Added -Wdisabled-macro-expansion warning.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147418 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index dea7efc..90b6798 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -509,8 +509,10 @@
 
   // If this is a macro to be expanded, do it.
   if (MacroInfo *MI = getMacroInfo(&II)) {
-    if (!DisableMacroExpansion && !Identifier.isExpandDisabled()) {
-      if (MI->isEnabled()) {
+    if (!DisableMacroExpansion) {
+      if (Identifier.isExpandDisabled()) {
+        Diag(Identifier, diag::pp_disabled_macro_expansion);
+      } else if (MI->isEnabled()) {
         if (!HandleMacroExpandedIdentifier(Identifier, MI))
           return;
       } else {
@@ -518,6 +520,7 @@
         // expanded, even if it's in a context where it could be expanded in the
         // future.
         Identifier.setFlag(Token::DisableExpand);
+        Diag(Identifier, diag::pp_disabled_macro_expansion);
       }
     }
   }