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Stabilize const_fn_transmute, const_fn_union #85769

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merged 3 commits into from
Jul 28, 2021

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@jhpratt jhpratt commented May 28, 2021

This PR stabilizes the const_fn_transmute and const_fn_union features. It does not stabilize any methods (obviously aside from transmute) that are blocked on only these features.

Closes #53605. Closes #51909.

Stabilization report: #85769 (comment)

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Some changes occurred in src/tools/clippy.

cc @rust-lang/clippy

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r? @yaahc

(rust-highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 28, 2021
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jhpratt commented May 28, 2021

@rustbot label: -S-waiting-on-review +S-waiting-on-author +A-const-fn +T-compiler

@rustbot rustbot added A-const-fn S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 28, 2021
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Cc @rust-lang/wg-const-eval

@jhpratt jhpratt force-pushed the stabilize-const-transmute-union branch from 25f21ed to 2fb3304 Compare May 31, 2021 00:55
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@jhpratt jhpratt force-pushed the stabilize-const-transmute-union branch from 2fb3304 to 990a295 Compare June 1, 2021 23:15
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jhpratt commented Jun 2, 2021

Looking at the failure, I'm not really sure what should be done about this. It's wholly unrelated to this PR (it's only being run because I remove the feature gate) and the lints are objectively correct — but it's also what's being tested. I think it's an issue with the script that's running the tests: -D warnings shouldn't be passed when clippy warnings are being checked.

When running x t --stage 2 locally, everything succeeds. I use Fedora 34/x64_64-unknown-linux-gnu if that's relevant.

r? @oli-obk

@rust-highfive rust-highfive assigned oli-obk and unassigned yaahc Jun 2, 2021
@jhpratt jhpratt marked this pull request as ready for review June 2, 2021 00:09
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RalfJung commented Jun 2, 2021

It's wholly unrelated to this PR (it's only being run because I remove the feature gate)

The test will get run by bors either way, so even if it wouldn't be run here we'd still get the same failure later. Therefore it is definitely related to the PR, in the sense that these warnings do not show up on master, but they do show up with your PR applied.
@rust-lang/clippy what do you recommend we do with these -D warning failures in clippy tests? Somehow just stabilizing a feature makes new warnings show up...?

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RalfJung commented Jun 2, 2021

Oh wait, I misread... these ware not new warnings, the line numbers are just wrong.
Sadly I don't know how to auto---bless clippy tests, so I think you will have to adjust the line numbers in the stderr files by hand.

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jhpratt commented Jun 2, 2021

Huh, you're right. Not sure why the lines removed weren't shown by rustbot. All I saw was the additions and assumed it was an error.

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flip1995 commented Jun 2, 2021

./x.py test --bless src/tools/clippy should work.

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jhpratt commented Jun 2, 2021

Thanks @flip1995! I incidentally just tried that figuring it can't hurt and found it helped :)

@jhpratt jhpratt force-pushed the stabilize-const-transmute-union branch from 990a295 to 3d7fdc3 Compare June 2, 2021 07:42
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flip1995 commented Jun 2, 2021

Great! Clippy changes LGTM. 👍

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bors commented Jul 28, 2021

☀️ Test successful - checks-actions
Approved by: RalfJung
Pushing 8b50cc9 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 28, 2021
@bors bors merged commit 8b50cc9 into rust-lang:master Jul 28, 2021
@rustbot rustbot added this to the 1.56.0 milestone Jul 28, 2021
@jhpratt jhpratt deleted the stabilize-const-transmute-union branch July 28, 2021 03:36
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ehuss commented Jul 29, 2021

Would someone be willing to update the documentation (here) for this?

@jplatte jplatte mentioned this pull request Jul 30, 2021
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@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Aug 5, 2021
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Oct 22, 2021
Pkgsrc changes:
 * Remove one now-longer-applicable patch, adjust a few others
 * Bump bootstrap requirements to 1.55.0.

