[GHC] #15219: Implement UnliftedNewtypes proposal

[GHC]

#15219: Implement UnliftedNewtypes proposal
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        Reporter:  andrewthad        |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
                                     |  UnliftedNewtypes, GHCProposal
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by andrewthad):

 We will definitely need to wait until 8.8. I've made some attempts at it
 on https://phabricator.haskell.org/D4777, but it still doesn't work right.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15219#comment:6>
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