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Stabilize some MaybeUninit behavior as const #90896

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merged 2 commits into from
Nov 28, 2021

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@jhpratt jhpratt commented Nov 14, 2021

This stabilizes the MaybeUninit::as_ptr, MaybeUninit::assume_init, and MaybeUninit::assume_init_ref as const fn. MaybeUninit::as_mut_ptr has been moved to a new flag: const_maybe_uninit_as_mut_ptr, which is blocked on #57349. MaybeUninit::slice_assume_init_ref can be const fn when the method is stabilized in general.

The relevant intrinsic has been stabilized as const as well, though this isn't user-visible. Due to the seemingly unrelated feature name I performed rg const_assert_type and found no other instances of it being used.

r? @oli-obk

@rustbot label: +A-const-fn +S-waiting-on-review +T-libs-api

@rustbot rustbot added A-const-fn S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Nov 14, 2021
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oli-obk commented Nov 14, 2021

Seems like we never added a test for these. Please make sure they are tested in a const context with some reasonablish use case (can we perform examples from the docs in const contexts now?)

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jhpratt commented Nov 16, 2021

My personal use case for field-by-field initialization of a struct. This would have to be done in a single method for a test, as mut refs aren't yet const stable.

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oli-obk commented Nov 16, 2021

My personal use case for field-by-field initialization of a struct. This would have to be done in a single method for a test, as mut refs aren't yet const stable.

tests can use unstable features, it seems ok to me to use const mut refs for such a test

@joshtriplett joshtriplett added I-libs-api-nominated Nominated for discussion during a libs-api team meeting. and removed I-nominated labels Nov 16, 2021
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jhpratt commented Nov 17, 2021

I knew that; I wasn't sure because you alluded to having a doctest. I'll add a regular UI test momentarily.

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oli-obk commented Nov 17, 2021

I knew that; I wasn't sure because you alluded to having a doctest. I'll add a regular UI test momentarily.

Ah sorry. I meant whether the doc examples contain something that we could copy into a test and make const. But your example is a great test, too, so let's roll with that

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oli-obk commented Nov 17, 2021

r? rust-lang/libs-api

cc @rust-lang/wg-const-eval

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jhpratt commented Nov 17, 2021

Ah gotcha. Either way works 🤷🏽

@@ -115,7 +114,7 @@
#![feature(const_intrinsic_copy)]
#![feature(const_intrinsic_forget)]
#![feature(const_likely)]
#![feature(const_maybe_uninit_as_ptr)]
#![feature(const_maybe_uninit_as_mut_ptr)]
#![feature(const_maybe_uninit_assume_init)]
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Can this be removed now?

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No, as the method takes a mutable parameter. const_mut_refs hasn't yet been stabilized.

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This is for assume_init, which is being stabilized... is it not? I am confused.

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Whoops, when I responded I thought misread where the code was. I'll check the necessity of this.

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Removing this results in the following errors:

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/mem/maybe_uninit.rs:915:19
    |
915 |             &mut *self.as_mut_ptr()
    |                   ^^^^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/ptr/mod.rs:374:32
    |
374 |         copy_nonoverlapping(x, tmp.as_mut_ptr(), 1);
    |                                ^^^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/ptr/mod.rs:485:17
    |
485 |         let t = t.as_mut_ptr() as *mut u8;
    |                 ^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/ptr/mod.rs:511:17
    |
511 |         let t = t.as_mut_ptr() as *mut u8;
    |                 ^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/ptr/mod.rs:701:34
    |
701 |         copy_nonoverlapping(src, tmp.as_mut_ptr(), 1);
    |                                  ^^^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: `maybe_uninit::MaybeUninit::<T>::as_mut_ptr` is not yet stable as a const fn
   --> library/core/src/ptr/mod.rs:793:47
    |
793 |         copy_nonoverlapping(src as *const u8, tmp.as_mut_ptr() as *mut u8, mem::size_of::<T>());
    |                                               ^^^^^^^^^^^^^^^^
    |
    = help: add `#![feature(const_maybe_uninit_as_mut_ptr)]` to the crate attributes to enable

error: could not compile `core` due to 6 previous errors

As such I'll be leaving the attribute in.

