[tnh]

Yeah, that trade-off makes a lot of sense. It's the logical conclusion of the "templates are textual" model. But C++ loves to have its cake and eat it regardless of the complexity, so it's non-conforming.

(I expect it's possible to construct cases where this difference is observable)

I think checking templates in isolation has value. We use statically typed languages in part to make more error classes locally-verifiable. But bolting that into a mostly-textual system is a mess.

(Checking templates in isolation is particularly valuable in IDEs, which tend to share logic with compiler frontends. IDEs only need that much power to do a passable job because the language is so complex, so I don't know which way this argument points)