func tError(c context, s []byte) (context, int) {
	return c, len(s)
}

// eatAttrName returns the largest j such that s[i:j] is an attribute name.
// It returns an error if s[i:] does not look like it begins with an
// attribute name, such as encountering a quote mark without a preceding
// equals sign.
func eatAttrName(s []byte, i int) (int, *Error) {
	for j := i; j < len(s); j++ {
		switch s[j] {