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I was asking about the const_maybe_uninit_assume_init, not the const_maybe_uninit_as_mut_ptr. (Note the line this comment is attached to.)

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Yeah, that probably should have been explicitly stated 🙂 I'll check when I'm on my laptop and send a follow-up if necessary.

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Thanks. :)

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Removing that line results in an error on line 496 of the same file (inside MaybeUninit::write). That's for the assume_init_mut method.

So...I think this means that const stability isn't currently subject to the same checks, in that a feature can be both simultaneously stable and unstable? If that's the case we should fix that.

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Ah I see, makes sense. I opened an issue for this: #91357

@m-ou-se m-ou-se removed the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Nov 17, 2021
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m-ou-se commented Nov 17, 2021

@rfcbot merge

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dtolnay commented Nov 17, 2021

@rust-lang/libs-api
@rfcbot fcp merge

This stabilizes const for the following already stable signatures:

impl<T> MaybeUninit<T> {
    pub const fn as_ptr(&self) -> *const T;
    pub const unsafe fn assume_init(self) -> T;
    pub const unsafe fn assume_init_ref(&self) -> &T;
}

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Amanieu commented Nov 17, 2021

What about assume_init_mut? Is there any reason not to const-stabilize it as well?

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dtolnay commented Nov 17, 2021

You can't have &mut in a const fn signature on stable.

error[E0658]: mutable references are not allowed in constant functions
 --> src/lib.rs:1:12
  |
1 | const fn f(_: &mut u8) {}
  |            ^
  |
  = note: see issue #57349 <https://github.com/rust-lang/rust/issues/57349> for more information

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rfcbot commented Nov 17, 2021

Team member @dtolnay 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!

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. final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Nov 17, 2021
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rfcbot commented Nov 18, 2021

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

@rfcbot rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Nov 18, 2021
@rfcbot rfcbot added the finished-final-comment-period The final comment period is finished for this PR / Issue. label Nov 28, 2021
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jhpratt commented Nov 28, 2021

Bumped stabilization to 1.59 and moved to a unit test. The other review comment I marked resolved as the feature gate is necessary (see my response for the error).

@rustbot label: -S-waiting-on-author +S-waiting-on-review

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 28, 2021
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oli-obk commented Nov 28, 2021

@bors r+ rollup

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bors commented Nov 28, 2021

📌 Commit 44b5b83 has been approved by oli-obk

@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 Nov 28, 2021
bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 28, 2021
…askrgr

Rollup of 3 pull requests

Successful merges:

 - rust-lang#90896 (Stabilize some `MaybeUninit` behavior as const)
 - rust-lang#91254 (Only check for errors in predicate when skipping impl assembly)
 - rust-lang#91303 (Miri: fix alignment check in array initialization)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit af0cf34 into rust-lang:master Nov 28, 2021
@rustbot rustbot added this to the 1.59.0 milestone Nov 28, 2021
@jhpratt jhpratt deleted the stabilize_const_maybe_uninit branch November 29, 2021 06:32
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Nov 29, 2021
CTFE: support assert_zero_valid and assert_uninit_valid

This ensures the implementation of all three type-based assert_ intrinsics remains consistent in Miri.

`assert_inhabited` recently got stabilized in rust-lang#90896 (meaning stable `const fn` can call it), so do the same with these other intrinsics.

Cc `@rust-lang/wg-const-eval`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Nov 30, 2021
CTFE: support assert_zero_valid and assert_uninit_valid

This ensures the implementation of all three type-based assert_ intrinsics remains consistent in Miri.

`assert_inhabited` recently got stabilized in rust-lang#90896 (meaning stable `const fn` can call it), so do the same with these other intrinsics.

