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

[Gábor Horváth via cfe-commits]

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@@ -1143,6 +1251,18 @@ void Sema::ProcessAPINotes(Decl *D) {
                   return Reader->lookupGlobalFunction(FD->getName(), Parameters,
                                                       APINotesContext);
                 });
+
+          if (DiagnoseUnmatchedSelectors && !DeclarationSelectors.empty()) {
+            SmallVector<SmallVector<std::string, 4>, 4> RawAPINotesSelectors;
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Xazax-hun wrote:

Would it make sense to construct an `APINotesParameterSelectorSet` here, instead of converting this to one later? And updating the APIs to work with that type. Only if this makes things simpler. 

I feel like we have too many data types representing the same concept, it would be nice to simplify as much as possible.

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