[GHC] #10805: Could not deduce (a ~ b) implies (f a ~ f b), because a type function may not be injective

[GHC]

#10805: Could not deduce (a ~ b) implies (f a ~ f b), because a type function may
not be injective
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        Reporter:  htebalaka         |                   Owner:
            Type:  bug               |                  Status:  closed
        Priority:  normal            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.10.2
  checker)                           |
      Resolution:  fixed             |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 Yes, it works fine in HEAD... I checked.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10805#comment:2>
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