Re: [GHC] #15592: Type families without CUSKs cannot be given visible kind variable binders

3 Oct 2018

      #15592: Type families without CUSKs cannot be given visible kind variable binders
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
                                     |  TypeApplications, TypeFamilies,
                                     |  CUSKs
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:  14880             |             Blocking:
 Related Tickets:  #15591            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):
...
In order to fix this, we'd need to be aware of the fact that a is
 mentioned explicitly in C within kcTyClGroup. Currently, kcTyClGroup
 doesn't have access to this information, however.
Hmm.  I wonder if we should simply add `a` to the `tyConScopedTyVars` of
 `T`?  And that info ''is'' available in `kcLHsTQTVars` which builds the
 `TcTyCon`.  Richard?

 Maybe that'd fix the gotcha too?

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15592#comment:10
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