[GHC] #11031: Record Pattern Synonym Cleanup

[GHC]

#11031: Record Pattern Synonym Cleanup
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           Reporter:  mpickering     |             Owner:
               Type:  task           |            Status:  new
           Priority:  low            |         Milestone:
          Component:  Compiler       |           Version:  7.10.2
           Keywords:  newcomer       |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Ben comments that there are some loose ends with record pattern synonyms.


 * It's still not clear to me that the free variables produced in
 rnPatSynBind are correct
 * Perhaps in the future we want to refactor tc_single to use a function
 which extends the typechecking environment instead of using setGblEnv
 * @mpickering's suggested refactoring of RecSelId to RecSelId (Either
 PatSyn TyCon) Bool described in the comment in TcExpr.hs
 * There is a TODO in tc_patsyn_finish which should either be clarified so
 it can be considered actionable, removed, or just fixed


 The comment from TcExpr was:

 > I tried to refactor RecSelId to RecSelId [DataCon] Bool but this causes
 some pain when it comes to the interface files. Next try it is something
 like RecSelId (Either PatSyn TyCon) Bool with the aim for something better
 in the future.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11031>
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