[GHC] #3049: STM with data invariants crashes GHC

[GHC]

#3049: STM with data invariants crashes GHC
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    Reporter:  simonpj           |        Owner:                  
        Type:  bug               |       Status:  new             
    Priority:  normal            |    Milestone:  6.12.1          
   Component:  Compiler          |      Version:  6.10.1          
    Severity:  normal            |   Resolution:                  
    Keywords:                    |   Difficulty:  Unknown         
    Testcase:                    |           Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |  
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Comment (by int-e):

 Here's a more enlightening example:

 {{{
 import GHC.Conc

 main = do
     t <- atomically $ do
         alwaysSucceeds (return 42)
         return 23
     print t
 }}}

 This will print 42 instead of 23. I believe that if any invariants are
 checked, the result of {{{atomically}}} will be that of the last
 invariant.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3049#comment:3>
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