Update ASTContext.cpp

Author: gmh5225

clang/lib/AST/ASTContext.cpp

@@ -7118,12 +7118,15 @@ QualType ASTContext::isPromotableBitField(Expr *E) const {
   //        We perform that promotion here to match GCC and C++.
   // FIXME: C does not permit promotion of an enum bit-field whose rank is
   //        greater than that of 'int'. We perform that promotion to match GCC.
-  if (BitWidth < IntSize)
+  if (BitWidth < IntSize) {
+    if (getLangOpts().MicrosoftExt || getLangOpts().MSVCCompat)
+      return {};
 #ifdef _WIN32
     return {};
 #else
     return IntTy;
 #endif
+  }
 
   if (BitWidth == IntSize)
     return FT->isSignedIntegerType() ? IntTy : UnsignedIntTy;