[clang] [clang] disallow narrowing when matching template template parameters (PR #124313)

[Matheus Izvekov via cfe-commits]

================
@@ -11682,6 +11683,7 @@ class Sema final : public SemaBase {
                         SmallVectorImpl<TemplateArgument> &SugaredConverted,
                         SmallVectorImpl<TemplateArgument> &CanonicalConverted,
                         CheckTemplateArgumentKind CTAK, bool PartialOrdering,
+                        bool PartialOrderingTTP,
----------------
mizvekov wrote:

In this case, they are orthogonal and all four combinations are valid. Maybe renaming s/PartialOrderingTTP/MatchingTTP would make that more clear, but there are tons of pre-existing users/

https://github.com/llvm/llvm-project/pull/124313