Upstream changes:

Version 1.56.0 (2021-10-21)
========================

Language
--------

- [The 2021 Edition is now stable.][rust#88100]
  See [the edition guide][rust-2021-edition-guide] for more details.
- [The pattern in `binding @ pattern` can now also introduce new bindings.]
  [rust#85305]
- [Union field access is permitted in `const fn`.][rust#85769]

[rust-2021-edition-guide]: https://doc.rust-lang.org/nightly/edition-guide/rust-2021/index.html

Compiler
--------

- [Upgrade to LLVM 13.][rust#87570]
- [Support memory, address, and thread sanitizers on
  aarch64-unknown-freebsd.][rust#88023]
- [Allow specifying a deployment target version for all iOS targets][rust#87699]
- [Warnings can be forced on with `--force-warn`.][rust#87472]
  This feature is primarily intended for usage by `cargo fix`,
  rather than end users.
- [Promote `aarch64-apple-ios-sim` to Tier 2\*.][rust#87760]
- [Add `powerpc-unknown-freebsd` at Tier 3\*.][rust#87370]
- [Add `riscv32imc-esp-espidf` at Tier 3\*.][rust#87666]

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

Libraries
---------

- [Allow writing of incomplete UTF-8 sequences via stdout/stderr on Windows.]
  [rust#83342]
  The Windows console still requires valid Unicode, but this change allows
  splitting a UTF-8 character across multiple write calls. This allows, for
  instance, programs that just read and write data buffers (e.g. copying a file
  to stdout) without regard for Unicode or character boundaries.
- [Prefer `AtomicU{64,128}` over Mutex for Instant backsliding protection.]
  [rust#83093]
  For this use case, atomics scale much better under contention.
- [Implement `Extend<(A, B)>` for `(Extend<A>, Extend<B>)`][rust#85835]
- [impl Default, Copy, Clone for std::io::Sink and std::io::Empty][rust#86744]
- [`impl From<[(K, V); N]>` for all collections.][rust#84111]
- [Remove `P: Unpin` bound on impl Future for Pin.][rust#81363]
- [Treat invalid environment variable names as non-existent.][rust#86183]
  Previously, the environment functions would panic if given a
  variable name with an internal null character or equal sign (`=`).
  Now, these functions will just treat such names as non-existent
  variables, since the OS cannot represent the existence of a
  variable with such a name.

Stabilised APIs
---------------

- [`std::os::unix::fs::chroot`]
- [`UnsafeCell::raw_get`]
- [`BufWriter::into_parts`]
- [`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]
  These APIs were previously stable in `std`, but are now also available
  in `core`.
- [`Vec::shrink_to`]
- [`String::shrink_to`]
- [`OsString::shrink_to`]
- [`PathBuf::shrink_to`]
- [`BinaryHeap::shrink_to`]
- [`VecDeque::shrink_to`]
- [`HashMap::shrink_to`]
- [`HashSet::shrink_to`]

These APIs are now usable in const contexts:

- [`std::mem::transmute`]
- [`[T]::first`][`slice::first`]
- [`[T]::split_first`][`slice::split_first`]
- [`[T]::last`][`slice::last`]
- [`[T]::split_last`][`slice::split_last`]

Cargo
-----

- [Cargo supports specifying a minimum supported Rust version in Cargo.toml.]
  [`rust-version`] This has no effect at present on dependency
  version selection.  We encourage crates to specify their minimum
  supported Rust version, and we encourage CI systems that support
  Rust code to include a crate's specified minimum version in the
  text matrix for that crate by default.

Compatibility notes
-------------------

- [Update to new argument parsing rules on Windows.][rust#87580]
  This adjusts Rust's standard library to match the behavior of the standard
  libraries for C/C++. The rules have changed slightly over time, and this PR
  brings us to the latest set of rules (changed in 2008).
- [Disallow the aapcs calling convention on aarch64][rust#88399]
  This was already not supported by LLVM; this change surfaces this lack of
  support with a better error message.
- [Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default][rust#87385]
- [Warn when an escaped newline skips multiple lines.][rust#87671]
- [Calls to `libc::getpid` / `std::process::id` from `Command::pre_exec`
  may return different values on glibc <= 2.24.][rust#81825] Rust
  now invokes the `clone3` system call directly, when available,
  to use new functionality available via that system call. Older
  versions of glibc cache the result of `getpid`, and only update
  that cache when calling glibc's clone/fork functions, so a direct
  system call bypasses that cache update. glibc 2.25 and newer no
  longer cache `getpid` for exactly this reason.

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.

