Evolution通ってない実験的な機能だから削除したと言っているのかなと思いました。(だから誰かPR作ってEvolution通して欲しいということなのかと)

If the feature is merged but doesn’t seem to be making progress, it may be removed. For what it’s worth, that has happened to work by Apple engineers.

https://forums.swift.org/t/pitch-optionset-macro/63547/167 Embedded buildには残っているですかね？ https://github.com/apple/swift/pull/69197 (edited)

[Pitch] @OptionSet macro

It’s not reserved only for certain people. As code owners, we make a judgment call based on an informal assessment of the feature’s prospects and how much work it would take to maintain it as a branch for a few months. Sometimes the Language Working Group gets asked for their opinion on the first point. If the feature is merged but doesn’t seem...

[Embedded] Include OptionSet as part of the embedded build by phaus...

It seems OptionSet was elided from embedded builds. This corrects that and includes it within those builds.