Code using seq has wrong strictness (too lazy) when optimised

Following program prints [1] 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 [1]

I used GHC 7.3.20111022 for triggering this problem.

Trac metadata

Trac field	Value
Version	7.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	michal.palka@poczta.fm
Operating system
Architecture