Assigning to class struct member leading to unexpected behavior.

[Paul]

I'm experiencing a compile error, but for the life of me, I 
cannot figure out what is wrong.

I'll try to keep it short but the code is roughly as follows:
> class Window{
>    Screen screen;
>    alias screen this;
>
>     this() {
>         Screen s = {bottom_f: {[0, 1]}};
>         this.screen = s; // Works
>         this.screen = {bottom_f: {[0, 1]}}; // Leads to the 
> list of errors below
>     }
>     ...
> }

> struct Screen{
>     Vec!(2, int) bottom_f;
>     ...
> }

> alias Vec(uint size, Type) = Mat!(size, 1, Type);
>
> struct Mat(uint rows, uint columns = rows, Type = float) {
>     private enum uint size = rows * columns;
>     union{
>         Type[columns][rows] mat;
>         Type[size] vec;
>     }
>     static if (columns == 1) alias vec this;
>     else alias mat this;
>     . . .
> }


List of errors:
1. "Label "bottom_f" is not used."
2. "expected ; instead of }"
3. "found `}` when expecting `;` following statement"
4. "use `{ }` for an empty statement, not `;`"
5. "found `void` when expecting `;` following statement" (later 
at function below constructor)

Why would assigning to a member variable lead to errors when 
using an intermediate variable of the same type does not?
I tried tweaking a lot but I just can't figure it out. Am I doing 
something wrong?