[GHC] #9293: GHCI :unset -XLanguageExtension returns "don't know how to reverse -XLanguageExtension"

[GHC]

#9293: GHCI :unset -XLanguageExtension returns "don't know how to reverse
-XLanguageExtension"
-------------------------+-------------------------------------------------
       Reporter:         |             Owner:
  jfeltz                 |            Status:  new
           Type:  bug    |         Milestone:
       Priority:         |           Version:  7.8.2
  normal                 |  Operating System:  Unknown/Multiple
      Component:  GHCi   |   Type of failure:  None/Unknown
       Keywords:         |         Test Case:  :set -XCPP followed by
   Architecture:  x86    |  :unset -XCPP
     Difficulty:         |          Blocking:
  Unknown                |
     Blocked By:         |
Related Tickets:         |
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 Any language extension tried appears to not work with :unset. To make
 matters worse, :unset expands to a number of options, misleading the user
 into thinking that it should (if that is the case). I eventually had to
 ask someone on IRC #haskell, leading to the :set -XNoLanguageExtension
 trick to do what I needed. A fix to :unset is suggested, or removing the
 misleading/non-working command.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9293>
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The Glasgow Haskell Compiler