[GHC] #12768: 8.0.2 derives invalid code when class method is constrained by itself

[GHC]

#12768: 8.0.2 derives invalid code when class method is constrained by itself
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        Reporter:  jophish           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"e43f05b62053f4742b105636b7ebf4ce8486b13b/ghc"
 e43f05b6/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="e43f05b62053f4742b105636b7ebf4ce8486b13b"
 Add comments from Trac #12768
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12768#comment:8>
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