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)]
• closure field capturing: don't depend on alignment of packed fields
• Enable MIR-based drop-tracking for async blocks
• Stabilize impl_trait_projections

Compiler

• stabilize combining +bundle and +whole-archive link modifiers
• Stabilize PATH option for --print KIND=PATH
• Enable ASAN/LSAN/TSAN for *-apple-ios-macabi
• Promote loongarch64-unknown-none* to Tier 2
• Add i686-pc-windows-gnullvm as a tier 3 target

Libraries

• Implement From<OwnedFd/Handle> for ChildStdin/out/err
• Implement From<{&,&mut} [T; N]> for Vec<T> where T: Clone
• impl Step for IP addresses
• Implement From<[T; N]> for Rc<[T]> and Arc<[T]>
• 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>
• 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]>

These APIs are now stable in const contexts:

• core::mem::transmute_copy
• str::is_ascii
• [u8]::is_ascii

Cargo

• fix: Set MSRV for internal packages
• config: merge lists in precedence order
• fix(update): Clarify meaning of --aggressive as --recursive
• fix(update): Make -p more convenient by being positional
• feat(help): Add styling to help output
• feat(pkgid): Allow incomplete versions when unambigious
• feat: stabilize credential-process and registry-auth
• feat(cli): Add '-n' to dry-run
• Add support for target.'cfg(..)'.linker
• Stabilize --keep-going
• feat: Stabilize lints

Rustdoc

• Add warning block support in rustdoc
• Accept additional user-defined syntax classes in fenced code blocks
• rustdoc-search: add support for type parameters
• rustdoc: show inner enum and struct in type definition for concrete type

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. 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.