Comment by eru

Well, Haskell is a big language with lots of different aspects.

To nicely support TVars, it's good if your language can differentiate between pure code and code with side-effects. Haskell's type system is one way to get there; but eg something like Rust could probably also be coerced to do something appropriate.

Apart from that, you probably don't even need static typing to make it work well enough (though it probably helps). You definitely don't need laziness or Haskell's love of making up new operators or significant whitespace.