TypeApplications-related GHC internal error
This is reproducible with GHC 8.0.1, 8.0.2, 8.2.1, and HEAD:
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
module Bug where
import Data.Coerce
class MFunctor t where
hoist :: (Monad m) => (forall a . m a -> n a) -> t m b -> t n b
newtype TaggedTrans tag trans m a = TaggedTrans (trans m a)
instance MFunctor trans => MFunctor (TaggedTrans tag trans) where
hoist = coerce
@(forall (m :: * -> *)
(n :: * -> *)
(b :: k).
Monad m =>
(forall (a :: *).
m a -> n a)
-> trans m b -> trans n b)
@(forall (m :: * -> *)
(n :: * -> *)
(b :: k).
Monad m =>
(forall (a :: *).
m a -> n a)
-> TaggedTrans tag trans m b
-> TaggedTrans tag trans n b)
hoist
GHCi, version 8.3.20170516: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Bug.hs:18:26: error:
• GHC internal error: ‘k’ is not in scope during type checking, but it passed the renamer
tcl_env of environment: [a1tR :-> Type variable ‘m’ = m,
a1tS :-> Type variable ‘n’ = n, a1tT :-> Type variable ‘b’ = b,
a1tV :-> Type variable ‘trans’ = trans,
a1tW :-> Type variable ‘tag’ = tag, a1tX :-> Type variable ‘m’ = m,
a1tY :-> Type variable ‘n’ = n, a1KE :-> Type variable ‘k’ = k,
a1KF :-> Type variable ‘k’ = k]
• In the kind ‘k’
In the type ‘(forall (m :: * -> *) (n :: * -> *) (b :: k).
Monad m =>
(forall (a :: *). m a -> n a) -> trans m b -> trans n b)’
In the expression:
coerce
@(forall (m :: * -> *) (n :: * -> *) (b :: k).
Monad m => (forall (a :: *). m a -> n a) -> trans m b -> trans n b)
@(forall (m :: * -> *) (n :: * -> *) (b :: k).
Monad m =>
(forall (a :: *). m a -> n a)
-> TaggedTrans tag trans m b -> TaggedTrans tag trans n b)
hoist
|
18 | (b :: k).
| ^
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |