It's the purity that's the challenge; you can basically construct your types just as accurate or inaccurate as you want. But purity forces you to understand a c

It's the purity that's the challenge; you can basically construct your types just as accurate or inaccurate as you want. But purity forces you to understand a couple of things first, in order to be productive (eg. monads, monad transformers, type classes). In my view, Haskell is in the opposite spectrum of Rust when it comes to performance over abstraction. Haskell abstracts everything away, and only manages to get good performance because of purity (I would argue), while Rust wants to be close to the metal, preferring performance over abstraction (e.g. with zero cost abstractions).