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Added #[repr(transparent)] to core::cmp::Reverse #81879

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merged 1 commit into from
Mar 9, 2021

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@imbrem imbrem commented Feb 8, 2021

I found casting from an &T to an &Reverse<T> potentially useful, but found that Reverse was not #[repr(transparent)], so after asking about it on Reddit, I decided to go ahead and make a pull request which simply adds the attribute to the struct.

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r? @joshtriplett

(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 Feb 8, 2021
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imbrem commented Feb 11, 2021

Is there anything I need to do to get this merged?

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imbrem commented Feb 20, 2021

@xfix ? @joshtriplett ?

@JohnCSimon JohnCSimon added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 7, 2021
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jyn514 commented Mar 8, 2021

r? @m-ou-se

@rust-highfive rust-highfive assigned m-ou-se and unassigned joshtriplett Mar 8, 2021
@m-ou-se m-ou-se added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Mar 8, 2021
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m-ou-se commented Mar 8, 2021

I suppose this technically requires an FCP:

@rfcbot merge

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rfcbot commented Mar 8, 2021

Team member @m-ou-se 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. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Mar 8, 2021
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🔔 This is now entering its final comment period, as per the review above. 🔔

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m-ou-se commented Mar 9, 2021

Alright, good enough.

@bors r+ rollup

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bors commented Mar 9, 2021

📌 Commit f847ff1 has been approved by m-ou-se

@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 Mar 9, 2021
m-ou-se added a commit to m-ou-se/rust that referenced this pull request Mar 9, 2021
…t, r=m-ou-se

Added #[repr(transparent)] to core::cmp::Reverse

I found casting from an `&T` to an `&Reverse<T>` potentially useful, but found that `Reverse` was not `#[repr(transparent)]`, so after asking about it [on Reddit](https://www.reddit.com/r/rust/comments/le60uv/make_stdcmpreverse_reprtransparent_and_add_a/), I decided to go ahead and make a pull request which simply adds the attribute to the struct.
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 9, 2021
Rollup of 8 pull requests

Successful merges:

 - rust-lang#81127 (Improve sift_down performance in BinaryHeap)
 - rust-lang#81879 (Added #[repr(transparent)] to core::cmp::Reverse)
 - rust-lang#82048 (or-patterns: disallow in `let` bindings)
 - rust-lang#82731 (Bump libc dependency of std to 0.2.88.)
 - rust-lang#82799 (Add regression test for rust-lang#75525)
 - rust-lang#82841 (Change x64 size checks to not apply to x32.)
 - rust-lang#82883 (Update Cargo)
 - rust-lang#82887 (Update CONTRIBUTING.md)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 0083e6c into rust-lang:master Mar 9, 2021
@rustbot rustbot added this to the 1.52.0 milestone Mar 9, 2021
@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 Mar 19, 2021
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Mar 25, 2021
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request May 9, 2021
Package changes:
 * bump bootstraps to 1.51.0.
 * adjust patches and cargo checksums as required
 * 1.51 failed to build natively on 32-bit armv7, there is hope
   that this is fixed with 1.52.  (1.51 can be built with netbsd32
   emulation on a aarch64 system).

Upsteream changes:

Version 1.52.0 (2021-05-06)
============================

Language
--------
- [Added the `unsafe_op_in_unsafe_fn` lint, which checks whether the unsafe
  code in an `unsafe fn` is wrapped in a `unsafe` block.][79208] This lint
  is allowed by default, and may become a warning or hard error in a
  future edition.
- [You can now cast mutable references to arrays to a pointer of the same
  type as the element.][81479]

Compiler
--------
- [Upgraded the default LLVM to LLVM 12.][81451]

Added tier 3\* support for the following targets.