Cc ``@rust-lang/wg-const-eval``
JohnTitor added a commit to JohnTitor/rust that referenced this pull request Nov 30, 2021
CTFE: support assert_zero_valid and assert_uninit_valid

This ensures the implementation of all three type-based assert_ intrinsics remains consistent in Miri.

`assert_inhabited` recently got stabilized in rust-lang#90896 (meaning stable `const fn` can call it), so do the same with these other intrinsics.

Cc ```@rust-lang/wg-const-eval```
@jplatte jplatte mentioned this pull request Dec 2, 2021
65 tasks
yvt added a commit to r3-os/r3 that referenced this pull request Dec 3, 2021
`const_maybe_uninit_as_ptr` has been stabilized by
<rust-lang/rust#90896>.
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Dec 9, 2021
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Jan 13, 2022
Update RELEASES for 1.58.

From what I can tell:

* `NonZero{unsigned}::is_power_of_two` was stabilized in 1.59: rust-lang#91301
* `MaybeUninit` const was added in 1.59: rust-lang#90896
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Jan 13, 2022
Update RELEASES for 1.58.

From what I can tell:

* `NonZero{unsigned}::is_power_of_two` was stabilized in 1.59: rust-lang#91301
* `MaybeUninit` const was added in 1.59: rust-lang#90896
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Jan 22, 2022
Pkgsrc changes:
 * Bump available bootstraps to 1.57.0.
 * For some reason, the vendor/libc checksums don't need fixing.
 * Bump required external LLVM to 12.0, according to upstream change log.
 * Adapt the Darwin linker patch.

(For some reason I've not figured out yet, cargo is a lot more
verbose while building, echoes the rustc invocation.)

Upstream changes:

Version 1.58.1 (2022-01-19)
===========================

* Fix race condition in `std::fs::remove_dir_all` ([CVE-2022-21658])
* [Handle captured arguments in the `useless_format` Clippy lint][clippy/8295]
* [Move `non_send_fields_in_send_ty` Clippy lint to nursery][clippy/8075]
* [Fix wrong error message displayed when some imports are missing][91254]
* [Fix rustfmt not formatting generated files from stdin][92912]

[CVE-2022-21658]: https://www.cve.org/CVERecord?id=CVE-2022-21658]
[91254]: rust-lang/rust#91254
[92912]: rust-lang/rust#92912
[clippy/8075]: rust-lang/rust-clippy#8075
[clippy/8295]: rust-lang/rust-clippy#8295

Version 1.58.0 (2022-01-13)
==========================

Language
--------

- [Format strings can now capture arguments simply by writing
  `{ident}` in the string.][90473] This works in all macros accepting
  format strings. Support for this in `panic!` (`panic!("{ident}")`)
  requires the 2021 edition; panic invocations in previous editions
  that appear to be trying to use this will result in a warning lint
  about not having the intended effect.
- [`*const T` pointers can now be dereferenced in const contexts.][89551]
- [The rules for when a generic struct implements `Unsize` have
  been relaxed.][90417]

Compiler
--------

- [Add LLVM CFI support to the Rust compiler][89652]
- [Stabilize -Z strip as -C strip][90058]. Note that while release
  builds already don't add debug symbols for the code you compile,
  the compiled standard library that ships with Rust includes debug
  symbols, so you may want to use the `strip` option to remove these
  symbols to produce smaller release binaries. Note that this release
  only includes support in rustc, not directly in cargo.
- [Add support for LLVM coverage mapping format versions 5 and 6][91207]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Update the minimum external LLVM to 12][90175]
- [Add `x86_64-unknown-none` at Tier 3*][89062]
- [Build musl dist artifacts with debuginfo enabled][90733]. When
  building release binaries using musl, you may want to use the newly
  stabilized strip option to remove these debug symbols, reducing
  the size of your binaries.
- [Don't abort compilation after giving a lint error][87337]
- [Error messages point at the source of trait bound obligations
  in more places][89580]

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

Libraries
---------

- [All remaining functions in the standard library have `#[must_use]`
  annotations where appropriate][89692], producing a warning when
  ignoring their return value. This helps catch mistakes such as
  expecting a function to mutate a value in place rather than return
  a new value.
- [Paths are automatically canonicalized on Windows for operations
  that support it][89174]
- [Re-enable debug checks for `copy` and `copy_nonoverlapping`][90041]
- [Implement `RefUnwindSafe` for `Rc<T>`][87467]
- [Make RSplit<T, P>: Clone not require T: Clone][90117]
- [Implement `Termination` for `Result<Infallible, E>`][88601].
  This allows writing `fn main() -> Result<Infallible, ErrorType>`,
  for a program whose successful exits never involve returning from
  `main` (for instance, a program that calls `exit`, or that uses
  `exec` to run another program).

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

- [`Metadata::is_symlink`]
- [`Path::is_symlink`]
- [`{integer}::saturating_div`]
- [`Option::unwrap_unchecked`]
- [`Result::unwrap_unchecked`]
- [`Result::unwrap_err_unchecked`]
- [`NonZero{unsigned}::is_power_of_two`]
- [`File::options`]

These APIs are now usable in const contexts:

- [`Duration::new`]
- [`Duration::checked_add`]
- [`Duration::saturating_add`]
- [`Duration::checked_sub`]
- [`Duration::saturating_sub`]
- [`Duration::checked_mul`]
- [`Duration::saturating_mul`]
- [`Duration::checked_div`]
- [`MaybeUninit::as_ptr`]
- [`MaybeUninit::as_mut_ptr`]
- [`MaybeUninit::assume_init`]
- [`MaybeUninit::assume_init_ref`]

Cargo
-----

- [Add --message-format for install command][cargo/10107]
- [Warn when alias shadows external subcommand][cargo/10082]

Rustdoc
-------

- [Show all Deref implementations recursively in rustdoc][90183]
- [Use computed visibility in rustdoc][88447]

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

- [Try all stable method candidates first before trying unstable
  ones][90329]. This change ensures that adding new nightly-only
  methods to the Rust standard library will not break code invoking
  methods of the same name from traits outside the standard library.
- Windows: [`std::process::Command` will no longer search the
  current directory for executables.][87704]
- [All proc-macro backward-compatibility lints are now deny-by-default.][88041]
- [proc_macro: Append .0 to unsuffixed float if it would otherwise
  become int token][90297]
- [Refactor weak symbols in std::sys::unix][90846]. This optimizes
  accesses to glibc functions, by avoiding the use of dlopen. This
  does not increase the [minimum expected version of
  glibc](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
  However, software distributions that use symbol versions to detect
  library dependencies, and which take weak symbols into account in
  that analysis, may detect rust binaries as requiring newer versions
  of glibc.
- [rustdoc now rejects some unexpected semicolons in doctests][91026]

Internal Changes
----------------

These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

- [Implement coherence checks for negative trait impls][90104]
- [Add rustc lint, warning when iterating over hashmaps][89558]
- [Optimize live point computation][90491]
- [Enable verification for 1/32nd of queries loaded from disk][90361]
- [Implement version of normalize_erasing_regions that allows for
  normalization failure][91255]

