C++11 allows unions to have static data members. Remove the corresponding
restriction and add some tests.

llvm-svn: 150721
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9fa0349..64a67d9 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3920,20 +3920,24 @@
       } else if (SC == SC_None)
         SC = SC_Static;
     }
-    if (SC == SC_Static) {
+    if (SC == SC_Static && CurContext->isRecord()) {
       if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC)) {
         if (RD->isLocalClass())
           Diag(D.getIdentifierLoc(),
                diag::err_static_data_member_not_allowed_in_local_class)
             << Name << RD->getDeclName();
 
-        // C++ [class.union]p1: If a union contains a static data member,
-        // the program is ill-formed.
-        //
-        // We also disallow static data members in anonymous structs.
-        if (CurContext->isRecord() && (RD->isUnion() || !RD->getDeclName()))
+        // C++98 [class.union]p1: If a union contains a static data member,
+        // the program is ill-formed. C++11 drops this restriction.
+        if (RD->isUnion())
           Diag(D.getIdentifierLoc(),
-               diag::err_static_data_member_not_allowed_in_union_or_anon_struct)
+               getLangOptions().CPlusPlus0x
+                 ? diag::warn_cxx98_compat_static_data_member_in_union
+                 : diag::ext_static_data_member_in_union) << Name;
+        // We conservatively disallow static data members in anonymous structs.
+        else if (!RD->getDeclName())
+          Diag(D.getIdentifierLoc(),
+               diag::err_static_data_member_not_allowed_in_anon_struct)
             << Name << RD->isUnion();
       }
     }