Rust release · Nov 16, 2023

Rust 1.74: what's new, what was stabilized

Short answerRust 1.74 was released on Nov 16, 2023: 1 language stabilization (Stabilize impl_trait_projections); 18 newly stable APIs (core::num::Saturating, impl From<io::Stdout> for std::process::Stdio, impl From<io::Stderr> for std::process::Stdio, impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}, ...); 5 compatibility notes that can affect existing code. Point release: 1.74.1 (Dec 7, 2023).

Nov 16, 2023release date

1language stabilizations

18APIs stabilized

-new edition

← Rust 1.73 All versions Rust 1.75 →

Language features stabilized

Stabilize impl_trait_projections

18 APIs stabilized

core::num::Saturating, impl From<io::Stdout> for std::process::Stdio, impl From<io::Stderr> for std::process::Stdio, impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}, impl From<OwnedFd> for std::process::Child{Stdin, Stdout, Stderr}, std::ffi::OsString::from_encoded_bytes_unchecked, std::ffi::OsString::into_encoded_bytes, std::ffi::OsStr::from_encoded_bytes_unchecked, std::ffi::OsStr::as_encoded_bytes, std::io::Error::other, impl TryFrom<char> for u16, impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T>, impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T>, impl<T, const N: usize> From<[T; N]> for Arc<[T]>, impl<T, const N: usize> From<[T; N]> for Rc<[T]>, core::mem::transmute_copy, str::is_ascii, [u8]::is_ascii

Can it break my build?

The release lists these compatibility notes. Most only affect rare code, but read them before you raise your toolchain in CI:

Raise minimum supported Apple OS versions
make Cell::swap panic if the Cells partially overlap
Reject invalid crate names in --extern
Don't resolve generic impls that may be shadowed by dyn built-in impls
[The new impl From<{&,&mut} [T; N]> for Vec<T> is known to cause some inference failures with overly-generic code.](https://github.com/rust-lang/rust/issues/117054) In those examples using the tui crate, the combination of AsRef<_> and Into<Vec> leaves the middle type ambiguous, and the new impl adds another possibility, so it now requires an explicit type annotation.

Use it

rustup update stable        # get the newest release
rustup install 1.74          # or exactly this one
rustup override set 1.74     # pin a project to it

To require at least this version from users of your crate, set rust-version = "1.74" under [package] in Cargo.toml. Cargo then refuses to build it on older compilers with a clear message, and with resolver 3 (the default on the 2024 edition, Rust 1.85+) it also prefers dependency versions that support it.

Full release notes

Language

Codify that std::mem::Discriminant<T> does not depend on any lifetimes in T
Replace private_in_public lint with private_interfaces and private_bounds per RFC 2145. Read more in RFC 2145.
[Allow explicit #[repr(Rust)]](https://github.com/rust-lang/rust/pull/114201/)
closure field capturing: don't depend on alignment of packed fields
Enable MIR-based drop-tracking for async blocks
Stabilize impl_trait_projections

Compiler

Libraries

Implement From<OwnedFd/Handle> for ChildStdin/out/err
[Implement From<{&,&mut} [T; N]> for Vec<T> where T: Clone](https://github.com/rust-lang/rust/pull/111278/)
impl Step for IP addresses
[Implement From<[T; N]> for Rc<[T]> and Arc<[T]>](https://github.com/rust-lang/rust/pull/114041/)
impl TryFrom<char> for u16
Stabilize io_error_other feature
Stabilize the Saturating type
Stabilize const_transmute_copy

Stabilized APIs

core::num::Saturating
impl From<io::Stdout> for std::process::Stdio
impl From<io::Stderr> for std::process::Stdio
impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}
impl From<OwnedFd> for std::process::Child{Stdin, Stdout, Stderr}
std::ffi::OsString::from_encoded_bytes_unchecked
std::ffi::OsString::into_encoded_bytes
std::ffi::OsStr::from_encoded_bytes_unchecked
std::ffi::OsStr::as_encoded_bytes
std::io::Error::other
impl TryFrom<char> for u16
[impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T>](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#impl-From%3C%26%5BT;+N%5D%3E-for-Vec%3CT,+Global%3E)
[impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T>](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#impl-From%3C%26mut+%5BT;+N%5D%3E-for-Vec%3CT,+Global%3E)
[impl<T, const N: usize> From<[T; N]> for Arc<[T]>](https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#impl-From%3C%5BT;+N%5D%3E-for-Arc%3C%5BT%5D,+Global%3E)
[impl<T, const N: usize> From<[T; N]> for Rc<[T]>](https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#impl-From%3C%5BT;+N%5D%3E-for-Rc%3C%5BT%5D,+Global%3E)

These APIs are now stable in const contexts:

core::mem::transmute_copy
str::is_ascii
[[u8]::is_ascii](https://doc.rust-lang.org/beta/std/primitive.slice.html#method.is_ascii)

Cargo

[In Cargo.toml, stabilize [lints]](https://github.com/rust-lang/cargo/pull/12648/)
Stabilize credential-process and registry-auth
Stabilize --keep-going build flag
Add styling to --help output
For cargo clean, add --dry-run flag and summary line at the end
For cargo update, make --package more convenient by being positional
For cargo update, clarify meaning of --aggressive as --recursive
Add '-n' as an alias for --dry-run
Allow version-prefixes in pkgid's (e.g. --package flags) to resolve ambiguities
In .cargo/config.toml, merge lists in precedence order
Add support for target.'cfg(..)'.linker

Rustdoc

Compatibility Notes

Raise minimum supported Apple OS versions
make Cell::swap panic if the Cells partially overlap
Reject invalid crate names in --extern
Don't resolve generic impls that may be shadowed by dyn built-in impls
[The new impl From<{&,&mut} [T; N]> for Vec<T> is known to cause some inference failures with overly-generic code.](https://github.com/rust-lang/rust/issues/117054) In those examples using the tui crate, the combination of AsRef<_> and Into<Vec> leaves the middle type ambiguous, and the new impl adds another possibility, so it now requires an explicit type annotation.

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.

None this cycle.

1.74.1 (Dec 7, 2023)

Release notes from the Rust project's RELEASES.md (MIT or Apache-2.0); summaries above are ours.