Add test case for PR 3675.

llvm-svn: 65635

clang/test/Sema/PR3675.c

@@ -0,0 +1,16 @@
+// RUN: clang -verify %s
+//
+// This example was reduced from actual code in Wine 1.1.13.  GCC accepts this
+// code, while the correct behavior is to reject it.
+//
+
+typedef struct _IRP {
+  union {
+    struct {
+      union {} u; // expected-note{{previous declaration is here}}
+      struct {
+        union {} u; // expected-error{{error: member of anonymous struct redeclares 'u'}}
+      };
+    } Overlay;
+  } Tail;
+} IRP;