[GHC] #10833: Use injective type families when dealing with givens

[GHC]

#10833: Use injective type families when dealing with givens
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        Reporter:  jstolarek         |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.10.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #6018             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 I don't think this relates to
 [[http://www.win.tue.nl/rtaloop/problems/79.html|RTA #79]]. (The soundness
 of type families + `UndecidableInstances` + non-linear patterns does.)
 Perhaps more sweat on the proof would yield fruit. But somehow it failed
 to succumb, and so I'm wary of putting it in Core.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10833#comment:2>
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