[clang] [clang-tools-extra] [clang][diagnostics] Stable IDs for Clang diagnostics (PR #168153)

[Dave Bartolomeo via cfe-commits]

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@@ -434,6 +478,30 @@ StringRef DiagnosticIDs::getDescription(unsigned DiagID) const {
   return CustomDiagInfo->getDescription(DiagID).GetDescription();
 }
 
+/// getStableID - Given a diagnostic ID, return the stable ID of the diagnostic.
+std::string DiagnosticIDs::getStableID(unsigned DiagID) const {
+  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
+    return Info->getStableID().str();
+  assert(CustomDiagInfo && "Invalid CustomDiagInfo");
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dbartol wrote:

I had a colleague double-check my logic here, and he concurred with my reasoning. I'm going to merge based on your conditional approval, but do ping me if there's something you want me to follow up on.

https://github.com/llvm/llvm-project/pull/168153