[GHC] #11639: `:print` being wacky

[GHC]

#11639: `:print` being wacky
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           Reporter:  TheKing42         |             Owner:
               Type:  bug               |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  Compiler          |           Version:  7.10.3
           Keywords:                    |  Operating System:  Linux
       Architecture:  Unknown/Multiple  |   Type of failure:  GHCi crash
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:
Differential Rev(s):                    |         Wiki Page:
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 {{{
 $ ghci
 GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
 Prelude> let x = 1:x
 Prelude> :print x
 x = (_t1::Num a => [a])
 Prelude> head _t1
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.3 for x86_64-unknown-linux):
         tcTyVarDetails a_avB

 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/11639>
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