[GHC] #14759: ListSetOps WARNING causes tests to fail

[GHC]

#14759: ListSetOps WARNING causes tests to fail
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        Reporter:  ezyang            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4628
       Wiki Page:                    |
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Comment (by simonpj):

 > I think you could mitigate this particular bad case if you did "path
 compression", that is instead of keeping the finst-flag, you remembered
 the first "interesting" module - a module that either defines it's own
 family instances or imports two modules with different "interesting"
 modules

 Interesting idea. Do you feel inclined to work on it?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14759#comment:16>
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