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Simplify code for occurs check.

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This commit is contained in:
evancz 2013-01-03 00:28:54 -08:00
parent 6af3eb3f5f
commit 9ecb6a7052
1 changed files with 1 additions and 22 deletions
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23
elm/src/Types/Substitutions.hs
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@ -69,28 +69,7 @@ instance FreeVars a => FreeVars (Context a) where
instance FreeVars a => FreeVars [a] where
freeVars = concatMap freeVars
class Occurs a where
occurs :: X -> a -> Bool
instance Occurs Type where
occurs v (VarT x) = v == x
occurs v (LambdaT t1 t2) = occurs v t1 || occurs v t2
occurs v (ADT _ ts) = any (occurs v) ts
occurs v (RecordT fs t) = occurs v (concat $ Map.elems fs) || occurs v t
occurs v EmptyRecord = False
occurs v (Super _ ) = False
instance Occurs Constraint where
occurs x (t1 :=: t2) = occurs x t1 || occurs x t2
occurs x (t1 :<: t2) = occurs x t1 || occurs x t2
occurs x (y :<<: Forall xs cs t) = x == y || occurs x t || inCs
where inCs = x `notElem` xs && any (occurs x) cs
instance Occurs a => Occurs (Context a) where
occurs x (C _ _ c) = occurs x c
instance Occurs a => Occurs [a] where
occurs v = any (occurs v)
occurs x t = x `elem` freeVars t
concretize :: Scheme -> GuidCounter (Type, [Context Constraint])
concretize (Forall xs cs t) = do