[GHC] #8773: Require -XIncoherentInstances to write role annotations on class definitions

[GHC]

#8773: Require -XIncoherentInstances to write role annotations on class
definitions
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        Reporter:  goldfire          |            Owner:  goldfire
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:  7.8.1
       Component:  Compiler          |          Version:  7.8.1-rc1
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:  8745              |  Related Tickets:  #8745
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Comment (by Richard Eisenberg <eir@…>):

 In [changeset:"138297585f88351352e0ed878b25f26e1d6edfef/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="138297585f88351352e0ed878b25f26e1d6edfef"
 Fix #8773.

 To make a role annotation on a class asserting a role other than
 nominal, you now need -XIncoherentInstances. See the ticket for
 more information as to why this is a good idea.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8773#comment:4>
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