default:
			ok = extend(&lx, leftRunes, leftPC)
		}
		if !ok {
			return noRune, noNext
		}
	}
	return merged, next
}

// cleanupOnePass drops working memory, and restores certain shortcut instructions.
func cleanupOnePass(prog *onePassProg, original *syntax.Prog) {
	for ix, instOriginal := range original.Inst {
		switch instOriginal.Op {
		case syntax.InstAlt, syntax.InstAltMatch, syntax.InstRune: