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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.

Language

• Stabilize raw-dylib, link_ordinal, import_name_type and -Cdlltool.
• Uplift clippy::{drop,forget}_{ref,copy} lints.
• Type inference is more conservative around constrained vars.
• Use fulfillment to check Drop impl compatibility

Compiler

• Evaluate place expression in PlaceMention, making let _ = patterns more consistent with respect to the borrow checker.
• Add --print deployment-target flag for Apple targets.
• Stabilize extern "C-unwind" and friends. The existing extern "C" etc. may change behavior for cross-language unwinding in a future release.
• Update the version of musl used on *-linux-musl targets to 1.2.3, enabling time64 on 32-bit systems.
• Stabilize debugger_visualizer for embedding metadata like Microsoft's Natvis.
• Enable flatten-format-args by default.
• Make Self respect tuple constructor privacy.
• Improve niche placement by trying two strategies and picking the better result.
• Use apple-m1 as the target CPU for aarch64-apple-darwin.
• Add Tier 3 support for the x86_64h-apple-darwin target.
• Promote loongarch64-unknown-linux-gnu to Tier 2 with host tools.

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

Libraries

• Rework handling of recursive panics. Additional panics are allowed while unwinding, as long as they are caught before escaping a Drop implementation, but panicking within a panic hook is now an immediate abort.
• Loosen From<&[T]> for Box<[T]> bound to T: Clone.
• Remove unnecessary T: Send bound in Error for mpsc::SendError<T> and TrySendError<T>.
• Fix docs for alloc::realloc to match Layout requirements that the size must not exceed isize::MAX.
• Document const {} syntax for std::thread_local. This syntax was stabilized in Rust 1.59, but not previously mentioned in release notes.

Stabilized APIs

• CStr::is_empty
• BuildHasher::hash_one
• NonZeroI*::is_positive
• NonZeroI*::is_negative
• NonZeroI*::checked_neg
• NonZeroI*::overflowing_neg
• NonZeroI*::saturating_neg
• NonZeroI*::wrapping_neg
• Neg for NonZeroI*
• Neg for &NonZeroI*
• From<[T; N]> for (T...) (array to N-tuple for N in 1..=12)
• From<(T...)> for [T; N] (N-tuple to array for N in 1..=12)
• windows::io::AsHandle for Box<T>
• windows::io::AsHandle for Rc<T>
• windows::io::AsHandle for Arc<T>
• windows::io::AsSocket for Box<T>
• windows::io::AsSocket for Rc<T>
• windows::io::AsSocket for Arc<T>

These APIs are now stable in const contexts:

• <*const T>::read
• <*const T>::read_unaligned
• <*mut T>::read
• <*mut T>::read_unaligned
• ptr::read
• ptr::read_unaligned
• <[T]>::split_at

Cargo

• Allow named debuginfo options in Cargo.toml.
• Add workspace_default_members to the output of cargo metadata.
• Automatically inherit workspace fields when running cargo new/cargo init.

Rustdoc

• Add a new rustdoc::unescaped_backticks lint for broken inline code.
• Support strikethrough with single tildes. (~~old~~ vs. ~new~)

Misc

Compatibility Notes

• Remove structural match from TypeId. Code that uses a constant TypeId in a pattern will potentially be broken. Known cases have already been fixed -- in particular, users of the log crate's kv_unstable feature should update to log v0.4.18 or later.
• Add a sysroot crate to represent the standard library crates. This does not affect stable users, but may require adjustment in tools that build their own standard library.
• Cargo optimizes its usage under rustup. When Cargo detects it will run rustc pointing to a rustup proxy, it'll try bypassing the proxy and use the underlying binary directly. There are assumptions around the interaction with rustup and RUSTUP_TOOLCHAIN. However, it's not expected to affect normal users.
• When querying a package, Cargo tries only the original name, all hyphens, and all underscores to handle misspellings. Previously, Cargo tried each combination of hyphens and underscores, causing excessive requests to crates.io.
• Cargo now disallows RUSTUP_HOME and RUSTUP_TOOLCHAIN in the [env] configuration table. This is considered to be not a use case Cargo would like to support, since it will likely cause problems or lead to confusion.

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.

Language

• Relax ordering rules for asm! operands
• Properly allow macro expanded format_args invocations to uses captures
• Lint ambiguous glob re-exports
• Perform const and unsafe checking for expressions in let _ = expr position.