- [LLVM is compiled with PGO in published x86_64-unknown-linux-gnu
  artifacts.][rust#88069] This improves the performance of most Rust builds.

- [Unify representation of macros in internal data structures.][rust#88019]
  This change fixes a host of bugs with the handling of macros by the compiler,
  as well as rustdoc.

[`std::os::unix::fs::chroot`]: https://doc.rust-lang.org/stable/std/os/unix/fs/fn.chroot.html
[`Iterator::intersperse`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`Iterator::intersperse_with`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`UnsafeCell::raw_get`]: https://doc.rust-lang.org/stable/std/cell/struct.UnsafeCell.html#method.raw_get
[`BufWriter::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.BufWriter.html#method.into_parts
[`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]: rust-lang/rust#84662
[`Vec::shrink_to`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.shrink_to
[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.shrink_to
[`OsString::shrink_to`]: https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.shrink_to
[`PathBuf::shrink_to`]: https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.shrink_to
[`BinaryHeap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.shrink_to
[`VecDeque::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.shrink_to
[`HashMap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_map/struct.HashMap.html#method.shrink_to
[`HashSet::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_set/struct.HashSet.html#method.shrink_to
[`std::mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
[`slice::first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first
[`slice::split_first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first
[`slice::last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last
[`slice::split_last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last
[`rust-version`]: https://doc.rust-lang.org/nightly/cargo/reference/manifest.html#the-rust-version-field
[rust#87671]: rust-lang/rust#87671
[rust#86183]: rust-lang/rust#86183
[rust#87385]: rust-lang/rust#87385
[rust#88100]: rust-lang/rust#88100
[rust#86860]: rust-lang/rust#86860
[rust#84039]: rust-lang/rust#84039
[rust#86492]: rust-lang/rust#86492
[rust#88363]: rust-lang/rust#88363
[rust#85305]: rust-lang/rust#85305
[rust#87832]: rust-lang/rust#87832
[rust#88069]: rust-lang/rust#88069
[rust#87472]: rust-lang/rust#87472
[rust#87699]: rust-lang/rust#87699
[rust#87570]: rust-lang/rust#87570
[rust#88023]: rust-lang/rust#88023
[rust#87760]: rust-lang/rust#87760
[rust#87370]: rust-lang/rust#87370
[rust#87580]: rust-lang/rust#87580
[rust#83342]: rust-lang/rust#83342
[rust#83093]: rust-lang/rust#83093
[rust#88177]: rust-lang/rust#88177
[rust#88548]: rust-lang/rust#88548
[rust#88551]: rust-lang/rust#88551
[rust#88299]: rust-lang/rust#88299
[rust#88220]: rust-lang/rust#88220
[rust#85835]: rust-lang/rust#85835
[rust#86879]: rust-lang/rust#86879
[rust#86744]: rust-lang/rust#86744
[rust#84662]: rust-lang/rust#84662
[rust#86593]: rust-lang/rust#86593
[rust#81050]: rust-lang/rust#81050
[rust#81363]: rust-lang/rust#81363
[rust#84111]: rust-lang/rust#84111
[rust#85769]: rust-lang/rust#85769 (comment)
[rust#88490]: rust-lang/rust#88490
[rust#88269]: rust-lang/rust#88269
[rust#84176]: rust-lang/rust#84176
[rust#88399]: rust-lang/rust#88399
[rust#88227]: rust-lang/rust#88227
[rust#88200]: rust-lang/rust#88200
[rust#82776]: rust-lang/rust#82776
[rust#88077]: rust-lang/rust#88077
[rust#87728]: rust-lang/rust#87728
[rust#87050]: rust-lang/rust#87050
[rust#87619]: rust-lang/rust#87619
[rust#81825]: rust-lang/rust#81825 (comment)
[rust#88019]: rust-lang/rust#88019
[rust#87666]: rust-lang/rust#87666
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Nov 20, 2021
Pkgsrc changes:
 * Bump bootstrap kit version to 1.55.0.
 * Adjust patches as needed, some no longer apply (so removed)
 * Update checksum adjustments.
 * Avoid rust-llvm on SunOS
 * Optionally build docs
 * Remove reference to closed/old PR#54621

Upstream changes:

Version 1.56.1 (2021-11-01)
===========================

- New lints to detect the presence of bidirectional-override Unicode
  codepoints in the compiled source code ([CVE-2021-42574])

[CVE-2021-42574]: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-42574

Version 1.56.0 (2021-10-21)
========================

Language
--------

- [The 2021 Edition is now stable.][rust#88100]
  See [the edition guide][rust-2021-edition-guide] for more details.
- [The pattern in `binding @ pattern` can now also introduce new bindings.]
  [rust#85305]
- [Union field access is permitted in `const fn`.][rust#85769]

[rust-2021-edition-guide]:
  https://doc.rust-lang.org/nightly/edition-guide/rust-2021/index.html

Compiler
--------

- [Upgrade to LLVM 13.][rust#87570]
- [Support memory, address, and thread sanitizers on aarch64-unknown-freebsd.]
  [rust#88023]
- [Allow specifying a deployment target version for all iOS targets][rust#87699]
- [Warnings can be forced on with `--force-warn`.][rust#87472]
  This feature is primarily intended for usage by `cargo fix`, rather than
  end users.
- [Promote `aarch64-apple-ios-sim` to Tier 2\*.][rust#87760]
- [Add `powerpc-unknown-freebsd` at Tier 3\*.][rust#87370]
- [Add `riscv32imc-esp-espidf` at Tier 3\*.][rust#87666]

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

Libraries
---------

- [Allow writing of incomplete UTF-8 sequences via stdout/stderr on Windows.]
  [rust#83342]
  The Windows console still requires valid Unicode, but this change allows
  splitting a UTF-8 character across multiple write calls. This allows, for
  instance, programs that just read and write data buffers (e.g. copying a file
  to stdout) without regard for Unicode or character boundaries.
- [Prefer `AtomicU{64,128}` over Mutex for Instant backsliding protection.]
  [rust#83093]
  For this use case, atomics scale much better under contention.
- [Implement `Extend<(A, B)>` for `(Extend<A>, Extend<B>)`][rust#85835]
- [impl Default, Copy, Clone for std::io::Sink and std::io::Empty][rust#86744]
- [`impl From<[(K, V); N]>` for all collections.][rust#84111]
- [Remove `P: Unpin` bound on impl Future for Pin.][rust#81363]
- [Treat invalid environment variable names as non-existent.][rust#86183]
  Previously, the environment functions would panic if given a
  variable name with an internal null character or equal sign (`=`).
  Now, these functions will just treat such names as non-existent
  variables, since the OS cannot represent the existence of a
  variable with such a name.

Stabilised APIs
---------------

- [`std::os::unix::fs::chroot`]
- [`UnsafeCell::raw_get`]
- [`BufWriter::into_parts`]
- [`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]
  These APIs were previously stable in `std`, but are now also available
  in `core`.
- [`Vec::shrink_to`]
- [`String::shrink_to`]
- [`OsString::shrink_to`]
- [`PathBuf::shrink_to`]
- [`BinaryHeap::shrink_to`]
- [`VecDeque::shrink_to`]
- [`HashMap::shrink_to`]
- [`HashSet::shrink_to`]

These APIs are now usable in const contexts:

- [`std::mem::transmute`]
- [`[T]::first`][`slice::first`]
- [`[T]::split_first`][`slice::split_first`]
- [`[T]::last`][`slice::last`]
- [`[T]::split_last`][`slice::split_last`]

Cargo
-----

- [Cargo supports specifying a minimum supported Rust version in Cargo.toml.]
  [`rust-version`]
  This has no effect at present on dependency version selection.
  We encourage crates to specify their minimum supported Rust
  version, and we encourage CI systems that support Rust code to
  include a crate's specified minimum version in the text matrix
  for that crate by default.

Compatibility notes
-------------------

- [Update to new argument parsing rules on Windows.][rust#87580]
  This adjusts Rust's standard library to match the behavior of the standard
  libraries for C/C++. The rules have changed slightly over time, and this PR
  brings us to the latest set of rules (changed in 2008).
- [Disallow the aapcs calling convention on aarch64][rust#88399]
  This was already not supported by LLVM; this change surfaces this lack of
  support with a better error message.
- [Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default][rust#87385]
- [Warn when an escaped newline skips multiple lines.][rust#87671]
- [Calls to `libc::getpid` / `std::process::id` from `Command::pre_exec`
  may return different values on glibc <= 2.24.][rust#81825]
  Rust now invokes the `clone3` system call directly, when available,
  to use new functionality available via that system call. Older
  versions of glibc cache the result of `getpid`, and only update
  that cache when calling glibc's clone/fork functions, so a direct
  system call bypasses that cache update. glibc 2.25 and newer no
  longer cache `getpid` for exactly this reason.