- [`s390x-unknown-linux-musl`][82166]
- [`riscv32gc-unknown-linux-musl` & `riscv64gc-unknown-linux-musl`][82202]
- [`powerpc-unknown-openbsd`][82733]

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

Libraries
---------
- [`OsString` now implements `Extend` and `FromIterator`.][82121]
- [`cmp::Reverse` now has `#[repr(transparent)]` representation.][81879]
- [`Arc<impl Error>` now implements `error::Error`.][80553]
- [All integer division and remainder operations are now `const`.][80962]

Stabilised APIs
-------------
- [`Arguments::as_str`]
- [`char::MAX`]
- [`char::REPLACEMENT_CHARACTER`]
- [`char::UNICODE_VERSION`]
- [`char::decode_utf16`]
- [`char::from_digit`]
- [`char::from_u32_unchecked`]
- [`char::from_u32`]
- [`slice::partition_point`]
- [`str::rsplit_once`]
- [`str::split_once`]

The following previously stable APIs are now `const`.

- [`char::len_utf8`]
- [`char::len_utf16`]
- [`char::to_ascii_uppercase`]
- [`char::to_ascii_lowercase`]
- [`char::eq_ignore_ascii_case`]
- [`u8::to_ascii_uppercase`]
- [`u8::to_ascii_lowercase`]
- [`u8::eq_ignore_ascii_case`]

Rustdoc
-------
- [Rustdoc lints are now treated as a tool lint, meaning that lints are
  now prefixed with `rustdoc::`
  (e.g. `#[warn(rustdoc::non_autolinks)]`).][80527]

  Using the old style is still allowed, and will become a warning in
  a future release.
- [Rustdoc now supports argument files.][82261]
- [Rustdoc now generates smart punctuation for documentation.][79423]
- [You can now use "task lists" in Rustdoc Markdown.][81766] E.g.
  ```markdown
  - [x] Complete
  - [ ] Todo
  ```

Misc
----
- [You can now pass multiple filters to tests.][81356] E.g.
  `cargo test -- foo bar` will run all tests that match `foo` and `bar`.
- [Rustup now distributes PDB symbols for the `std` library on Windows,
  allowing you to see `std` symbols when debugging.][82218]

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

- [Check the result cache before the DepGraph when ensuring queries][81855]
- [Try fast_reject::simplify_type in coherence before doing full check][81744]
- [Only store a LocalDefId in some HIR nodes][81611]
- [Store HIR attributes in a side table][79519]

Compatibility Notes
-------------------
- [Cargo build scripts are now forbidden from setting `RUSTC_BOOTSTRAP`.]
  [cargo/9181]
- [Removed support for the `x86_64-rumprun-netbsd` target.][82594]
- [Deprecated the `x86_64-sun-solaris` target in favor of `x86_64-pc-solaris`.]
  [82216]
- [Rustdoc now only accepts `,`, ` `, and `\t` as delimiters for specifying
  languages in code blocks.][78429]
- [Rustc now catches more cases of `pub_use_of_private_extern_crate`][80763]
- [Changes in how proc macros handle whitespace may lead to panics when used
  with older `proc-macro-hack` versions. A `cargo update` should be sufficient
  to fix this in all cases.][84136]

