[GHC] #15316: Regarding coherence and implication loops in presence of QuantifiedConstraints

[GHC]

#15316: Regarding coherence and implication loops in presence of
QuantifiedConstraints
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        Reporter:  mniip             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |             Keywords:
      Resolution:                    |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > This leads to a question: should forall c. c => c be an inferrable local
 axiom schema in absence of UndecidableInstances?

 I think not.  I'm busy adding a check for this case!   Agreed?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15316#comment:3>
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