Is this a bug?

[Elfstone]

On Thursday, 16 March 2023 at 03:44:19 UTC, Elfstone wrote:
> On Thursday, 16 March 2023 at 03:40:04 UTC, Elfstone wrote:
>> [...]
>
> Oops, the above code compiles, because I added comments!!!
>
> Now this really doesn't compile:
>
> ```D
> struct Matrix(S, size_t M, size_t N)
> {
> }
>
> alias Vec3(S) = Matrix!(S, 3, 1);
>
> void main()
> {
>     import std.stdio;
>
>     writeln(is(Vec3!float == Matrix!(S, 3, 1), S));
>     writeln(is(Matrix!(float, 3, 1) == Matrix!(S, 3, 1), S));
> }
> ```

Correction.

With or without comments, mostly it doesn't compile, occasionally 
it does!
I have no idea.