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Re: Idea for new warning - scalar assignment from @_

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From:
Paul Johnson
Date:
January 15, 2020 11:56
Subject:
Re: Idea for new warning - scalar assignment from @_
Message ID:
20200115115636.GA4682@pjcj.net
On Tue, Jan 14, 2020 at 10:41:16AM +0000, Dave Mitchell wrote:
> On Mon, Jan 13, 2020 at 10:16:30PM +0100, demerphq wrote:
> > On Mon, 13 Jan 2020 at 19:38, Paul "LeoNerd" Evans
> 
> [ just repeating here what I added to the github thread]
> 
> While such a warning will of course flush out possible bugs, it will also
> warn on existing perfectly valid code, such as
> 
>     my $nargs = @_;
> 
> A quick CPAN grep of \$\w+\s*=\s*\@_; matches 267 distributions, and
> looking at the first few hits, about 2/3 appear to be valid uses.

I find this argument quite convincing.

I'm not against quite specific warnings but I think I'd also be rather
surprised to find this warning only applicable to @_.  Perhaps that's
partly because I'm not sure I've ever hit Paul's original problem.

Is this a problem which would be entirely fixed with the use of
(expanded?) signatures?

> Coupled with code that may have done "use warnings FATAL => 'all'", there
> is lots of scope for breakage of existing code. So its a -1 from me.

I'm not convinced by the "use warnings FATAL => 'all'" argument though.
There are dire warnings in the docs about doing this and so I really
think that if you do it then you get what you ask for.  We can't keep
painting ourselves into backwards compatibility corners.

-- 
Paul Johnson - paul@pjcj.net

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