When deriving Data with all warnings enabled, for example compiling the following line: data TestType = TestType Int deriving (Typeable,Data) ghc 6.2 gives the following warnings: Warning: Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: GHC.Base.I# #x with #x `notElem` [1#] Is there a problem with the 'derived' code, or should this warning be ignored? regards, Keean Schupke.