cognitive psychology. PhD 
Are there any programming languages with *intentionally* unsound static type systems?
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Dart - covariant subtyping of arrays is unsound, but convenient and can be caught at runtime, iirc
Great example. The point being that this is allowed, right? f : Array<Object> -> ... Array<int> a = ... f(a) // type checks Array<Object> b = a; b.push("string") // type checks & runtime error
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Hmm, the original tweet may be poorly phrased. This is the kind of example I want, but the Dart type system is still sound here when paired with runtime checks. Like soundness of gradual typing.
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Yeah, I don’t think you could be deliberately unsound at runtime because that just means you’ll get errors. I guess that there are languages which were accidentally unsound but left unsound deliberately because it’s too hard to fix
End of conversation
New conversation -
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I think the first type checks and fails at runtime. I think the second is fine
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