[GHC] #14879: QuantifiedConstraints: Big error message + can't substitute (=>) with a class alias

[GHC]

#14879: QuantifiedConstraints: Big error message + can't substitute (=>) with a
class alias
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             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 simonpj):

 > The current implementation is very impressive. If something seem
 unworkable there is surprisingly often some way to guide (trick) GHC into
 accepting it

 Well that is good news, thanks.  I hope you are going to write a paper to
 explain the uses of quantified constraints; and in there we can explore
 the boundaries and he way to guide GHC.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14879#comment:3>
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