[GHC] #12055: Typechecker panic instead of proper error

[GHC]

#12055: Typechecker panic instead of proper error
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash                              |  polykinds/T12055, T12055a
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by simonpj):

 * testcase:   => polykinds/T12055, T12055a


Comment:

 I've added two regressions test.

 HEAD is fine, but there really is a bug in GHC 8.0, producing "GHC
 internal error" when `FlexibleContexts` is omitted.  It doesn't look that
 high a priority to me.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12055#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler