tools::undoc(dir = "diffobj")
# Undocumented S4 classes:
# ‘StyleFunsAnsi’ ‘GuideLines’
I'm not sure why R CMD check doesn't report this, it's meant to be part of * check for missing documentation entries:
https://github.com/r-devel/r-svn/blob/44873214cde2e96df6dcc9d466a02c6a0a5bd46a/src/library/tools/R/check.R#L2639-L2644