[clang] [clang-tools-extra] [clang] support pack expansions for trailing requires clauses (PR #133190)

[via cfe-commits]

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@@ -78,6 +78,22 @@ class UnresolvedSetImpl;
 class VarTemplateDecl;
 enum class ImplicitParamKind;
 
+// Holds a constraint expression along with a pack expansion index, if
+// expanded.
+struct AssociatedConstraint {
+  const Expr *ConstraintExpr = nullptr;
+  int ArgumentPackSubstitutionIndex = -1;
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cor3ntin wrote:

I think replacing -1 by a constant in a followup patch makes sense

https://github.com/llvm/llvm-project/pull/133190