presto-rcfile/src/main/java/io/prestosql/rcfile/text/TextRcFileEncoding.java/TextRcFileEncoding/structEncoding
class TextRcFileEncoding:    @Override
    public ColumnEncoding structEncoding(Type type, List<ColumnEncoding> fieldEncodings)
    {
        return new StructEncoding(
                type,
                nullSequence,
                separators,
                escapeByte,
                lastColumnTakesRest,
                fieldEncodings.stream()
                        .map(TextColumnEncoding.class::cast)
                        .collect(Collectors.toList()));
    }