[clang] [Clang][C++26] Implement Pack Indexing (P2662R3). (PR #72644)

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@@ -836,6 +836,8 @@ ANNOTATION(primary_expr) // annotation for a primary expression, used when
                          // message send
 ANNOTATION(decltype)     // annotation for a decltype expression,
                          // e.g., "decltype(foo.bar())"
+ANNOTATION(indexed_pack_type) // annotation for an indexed pack of type,
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cor3ntin wrote:

I did remain a lot of types to be more consistent, let me know what you think

https://github.com/llvm/llvm-project/pull/72644