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feat: Polymorphic Elem for Union (#1637)

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Close https://github.com/haskell-servant/servant/issues/1590
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Guillaume Bouchard 2022-12-23 09:42:52 +01:00 committed by GitHub
parent 6392dce4bf
commit a4194dc490
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1 changed files with 2 additions and 2 deletions
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4
servant/src/Servant/API/UVerb/Union.hs
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@ -128,9 +128,9 @@ type DuplicateElementError (rs :: [k]) =
':$$: 'Text " " ':<>: 'ShowType rs ':$$: 'Text " " ':<>: 'ShowType rs
type family Elem (x :: k) (xs :: [k]) :: Bool where type family Elem (x :: k) (xs :: [k]) :: Bool where
Elem x (x ': _) = 'True
Elem x (_ ': xs) = Elem x xs
Elem _ '[] = 'False Elem _ '[] = 'False
Elem x (x' ': xs) =
If (x == x') 'True (Elem x xs)
type family Unique xs :: Constraint where type family Unique xs :: Constraint where
Unique xs = If (Nubbed xs == 'True) (() :: Constraint) (TypeError (DuplicateElementError xs)) Unique xs = If (Nubbed xs == 'True) (() :: Constraint) (TypeError (DuplicateElementError xs))