#8953: Reifying poly-kinded type families misses kind annotations -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 7.9 Haskell | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Old description:
Consider the following two modules:
{{{ {-# LANGUAGE DataKinds, PolyKinds, TypeFamilies #-}
module A where
type family Poly (a :: k) :: * type instance Poly (x :: Bool) = Int type instance Poly (x :: Maybe k) = Double }}}
{{{ {-# LANGUAGE TemplateHaskell #-}
module B where
import Language.Haskell.TH import A
$( do info <- reify ''Poly runIO $ putStrLn $ pprint info return [] ) }}}
Compiling with HEAD yields this output:
{{{ type family A.Poly (a_0 :: k_1) :: * type instance A.Poly x_2 = GHC.Types.Double type instance A.Poly x_3 = GHC.Types.Int }}}
The problem is that the type patterns in the reified instances are just plain variables, without their kind annotations. This omission makes the instance declarations unfaithful to the original meaning.
New description: Consider the following: {{{ {-# LANGUAGE DataKinds, PolyKinds, TypeFamilies, TemplateHaskell #-} import Language.Haskell.TH type family Poly (a :: k) :: * type instance Poly (x :: Bool) = Int type instance Poly (x :: Maybe k) = Double $( do info <- reify ''Poly runIO $ putStrLn $ pprint info return [] ) }}} Compiling with HEAD yields this output: {{{ type family Main.Poly (a_0 :: k_1) :: * type instance Main.Poly x_2 = GHC.Types.Double type instance Main.Poly x_3 = GHC.Types.Int }}} The problem is that the type patterns in the reified instances are just plain variables, without their kind annotations. This omission makes the instance declarations unfaithful to the original meaning. -- Comment (by goldfire): Only one module is required. Previous bug description had two. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8953#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler