$ cat rust-lang/week/2026-09-21.log
the week in review · Sep 21 – Sep 27, 2026
Polonius constraints speed up, RawVec drops Unique
By RepoJournal · composed from the cited sources · human-reviewed weekly · methodology
The week's work is compiler throughput and diagnostics: borrow-check traversal wins, a RawVec internals cleanup, and higher-level const generics.
A couple polonius constraints perf improvements rust-lang/rust
The polonius constraint changes land as conceptually independent of the lazy liveness work and show up in cases where traversal dominates. Reviewers asked for a perf run because the touched code is on the hot path, so expect numbers before you count on it in your own builds.
Auto merge of #162804 - maxdexh:nuke-unique-in-vec, r=hanna-kruppe rust-lang/rust
The auto-merged change strips `Unique` out of `RawVec`, following a t-libs discussion about whether the type is still pulling its weight. Because it touches allocation-adjacent code, a perf run was flagged as likely.
Rollup merge of #163138 - sorairolake:feature/more-duration-constants, r=clarfonthey rust-lang/rust
`Duration::{WEEK, DAY, HOUR, MINUTE}` are now associated constants, tracking issue rust-lang/rust#57391. Code that spelled out 86_400 or 604_800 in seconds can name the unit instead.
Reduce missing/corrupt SQLite archive-index errors caused by overlapping cache cleanup and repair rust-lang/docs.rs
docs.rs is cutting the overlapping cache cleanup and repair that produced regular "unable to open database file" errors and flaky tests. If you maintain a crate whose docs builds failed intermittently, this is the class of failure being addressed.
metrics: Remove legacy Prometheus metrics rust-lang/crates.io
OpenTelemetry now covers the server and worker metrics that Prometheus used to expose, so crates.io removes the private endpoint, its legacy instruments, the endpoint configuration, and the Prometheus dependency; the database snapshot path stays.
Use span context for enclosing item(s) of unmet bound rust-lang/rust
E0277 now points at the item that introduced an unmet bound, and at the surrounding trait or impl for associated items, without adding a span label. Fewer round trips when a generic bound is one level up from the error.
Add background job queue-age metrics rust-lang/crates.io
A new `crates_io.background_jobs.oldest_age` gauge reports seconds since the oldest outstanding job was enqueued, grouped by job type and priority, so background-job health thresholds live in Datadog rather than application code.
Rollup merge of #163207 - mejrs:hir_imports2, r=BoxyUwU rust-lang/rust
The rustc_hir import cleanup continues, with one more PR still to come and a matching clippy change, split up to keep each diff reviewable. Alongside: rustfmt bumped its toolchain to nightly-2026-09-21, miri runs more tests natively (which surfaced a segfault in its pthread_set/getname_np tests) and now rejects unsupported `FILE_FLAG_OPEN_REPARSE_POINT` uses, and the stable/nightly channel memb...
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