NAME

Perl::Critic::Policy::ValuesAndExpressions::ProhibitArrayAssignAref - don't assign an anonymous arrayref to an array

DESCRIPTION

This policy is part of the Perl::Critic::Pulp addon. It asks you not to assign an anonymous arrayref to an array

    @array = [ 1, 2, 3 ];       # bad

The idea is that it's rather unclear whether an arrayref is intended, or might have meant to be a list like

    @array = ( 1, 2, 3 );

This policy is under the "bugs" theme (see "POLICY THEMES" in Perl::Critic) for the chance [] is a mistake, and since even if it's correct it will likely make anyone reading it wonder.

An single arrayref can still be assigned to an array, but with parens to make it clear,

    @array = ( [1,2,3] );       # ok

Dereferencess or array and hash slices (see "Slices" in perldata) are recognised and treated similarly,

    @$ref = [1,2,3];            # bad assign to deref
    @{$ref} = [1,2,3];          # bad assign to deref
    @x[1,2,3] = ['a','b','c'];  # bad assign to array slice
    @x{'a','b'} = [1,2];        # bad assign to hash slice

List Assignment Parens

This policy is not a blanket requirement for () parens on array assignments, since it's normal and unambiguous to have a function call or grep etc.

    @array = foo();
    @array = grep {/\.txt$/} @array;

The only likely problem from lack of parens in such cases is that the , comma operator has lower precedence than = (see perlop), so something like

    @array = 1,2,3;   # oops, not a list

means

    @array = (1);
    2;
    3;

Normally the remaining literals in void context provoke a warning from Perl itself.

An intentional single element assignment is quite common as a statement, for instance

    @ISA = 'My::Parent::Class';   # ok

And for reference the range operator precedence is high enough,

    @array=1..10;                 # ok

though of course parens are needed if concatenating some disjoint ranges with the comma operator,

    @array = (1..5, 10..15);      # parens needed

The qw form gives a list too

    @array = qw(a b c);           # ok

SEE ALSO

Perl::Critic, Perl::Critic::Pulp

HOME PAGE

http://user42.tuxfamily.org/perl-critic-pulp/index.html

COPYRIGHT

Copyright 2011, 2012 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses>.

cpanm Perl::Critic::Pulp

perl -MCPAN -e shell
install Perl::Critic::Pulp