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{-# LANGUAGE ExistentialQuantification, TypeFamilies #-}
-- Tests a nasty case where 'exprType' or 'coreAltsType' can
-- return a type that mentions an out-of-scope type variable
-- because of a type synonym that discards one of its arguments
--
-- See Note [Existential variables and silly type synonyms]
-- in CoreUtils
-- In GHC 6.10, both tests below (independently) give Lint errors
module T3409 where
--------------------------
-- Simpler version not involving type families
data T = forall a. T a (Funny a)
type Funny a = Bool
f :: T -> Bool
f (T x n) = n
--------------------------
-- Cut down version of the original report
newtype Size s = Size Int
data ArrayS d e = ArrayS d e
data Array1 e = forall s . Array1 (Size s) (ArrayS (Size s) e)
-- Array1 :: forall e s. Size s -> ArrayS (Size s) e -> Array1 e
copy :: Int -> Array1 a -> Array1 a
copy _ (Array1 s a) = Array1 s $ (ArrayS s (bang a))
-- Array1 s :: ArrayS (Size s) a -> Array1 a
-- s :: Size s
-- a :: ArrayS (Size s) a
-- ArrayS :: Size s -> a -> ArrayS (Size s) a
-- i :: AccessIx (ArrayS (Size s) a) = Ix s
-- bang a :: AccessResult (ArrayS (Size s) a) = a
-- ArrayS s (bang a) :: ArrayS (Size s) (AccessResult (ArrayS (Size s) a))
class Access a where
type AccessResult a
bang :: a -> AccessResult a
instance Access (ArrayS d a) where
type AccessResult (ArrayS d a) = a
bang = error "urk"
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