This is new in R-devel:
> rm(list = NULL)
Error in rm(list = NULL) : invalid first argument
It still works in r84020, but does not in r84023, possibly because of
r84022 [1].
Gabor
[1]
https://github.com/wch/r-source/commit/4dc057f5d49d3c0590488100e418e39b68682c95