> What I was proposing was that common subsequences of enum fields be treated by the compiler as synonyms, but accesses to uninitialized data would still be illegal. One way this might be implemented is by, when necessary, creating additional tags behind the scenes, e.g. MyEnum::__AB__ meaning A was initialized but B is the active member, so only accesses to their common subsequence are legal, MyEnum::__BA__ meaning the reverse, and so forth. Or it could be restricted to fields that contain no members outside their common subsequence with nontrivial destructors. Or the compiler could null out any uninitialized references to such.

I feel like that's too much hidden behind-the-scenes magic for a systems language, and I suspect the majority of the Rust community would feel the same way, but feel free to file an RFC.

> Interesting. Link?

https://github.com/rust-lang/rfcs/issues/349