[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):

 PS. One bad case might be this:
 {{{
 import A
 import B
 }}}
 where
 * A imports A1 which imports A2 .. which import A20, which imports F.
 * B imports B1 which imports B2 .. which import B20, which imports F.
 }}}
 and F has the family instances.  I may have to walk down A.hi, A1.hi... to
 get to F.  But it's painful to walk down B1, B2... etc as well.

 I wonder about having a Bloom filter, which might compactly summarise the
 set of family-instance modules below M?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14759#comment:14>
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