[Rd] Inappropriate class(o)[!inherits(o,"AsIs")] in get_all_vars

Martin Maechler m@ech|er @end|ng |rom @t@t@m@th@ethz@ch
Mon Nov 18 14:12:07 CET 2019

>>>>> Martin Maechler 
>>>>>     on Mon, 18 Nov 2019 12:15:38 +0100 writes:

>>>>> suharto anggono--- via R-devel 
>>>>>     on Sun, 17 Nov 2019 10:34:31 +0000 writes:

    >> SVN revision 77401 changes
    >> x[isM] <- lapply(x[isM], function(o) `class<-`(o, class(o)[class(o) != "AsIs"]))
    >> to
    >> x[isM] <- lapply(x[isM], function(o) `class<-`(o, class(o)[!inherits(o,"AsIs")]))
    >> in function 'get_all_vars' in src/library/stats/R/models.R in R devel.

    >> The change is inappropriate.

    >> class(o)[class(o) != "AsIs"] removes "AsIs" from class(o), giving class(o) without "AsIs".

    >> On the other hand, inherits(o,"AsIs") is just a single logical value. If "AsIs" is in class(o), inherits(o,"AsIs") is TRUE. In that case, by recycling of logical index, class(o)[!inherits(o,"AsIs")] removes all elements of class(o), giving character(0).

    > Thank you, Suharto !

    > You are obviously right,  and I'm a bit embarrassed by my
    > overzealousness to follow my own recommendations in the  R Blog

    > http://bit.ly/R_blog_class_think_2x

    > {*wrongly*: The recommendation was to "think again" ...}

    > It's a "shame" that the wrong code did not trigger any checks,
    > so if anybody has time... I'd be grateful for such a regression
    > check.

Once I started thinking, it was easy to modify the previous
reg.check  to trigger in the case of the erronous r77401.

Fixed now in 77435.

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