[GHC] #10607: Auto derive from top to bottom

[GHC]

#10607: Auto derive from top to bottom
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        Reporter:  songzh            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:  deriving,
                                     |  typeclass, auto
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 RyanGlScott):

 I'm quite reluctant to steal wildcard syntax for this particular purpose,
 because it's conceivable that in the future, we might want to allow GHC to
 fill in this wildcard, producing an error to the effect of:

 {{{
 • Found type wildcard ‘_’ standing for ‘(C a, C b, C c)’
   To use the inferred type, enable PartialTypeSignatures
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10607#comment:14>
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