[R-sig-Debian] c2d4u3.5 packages not working in R 3.5 anymore

[Jeroen Ooms]

Travis users are reporting a lot of these errors when testing packages on R 3.5:

  Error: package or namespace load failed for ‘....’ in rbind(info,
getNamespaceInfo(env, "S3methods")):

This problem seems to happen when a c2d4u package was compiled with R
3.6 and is loaded in R 3.5. The problem does not appear when using the
same r-cran-xyz package on R 3.6. I'm not entirely sure what the root
cause is but I think it has to do with a new feature in R 3.6 (from
the NEWS file):

  S3method() directives in ‘NAMESPACE’ can now also be used to perform
delayed S3 method registration.

Maybe c2d4u3.5 packages should be compiled with R 3.5 instead of R
3.6? I think backward compatibility not a problem.