[GHC] #13130: atomicModifyMutVar# has incorrect type

[GHC]

#13130: atomicModifyMutVar# has incorrect type
-------------------------------------+-------------------------------------
           Reporter:  carter         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.2.1
          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:
-------------------------------------+-------------------------------------
 this ticket

 specifically, currently we only expose in ghc-prim

 {{{
 atomicModifyMutVar# :: MutVar# s a -> (a -> b) -> State# s -> (# State#
 s,c #)
 }}}


 is the type more like the following?
 {{{
 atomicModifyMutVar# :: MutVar# s a -> (a -> (#a,b #)) -> State# s -> (#
 State# s,b #)
 }}}

 looking at GHC.IOREF
 {{{
 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r#
 f s
 }}}

 it seems that either way, something screwy is afoot

 i'm not sure where the spurious c type variable comes from

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13130>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler