`Language.Haskell.TH.Syntax.reify` returns * rather than Constraint
This module is sufficient to demonstrate the mistake:
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TemplateHaskell #-}
module Bug where
import Data.Kind
import Data.Proxy
import Language.Haskell.TH
foo :: forall (k :: Constraint). Proxy k
foo = Proxy
return [] -- delimit declaration groups
main :: IO ()
main = putStrLn $(do
VarI _ ty _ <- reify 'foo
let p = pprint ty
[| p |])
Running this in GHC 8.0.2 correctly prints out forall (k_0 :: Constraint) . Data.Proxy.Proxy k_0
, but GHC 8.2.2 and 8.4.2 both print forall (k_0 :: *) . Data.Proxy.Proxy k_0
.
Trac metadata
Trac field | Value |
---|---|
Version | 8.4.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Template Haskell |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |