Yes, editions are a great mechanism. It still has its limits, especially if you want easy edition migrations. All existing Rust code assumes it can drop any type whenever it wants, and that is not something you can just change across editions. You have to be very careful with defaults if you don't want conflicts when crossing edition boundaries.

The naïve idea would be to just say that all generic parameters have an implicit `where T: Move` bound, and you have to explicitly opt out of it with `where T: ?Move`, just like with `?Sized`.

In fact, that's exactly how I would expect it to work, but there may be non-obvious drawbacks.