[GHC] #11207: GHC cannot infer injectivity on type family operating on GHC.TypeLits' Nat, but can for equivalent type family operating on user-defined Nat kind

[GHC]

#11207: GHC cannot infer injectivity on type family operating on GHC.TypeLits' Nat,
but can for equivalent type family operating on user-defined Nat kind
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        Reporter:  duairc            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
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 jstolarek):

 Replying to [comment:6 goldfire]:
 > I do think that generalized injectivity is the fastest way toward what
 you want, though.
 Note however, that generalized injectivity will not make it into 8.0
 (unless miracle happens), which means over a year of waiting until it
 makes it into next stable release.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11207#comment:7>
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