I think you could also make the commit message a bit more clear in terms of what's going to be using this new method and defend why it's appropriate to be placed here (i.e. it makes sense for the template type checker to have this method because users of the `TemplateTypeChecker` could use the typing information available there to determine if a diagnostic should be produced).

Try to provide the whole context in your commit message so if someone were to look at this in isolation, it would still make sense.