git.iko.soy/servant
on master help sign in
feat: Polymorphic `Elem` for `Union` (#1637)
a4194dcGuillaume Bouchard
servant/src/Servant/API/UVerb/Union.hs+2−2
compare with master
unifiedsplit
@@ -128,9 +128,9 @@ type DuplicateElementError (rs :: [k]) =
128 ':$$: 'Text " " ':<>: 'ShowType rs
128 ':$$: 'Text " " ':<>: 'ShowType rs
129
129
130type family Elem (x :: k) (xs :: [k]) :: Bool where
130type family Elem (x :: k) (xs :: [k]) :: Bool where
131+ Elem x (x ': _) = 'True
132+ Elem x (_ ': xs) = Elem x xs
131 Elem _ '[] = 'False
133 Elem _ '[] = 'False
132− Elem x (x' ': xs) =
133− If (x == x') 'True (Elem x xs)
134
134
135type family Unique xs :: Constraint where
135type family Unique xs :: Constraint where
136 Unique xs = If (Nubbed xs == 'True) (() :: Constraint) (TypeError (DuplicateElementError xs))
136 Unique xs = If (Nubbed xs == 'True) (() :: Constraint) (TypeError (DuplicateElementError xs))