[GHC] #11635: Higher-rank kind in datatype definition rejected

[GHC]

#11635: Higher-rank kind in datatype definition rejected
-------------------------------------+-------------------------------------
        Reporter:  phadej            |                Owner:  goldfire
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc2
      Resolution:  fixed             |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  GHC rejects       |            Test Case:
  valid program                      |  dependent/should_compile/T11635
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * status:  merge => closed
 * failure:  None/Unknown => GHC rejects valid program
 * resolution:   => fixed
 * milestone:   => 8.0.1


@@ -3,1 +3,1 @@
- {{{
+ {{{#!hs

New description:

 Example program:

 {{{#!hs
 {-# LANGUAGE TypeInType, KindSignatures, ExplicitForAll #-}
 import Data.Kind
 data X (a :: forall k. k -> * ) = X
 }}}

 errors with

 {{{
 polykind.hs:3:1: error:
     Expecting one more argument to ‘a’
     Expected kind ‘k0’, but ‘a’ has kind ‘forall k. k -> *’
 }}}

 Without `TypeInType`, the error is better, yet gives false hint:

 {{{
 polykind.hs:3:23: error:
     Illegal kind: forall k. k -> *
     Did you mean to enable TypeInType?
 }}}

 ---

 For the record 7.10.3 doesn't recognise polymorphic kinds at all (same
 program, without `Data.Kind` import):

 {{{
 polykind.hs:3:23: parse error on input ‘forall’
 }}}

 Which makes me think that polymorphic kinds are somehow supported, but
 maybe not.

--

Comment:

 Merged as bae60f654ac5d99834818da9c50ad4bee54c334e.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11635#comment:7>
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