[GHC] #15322: `KnownNat` does not imply `Typeable` any more when used with plugin

[GHC]

#15322: `KnownNat` does not imply `Typeable` any more when used with plugin
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        Reporter:  chshersh          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
                                     |  typeable,knownnat
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10348            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by LeanderK):

 You are right, the issue mostly stems from the fact (I think? At least
 that is the most common problem where it all breaks down) that I can't
 convince the typechecker that things defined by induction (through 0 and
 (n+1)) are valid and hold for every n.

 I have no idea what the best technical solution would be. I am just a
 user. Here's a related issue: https://github.com/clash-lang/ghc-typelits-
 natnormalise/issues/13, which is very similar to the usual pains when I
 use type-level nats.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15322#comment:18>
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