[GHC] #8978: Type synonyms in class associated types behave strangely

[GHC]

#8978: Type synonyms in class associated types behave strangely
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        Reporter:  joelteon                   |            Owner:
            Type:  bug                        |           Status:  new
        Priority:  normal                     |        Milestone:
       Component:  Compiler                   |          Version:  7.8.1
      Resolution:                             |         Keywords:
Operating System:  Unknown/Multiple           |     Architecture:
 Type of failure:  GHC rejects valid program  |  Unknown/Multiple
       Test Case:                             |       Difficulty:  Unknown
        Blocking:                             |       Blocked By:
                                              |  Related Tickets:
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Comment (by snoyberg):

 This bug has apparently broken a number of my packages, and I'm not
 certain if all of them can be fixed in a way that's backwards compatible
 with GHC 7.4 and 7.6 (both of which I still support). Would it be possible
 to release 7.8.2 with this fix alone, instead of waiting a number of
 months for the release as would normally be done?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8978#comment:10>
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