D1 -> D2

[%u]

== Quote from Denis Koroskin (2korden at gmail.com)'s article
> On Thu, 18 Nov 2010 22:19:12 +0300, Walter Bright
> <newshound2 at digitalmars.com> wrote:
> > Steven Schveighoffer wrote:
> >> My recommendation -- when you are ready, switch wholly to D2.  Don't
> >> bother with compatibility, it's just not possible.
> >
> >  From what you wrote, it appears that most of the difficulties were in
> > dealing with strings.
> No, it's not. From my experience, a bigger issue is that
> version (D2) {
>     /* some D2 only code involving const etc */
> }
> simply won't compile in D1, because even if it's D2-only the code needs to
> be correct D1 code as well.

Wow, that sucks!!
Can't this simply be mended with special D_DMD1 and D_DMD2 (D_DMD3 :) version
identifiers?
If the compiler version isn't the same then it won't look at the code.