[GHC] #9046: Panic in GHCi when using :print

[GHC]

#9046: Panic in GHCi when using :print
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        Reporter:  quchen            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:  7.8.4
       Component:  GHCi              |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  GHCi crash        |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by bravit):

 Another strange result made visible using `-fprint-explicit-foralls`:

 {{{
 $ ghci -fprint-explicit-foralls
 GHCi, version 7.8.2: http://www.haskell.org/ghc/  :? for help

 > let a = [1]

 > :print a
 a = (_t1::Num t => [t])

 > :show bindings
 a :: forall t. Num t => [t] = _
 _t1 :: Num t => [t] = _
 }}}

 It looks like free type variable `t` in the signature of `_t1` causes GHC
 panic while typechecking it. But I can't figure out whether it is a bug of
 rtti type reconstruction in `:print` or incorrect behaviour during
 typechecking.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9046#comment:4>
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