[GHC] #13435: Segfaults on levity-polymorphic type class

17 Mar 2017


      #13435: Segfaults on levity-polymorphic type class
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 {{{#!hs
 {-# Language FlexibleInstances, TypeFamilies, TypeInType, MagicHash #-}

 import Data.Kind
 import GHC.Exts

 class Shw (a :: TYPE rep) where
   shw :: a -> String

 instance Int# ~ a => Shw (a :: TYPE IntRep) where
   shw a = "I#" ++ show (I# a)

 main = putStrLn (shw 3#)
 }}}

 induces a segfault

 {{{
 $ runghc --version
 runghc 8.0.1
 $ runghc test.hs
 I#Segmentation fault
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13435
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler