Has Rust actually settled down on some stability?
1. serde, the best serialization/deserialization library. This works on stable now using the `serge_codegen` crate and a custom `build.rs` script. This will Just Work on stable with no extra setup once Macros 1.1 lands, theoretically in about 5 weeks. But I'm using it on stable now in a half-dozen projects, thanks to a `build.rs` script.
2. Diesel, the high-level ORM library for Rust. This works on stable using a `build.rs` script, and 90% of it will work on stable without the `build.rs` script once Macros 1.1 ships.
There are a few other experimental libraries like Rocket (which looks very slick) that only work on nightly Rust. But I don't think any of them are particularly popular yet.
Personally, I maintain something like two dozen Rust crates and applications, and only two use nightly Rust. Both need Macros 1.1, which should be on stable in about 5 weeks.
To recap, in Rust, to make additions to the language:
1. Small additions mean make a PR.
2. Big additions mean make an RFC, then a PR if accepted.
3. These PRs go behind a feature flag that lets us track the feature, and only allows it on nightly.
4. People who desire the new feature try it out. (This is what you refer to.)
5. If any issues are found, they're fixed, or, in the worst case, the feature is removed.
6. The feature is made available to stable users, the feature flag is removed, and backwards incompatible changes can no longer happen.
What would be un-healthy is if everyone had to rely on nightly for everything. At the moment, most people use stable Rust. And of the people that use nightly, the largest single feature will be stable as of the next stable release for Rust. But some people are always going to be using nightly features, and that's a good thing: it means that by the time it hits stable, it's already undergone some degree of vetting.
How many breaking changes happened in the past 18 months?
