[Old bug] Tiles over buildings

Branch: Preview Branch

Version: Windows

Pending

This is an old bug that, to my knowledge, never got reported.

Someone already did a great video demonstrating it:

By replacing a tile with another tile of another material just before it's deconstructed, you can build another building inside.

Once re-built, tiles have a weird behavior, interacting with the world in some ways, but not in others:

from the sim perspective, they are seen as regular tiles
from Dupes perspective, they will go through if there is a door inside
from other buildings perspective, they exist for requirements (Wall Pot see them as a valid wall)
but it doesn't prevent buildings inside from working

A few examples:

There is a mechanized door set to "Open" just left of the printing pod. Dupes can go through, gases cannot.
The Bluff Briars are inside Wall pots.This is for demonstration, but the real value is to combine it with this exploit.
The Liquid Pump is tricked by the droplet of water and will pump the magma without transferring it with it at 10kg/s. This is by far easier than non-exploit methods to do that.
The Gas Pump is tricked to pump and will not exchange heat with the bottom left gases. Unfortunately, it's coded in a way that it requires line of sight to pump, and this exploit doesn't work there : it's actively pumping, but it doesn't output anything. Before reload, it was depleting the gas, after reload it doesn't anymore.

Here is the save with the already built contraptions:

Steps to Reproduce

Build a tile with any material except the desired one.
Deconstruct that tile.
Just after the progress bar disappear, but before the tile is removed, order the construction of a tile with the desired material at that place. The previous material will fall out and the new tile will be queued for construction.
It's now possible to build buildings inside that tile before it's fully built. Order the construction of a building there.
Let Dupes construct both the tile and the building in the same cell.