[clang] [APINotes] Diagnose invalid Where.Parameters selectors (PR #209408)

[John Hui via cfe-commits]

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@@ -1374,3 +1450,33 @@ void Sema::ProcessAPINotes(Decl *D) {
     }
   }
 }
+
+void APINotesSelectorDiagnosticReaderState::diagnoseUnused(Sema &S) const {
+  for (const auto &Selector : Selectors) {
+    if (Selector.Used)
+      continue;
+
+    auto SeenName = SeenNames.find(Selector.BroadKey);
+    if (SeenName == SeenNames.end())
+      continue;
+
+    S.Diag(SeenName->second.Loc, diag::warn_apinotes_message)
+        << (llvm::Twine("API notes entry for '") + SeenName->second.Name +
+            "' has unmatched Where.Parameters " +
+            api_notes::formatAPINotesParameterSelector(Selector.Parameters))
+               .str();
+  }
+}
+
+void APINotesSelectorDiagnosticState::diagnoseUnused(Sema &S) const {
----------------
j-hui wrote:

I wonder if this definition should be inlined at the declaration site, given how simple it is?

I don't feel strongly about this, though, and am fine with this here for consistency with `APINotesSelectorDiagnosticReaderState::diagnoseUnused`.

https://github.com/llvm/llvm-project/pull/209408