[GHC] #12923: MultiParamTypeClasses + ExtendedDefaultRules

[GHC]

#12923: MultiParamTypeClasses + ExtendedDefaultRules
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        Reporter:  amindfv           |                Owner:
            Type:  feature request   |               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:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 What, precisely, would you like the defaulting rule to be?

 Ideally, express your proposed rule(s) in the same way as [the user manual
 does](https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html
 #type-defaulting-in-ghci).  Thanks.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12923#comment:2>
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