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const_eval: allow function pointer signatures containing &mut T in const contexts #116015

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merged 2 commits into from
Oct 14, 2023

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EvanMerlock
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@EvanMerlock EvanMerlock commented Sep 21, 2023

potentially fixes #114994

We utilize a TypeVisitor here in order to more easily handle control flow.

  • In the event the typekind the Visitor sees is a function pointer, we skip over it
  • However, otherwise we do one of two things:
    • If we find a mutable reference, check it, then continue visiting types
    • If we find any other type, continue visiting types

This means we will check if the function pointer itself is mutable, but not if any of the types within are.

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rustbot commented Sep 21, 2023

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @cjgillot (or someone else) soon.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

  • @rustbot author: the review is finished, PR author should check the comments and take action accordingly
  • @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 21, 2023
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cc @oli-obk as it touches const-fn checks.

- uses TypeReader for resolving local/return ty to support case where function pointer is before another type in a compound type
- add new testcase for TypeVisitor on const-eval mutable ref check
@oli-obk oli-obk added T-lang Relevant to the language team, which will review and decide on the PR/issue. I-lang-nominated Nominated for discussion during a lang team meeting. and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 25, 2023
@oli-obk oli-obk marked this pull request as ready for review September 25, 2023 14:55
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oli-obk commented Sep 25, 2023

Nominating for T-lang FCP as this enables more code to compile. Specifically this allows mutable references in const fn, as long as they are part of a function pointer signature. We already support function pointers on stable (but not calling them), and we forbid all mutable references. This check was overzealous and also forbade function pointers that had mutable references as arguments, even though there is no risk associated with that at all, as function pointers can't be used at compile-time anyway (except to pass them around).

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tmandry commented Oct 3, 2023

@rfcbot fcp merge

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rfcbot commented Oct 3, 2023

Team member @tmandry has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Oct 3, 2023
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@oli-obk I'm fine with this PR, but it'd be nice to have examples of other places where &mut is disallowed (and why) so that we can see that those cases don't apply here.

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@rfcbot reviewed

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@nikomatsakis: See #57349 for the remaining blockers for &mut in const, there seems to be some outstanding issue with statics (de)duplication.

@rfcbot rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Oct 3, 2023
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rfcbot commented Oct 3, 2023

🔔 This is now entering its final comment period, as per the review above. 🔔

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RalfJung commented Oct 3, 2023

Cc @rust-lang/wg-const-eval

@tmandry tmandry removed the I-lang-nominated Nominated for discussion during a lang team meeting. label Oct 10, 2023
@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Oct 13, 2023
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rfcbot commented Oct 13, 2023

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

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oli-obk commented Oct 13, 2023

@bors r+

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bors commented Oct 13, 2023

📌 Commit d975ae5 has been approved by oli-obk

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 13, 2023
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bors commented Oct 14, 2023

⌛ Testing commit d975ae5 with merge 2104b0d...

bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 14, 2023
const_eval: allow function pointer signatures containing &mut T in const contexts

potentially fixes rust-lang#114994

We utilize a `TypeVisitor` here in order to more easily handle control flow.
- In the event the typekind the Visitor sees is a function pointer, we skip over it
- However, otherwise we do one of two things:
   - If we find a mutable reference, check it, then continue visiting types
   - If we find any other type, continue visiting types

This means we will check if the function pointer _itself_ is mutable, but not if any of the types _within_ are.
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The job x86_64-msvc-ext failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)
tests\ui-toml\undocumented_unsafe_blocks\undocumented_unsafe_blocks.rs (default) ... ok
tests\ui-toml\undocumented_unsafe_blocks\undocumented_unsafe_blocks.rs (disabled) ... ok

