[clang] [clang-tools-extra] [Clang][C++29] Template pack indexing (PR #218738)

[Corentin Jabot via cfe-commits]

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@@ -4973,6 +4987,101 @@ TemplateName TreeTransform<Derived>::TransformTemplateName(
         S->getFinal());
   }
 
+  if (PackIndexingTemplateStorage *PI = Name.getAsPackIndexingTemplate()) {
+    assert(!QualifierLoc && "Unexpected qualified pack-index-template-name");
+
+    ExprResult IndexExpr;
+    {
+      EnterExpressionEvaluationContext ConstantContext(
+          SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+      IndexExpr = getDerived().TransformExpr(PI->getIndexExpr());
+      if (IndexExpr.isInvalid())
+        return TemplateName();
+    }
+
+    auto TransformOne = [&](TemplateName N) {
+      NestedNameSpecifierLoc NoQualifier;
+      return getDerived().TransformTemplateName(
+          NoQualifier, TemplateKWLoc, N, NameLoc, ObjectType,
+          FirstQualifierInScope, AllowInjectedClassName);
+    };
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cor3ntin wrote:

how so? It's use 5 times

https://github.com/llvm/llvm-project/pull/218738