Add a fail test for aligned_union of an incomplete type. See LWG#2979. NFC

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@316969 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/meta/meta.trans/meta.trans.other/aligned_union.fail.cpp

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// type_traits
+
+// aligned_union<size_t Len, class ...Types>
+
+#include <type_traits>
+
+class A; // Incomplete
+
+int main()
+{
+    typedef std::aligned_union<10, A>::type T1;
+}