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.

- [LLVM is compiled with PGO in published x86_64-unknown-linux-gnu artifacts.]
  [rust#88069]
  This improves the performance of most Rust builds.
- [Unify representation of macros in internal data structures.][rust#88019]
  This change fixes a host of bugs with the handling of macros by the compiler,
  as well as rustdoc.

[`std::os::unix::fs::chroot`]: https://doc.rust-lang.org/stable/std/os/unix/fs/fn.chroot.html
[`Iterator::intersperse`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`Iterator::intersperse_with`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`UnsafeCell::raw_get`]: https://doc.rust-lang.org/stable/std/cell/struct.UnsafeCell.html#method.raw_get
[`BufWriter::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.BufWriter.html#method.into_parts
[`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]: rust-lang/rust#84662
[`Vec::shrink_to`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.shrink_to
[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.shrink_to
[`OsString::shrink_to`]: https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.shrink_to
[`PathBuf::shrink_to`]: https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.shrink_to
[`BinaryHeap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.shrink_to
[`VecDeque::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.shrink_to
[`HashMap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_map/struct.HashMap.html#method.shrink_to
[`HashSet::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_set/struct.HashSet.html#method.shrink_to
[`std::mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
[`slice::first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first
[`slice::split_first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first
[`slice::last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last
[`slice::split_last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last
[`rust-version`]: https://doc.rust-lang.org/nightly/cargo/reference/manifest.html#the-rust-version-field
[rust#87671]: rust-lang/rust#87671
[rust#86183]: rust-lang/rust#86183
[rust#87385]: rust-lang/rust#87385
[rust#88100]: rust-lang/rust#88100
[rust#86860]: rust-lang/rust#86860
[rust#84039]: rust-lang/rust#84039
[rust#86492]: rust-lang/rust#86492
[rust#88363]: rust-lang/rust#88363
[rust#85305]: rust-lang/rust#85305
[rust#87832]: rust-lang/rust#87832
[rust#88069]: rust-lang/rust#88069
[rust#87472]: rust-lang/rust#87472
[rust#87699]: rust-lang/rust#87699
[rust#87570]: rust-lang/rust#87570
[rust#88023]: rust-lang/rust#88023
[rust#87760]: rust-lang/rust#87760
[rust#87370]: rust-lang/rust#87370
[rust#87580]: rust-lang/rust#87580
[rust#83342]: rust-lang/rust#83342
[rust#83093]: rust-lang/rust#83093
[rust#88177]: rust-lang/rust#88177
[rust#88548]: rust-lang/rust#88548
[rust#88551]: rust-lang/rust#88551
[rust#88299]: rust-lang/rust#88299
[rust#88220]: rust-lang/rust#88220
[rust#85835]: rust-lang/rust#85835
[rust#86879]: rust-lang/rust#86879
[rust#86744]: rust-lang/rust#86744
[rust#84662]: rust-lang/rust#84662
[rust#86593]: rust-lang/rust#86593
[rust#81050]: rust-lang/rust#81050
[rust#81363]: rust-lang/rust#81363
[rust#84111]: rust-lang/rust#84111
[rust#85769]: rust-lang/rust#85769 (comment)
[rust#88490]: rust-lang/rust#88490
[rust#88269]: rust-lang/rust#88269
[rust#84176]: rust-lang/rust#84176
[rust#88399]: rust-lang/rust#88399
[rust#88227]: rust-lang/rust#88227
[rust#88200]: rust-lang/rust#88200
[rust#82776]: rust-lang/rust#82776
[rust#88077]: rust-lang/rust#88077
[rust#87728]: rust-lang/rust#87728
[rust#87050]: rust-lang/rust#87050
[rust#87619]: rust-lang/rust#87619
[rust#81825]: rust-lang/rust#81825 (comment)
[rust#88019]: rust-lang/rust#88019
[rust#87666]: rust-lang/rust#87666

