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‎_posts/2024-12-02-2024-11-monthly-report.md‎

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---
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layout: post
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title: "November 2024 Monthly report"
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author: Philip Herron, Pierre-Emmanuel Patry and Arthur Cohen
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tags:
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- monthly-report
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---
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## Overview
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Thanks again to [Open Source Security, inc](https://opensrcsec.com/) and
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[Embecosm](https://www.embecosm.com/) for their ongoing support for this
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project.
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### Project update
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GCC development entered stage 3 this month, meaning that `gccrs` is no
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longer allowed to submit patches that affect the entire GCC framewrok
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until the project re-enters stage 1, after the release of GCC 15.1. This
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is not an issue for us, as we took special care to send the affected
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patches upstream back in June of this year, giving them plenty of time
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to get reviewed and merged before stage 3. In other GCC news, the
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baseline for building the compiler got bumped from GCC 4.8 to GCC 5.4 -
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this means that the oldest compiler that we are expected to target is
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newer and adds support for C++14. Thanks to [Sam
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James](https://github.com/thesamesam) and [Marc
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Poulhiès](https://github.com/dkm), we have updated our CI to reflect
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this change. Thank you both!
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Most of the pull-requests this month were focused on name resolution,
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with even more improvements made by [Owen
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Avery](https://github.com/powerboat9). Owen has been a contributor to
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the project for two years, and has been extremely helpful recently with
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our name resolution rewrite (NR2.0), by working on integrating it to all
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areas of the compiler. We will thus be welcoming Owen to the core
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`gccrs` team of contributors.
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An interesting technical change this month concerns the type-checking of
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`match` expressions. In one certain case, `match` expressions can
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resolve to the `never` type. This is interesting for empty \~enum\~s,
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which can be used to represent invalid or impossible states. A well
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known type from the standard library is
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[Infallible](https://doc.rust-lang.org/std/convert/enum.Infallible.html),
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whose definition is as follows:
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``` rust
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enum Infallible {}
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```
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Since this `enum` does not contain any variants, matching on it looks a
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bit strange:
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``` rust
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fn handle_infallible(x: Infallible) {
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let y = match x {};
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}
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```
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In that case, what should the type of `y` be? Since we cannot extract
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any information from `x`, it doesn't really make sense to give `y` a
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regular type. Furthermore, since we cannot instantiate a value of type
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`Infallible` in the first place, it does not make sense to do
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pattern-matching on it to extract information! But by making this
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pattern matching resolve to the `never` type, we can implement traits on
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`Infallible` in order to use it just like a regular error type - since
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`never` can always coerce to any target type, as it cannot exist in the
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first place. This makes empty pattern matching required for handling the
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`Infallible` type and its trait implementations, which is required for
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handling code that can never fail. The documentation of the `enum` gives
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an interesting example, in which the `TryFrom<T>` trait can be
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implemented for `U` when `U` already implements `From<T>`. Because we
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know the conversion can never fail, there is no need to expose a proper
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error type, as those errors will never show up.
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The fix for this is quite simple - if the `match` we are type-checking
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is empty, then we can just resolve its type to `never`. If the match is
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not supposed to be empty (for example, if we are matching on an `enum`
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with one or more variants), then it's up to the exhaustiveness checker
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to report an issue - not the type-checker!
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If you are curious, you can see how this special case is handled in
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[gccrs](https://github.com/Rust-GCC/gccrs/blob/afbd87358cc8b4627536145510b0c17634005eb6/gcc/rust/typecheck/rust-hir-type-check-expr.cc#L1461-L1468)
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and in
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[rustc](https://github.com/rust-lang/rust/blob/3d1dba830a564d1118361345d7ada47a05241f45/compiler/rustc_hir_typeck/src/_match.rs#L32-L36).
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In other technical news, [Antoni Boucher](https://github.com/antoyo),
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lead developer of the `rustc_codegen_gcc` project, contributed code to
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`gccrs` this month in order to improve target feature detection for both
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of our projects. This code concerns platform-specific information that
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the compilers needs to know about in order to produce correct assembly.
