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

[Gábor Horváth via cfe-commits]

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@@ -1001,4 +1089,53 @@ struct ObjCSelectorRef {
 } // namespace api_notes
 } // namespace clang
 
+namespace llvm {
+template <> struct DenseMapInfo<clang::api_notes::FunctionTableKey> {
+  static clang::api_notes::FunctionTableKey getEmptyKey() {
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Xazax-hun wrote:

I think in the latest version of `DenseMap` we might no longer need to define `getEmptyKey` and `getTombstoneKey`. Let's try to delete these and see if it still works as expected (make sure you are rebased on a relatively recent commit from main). 

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