Compiler

• Extend -Cdebuginfo with new options and named aliases This provides a smaller version of debuginfo for cases that only need line number information (-Cdebuginfo=line-tables-only), which may eventually become the default for -Cdebuginfo=1.
• Make unused_allocation lint against Box::new too
• Detect uninhabited types early in const eval
• Switch to LLD as default linker for {arm,thumb}v4t-none-eabi
• Add tier 3 target loongarch64-unknown-linux-gnu
• Add tier 3 target for i586-pc-nto-qnx700 (QNX Neutrino RTOS, version 7.0),
• Insert alignment checks for pointer dereferences as debug assertions This catches undefined behavior at runtime, and may cause existing code to fail.

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

Libraries

• Document NonZeroXxx layout guarantees
• Windows: make Command prefer non-verbatim paths
• Implement Default for some alloc/core iterators
• Fix handling of trailing bare CR in str::lines
• allow negative numeric literals in concat!
• Add documentation about the memory layout of Cell
• Use partial_cmp to implement tuple lt/le/ge/gt
• Stabilize atomic_as_ptr
• Stabilize nonnull_slice_from_raw_parts
• Partial stabilization of once_cell
• Stabilize nonzero_min_max
• Flatten/inline format_args!() and (string and int) literal arguments into format_args!()
• Stabilize movbe target feature
• don't splice from files into pipes in io::copy
• Add a builtin unstable FnPtr trait that is implemented for all function pointers This extends Debug, Pointer, Hash, PartialEq, Eq, PartialOrd, and Ord implementations for function pointers with all ABIs.

Stabilized APIs

• NonZero*::MIN/MAX
• BinaryHeap::retain
• Default for std::collections::binary_heap::IntoIter
• Default for std::collections::btree_map::{IntoIter, Iter, IterMut}
• Default for std::collections::btree_map::{IntoKeys, Keys}
• Default for std::collections::btree_map::{IntoValues, Values}
• Default for std::collections::btree_map::Range
• Default for std::collections::btree_set::{IntoIter, Iter}
• Default for std::collections::btree_set::Range
• Default for std::collections::linked_list::{IntoIter, Iter, IterMut}
• Default for std::vec::IntoIter
• Default for std::iter::Chain
• Default for std::iter::Cloned
• Default for std::iter::Copied
• Default for std::iter::Enumerate
• Default for std::iter::Flatten
• Default for std::iter::Fuse
• Default for std::iter::Rev
• Default for std::slice::Iter
• Default for std::slice::IterMut
• Rc::into_inner
• Arc::into_inner
• std::cell::OnceCell
• Option::is_some_and
• NonNull::slice_from_raw_parts
• Result::is_ok_and
• Result::is_err_and
• std::sync::atomic::Atomic*::as_ptr
• std::io::IsTerminal
• std::os::linux::net::SocketAddrExt
• std::os::unix::net::UnixDatagram::bind_addr
• std::os::unix::net::UnixDatagram::connect_addr
• std::os::unix::net::UnixDatagram::send_to_addr
• std::os::unix::net::UnixListener::bind_addr
• std::path::Path::as_mut_os_str
• std::sync::OnceLock

Cargo

• Add CARGO_PKG_README
• Make sparse the default protocol for crates.io
• Accurately show status when downgrading dependencies
• Use registry.default for login/logout
• Stabilize cargo logout

Misc

• Stabilize rustdoc --test-run-directory

Compatibility Notes

• Prevent stable libtest from supporting -Zunstable-options
• Perform const and unsafe checking for expressions in let _ = expr position.
• WebAssembly targets enable sign-ext and mutable-globals features in codegen This may cause incompatibility with older execution environments.
• Insert alignment checks for pointer dereferences as debug assertions This catches undefined behavior at runtime, and may cause existing code to fail.

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.

• Upgrade to LLVM 16
• Use SipHash-1-3 instead of SipHash-2-4 for StableHasher

Language

• Deriving built-in traits on packed structs works with Copy fields.
• Stabilize the cmpxchg16b target feature on x86 and x86_64.
• Improve analysis of trait bounds for associated types.
• Allow associated types to be used as union fields.
• Allow Self: Autotrait bounds on dyn-safe trait methods.
• Treat str as containing [u8] for auto trait purposes.

Compiler

• Upgrade *-pc-windows-gnu on CI to mingw-w64 v10 and GCC 12.2.
• Rework min_choice algorithm of member constraints.
• Support true and false as boolean flags in compiler arguments.
• Default repr(C) enums to c_int size.

Libraries

• Implement the unstable DispatchFromDyn for cell types, allowing downstream experimentation with custom method receivers.
• Document that fmt::Arguments::as_str() may return Some(_) in more cases after optimization, subject to change.
• Implement AsFd and AsRawFd for Rc.

Stabilized APIs

• CStr::from_bytes_until_nul
• core::ffi::FromBytesUntilNulError

These APIs are now stable in const contexts:

• SocketAddr::new
• SocketAddr::ip
• SocketAddr::port
• SocketAddr::is_ipv4
• SocketAddr::is_ipv6
• SocketAddrV4::new
• SocketAddrV4::ip
• SocketAddrV4::port
• SocketAddrV6::new
• SocketAddrV6::ip
• SocketAddrV6::port
• SocketAddrV6::flowinfo
• SocketAddrV6::scope_id

Cargo

• Cargo now suggests cargo fix or cargo clippy --fix when compilation warnings are auto-fixable.
• Cargo now suggests cargo add if you try to install a library crate.
• Cargo now sets the CARGO_BIN_NAME environment variable also for binary examples.

Rustdoc

• Vertically compact trait bound formatting.
• Only include stable lints in rustdoc::all group.
• Compute maximum Levenshtein distance based on the query.
• Remove inconsistently-present sidebar tooltips.
• Search by macro when query ends with !.

Compatibility Notes

• The rust-analysis component from rustup now only contains a warning placeholder. This was primarily intended for RLS, and the corresponding -Zsave-analysis flag has been removed from the compiler as well.
• Unaligned references to packed fields are now a hard error. This has been a warning since 1.53, and denied by default with a future-compatibility warning since 1.62.
• Update the minimum external LLVM to 14.
• Cargo now emits errors on invalid characters in a registry token.
• When default-features is set to false of a workspace dependency, and an inherited dependency of a member has default-features = true, Cargo will enable default features of that dependency.
• Cargo denies CARGO_HOME in the [env] configuration table. Cargo itself doesn't pick up this value, but recursive calls to cargo would, which was not intended.
• Debuginfo for build dependencies is now off if not explicitly set. This is expected to improve the overall build time.
• The Rust distribution no longer always includes rustdoc If tools = [...] is set in config.toml, we will respect a missing rustdoc in that list. By default rustdoc remains included. To retain the prior behavior explicitly add "rustdoc" to the list.

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.

• Move format_args!() into AST (and expand it during AST lowering)

• Update the GitHub RSA host key bundled within Cargo. The key was rotated by GitHub on 2023-03-24 after the old one leaked.
• Mark the old GitHub RSA host key as revoked. This will prevent Cargo from accepting the leaked key even when trusted by the system.
• Add support for @revoked and a better error message for @cert-authority in Cargo's SSH host key verification

• Fix miscompilation in produced Windows MSVC artifacts This was introduced by enabling ThinLTO for the distributed rustc which led to miscompilations in the resulting binary. Currently this is believed to be limited to the -Zdylib-lto flag used for rustc compilation, rather than a general bug in ThinLTO, so only rustc artifacts should be affected.
• Fix --enable-local-rust builds
• Treat $prefix-clang as clang in linker detection code
• Fix panic in compiler code

Language

• Stabilize default_alloc_error_handler This allows usage of alloc on stable without requiring the definition of a handler for allocation failure. Defining custom handlers is still unstable.
• Stabilize efiapi calling convention.
• Remove implicit promotion for types with drop glue

Compiler

• Change bindings_with_variant_name to deny-by-default
• Allow .. to be parsed as let initializer
• Add armv7-sony-vita-newlibeabihf as a tier 3 target
• Always check alignment during compile-time const evaluation
• Disable "split dwarf inlining" by default.
• Add vendor to Fuchsia's target triple
• Enable sanitizers for s390x-linux

Libraries

• Loosen the bound on the Debug implementation of Weak.
• Make std::task::Context !Send and !Sync
• PhantomData layout guarantees
• Don't derive Debug for OnceWith & RepeatWith
• Implement DerefMut for PathBuf
• Add O(1) Vec -> VecDeque conversion guarantee
• Leak amplification for peek_mut() to ensure BinaryHeap's invariant is always met