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By reusing the same code in both projects, we ensure that Rust code
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compiled using one of the GCC-based compilers will behave the same way
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on the users' machines. This change also makes it easier to adapt our
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target configuration values for Rust if the need arises. Thank you
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Antoni!
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Finally, a blogpost written in collaboration with the Rust project was
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also published on the official Rust blog:
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<https://blog.rust-lang.org/2024/11/07/gccrs-an-alternative-compiler-for-rust.html>.
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This blogpost outlines some of the decisions we've made for `gccrs` to
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make sure that the project does not threaten the Rust ecosystem and does
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not risk splitting it in two. The main discussion thread about it can be
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found [here on
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Reddit](https://www.reddit.com/r/rust/comments/1gm51ki/gccrs_an_alternative_compiler_for_rust_rust_blog/),
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where it was really well-received.
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### Community call
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We will have our next monthly community call on the 9th of December at
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10am UTC. You can subscribe to our calendar to see when the next one
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will be held. The call is open to everyone, even if you would just like
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to sit-in and listen. You can also subscribe to our
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[mailing-list](https://gcc.gnu.org/mailman/listinfo/gcc-rust) or join
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our [Zulip chat](https://gcc-rust.zulipchat.com) to be notified of
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upcoming events.
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- [Jitsi link](https://meet.jit.si/gccrs-community-call-december)
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- Calendar ID:
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7060a0923ffebd3cb52b1afef35a28ff7b64f05962c9af84c23b1847f1f5f894@group.calendar.google.com
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- [Google calendar
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link](https://calendar.google.com/calendar/embed?src=7060a0923ffebd3cb52b1afef35a28ff7b64f05962c9af84c23b1847f1f5f894%40group.calendar.google.com)
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- [iCal
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link](https://calendar.google.com/calendar/ical/7060a0923ffebd3cb52b1afef35a28ff7b64f05962c9af84c23b1847f1f5f894%40group.calendar.google.com/public/basic.ics)
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## Call for contribution
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There are no calls for contribution this month, as we do not have a lot
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of good first issues available. Still, feel free to take a look at them
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[here](https://github.com/Rust-GCC/gccrs/issues?q=is%3Aopen+is%3Aissue+label%3Agood-first-pr)
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and get in touch with us for some mentoring or help!
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## Completed Activities
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- hir: Remove duplicate function in TraitItemFunc
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[PR3276](https://github.com/rust-gcc/gccrs/pull/3276)
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- Cleanup lang items mappings
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[PR3273](https://github.com/rust-gcc/gccrs/pull/3273)
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- gccrs: ensure packed and aligned is applied properly
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[PR3272](https://github.com/rust-gcc/gccrs/pull/3272)
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- gccrs: allow casts from numeric types to floats
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[PR3270](https://github.com/rust-gcc/gccrs/pull/3270)
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- gccrs: improve handling of Self Type paths
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[PR3269](https://github.com/rust-gcc/gccrs/pull/3269)
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- ci: bump actions/checkout version and fix gcc 5 testing
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[PR3268](https://github.com/rust-gcc/gccrs/pull/3268)
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- gccrs: fix crash in hir dump with missing guards
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[PR3267](https://github.com/rust-gcc/gccrs/pull/3267)
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- Prepend crate name to functions with nr2
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[PR3265](https://github.com/rust-gcc/gccrs/pull/3265)
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- ci: remove bors mention
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[PR3263](https://github.com/rust-gcc/gccrs/pull/3263)
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- CI: upgrade GCC baseline from 4.8 -\> 5.4 (5.5)
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[PR3262](https://github.com/rust-gcc/gccrs/pull/3262)
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- Clean up some system includes
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[PR3259](https://github.com/rust-gcc/gccrs/pull/3259)
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- Prevent execution of some nr1.0 functions with nr2.0
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[PR3257](https://github.com/rust-gcc/gccrs/pull/3257)
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- gccrs: empty match expressions should resolve to !
