Robert Clipsham Wrote:
> I recently came across this:
>
> version( BackendFoo ) {}
> else version( BackendBar ) {}
> else version( BackendCar ) {}
> else
> {
> pragma( msg, "Warning: backend version undefined" );
> pragma( msg, "Attempting to guess backend" );
> version( Windows )
> {
> version = BackendFoo;
> pragma( msg, "Selected the Foo backend." );
> }
> else version(...)
> { /* You get the idea */ }
> }
>
> However, when trying to compile I get the following error:
>
> Error: version BackendFoo defined after use
>
> What is the reasoning behind this? It could be extremely useful to have
> this functionality. The only reason I can think of for doing this is
> that this code could be evaluated after modules that depend on the
> version being defined, causing it not to work. Surely there would be a
> way around that?
>
> If it's not possible to fix this, what way would you recommend I get
> around this? The only idea I've come up with so far is to do:
>
> else
> {
> static assert( false, "Please compile with
> -version=Backend(Foo|Bar|Bar)" );
> }
>
> Which is less than optimal.
I wonder if a compiler patch to loosen the restrictions would be accepted.
Something like what you tried should be trivial to support.
