SI-6928, VerifyError with self reference to super.

A bug in typers mishandled varargs. We should get more
aggressive about eliminating all the ad hoc parameter/argument
handling code spread everywhere. For varargs especially:
any code which tries to make an adjustment based on a
repeated parameter is more likely to be wrong than right.
In aggregate these reinventions are a huge source of bugs.
Merge pull request #1853 from paulp/issue/6928

SI-6928, VerifyError with self reference to super.