Waypoint Station Pathfinding Restrictions: Self-Defying

I saw the pathfinding restrictions in the waypoint stations today. They've been there a while, and I seem to remember I was the one that requested them in the first place. So I thought I'd test them out, and they work- though perhaps a little too well:

The restriction is doing precisely what it made to do: The train that is assigned to stop at that waypoint is not allowed to approach it. (The other empty waypoint there is configured identically; 3 holding waypoints, but only 2 trains on that line). The selected train is offscreen to the right somewhere, not the one sitting at the third waypoint, but it looks the same.

This feels like it should be an illegal configuration for the waypoint station.

Update 4.2 | v0.8.6c (b612).

Reproduction:

1. Have a train.
2. Have a waypoint.
3. Have the train on a line that explicitly uses that waypoint. Haven't tested with Network waiting bays, but it might work the same.
4. Configure the waypoint restrictions to deny the very line (or network) that is explicitly using it. This is the part that I feel ought to be impossible.
5. Make sure the train has nowhere else to go, so it's forced to go there. The effect is largely invisible otherwise (it will simply pick the alternatives, if they're not occupied by other trains).
6. Watch the pathfinding restriction function as designed!

If I assume it works the same on Network waiting bays, these restrictions seem like an excellent way to sort waiting bays by cargo type- as I've done on previous worlds- but using a single network, rather than three separate specific-cargo-type networks. Undoubtedly makes that kind of arrangement much easier to build and maintain.

I will note this also seems like it should be illegal... and has the same effect as above: Trains of the specified line are denied permission to approach.

The "Allow" side is a whitelist, right?

Interestingly, this time I tested on a waypoint that had a train parked at it- and that train did not respond to the addition of the restriction. That seems appropriate to me, since it's already there, and doesn't have anywhere else to go.

Yes, right now you can input contradictory things, and they will fail (or not) in interesting ways. We could do some work to make it a bit more foolproof (eg. ban waypoints on a line if the waypoint bans the line). For the most part I expect people to realise they've made a mistake and fix it themselves!