+ -- In practice it always will have a strictness
+ -- signature, even if it's a uninformative one
+ strict_sig = newStrictnessInfo fn_info `orElse` topSig
+ StrictSig (DmdType env wrap_dmds res_info) = strict_sig
+
+ -- fn_id' has the DmdEnv zapped.
+ -- (a) it is never used again
+ -- (b) it wastes space
+ -- (c) it becomes incorrect as things are cloned, because
+ -- we don't push the substitution into it
+ fn_id' | isEmptyVarEnv env = fn_id
+ | otherwise = fn_id `setIdNewStrictness`
+ StrictSig (mkTopDmdType wrap_dmds res_info)