[GHC] #11435: Evidence from TC Plugin triggers core-lint warning

[GHC]

#11435: Evidence from TC Plugin triggers core-lint warning
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        Reporter:  jbracker          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:  core-lint
                                     |  warning evidence type-checker
                                     |  plugin
Operating System:  Linux             |         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 thomie):

 `-fno-opt-coercion` makes the problem go away. Tested with ghc-7.10.3.

 The plugin doesn't compile with GHC 8 or HEAD, without significant
 changes.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11435#comment:2>
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