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

[Gábor Horváth via cfe-commits]

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@@ -833,6 +835,16 @@ class APINotesReader::Implementation {
   /// optional if the string is unknown.
   std::optional<IdentifierID> getIdentifier(llvm::StringRef Str);
 
+  /// Retrieve the identifier string for the given ID, or an empty optional if
+  /// the ID is unknown.
+  std::optional<llvm::StringRef> getIdentifierString(IdentifierID ID);
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Xazax-hun wrote:

I wonder if we should add a comment about this having linear complexity. People might not expect that. 

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