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[PR3256](https://github.com/rust-gcc/gccrs/pull/3256)
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- Add a new CI step to detect raw issue references in commit messages
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[PR3255](https://github.com/rust-gcc/gccrs/pull/3255)
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- Handle type path segments during late resolution 2.0
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[PR3254](https://github.com/rust-gcc/gccrs/pull/3254)
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- Use nr2.0 in typechecker
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[PR3253](https://github.com/rust-gcc/gccrs/pull/3253)
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- Use nr2.0 in \`PrivacyReporter\`
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[PR3252](https://github.com/rust-gcc/gccrs/pull/3252)
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- gccrs: Fix bad handling for recursive type query
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[PR3250](https://github.com/rust-gcc/gccrs/pull/3250)
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- Push ribs by kind rather than by value
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[PR3249](https://github.com/rust-gcc/gccrs/pull/3249)
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- Improve handling of static items in toplevel 2.0
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[PR3248](https://github.com/rust-gcc/gccrs/pull/3248)
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- Cleanup clang warnings
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[PR3244](https://github.com/rust-gcc/gccrs/pull/3244)
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- gccrs: add test case to show issue is fixed
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[PR3243](https://github.com/rust-gcc/gccrs/pull/3243)
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- Fix bad type checking on fn trait calls
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[PR3240](https://github.com/rust-gcc/gccrs/pull/3240)
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- Use name resolver 2.0 in \`VisibilityResolver\`
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[PR3239](https://github.com/rust-gcc/gccrs/pull/3239)
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- Improve handling of implicit \`Self\` parameter in AST
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[PR3238](https://github.com/rust-gcc/gccrs/pull/3238)
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- gccrs: fix bad type inference on local patterns
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[PR3237](https://github.com/rust-gcc/gccrs/pull/3237)
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- Improve handling of struct expressions in nr2.0
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[PR3225](https://github.com/rust-gcc/gccrs/pull/3225)
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- Use name resolver 2.0 for module descendance checks
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[PR3224](https://github.com/rust-gcc/gccrs/pull/3224)
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- Reorganize the CPU feature detection
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[PR3195](https://github.com/rust-gcc/gccrs/pull/3195)
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- Add build dependencies for Fedora
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[PR3154](https://github.com/rust-gcc/gccrs/pull/3154)
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- Reduce the amount of raw pointer the HIR API
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[PR2878](https://github.com/rust-gcc/gccrs/pull/2878)
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### Contributors this month
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- [Antoni Boucher](https://github.com/antoyo) (new contributor!)
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- [Sam James](https://github.com/thesamesam) (new contributor!)
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- [Jarkko Sakkinen](https://github.com/jarkkojs) (new contributor!)
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- [Philip Herron](https://github.com/philberty)
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- [Pierre-Emmanuel Patry](https://github.com/P-E-P)
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- [Arthur Cohen](https://github.com/CohenArthur)
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- [Owen Avery](https://github.com/powerboat9)
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- [Marc Poulhiès](https://github.com/dkm)
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- [Thomas Schwinge](https://github.com/tschwinge)
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### Overall Task Status
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| Category | Last Month | This Month | Delta |
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|-------------|------------|------------|-------|
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| TODO | 327 | 316 | -11 |
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| In Progress | 75 | 80 | +5 |
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| Completed | 897 | 907 | +10 |
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### Test Cases
