[GHC] #12662: Investivate ListSetOps module

[GHC]

#12662: Investivate ListSetOps module
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           Reporter:  mpickering     |             Owner:
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  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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 It seems that the `ListSetOps` module is very inefficient and there are
 probably better ways to do what it does elsewhere in GHC. This is an open
 ended ticket to:

 1. Investigate where functions from `ListSetOps` are used in GHC.
 2. Investigate how easy it is to remove the usages of these functions.
 3. Remove the module if it is feasible to do so.

 Seems like it might be good for a newcomer? Someone else can tag it so if
 they agree.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12662>
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