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Yeah I realise you'd never reach the same level of soundness due to the limitations of the underlying JS (although presumably you could get close with a subset?). But that's why it's an interesting challenge, and I think what Flow has shown is that it's possible to get a lot closer than had previously been imagined.

If everyone just accepted the argument 4 years ago that "JS will never be sound" then maybe today TS would still just be Java style `interface` annotations for classes. It's not like the Flow team has reached a ceiling at this point... there's still plenty on their roadmap that would continue to improve soundness and expressiveness.

> You can’t have anything approaching ocaml correctness when in typescript all objects with the same shape are interchangeable.

Could you elaborate? Flow has recently switched to exact objects by default[1], which I would have thought would be enough for a sound approach?

[1] https://medium.com/flow-type/on-the-roadmap-exact-objects-by...

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type A = {name: string} type B = {name: string} function print(obj: A) { alert(obj.name);} let a: A = {name: “hello”}; let b: B = {name: “world”} print(a); print(b);