Rust 1.57.0

Language

--------

- [Macro attributes may follow #[derive] and will see the original (pre-cfg) input.][87220]

- [Accept curly-brace macros in expressions, like m!{ .. }.method() and m!{ .. }?.][88690]

- [Allow panicking in constant evaluation.][89508]

- [Ignore derived Clone and Debug implementations during dead code analysis.][85200]

Compiler

--------

- [Create more accurate debuginfo for vtables.][89597]

- [Add armv6k-nintendo-3ds at Tier 3\*.][88529]

- [Add armv7-unknown-linux-uclibceabihf at Tier 3\*.][88952]

- [Add m68k-unknown-linux-gnu at Tier 3\*.][88321]

- [Add SOLID targets at Tier 3\*:][86191] aarch64-kmc-solid_asp3, armv7a-kmc-solid_asp3-eabi, armv7a-kmc-solid_asp3-eabihf

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

information on Rust's tiered platform support.

Libraries

---------

- [Avoid allocations and copying in Vec::leak][89337]

- [Add #[repr(i8)] to Ordering][89507]

- [Optimize File::read_to_end and read_to_string][89582]

- [Update to Unicode 14.0][89614]

- [Many more functions are marked #[must_use]][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.

Stabilised APIs

---------------

- [[T; N]::as_mut_slice][array::as_mut_slice]

- [[T; N]::as_slice][array::as_slice]

- [collections::TryReserveError]

- [HashMap::try_reserve]

- [HashSet::try_reserve]

- [String::try_reserve]

- [String::try_reserve_exact]

- [Vec::try_reserve]

- [Vec::try_reserve_exact]

- [VecDeque::try_reserve]

- [VecDeque::try_reserve_exact]

- [Iterator::map_while]

- [iter::MapWhile]

- [proc_macro::is_available]

- [Command::get_program]

- [Command::get_args]

- [Command::get_envs]

- [Command::get_current_dir]

- [CommandArgs]

- [CommandEnvs]

These APIs are now usable in const contexts:

- [hint::unreachable_unchecked]

Cargo

-----

- [Stabilize custom profiles][cargo/9943]

Compatibility notes

-------------------

- [Ignore derived Clone and Debug implementations during dead code analysis.][85200]

This will break some builds that set #![deny(dead_code)].

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.

- [Added an experimental backend for codegen with libgccjit.][87260]

[85200]: https://github.com/rust-lang/rust/pull/85200/

[86191]: https://github.com/rust-lang/rust/pull/86191/

[87220]: https://github.com/rust-lang/rust/pull/87220/

[87260]: https://github.com/rust-lang/rust/pull/87260/

[88321]: https://github.com/rust-lang/rust/pull/88321/

[88529]: https://github.com/rust-lang/rust/pull/88529/

[88690]: https://github.com/rust-lang/rust/pull/88690/

[88952]: https://github.com/rust-lang/rust/pull/88952/

[89337]: https://github.com/rust-lang/rust/pull/89337/

[89507]: https://github.com/rust-lang/rust/pull/89507/

[89508]: https://github.com/rust-lang/rust/pull/89508/

[89582]: https://github.com/rust-lang/rust/pull/89582/

[89597]: https://github.com/rust-lang/rust/pull/89597/

[89614]: https://github.com/rust-lang/rust/pull/89614/

[89692]: https://github.com/rust-lang/rust/issues/89692/

[cargo/9943]: https://github.com/rust-lang/cargo/pull/9943/

[array::as_mut_slice]: https://doc.rust-lang.org/std/primitive.array.html#method.as_mut_slice

[array::as_slice]: https://doc.rust-lang.org/std/primitive.array.html#method.as_slice

[collections::TryReserveError]: https://doc.rust-lang.org/std/collections/struct.TryReserveError.html

[HashMap::try_reserve]: https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.try_reserve

[HashSet::try_reserve]: https://doc.rust-lang.org/std/collections/hash_set/struct.HashSet.html#method.try_reserve

[String::try_reserve]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve

[String::try_reserve_exact]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve_exact

[Vec::try_reserve]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve

[Vec::try_reserve_exact]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve_exact

[VecDeque::try_reserve]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve

[VecDeque::try_reserve_exact]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve_exact

[Iterator::map_while]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map_while

[iter::MapWhile]: https://doc.rust-lang.org/std/iter/struct.MapWhile.html

[proc_macro::is_available]: https://doc.rust-lang.org/proc_macro/fn.is_available.html

[Command::get_program]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_program

[Command::get_args]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_args

[Command::get_envs]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_envs

[Command::get_current_dir]: https://doc.rust-lang.org/std/process/struct.Command.html#method.get_current_dir

[CommandArgs]: https://doc.rust-lang.org/std/process/struct.CommandArgs.html

[CommandEnvs]: https://doc.rust-lang.org/std/process/struct.CommandEnvs.html