plt/racket — pull request #709 by shekari (2014-07-05 21:18:34+00:00)
Title: Make struct overlap work correctly.

This does 3 things.
1. Make remove intersect handle overlapping structs correctly.
2. Fix resulting breakage in restrict, by making restrict understand how
to instantiate type variables when restricting to a substruct.
3. Prevent infinite loops that occur when trying to acheive #2.