In the activities types Feedback, Forum, Glossary and Survey
there is an explicit check for module visibility. It is not needed if require_login() is called properly indicating the $cm.

As a result the activities are not displayed when teacher views them switching the role to student. He sees "Sorry, this activity is currently hidden".

Replication steps:

1. Log in as a teacher/admin.
2. Navigate to a course containing a Feedback, Forum, Glossary or Survey module (or create one).
3. Hide the activity.
4. Go to the activity.
5. Click Administration > Switch role to... > Student

Expected result: The activity page should be shown as would be to a student, but not hidden.

Actual result: The activity states "Sorry, this activity is currently hidden".