[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 diatchki):

 Well, the evidence for `KnownNat` is just a simple integer, while the
 corresponding `TypeRep` is a much more heavy-weight structure, containing
 hashes, strings, etc.  Since these are created on demand for type-
 literals, we would be doing additional allocation and hashing at run-time.

 There are many cases where `KnowNat` is useful without the additional
 functionality provided by `Typeable`, so I think that the current system
 makes sense.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15322#comment:9>
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