Hi there. C# lang designer here :)
Discriminated unions continue to be worked on, and you can see our latest designs here: https://github.com/dotnet/csharplang/blob/main/proposals/uni...
The space there is large and complex, and we have a large amount of resources devoted to it. There was no way that `a?.b = c` was going to change if/when unions come to the language.
For unions, nothing has actually been delayed. We continue working hard on it, and we'll release it when we think it's suitable and ready for the future of the lang.
The only feature that actually did get delayed was 'dictionary expressions' (one that i'm working). But that will hopefully be in C# 15 to fill out the collection-expression space.
Thank you for working on it, I hope we will see it in a release soon.
By delayed I mean that the committee was discussing about discriminated unions since a long time ago and it was never "the right time". You can see the discussions related to implementing discriminated unions on Github.
Hard problems take time :)
They also often need a lot of scaffolding to be built along the way. We like breaking hard problems into much smaller, composable, units that we can build into the language and then compose to a final full solution. We've been doing that for many years, with unions being a major goal we've been leading to. At this point, we think we have the right pieces in place to naturally add this in a way that feels right to the C# ecosystem.
Thanks for the feedback!