Error when using `import`.

[Liam McGillivray]

There's something that I'm trying to do that D may or may not be 
capable of.

In the Map class, there is a 2-dimensional array called `grid`, 
where the Tile objects are stored. The Mission class inherits the 
Map class.

In the Mission class, I want the `grid` array to instead be 
composed of a derivative of the Tile class. I tried making a 
derived class called `GridTile` which contains the additional 
property specific to the Raylib front-end.

I tried doing this, but it won't let me override `grid`, even if 
I change it from `private` to `protected` in the Map class.

Is there a way I can do this, without this additional 
functionality being put in the base Tile class?