[clang] [clang-tools-extra] [clang] Extend diagnose_if to accept more detailed warning information (PR #70976)

[Aaron Ballman via cfe-commits]

================
@@ -597,6 +592,15 @@ DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
   return Result;
 }
 
+DiagnosticIDs::Class DiagnosticIDs::getDiagClass(unsigned DiagID) const {
+  if (IsCustomDiag(DiagID))
+    return Class(CustomDiagInfo->getDescription(DiagID).GetClass());
+
+  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
+    return Class(Info->Class);
+  return Class(~0U);
----------------
AaronBallman wrote:

This is UB because it's outside the range of representable values for the `Class` enum; maybe make it an enum member instead?

https://github.com/llvm/llvm-project/pull/70976