Re:The biggest threat to Rust's sustainability
by steveklabnik on Saturday March 20, 2021 @03:54PM
(#26525667)
Nobody promised full formal specifications before landing features. The pin soundness issue was found close to release, but a plan was made to fix it before it was released. Pin is not fundamentally unsound.
People do want it, and in fact, it is part of async, and directly related to the soundness issues you’re complaint about. The reason such things aren’t in stable is that, while people do want it, people wanted async more, and did the work. The work has to happen, features don’t just magically come into existence.
The way I see unprincipled is two fold: 1) You're breaking your promise 2) In a similar situation behave differently
1) Pin was a problem from the start. Allowing it into std/core was a mistake. The fact they allowed an almost blatantly unsound feature is unprincipled.
I'm not 100% sure of the timeline, but near or before the release there were examples floating of a possible Pin unsoundness. And defense was, it's an obscure thing, no one would really use that in practice. The moment designer says, no one would use that in practice, is the moment they lost.
2) Yeah, I get async was a feature everyone wanted. By same measure, why not add self-referential struct. People want it. It's probably unsound but you can't tell. Maybe there exist a model that allows self-referntial structs.
Similar situation, different behavior