[GHC] #12128: ghci cause panic on 8.0.1

[GHC]

#12128: ghci cause panic on 8.0.1
-------------------------------------+-------------------------------------
        Reporter:  zxtx              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by seraphime):

 Seems to be a regression introduced in
 1c9fd3f1c5522372fcaf250c805b959e8090a62c : Case-of-empty-alts is trivial
 (Trac #11155).

 Removing the line:

 {{{

 cpe_ExprIsTrivial (Case e _ _ []) = cpe_ExprIsTrivial e
 }}}


 Fixes the issue, but breaks T11155 and T12212 in HEAD.

 I'm trying to find a workaround.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12128#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler