Code using seq has wrong strictness (too lazy) when optimised
Following program prints
 instead of crashing when compiled with
-O -fno-full-laziness. Note that it's neccessary to use the extra definition
hiddenError instead of calling
error directly. The problem might be related to #5557 (closed), which, however, has already been fixed and optimisation is needed to trigger the current bug.
hiddenError = error "hidden error" main = do print $ seq (head (map (\a -> \b -> hiddenError) (hiddenError:: Bool))) id 
I used GHC 7.3.20111022 for triggering this problem.
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