[BUGZILLA #16963] In ?on.exit, add note that on.exit expressions are evaluated after return() call.

[MichaelChirico]

I suggest adding a note at the end of the Details section of help(on.exit) indicating:

Expressions are evaluated after the function's return value is evaluated, so on.exit cannot be used to modify the return value.

Here is an example (which you could add to the Examples section, but I don't think it is worth it):

f <- function() {
result <- list(a = 1)
on.exit(result$b <- 2)
return(result)
}
f()
# only includes $a, not $b.

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METADATA

• Bug author - Tim Hesterberg
• Creation time - 2016-06-22 17:29:19 UTC
• Bugzilla link
• Status - UNCONFIRMED
• Alias - None
• Component - Documentation
• Version - R 3.2.4
• Hardware - All All
• Importance - P5 enhancement
• Assignee - R-core
• URL -