Ghosting a language feature

[Avrina]

On Tuesday, 22 September 2020 at 03:19:43 UTC, Avrina wrote:
> On Monday, 21 September 2020 at 23:57:17 UTC, Walter Bright 
> wrote:
>> Once something is implemented, I don't see the advantage of 
>> delaying deployment of it, possibly for years, in order to 
>> meet some arbitrary milepost.
>
> A lot of c++ features get implemented before the spec is 
> finalized. You can use the features by specifying a specific 
> version. For anyone that wants bleeding edge they can access 
> the new features. Those new features tend to introduce 
> regressions and are buggy. The bugs that get ironed out early 
> on don't follow deprecation paths as the feature is still new 
> and isn't used that wildly, so breaking changes are let through 
> more easily in these cases. Discouraging investing in using the 
> feature even if it is "implemented".

That's to say if you want how D is developed now you'd just use 
-spec=d2.xy and it'll enable be at the bleeding edge. What'd this 
introduce is a way for people that want and need backwards 
co.patibility to have it.