Make `-O` mean `OptLevel::Aggressive`

Implementation of this MCP: rust-lang/compiler-team#828, changing the meaning of `-O` from `-Copt-level=2` to `-Copt-level=3`.

This also renames `OptLevel::Default` to `OptLevel::More`, as `Default` no longer makes sense.

Rollup merge of rust-lang#135439 - clubby789:O3, r=Noratrieb

Make `-O` mean `OptLevel::Aggressive`

Implementation of this MCP: rust-lang/compiler-team#828, changing the meaning of `-O` from `-Copt-level=2` to `-Copt-level=3`.

This also renames `OptLevel::Default` to `OptLevel::More`, as `Default` no longer makes sense.

Upstream changes relative to 1.85.1:

Version 1.86.0 (2025-04-03)
==========================

Language
--------
- [Stabilize upcasting trait objects to supertraits.]
  (rust-lang/rust#134367)
- [Allow safe functions to be marked with the `#[target_feature]` attribute.]
  (rust-lang/rust#134090)
- [The `missing_abi` lint now warns-by-default.]
  (rust-lang/rust#132397)
- Rust now lints about double negations, to catch cases that might
  have intended to be a prefix decrement operator (`--x`) as written
  in other languages. This was previously a clippy lint,
  `clippy::double_neg`, and is [now available directly in Rust as
  `double_negations`.]
  (rust-lang/rust#126604)
- [More pointers are now detected as definitely not-null based on
  their alignment in const eval.]
  (rust-lang/rust#133700)
- [Empty `repr()` attribute applied to invalid items are now
  correctly rejected.]
  (rust-lang/rust#133925)
- [Inner attributes `#![test]` and `#![rustfmt::skip]` are no longer
  accepted in more places than intended.]
  (rust-lang/rust#134276)

Compiler
--------
- [Debug-assert that raw pointers are non-null on access.]
  (rust-lang/rust#134424)
- [Change `-O` to mean `-C opt-level=3` instead of `-C opt-level=2`
  to match Cargo's defaults.]
  (rust-lang/rust#135439)
- [Fix emission of `overflowing_literals` under certain macro environments.]
  (rust-lang/rust#136393)

Platform Support
----------------
- [Replace `i686-unknown-redox` target with `i586-unknown-redox`.]
  (rust-lang/rust#136698)
- [Increase baseline CPU of `i686-unknown-hurd-gnu` to Pentium 4.]
  (rust-lang/rust#136700)
- New tier 3 targets:
  - [`{aarch64-unknown,x86_64-pc}-nto-qnx710_iosock`]
    (rust-lang/rust#133631).
    For supporting Neutrino QNX 7.1 with `io-socket` network stack.
  - [`{aarch64-unknown,x86_64-pc}-nto-qnx800`]
    (rust-lang/rust#133631).
    For supporting Neutrino QNX 8.0 (`no_std`-only).
  - [`{x86_64,i686}-win7-windows-gnu`]
    (rust-lang/rust#134609).
    Intended for backwards compatibility with Windows 7.
    `{x86_64,i686}-win7-windows-msvc` are the Windows MSVC counterparts
    that already exist as Tier 3 targets.
  - [`amdgcn-amd-amdhsa`](rust-lang/rust#134740).
  - [`x86_64-pc-cygwin`](rust-lang/rust#134999).
  - [`{mips,mipsel}-mti-none-elf`]
    (rust-lang/rust#135074).
    Initial bare-metal support.
  - [`m68k-unknown-none-elf`](rust-lang/rust#135085).
  - [`armv7a-nuttx-{eabi,eabihf}`, `aarch64-unknown-nuttx`, and
    `thumbv7a-nuttx-{eabi,eabihf}`]
    (rust-lang/rust#135757).

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

Libraries
---------
- The type of `FromBytesWithNulError` in `CStr::from_bytes_with_nul(bytes:
  &[u8]) -> Result<&Self, FromBytesWithNulError>` was [changed from
  an opaque struct to an enum]
  (rust-lang/rust#134143), allowing users
  to examine why the conversion failed.
- [Remove `RustcDecodable` and `RustcEncodable`.]
  (rust-lang/rust#134272)
- [Deprecate libtest's `--logfile` option.]
  (rust-lang/rust#134283)
- [On recent versions of Windows, `std::fs::remove_file` will now
  remove read-only files.]
  (rust-lang/rust#134679)