Stabilized APIs

• {core,std}::pin::pin!
• impl From<bool> for {f32,f64}
• std::path::MAIN_SEPARATOR_STR
• impl DerefMut for PathBuf

These APIs are now stable in const contexts:

• VecDeque::new

Cargo

• Stabilize sparse registry support for crates.io
• cargo build --verbose tells you more about why it recompiles.
• Show progress of crates.io index update even net.git-fetch-with-cli option enabled

Misc

Compatibility Notes

• Only support Android NDK 25 or newer
• Add SEMICOLON_IN_EXPRESSIONS_FROM_MACROS to future-incompat report
• Only specify --target by default for -Zgcc-ld=lld on wasm
• Bump IMPLIED_BOUNDS_ENTAILMENT to Deny + ReportNow
• std::task::Context no longer implements Send and Sync

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.

• Encode spans relative to the enclosing item
• Don't normalize in AstConv
• Find the right lower bound region in the scenario of partial order relations
• Fix impl block in const expr
• Check ADT fields for copy implementations considering regions
• rustdoc: simplify JS search routine by not messing with lev distance
• Enable ThinLTO for rustc on x86_64-pc-windows-msvc
• Enable ThinLTO for rustc on x86_64-apple-darwin

• Fix interoperability with thin archives.
• Fix an internal error in the compiler build process.
• Downgrade clippy::uninlined_format_args to pedantic.

Language

• Make Sized predicates coinductive, allowing cycles.
• #[must_use] annotations on async fn also affect the Future::Output.
• Elaborate supertrait obligations when deducing closure signatures.
• Invalid literals are no longer an error under cfg(FALSE).
• Unreserve braced enum variants in value namespace.

Compiler

• Enable varargs support for calling conventions other than C or cdecl.
• Add new MIR constant propagation based on dataflow analysis.
• Optimize field ordering by grouping m*2^n-sized fields with equivalently aligned ones.
• Stabilize native library modifier verbatim.

Added, updated, and removed targets:

• Add a tier 3 target for PowerPC on AIX, powerpc64-ibm-aix.
• Add a tier 3 target for the Sony PlayStation 1, mipsel-sony-psx.
• Add tier 3 no_std targets for the QNX Neutrino RTOS, aarch64-unknown-nto-qnx710 and x86_64-pc-nto-qnx710.
• Promote UEFI targets to tier 2, aarch64-unknown-uefi, i686-unknown-uefi, and x86_64-unknown-uefi.
• Remove tier 3 linuxkernel targets (not used by the actual kernel).

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

Libraries

• Merge crossbeam-channel into std::sync::mpsc.
• Fix inconsistent rounding of 0.5 when formatted to 0 decimal places.
• Derive Eq and Hash for ControlFlow.
• Don't build compiler_builtins with -C panic=abort.

Stabilized APIs

• {integer}::checked_ilog
• {integer}::checked_ilog2
• {integer}::checked_ilog10
• {integer}::ilog
• {integer}::ilog2
• {integer}::ilog10
• NonZeroU*::ilog2
• NonZeroU*::ilog10
• NonZero*::BITS

These APIs are now stable in const contexts:

• char::from_u32
• char::from_digit
• char::to_digit
• core::char::from_u32
• core::char::from_digit

Compatibility Notes

• The layout of repr(Rust) types now groups m*2^n-sized fields with equivalently aligned ones. This is intended to be an optimization, but it is also known to increase type sizes in a few cases for the placement of enum tags. As a reminder, the layout of repr(Rust) types is an implementation detail, subject to change.
• 0.5 now rounds to 0 when formatted to 0 decimal places. This makes it consistent with the rest of floating point formatting that rounds ties toward even digits.
• Chains of && and || will now drop temporaries from their sub-expressions in evaluation order, left-to-right. Previously, it was "twisted" such that the first expression dropped its temporaries last, after all of the other expressions dropped in order.
• Underscore suffixes on string literals are now a hard error. This has been a future-compatibility warning since 1.20.0.
• Stop passing -export-dynamic to wasm-ld.
• main is now mangled as __main_void on wasm32-wasi.
• Cargo now emits an error if there are multiple registries in the configuration with the same index URL.

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.

• Rewrite LLVM's archive writer in Rust.

• Added validation of SSH host keys for git URLs in Cargo (CVE-2022-46176)