[GHC] #12131: Can't solve constraints with UndecidableSuperClasses but can infer kind (+ undesired order of kinds)

[GHC]

#12131: Can't solve constraints with UndecidableSuperClasses but can infer kind (+
undesired order of kinds)
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |             Keywords:
      Resolution:                    |  UndecidableSuperClasses, TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11480 #12025     |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * cc: ekmett (added)


Comment:

 The code in the Description is, I think, essentially the same as that in
 #11523.  In comment:14 of that ticket I explain why I think there is a
 truly infinite tower of superclasses.   If there is, GHC is likely to
 spin, and I don't know how to prevent that.

 Edward claims that there isn't an infinite tower, but I think he's wrong.
 But I believe he probably doesn't ''intend'' there to be one.  So these
 tickets are stalled on resolving the question of what is really intended
 here

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12131#comment:5>
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