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Perl::Critic::Policy::UserlContributedoPerl:Documentati:ProhibitReusedNames(3)

NAME
       Perl::Critic::Policy::Variables::ProhibitReusedNames - Do not reuse a
       variable	name in	a lexical scope

AFFILIATION
       This Policy is part of the core Perl::Critic distribution.

DESCRIPTION
       It's really hard	on future maintenance programmers if you reuse a
       variable	name in	a lexical scope. The programmer	is at risk of
       confusing which variable	is which. And, worse, the programmer could
       accidentally remove the inner declaration, thus silently	changing the
       meaning of the inner code to use	the outer variable.

	   my $x = 1;
	   for my $i (0	.. 10) {
	       my $x = $i+1;  #	not OK,	"$x" reused
	   }

       With "use warnings" in effect, Perl will	warn you if you	reuse a
       variable	name at	the same scope level but not within nested scopes.
       Like so:

	   % perl -we 'my $x; my $x'
	   "my"	variable $x masks earlier declaration in same scope at -e line 1.

       This policy takes that warning to a stricter level.

CAVEATS
   Crossing subroutines
       This policy looks across	subroutine boundaries.	So, the	following may
       be a false positive for you:

	   sub make_accessor {
	       my ($self, $fieldname) =	@_;
	       return sub {
		   my ($self) =	@_;  # false positive, $self declared as reused
		   return $self->{$fieldname};
	       }
	   }

       This is intentional, though, because it catches bugs like this:

	   my $debug_mode = 0;
	   sub set_debug {
	       my $debug_mode =	1;  # accidental redeclaration
	   }

       I've done this myself several times -- it's a strong habit to put that
       "my" in front of	variables at the start of subroutines.

   Performance
       The current implementation walks	the tree over and over.	 For a big
       file, this can be a huge	time sink.  I'm	considering rewriting to
       search the document just	once for variable declarations and cache the
       tree walking on that single analysis.

CONFIGURATION
       This policy has a single	option,	"allow", which is a list of names to
       never count as duplicates.  It defaults to containing $self and $class.
       You add to this by adding something like	this to	your .perlcriticrc:

	   [Variables::ProhibitReusedNames]
	   allow = $self $class	@blah

AUTHOR
       Chris Dolan <cdolan@cpan.org>

       This policy is inspired by
       <http://use.perl.org/~jdavidb/journal/37548>.  Java does	not allow you
       to reuse	variable names declared	in outer scopes, which I think is a
       nice feature.

COPYRIGHT
       Copyright (c) 2008-2013 Chris Dolan

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.  The full text of this license can
       be found	in the LICENSE file included with this module.

perl v5.24.1	       Perl::Critic::Policy::Variables::ProhibitReusedNames(3)

NAME | AFFILIATION | DESCRIPTION | CAVEATS | CONFIGURATION | AUTHOR | COPYRIGHT

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