[clang] [Clang] Follow up to previous lambda-in-concept patch (PR #210381)

[Erich Keane via cfe-commits]

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@@ -3761,13 +3761,17 @@ Decl *TemplateDeclInstantiator::VisitNonTypeTemplateParmDecl(
   if (IsExpandedParameterPack)
     Param = NonTypeTemplateParmDecl::Create(
         SemaRef.Context, Owner, D->getInnerLocStart(), D->getLocation(),
-        D->getDepth() - TemplateArgs.getNumSubstitutedLevels(),
+        D->getDepth() - (TemplateArgs.retainInnerDepths()
+                             ? 0
+                             : TemplateArgs.getNumSubstitutedLevels()),
         D->getPosition(), D->getIdentifier(), T, TSI,
         ExpandedParameterPackTypes, ExpandedParameterPackTypesAsWritten);
   else
     Param = NonTypeTemplateParmDecl::Create(
         SemaRef.Context, Owner, D->getInnerLocStart(), D->getLocation(),
-        D->getDepth() - TemplateArgs.getNumSubstitutedLevels(),
+        D->getDepth() - (TemplateArgs.retainInnerDepths()
+                             ? 0
+                             : TemplateArgs.getNumSubstitutedLevels()),
----------------
erichkeane wrote:

I agree with @cor3ntin .  This is imperfect, but I think this is a about as good as we can do without some high risk changes.

While in my lifetime I'd love to see a replacement way to do template instantation/the whole rewrite it would be to do this 'right', I think this is a 'good as it gets' for now.  So, ship it.

https://github.com/llvm/llvm-project/pull/210381