[GHC] #9291: Don't reconstruct sum types if the type subtly changes

[GHC]

#9291: Don't reconstruct sum types if the type subtly changes
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        Reporter:  schyler           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Replying to [comment:28 simonpj]:
 > The wiki page looks plausible... but rather a lot of work for a modest
 gain.

 As Joachim hinted at above, this is also my stance. There might be some
 interesting theory here and some fun proofs, but I'm unconvinced that all
 the heavy lifting will be worth it.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9291#comment:29>
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