[GHC] #12039: Panic with partial class definition

[GHC]

#12039: Panic with partial class definition
-------------------------------------+-------------------------------------
           Reporter:  maud           |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Compiling a class with partial definition fails:

 {{{#!hs
 class A _ => B a
 }}}

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.3 for x86_64-apple-darwin):
         rnHsTyKi HsWildcardTy
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12039>
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