[GHC] #7986: make newBroadcastTChanIO match newBroadcastTChan

[GHC]

#7986: make newBroadcastTChanIO match newBroadcastTChan
-----------------------------+----------------------------------------------
Reporter:  WrenThornton      |          Owner:                  
    Type:  bug               |         Status:  new             
Priority:  normal            |      Component:  Compiler        
 Version:  7.6.3             |       Keywords:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
 Failure:  None/Unknown      |      Blockedby:                  
Blocking:                    |        Related:                  
-----------------------------+----------------------------------------------
 While looking through the pull requests for stm-chans I came across a
 discrepancy in the new stm. Namely, we have the following definitions:

 * stm == 2.4
 {{{
     newBroadcastTChan :: STM (TChan a)
     newBroadcastTChan = do
         dummy_hole <- newTVar TNil
         write_hole <- newTVar TNil
         read <- newTVar dummy_hole
         write <- newTVar write_hole
         return (TChan read write)

     newBroadcastTChanIO :: IO (TChan a)
     newBroadcastTChanIO = do
         dummy_hole <- newTVarIO TNil
         write_hole <- newTVarIO TNil
         read <- newTVarIO dummy_hole
         write <- newTVarIO write_hole
         return (TChan read write)
 }}}

 * stm == 2.4.2
 {{{
     newBroadcastTChan :: STM (TChan a)
     newBroadcastTChan = do
         write_hole <- newTVar TNil
         read <- newTVar (error ...)
         write <- newTVar write_hole
         return (TChan read write)

     newBroadcastTChanIO :: IO (TChan a)
     newBroadcastTChanIO = do
         dummy_hole <- newTVarIO TNil
         write_hole <- newTVarIO TNil
         read <- newTVarIO dummy_hole
         write <- newTVarIO write_hole
         return (TChan read write)
 }}}

 Thus, whoever changed the definition of newBroadcastTChan in 2.4.2 forgot
 to change newBroadcastTChanIO to keep it in sync.

 PROPOSAL: I propose changing newBroadcastTChanIO to match
 newBroadcastTChan.

 ACCEPTED: +1: wren ng thornton, Edward Kmett, John Wiegley; -1: noone.

 http://www.haskell.org/pipermail/libraries/2013-May/019808.html

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7986>
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