Flow\Parser::parsePrimaryExpression PHP Method

    protected function parsePrimaryExpression()
    {
        $token = $this->stream->getCurrentToken();
        switch ($token->getType()) {
            case Token::CONSTANT:
            case Token::NUMBER:
            case Token::STRING:
                $node = $this->parseLiteralExpression();
                break;
            case Token::NAME:
                $this->stream->next();
                $node = new Expression\NameExpression($token->getValue(), $token->getLine());
                if ($this->stream->test(Token::OPERATOR, '(')) {
                    $node = $this->parseFunctionCallExpression($node);
                }
                break;
            case Token::CONSTANT:
            case Token::OPERATOR:
                if (($name = $this->parseName(false)) !== null) {
                    $node = new Expression\NameExpression($name->getValue(), $token->getLine());
                    break;
                }
            default:
                if ($this->stream->consume(Token::OPERATOR, '@')) {
                    $node = new Expression\FilterExpression($this->parseMacroExpression($token), array('raw'), false, $token->getLine());
                } elseif ($this->stream->consume(Token::OPERATOR, '[')) {
                    $node = $this->parseArrayExpression();
                    $this->stream->expect(Token::OPERATOR, ']');
                } elseif ($this->stream->consume(Token::OPERATOR, '(')) {
                    $node = $this->parseExpression();
                    $this->stream->expect(Token::OPERATOR, ')');
                } else {
                    throw new SyntaxError(sprintf('unexpected "%s", expecting an expression', str_replace("\n", '\\n', $token->getValue())), $token);
                }
        }
        return $this->parsePostfixExpression($node);
    }