[clang] [clang] Exclude non-template classes when checking if constraint refers to containing template arguments (PR #74265)

[Erich Keane via cfe-commits]

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@@ -1714,6 +1714,8 @@ class ConstraintRefersToContainingTemplateChecker
   // Friend, likely because it was referred to without its template arguments.
   void CheckIfContainingRecord(const CXXRecordDecl *CheckingRD) {
     CheckingRD = CheckingRD->getMostRecentDecl();
+    if (!CheckingRD->isTemplated())
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erichkeane wrote:

Hmm... I THINK that should be rejected, since you can't name `Child` without naming `Parent`?  But I don't think the standard is explicit about that.

So perhaps `isTemplated` is what we want here.

I didn't think it too far through when making the comment, but I'm glad you put together a good example.



https://github.com/llvm/llvm-project/pull/74265