Dlang equivalent of #define/#ifdef : not... version

[Dukc]

On Tuesday, 20 April 2021 at 23:58:46 UTC, Steven Schveighoffer 
wrote:
> static if(i_am_a_feature) {
>    ...
> }
This would be correct if `i_am_a_feature` would be always 
defined, just set to `false` if not existent. But I think the 
idea was to not define the symbol at all if feature does not 
exists. In that case, the condition should be `static 
if(is(typeof(i_am_a_feature)))`.