (since logging may overflow the stack) is to let the error propagate. Because
     * it is an Error, it won't be caught and logged by AbstractFuture.executeListener. Instead, it
     * can propagate through many layers of AbstractTransformFuture up to the root call to set().
     *
     * https://github.com/google/guava/issues/2254
     *
     * Other kinds of Errors are possible:
     *

   * full range of <a
   * href="https://docs.oracle.com/javase/9/docs/api/java/util/Formatter.html#syntax">format
   * specifiers</a>, and alert you to usage errors by throwing {@link
   * java.util.IllegalFormatException}.
   *
   * <p>In certain cases, such as outputting debugging information or constructing a message to be

   *
   * <pre>{@code
   * Optional<Integer> optionalInt = getSomeOptionalInt();
   * Number value = optionalInt.or(0.5); // error
   *
   * FluentIterable<? extends Number> numbers = getSomeNumbers();
   * Optional<? extends Number> first = numbers.first();
   * Number value = first.or(0.5); // error
   * }</pre>
   *

   * Function<A, B> or who call convertAll (and for any checkers that apply @PolyNull-like semantics
   * to Converter.convert). So maybe we don't want to think too hard about how to prevent our
   * checkers from issuing errors related to LegacyConverter, since it turns out that
   * LegacyConverter does violate the assumptions we make elsewhere.
   */

  @CheckForNull
  private B unsafeDoForward(@CheckForNull A a) {

  }

  /**
   * Returns an {@code InputStream} that decodes base-encoded input from the specified {@code
   * Reader}. The returned stream throws a {@link DecodingException} upon decoding-specific errors.
   */
  @J2ktIncompatible
  @GwtIncompatible // Reader,InputStream
  public abstract InputStream decodingStream(Reader reader);

  /**

   * data, and vertical if there is variance in the {@code y} data but not the {@code x} data.
   *
   * <p>This fit minimizes the root-mean-square error in {@code y} as a function of {@code x}. This
   * error is defined as the square root of the mean of the squares of the differences between the
   * actual {@code y} values of the data and the values predicted by the fit for the {@code x}

     * handleException() at all.
     */
    if (throwable instanceof Error) {
      /*
       * TODO(cpovirk): Do we really want to log this if we called setException(throwable) and it
       * returned true? This was intentional (CL 46470009), but it seems odd compared to how we
       * normally handle Error.
       *