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

- [`{float}::next_down`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_down)
- [`{float}::next_up`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_up)
- [`<[_]>::get_disjoint_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_mut)
- [`<[_]>::get_disjoint_unchecked_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_unchecked_mut)
- [`slice::GetDisjointMutError`]
  (https://doc.rust-lang.org/stable/std/slice/enum.GetDisjointMutError.html)
- [`HashMap::get_disjoint_mut`]
  (https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_mut)
- [`HashMap::get_disjoint_unchecked_mut`]
  (https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_unchecked_mut)
- [`NonZero::count_ones`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.count_ones)
- [`Vec::pop_if`]
  (https://doc.rust-lang.org/std/vec/struct.Vec.html#method.pop_if)
- [`sync::Once::wait`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait)
- [`sync::Once::wait_force`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait_force)
- [`sync::OnceLock::wait`]
  (https://doc.rust-lang.org/stable/std/sync/struct.OnceLock.html#method.wait)

These APIs are now stable in const contexts:

- [`hint::black_box`]
  (https://doc.rust-lang.org/stable/std/hint/fn.black_box.html)
- [`io::Cursor::get_mut`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_mut)
- [`io::Cursor::set_position`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.set_position)
- [`str::is_char_boundary`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.is_char_boundary)
- [`str::split_at`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at)
- [`str::split_at_checked`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_checked)
- [`str::split_at_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut)
- [`str::split_at_mut_checked`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut_checked)

Cargo
-----
- [When merging, replace rather than combine configuration keys
  that refer to a program path and its arguments.]
  (rust-lang/cargo#15066)
- [Error if both `--package` and `--workspace` are passed but the
  requested package is missing.]
  (rust-lang/cargo#15071) This was previously
  silently ignored, which was considered a bug since missing packages
  should be reported.
- [Deprecate the token argument in `cargo login` to avoid shell history leaks.]
  (rust-lang/cargo#15057)
- [Simplify the implementation of `SourceID` comparisons.]
  (rust-lang/cargo#14980) This may
  potentially change behavior if the canonicalized URL compares
  differently in alternative registries.

Rustdoc
-----
- [Add a sans-serif font setting.]
  (rust-lang/rust#133636)

Compatibility Notes
-------------------
- [The `wasm_c_abi` future compatibility warning is now a hard error.]
  (rust-lang/rust#133951)
  Users of `wasm-bindgen` should upgrade to at least version 0.2.89,
  otherwise compilation will fail.
- [Remove long-deprecated no-op attributes `#![no_start]` and `#![crate_id]`.]
  (rust-lang/rust#134300)
- [The future incompatibility lint `cenum_impl_drop_cast` has been
  made into a hard error.]
  (rust-lang/rust#135964) This means it is
  now an error to cast a field-less enum to an integer if the enum
  implements `Drop`.
- [SSE2 is now required for "i686" 32-bit x86 hard-float targets;
  disabling it causes a warning that will become a hard error
  eventually.]
  (rust-lang/rust#137037) To compile for
  pre-SSE2 32-bit x86, use a "i586" target instead.

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

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Build the rustc on AArch64 Linux with ThinLTO + PGO.]
  (rust-lang/rust#133807)
  The ARM 64-bit compiler (AArch64) on Linux is now optimized with
  ThinLTO and PGO, similar to the optimizations we have already
  performed for the x86-64 compiler on Linux. This should make it
  up to 30% faster.

This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [rust](https://github.com/rust-lang/rust) | minor | `1.85.1` -> `1.86.0` |

MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot).

**Proposed changes to behavior should be submitted there as MRs.**

---

### Release Notes

<details>
<summary>rust-lang/rust (rust)</summary>

### [`v1.86.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1860-2025-04-03)

[Compare Source](rust-lang/rust@1.85.1...1.86.0)

\==========================

<a id="1.86.0-Language"></a>

## Language

-   [Stabilize upcasting trait objects to supertraits.](rust-lang/rust#134367)
-   [Allow safe functions to be marked with the `#[target_feature]` attribute.](rust-lang/rust#134090)
-   [The `missing_abi` lint now warns-by-default.](rust-lang/rust#132397)
-   Rust now lints about double negations, to catch cases that might have intended to be a prefix decrement operator (`--x`) as written in other languages. This was previously a clippy lint, `clippy::double_neg`, and is [now available directly in Rust as `double_negations`.](rust-lang/rust#126604)
-   [More pointers are now detected as definitely not-null based on their alignment in const eval.](rust-lang/rust#133700)
-   [Empty `repr()` attribute applied to invalid items are now correctly rejected.](rust-lang/rust#133925)
-   [Inner attributes `#![test]` and `#![rustfmt::skip]` are no longer accepted in more places than intended.](rust-lang/rust#134276)

<a id="1.86.0-Compiler"></a>

## Compiler

-   [Debug-assert that raw pointers are non-null on access.](rust-lang/rust#134424)
-   [Change `-O` to mean `-C opt-level=3` instead of `-C opt-level=2` to match Cargo's defaults.](rust-lang/rust#135439)
-   [Fix emission of `overflowing_literals` under certain macro environments.](rust-lang/rust#136393)

<a id="1.86.0-Platform-Support"></a>

## Platform Support

-   [Replace `i686-unknown-redox` target with `i586-unknown-redox`.](rust-lang/rust#136698)
-   [Increase baseline CPU of `i686-unknown-hurd-gnu` to Pentium 4.](rust-lang/rust#136700)
-   New tier 3 targets:
    -   [`{aarch64-unknown,x86_64-pc}-nto-qnx710_iosock`](rust-lang/rust#133631).
        For supporting Neutrino QNX 7.1 with `io-socket` network stack.
    -   [`{aarch64-unknown,x86_64-pc}-nto-qnx800`](rust-lang/rust#133631).
        For supporting Neutrino QNX 8.0 (`no_std`-only).
    -   [`{x86_64,i686}-win7-windows-gnu`](rust-lang/rust#134609).
        Intended for backwards compatibility with Windows 7. `{x86_64,i686}-win7-windows-msvc` are the Windows MSVC counterparts that already exist as Tier 3 targets.
    -   [`amdgcn-amd-amdhsa`](rust-lang/rust#134740).
    -   [`x86_64-pc-cygwin`](rust-lang/rust#134999).
    -   [`{mips,mipsel}-mti-none-elf`](rust-lang/rust#135074).
        Initial bare-metal support.
    -   [`m68k-unknown-none-elf`](rust-lang/rust#135085).
    -   [`armv7a-nuttx-{eabi,eabihf}`, `aarch64-unknown-nuttx`, and `thumbv7a-nuttx-{eabi,eabihf}`](rust-lang/rust#135757).

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

<a id="1.86.0-Libraries"></a>

## Libraries

-   The type of `FromBytesWithNulError` in `CStr::from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError>` was [changed from an opaque struct to an enum](rust-lang/rust#134143), allowing users to examine why the conversion failed.
-   [Remove `RustcDecodable` and `RustcEncodable`.](rust-lang/rust#134272)
-   [Deprecate libtest's `--logfile` option.](rust-lang/rust#134283)
-   [On recent versions of Windows, `std::fs::remove_file` will now remove read-only files.](rust-lang/rust#134679)

<a id="1.86.0-Stabilized-APIs"></a>

## Stabilized APIs

-   [`{float}::next_down`](https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_down)
-   [`{float}::next_up`](https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_up)
-   [`<[_]>::get_disjoint_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_mut)
-   [`<[_]>::get_disjoint_unchecked_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_unchecked_mut)
-   [`slice::GetDisjointMutError`](https://doc.rust-lang.org/stable/std/slice/enum.GetDisjointMutError.html)
-   [`HashMap::get_disjoint_mut`](https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_mut)
-   [`HashMap::get_disjoint_unchecked_mut`](https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_unchecked_mut)
-   [`NonZero::count_ones`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.count_ones)
-   [`Vec::pop_if`](https://doc.rust-lang.org/std/vec/struct.Vec.html#method.pop_if)
-   [`sync::Once::wait`](https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait)
-   [`sync::Once::wait_force`](https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait_force)
-   [`sync::OnceLock::wait`](https://doc.rust-lang.org/stable/std/sync/struct.OnceLock.html#method.wait)

These APIs are now stable in const contexts:

-   [`hint::black_box`](https://doc.rust-lang.org/stable/std/hint/fn.black_box.html)
-   [`io::Cursor::get_mut`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_mut)
-   [`io::Cursor::set_position`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.set_position)
-   [`str::is_char_boundary`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.is_char_boundary)
-   [`str::split_at`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at)
-   [`str::split_at_checked`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_checked)
-   [`str::split_at_mut`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut)
-   [`str::split_at_mut_checked`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut_checked)

<a id="1.86.0-Cargo"></a>

## Cargo

-   [When merging, replace rather than combine configuration keys that refer to a program path and its arguments.](rust-lang/cargo#15066)
-   [Error if both `--package` and `--workspace` are passed but the requested package is missing.](rust-lang/cargo#15071) This was previously silently ignored, which was considered a bug since missing packages should be reported.
-   [Deprecate the token argument in `cargo login` to avoid shell history leaks.](rust-lang/cargo#15057)
-   [Simplify the implementation of `SourceID` comparisons.](rust-lang/cargo#14980) This may potentially change behavior if the canonicalized URL compares differently in alternative registries.

<a id="1.86.0-Rustdoc"></a>

## Rustdoc

-   [Add a sans-serif font setting.](rust-lang/rust#133636)

<a id="1.86.0-Compatibility-Notes"></a>

## Compatibility Notes

-   [The `wasm_c_abi` future compatibility warning is now a hard error.](rust-lang/rust#133951)
    Users of `wasm-bindgen` should upgrade to at least version 0.2.89, otherwise compilation will fail.
-   [Remove long-deprecated no-op attributes `#![no_start]` and `#![crate_id]`.](rust-lang/rust#134300)
-   [The future incompatibility lint `cenum_impl_drop_cast` has been made into a hard error.](rust-lang/rust#135964) This means it is now an error to cast a field-less enum to an integer if the enum implements `Drop`.
-   [SSE2 is now required for "i686" 32-bit x86 hard-float targets; disabling it causes a warning that will become a hard error eventually.](rust-lang/rust#137037)
    To compile for pre-SSE2 32-bit x86, use a "i586" target instead.

<a id="1.86.0-Internal-Changes"></a>

## Internal Changes

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

-   [Build the rustc on AArch64 Linux with ThinLTO + PGO.](rust-lang/rust#133807)
    The ARM 64-bit compiler (AArch64) on Linux is now optimized with ThinLTO and PGO, similar to the optimizations we have already performed for the x86-64 compiler on Linux. This should make it up to 30% faster.

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this MR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this MR, check this box

---

This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MC4xMS4yIiwidXBkYXRlZEluVmVyIjoiNDAuMTEuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiUmVub3ZhdGUgQm90Il19-->

Pkgsrc changes:
 * Drop support for building now old 1.76.0 rust natively on 32-bit
   NetBSD arm ports, pushing those to use the rust-bin variant instead.
 * Use of newer GCC on NetBSD/powerpc turned out to not be required,
   given that your kernel and user-land is new enough.  >= 10.0 release?
 * Checksum updates.

Upstream changes:

Version 1.86.0 (2025-04-03)
==========================

Language
--------
- [Stabilize upcasting trait objects to supertraits.]
  (rust-lang/rust#134367)
- [Allow safe functions to be marked with the `#[target_feature]` attribute.]
  (rust-lang/rust#134090)
- [The `missing_abi` lint now warns-by-default.]
  (rust-lang/rust#132397)
- Rust now lints about double negations, to catch cases that might
  have intended to be a prefix decrement operator (`--x`) as written
  in other languages. This was previously a clippy lint,
  `clippy::double_neg`, and is [now available directly in Rust as
  `double_negations`.]
  (rust-lang/rust#126604)
- [More pointers are now detected as definitely not-null based on
  their alignment in const eval.]
  (rust-lang/rust#133700)
- [Empty `repr()` attribute applied to invalid items are now
  correctly rejected.]
  (rust-lang/rust#133925)
- [Inner attributes `#![test]` and `#![rustfmt::skip]` are no longer
  accepted in more places than intended.]
  (rust-lang/rust#134276)

Compiler
--------
- [Debug-assert that raw pointers are non-null on access.]
  (rust-lang/rust#134424)
- [Change `-O` to mean `-C opt-level=3` instead of `-C opt-level=2`
  to match Cargo's defaults.]
  (rust-lang/rust#135439)
- [Fix emission of `overflowing_literals` under certain macro environments.]
  (rust-lang/rust#136393)

Platform Support
----------------
- [Replace `i686-unknown-redox` target with `i586-unknown-redox`.]
  (rust-lang/rust#136698)
- [Increase baseline CPU of `i686-unknown-hurd-gnu` to Pentium 4.]
  (rust-lang/rust#136700)
- New tier 3 targets:
  - [`{aarch64-unknown,x86_64-pc}-nto-qnx710_iosock`]
    (rust-lang/rust#133631).
    For supporting Neutrino QNX 7.1 with `io-socket` network stack.
  - [`{aarch64-unknown,x86_64-pc}-nto-qnx800`]
    (rust-lang/rust#133631).
    For supporting Neutrino QNX 8.0 (`no_std`-only).
  - [`{x86_64,i686}-win7-windows-gnu`]
    (rust-lang/rust#134609).
    Intended for backwards compatibility with Windows 7.
    `{x86_64,i686}-win7-windows-msvc` are the Windows MSVC counterparts
    that already exist as Tier 3 targets.
  - [`amdgcn-amd-amdhsa`](rust-lang/rust#134740).
  - [`x86_64-pc-cygwin`](rust-lang/rust#134999).
  - [`{mips,mipsel}-mti-none-elf`]
    (rust-lang/rust#135074).
    Initial bare-metal support.
  - [`m68k-unknown-none-elf`](rust-lang/rust#135085).
  - [`armv7a-nuttx-{eabi,eabihf}`, `aarch64-unknown-nuttx`, and
    `thumbv7a-nuttx-{eabi,eabihf}`]
    (rust-lang/rust#135757).

