Test Trac #6035, #6036

testsuite/tests/polykinds/T6035.hs

+{-# LANGUAGE PolyKinds, DataKinds, TypeFamilies, KindSignatures, GADTs,  TypeOperators
+  #-}
+
+module T6035 where
+
+data Nat = Zero | Succ Nat
+
+type family Sing (a :: k) :: k -> *
+
+data SNat n where
+  SZero :: SNat Zero
+  SSucc :: SNat n -> SNat (Succ n)
+
+data SList (a :: [k]) where
+  SNil :: SList '[]
+  SCons :: Sing h h -> SList t -> SList (h ': t)
+
+type instance Sing (a :: Nat) = SNat
+type instance Sing (a :: [k]) = SList
+
+nil :: SList '[]
+nil = SNil
+
+zero :: SList '[ '[] ]
+zero = SCons SNil SNil
+
+term :: SList '[ '[Zero], '[]]
+term = SCons (SCons SZero SNil) (SCons SNil SNil)

testsuite/tests/polykinds/T6036.hs

+{-# LANGUAGE DataKinds, TypeFamilies, PolyKinds, GADTs #-}
+
+module T6036 where
+
+data family Sing (a :: k)
+
+data instance Sing (a :: Maybe k) where
+  SNothing :: Sing 'Nothing
+  SJust :: Sing b -> Sing ('Just b)
+
+data Nat = Zero | Succ Nat
+
+data instance Sing (a :: Nat) where
+  SZero :: Sing Zero
+  SSucc :: Sing n -> Sing (Succ n)
+
+term = SJust SZero