Sub-Attribute-Prototype

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README  view on Meta::CPAN

    that newer versions of perl would do; subject to some caveats.

 Caveats

    The following caveats should be noted about the pre-5.20 polyfilled
    version of the :prototype attribute.

      * Due to the way that attributes are applied to functions, it is not
      possible to apply the prototype immediately during compiletime.
      Instead, they must be deferred until a slightly later time. The
      earliest time that can feasibly be implemented is UNITCHECK time of
      the importing module.

      This has the unfortunate downside that function prototypes are NOT
      visible to later functions in the module itself, though they are
      visible to the importing code in the usual way. This means that
      exported functions will work just fine from the perspective of a
      module that uses them, they cannot be used internally within the
      module itself.

      Because this limitation only applies to the polyfilled version of the

README  view on Meta::CPAN

      * Perl versions older than 5.20 will provoke a warning in the
      reserved category when they encounter the attribute syntax provided
      by this polyfill, even though the polyfill has consumed the
      attribute. In order not to cause this warning to appear to users of
      modules using this syntax, it is necessary for this polyfill to
      suppress the entire reserved warning category. This means that all
      such warnings will be silenced, including those about different
      attributes.

      * Because core perl does not have a built-in way for exporter to
      inject a UNITCHECK block into their importer, it is necessary to use
      a non-core XS module, B::CompilerPhase::Hook, to provide this. As a
      result, this polyfill has non-core depenencies when running on older
      perl versions, and this dependency includes XS (i.e. compiled) code,
      and is no longer Pure Perl. It will not be possible to use tools such
      as App::FatPacker to bundle this dependency in order to ship a
      pure-perl portable script.

    It should be stressed that none of these limitations apply when running
    on a version of perl 5.20 or later. Though in that case there is no
    need to use this polyfill at all, because the :prototype attribute will

lib/Sub/Attribute/Prototype.pm  view on Meta::CPAN

The following caveats should be noted about the pre-5.20 polyfilled version
of the C<:prototype> attribute.

=over 4

=item *

Due to the way that attributes are applied to functions, it is not possible
to apply the prototype immediately during compiletime. Instead, they must be
deferred until a slightly later time. The earliest time that can feasibly be
implemented is C<UNITCHECK> time of the importing module.

This has the unfortunate downside that function prototypes are B<NOT> visible
to later functions in the module itself, though they are visible to the
importing code in the usual way. This means that exported functions will work
just fine from the perspective of a module that C<use>s them, they cannot be
used internally within the module itself.

Because this limitation only applies to the polyfilled version of the
attribute for older versions of perl, it means the behavior will differ on a
newer version of perl. Thus it is important that if you wish call a prototyped

lib/Sub/Attribute/Prototype.pm  view on Meta::CPAN

category when they encounter the attribute syntax provided by this polyfill,
even though the polyfill has consumed the attribute. In order not to cause this
warning to appear to users of modules using this syntax, it is necessary for
this polyfill to suppress the entire C<reserved> warning category. This means
that all such warnings will be silenced, including those about different
attributes.

=item *

Because core perl does not have a built-in way for exporter to inject a
C<UNITCHECK> block into their importer, it is necessary to use a non-core XS
module, L<B::CompilerPhase::Hook>, to provide this. As a result, this polyfill
has non-core depenencies when running on older perl versions, and this
dependency includes XS (i.e. compiled) code, and is no longer Pure Perl. It
will not be possible to use tools such as L<App::FatPacker> to bundle this
dependency in order to ship a pure-perl portable script.

=back

It should be stressed that none of these limitations apply when running on a
version of perl 5.20 or later. Though in that case there is no need to use

lib/Sub/Attribute/Prototype.pm  view on Meta::CPAN

            push @prototypes, [ $code, $prototype ];
            next;
         }
         push @ret, $attr;
      }

      return @ret;
   };
   { no strict 'refs'; *{"${pkg}::MODIFY_CODE_ATTRIBUTES"} = $MODIFY_CODE_ATTRIBUTES }

   B::CompilerPhase::Hook::enqueue_UNITCHECK( sub {
      foreach ( @prototypes ) {
         my ( $code, $prototype ) = @$_;
         Sub::Util::set_prototype( $_->[1], $_->[0] );
      }
   } );

   warnings->unimport( qw( reserved ) );
}

=head1 AUTHOR