Permitted locations of a version condition

[Stewart Gordon]

Phil Deets wrote:
> Hello, I looked over the language specification, and I could not 
> find any statement which says where version conditions are 
> permitted.

Language syntax is generally left to the BNF blocks dotted around the 
documentation.

> I assumed that they would be permitted most places that #if would 
> be reasonable in C, but evidently that is not true as they do not 
> work within enumerations. 

That's because D's versioning system isn't a preprocessor.

> I would definitely like the following code to work.
> 
> enum Tag
> {
>    A, B, C,
>    version (5) {
>       D, E,
>    }
>    version (7) {
>       F, G,
>    }
>    // ...
> }

So would I, except that it makes more sense to me to have the trailing 
comma after the '}'.  Commas separate, unlike semicolons, which terminate.

> Added enumerated values based on versions seems like something that 
> would be desirable. I ran into this need when converting a header file 
> to D.
> 
> Does anyone know where version conditions are and are not allowed 
> currently?

They're allowed wherever the grammar expects either a statement or a 
declaration.

> Would version conditions within enumerations be a good feature to add to 
> D2?
<snip>

Yes.

Stewart.