[GHC] #13006: Possible program should type check but does not using Implicit Parameters and Vectors

[GHC]

#13006: Possible program should type check but does not using Implicit Parameters
and Vectors
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        Reporter:  clinton           |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2-rc2
      Resolution:  invalid           |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 On the contrary, if `F` is injective then we can indeed deduce `a ~ b`
 from `F a ~ F b`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13006#comment:5>
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