[GHC] #11346: GHCi can crash when tabbing a filename

[GHC]

#11346: GHCi can crash when tabbing a filename
------------------------------+-------------------------------
           Reporter:  honnza  |             Owner:
               Type:  bug     |            Status:  new
           Priority:  normal  |         Milestone:
          Component:  GHCi    |           Version:  7.6.3
           Keywords:          |  Operating System:  Windows
       Architecture:  x86     |   Type of failure:  GHCi crash
          Test Case:          |        Blocked By:
           Blocking:          |   Related Tickets:
Differential Rev(s):          |         Wiki Page:
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 The following sequence of actions:

 1. Type `:: I` into GHCI
 2. Press the tab key
 3. Hold backspace to erase the resulting text
 4. Repeat steps 2 and 3

 May result in the following appearing in the console:

 {{{
 Prelude Data.Map> :: ImageExpo.config ghc.exe: panic! (the 'impossible'
 happened)
   (GHC version 7.6.3 for i386-unknown-mingw32):
         Prelude.chr: bad argument: (-947713851)

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 followed by the system prompt.

 Afterwards I have realised that `::` was actually interpreted as a GHCi
 command rather than the type designation syntax. Tabbing yields all files
 in the current directory, but actually performing the command yields
 `unknown command '::'`

 There is only one file that starts with `I` in my current directory.

 Did not manage to reproduce

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11346>
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