[GHC] #10477: Tab-completing in a directory with Unicode heiroglyph crashes ghci

[GHC]

#10477: Tab-completing in a directory with Unicode heiroglyph crashes ghci
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              Reporter:  acfoltzer         |             Owner:
                  Type:  bug               |            Status:  new
              Priority:  normal            |         Milestone:
             Component:  GHCi              |           Version:  7.10.1
              Keywords:                    |  Operating System:  Windows
          Architecture:  Unknown/Multiple  |   Type of failure:  GHCi crash
             Test Case:                    |        Blocked By:
              Blocking:                    |   Related Tickets:
Differential Revisions:                    |
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 With a file called 𓅖.hs in `C:\Users\acfoltzer`, the following in
 `cmd.exe`:

 {{{
 C:\Users\acfoltzer>chcp 65001
 Active code page: 65001
 C:\Users\acfoltzer>ghci
 GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
 Prelude> :l C:\cygwin\home\acfoltzer\<TAB>
 ghc.exe: panic! (the 'impossible' happened)
   (GHC version 7.10.1 for i386-unknown-mingw32):
         Enum.toEnum{Word16}: tag (78166) is outside of bounds (0,65535)

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

 Here, I'm setting the code page first according to the various bits of
 folk wisdom on the Internet about getting Unicode to properly display in
 `cmd.exe`. I don't get this crash with a Cygwin terminal, but rather see
 `??.hs`.

 I came across this because I was getting the same exception in the Cryptol
 REPL, so I suspect it's not unique to GHCi, but is rather something fishy
 in base.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10477>
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