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package fields;
=head1 NAME
fields - compile-time class fields
=head1 SYNOPSIS
{
package Foo;
use fields qw(foo bar baz);
}
...
my Foo $var = new Foo;
$var->{foo} = 42;
# This will generate a compile-time error.
$var->{zap} = 42;
=head1 DESCRIPTION
The C<fields> pragma enables compile-time verified class fields.
=cut
sub import {
my $class = shift;
my ($package) = caller;
my $fields = \%{"$package\::FIELDS"};
my $i = $fields->{__MAX__};
foreach my $f (@_) {
if (defined($fields->{$f})) {
require Carp;
Carp::croak("Field name $f already in use");
}
$fields->{$f} = ++$i;
}
$fields->{__MAX__} = $i;
}
1;
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