[GHC] #14845: TypeInType, index GADT by constraint witness

[GHC]

#14845: TypeInType, index GADT by constraint witness
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13895            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > I suppose the difference in promoting and not promoting is in the error
 message, no?

 Indeed!  You'll get "Data constructor S can't be used in a type because
 it's a GADT" or something like tat, rather than the current mysterious
 one.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14845#comment:8>
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