From: Phrogz <gavin@...>
Date: 2007-02-17T15:45:11+09:00
Subject: Re: Oppinions on RCR for dup on immutable classes

On Feb 16, 4:47 pm, "Gregory Brown" <gregory.t.br...@gmail.com> wrote:
> On 2/16/07, Phrogz <g...@refinery.com> wrote:
> > I personally believe that returning self for symbols, fixnums, true,
> > false, and nil is not bad or dangerous in any way. Can you provide a
> > single example (even if contrived) where this could produce an
> > unintended result? I can only come up with one myself, and it's too
> > contrived for me to consider it a danger.
>
> the only things I can think of involve singleton methods
>
> >> def nil.foo
> >>   "hi there"
> >> end
> => nil
> >> nil.foo
> => "hi there"
> >> b = nil.dup
>
> TypeError: can't dup NilClass
>         from (irb):13:in `dup'
>         from (irb):13
>
> >> def b.bar; "confusing?"; end
>
> Imagine no error was thrown by that dup.
>
> bar would be defined both on the duped (really not duped at all) nil
> in your b variable, and on nil itself.
>
> This of course is contrived, but it would be surprising behaviour.  (I think)

A very good case. Enough so that I change my vote from "change dup" to
"leave things as they are".