Many changes, including bug fixes and documentation improvements can be implemented and reviewed via the normal GitHub pull request workflow.
Some changes though are "substantial", and we ask that these be put through a bit of a design process and produce a consensus among the Rust community and the core team.
The "RFC" (request for comments process) is intended to provide a consistent and controlled path for new features to enter the language and standard libraries, so that all stakeholders can be confident about the direction the language is evolving in.
You need to follow this process if you intend to make "substantial" changes to the Rust distribution. What constitutes a "substantial" change is evolving based on community norms, but may include the following.
- Any semantic or syntactic change to the language that is not a bugfix.
- Changes to the interface between the compiler and libraries, including lang items and intrinsics.
- Additions to
std
Some changes do not require an RFC:
- Rephrasing, reorganizing, refactoring, or otherwise "changing shape does not change meaning".
- Additions that strictly improve objective, numerical quality criteria (warning removal, speedup, better platform coverage, more parallelism, trap more errors, etc.)
- Additions only likely to be noticed by other developers-of-rust, invisible to users-of-rust.
If you submit a pull request to implement a new feature without going through the RFC process, it may be closed with a polite request to submit an RFC first.
In short, to get a major feature added to Rust, one must first get the RFC merged into the RFC repo as a markdown file. At that point the RFC is 'active' and may be implemented with the goal of eventual inclusion into Rust.
- Fork the RFC repo http://github.com/rust-lang/rfcs
- Copy
0000-template.mdtoactive/0000-my-feature.md(where 'my-feature' is descriptive. don't assign an RFC number yet). - Fill in the RFC
- Submit a pull request. The pull request is the time to get review of the design from the larger community.
- Build consensus and integrate feedback. RFCs that have broad support are much more likely to make progress than those that don't receive any comments.
- Eventually, somebody on the core team will either accept the RFC by merging the pull request and assigning the RFC a number, at which point the RFC is 'active', or reject it by closing the pull request.
Once an RFC becomes active then authors may implement it and submit the feature as a pull request to the Rust repo. An 'active' is not a rubber stamp, and in particular still does not mean the feature will ultimately be merged; it does mean that in principle all the major stakeholders have agreed to the feature and are amenable to merging it.
Modifications to active RFC's can be done in followup PR's. An RFC that makes it through the entire process to implementation is considered 'complete' and is moved to the 'complete' folder; an RFC that fails after becoming active is 'inactive' and moves to the 'inactive' folder.
The process is intended to be as lightweight as reasonable for the present circumstances. As usual, we are trying to let the process be driven by consensus and community norms, not impose more structure than necessary.