switch p.tok {
		case _Import:
			p.next()
			f.DeclList = p.appendGroup(f.DeclList, p.importDecl)

		case _Const:
			p.next()
			f.DeclList = p.appendGroup(f.DeclList, p.constDecl)

		case _Type:
			p.next()
			f.DeclList = p.appendGroup(f.DeclList, p.typeDecl)

		case _Var:
			p.next()
			f.DeclList = p.appendGroup(f.DeclList, p.varDecl)

		case _Func:
			p.next()

		return
	}
	i += 2
	name, s := s[0:i+2], s[i+2:]
	g := posixGroup[name]
	if g.sign == 0 {
		return nil, "", &Error{ErrInvalidCharRange, name}
	}
	return p.appendGroup(r, g), s, nil
}

func (p *parser) appendGroup(r []rune, g charGroup) []rune {
	if p.flags&FoldCase == 0 {
		if g.sign < 0 {
			r = appendNegatedClass(r, g.class)
		} else {
			r = appendClass(r, g.class)
		}