[GHC] #11341: Reifying a GADT doesn't tell you the correct return type

2 Jan 2016

      #11341: Reifying a GADT doesn't tell you the correct return type
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           Reporter:  RyanGlScott    |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Template       |           Version:  8.1
  Haskell                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Running this example:

 {{{#!hs
 {-# LANGUAGE GADTs, TemplateHaskell #-}
 module Main (main) where

 import Language.Haskell.TH

 type S = T

 data T a where
     MkT :: S Int

 $(return [])

 main :: IO ()
 main = putStrLn $(reify ''T >>= stringE . pprint)
 }}}

 gives the following result:

 {{{
 data Main.T (a_0 :: *) where Main.MkT :: Main.T GHC.Types.Int
 }}}

 Shouldn't the return type be `Main.S GHC.Types.Int` instead?

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11341
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