Design meeting: Open enums

[traviscross]

Summary

Let's discuss open enums.

• https://rust-lang.github.io/rust-project-goals/2026/open-enums.html
• RFC: Open up your enum with an unnamed variant rfcs#3894

cc @scottmcm @kupiakos

About this issue

This issue corresponds to a lang-team design meeting proposal. It corresponds to a possible topic of discussion that may be scheduled for deeper discussion during one of our design meetings.