Re: [GHC] #12102: “Constraints in kin ds” illegal family application in instance ( + documentation issues?)

"GHC" <[email protected]> Wed, 06 Mar 2019 11:33:08 -0000

Newsgroups	gmane.comp.lang.haskell.glasgow.bugs
Message-ID	<[email protected]>

#12102: “Constraints in kinds” illegal family application in instance (+
documentation issues?)
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  typecheck/should_fail/T12102
      Blocked By:                    |             Blocking:
 Related Tickets:  #13780, #15872,   |  Differential Rev(s):  Phab:D5397
  #16263                             |
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I don't think we're on the same page here. This ticket and #15872
 demonstrate that constraints in kinds are horribly broken, and that
 there's no way to profitably use them. I would think that we should fix
 GHC's treatment of constraints in kinds before we document how they work
 in the users' manual.

 Unfortunately, fixing that is far beyond my technical expertise.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12102#comment:20>