[swyx]

4 is not an issue given that basically all other JavaScript typing systems that refused to make that tradeoff never became successful. so one could make a post hoc argument that unsoundness is simply a lesser evil than not having full JavaScript compatibility.

[Silhouette]

A decision can be rational but still, as the article says, unfortunate. Yes, it probably is the lesser evil to accept the typing wart and maintain compatibility. It's still a glaring hole in the type system of a language whose main raison d'etre is its type system.