You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parser.go
    path of file: ./repos/DocHub/vendor/github.com/andybalholm/cascadia
    
    the code of the file until where you have to start completion: // Package cascadia is an implementation of CSS selectors.
package cascadia

import (
	"errors"
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"golang.org/x/net/html"
)

// a parser for CSS selectors
type parser struct {
	s string // the source text
	i int  
    
func (p *parser) parseIdentifier() (result string, err error) {
	startingDash := false
	if len(p.s) > p.i && p.s[p.i] == '-' {
		startingDash = true
		p.i++
	}

	if len(p.s) <= p.i {
		return "", errors.New("expected identifier, found EOF instead")
	}

	if c := p.s[p.i]; !(nameStart(c) || c == '\\') {
		return "", fmt.Errorf("expected identifier, found %c instead", c)
	}

	result, err = p.parseName()
	if startingDash && err == nil {
		result = "-" + result
	}
	return
}