Bug#691102: perl: Any ~~ Object smartmatch precedence broken

[Niko Tyni]

Package: perl
Version: 5.14.2-14
Severity: important
Tags: patch fixed-upstream

Perl 5.14.3 included the attached patch, which fixes incorrect smartmatch
precedence.

$ perl -lwe '{ package A; use overload "~~" => sub { print "in overloaded match A"; }; } { package B; use overload "~~" => sub { print "in overloaded match B"; }; } my $a=bless({},"A"); my $b=bless({},"B"); print $a ~~ $b'   
in overloaded match A
1

According to the documented behaviour, the first line should be 
in overloaded match B

There's some background at
 http://www.nntp.perl.org/group/perl.perl5.porters/2011/07/msg174260.html
where the upstream consensus is clearly that this is a misfeature that
nobody should be counting on and works against the current documentation.

The patch removes two incorrect test cases; quoting Leon Timmermans in
the thread:

>> It fixes the issue but
>> makes two tests in t/op/smartmatch.t fail. It creates a failure if you
>> match an object with smartmatch overloading with an object that has
>> overloading but not for smartmatching (in case of the test,
>> stringification overloading). I'm not sure that case is sane to begin
>> with though.
>
> IMO, in this case following the left hand (the current behavior) is
> simply insane, for reasons Ricardo already explained. Following the
> right hand if it doesn't overload smartmatching is simply impossible:
> it can't know if it should use the code, hash, regexp, array, string
> or number overloading. Making this obscure use-case die is the only
> possible sane thing we can do. 

The issue isn't a regression from squeeze, but we think it should be
fixed rather sooner than later, on the principle of least surprise.
-- 
Niko Tyni   ntyni at debian.org
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