McGehee, Robert wrote:
The bug might be here:
is.null(expression())
[1] TRUE
But
is.null(expression(NULL))
[1] FALSE
So it might look to the methods package like you're passing in a NULL
value for @bar. I might argue that expression() should not be NULL (and
only NULL is NULL) as I have had similar trouble trying to extend
language objects to S4 classes, partially because length 0 name, call
and expression objects are either not available, or in this case,
handled poorly.
I think you've spotted it. The internal code for is.null checks for
NULL or a zero length expression, not just for NULL. Changing that so
it only accepts NULL fixes this bug.
This code has been in place since prehistoric times, so I'm going to
tread pretty carefully here before I commit a change.
Duncan Murdoch
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