Merge pull request #3345 from practicalswift/swiftc-28345-swift-iterativetypechecker-processtypechecksuperclass

[swiftc] Add 💥 case (😢 → 56, 😀 → 5099) triggered in swift::IterativeTypeChecker::processTypeCheckSuperclass(…)

Author: practicalswift

validation-test/compiler_crashers/28345-swift-iterativetypechecker-processtypechecksuperclass.swift

@@ -0,0 +1,10 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// RUN: not --crash %target-swift-frontend %s -parse
+// REQUIRES: asserts
+struct A<A{class a{protocol A{struct B{}class B<T where B:T>:a