[Issue 1594] version not honored for invarient declaration

[John Mandeville]

d-bugmail at puremagic.com Wrote:

> I know its not intuitive but the compiler is behaving correctly. All the code
> inside a version block must be valid code for the compiler you are using.
> 
> Here is how you need to do what you want to achieve...
> 
> version(D_Version2)
> {
>         string str = "Version 2";
>         mixin("invariant int myint = 2;");
> }
> 
> else
> {
>         string str = "Version 1";
>         const int myint = 1;
> }

Hmmmm.  The following would also work:

version (D_Version2)
{
	mixin( "alias invariant int invarInt;" );
	invarInt myint = 2;
}

Unfortunately, this does not work:

version (D_Version2)
{
	mixin( "alias invariant int invarInt;" );
}
else
{
	alias const int invarInt;
}

Neither v.1 nor v. 2 likes alias of const.  (I can't figure out why neither likes alias of const but v. 2 likes alias of invariant.  const is a storage class, not a type modifier; but then, I  presume, the same is true for invariant in v. 2.)

Could an invariant storage class be added to version 1 that is just equivalent 10 const?  We obviously don't want to add a new storage class semantics to version 1--changes to v. 1 at this point should be limited essentially to bug fixes.  However, using the word invariant with const semantics might be a small enough change to be a worthwhile.  It would be a convenience to those trying to develop for version 1 and version 2 sinultaneously.