[GHC] #9802: A ghci bug

[GHC]

#9802: A ghci bug
-------------------------------------+-------------------------------------
       Reporter:  vxanica            |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  GHCi               |                 Version:  7.8.3
       Keywords:  :force :type       |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:
     Blocked By:                     |  None/Unknown
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 Prelude> let a = [1,2,3]
 (0.00 secs, 0 bytes)
 Prelude> :t a
 a :: Num t => [t]
 Prelude> :force a
 a = _
 Prelude> a
 [1,2,3]
 (0.02 secs, 3580816 bytes)
 Prelude> :print a
 a = (_t1::Num t => [t])
 Prelude> :t _t1
 ghc.exe: panic! (the 'impossible' happened)
   (GHC version 7.8.3 for x86_64-unknown-mingw32):
         tcTyVarDetails t{tv auB} [tv]


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

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9802>
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