[GHC] #14048: Data instances of kind Constraint

[GHC]

#14048: Data instances of kind Constraint
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #12369            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Could you elaborate on comment:4? As in, give a program that would benefit
 from this treatment (inventing syntax as you go). I think `(=>)` should
 have kind `Constraint -> TYPE r -> Type`, and that's it. Yes, in class and
 instance heads, the symbol `=>` appears between two types of kind
 `Constraint`, but that's not properly a use of the `(=>)` operator; it's
 just a piece of concrete syntax.

 To clarify my comment:3, I do think this is a possible direction of future
 travel and would make an appropriate ghc-proposal. I'm not yet convinced
 about the idea, but my reluctance is based in personal preference/taste,
 not technical grounds.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14048#comment:5>
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