When is_action_possible() determines target extra for CLEAN_POLLUTION or CLEAN_FALLOUT by prev_extra_in_tile() some of the later checks are redundant (should be done only for caller-provided extras); we already know that the extra is on tile, and that it's removed by the action.
When is_action_possible() determines target extra for CLEAN_POLLUTION or CLEAN_FALLOUT by prev_extra_in_tile() some of the later checks are redundant (should be done only for caller-provided extras); we already know that the extra is on tile, and that it's removed by the action.