Merge pull request #1091 from practicalswift/swiftc-28238-swift-typechecker-validatedecl

[swiftc] Add test case for crash triggered in swift::TypeChecker::validateDecl(…)

Author: gribozavr

validation-test/compiler_crashers/28238-swift-typechecker-validatedecl.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
+
+class B<T:B{class B<class b{}func b(T.B