title: How MutexGuard was Sync When It Should Not Have Been
categories: rust research
reddit: /rust/comments/6gavfe/how_mutexguard_was_sync_when_it_should_not_have/
+license: CC BY-SA 4.0
+license-url: https://creativecommons.org/licenses/by-sa/4.0/
---
A couple of weeks ago, our ongoing effort to [formalize Rust's type system]({% post_url 2015-10-12-formalizing-rust %}) lead to us actually discovering a bug in the Rust standard library:
That said, such decisions are of course going to go through the usual RFC process.
It's certainly possible that someone comes up with a compromise that preserves some of the usefulness of auto traits, without putting safety at risk.
+#### Footnotes