Why does file order matters when using -run option?

[Seb]

On Wednesday, 14 March 2018 at 14:44:24 UTC, Marc wrote:
> assume the files:
>
> app.d
>
>> void main() {
>>   import myModule : foo;
>>    writeln(foo(...));
>>
>> }
>
> myModule.d
>
> module myModule;
>> int foo(int n) { .... }
>
> the following fail:
>
>> dmd -run app.d mymodule.d
>
> give error like this:
>
>> Error: module `myModule` is in file 'myModule.d' which cannot 
>> be read
>
> but this doesn't fail:
>
>> dmd app.d mymodule.d && app
>
> Why does -run fail here? I thought it was a shorthand to this 
> batch:
>
>> dmd app.d mymodule.d
>> app.exe
>> del app.exe

Not even that dmd mymodule.d -run app.d works and dmd -i -run 
app.d works too.

However, at the moment -run needs to be the last parameter. 
That's a more or less arbitrary restriction.
And no one has lifted it (yet).
Though there's a bit of work on that front:

https://github.com/dlang/dmd/pull/7927

The main problem is that the arguments after -run module are 
passed to the program and thus -run can be ambiguous.