Attempt to make MSVC happy.

llvm-svn: 104432
diff --git a/clang/lib/Driver/ArgList.cpp b/clang/lib/Driver/ArgList.cpp
index dbcc115..3d07431 100644
--- a/clang/lib/Driver/ArgList.cpp
+++ b/clang/lib/Driver/ArgList.cpp
@@ -118,7 +118,7 @@
 }
 
 int ArgList::getLastArgIntValue(OptSpecifier Id, int Default,
-                                Diagnostic &Diags) const {
+                                clang::Diagnostic &Diags) const {
   int Res = Default;
 
   if (Arg *A = getLastArg(Id)) {