version vs. static if

[Sean Kelly]

On Sep 23, 2011, at 3:30 PM, Nick Sabalausky wrote:
> 
> But version is *not* restricted to what's defined. It *also* deals with 
> what's *not* defined. That's the main problem I'm talking about.
> 
> If Walter wants to limit the logic operations and import implications, none 
> of that necessitates that the version identifiers be based on "defined vs 
> undefined".
> 
> What I mean is this: Using an undefined version identifier should be an 
> error:
> 
> version(ThisIsNeverDeclaredAnywhere) {} else {}
> 
> That is currently accepted, but it should be a compile-time error.

I'm not sure I understand.  If this were the case, how could we use version(Windows) etc in our code?