[GHC] #12923: MultiParamTypeClasses + ExtendedDefaultRules

[GHC]

#12923: MultiParamTypeClasses + ExtendedDefaultRules
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        Reporter:  amindfv           |                Owner:
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.2.1
       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):  Phab:D2822
       Wiki Page:                    |
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Comment (by simonpj):

 Turns out that back-pedaling on #8155 doesn't break #8155!  So I'm going
 to do that.  It's no documented feature, and it'll make more programs do
 defaulting.

 That leaves your tiny patch.  It is no so small, and so well defined, that
 I think we should go ahead.  Please do the user manual stuff and then we
 can land it.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12923#comment:17>
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