The rustc repo has a system to assign PRs to reviewers automatically upon filing. On github, PRs and issues are very similar, and one can assign people to them.

The rustc repo has a system to assign PRs to reviewers automatically upon filing. On github, PRs and issues are very similar, and one can assign people to them. There is a bot which checks which components the PR is modifying and based on that it assigns a reviewer to it. It predates github's builtin support for specifying component maintainers, so is a bit different than that. However, as the Rust project is mostly made up of volunteers, sometimes a PR gets assigned to someone who is less active. This happened in my instance, where the PR got assigned to a reviewer whose last approval that ended up in a merge was in February 2022. The PRs assigned to these maintainers still get reviewed eventually, by other reviewers, or maybe them themselves. The assignment is more of a suggestion than a strict requirement and often maintainers with a desire to review some PR assign themselves. I just wanted to speed up the process so I talked to a maintainer who I knew likes to go through the list of open PRs and approve them if they are trivial. That's what I mean by "fell through the cracks".