class sysusers {
        @user{"foo":
        }
}

class backupsusers inherits sysusers {
        realize(User["foo"])
        file{"/tmp/foo":
                content => "foo",
                owner   => foo,
        }
}

include backupsusers

# puppet test.pp
err: //backupsusers/File[/tmp/foo]: Failed to retrieve current state of resource: Could not find user foo at /home/rip/test.pp:11