returnUs (env', vs2)
-- VERY IMPORTANT: we must zap the demand info
- -- if the thing is going to float out past a lambda
+ -- if the thing is going to float out past a lambda,
+ -- or if it's going to top level (where things can't be strict)
zap_demand dest_lvl ctxt_lvl id
- | ctxt_lvl == dest_lvl = id -- Stays put
- | otherwise = zapDemandIdInfo id -- Floats out
+ | ctxt_lvl == dest_lvl,
+ not (isTopLvl dest_lvl) = id -- Stays, and not going to top level
+ | otherwise = zapDemandIdInfo id -- Floats out
\end{code}