public function enterNode(Node $node)
    {
        if ($this->atLeastPhp55) {
            return;
        }

        if (!$node instanceof Empty_) {
            return;
        }

        if (!$node->expr instanceof Variable) {
            $msg = \sprintf('syntax error, unexpected %s', $this->getUnexpectedThing($node->expr));

            throw new ParseErrorException($msg, $node->expr->getLine());
        }
    }