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

[Jason Rice 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
+    : public Expr,
+      private llvm::TrailingObjects<ResolvedUnexpandedPackExpr, Expr *> {
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ricejasonf wrote:

Personally, I am content to leave it as is, but storing Decls instead of Exprs does have the benefit of delaying building the DeclRefExprs until expansion which creates less garbage and would simplify `flat_bindings`. If anything, I would leave the name `ResolvedUnexpandedPackExpr` and make the trailing objects `ValueDecl`  to support future consolidation. That is premised on never wanting to create a pack of expressions which was my original intent as this was made for P1221 (which I have abandoned). I will defer to @cor3ntin.

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