[Rd] AddComment (gram.y)

[Peter Danenberg]

> IIRC, because there were always cases where they were attached to
> the wrong expression, and we were more or less convinced, there was
> no to do it "right" in all cases.

Doxygen and Javadoc seem to have solved the problem of comment-object
association, implying that it's not generally intractable; are there
any ambiguities specific to R (but not, say, C++ or Java) that make it
a special case?