return sets.NewString(""), nil
	default:
		return nil, fmt.Errorf("found '%s', expected: ',', ')' or identifier", lit)
	}
}

// parseIdentifiersList parses a (possibly empty) list of
// of comma separated (possibly empty) identifiers
func (p *Parser) parseIdentifiersList() (sets.String, error) {
	s := sets.NewString()
	for {
		tok, lit := p.consume(Values)
		switch tok {
		case IdentifierToken:
			s.Insert(lit)