ports https://github.com/tgstation/tgstation/pull/19981

Special thanks to MrStonedOne.

code/__HELPERS/lists.dm

@@ -67,6 +67,14 @@
 		return 0
 	return L[A.type]
 
+//returns a new list with only atoms that are in typecache L
+/proc/typecache_filter_list(list/atoms, list/typecache)
+	. = list()
+	for (var/thing in atoms)
+		var/atom/A = thing
+		if (typecache[A.type])
+			. += A
+
 //Like typesof() or subtypesof(), but returns a typecache instead of a list
 /proc/typecacheof(path, ignore_root_path)
 	if(ispath(path))

code/__HELPERS/unsorted.dm

@@ -543,7 +543,7 @@ Turf and target are seperate in case you want to teleport some distance from a t
 				return 0
 			if(current.opacity)
 				return 0
-			for(var/atom/A in current)
+			for(var/thing in current)
 				if(A.opacity)
 					return 0
 			current = get_step_towards(current, target_turf)