[GHC] #11291: DfltProb1(optasm): panic CoreToStg.myCollectArgs

[GHC]

#11291: DfltProb1(optasm): panic CoreToStg.myCollectArgs
-------------------------------------+-------------------------------------
           Reporter:  thomie         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  highest        |         Milestone:  8.0.1
          Component:  Compiler       |           Version:  7.11
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
  typecheck/should_compile/DfltProb1 |
  (optasm)                           |
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The program looks like this:
 {{{
 module DfltProb1 where

 import Control.Monad.ST
 import Prelude hiding (traverse)

 traverse :: a -> ST s [a]
 traverse = undefined

 -- WORKS with signature test :: Num a => [a]
 test = runST (traverse 1)

 main = print test
 }}}

 This is the failure:
 {{{
 $ ghc-7.11.20151225 -O DfltProb1.hs
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.11.20151224 for x86_64-unknown-linux):
         CoreToStg.myCollectArgs
   (case traverse of _ [Occ=Dead] { }) realWorld#
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11291>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler