Nette\Forms\Rules::adjustOperation PHP Method

    private function adjustOperation($rule)
    {
        if (is_string($rule->validator) && ord($rule->validator[0]) > 127) {
            $rule->isNegative = TRUE;
            $rule->validator = ~$rule->validator;
            if (!$rule->branch) {
                $name = strncmp($rule->validator, ':', 1) ? $rule->validator : 'Form:' . strtoupper($rule->validator);
                trigger_error("Negative validation rules such as ~{$name} are deprecated.", E_USER_DEPRECATED);
            }
            if ($rule->validator === Form::FILLED) {
                $rule->validator = Form::BLANK;
                $rule->isNegative = FALSE;
                trigger_error('Replace negative validation rule ~Form::FILLED with Form::BLANK.', E_USER_DEPRECATED);
            }
        }
        if (!is_callable($this->getCallback($rule))) {
            $validator = is_scalar($rule->validator) ? " '{$rule->validator}'" : '';
            throw new Nette\InvalidArgumentException("Unknown validator{$validator} for control '{$rule->control->name}'.");
        }
    }