[GHC] #11348: Local open type families instances ignored during type checking

[GHC]

#11348: Local open type families instances ignored during type checking
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        Reporter:  alexvieth         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Yay yay yay. Thanks! The issue here is a known infelicity, but it seemed
 to me that fixing it would take a fair amount of reinstallation of
 plumbing. I think you'll have to type-check instance declarations (the
 first of the two passes in !TcInstDcls) in with mutually recursive groups.
 A type whose kind mentions an open type family depends on the instances of
 that family.

 If you're up to this task, that would be wonderful. I'm more than happy to
 advise.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11348#comment:2>
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