[GHC] #15151: Better Interaction Between Specialization and GND

[GHC]

#15151: Better Interaction Between Specialization and GND
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        Reporter:  andrewthad        |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  Research
                                     |  needed
       Component:  Compiler          |              Version:  8.4.2
      Resolution:                    |             Keywords:  deriving
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 andrewthad):

 > In short, it feels like there ought to be a more general guiding
 principle here to determine whether two instance dictionaries are
 representationally equivalent. I'm not sure what that would be, though.

 That seems to sum up the difficulty pretty well. I agree that giving GNDed
 instances special standing would be bad (and difficult, since that's
 currently not even tracked). I have no idea what a good way to check
 instance equality would be. I don't expect that this will be doable in the
 immediate or even in the far future, but maybe it's a research problem
 someone may try to tackle one day.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15151#comment:7>
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