Version of OpenTTD

20190603-master-g846fc8fe09

Expected result

Like rail infrastructure, road infrastructure counts should be updated properly when converting to different road types.

Actual result

When you convert road types, the game does not properly change the numbers on the infrastructure piece counts for road, unlike rail. This can lead to:

• You don't have any infrastructure built but are paying thousands in infrastructure maintenance per year
• You have some infrastructure built but are not paying anything towards infrastructure maintenance or even getting an idle net profit from infrastructure maintenance.
• Detailed infrastructure says that you have, for example, "Dirt Road: -100"

Note that all infrastructure counts are fixed on savegame load, so any server where one or more companies fell victim to this exploit just has to 1. save game, 2. load game, 3. reset affected bank balances (optional).

Steps to reproduce

1. Load any NewGRF providing extra road types (examples: Unspooled, Docklands, RattRoads).
2. Start new game, with infrastructure maintenance enabled.
   The following steps assume you have RattRoads loaded in your game.
3. Build some dirt roads.
4. Convert the dirt roads to highways.
5. Demolish the highways.
6. Repeat steps 3 through 5, but on a larger scale each time.
7. You should be getting lots of money despite having no infrastructure, no vehicles, and a nonnegative loan.

If you repeat steps 3 through 5 in reverse order, then you'll actually end up losing much more than the background loss rate of £300/yr (£25/mo) despite having nothing built, no vehicles, and no loan.