[GHC] #15341: :info prints kinds in closed type family equations without enabling -fprint-explicit-kinds

4 Jul 2018

      #15341: :info prints kinds in closed type family equations without enabling
-fprint-explicit-kinds
-------------------------------------+-------------------------------------
           Reporter:  RyanGlScott    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
           Keywords:  TypeFamilies   |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Load this file into GHCi:

 {{{#!hs
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE TypeFamilies #-}
 module Bug where

 type family Foo (a :: k) :: k where
   Foo a = a
 }}}

 And run `:info` on `Foo`:

 {{{
 $ /opt/ghc/8.4.3/bin/ghci Bug.hs
 GHCi, version 8.4.3: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/ryanglscott/.ghci
 [1 of 1] Compiling Bug              ( Bug.hs, interpreted )
 Ok, one module loaded.
 λ> :i Foo
 type family Foo (a :: k) :: k
   where Foo k a = a
         -- Defined at Bug.hs:5:1
 }}}

 Note that when printing the equation for `Foo`, the kind `k` is treated as
 though it were the first visible argument to `Foo`, even though `-fprint-
 explicit-kinds` is not enabled. This is because `ppr_tc_args` in
 `IfaceType` does not take `-fprint-explicit-kinds` into account.

 Patch incoming (pending a `./validate`).

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15341
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