If I understand correctly, Autopropagators are basically implicit parameters , a.k.a typed dynamic scoping, which is exactly what you need to solve this problem

If I understand correctly, Autopropagators are basically implicit parameters , a.k.a typed dynamic scoping, which is exactly what you need to solve this problem. In fact the equivalent Scala functionality is mentioned in the issue thread. They might be confusing but they are probably a million time better than actual mutable globals.