Godot - Change tiles within an area - godot

Question

I'm trying to make it so if a function is called an area covered by a Collisionshape2D gets its tiles removed in a TileMap node. My problem is the area deleted doesn't match the Collisionshape2D's. Any insight is appreciated! Thank you.
My code:
func changeArea(collionshape):
var corridorTile = $CorridorTiles
var rect = Rect2(collionshape.position, collionshape.shape.extents*2)
var topleft = corridorTile.world_to_map(rect.position)
var bottomright = corridorTile.world_to_map(rect.end)
for x in range(topleft.x, bottomright.x):
for y in range(topleft.y, bottomright.y):
corridorTile.set_cell(x, y, -1)
Edit1*
Upon changing the code to:
func changeCorridorTile(collionshape):
var corridorTile = $CorridorTiles
var extents:Vector2 = collionshape.shape.extents
var topleft = corridorTile.world_to_map(collionshape.position - extents)
var bottomright = corridorTile.world_to_map(collionshape.position + extents)
for x in range(topleft.x, bottomright.x):
for y in range(topleft.y, bottomright.y):
corridorTile.set_cell(x, y, -1)
corridorTile.update_bitmask_region()
The cells in the tileMap which the collisionShape2D area covers get deleted. And I update them using .bitmask_region() method.

Answer 1

First thing I notice, from the top of my head: The Rect2 position is a corner, but the CollisionShape position is the center.
You would have to do it like this:
var extents:Vector2 = collionshape.shape.extents
var rect := Rect2(collionshape.position - extents, extents * 2)
Now, on a second look, you don't need the Rect2 at all:
var extents:Vector2 = collionshape.shape.extents
var topleft = corridorTile.world_to_map(collionshape.position - extents)
var bottomright = corridorTile.world_to_map(collionshape.position + extents)
One more thing: I believe that is in local space of the parent of the CollisionShape2D (an Area2D, I guess). So, if that is not working, it might be because you need to do it in global space. Hopefully you don't have any rotation (which would just mess the whole thing up) or scaling, so that would only be a matter of using global_position.
Addendum: I forgot something, world_to_map does not take global coordinates. Try this instead (assuming no rotation or scaling):
var extents:Vector2 = collionshape.shape.extents
var position := corridorTile.to_local(collionshape.global_position)
var topleft = corridorTile.world_to_map(position - extents)
var bottomright = corridorTile.world_to_map(position + extents)