swift

5ff0bd17 - Add a few more type-checker crasher addressed by the "occurs" check.

Add a few more type-checker crasher addressed by the "occurs" check. For rdar://problem/19343997, rdar://problem/19924870, and rdar://problem/20771765. (cherry picked from commit 2ce30d32c48fa4356da72efc6359d1cc4bcee7f5)