Enrolment not yet started and enrolment already over notification not helpful

In a course which has an enrolment start date set and/or an enrolment end date, the error notification (incase the enrolment is currently not possible), which the students get incase the enrolment is not helpful and there is only one type of notification.

In function enrol_page_hook in moodle/enrol/self/lib.php there are already placeholders for giving different notifications:

if ($instance->enrolstartdate != 0 and $instance->enrolstartdate > time())

{ //TODO: inform that we can not enrol yet return null; }

if ($instance->enrolenddate != 0 and $instance->enrolenddate < time())

{ //TODO: inform that enrolment is not possible any more return null; }

Is there a timeframe when to expect different notifications?