[clang] [clang] Language to String function (PR #69487)

[Aaron Ballman via cfe-commits]

================
@@ -10,9 +10,49 @@
 #include "clang/Config/config.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FormatVariadic.h"
----------------
AaronBallman wrote:

Let's drop this, it's kind of overkill for an unreachable message.

https://github.com/llvm/llvm-project/pull/69487