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Re: [perl #5087] used only once warning

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From:
Nicholas Clark
Date:
May 18, 2013 08:35
Subject:
Re: [perl #5087] used only once warning
Message ID:
20130518083454.GD3729@plum.flirble.org
On Fri, May 17, 2013 at 05:31:39PM -0700, James E Keenan via RT wrote:
> On Sat Jan 05 11:20:05 2013, rjbs wrote:
> > On Fri Dec 14 07:36:17 2012, nicholas wrote:
> > > On Wed, Dec 12, 2012 at 01:15:39PM -0500, Peter Martini wrote:
> > >
> > > > Right.  Can the ticket be closed for that reason then?  There is
> > an
> > > > implementation of a module to do this on cpan, and a note on this
> > warning
> > > > in the docs wouldn't hurt.
> > >
> > > I think fix the documentation to be clear on the "what" and the
> > "why", then
> > > close the ticket.
> > 
> > When I wrote about this todo a while ago, I suggested that assigning
> > to a lexical was enough
> > to indicate that it was used.  For example, "my $exit = Scope::Guard-
> > >..." is useful, even if
> > you don't mention $exit again.  Similarly, "my ($self, @x) = @_" is
> > not madness.
> > 
> > This does mean that we're detecting fewer actually bogus cases.  We'd
> > only get variables
> > declared and use never, rather than used once.  (my $x;)
> > 
> > Is that sufficiently useful to pursue?  I'm not sure.
> 
> This is the sort of ticket where, the more people think out loud about
> it, the farther we get from closing it.
> 
> My reading of the ticket leads me to believe:
> 
> * No one is convinced we need any changes in Perl's behavior here.
> 
> * No one is convinced of the necessity of a documentation patch -- as no
> one has submitted one since the idea was first floated.

I don't agree with this reasoning. Specifically treating "necessity" as
implying "lack of desirability" and hence "reason to close".

By that reasoning, we would close all wishlist tickets that no-one works on.

> It's time to try, once again, to put this ticket out of its 13-year-old
> misery.  I am taking this ticket for the purpose of closing it and will
> do so in 7 days unless someone submits a documentation patch.

I don't agree with this.

The documentation doesn't say clearly that it doesn't apply to lexicals.

A documentation patch is desirable. But anyone could write it. But not
everyone can hack the C code or the build system, so I prioritise my time
on that.

I would welcome a documentation patch that said that the warning doesn't
apply to lexicals. (Or someone to tell me where the fine manual already says
this)

Nicholas Clark

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