@Override
          public String toString() {
            return fallback.toString();
          }
        };
    // TODO(dpb): Switch to future.catchingSync when that exists (passing a throwing function).
    return derive(future.catchingAsync(exceptionType, applyFallback, executor));
  }

  /**
   * Returns a new {@code ClosingFuture} pipeline step derived from this one by applying a function

          @Override
          public String toString() {
            return fallback.toString();
          }
        };
    // TODO(dpb): Switch to future.catchingSync when that exists (passing a throwing function).
    return derive(future.catchingAsync(exceptionType, applyFallback, executor));
  }

  /**
   * Returns a new {@code ClosingFuture} pipeline step derived from this one by applying a function