[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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"a94b484715d3caf445a7069377d5311e0e50f66e/ghc"
 a94b4847/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a94b484715d3caf445a7069377d5311e0e50f66e"
 Back-pedal the fix for Trac #8155

 I implemented a rather elaborate fix for #8155 ages ago, which
 which turns out to be
   a) unnecesssary in this particular case
   b) harmful to the defaulting story; see comment:15 of #12923.

 So this patch reverts the elaborate bit. The bit I removed is
 described in "Historical note" under Note [approximateWC].
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12923#comment:18>
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