isUnary example

        $stream->expect(/* Token::PUNCTUATION_TYPE */ 9, ')');
        $stream->expect(/* Token::ARROW_TYPE */ 12);

        return new ArrowFunctionExpression($this->parseExpression(0), new Node($names), $line);
    }

    private function getPrimary(): AbstractExpression
    {
        $token = $this->parser->getCurrentToken();

        if ($this->isUnary($token)) {
            $operator = $this->unaryOperators[$token->getValue()];
            $this->parser->getStream()->next();
            $expr = $this->parseExpression($operator['precedence']);
            $class = $operator['class'];

            return $this->parsePostfixExpression(new $class($expr, $token->getLine()));
        } elseif ($token->test(/* Token::PUNCTUATION_TYPE */ 9, '(')) {
            $this->parser->getStream()->next();
            $expr = $this->parseExpression();
            $this->parser->getStream()->expect(/* Token::PUNCTUATION_TYPE */ 9, ')', 'An opened parenthesis is not properly closed');