[clang] [Clang][NFC] Remove TemplateArgumentList::OnStack (PR #79760)

[via cfe-commits]

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@@ -301,7 +279,9 @@ class TemplateArgumentList final
   unsigned size() const { return NumArguments; }
 
   /// Retrieve a pointer to the template argument list.
-  const TemplateArgument *data() const { return Arguments; }
+  const TemplateArgument *data() const {
+    return getTrailingObjects<TemplateArgument>();
+  }
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cor3ntin wrote:

I wonder if we could get rid of that entirely in the public interface

https://github.com/llvm/llvm-project/pull/79760