blob: 662fa66022a06c719370cc184bc094fcf0e381b8 (
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
|
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE BangPatterns #-}
{- # OPTIONS_GHC -Werror #-}
{-# OPTIONS_GHC -g -O2 #-}
module Bug (bug) where
-- import GHC.Base (seq)
import Unsafe.Coerce (unsafeCoerce)
undefined :: a
undefined = undefined
data TypeRep (a :: k) where
TrTyCon :: TypeRep (a :: k)
TrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1).
TypeRep (a b)
data SomeTypeRep where
SomeTypeRep :: forall k (a :: k).
TypeRep a
-> SomeTypeRep
mkTrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1).
TypeRep (a :: k1 -> k2)
-> TypeRep (a b)
mkTrApp TrTyCon = undefined
mkTrApp TrApp = undefined
bug :: SomeTypeRep
-- bug = f x -- this works
bug = f (f x)
where x = SomeTypeRep TrTyCon
f :: SomeTypeRep -> SomeTypeRep
f (SomeTypeRep acc) = SomeTypeRep (mkTrApp (unsafeCoerce acc))
|
