return "", s
	}
	id = strings.TrimSpace(s[i+2 : j])
	if id == "" {
		p.corner = true // goldmark accepts {#}
		return "", s
	}
	return s[i+2 : j], s[:i]
}

func newSetextHeading(p *parseState, s line) (line, bool) {
	var n int
	peek := s
	if p.nextB() == p.para() && peek.trimSetext(&n) {
		p.closeBlock()
		para, ok := p.last().(*Paragraph)
		if !ok {
			return s, false
		}

	newPara(p, s)
}

func (c *rootBuilder) extend(p *parseState, s line) (line, bool) {
	panic("root extend")
}

var news = []func(*parseState, line) (line, bool){
	newQuote,
	newATXHeading,
	newSetextHeading,
	newHR,
	newListItem,
	newHTML,
	newFence,
	newPre,
}

func (s *line) peek() byte {
	if s.spaces > 0 {
		return ' '
	}
	if s.i >= len(s.text) {
		return 0
	}