presto-spi/src/main/java/io/prestosql/spi/type/RowType.java/RowType/RowType
class RowType:    private RowType(TypeSignature typeSignature, List<Field> fields)
    {
        super(typeSignature, Block.class);

        this.fields = fields;
        this.fieldTypes = fields.stream()
                .map(Field::getType)
                .collect(Collectors.toList());
    }