[GHC] #8447: A combination of type-level comparison and subtraction does not work for 0

[GHC]

#8447: A combination of type-level comparison and subtraction does not work for 0
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        Reporter:  nushio                     |            Owner:
            Type:  bug                        |           Status:  new
        Priority:  low                        |        Milestone:
       Component:  Compiler (Type checker)    |          Version:  7.6.3
      Resolution:                             |         Keywords:
Operating System:  Linux                      |     Architecture:
 Type of failure:  GHC rejects valid program  |  Unknown/Multiple
       Test Case:                             |       Difficulty:  Unknown
        Blocking:                             |       Blocked By:
                                              |  Related Tickets:
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Comment (by carter):

 This seems to tie into having good coverage checking for pattern matching,
 at least naively. (and the fact that we currently don't really have a
 solver for type level nats). thoughts?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8447#comment:2>
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