> I'm always a little frustrated whenever I see this aphorism perpetuated since I think it gives the impression that a static type system is doing more than it is actually doing. In type systems that are used outside of academia, the main thing your static types are doing is checking whether the shapes of your data and functions all line up. With some small exceptions, that's it: the compiler will tell you if your LEGOs fit together, but not if you've built a knife instead of a fork.

Disagree. You can and should be using your type system to express your system design. If it's important that your utensil has at least 3 prongs, it should only be constructible by passing at least 3 prongs; that much is trivial to do even in Java, yet alone a language with a decent (i.e. ML-family) typesystem.