Try the November release of Hugs with the +N option.

Well, now Hugs and ghc show the same behaviour for my program: they don't parse my doc, even with the same error. But the +N does not work: it says "New hierarchical libraries not found along search path; ignoring +N toggle." I tried adding {Hugs}\libraries to the Options, but after a restart, it is missing again. How can I change that?