[clang] [clang] Warn on mismatched RequiresCapability attributes (PR #67520)

[Aaron Puchert via cfe-commits]

================
@@ -2073,6 +2073,18 @@ class ThreadSafetyReporter : public clang::threadSafety::ThreadSafetyHandler {
     Warnings.emplace_back(std::move(Warning), getNotes());
   }
 
+  void handleAttributeMismatch(const NamedDecl *ThisDecl,
+                               const NamedDecl *PrevDecl) override {
+    PartialDiagnosticAt Warning(ThisDecl->getLocation(),
+                                S.PDiag(diag::warn_attribute_mismatch)
+                                    << ThisDecl);
+    Warnings.emplace_back(std::move(Warning), getNotes());
+
+    PartialDiagnosticAt Note(PrevDecl->getLocation(),
+                             S.PDiag(diag::note_previous_decl) << PrevDecl);
+    Warnings.emplace_back(std::move(Note), getNotes());
----------------
aaronpuchert wrote:

The problem is likely here. You shouldn't add the note as a warning, but as a note to the corresponding warning:
```suggestion
    PartialDiagnosticAt Note(PrevDecl->getLocation(),
                             S.PDiag(diag::note_previous_decl) << PrevDecl);
    Warnings.emplace_back(std::move(Warning), getNotes(Note));
```

https://github.com/llvm/llvm-project/pull/67520