Hello everybody, Although I didn't manage to reproduce the bug with a minimal example, I think it is still important enough to tell you (and especially the Hugs writers and maintainers). Yesterday evening, I tried to add some correct (!) code (by-hand-verifyable; by GHC accepted; just using plain Haskell 98) to one of the projects I'm working on. Hugs however said this: Type checking ERROR "TypeInferDecls.hs":102 - Type error in application *** Expression : checkedUnify (snd newTyEnv) inferredHpPtr explicitHpPtr (\t1 t2 ue -> ([l],ExplicitError n t1 t2 ue)) *** Term : checkedUnify *** Type : NonGenerics -> HpPtr -> HpPtr -> ErrorFunction -> TI Error () *** Does not match : a -> b -> c -> d -> e *** Because : types do not match I've read this ten times, checked my code looking whether I were doing strange things, but I can only conclude: This is, even without a minimal example, clearly a bug: the types do match. Moreover, the bug is reported about a completely different part of the file (relative to the location I edited), in code almost unrelated to the code I added (about line 300). I have explicit types everywhere in that file, so if it were wrong, the error should be reported about line 300. So the reporting-place is wrong (but I don't expect Hugs to report good error-placement). Though I didn't manage to write a minimal example, I hope our Hugs experts are able to find the bug soon. As a last point: the file is rather big: 726 lines of code, 27KB. Rijk-Jan van Haaften