[GHC] #9991: runghc shows the value produced by main when its type is a non-() Show instance

[GHC]

#9991: runghc shows the value produced by main when its type is a non-() Show
instance
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        Reporter:  shachaf           |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Changes (by ezyang):

 * type:  bug => task


Comment:

 Looks fixed in 7.10, but we could still use a test.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9991#comment:1>
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