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

Libraries
---------
- The type of `FromBytesWithNulError` in `CStr::from_bytes_with_nul(bytes:
  &[u8]) -> Result<&Self, FromBytesWithNulError>` was [changed from
  an opaque struct to an enum]
  (rust-lang/rust#134143), allowing users
  to examine why the conversion failed.
- [Remove `RustcDecodable` and `RustcEncodable`.]
  (rust-lang/rust#134272)
- [Deprecate libtest's `--logfile` option.]
  (rust-lang/rust#134283)
- [On recent versions of Windows, `std::fs::remove_file` will now
  remove read-only files.]
  (rust-lang/rust#134679)

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

- [`{float}::next_down`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_down)
- [`{float}::next_up`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.next_up)
- [`<[_]>::get_disjoint_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_mut)
- [`<[_]>::get_disjoint_unchecked_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.get_disjoint_unchecked_mut)
- [`slice::GetDisjointMutError`]
  (https://doc.rust-lang.org/stable/std/slice/enum.GetDisjointMutError.html)
- [`HashMap::get_disjoint_mut`]
  (https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_mut)
- [`HashMap::get_disjoint_unchecked_mut`]
  (https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.get_disjoint_unchecked_mut)
- [`NonZero::count_ones`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.count_ones)
- [`Vec::pop_if`]
  (https://doc.rust-lang.org/std/vec/struct.Vec.html#method.pop_if)
- [`sync::Once::wait`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait)
- [`sync::Once::wait_force`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Once.html#method.wait_force)
- [`sync::OnceLock::wait`]
  (https://doc.rust-lang.org/stable/std/sync/struct.OnceLock.html#method.wait)

These APIs are now stable in const contexts:

- [`hint::black_box`]
  (https://doc.rust-lang.org/stable/std/hint/fn.black_box.html)
- [`io::Cursor::get_mut`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_mut)
- [`io::Cursor::set_position`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.set_position)
- [`str::is_char_boundary`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.is_char_boundary)
- [`str::split_at`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at)
- [`str::split_at_checked`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_checked)
- [`str::split_at_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut)
- [`str::split_at_mut_checked`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#method.split_at_mut_checked)

Cargo
-----
- [When merging, replace rather than combine configuration keys
  that refer to a program path and its arguments.]
  (rust-lang/cargo#15066)
- [Error if both `--package` and `--workspace` are passed but the
  requested package is missing.]
  (rust-lang/cargo#15071) This was previously
  silently ignored, which was considered a bug since missing packages
  should be reported.
- [Deprecate the token argument in `cargo login` to avoid shell history leaks.]
  (rust-lang/cargo#15057)
- [Simplify the implementation of `SourceID` comparisons.]
  (rust-lang/cargo#14980) This may
  potentially change behavior if the canonicalized URL compares
  differently in alternative registries.

Rustdoc
-----
- [Add a sans-serif font setting.]
  (rust-lang/rust#133636)

Compatibility Notes
-------------------
- [The `wasm_c_abi` future compatibility warning is now a hard error.]
  (rust-lang/rust#133951)
  Users of `wasm-bindgen` should upgrade to at least version 0.2.89,
  otherwise compilation will fail.
- [Remove long-deprecated no-op attributes `#![no_start]` and `#![crate_id]`.]
  (rust-lang/rust#134300)
- [The future incompatibility lint `cenum_impl_drop_cast` has been
  made into a hard error.]
  (rust-lang/rust#135964) This means it is
  now an error to cast a field-less enum to an integer if the enum
  implements `Drop`.
- [SSE2 is now required for "i686" 32-bit x86 hard-float targets;
  disabling it causes a warning that will become a hard error
  eventually.]
  (rust-lang/rust#137037) To compile for
  pre-SSE2 32-bit x86, use a "i586" target instead.

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

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Build the rustc on AArch64 Linux with ThinLTO + PGO.]
  (rust-lang/rust#133807)
  The ARM 64-bit compiler (AArch64) on Linux is now optimized with
  ThinLTO and PGO, similar to the optimizations we have already
  performed for the x86-64 compiler on Linux. This should make it
  up to 30% faster.