Post

Predrag Gruevski
@predr.ag

It's Tuesday, and so far so good! Two things happened today, by which I mean after midnight last night. First, I merged a PR to allow unstable stdlib items to be considered non-public-API. Similarly, const-unstable items are considered non-const in public API: github.com/obi1kenobi/t...

github.comAllow std library stability to influence what is public API. by obi1kenobi · Pull Request #1080 · obi1kenobi/trustfall-rustdoc-adapterIn preparation for allowing cargo-semver-checks to check the Rust standard library for accidental breakage, add a mode where stability affects what is considered public API. In that mode: unstable...
Predrag Gruevski
@predr.ag

Second, the last required upstream PR got merged into rustdoc! It lets us know which default values (like on associated consts, or default method impls in traits) are considered stable and therefore public API. This is the last "partial stability" mechanism we need. github.com/rust-lang/ru...

github.comInclude default-stability info in rustdoc JSON. by obi1kenobi · Pull Request #158468 · rust-lang/rustAdd a default_unstable field on associated constants, associated types, and functions. The field is populated only when those items appear inside a trait, only when there's a default present, a...
Predrag Gruevski
@predr.ag

It's Wednesday, day 3. Default-stability is in rustdoc JSON in today's nightly Rust. Only *stable* defaults are public API, so we pretend unstable values don't exist. I'm working on a PR for this, and also on type normalization improvements to let us have type-checking lints 👀

Predrag Gruevski
@predr.ag

I had to take a brief detour to triage a surprising new class of SemVer breakage. It's always *a time* when the net result is "8 issues across 5 repos" 😅 The net result is the same: even more lints! github.com/obi1kenobi/c...

github.comBreakage in items of reachable but not nameable supertrait · Issue #1658 · obi1kenobi/cargo-semver-checksExample minified from time-rs/time#793 mod sealed { pub trait Sealed { fn example(&self) { ... } } } pub trait Visible: sealed::Sealed {} Now modify: mod sealed { pub trait Sealed { - fn example(&s...
Predrag Gruevski
@predr.ag

It's Thursday, day 4. Today's haul so far is ~2500 LoC. First, making use of default-value stability which we previously exposed in rustdoc JSON. Codex caught a subtle edge case that affects which traits are considered sealed. Copious test cases are standard, of course. github.com/obi1kenobi/t...

github.comSupport default-value stability in rustdoc JSON v60. by obi1kenobi · Pull Request #1087 · obi1kenobi/trustfall-rustdoc-adapterUnstable default values, such as provided function bodies in trait definitions, associated type defaults, and default values for associated constants, are treated as not present when indexing rustd...

1 repost1 like

Predrag Gruevski
@predr.ag

Second, an improvement to how we normalize types. We'll need this to implement type-checking lints in the future. This will eliminate a large class of expensive type-checks where the previous logic was unnecessarily conservative and quite inefficient. github.com/obi1kenobi/t...

github.comNormalize parent, item, and higher-ranked generics separately. by obi1kenobi · Pull Request #1086 · obi1kenobi/trustfall-rustdoc-adapterPreviously, adding a generic param to a parent impl scope could cause the normalized generic params of functions in that impl to get renumbered, making it look like those functions' signatures ...
Predrag Gruevski
@predr.ag

Day 5, a picture worth a thousand words 👇 I put an API-breaking `#[doc(hidden)]` in my local build of the Rust standard library, and asked cargo-semver-checks to find it. See for yourself!

Predrag Gruevski
@predr.ag

Still some cleanup to do before this can merge, but I'm exhausted. I'm 30 PRs and 15080 cumulative lines in on my week off from work 😅 I'm calling this a win, and now going to lay down and read a book.