tests\ui-toml\doc_valid_idents_append\doc_markdown.rs FAILED:
command: "C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\clippy-driver.exe" "--error-format=json" "--emit=metadata" "-Aunused" "-Ainternal_features" "-Zui-testing" "-Dwarnings" "-Ldependency=C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps" "--extern=clippy_lints=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libclippy_lints-5e8d785e054edb28.rlib" "--extern=clippy_utils=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libclippy_utils-0cf228b0c1780fd5.rlib" "--extern=futures=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libfutures-a074388a1bf2e009.rlib" "--extern=if_chain=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libif_chain-ba0253edeba7a8f0.rlib" "--extern=itertools=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libitertools-6894b4f3e8c5523f.rlib" "--extern=parking_lot=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libparking_lot-f87e1900e520ff9b.rlib" "--extern=quote=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libquote-3ebce4a1d5d43cf1.rlib" "--extern=regex=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libregex-3e46ad2dfdd0c657.rlib" "--extern=serde=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libserde-12500b7f802b2beb.rlib" "--extern=serde_derive=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\release\\deps\\serde_derive-67ed154847593e2b.dll" "--extern=syn=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libsyn-bc3ce53f417d339c.rlib" "--extern=tokio=\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\x86_64-pc-windows-msvc\\release\\deps\\libtokio-159ee9fbda356223.rlib" "-Ldependency=C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\release\\deps" "--out-dir" "\\\\?\\C:\\a\\rust\\rust\\build\\x86_64-pc-windows-msvc\\stage2-tools\\ui_test" "tests\\ui-toml\\doc_valid_idents_append\\doc_markdown.fixed" "--edition" "2021" "--crate-name" "doc_markdown"
called `Result::unwrap()` on an `Err` value: tests failed

Location:
    C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\ui_test-0.20.0\src\lib.rs:362:13
    C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\ui_test-0.20.0\src\lib.rs:362:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: test failed, to rerun pass `--test compile-test`

rustfix failed with exit code: 1

full stderr:
error: failed to write \\?\C:\a\rust\rust\build\x86_64-pc-windows-msvc\stage2-tools\ui_test\libdoc_markdown.rmeta: Access is denied. (os error 5)
error: aborting due to previous error


full stdout:

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bors commented Oct 14, 2023

💔 Test failed - checks-actions

@bors bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Oct 14, 2023
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oli-obk commented Oct 14, 2023

@bors retry

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 14, 2023
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bors commented Oct 14, 2023

⌛ Testing commit d975ae5 with merge 139f63a...

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bors commented Oct 14, 2023

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 139f63a to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 14, 2023
@bors bors merged commit 139f63a into rust-lang:master Oct 14, 2023
12 checks passed
@rustbot rustbot added this to the 1.75.0 milestone Oct 14, 2023
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Finished benchmarking commit (139f63a): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
0.9% [0.9%, 0.9%] 1
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) - - 0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
1.3% [1.3%, 1.3%] 1
Regressions ❌
(secondary)
1.6% [1.3%, 2.1%] 3
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) 1.3% [1.3%, 1.3%] 1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
1.3% [1.3%, 1.3%] 1
Regressions ❌
(secondary)
- - 0
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) 1.3% [1.3%, 1.3%] 1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 627.527s -> 628.233s (0.11%)
Artifact size: 271.26 MiB -> 271.32 MiB (0.03%)

bors-ferrocene bot added a commit to ferrocene/ferrocene that referenced this pull request Oct 17, 2023
54: Pull upstream master 2023 10 17 r=pietroalbini a=Veykril

* rust-lang/rust#116196
* rust-lang/rust#116824
* rust-lang/rust#116822
* rust-lang/rust#116477
* rust-lang/rust#116826
* rust-lang/rust#116820
  * rust-lang/rust#116811
  * rust-lang/rust#116808
  * rust-lang/rust#116805
  * rust-lang/rust#116800
  * rust-lang/rust#116798
  * rust-lang/rust#116754
* rust-lang/rust#114370
* rust-lang/rust#116804
  * rust-lang/rust#116802
  * rust-lang/rust#116790
  * rust-lang/rust#116786
  * rust-lang/rust#116709
  * rust-lang/rust#116430
  * rust-lang/rust#116257
  * rust-lang/rust#114157
* rust-lang/rust#116731
* rust-lang/rust#116550
* rust-lang/rust#114330
* rust-lang/rust#116724
* rust-lang/rust#116782
  * rust-lang/rust#116776
  * rust-lang/rust#115955
  * rust-lang/rust#115196
* rust-lang/rust#116775
* rust-lang/rust#114589
* rust-lang/rust#113747
* rust-lang/rust#116772
  * rust-lang/rust#116771
  * rust-lang/rust#116760
  * rust-lang/rust#116755
  * rust-lang/rust#116732
  * rust-lang/rust#116522
  * rust-lang/rust#116341
  * rust-lang/rust#116172
* rust-lang/rust#110604
* rust-lang/rust#110729
* rust-lang/rust#116527
* rust-lang/rust#116688
* rust-lang/rust#116757
  * rust-lang/rust#116753
  * rust-lang/rust#116748
  * rust-lang/rust#116741
  * rust-lang/rust#116594
* rust-lang/rust#116691
* rust-lang/rust#116643
* rust-lang/rust#116683
* rust-lang/rust#116635
* rust-lang/rust#115515
* rust-lang/rust#116742
  * rust-lang/rust#116661
  * rust-lang/rust#116576
  * rust-lang/rust#116540
* rust-lang/rust#116352
* rust-lang/rust#116737
  * rust-lang/rust#116730
  * rust-lang/rust#116723
  * rust-lang/rust#116715
  * rust-lang/rust#116603
  * rust-lang/rust#116591
  * rust-lang/rust#115439
* rust-lang/rust#116264
* rust-lang/rust#116727
  * rust-lang/rust#116704
  * rust-lang/rust#116696
  * rust-lang/rust#116695
  * rust-lang/rust#116644
  * rust-lang/rust#116630
* rust-lang/rust#116728
  * rust-lang/rust#116689
  * rust-lang/rust#116679
  * rust-lang/rust#116618
  * rust-lang/rust#116577
  * rust-lang/rust#115653
* rust-lang/rust#116702
* rust-lang/rust#116015
* rust-lang/rust#115822
* rust-lang/rust#116407
* rust-lang/rust#115719
* rust-lang/rust#115524
* rust-lang/rust#116705
* rust-lang/rust#116645
* rust-lang/rust#116233
* rust-lang/rust#115108
* rust-lang/rust#116670
* rust-lang/rust#116676
* rust-lang/rust#116666



