[clang] [clang-tools-extra] [Clang] Add a builtin that deduplicate types into a pack (PR #106730)

[Ilya Biryukov via cfe-commits]

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@@ -17992,7 +17992,12 @@ DeclResult Sema::ActOnTemplatedFriendTag(
   collectUnexpandedParameterPacks(QualifierLoc, Unexpanded);
   unsigned FriendDeclDepth = TempParamLists.front()->getDepth();
   for (UnexpandedParameterPack &U : Unexpanded) {
-    if (getDepthAndIndex(U).first >= FriendDeclDepth) {
+    unsigned Depth;
+    if (auto DI = getDepthAndIndex(U))
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ilya-biryukov wrote:

Done. It is actually `optional<pair>`. I have made the type explicit instead of `auto` too

https://github.com/llvm/llvm-project/pull/106730