[cwzwarich]

I think it's fair to say that (GHC) Haskell no longer really uses the Hindley-Milner type system. It doesn't have let generalization (except in a few restricted cases), and it doesn't have principal types, which I would consider to be the two distinguishing features of HM.

[danharaj]

Let generalization should only be disabled if one uses the GADT type extension and even then can be turned on in addition to GADTs. While Haskell isn't really Hindley-Milner, it's close enough for most development.