[Rd] Not documenting a function and not getting a check error?

[Duncan Murdoch]

I'm in the process of a fairly large overhaul of the exports from the 
rgl package, with an aim of simplifying maintenance of the package. 
During this work, I came across the reverse dependency geomorph that 
calls the rgl.primitive function.

I had forgotten that rgl.primitive was still exported:  I've been 
thinking of it as an internal function for a few years now.  I was 
surprised geomorph was able to call it.

Particularly surprising to me was the fact that it is not properly 
documented.  One of the help topics lists it as an alias, but it 
contains no usage info, and is not mentioned in the .Rd file other than 
the alias.  And yet "R CMD check rgl" has never complained about it.

Is this intentional?

Duncan Murdoch