Merge pull request #4808 from practicalswift/swiftc-28420-swift-lowering-emitconditionalcheckedcast

Author: swift-ci

validation-test/compiler_crashers/28420-swift-lowering-emitconditionalcheckedcast.swift

@@ -0,0 +1,17 @@
+// 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 -emit-ir
+// REQUIRES: asserts
+struct A{
+func a()->String{
+}
+}
+func b(){
+guard let c = A.a as?String else{
+}
+}