[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:  RolandSenn
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       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 RolandSenn):

 @monoidal:

 > Fixing this will likely also fix #12509

 Unfortunately not...

 #12509 does not enter `loadSrcInterface_maybe` because of `not
 (safeDirectImpsReq dflags)`.
 However, this ticket fails somewhere in a subfunction of
 `loadSrcInterface_maybe`.

 {{{
 Code from compiler/rename/RnEnv.hs:

 lookupQualifiedNameGHCi :: RdrName -> RnM [Name]
 lookupQualifiedNameGHCi rdr_name
   = -- We want to behave as we would for a source file import here,
     -- and respect hiddenness of modules/packages, hence loadSrcInterface.
     do { dflags  <- getDynFlags
        ; is_ghci <- getIsGHCi
        ; go_for_it dflags is_ghci }

   where
     go_for_it dflags is_ghci
       | Just (mod,occ) <- isQual_maybe rdr_name
       , is_ghci
       , gopt Opt_ImplicitImportQualified dflags   -- Enables this GHCi
 behaviour
       , not (safeDirectImpsReq dflags)            -- See Note [Safe
 Haskell and GHCi]
       = do { res <- loadSrcInterface_maybe doc mod False Nothing

       <...etc...>

 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15336#comment:7>
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