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• Revert stripping debuginfo by default for Windows This fixes a regression in 1.77 by reverting to the previous default. Platforms other than Windows are not affected.
• Internal: Fix heading anchor rendering in doc pages

Language

• Reveal opaque types within the defining body for exhaustiveness checking.
• Stabilize C-string literals.
• Stabilize THIR unsafeck.
• Add lint static_mut_refs to warn on references to mutable statics.
• Support async recursive calls (as long as they have indirection).
• Undeprecate lint unstable_features and make use of it in the compiler.
• Make inductive cycles in coherence ambiguous always.
• Get rid of type-driven traversal in const-eval interning, only as a future compatiblity lint for now.
• Deny braced macro invocations in let-else.

Compiler

• Include lint soft_unstable in future breakage reports.
• Make i128 and u128 16-byte aligned on x86-based targets.
• Use --verbose in diagnostic output.
• Improve spacing between printed tokens.
• Merge the unused_tuple_struct_fields lint into dead_code.
• Error on incorrect implied bounds in well-formedness check, with a temporary exception for Bevy.
• Fix coverage instrumentation/reports for non-ASCII source code.
• Fix fn/const items implied bounds and well-formedness check.
• Promote riscv32{im|imafc}-unknown-none-elf targets to tier 2.
• Add several new tier 3 targets:
  • aarch64-unknown-illumos
  • hexagon-unknown-none-elf
  • riscv32imafc-esp-espidf
  • riscv32im-risc0-zkvm-elf

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Implement From<&[T; N]> for Cow<[T]>.
• Remove special-case handling of vec.split_off(0).

Stabilized APIs

• array::each_ref
• array::each_mut
• core::net
• f32::round_ties_even
• f64::round_ties_even
• mem::offset_of!
• slice::first_chunk
• slice::first_chunk_mut
• slice::split_first_chunk
• slice::split_first_chunk_mut
• slice::last_chunk
• slice::last_chunk_mut
• slice::split_last_chunk
• slice::split_last_chunk_mut
• slice::chunk_by
• slice::chunk_by_mut
• Bound::map
• File::create_new
• Mutex::clear_poison
• RwLock::clear_poison

Cargo

• Extend the build directive syntax with cargo::.
• Stabilize metadata id format as PackageIDSpec.
• Pull out cargo-util-schemas as a crate.
• Strip all debuginfo when debuginfo is not requested.
• Inherit jobserver from env for all kinds of runners.
• Deprecate rustc plugin support in cargo.

Rustdoc

• Allows links in markdown headings.
• Search for tuples and unit by type with ().
• Clean up the source sidebar's hide button.
• Prevent JS injection from localStorage.

Misc

• Recommend version-sorting for all sorting in style guide.

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.

• Add more weirdness to weird-exprs.rs.

Language

• Document Rust ABI compatibility between various types
• Also: guarantee that char and u32 are ABI-compatible
• Add lint ambiguous_wide_pointer_comparisons that supersedes clippy::vtable_address_comparisons

Compiler

• Lint pinned #[must_use] pointers (in particular, Box<T> where T is #[must_use]) in unused_must_use.
• Soundness fix: fix computing the offset of an unsized field in a packed struct
• Soundness fix: fix dynamic size/align computation logic for packed types with dyn Trait tail
• Add $message_type field to distinguish json diagnostic outputs
• Enable Rust to use the EHCont security feature of Windows
• Add tier 3 {x86_64,i686}-win7-windows-msvc targets
• Add tier 3 aarch64-apple-watchos target
• Add tier 3 arm64e-apple-ios & arm64e-apple-darwin targets

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Add a column number to dbg!()
• Add std::hash::{DefaultHasher, RandomState} exports
• Fix rounding issue with exponents in fmt
• Add T: ?Sized to RwLockReadGuard and RwLockWriteGuard's Debug impls.
• Windows: Allow File::create to work on hidden files

Stabilized APIs

• Arc::unwrap_or_clone
• Rc::unwrap_or_clone
• Result::inspect
• Result::inspect_err
• Option::inspect
• type_name_of_val
• std::hash::{DefaultHasher, RandomState} These were previously available only through std::collections::hash_map.
• ptr::{from_ref, from_mut}
• ptr::addr_eq

Cargo

See Cargo release notes.

Rustdoc

• Don't merge cfg and doc(cfg) attributes for re-exports
• rustdoc: allow resizing the sidebar / hiding the top bar
• rustdoc-search: add support for traits and associated types
• rustdoc: Add highlighting for comments in items declaration

Compatibility Notes

• Add allow-by-default lint for unit bindings This is expected to be upgraded to a warning by default in a future Rust release. Some macros emit bindings with type () with user-provided spans, which means that this lint will warn for user code.
• Remove x86_64-sun-solaris target.
• Remove asmjs-unknown-emscripten target
• Report errors in jobserver inherited through environment variables This may warn on benign problems too.
• Update the minimum external LLVM to 16.
• Improve print_tts This change can break some naive manual parsing of token trees in proc macro code which expect a particular structure after .to_string(), rather than just arbitrary Rust code.
• Make IMPLIED_BOUNDS_ENTAILMENT into a hard error from a lint
• Vec's allocation behavior was changed when collecting some iterators Allocation behavior is currently not specified, nevertheless changes can be surprising. See impl FromIterator for Vec for more details.
• Properly reject default on free const items

Language

• Stabilize async fn and return-position impl Trait in traits.
• Allow function pointer signatures containing &mut T in const contexts.
• Match usize/isize exhaustively with half-open ranges.
• Guarantee that char has the same size and alignment as u32.
• Document that the null pointer has the 0 address.
• Allow partially moved values in match.
• Add notes about non-compliant FP behavior on 32bit x86 targets.
• Stabilize ratified RISC-V target features.

