[GHC] #15673: ghc: panic! (the 'impossible' happened)

[GHC]

#15673: ghc: panic! (the 'impossible' happened)
--------------------------------------+---------------------------------
           Reporter:  mcmayer         |             Owner:  (none)
               Type:  bug             |            Status:  new
           Priority:  normal          |         Milestone:  8.4.4
          Component:  Compiler        |           Version:  8.4.3
           Keywords:                  |  Operating System:  MacOS X
       Architecture:  x86_64 (amd64)  |   Type of failure:  None/Unknown
          Test Case:                  |        Blocked By:
           Blocking:                  |   Related Tickets:
Differential Rev(s):                  |         Wiki Page:
--------------------------------------+---------------------------------
 The following few lines produce a GHC panic:

 {{{#!hs
 module Main where

 import Data.Bits (shift)

 badOne :: [Int] -> Integer
 badOne is = sum $ zipWith (\n _->shift 1 n) (enumFrom 0) is

 main = return () :: IO ()
 }}}

 The function is stripped down as much as possible, it doesn't perform
 anything all to meaningful anymore.

 The error message is:

 {{{#!bash
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.4.3 for x86_64-apple-darwin):
         heap overflow
 }}}

 All else is off-the-shelf stack lts-12.10 via

 {{{#!bash
 stack new bad-one simple
 }}}

 Tested on Mac OS X and Debian.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15673>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler