Why would Move/Leak being tied to editions hurt compile times? Presumably old editions would have the required trait bounds added immediately after parsing, and

Why would Move/Leak being tied to editions hurt compile times? Presumably old editions would have the required trait bounds added immediately after parsing, and the existing trait machinery would handle that. You'd need extra checks for error messages so you can tell people using !Leak/!Move with old code why they have extra trait bounds, but that's about that.