Compiler

• Rework negative coherence to properly consider impls that only partly overlap.
• Bump COINDUCTIVE_OVERLAP_IN_COHERENCE to deny, and warn in dependencies.
• Consider alias bounds when computing liveness in NLL.
• Add the V (vector) extension to the riscv64-linux-android target spec.
• Automatically enable cross-crate inlining for small functions
• Add several new tier 3 targets:
  • csky-unknown-linux-gnuabiv2hf
  • i586-unknown-netbsd
  • mipsel-unknown-netbsd

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Override Waker::clone_from to avoid cloning Wakers unnecessarily.
• Implement BufRead for VecDeque<u8>.
• Implement FusedIterator for DecodeUtf16 when the inner iterator does.
• Implement Not, Bit{And,Or}{,Assign} for IP addresses.
• Implement Default for ExitCode.
• Guarantee representation of None in NPO
• Document when atomic loads are guaranteed read-only.
• Broaden the consequences of recursive TLS initialization.
• Windows: Support sub-millisecond sleep.
• Fix generic bound of str::SplitInclusive's DoubleEndedIterator impl
• Fix exit status / wait status on non-Unix cfg(unix) platforms.

Stabilized APIs

• Atomic*::from_ptr
• FileTimes
• FileTimesExt
• File::set_modified
• File::set_times
• IpAddr::to_canonical
• Ipv6Addr::to_canonical
• Option::as_slice
• Option::as_mut_slice
• pointer::byte_add
• pointer::byte_offset
• pointer::byte_offset_from
• pointer::byte_sub
• pointer::wrapping_byte_add
• pointer::wrapping_byte_offset
• pointer::wrapping_byte_sub

These APIs are now stable in const contexts:

• Ipv6Addr::to_ipv4_mapped
• MaybeUninit::assume_init_read
• MaybeUninit::zeroed
• mem::discriminant
• mem::zeroed

Cargo

• Add new packages to [workspace.members] automatically.
• Allow version-less Cargo.toml manifests.
• Make browser links out of HTML file paths.

Rustdoc

• Accept less invalid Rust in rustdoc.
• Document lack of object safety on affected traits.
• Hide #[repr(transparent)] if it isn't part of the public ABI.
• Show enum discriminant if it is a C-like variant.

Compatibility Notes

• FreeBSD targets now require at least version 12.
• Formally demote tier 2 MIPS targets to tier 3.
• Make misalignment a hard error in const contexts.
• Fix detecting references to packed unsized fields.
• Remove support for compiler plugins.

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.

• Optimize librustc_driver.so with BOLT.
• Enable parallel rustc front end in dev and nightly builds.
• Distribute rustc-codegen-cranelift as rustup component on the nightly channel.

• Resolved spurious STATUS_ACCESS_VIOLATIONs in LLVM
• Clarify guarantees for std::mem::discriminant
• Fix some subtyping-related regressions

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

• In Cargo.toml, stabilize [lints]
• 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

• Add warning block support in rustdoc
• 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.

Language

• Uplift clippy::fn_null_check lint as useless_ptr_null_checks.
• Make noop_method_call warn by default.
• Support interpolated block for try and async in macros.
• Make unconditional_recursion lint detect recursive drops.
• Future compatibility warning for some impls being incorrectly considered not overlapping.
• The invalid_reference_casting lint is now deny-by-default (instead of allow-by-default)

Compiler

• Write version information in a .comment section like GCC/Clang.
• Add documentation on v0 symbol mangling.
• Stabilize extern "thiscall" and "thiscall-unwind" ABIs.
• Only check outlives goals on impl compared to trait.
• Infer type in irrefutable slice patterns with fixed length as array.
• Discard default auto trait impls if explicit ones exist.
• Add several new tier 3 targets:
  • aarch64-unknown-teeos
  • csky-unknown-linux-gnuabiv2
  • riscv64-linux-android
  • riscv64gc-unknown-hermit
  • x86_64-unikraft-linux-musl
  • x86_64-unknown-linux-ohos
• Add wasm32-wasi-preview1-threads as a tier 2 target.

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Add Read, Write and Seek impls for Arc<File>.
• Merge functionality of io::Sink into io::Empty.
• Implement RefUnwindSafe for Backtrace
• Make ExitStatus implement Default
• impl SliceIndex<str> for (Bound<usize>, Bound<usize>)
• Change default panic handler message format.
• Cleaner assert_eq! & assert_ne! panic messages.
• Correct the (deprecated) Android stat struct definitions.

