[GHC] #13381: "opt_univ fell into a hole" panic from rewrite rule

[GHC]

#13381: "opt_univ fell into a hole" panic from rewrite rule
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 To be clear, the `opt_univ fell into a hole` bit is a red herring here.
 The real problem is that the type-checker doesn't reject the program.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13381#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler