util.set: Change '/' operator from filter to map+filter (nil to drop from set, false is a valid item). No code found which depends on current behaviour.

1 files changed, 3 insertions, 2 deletions

diff --git a/util/set.lua b/util/set.lua
index 050446ec..7f45526e 100644
--- a/util/set.lua
+++ b/util/set.lua
@@ -26,8 +26,9 @@ function set_mt.__div(set, func)
 	local new_set, new_items = _M.new();
 	local items, new_items = set._items, new_set._items;
 	for item in pairs(items) do
-		if func(item) then
-			new_items[item] = true;
+		local new_item = func(item);
+		if new_item ~= nil then
+			new_items[new_item] = true;
 		end
 	end
 	return new_set;