[87337]: rust-lang/rust#87337
[87467]: rust-lang/rust#87467
[87704]: rust-lang/rust#87704
[88041]: rust-lang/rust#88041
[88300]: rust-lang/rust#88300
[88447]: rust-lang/rust#88447
[88601]: rust-lang/rust#88601
[88624]: rust-lang/rust#88624
[89062]: rust-lang/rust#89062
[89174]: rust-lang/rust#89174
[89542]: rust-lang/rust#89542
[89551]: rust-lang/rust#89551
[89558]: rust-lang/rust#89558
[89580]: rust-lang/rust#89580
[89652]: rust-lang/rust#89652
[89677]: rust-lang/rust#89677
[89951]: rust-lang/rust#89951
[90041]: rust-lang/rust#90041
[90058]: rust-lang/rust#90058
[90104]: rust-lang/rust#90104
[90117]: rust-lang/rust#90117
[90175]: rust-lang/rust#90175
[90183]: rust-lang/rust#90183
[90297]: rust-lang/rust#90297
[90329]: rust-lang/rust#90329
[90361]: rust-lang/rust#90361
[90417]: rust-lang/rust#90417
[90473]: rust-lang/rust#90473
[90491]: rust-lang/rust#90491
[90733]: rust-lang/rust#90733
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[90896]: rust-lang/rust#90896
[91026]: rust-lang/rust#91026
[91207]: rust-lang/rust#91207
[91255]: rust-lang/rust#91255
[91301]: rust-lang/rust#91301
[cargo/10082]: rust-lang/cargo#10082
[cargo/10107]: rust-lang/cargo#10107
[`Metadata::is_symlink`]: https://doc.rust-lang.org/stable/std/fs/struct.Metadata.html#method.is_symlink
[`Path::is_symlink`]: https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.is_symlink
[`{integer}::saturating_div`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.saturating_div
[`Option::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_unchecked
[`Result::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_unchecked
[`Result::unwrap_err_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_err_unchecked
[`NonZero{unsigned}::is_power_of_two`]: https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html#method.is_power_of_two
[`File::options`]: https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.options
[`unix::process::ExitStatusExt::core_dumped`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.core_dumped
[`unix::process::ExitStatusExt::stopped_signal`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.stopped_signal
[`unix::process::ExitStatusExt::continued`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.continued
[`unix::process::ExitStatusExt::into_raw`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.into_raw
[`Duration::new`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.new
[`Duration::checked_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_add
[`Duration::saturating_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_add
[`Duration::checked_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_sub
[`Duration::saturating_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_sub
[`Duration::checked_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_mul
[`Duration::saturating_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_mul
[`Duration::checked_div`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_div
[`Duration::as_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f64
[`Duration::as_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f32
[`Duration::from_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f64
[`Duration::from_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f32
[`Duration::mul_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f64
[`Duration::mul_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f32
[`Duration::div_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f64
[`Duration::div_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f32
[`Duration::div_duration_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f64
[`Duration::div_duration_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f32
[`MaybeUninit::as_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[`MaybeUninit::as_mut_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_mut_ptr
[`MaybeUninit::assume_init`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Mar 1, 2022
Pkgsrc changes:
 * Bump bootstrap kit version to 1.57.0.
 * Bump require external LLVM to 12.0, according to upstream change log.
 * Adjust patches as needed, adjust line numbers.
 * Update checksum adjustments.  For some reason the vendor/libc checksum
   doesn't need fixing, apparently, it remains as commented out.
 * Add makefile to do all the NetBSD boostrap/cross builds (do-cross.mk).
   Allow passing in additions to CONFIGURE_ARGS via ADD_CONFIGURE_ARGS.

Upstream changes:

Version 1.58.1 (2022-01-19)
===========================

* Fix race condition in `std::fs::remove_dir_all` ([CVE-2022-21658])
* [Handle captured arguments in the `useless_format` Clippy lint][clippy/8295]
* [Move `non_send_fields_in_send_ty` Clippy lint to nursery][clippy/8075]
* [Fix wrong error message displayed when some imports are missing][91254]
* [Fix rustfmt not formatting generated files from stdin][92912]

[CVE-2022-21658]: https://www.cve.org/CVERecord?id=CVE-2022-21658]
[91254]: rust-lang/rust#91254
[92912]: rust-lang/rust#92912
[clippy/8075]: rust-lang/rust-clippy#8075
[clippy/8295]: rust-lang/rust-clippy#8295

