[clang] [Clang][P1061] Add stuctured binding packs (PR #121417)

[Richard Smith via cfe-commits]

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@@ -5321,6 +5321,59 @@ class BuiltinBitCastExpr final
   }
 };
 
+// Represents an unexpanded pack where the list of expressions are
+// known. These are used when structured bindings introduce a pack.
+class ResolvedUnexpandedPackExpr final
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zygoloid wrote:

This seems to be doing the same job as `SubstNonTypeTemplateParmPackExpr` and `FunctionParmPackExpr`. Do we need all three? If so, mentioning the relationship between the three in this comment might be nice -- but I do wonder if `FunctionParmPackExpr` could be generalized to cover the case of a binding declaration too.

https://github.com/llvm/llvm-project/pull/121417