code: public static <T> Parser<T> fail(final String message) {
      return new Parser<T>() {
        @Override boolean apply(ParseContext ctxt) {
          ctxt.fail(message);
          return false;
        }
        
        @Override public String toString() {
          return message;
        }
      };
    }
docs: A {@link Parser} that always fails with {@code message}.