Co-authored-by: Benoît du Garreau <bdgdlm@outlook.com>
Co-authored-by: Colin Finck <colin@reactos.org>
Co-authored-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Co-authored-by: Joshua Liebow-Feeser <joshlf@users.noreply.github.com>
Co-authored-by: León Orell Valerian Liehr <me@fmease.dev>
Co-authored-by: Trevor Gross <tmgross@umich.edu>
Co-authored-by: Evan Merlock <evan@merlock.dev>
Co-authored-by: joboet <jonasboettiger@icloud.com>
Co-authored-by: Ralf Jung <post@ralfj.de>
Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
Co-authored-by: Mark Rousskov <mark.simulacrum@gmail.com>
Co-authored-by: onur-ozkan <work@onurozkan.dev>
Co-authored-by: Nicholas Nethercote <n.nethercote@gmail.com>
Co-authored-by: The 8472 <git@infinite-source.de>
Co-authored-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Co-authored-by: reez12g <reez12g@gmail.com>
Co-authored-by: Jakub Beránek <berykubik@gmail.com>
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Oct 19, 2023
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Mar 3, 2024
Pkgsrc changes:
 * Adjust patches and cargo checksums to new versions.
 * For an external LLVM, set dependency of llvm >= 16, in accordance
   with the upstream changes.
 * Mark that on NetBSD we now need >= 9.0, so 8.x is no longer supported.
 * On NetBSD/sparc64 10.x, we now need GCC 12 to build the embedded
   LLVM, which is version 17; apparently GCC 10.4 or 10.5 mis-compiles it,
   resulting in an illegal instruction fault during the build.
   Ref. rust-lang/rust#117231

Upstream changes:

Version 1.75.0 (2023-12-28)
==========================

- [Stabilize `async fn` and return-position `impl Trait` in traits.]
  (rust-lang/rust#115822)
- [Allow function pointer signatures containing `&mut T` in `const` contexts.]
  (rust-lang/rust#116015)
- [Match `usize`/`isize` exhaustively with half-open ranges.]
  (rust-lang/rust#116692)
- [Guarantee that `char` has the same size and alignment as `u32`.]
  (rust-lang/rust#116894)
- [Document that the null pointer has the 0 address.]
  (rust-lang/rust#116988)
- [Allow partially moved values in `match`.]
  (rust-lang/rust#103208)
- [Add notes about non-compliant FP behavior on 32bit x86 targets.]
  (rust-lang/rust#113053)
- [Stabilize ratified RISC-V target features.]
  (rust-lang/rust#116485)

