Discriminated unions coming to C# (type unions)

[StefanBertels]

Seems that after a long discussion DU might arrive in C#:

https://github.com/dotnet/csharplang/blob/main/proposals/TypeUnions.md

They want to introduce Option and Result (~Either/Fin). But: "no monadic behaviour" (for now). Hmm.

Could/Should lang-ext make use of those types union feature? Naming conflicts?

What do you think?

[louthy]

If they add Option to System then I'll remove it from lang-ext and then extend it to have the same interface.

The biggest issue will be inability to use the traits.

Although, I'm hoping that the new extension-types feature (which will come before sum-types) will enable ad-hoc traits. If that's the case then the transition should be quite smooth.