[GHC] #3765: Rules should "look through" case binders too

[GHC]

#3765: Rules should "look through" case binders too
-------------------------------------+-------------------------------------
              Reporter:  simonpj     |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  ⊥
             Component:  Compiler    |          Version:  6.12.1
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:  Runtime     |       Blocked By:
  performance bug                    |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
Changes (by thomie):

 * difficulty:   => Unknown
 * failure:  None/Unknown => Runtime performance bug


Comment:

 Confirmed in HEAD (7.9.20141130).

 For reference: the following command shows `Rule fired: dec/inc` only if
 the bang is removed.

 `$ ghc -ddump-rule-firings -fforce-recomp -O T3765.hs`

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3765#comment:1>
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