[GHC] #8427: GHC accepts invalid program because of EPS poisoning

[GHC]

#8427: GHC accepts invalid program because of EPS poisoning
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              Reporter:  errge       |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Compiler    |          Version:  7.7
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Moderate (less
       Type of failure:  GHC         |  than a day)
  accepts invalid program            |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Comment (by ezyang):

 #9422 is a duplicate of this bug, and also has a different strategy for
 solving the problem.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8427#comment:3>
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