Stabilized APIs

• Unsigned {integer}::div_ceil
• Unsigned {integer}::next_multiple_of
• Unsigned {integer}::checked_next_multiple_of
• std::ffi::FromBytesUntilNulError
• std::os::unix::fs::chown
• std::os::unix::fs::fchown
• std::os::unix::fs::lchown
• LocalKey::<Cell<T>>::get
• LocalKey::<Cell<T>>::set
• LocalKey::<Cell<T>>::take
• LocalKey::<Cell<T>>::replace
• LocalKey::<RefCell<T>>::with_borrow
• LocalKey::<RefCell<T>>::with_borrow_mut
• LocalKey::<RefCell<T>>::set
• LocalKey::<RefCell<T>>::take
• LocalKey::<RefCell<T>>::replace

These APIs are now stable in const contexts:

• rc::Weak::new
• sync::Weak::new
• NonNull::as_ref

Cargo

• Bail out an error when using cargo:: in custom build script.

Misc

Compatibility Notes

• Update the minimum external LLVM to 15.
• Check for non-defining uses of return position impl Trait.

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.

• Remove LLVM pointee types, supporting only opaque pointers.
• Port PGO/LTO/BOLT optimized build pipeline to Rust.
• Replace in-tree rustc_apfloat with the new version of the crate.
• Update to LLVM 17.
• Add internal_features lint for internal unstable features.
• Mention style for new syntax in tracking issue template.

• Fix CVE-2023-38497: Cargo did not respect the umask when extracting dependencies
• Fix bash completion for users of Rustup
• Do not show suspicious_double_ref_op lint when calling borrow()
• Fix ICE: substitute types before checking inlining compatibility
• Fix ICE: don't use can_eq in derive(..) suggestion for missing method
• Fix building Rust 1.71.0 from the source tarball

• Adjust codegen change to improve LLVM codegen
• rustdoc: Fix self ty params in objects with lifetimes
• Fix regression in compile times
• Resolve some ICE regressions in the compiler:
  • #115215
  • #115559

Language

• Replace const eval limit by a lint and add an exponential backoff warning
• expand: Change how #![cfg(FALSE)] behaves on crate root
• Stabilize inline asm for LoongArch64
• Uplift clippy::undropped_manually_drops lint
• Uplift clippy::invalid_utf8_in_unchecked lint as invalid_from_utf8_unchecked and invalid_from_utf8
• Uplift clippy::cast_ref_to_mut lint as invalid_reference_casting
• Uplift clippy::cmp_nan lint as invalid_nan_comparisons
• resolve: Remove artificial import ambiguity errors
• Don't require associated types with Self: Sized bounds in dyn Trait objects

Compiler

• Remember names of cfg-ed out items to mention them in diagnostics
• Support for native WASM exceptions
• Add support for NetBSD/aarch64-be (big-endian arm64).
• Write to stdout if - is given as output file
• Force all native libraries to be statically linked when linking a static binary
• Add Tier 3 support for loongarch64-unknown-none*
• Prevent .eh_frame from being emitted for -C panic=abort
• Support 128-bit enum variant in debuginfo codegen
• compiler: update solaris/illumos to enable tsan support.

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Document memory orderings of thread::{park, unpark}
• io: soften ‘at most one write attempt’ requirement in io::Write::write
• Specify behavior of HashSet::insert
• Relax implicit T: Sized bounds on BufReader<T>, BufWriter<T> and LineWriter<T>
• Update runtime guarantee for select_nth_unstable
• Return Ok on kill if process has already exited
• Implement PartialOrd for Vecs over different allocators
• Use 128 bits for TypeId hash
• Don't drain-on-drop in DrainFilter impls of various collections.
• Make {Arc,Rc,Weak}::ptr_eq ignore pointer metadata

Rustdoc

• Allow whitespace as path separator like double colon
• Add search result item types after their name
• Search for slices and arrays by type with []
• Clean up type unification and "unboxing"

Stabilized APIs

• impl<T: Send> Sync for mpsc::Sender<T>
• impl TryFrom<&OsStr> for &str
• String::leak

These APIs are now stable in const contexts:

• CStr::from_bytes_with_nul
• CStr::to_bytes
• CStr::to_bytes_with_nul
• CStr::to_str

Cargo

• Enable -Zdoctest-in-workspace by default. When running each documentation test, the working directory is set to the root directory of the package the test belongs to. docs #12221 #12288
• Add support of the "default" keyword to reset previously set build.jobs parallelism back to the default. #12222

Compatibility Notes

• Alter Display for Ipv6Addr for IPv4-compatible addresses
• Cargo changed feature name validation check to a hard error. The warning was added in Rust 1.49. These extended characters aren't allowed on crates.io, so this should only impact users of other registries, or people who don't publish to a registry. #12291
• Demoted mips*-unknown-linux-gnu* targets from host tier 2 to target tier 3 support.