}
	if !p.checkJoiners {
		return nil
	}
	trie := p.trie // p.checkJoiners is only set if trie is set.
	// TODO: merge the use of this in the trie.
	v, sz := trie.lookupString(s)
	x := info(v)
	if x.isModifier() {
		return &labelError{s, "V5"}
	}
	// Quickly return in the absence of zero-width (non) joiners.
	if strings.Index(s, zwj) == -1 && strings.Index(s, zwnj) == -1 {
		return nil
	}
	st := stateStart

	}
	if !p.checkJoiners {
		return nil
	}
	trie := p.trie // p.checkJoiners is only set if trie is set.
	// TODO: merge the use of this in the trie.
	v, sz := trie.lookupString(s)
	x := info(v)
	if x.isModifier() {
		return &labelError{s, "V5"}
	}
	// Quickly return in the absence of zero-width (non) joiners.
	if strings.Index(s, zwj) == -1 && strings.Index(s, zwnj) == -1 {
		return nil
	}
	st := stateStart