[84136]: rust-lang/rust#84136
[80763]: rust-lang/rust#80763
[82166]: rust-lang/rust#82166
[82121]: rust-lang/rust#82121
[81879]: rust-lang/rust#81879
[82261]: rust-lang/rust#82261
[82218]: rust-lang/rust#82218
[82216]: rust-lang/rust#82216
[82202]: rust-lang/rust#82202
[81855]: rust-lang/rust#81855
[81766]: rust-lang/rust#81766
[81744]: rust-lang/rust#81744
[81611]: rust-lang/rust#81611
[81479]: rust-lang/rust#81479
[81451]: rust-lang/rust#81451
[81356]: rust-lang/rust#81356
[80962]: rust-lang/rust#80962
[80553]: rust-lang/rust#80553
[80527]: rust-lang/rust#80527
[79519]: rust-lang/rust#79519
[79423]: rust-lang/rust#79423
[79208]: rust-lang/rust#79208
[78429]: rust-lang/rust#78429
[82733]: rust-lang/rust#82733
[82594]: rust-lang/rust#82594
[cargo/9181]: rust-lang/cargo#9181
[`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX
[`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER
[`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION
[`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16
[`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32
[`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked
[`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit
[`Peekable::next_if`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if
[`Peekable::next_if_eq`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if_eq
[`Arguments::as_str`]: https://doc.rust-lang.org/stable/std/fmt/struct.Arguments.html#method.as_str
[`str::split_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_once
[`str::rsplit_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.rsplit_once
[`slice::partition_point`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.partition_point
[`char::len_utf8`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf8
[`char::len_utf16`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf16
[`char::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_uppercase
[`char::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_lowercase
[`char::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.eq_ignore_ascii_case
[`u8::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_uppercase
[`u8::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_lowercase
[`u8::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.eq_ignore_ascii_case
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request May 31, 2021
Pkgsrc changes:
 * Bump bootstrap kit version to 1.51.0.
 * Adjust patches as needed.
 * Update checksum adjustments.
 * Fix syntax error in commands adjusting libserde_derive for Darwin

Upstream changes:

Version 1.52.1 (2021-05-10)
============================

This release disables incremental compilation, unless the user has explicitly
opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable.

This is due to the widespread, and frequently occuring, breakage encountered by
Rust users due to newly enabled incremental verification in 1.52.0. Notably,
Rust users **should** upgrade to 1.52.0 or 1.52.1: the bugs that are detected by
newly added incremental verification are still present in past stable versions,
and are not yet fixed on any channel. These bugs can lead to miscompilation of
Rust binaries.

These problems only affect incremental builds, so release builds with Cargo
should not be affected unless the user has explicitly opted into incremental.
Debug and check builds are affected.

See [84970] for more details.

[84970]: rust-lang/rust#84970

Version 1.52.0 (2021-05-06)
============================

Language
--------
- [Added the `unsafe_op_in_unsafe_fn` lint, which checks whether
  the unsafe code in an `unsafe fn` is wrapped in a `unsafe`
  block.][79208] This lint is allowed by default, and may become
  a warning or hard error in a future edition.

- [You can now cast mutable references to arrays to a pointer of
  the same type as the element.][81479]

Compiler
--------
- [Upgraded the default LLVM to LLVM 12.][81451]

Added tier 3\* support for the following targets.

- [`s390x-unknown-linux-musl`][82166]
- [`riscv32gc-unknown-linux-musl` & `riscv64gc-unknown-linux-musl`][82202]
- [`powerpc-unknown-openbsd`][82733]

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

Libraries
---------
- [`OsString` now implements `Extend` and `FromIterator`.][82121]
- [`cmp::Reverse` now has `#[repr(transparent)]` representation.][81879]
- [`Arc<impl Error>` now implements `error::Error`.][80553]
- [All integer division and remainder operations are now `const`.][80962]

Stabilised APIs
-------------
- [`Arguments::as_str`]
- [`char::MAX`]
- [`char::REPLACEMENT_CHARACTER`]
- [`char::UNICODE_VERSION`]
- [`char::decode_utf16`]
- [`char::from_digit`]
- [`char::from_u32_unchecked`]
- [`char::from_u32`]
- [`slice::partition_point`]
- [`str::rsplit_once`]
- [`str::split_once`]

The following previously stable APIs are now `const`.

