blob: dd6c935a1d47cbf2bc4c945d328eb25dd1d9b1c9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
{-# 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 GHC.Core.Utils
-- 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"
|