[GHC] #12240: Common Sense for Type Classes

[GHC]

#12240: Common Sense for Type Classes
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        Reporter:  Mathnerd314       |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by adamgundry):

 * cc: adamgundry (added)


Comment:

 This is only "common sense" if you discard the open world assumption (or
 accept incoherence), neither of which are particularly palatable.

 I don't claim to have any say in whether an implementation will or will
 not be accepted, but bear in mind that new features have an ongoing cost,
 even if guarded by language flags. Feel free to work on it if you like,
 but seeking wider input first might be a good idea to avoid working on
 something that is ultimately not merged.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12240#comment:6>
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