}

// removeLeadingString removes the first n leading runes
// from the beginning of re. It returns the replacement for re.
func (p *parser) removeLeadingString(re *Regexp, n int) *Regexp {
	if re.Op == OpConcat && len(re.Sub) > 0 {
		// Removing a leading string in a concatenation
		// might simplify the concatenation.
		sub := re.Sub[0]
		sub = p.removeLeadingString(sub, n)
		re.Sub[0] = sub