[R-pkg-devel] failing S3 dispatch

I didn't find an answer elsewhere:

My package 'bit' creates a S3 generic 'clone' and exports it. 
Furthermore it registers a S3 method 'clone.default' (not exported).

My package 'ff' imports package 'bit' and exports and registers a new S3 
method 'clone.ff'. However, calling 'clone(ffobj)' dispatches to 
clone.default instead of clone.ff !? Why?

What is the recommended way to create new S3-methods that get 
dispatched? In earlier versions of the packages I simply exported 
everything - that worked.

Best


Jens


 > require(ff)
 >
 > a <- as.ff(0:9)
 > class(x)
[1] "ff_vector" "ff"
 >
 > x <- clone(a)
 > y <- bit:::clone.default(a)
 > z <- clone.ff(a)
 >
 > # cloned ffobjects should have different filenames>

 > filename(a)? # original
[1] "/tmp/Rtmpk17JRZ/ff/clone1ed54cbb5060.ff"
 >
 > filename(x)? # unexpected equal (dispatch to clone.default)
[1] "/tmp/Rtmpk17JRZ/ff/clone1ed54cbb5060.ff"
 >
 > filename(y)? # expected equal
[1] "/tmp/Rtmpk17JRZ/ff/clone1ed54cbb5060.ff"
 >
 > filename(z)? # OK
[1] "/tmp/Rtmpk17JRZ/ff/clone1ed551d3ee66.ff"

 > version
 ?????????????? _
platform?????? x86_64-pc-linux-gnu
arch?????????? x86_64
os???????????? linux-gnu
system???????? x86_64, linux-gnu
status
major????????? 4
minor????????? 1.1
year?????????? 2021
month????????? 08
day??????????? 10
svn rev??????? 80725
language?????? R
version.string R version 4.1.1 (2021-08-10)
nickname?????? Kick Things