Update language feature status doc.

[333fred]

@jaredpar @jcouv for review. I'm optimistically assuming that #54724 will be merged before this is. I'm also not 100% certain that all the lambda features are in, but certainly a portion of them are? LMK if you think I should break them out into what's been implemented or if this is good.

[jcouv]

"Static Abstract Members In Interfaces" should stay under C# Next.
The optimistic moving of other features makes sense. Thanks

[333fred]

"Static Abstract Members In Interfaces" should stay under C# Next.

I considered this, but I specifically renamed it to "Preview" and put it under 10 because my assumption is that, once we start implementing any feedback from the preview, we'll want to have another feature branch and it will be good to have a separate listing maintaining when the initial preview shipped.

[jcouv]

I'd agree with moving it if the sections were Roslyn versions. But we're using C# versions and this feature it's not part of C# 10. We're recording when things shipped with the status column ("Merged into ").
If we need to track new feature branches (not just bug fixes), it's easy to add new rows as needed.

[333fred]

I'd agree with moving it if the sections were Roslyn versions. But we're using C# versions and this feature it's not part of C# 10.

The preview is part of the C# 10 release cycle. As I said, we use this document to keep track of when things are released. This was released, in preview, as part of the C# 10 release cycle. Next year, when we release for real, we'll have a separate section for C# 11 that includes the non-preview version of this feature, and we will still want to know when the preview was merged.

[jcouv]

As I said, we use this document to keep track of when things are released.

This feature was not released. That's the point of contention.
Just like all preview features, it exists in the codebase, is merged into a certain version of VS, etc. Until it is released, it should not be attached to a language version, either in code (RequiredVersion) or in docs.

we will still want to know when the preview was merged.

Yes and that is tracked by the Status column already.

[333fred]

Yes and that is tracked by the Status column already.

Where would you propose that we put this feature when C# 11 comes out? Again, remember that there will be two rows: one for the initial preview, one for the final version.

[jcouv]

I'm not convinced that we're going to have a second iteration on this feature. My expectation is that we'll add three small satellite features, but likely leave the main feature alone.

But assuming we do need two waves, we'll have the choice of having two links in Status column ("wave 1 merged in dev17p2, wave 2 in progress") or using two rows. Either is fine with me.
Once the feature is released in C# 11, we just move the row (or rows) into C# 11 section.