Why isn't `size` always inferred to be an Integer?

Type instabilities in end-packages tend to impact runtime speed, not the (pre-)compile time. In upstream libraries, yes, they can indeed become one of the magnets for invalidation, but I don’t think they’re typically troublesome at the point where I think you are.

This conversation is now circling back to the original thread from which it was split — we can go back to Taking TTFX seriously: Can we make common packages faster to load and use for concrete tips for reducing that compile time.