[GHC] #12646: Type family reification misses a kind signature

30 Sep 2016

      #12646: Type family reification misses a kind signature
-------------------------------------+-------------------------------------
           Reporter:  goldfire       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.2.1
          Component:  Template       |           Version:  8.0.1
  Haskell                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 If I have

 {{{
 type family F (a :: k) :: * where
     F (a :: * -> *) = Int
     F (a :: k)      = Char
 }}}

 and then print out the reification of `F`, I get (when pretty-printed)

 {{{
 type family Ghci1.F (a_0 :: k_1) :: * where
     Ghci1.F a_2 = GHC.Types.Int
     Ghci1.F a_3 = GHC.Types.Char
 }}}

 Note that the kind signature on the first variable is dropped. This is
 '''not''' the fault of the pretty-printer, as the kind signature is
 dropped in the AST as well. The reifier should include the kind signature.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12646
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