src/Language/Parser.php
private function parseArgument()
    {
        $start = $this->lexer->token;
        $name  = $this->parseName();

        $this->expect(Token::COLON);
        $value = $this->parseValueLiteral(false);

        return new ArgumentNode([
            'name'  => $name,
            'value' => $value,
            'loc'   => $this->loc($start),
        ]);
    }
private function parseArgument()
    {
        $start = $this->lexer->token;
        $name  = $this->parseName();

        $this->expect(Token::COLON);
        $value = $this->parseValueLiteral(false);

        return new ArgumentNode([
            'name'  => $name,
            'value' => $value,
            'loc'   => $this->loc($start),
        ]);
    }
@return ArgumentNode

@throws SyntaxError