Version 1.58.0 (2022-01-13)
==========================

Language
--------

- [Format strings can now capture arguments simply by writing
  `{ident}` in the string.][90473] This works in all macros accepting
  format strings. Support for this in `panic!` (`panic!("{ident}")`)
  requires the 2021 edition; panic invocations in previous editions
  that appear to be trying to use this will result in a warning lint
  about not having the intended effect.
- [`*const T` pointers can now be dereferenced in const contexts.][89551]
- [The rules for when a generic struct implements `Unsize` have
  been relaxed.][90417]

Compiler
--------

- [Add LLVM CFI support to the Rust compiler][89652]
- [Stabilize -Z strip as -C strip][90058]. Note that while release
  builds already don't add debug symbols for the code you compile,
  the compiled standard library that ships with Rust includes debug
  symbols, so you may want to use the `strip` option to remove these
  symbols to produce smaller release binaries. Note that this release
  only includes support in rustc, not directly in cargo.
- [Add support for LLVM coverage mapping format versions 5 and 6][91207]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Update the minimum external LLVM to 12][90175]
- [Add `x86_64-unknown-none` at Tier 3*][89062]
- [Build musl dist artifacts with debuginfo enabled][90733]. When
  building release binaries using musl, you may want to use the newly
  stabilized strip option to remove these debug symbols, reducing
  the size of your binaries.
- [Don't abort compilation after giving a lint error][87337]
- [Error messages point at the source of trait bound obligations
  in more places][89580]

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

Libraries
---------

- [All remaining functions in the standard library have `#[must_use]`
  annotations where appropriate][89692], producing a warning when
  ignoring their return value. This helps catch mistakes such as
  expecting a function to mutate a value in place rather than return
  a new value.
- [Paths are automatically canonicalized on Windows for operations
  that support it][89174]
- [Re-enable debug checks for `copy` and `copy_nonoverlapping`][90041]
- [Implement `RefUnwindSafe` for `Rc<T>`][87467]
- [Make RSplit<T, P>: Clone not require T: Clone][90117]
- [Implement `Termination` for `Result<Infallible, E>`][88601].
  This allows writing `fn main() -> Result<Infallible, ErrorType>`,
  for a program whose successful exits never involve returning from
  `main` (for instance, a program that calls `exit`, or that uses
  `exec` to run another program).

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

- [`Metadata::is_symlink`]
- [`Path::is_symlink`]
- [`{integer}::saturating_div`]
- [`Option::unwrap_unchecked`]
- [`Result::unwrap_unchecked`]
- [`Result::unwrap_err_unchecked`]
- [`NonZero{unsigned}::is_power_of_two`]
- [`File::options`]

These APIs are now usable in const contexts:

- [`Duration::new`]
- [`Duration::checked_add`]
- [`Duration::saturating_add`]
- [`Duration::checked_sub`]
- [`Duration::saturating_sub`]
- [`Duration::checked_mul`]
- [`Duration::saturating_mul`]
- [`Duration::checked_div`]
- [`MaybeUninit::as_ptr`]
- [`MaybeUninit::as_mut_ptr`]
- [`MaybeUninit::assume_init`]
- [`MaybeUninit::assume_init_ref`]

Cargo
-----

- [Add --message-format for install command][cargo/10107]
- [Warn when alias shadows external subcommand][cargo/10082]

Rustdoc
-------

- [Show all Deref implementations recursively in rustdoc][90183]
- [Use computed visibility in rustdoc][88447]

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

- [Try all stable method candidates first before trying unstable
  ones][90329]. This change ensures that adding new nightly-only
  methods to the Rust standard library will not break code invoking
  methods of the same name from traits outside the standard library.
- Windows: [`std::process::Command` will no longer search the
  current directory for executables.][87704]
- [All proc-macro backward-compatibility lints are now deny-by-default.][88041]
- [proc_macro: Append .0 to unsuffixed float if it would otherwise
  become int token][90297]
- [Refactor weak symbols in std::sys::unix][90846]. This optimizes
  accesses to glibc functions, by avoiding the use of dlopen. This
  does not increase the [minimum expected version of
  glibc](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
  However, software distributions that use symbol versions to detect
  library dependencies, and which take weak symbols into account in
  that analysis, may detect rust binaries as requiring newer versions
  of glibc.
- [rustdoc now rejects some unexpected semicolons in doctests][91026]