Version 1.55.0 (2021-09-09)
============================

Language
--------
- [You can now write open "from" range patterns (`X..`), which will start
  at `X` and will end at the maximum value of the integer.][83918]
- [You can now explicitly import the prelude of different editions
  through `std::prelude` (e.g. `use std::prelude::rust_2021::*;`).][86294]

Compiler
--------
- [Added tier 3\* support for `powerpc64le-unknown-freebsd`.][83572]

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

Libraries
---------

- [Updated std's float parsing to use the Eisel-Lemire algorithm.][86761]
  These improvements should in general provide faster string parsing of floats,
  no longer reject certain valid floating point values, and reduce
  the produced code size for non-stripped artifacts.
- [`string::Drain` now implements `AsRef<str>` and `AsRef<[u8]>`.][86858]

Stabilised APIs
---------------

- [`Bound::cloned`]
- [`Drain::as_str`]
- [`IntoInnerError::into_error`]
- [`IntoInnerError::into_parts`]
- [`MaybeUninit::assume_init_mut`]
- [`MaybeUninit::assume_init_ref`]
- [`MaybeUninit::write`]
- [`array::map`]
- [`ops::ControlFlow`]
- [`x86::_bittest`]
- [`x86::_bittestandcomplement`]
- [`x86::_bittestandreset`]
- [`x86::_bittestandset`]
- [`x86_64::_bittest64`]
- [`x86_64::_bittestandcomplement64`]
- [`x86_64::_bittestandreset64`]
- [`x86_64::_bittestandset64`]

The following previously stable functions are now `const`.

- [`str::from_utf8_unchecked`]


Cargo
-----
- [Cargo will now deduplicate compiler diagnostics to the terminal when invoking
  rustc in parallel such as when using `cargo test`.][cargo/9675]
- [The package definition in `cargo metadata` now includes the `"default_run"`
  field from the manifest.][cargo/9550]
- [Added `cargo d` as an alias for `cargo doc`.][cargo/9680]
- [Added `{lib}` as formatting option for `cargo tree` to print the `"lib_name"`
  of packages.][cargo/9663]

Rustdoc
-------
- [Added "Go to item on exact match" search option.][85876]
- [The "Implementors" section on traits no longer shows redundant
  method definitions.][85970]
- [Trait implementations are toggled open by default.][86260] This should
  make the implementations more searchable by tools like `CTRL+F` in
  your browser.
- [Intra-doc links should now correctly resolve associated items (e.g. methods)
  through type aliases.][86334]
- [Traits which are marked with `#[doc(hidden)]` will no longer appear in the
  "Trait Implementations" section.][86513]


Compatibility Notes
-------------------
- [std functions that return an `io::Error` will no longer use the
  `ErrorKind::Other` variant.][85746] This is to better reflect that these
  kinds of errors could be categorised [into newer more specific `ErrorKind`
  variants][79965], and that they do not represent a user error.
- [Using environment variable names with `process::Command` on Windows now
  behaves as expected.][85270] Previously using envionment variables with
  `Command` would cause them to be ASCII-uppercased.
- [Rustdoc will now warn on using rustdoc lints that aren't prefixed
  with `rustdoc::`][86849]

