Hello! I think NHC does not properly handle exports and imports of field labels. Problem 1 -------- The following two modules seem to be legal according to the Haskell 98 report (Sec.5.2, p. 66): ================================================================== module See1 ( D( Undef, Def, value ) ) where data D = Undef | Def{ value :: Int } ------------------------------------------------------------------ module See2 ( foo ) where import See1 ( D( Undef, Def, value ) ) foo :: D -> Int foo d = case d of Undef -> error "no value" Def{} -> value d ================================================================== Both GHC and Hugs accept this, but NHC reports an error: hmake -d../nhc See2.hs nhc98 -c -d ../nhc See1.hs ==================================== In file: ./See1.hs: 1:16 Found ( but expected one of ) , If one changes the heading of See1 to module See1 ( D( Undef, Def ), value ) where then one gets hmake -d../nhc See2.hs nhc98 -c -d ../nhc See2.hs ==================================== In file: ./See2.hs: 3:13 Found ( but expected a {-end-of-definition-or-EOF-} Problem 2 --------- There are no syntactic problems when one uses another, equally legal form: ================================================================== module See1 ( D( Undef, Def ), value ) where data D = Undef | Def{ value :: Int } ------------------------------------------------------------------ module See2 ( foo ) where import See1 ( D( Undef, Def ), value ) foo :: D -> Int foo d = case d of Undef -> error "no value" Def{} -> value d ================================================================== Again, this is accepted both by GHC and Hugs. But now NHC has another bone to pick: hmake -d../nhc See2.hs nhc98 -c -d ../nhc See2.hs ==================================== Error when renaming:: Identifier value defined 2 times. To make this go away, one has to change the importation clause to import See1 ( D( Undef, Def ) ) Now everything is OK, and NHC does not complain about the occurrence of "value" in "foo"! Regards, -- Feliks