[clang] [Clang] Implement C++26’s P2893R3 ‘Variadic friends’ (PR #101448)

[via cfe-commits]

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@@ -17556,11 +17584,12 @@ Decl *Sema::ActOnFriendTypeDecl(Scope *S, const DeclSpec &DS,
 
   Decl *D;
   if (!TempParams.empty())
+    // TODO: Support variadic friend template decls?
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Sirraide wrote:

I’ve opened an issue for supporting friend declarations w/ dependent NNSs: #104057

Once we actually start using `FriendTemplateDecl`s properly (which from what I can tell is what’s required for that), then this should be a natural follow-up.

https://github.com/llvm/llvm-project/pull/101448