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{-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
{-# LANGUAGE EmptyCase, LambdaCase #-}
{-# LANGUAGE GADTs, TypeFamilies #-}
-- Check some newtypes, in combination with GADTs and TypeFamilies
module EmptyCase002 where
import Data.Kind (Type)
newtype T = MkT H
newtype G = MkG T
newtype H = MkH G
-- Exhaustive but it cannot be detected.
f1 :: T -> a
f1 = \case
data A
data B = B1 | B2
data C :: Type -> Type where
C1 :: C Int
C2 :: C Bool
data D :: Type -> Type -> Type where
D1 :: D Int Bool
D2 :: D Bool Char
type family E (a :: Type) :: Type where
E Int = Bool
E Bool = Char
newtype T1 a = MkT1 a
newtype T2 b = MkT2 b
-- Exhaustive
f2 :: T1 A -> z
f2 = \case
-- Non-exhaustive. Missing cases: MkT1 B1, MkT1 B2
f3 :: T1 B -> z
f3 = \case
-- Non-exhaustive. Missing cases: MkT1 False, MkT1 True
f4 :: T1 (E Int) -> z
f4 = \case
-- Non-exhaustive. Missing cases: MkT1 (MkT2 (MkT1 D2))
f5 :: T1 (T2 (T1 (D (E Int) (E (E Int))))) -> z
f5 = \case
-- Exhaustive. Not an EmptyCase but good to have for
-- comparison with the example above
f6 :: T1 (T2 (T1 (D (E Int) (E (E Int))))) -> ()
f6 = \case MkT1 (MkT2 (MkT1 D2)) -> ()
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