presto-parser/src/main/java/io/prestosql/sql/SqlFormatter.java/Formatter/formatGrantor
class Formatter:        private static String formatGrantor(GrantorSpecification grantor)
        {
            GrantorSpecification.Type type = grantor.getType();
            switch (type) {
                case CURRENT_ROLE:
                case CURRENT_USER:
                    return type.name();
                case PRINCIPAL:
                    return formatPrincipal(grantor.getPrincipal().get());
                default:
                    throw new IllegalArgumentException("Unsupported principal type: " + type);
            }
        }