- [`char::len_utf8`]
- [`char::len_utf16`]
- [`char::to_ascii_uppercase`]
- [`char::to_ascii_lowercase`]
- [`char::eq_ignore_ascii_case`]
- [`u8::to_ascii_uppercase`]
- [`u8::to_ascii_lowercase`]
- [`u8::eq_ignore_ascii_case`]

Rustdoc
-------
- [Rustdoc lints are now treated as a tool lint, meaning that
  lints are now prefixed with `rustdoc::` (e.g.
  `#[warn(rustdoc::non_autolinks)]`).][80527] Using the old style
  is still allowed, and will become a warning in a future release.
- [Rustdoc now supports argument files.][82261]
- [Rustdoc now generates smart punctuation for documentation.][79423]
- [You can now use "task lists" in Rustdoc Markdown.][81766] E.g.
  ```markdown
  - [x] Complete
  - [ ] Todo
  ```

Misc
----
- [You can now pass multiple filters to tests.][81356] E.g.
  `cargo test -- foo bar` will run all tests that match `foo` and `bar`.
- [Rustup now distributes PDB symbols for the `std` library on Windows,
  allowing you to see `std` symbols when debugging.][82218]

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

- [Check the result cache before the DepGraph when ensuring queries][81855]
- [Try fast_reject::simplify_type in coherence before doing full check][81744]
- [Only store a LocalDefId in some HIR nodes][81611]
- [Store HIR attributes in a side table][79519]

Compatibility Notes
-------------------
- [Cargo build scripts are now forbidden from setting
  `RUSTC_BOOTSTRAP`.][cargo/9181]
- [Removed support for the `x86_64-rumprun-netbsd` target.][82594]
- [Deprecated the `x86_64-sun-solaris` target in favor of
  `x86_64-pc-solaris`.][82216]
- [Rustdoc now only accepts `,`, ` `, and `\t` as delimiters for specifying
  languages in code blocks.][78429]
- [Rustc now catches more cases of `pub_use_of_private_extern_crate`][80763]
- [Changes in how proc macros handle whitespace may lead to panics
  when used with older `proc-macro-hack` versions. A `cargo update` should
  be sufficient to fix this in all cases.][84136]

[84136]: rust-lang/rust#84136
[80763]: rust-lang/rust#80763
[82166]: rust-lang/rust#82166
[82121]: rust-lang/rust#82121
[81879]: rust-lang/rust#81879
[82261]: rust-lang/rust#82261
[82218]: rust-lang/rust#82218
[82216]: rust-lang/rust#82216
[82202]: rust-lang/rust#82202
[81855]: rust-lang/rust#81855
[81766]: rust-lang/rust#81766
[81744]: rust-lang/rust#81744
[81611]: rust-lang/rust#81611
[81479]: rust-lang/rust#81479
[81451]: rust-lang/rust#81451
[81356]: rust-lang/rust#81356
[80962]: rust-lang/rust#80962
[80553]: rust-lang/rust#80553
[80527]: rust-lang/rust#80527
[79519]: rust-lang/rust#79519
[79423]: rust-lang/rust#79423
[79208]: rust-lang/rust#79208
[78429]: rust-lang/rust#78429
[82733]: rust-lang/rust#82733
[82594]: rust-lang/rust#82594
[cargo/9181]: rust-lang/cargo#9181
[`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX
[`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER
[`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION
[`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16
[`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32
[`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked
[`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit
[`Peekable::next_if`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if
[`Peekable::next_if_eq`]: https://doc.rust-lang.org/stable/std/iter/struct.Peekable.html#method.next_if_eq
[`Arguments::as_str`]: https://doc.rust-lang.org/stable/std/fmt/struct.Arguments.html#method.as_str
[`str::split_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_once
[`str::rsplit_once`]: https://doc.rust-lang.org/stable/std/primitive.str.html#method.rsplit_once
[`slice::partition_point`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.partition_point
[`char::len_utf8`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf8
[`char::len_utf16`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.len_utf16
[`char::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_uppercase
[`char::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.to_ascii_lowercase
[`char::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.char.html#method.eq_ignore_ascii_case
[`u8::to_ascii_uppercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_uppercase
[`u8::to_ascii_lowercase`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ascii_lowercase
[`u8::eq_ignore_ascii_case`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.eq_ignore_ascii_case
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