[GHC] #14863: QuantifiedConstraints: Can't deduce `c' from `(a, b)' and `a |- b |- c'

[GHC]

#14863: QuantifiedConstraints: Can't deduce `c' from `(a, b)' and `a |- b |- c'
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:  fixed             |             Keywords:
                                     |  QuantifiedConstraints wipT2893
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Iceland_jack):

 This is great work thanks!

 For those interested these examples came from
 [https://www.reddit.com/r/haskell/comments/6k86je/constraint_unions_bringing_or_to_the_language_of/djlghz8/
 Edward Kmett's encoding of sums of Constraints]. This may be a milestone,
 since `curryC` / `uncurryC` mean that the "category of entailment" `(:-)`
 is a Cartesian closed `Constraint` category (which means we could get
 [https://www.reddit.com/r/haskell/comments/73lp4m/higherorder_abstract_syntax_for_any/
 HOAS syntax for constraints]?).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14863#comment:6>
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