Odd pretty printing of equality constraint in kind ('GHC.Types.Eq# <>)
Maybe indicative of deeper issues:
{-# Language RankNTypes #-}
{-# Language DataKinds #-}
{-# Language PolyKinds #-}
{-# Language GADTs #-}
import Data.Kind
data WHICH = OP | OPOP
data Fun :: forall (a :: WHICH). a ~ OP => Type -> Type -> Type where
MkFun :: (a -> b) -> Fun a b
There are some artifacts Fun ('GHC.Type.Eq# <>)
in the type of MkFun
that shouldn't be there
$ ~/code/unmodifiedghc/inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci ~/hs/655_bug.hs
GHCi, version 8.7.20181029: http://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Main ( /home/baldur/hs/655_bug.hs, interpreted )
Ok, one module loaded.
*Main> :t MkFun
MkFun :: (a -> b) -> Fun ('GHC.Types.Eq# <>) a b
*Main> :k Fun
Fun :: (a ~ 'OP) => * -> * -> *
*Main>
Tangent: Omitting {-# Language GADTs #-}
we get the term "equational constraint" which is not the term I have seen in the wild
$ latestbug 655_bug.hs
GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Main ( 655_bug.hs, interpreted )
655_bug.hs:9:1: error:
Illegal equational constraint a ~ 'OP
(Use GADTs or TypeFamilies to permit this)
|
9 | data Fun :: forall (a :: WHICH). a ~ OP => Type -> Type -> Type where
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
Failed, no modules loaded.
Prelude>
Trac metadata
Trac field | Value |
---|---|
Version | 8.6.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |