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{-# LANGUAGE CPP, TypeFamilies, FlexibleContexts #-}
module Class ( cleverNamedResolve ) where
data FL p = FL p
class PatchInspect p where
instance PatchInspect p => PatchInspect (FL p) where
type family PrimOf p
type instance PrimOf (FL p) = PrimOf p
data WithName prim = WithName prim
instance PatchInspect prim => PatchInspect (WithName prim) where
class (PatchInspect (PrimOf p)) => Conflict p where
resolveConflicts :: p -> PrimOf p
instance Conflict p => Conflict (FL p) where
resolveConflicts = undefined
type family OnPrim p
joinPatches :: p -> p
joinPatches = id
cleverNamedResolve :: (Conflict (OnPrim p)
,PrimOf (OnPrim p) ~ WithName (PrimOf p))
=> p -> FL (OnPrim p) -> WithName (PrimOf p)
cleverNamedResolve x = resolveConflicts . joinPatches
-- I added the parameter 'x' to make the signature unambiguous
-- I don't think that ambiguity is essential to the original problem
{-
resolveConflicts :: q -> PrimOf q
(w) FL (OnPrim p) ~ q
(w) WithName (PrimOf p) ~ PrimOf q
==>
(w) PrimOf (OnPrim p) ~ PrimOf (FL (OnPrim p))
==>
(w) PrimOf (OnPrim p) ~ PrimOf (OnPrim p)
-}
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