[GHC] #9440: Buggy binder swap in occurrence analysis

[GHC]

#9440: Buggy binder swap in occurrence analysis
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              Reporter:  afarmer     |            Owner:
                  Type:  bug         |           Status:  patch
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D156   |
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Comment (by afarmer):

 (a) turned out to be easy enough, I just tagged the binders before
 checking for usage in the alt. (b) and the coercion variables required a
 slight bit of refactoring. See the Phab:D156 patch for details.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9440#comment:4>
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