Finding that a lot of really useful Rust features are very thinly documented. `Arc::make_mut()` is an *incredibly* powerful feature that is barely discussed. I only discovered it as a passing mention in the `Cow` docs. Just this one method has shaved literally hundreds of lines off the code I'm writing…
Worse still, the `Arc` introductory notes actually go out of their way to warn that you can't obtain a mutable reference, and point users at `Mutex`, without mentioning this copy-on-write feature!
#rustlang
And `Mutex` is a phenomenal ball-ache. Trying to push simple iterators through `Ref` nodes consumed most of the hundreds of lines of code I just deleted…
#rustlang