[GHC] #7414: plugins always trigger recompilation

[GHC]

#7414: plugins always trigger recompilation
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        Reporter:  jwlato            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.6.1
      Resolution:                    |             Keywords:  plugin,
                                     |  recompilation
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 Related #7277, which has the opposite problem where rely only on the
 interface hash (and not an "implementation" hash.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7414#comment:7>
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