Merge pull request #1013 from practicalswift/swiftc-28217-swift-diagnosticengine-emitdiagnostic

[swiftc] Add test case for crash triggered in swift::DiagnosticEngine::emitDiagnostic(…)

Author: gribozavr

validation-test/compiler_crashers/28217-swift-diagnosticengine-emitdiagnostic.swift

@@ -0,0 +1,8 @@
+// RUN: not --crash %target-swift-frontend %s -parse
+// REQUIRES: asserts
+
+// Distributed under the terms of the MIT license
+// Test case submitted to project by https://github.com/practicalswift (practicalswift)
+// Test case found by fuzzing
+
+var b{enum b:String{case=nil