[GHC] #8958: Allow role inference on datatype contexts

[GHC]

#8958: Allow role inference on datatype contexts
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        Reporter:  goldfire                    |            Owner:
            Type:  feature request             |           Status:  new
        Priority:  normal                      |        Milestone:  7.8.1
       Component:  Compiler                    |          Version:
      Resolution:                              |  7.8.1-rc2
Operating System:  Unknown/Multiple            |         Keywords:
 Type of failure:  None/Unknown                |     Architecture:
       Test Case:  roles/should_compile/T8958  |  Unknown/Multiple
        Blocking:                              |       Difficulty:  Unknown
                                               |       Blocked By:
                                               |  Related Tickets:
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Changes (by simonpj):

 * owner:  goldfire =>
 * status:  closed => new
 * resolution:  fixed =>


Comment:

 I can see the motivation here, though it is a grievous hack.

 But it needs documenting in the user manual!

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8958#comment:4>
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