[GHC] #12729: Unlifted newtypes via GADTSyntax

[GHC]

#12729: Unlifted newtypes via GADTSyntax
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        Reporter:  monoidal          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Iceland_jack):

 See UnliftedDataTypes
 ([https://ghc.haskell.org/trac/ghc/wiki/UnliftedDataTypes#Proposal3:Allownewtypesoverunliftedtypes
 Proposal 3: Allow newtypes over unlifted types])

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12729#comment:1>
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