Hi Joel,
import Data.Generics import qualified Text.ParserCombinators.Parsec as P
instance Data SourcePos where gfoldl r k x = k x
typename_SourcePos = mkTyCon "SourcePos"
instance Typeable SourcePos where typeOf _ = mkTyConApp typename_SourcePos ([])
strip = everywhere (mkT f) where f (TokenPos a _) = a f x = x
I know that the warnings about gunfold, toConstr and dataTypeOf are harmless but how would I define them to avoid the warnings?
Once you find out, we can implement this in Derive as deriving DataOpaque and TypeableOpaque - could be useful for some things, then you can fake up an instance with data SourcePos = WHO_CARES.
Also, the definition of strip above requires -fno-monomorphism- restriction. Should I not worry about it? The code runs just fine, locations are being stripped and tests pass.
If you eta-expand everything, i.e. strip x = everything ... x, or give it a type signature, then you don't need monomorphism. Thanks Neil