[GHC] #13981: Family instance consistency checks happens too early when hs-boot defined type occurs on LHS

[GHC]

#13981: Family instance consistency checks happens too early when hs-boot defined
type occurs on LHS
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        Reporter:  ezyang            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:  hs-boot
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 >  right now, we decide to defer a type family consistency check if the
 family was recursively defined.

 I don't like the sound of that.  Strange deferring under special
 circumstances.  Can we figure out a more uniform approach?

 I've lost context here.  In your example, modules `B` and `C` seem to have
 no overlap problem, but `A` does.   Can you set out the problem you are
 trying to solve, ab-initio?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13981#comment:1>
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