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| TestCases | Last Month | This Month | Delta |
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|-----------|------------|------------|-------|
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| Passing | 9212 | 9266 | +54 |
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| Failed | \- | \- | \- |
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| XFAIL | 294 | 264 | -30 |
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| XPASS | \- | \- | \- |
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### Bugs
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| Category | Last Month | This Month | Delta |
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|-------------|------------|------------|-------|
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| TODO | 119 | 112 | -7 |
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| In Progress | 48 | 40 | -8 |
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| Completed | 441 | 450 | +9 |
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### Milestones Progress
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| Milestone | Last Month | This Month | Delta | Start Date | Completion Date | Target | Target GCC |
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|----------------------------|------------|------------|-------|---------------|-----------------|---------------|------------|
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| Name resolution 2.0 rework | 6% | 20% | +14% | 1st Jun 2024 | \- | 1st Apr 2025 | GCC 15.1 |
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| Macro expansion | 29% | 29% | \- | 1st Jun 2024 | \- | 1st Jan 2025 | GCC 15.1 |
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| Lang items | 66% | 90% | +24% | 1st Jul 2024 | \- | 21st Nov 2024 | GCC 15.1 |
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| Indexing fixes | 0% | 0% | \- | 21st Jul 2024 | \- | 15th Nov 2024 | GCC 15.1 |
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| Iterator fixes | 0% | 0% | \- | 21st Jul 2024 | \- | 15th Nov 2024 | GCC 15.1 |
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| Auto traits improvements | 0% | 0% | \- | 15th Sep 2024 | \- | 21st Dec 2024 | GCC 15.1 |
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| Remaining typecheck issues | 85% | 88% | +3% | 21st Oct 2024 | \- | 1st Mar 2025 | GCC 15.1 |
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| cfg-core | 0% | 0% | \- | 1st Dec 2024 | \- | 1st Mar 2025 | GCC 15.1 |
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| Codegen fixes | 0% | 0% | \- | 7th Oct 2024 | \- | 1st Mar 2025 | GCC 15.1 |
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| Upcoming Milestone | Last Month | This Month | Delta | Start Date | Completion Date | Target | Target GCC |
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|--------------------------------------|------------|------------|-------|---------------|-----------------|---------------|------------|
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| Question mark operator | 0% | 0% | \- | 15th Dec 2024 | \- | 21st Feb 2025 | GCC 15.1 |
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| Specialization | 0% | 0% | \- | 1st Jan 2025 | \- | 1st Mar 2025 | GCC 15.1 |
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| Inline assembly | 100% | 100% | \- | 1st Jun 2024 | 26th Aug 2024 | 15th Sep 2024 | GCC 15.1 |
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| Borrow checker improvements | 100% | 100% | \- | 1st Jun 2024 | 26th Aug 2024 | 15th Sep 2024 | GCC 15.1 |
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| Rustc Testsuite Adaptor | 0% | 0% | \- | 1st Jun 2024 | \- | 15th Sep 2024 | GCC 15.1 |
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| black<sub>box</sub> intrinsic | 0% | 0% | \- | 28th Oct 2024 | \- | 28th Jan 2025 | GCC 15.1 |
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| Unstable RfL features | 0% | 0% | \- | 7th Jan 2025 | \- | 1st Mar 2025 | GCC 15.1 |
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| cfg-rfl | 0% | 0% | \- | 7th Jan 2025 | \- | 15th Feb 2025 | GCC 15.1 |
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| alloc parser issues | 100% | 100% | \- | 7th Jan 2025 | 31st Jun 2024 | 28th Jan 2025 | GCC 15.1 |
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| let-else | 0% | 0% | \- | 28th Jan 2025 | \- | 28th Feb 2025 | GCC 15.1 |
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| Explicit generics with impl Trait | 0% | 0% | \- | 28th Feb 2025 | \- | 28th Mar 2025 | GCC 15.1 |
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| Downgrade to Rust 1.49 | 0% | 0% | \- | \- | \- | 1st Apr 2025 | GCC 15.1 |
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| offset<sub>of</sub>!() builtin macro | 0% | 0% | \- | 15th Mar 2025 | \- | 15th May 2025 | GCC 15.1 |
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| Generic Associated Types | 0% | 0% | \- | 15th Mar 2025 | \- | 15th Jun 2025 | GCC 16.1 |
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| RfL const generics | 0% | 0% | \- | 1st May 2025 | \- | 15th Jun 2025 | GCC 16.1 |
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| frontend plugin hooks | 0% | 0% | \- | 15th May 2025 | \- | 7th Jul 2025 | GCC 16.1 |
