Module Clarification

[Jonathan Marler via Digitalmars-d-learn]

On Thursday, 22 September 2016 at 20:09:41 UTC, Steven 
Schveighoffer wrote:
>
> Before package.d support, you could not do any importing of 
> packages. You could only import modules. package.d was how the 
> compiler allowed importing packages.
>
> I don't know that there is a fundamental difference between 
> foo/package.d and foo.d, but this is just the solution that was 
> chosen. Is it a mistake? I don't think so, it's just a 
> preference.
>
> Prior to this, it was common to put "package" imports into an 
> "all.d" file:
>
> foo/all.d // import fooPart1.d fooPart2.d
> foo/fooPart1.d
>
> -Steve

Ok, do you know why is this not allowed?

foo.d
foo/bar.d