[GHC] #15782: Visible type/kind applications in declaration of data/type constructors

19 Oct 2018


      #15782: Visible type/kind applications in declaration of data/type constructors
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  TypeApplications                   |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #12045
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Two "logical" placements of visible type / kind application, in the
 declaration of data and type constructors (from
 [https://phabricator.haskell.org/D5229#144558 Phab comment]).


 {{{#!hs
 data
     Proxy :: forall k. k -> Type where
   MkProxy :: Proxy @k (a :: k)

 -- can be written

 data
     Proxy @k :: k -> Type where
   MkProxy @k :: Proxy @k (a :: k)
 }}}

 &

 {{{#!hs
 data
   Fin  :: N -> Type where
   FinO ::          Fin (S n)
   FinS :: Fin n -> Fin (S n)

 -- can be written

 data
   Fin     :: N -> Type where
   FinO @n ::          Fin (S n)
   FinS @n :: Fin n -> Fin (S n)
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15782
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