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| Handling the testsuite issues | 0% | 0% | \- | 15th Sep 2024 | \- | 15th Sep 2025 | GCC 16.1 |
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| std parser issues | 100% | 100% | \- | 7th Jan 2025 | 31st Jun 2024 | 28th Jan 2025 | GCC 16.1 |
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| main shim | 0% | 0% | \- | 28th Jul 2025 | \- | 15th Sep 2025 | GCC 16.1 |
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| Past Milestone | Last Month | This Month | Delta | Start Date | Completion Date | Target | Target GCC |
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|-----------------------------------|------------|------------|-------|---------------|-----------------|---------------|------------|
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| Data Structures 1 - Core | 100% | 100% | \- | 30th Nov 2020 | 27th Jan 2021 | 29th Jan 2021 | GCC 14.1 |
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| Control Flow 1 - Core | 100% | 100% | \- | 28th Jan 2021 | 10th Feb 2021 | 26th Feb 2021 | GCC 14.1 |
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| Data Structures 2 - Generics | 100% | 100% | \- | 11th Feb 2021 | 14th May 2021 | 28th May 2021 | GCC 14.1 |
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| Data Structures 3 - Traits | 100% | 100% | \- | 20th May 2021 | 17th Sep 2021 | 27th Aug 2021 | GCC 14.1 |
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| Control Flow 2 - Pattern Matching | 100% | 100% | \- | 20th Sep 2021 | 9th Dec 2021 | 29th Nov 2021 | GCC 14.1 |
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| Macros and cfg expansion | 100% | 100% | \- | 1st Dec 2021 | 31st Mar 2022 | 28th Mar 2022 | GCC 14.1 |
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| Imports and Visibility | 100% | 100% | \- | 29th Mar 2022 | 13th Jul 2022 | 27th May 2022 | GCC 14.1 |
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| Const Generics | 100% | 100% | \- | 30th May 2022 | 10th Oct 2022 | 17th Oct 2022 | GCC 14.1 |
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| Initial upstream patches | 100% | 100% | \- | 10th Oct 2022 | 13th Nov 2022 | 13th Nov 2022 | GCC 14.1 |
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| Upstream initial patchset | 100% | 100% | \- | 13th Nov 2022 | 13th Dec 2022 | 19th Dec 2022 | GCC 14.1 |
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| Update GCC's master branch | 100% | 100% | \- | 1st Jan 2023 | 21st Feb 2023 | 3rd Mar 2023 | GCC 14.1 |
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| Final set of upstream patches | 100% | 100% | \- | 16th Nov 2022 | 1st May 2023 | 30th Apr 2023 | GCC 14.1 |
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| Borrow Checking 1 | 100% | 100% | \- | TBD | 8th Jan 2024 | 15th Aug 2023 | GCC 14.1 |
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| Procedural Macros 1 | 100% | 100% | \- | 13th Apr 2023 | 6th Aug 2023 | 6th Aug 2023 | GCC 14.1 |
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| GCC 13.2 Release | 100% | 100% | \- | 13th Apr 2023 | 22nd Jul 2023 | 15th Jul 2023 | GCC 14.1 |
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| GCC 14 Stage 3 | 100% | 100% | \- | 1st Sep 2023 | 20th Sep 2023 | 1st Nov 2023 | GCC 14.1 |
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| GCC 14.1 Release | 100% | 100% | \- | 2nd Jan 2024 | 2nd Jun 2024 | 15th Apr 2024 | GCC 14.1 |
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| format<sub>args</sub>!() support | 100% | 100% | \- | 15th Feb 2024 | \- | 1st Apr 2024 | GCC 14.1 |
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| GCC 14.2 | 100% | 100% | \- | 7th Jun 2024 | 15th Jun 2024 | 15th Jun 2024 | GCC 14.2 |
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| GCC 15.1 | 100% | 100% | \- | 21st Jun 2024 | 31st Jun 2024 | 1st Jul 2024 | GCC 15.1 |
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| Unhandled attributes | 100% | 100% | \- | 1st Jul 2024 | 15th Aug 2024 | 15th Aug 2024 | GCC 15.1 |
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| Deref and DerefMut improvements | 100% | 100% | \- | 28th Sep 2024 | 25th Oct 2024 | 28th Dec 2024 | GCC 15.1 |
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## Planned Activities
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- Finish usage of lang items for codegen
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- Finish for-loops code expansion
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- Improve our process for updating our github repository with upstream
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GCC
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### Risks
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There have been no changes to the Risk table this month
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| Risk | Impact (1-3) | Likelihood (0-10) | Risk (I \* L) | Mitigation |
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|----------------------------------------|--------------|-------------------|---------------|-----------------------------------------------------------------|
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| Missing features for GCC 15.1 deadline | 2 | 1 | 2 | Start working on required features as early as July (6mo ahead) |
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## Detailed changelog

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