[GHC] #16255: Visible kind application defeats type family with higher-rank result kind

[GHC]

#16255: Visible kind application defeats type family with higher-rank result kind
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.7
  checker)                           |             Keywords:
      Resolution:                    |  TypeApplications, TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15740            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Ah, I just realized the answer to my own question: this information is
 (indirectly) stored in the `tyConBinders` of the type family tycon. We'd
 have to do a little bit of reverse engineering to recover which type
 patterns had which visibility, but it should be possible (I think).

 Another challenge is figuring out a good `SrcSpan` to use in the error
 message, which we don't have any location info in `TcValidity`. Maybe
 we'll just have to settle for the `SrcSpan` of the entire type family
 equation?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16255#comment:5>
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