While this is nice, there are some long requested features like Discriminated Unions that got delayed a lot.

Metasyntactic 4 days ago | parent | next [-]

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.

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DeathArrow 4 days ago | parent [-]

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.

	▲	Metasyntactic 4 days ago \| parent [-]
		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!

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SideburnsOfDoom 5 days ago | parent | prev [-]

Discriminated unions are a hard feature to put into a mature language that already has other features in a similar space - I mean enums and class hierarchies. (.e.g. if your union is "Cat or Dog", then in OO terms they have a common base class "Animal" ). How does it play with records, structs, generics, etc etc.

That is why although they are much requested, none of the proposals that I have seen are simple to understand or easy to implement, and thus are proceeding slowly.

I don't really see Discriminated union as being in "competition" with "a?.b = c" as that's a "quick win" extension to previous ?. and ?? syntax. It's not even close to being of the same magnitude.

I would settle for a good built-in Result<T, E> type, so that people don't roll their own crappy ones, or use various opinionated but incompatible libraries.