The features Haskell has been “trying to copy” from TypeScript are, without exception, features TypeScript copied from type theory research that predates TypeScript by decades – row polymorphism from Didier Rémy’s 1989 work, untagged unions from the intersection type literature of the 1980s, type-level computation from Martin-Löf’s 1975 intuitionistic type theory – and what you are observing is not Haskell enviously watching TypeScript and taking notes, but rather two languages drinking from the same well of ideas, one of which is doing so with a formal semantics and a proof of soundness, and the other of which is doing so while standing in a JavaScript runtime and hoping no one looks down.​​​​​​​​​​​​​​​​

Purescript > Typescript