[GHC] #8634: Code valid in GHC 7.6 is impossible to move over GHC 7.7 (because of liberal coverage condition)

[GHC]

#8634: Code valid in GHC 7.6 is impossible to move over GHC 7.7 (because of
liberal coverage condition)
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        Reporter:  danilo2         |            Owner:
            Type:  bug             |           Status:  new
        Priority:  high            |        Milestone:
       Component:  Compiler        |          Version:  7.7
      Resolution:                  |         Keywords:
Operating System:                  |     Architecture:  Unknown/Multiple
  Unknown/Multiple                 |       Difficulty:  Unknown
 Type of failure:  None/Unknown    |       Blocked By:
       Test Case:                  |  Related Tickets:  #1241, #2247, #8356
        Blocking:                  |
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Comment (by rwbarton):

 Perhaps the option to emulate the GHC 7.6 behavior could be called
 `-XDysfunctionalDependencies`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8634#comment:2>
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