[GHC] #10651: Type checking issue with existential quantification, rank-n types and constraint kinds

[GHC]

#10651: Type checking issue with existential quantification, rank-n types and
constraint kinds
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        Reporter:  Roboguy           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.10.1
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:                    |
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Comment (by mniip):

 > I believe that this is accepted and works as I had intended on 7.8.3
 (with the correct definition as well) after talking to some people on IRC,
 but I haven't personally tested it

 It only works with `undefined` in 7.8.3. The proper implementation fails.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10651#comment:1>
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