Compiler
--------

- [Rework negative coherence to properly consider impls that only
  partly overlap.] (rust-lang/rust#112875)
- [Bump `COINDUCTIVE_OVERLAP_IN_COHERENCE` to deny, and warn in dependencies.]
  (rust-lang/rust#116493)
- [Consider alias bounds when computing liveness in NLL.]
  (rust-lang/rust#116733)
- [Add the V (vector) extension to the `riscv64-linux-android` target spec.]
  (rust-lang/rust#116618)
- [Automatically enable cross-crate inlining for small functions]
  (rust-lang/rust#116505)
- Add several new tier 3 targets:
    - [`csky-unknown-linux-gnuabiv2hf`]
      (rust-lang/rust#117049)
    - [`i586-unknown-netbsd`]
      (rust-lang/rust#117170)
    - [`mipsel-unknown-netbsd`]
      (rust-lang/rust#117356)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Override `Waker::clone_from` to avoid cloning `Waker`s unnecessarily.]
  (rust-lang/rust#96979)
- [Implement `BufRead` for `VecDeque<u8>`.]
  (rust-lang/rust#110604)
- [Implement `FusedIterator` for `DecodeUtf16` when the inner iterator does.]
  (rust-lang/rust#110729)
- [Implement `Not, Bit{And,Or}{,Assign}` for IP addresses.]
  (rust-lang/rust#113747)
- [Implement `Default` for `ExitCode`.]
  (rust-lang/rust#114589)
- [Guarantee representation of None in NPO]
  (rust-lang/rust#115333)
- [Document when atomic loads are guaranteed read-only.]
  (rust-lang/rust#115577)
- [Broaden the consequences of recursive TLS initialization.]
  (rust-lang/rust#116172)
- [Windows: Support sub-millisecond sleep.]
  (rust-lang/rust#116461)
- [Fix generic bound of `str::SplitInclusive`'s `DoubleEndedIterator` impl]
  (rust-lang/rust#100806)
- [Fix exit status / wait status on non-Unix `cfg(unix)` platforms.]
  (rust-lang/rust#115108)

Stabilized APIs
---------------

- [`Atomic*::from_ptr`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.from_ptr)
- [`FileTimes`]
  (https://doc.rust-lang.org/stable/std/fs/struct.FileTimes.html)
- [`FileTimesExt`]
  (https://doc.rust-lang.org/stable/std/os/windows/fs/trait.FileTimesExt.html)
- [`File::set_modified`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_modified)
- [`File::set_times`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_times)
- [`IpAddr::to_canonical`]
  (https://doc.rust-lang.org/stable/core/net/enum.IpAddr.html#method.to_canonical)
- [`Ipv6Addr::to_canonical`]
  (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_canonical)
- [`Option::as_slice`]
  (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_slice)
- [`Option::as_mut_slice`]
  (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_mut_slice)
- [`pointer::byte_add`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_add)
- [`pointer::byte_offset`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset)
- [`pointer::byte_offset_from`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset_from)
- [`pointer::byte_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_sub)
- [`pointer::wrapping_byte_add`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_add)
- [`pointer::wrapping_byte_offset`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_offset)
- [`pointer::wrapping_byte_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_sub)

These APIs are now stable in const contexts:

- [`Ipv6Addr::to_ipv4_mapped`]
  (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_ipv4_mapped)
- [`MaybeUninit::assume_init_read`]
  (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_read)
- [`MaybeUninit::zeroed`]
  (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.zeroed)
- [`mem::discriminant`]
  (https://doc.rust-lang.org/stable/core/mem/fn.discriminant.html)
- [`mem::zeroed`]
  (https://doc.rust-lang.org/stable/core/mem/fn.zeroed.html)

Cargo
-----

- [Add new packages to `[workspace.members]` automatically.]
  (rust-lang/cargo#12779)
- [Allow version-less `Cargo.toml` manifests.]
  (rust-lang/cargo#12786)
- [Make browser links out of HTML file paths.]
  (rust-lang/cargo#12889)

Rustdoc
-------

- [Accept less invalid Rust in rustdoc.]
  (rust-lang/rust#117450)
- [Document lack of object safety on affected traits.]
  (rust-lang/rust#113241)
- [Hide `#[repr(transparent)]` if it isn't part of the public ABI.]
  (rust-lang/rust#115439)
- [Show enum discriminant if it is a C-like variant.]
  (rust-lang/rust#116142)

Compatibility Notes
-------------------

- [FreeBSD targets now require at least version 12.]
  (rust-lang/rust#114521)
- [Formally demote tier 2 MIPS targets to tier 3.]
  (rust-lang/rust#115238)
- [Make misalignment a hard error in `const` contexts.]
  (rust-lang/rust#115524)
- [Fix detecting references to packed unsized fields.]
  (rust-lang/rust#115583)
- [Remove support for compiler plugins.]
  (rust-lang/rust#116412)
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Function pointer signature containing &mut T should work in const context