[GHC] #13135: Typechecker "panic! the 'impossible' happened"

[GHC]

#13135: Typechecker "panic! the 'impossible' happened"
-------------------------------------+-------------------------------------
        Reporter:  Saulzar           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |
      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 RyanGlScott):

 To be precise, here's the particular panic it gives:

 {{{
 $ /opt/ghc/8.0.2/bin/ghci NanoFeldspar.hs GHCi, version 8.0.2:
 http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling NanoFeldspar     ( NanoFeldspar.hs, interpreted )

 NanoFeldspar.hs:122:10: error:ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         No skolem info: t_a2xN
 }}}

 Reproducible on GHC 8.0.1, 8.0.2, and HEAD.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13135#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler