[stm] strange behavior with TQueue and STM's alternative instance

[Simon Marlow]

On 10/12/12 13:24, Bas van Dijk wrote:
> import Control.Concurrent.STM
> main = do
>    x <- atomically $ do
>           t <- newTVar 1
>           writeTVar t 2
>           ((writeTVar t 3 >> retry) `orElse` return ()) `orElse` return ()
>           readTVar t
>    print x

Yes, it gives the right answer now.  I don't think reading or writing in 
the inner transaction affects the bug, since that part is aborted before 
we get to the outer orElse, which is where the erroneous case was triggered.

Cheers,
	Simon