Merge pull request swiftlang#6805 from practicalswift/swiftc-28647-unreachable-executed-at-swift-include-swift-ast-typevisitor-h-39

Author: swift-ci

validation-test/compiler_crashers/28647-unreachable-executed-at-swift-include-swift-ast-typevisitor-h-39.swift

@@ -0,0 +1,11 @@
+// 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: deterministic-behavior
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+
+c|[{t in(0/0