[GHC] #15336: ./System/IO.hs accidentally overridden when running ghci

[GHC]

#15336: ./System/IO.hs accidentally overridden when running ghci
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        Reporter:  luqui             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  GHCi              |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  MacOS X           |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by monoidal):

 Fixing this will likely also fix #12509.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15336#comment:4>
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