Hm. I believe the requires is provided by Moose::Role, and hence has the limitations outlined in the documentation.

What it comes down is that while I can use a role to require a method definition directly in a class, I can't "defer" the method definition until later in the class hierarchy. That is, the following would work:

package WidgetRole;
use Moose::Role;

requires 'get_widget_type';


package AbstractWidget;
use Moose;

with 'WidgetRole';

sub get_widget_type{ "IAmAbstract" }
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package WidgetRole;
use Moose::Role;

requires 'get_widget_type';


package AbstractWidget;
use Moose;

with 'WidgetRole';


package SnazzyWidget;
use Moose;

extends 'AbstractWidget';

sub get_widget_type{ "BasicWidget" }

# throws error and dies
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So I don't think roles/using requires is what I am looking for. But maybe I'm wrong - I have all of five days of experience with Moose!

Why do you have a role and and a base class? You should use a role instead of a base class. All you need is

package Widget::Role;            # Formerly Widget::Abstract
use Moose::Role;
requires qw( get_widget_type );  # Abstract methods
...                              # Other attributes and methods.
1;
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package Widget::Snazzy;
use Moose;
with qw( Widget::Role );
sub get_widget_type { __PACKAGE__ }
...
1;
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imho roles are theabstract part and the class that consumes is muchh more concrete