[86849]: rust-lang/rust#86849
[86513]: rust-lang/rust#86513
[86334]: rust-lang/rust#86334
[86260]: rust-lang/rust#86260
[85970]: rust-lang/rust#85970
[85876]: rust-lang/rust#85876
[83572]: rust-lang/rust#83572
[86294]: rust-lang/rust#86294
[86858]: rust-lang/rust#86858
[86761]: rust-lang/rust#86761
[85769]: rust-lang/rust#85769
[85746]: rust-lang/rust#85746
[85305]: rust-lang/rust#85305
[85270]: rust-lang/rust#85270
[84111]: rust-lang/rust#84111
[83918]: rust-lang/rust#83918
[79965]: rust-lang/rust#79965
[87370]: rust-lang/rust#87370
[87298]: rust-lang/rust#87298
[cargo/9663]: rust-lang/cargo#9663
[cargo/9675]: rust-lang/cargo#9675
[cargo/9550]: rust-lang/cargo#9550
[cargo/9680]: rust-lang/cargo#9680
[cargo/9663]: rust-lang/cargo#9663
[`array::map`]: https://doc.rust-lang.org/stable/std/primitive.array.html#method.map
[`Bound::cloned`]: https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.cloned
[`Drain::as_str`]: https://doc.rust-lang.org/stable/std/string/struct.Drain.html#method.as_str
[`IntoInnerError::into_error`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_error
[`IntoInnerError::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_parts
[`MaybeUninit::assume_init_mut`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_mut
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
[`MaybeUninit::write`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.write
[`Seek::rewind`]: https://doc.rust-lang.org/stable/std/io/trait.Seek.html#method.rewind
[`ops::ControlFlow`]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html
[`str::from_utf8_unchecked`]: https://doc.rust-lang.org/stable/std/str/fn.from_utf8_unchecked.html
[`x86::_bittest`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittest.html
[`x86::_bittestandcomplement`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandcomplement.html
[`x86::_bittestandreset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandreset.html
[`x86::_bittestandset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandset.html
[`x86_64::_bittest64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittest64.html
[`x86_64::_bittestandcomplement64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandcomplement64.html
[`x86_64::_bittestandreset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandreset64.html
[`x86_64::_bittestandset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandset64.html
bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 6, 2024
Add a Lint for Pointer to Integer Transmutes in Consts

Fixes rust-lang#87525

This PR adds a MirLint for pointer to integer transmutes in const functions and associated consts. The implementation closely follows this comment: rust-lang#85769 (comment). More details about the implementation can be found in the comments.

Note: This could break some sound code as mentioned by RalfJung in rust-lang#85769 (comment):

> ... technically const-code could transmute/cast an int to a ptr and then transmute it back and that would be correct -- so the lint will deny some sound code. Does not seem terribly likely though.

References:
1. https://doc.rust-lang.org/std/mem/fn.transmute.html
2. https://doc.rust-lang.org/reference/items/associated-items.html#associated-constants
lnicola pushed a commit to lnicola/rust-analyzer that referenced this pull request Oct 8, 2024
Add a Lint for Pointer to Integer Transmutes in Consts

Fixes #87525

This PR adds a MirLint for pointer to integer transmutes in const functions and associated consts. The implementation closely follows this comment: rust-lang/rust#85769 (comment). More details about the implementation can be found in the comments.

Note: This could break some sound code as mentioned by RalfJung in rust-lang/rust#85769 (comment):

> ... technically const-code could transmute/cast an int to a ptr and then transmute it back and that would be correct -- so the lint will deny some sound code. Does not seem terribly likely though.

References:
1. https://doc.rust-lang.org/std/mem/fn.transmute.html
2. https://doc.rust-lang.org/reference/items/associated-items.html#associated-constants
flip1995 pushed a commit to flip1995/rust-clippy that referenced this pull request Oct 10, 2024
Add a Lint for Pointer to Integer Transmutes in Consts

Fixes #87525

This PR adds a MirLint for pointer to integer transmutes in const functions and associated consts. The implementation closely follows this comment: rust-lang/rust#85769 (comment). More details about the implementation can be found in the comments.

Note: This could break some sound code as mentioned by RalfJung in rust-lang/rust#85769 (comment):

> ... technically const-code could transmute/cast an int to a ptr and then transmute it back and that would be correct -- so the lint will deny some sound code. Does not seem terribly likely though.

References:
1. https://doc.rust-lang.org/std/mem/fn.transmute.html
2. https://doc.rust-lang.org/reference/items/associated-items.html#associated-constants
RalfJung pushed a commit to RalfJung/miri that referenced this pull request Oct 14, 2024
Add a Lint for Pointer to Integer Transmutes in Consts

Fixes #87525

This PR adds a MirLint for pointer to integer transmutes in const functions and associated consts. The implementation closely follows this comment: rust-lang/rust#85769 (comment). More details about the implementation can be found in the comments.

Note: This could break some sound code as mentioned by RalfJung in rust-lang/rust#85769 (comment):

> ... technically const-code could transmute/cast an int to a ptr and then transmute it back and that would be correct -- so the lint will deny some sound code. Does not seem terribly likely though.

References:
1. https://doc.rust-lang.org/std/mem/fn.transmute.html
2. https://doc.rust-lang.org/reference/items/associated-items.html#associated-constants
@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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