Merge pull request #12292 from practicalswift/swiftc-28853-result-second

[swiftc (59 vs. 5600)] Add crasher in swift::TypeBase::getContextSubstitutions

Author: practicalswift

validation-test/compiler_crashers/28853-result-second.swift

@@ -0,0 +1,16 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// REQUIRES: asserts
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+func a<a{
+extension{{}
+{
+}
+class a<a{
+class a{protocol
+protocol{protocol A typealias e:A