[GHC] #13955: Backpack does not handle unlifted types

[GHC]

#13955: Backpack does not handle unlifted types
-------------------------------------+-------------------------------------
        Reporter:  andrewthad        |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  low               |            Milestone:
       Component:  Compiler          |              Version:  8.2.1-rc2
      Resolution:                    |             Keywords:  backpack
                                     |  LevityPolymorphism
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ezyang):

 Yeah, this doesn't look something GHC allows right now, because `data`
 declarations have to have kind `*`, and there is no way to define an
 abstract type with different kind. But it seems like it should be
 possible, we just have to relax some of the checks GHC does.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13955#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler