[Rd] `slot<-` performs an in-place modification

[Hervé Pagès]

Hi,

I just found out that `slot<-` performs an in-place modification of the 
object:

   setClass("A", slots=c(stuff="ANY"))
   x <- new("A", stuff=11:14)
   y <- `slot<-`(x, "stuff", value=99)

Then:

   y
   # An object of class "A"
   # Slot "stuff":
   # [1] 99

   x
   # An object of class "A"
   # Slot "stuff":
   # [1] 99

That doesn't seem right!

Is this violation of the standard pass-by-value semantic somehow 
intended here because most of the time people are expected to do 
'slot(x, "stuff") <- 99' instead, in which case the violation cannot be 
observed so does not matter? I didn't find anything in the man page 
about this.

I see this behavior with R 4.1.3 and current R devel.

Thanks,

H.

-- 
Hervé Pagès

Bioconductor Core Team
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