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Date: Wed, 17 Apr 2024 09:54:23 +0000
From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: sub prototypes aren't enough...
Message-ID: <20240417095423.M903544@dcvr>
References: <20240416205629.3648894-1-e@80x24.org>
 <20240416205629.3648894-4-e@80x24.org>
 <20240417093401.M319057@dcvr>
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In-Reply-To: <20240417093401.M319057@dcvr>
List-Id: <meta.public-inbox.org>

Eric Wong <e@80x24.org> wrote:
>   v2 fixes an incorrect call to add_uniq_timer.  Sometimes I wish Perl
>   could have more static type||arg checking, but it's probably still
>   better than other scripting languages...

Fwiw, this would work for all current callers, AFAIK:

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index a6fec954..52b89247 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -117,9 +117,9 @@ sub _add_named_timer {
 	die "Shouldn't get here.";
 }
 
-sub add_timer { _add_named_timer(undef, @_) }
+sub add_timer ($&;@) { _add_named_timer(undef, @_) }
 
-sub add_uniq_timer { # ($name, $secs, $coderef, @args) = @_;
+sub add_uniq_timer ($$&;@) { # ($name, $secs, $coderef, @args) = @_;
 	$UniqTimer{$_[0]} //= _add_named_timer(@_);
 }
 
... But the above falls short if somebody were to pass a scalar which
references CODE:

my $foo = sub {};
add_timer 5, $foo; # this valid code fails with the above patch
add_timer 5, sub {}; # this works as expected

So AFAIK Perl has no way to detect argument type bugs like this
reliably at compile time.