Internal Changes
----------------

These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

- [Implement coherence checks for negative trait impls][90104]
- [Add rustc lint, warning when iterating over hashmaps][89558]
- [Optimize live point computation][90491]
- [Enable verification for 1/32nd of queries loaded from disk][90361]
- [Implement version of normalize_erasing_regions that allows for
  normalization failure][91255]

[87337]: rust-lang/rust#87337
[87467]: rust-lang/rust#87467
[87704]: rust-lang/rust#87704
[88041]: rust-lang/rust#88041
[88300]: rust-lang/rust#88300
[88447]: rust-lang/rust#88447
[88601]: rust-lang/rust#88601
[88624]: rust-lang/rust#88624
[89062]: rust-lang/rust#89062
[89174]: rust-lang/rust#89174
[89542]: rust-lang/rust#89542
[89551]: rust-lang/rust#89551
[89558]: rust-lang/rust#89558
[89580]: rust-lang/rust#89580
[89652]: rust-lang/rust#89652
[89677]: rust-lang/rust#89677
[89951]: rust-lang/rust#89951
[90041]: rust-lang/rust#90041
[90058]: rust-lang/rust#90058
[90104]: rust-lang/rust#90104
[90117]: rust-lang/rust#90117
[90175]: rust-lang/rust#90175
[90183]: rust-lang/rust#90183
[90297]: rust-lang/rust#90297
[90329]: rust-lang/rust#90329
[90361]: rust-lang/rust#90361
[90417]: rust-lang/rust#90417
[90473]: rust-lang/rust#90473
[90491]: rust-lang/rust#90491
[90733]: rust-lang/rust#90733
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[90896]: rust-lang/rust#90896
[91026]: rust-lang/rust#91026
[91207]: rust-lang/rust#91207
[91255]: rust-lang/rust#91255
[91301]: rust-lang/rust#91301
[cargo/10082]: rust-lang/cargo#10082
[cargo/10107]: rust-lang/cargo#10107
[`Metadata::is_symlink`]: https://doc.rust-lang.org/stable/std/fs/struct.Metadata.html#method.is_symlink
[`Path::is_symlink`]: https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.is_symlink
[`{integer}::saturating_div`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.saturating_div
[`Option::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_unchecked
[`Result::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_unchecked
[`Result::unwrap_err_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_err_unchecked
[`NonZero{unsigned}::is_power_of_two`]: https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html#method.is_power_of_two
[`File::options`]: https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.options
[`unix::process::ExitStatusExt::core_dumped`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.core_dumped
[`unix::process::ExitStatusExt::stopped_signal`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.stopped_signal
[`unix::process::ExitStatusExt::continued`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.continued
[`unix::process::ExitStatusExt::into_raw`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.into_raw
[`Duration::new`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.new
[`Duration::checked_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_add
[`Duration::saturating_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_add
[`Duration::checked_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_sub
[`Duration::saturating_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_sub
[`Duration::checked_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_mul
[`Duration::saturating_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_mul
[`Duration::checked_div`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_div
[`Duration::as_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f64
[`Duration::as_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f32
[`Duration::from_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f64
[`Duration::from_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f32
[`Duration::mul_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f64
[`Duration::mul_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f32
[`Duration::div_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f64
[`Duration::div_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f32
[`Duration::div_duration_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f64
[`Duration::div_duration_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f32
[`MaybeUninit::as_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[`MaybeUninit::as_mut_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_mut_ptr
[`MaybeUninit::assume_init`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
@RalfJung RalfJung added the A-const-eval Area: Constant evaluation, covers all const contexts (static, const fn, ...) label Dec 1, 2024
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