[GHC] #12942: Add infix flag for class and data declarations

[GHC]

#12942: Add infix flag for class and data declarations
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        Reporter:  alanz             |                Owner:  alanz
            Type:  task              |               Status:  new
        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:  #3384             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by alanz):

 The additional `HasOccNameId`constraints were introduced in Phab:D2752,
 this patch should remove them again.

 E.g.

 {{{#!hs
 pp_vanilla_decl_head :: (OutputableBndrId name, HasOccNameId name)
    => Located name
    -> LHsQTyVars name
    -> HsContext name
    -> SDoc
 pp_vanilla_decl_head thing (HsQTvs { hsq_explicit = tyvars }) context
  = hsep [pprHsContext context, pp_tyvars tyvars]
   where
     pp_tyvars (varl:varsr)
       | isSymOcc $ occName (unLoc thing)
          = hsep [ppr (unLoc varl), pprInfixOcc (unLoc thing)
          , hsep (map (ppr.unLoc) varsr)]
       | otherwise = hsep [ pprPrefixOcc (unLoc thing)
                   , hsep (map (ppr.unLoc) (varl:varsr))]
     pp_tyvars [] = ppr thing
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12942#comment:2>
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