Switched FormatAttr to using an IdentifierArgument instead of a StringArgument since that is a more accurate modeling.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189851 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 499c21c..82eca73 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -2141,7 +2141,7 @@
 }
 
 Sema::FormatStringType Sema::GetFormatStringType(const FormatAttr *Format) {
-  return llvm::StringSwitch<FormatStringType>(Format->getType())
+  return llvm::StringSwitch<FormatStringType>(Format->getType()->getName())
   .Case("scanf", FST_Scanf)
   .Cases("printf", "printf0", FST_Printf)
   .Cases("NSString", "CFString", FST_NSString)