Rust 1.91.0

Language

• Lower pattern bindings in the order they're written and base drop order on primary bindings' order
• Stabilize declaration of C-style variadic functions for sysv64, win64, efiapi, and aapcs ABIs. This brings these ABIs in line with the C ABI: variadic functions can be declared in extern blocks but not defined.
• Add dangling_pointers_from_locals lint to warn against dangling pointers from local variables
• Upgrade semicolon_in_expressions_from_macros from warn to deny
• Stabilize LoongArch32 inline assembly
• Add warn-by-default integer_to_ptr_transmutes lint against integer-to-pointer transmutes
• Stabilize sse4a and tbm target features
• Add target_env = "macabi" and target_env = "sim" cfgs as replacements for the target_abi cfgs with the same values.

Compiler

• Don't warn on never-to-any as casts as unreachable

Platform Support

• Promote aarch64-pc-windows-gnullvm and x86_64-pc-windows-gnullvm to Tier 2 with host tools. Note: llvm-tools and MSI installers are missing but will be added in future releases.
• Promote aarch64-pc-windows-msvc to Tier 1

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

Libraries

• Print thread ID in panic message
• Fix overly restrictive lifetime in core::panic::Location::file return type
• Guarantee parameter order for _by() variants of min / max/ minmax in std::cmp
• Document assumptions about Clone and Eq traits
• std::thread: Return error if setting thread stack size fails This used to panic within the standard library.

Stabilized APIs

• Path::file_prefix
• AtomicPtr::fetch_ptr_add
• AtomicPtr::fetch_ptr_sub
• AtomicPtr::fetch_byte_add
• AtomicPtr::fetch_byte_sub
• AtomicPtr::fetch_or
• AtomicPtr::fetch_and
• AtomicPtr::fetch_xor
• {integer}::strict_add
• {integer}::strict_sub
• {integer}::strict_mul
• {integer}::strict_div
• {integer}::strict_div_euclid
• {integer}::strict_rem
• {integer}::strict_rem_euclid
• {integer}::strict_neg
• {integer}::strict_shl
• {integer}::strict_shr
• {integer}::strict_pow
• i{N}::strict_add_unsigned
• i{N}::strict_sub_unsigned
• i{N}::strict_abs
• u{N}::strict_add_signed
• u{N}::strict_sub_signed
• PanicHookInfo::payload_as_str
• core::iter::chain
• u{N}::checked_signed_diff
• core::array::repeat
• PathBuf::add_extension
• PathBuf::with_added_extension
• Duration::from_mins
• Duration::from_hours
• impl PartialEq<str> for PathBuf
• impl PartialEq<String> for PathBuf
• impl PartialEq<str> for Path
• impl PartialEq<String> for Path
• impl PartialEq<PathBuf> for String
• impl PartialEq<Path> for String
• impl PartialEq<PathBuf> for str
• impl PartialEq<Path> for str
• Ipv4Addr::from_octets
• Ipv6Addr::from_octets
• Ipv6Addr::from_segments
• impl<T> Default for Pin<Box<T>> where Box<T>: Default, T: ?Sized
• impl<T> Default for Pin<Rc<T>> where Rc<T>: Default, T: ?Sized
• impl<T> Default for Pin<Arc<T>> where Arc<T>: Default, T: ?Sized
• Cell::as_array_of_cells
• u{N}::carrying_add
• u{N}::borrowing_sub
• u{N}::carrying_mul
• u{N}::carrying_mul_add
• BTreeMap::extract_if
• BTreeSet::extract_if
• impl Debug for windows::ffi::EncodeWide<'_>
• str::ceil_char_boundary
• str::floor_char_boundary
• impl Sum for Saturating<u{N}>
• impl Sum<&Self> for Saturating<u{N}>
• impl Product for Saturating<u{N}>
• impl Product<&Self> for Saturating<u{N}>

These previously stable APIs are now stable in const contexts:

• [<[T; N]>::each_ref](https://doc.rust-lang.org/stable/std/...

Rust 1.90.0

Language

• Split up the unknown_or_malformed_diagnostic_attributes lint. This lint has been split up into four finer-grained lints, with unknown_or_malformed_diagnostic_attributes now being the lint group that contains these lints:
  1. unknown_diagnostic_attributes: unknown to the current compiler
  2. misplaced_diagnostic_attributes: placed on the wrong item
  3. malformed_diagnostic_attributes: malformed attribute syntax or options
  4. malformed_diagnostic_format_literals: malformed format string literal
• Allow constants whose final value has references to mutable/external memory, but reject such constants as patterns
• Allow volatile access to non-Rust memory, including address 0

Compiler

• Use lld by default on x86_64-unknown-linux-gnu.
• Tier 3 musl targets now link dynamically by default. Affected targets:
  • mips64-unknown-linux-muslabi64
  • powerpc64-unknown-linux-musl
  • powerpc-unknown-linux-musl
  • powerpc-unknown-linux-muslspe
  • riscv32gc-unknown-linux-musl
  • s390x-unknown-linux-musl
  • thumbv7neon-unknown-linux-musleabihf

Platform Support

• Demote x86_64-apple-darwin to Tier 2 with host tools

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

Libraries

• Stabilize u*::{checked,overflowing,saturating,wrapping}_sub_signed
• Allow comparisons between CStr, CString, and Cow<CStr>
• Remove some unsized tuple impls since unsized tuples can't be constructed
• Set MSG_NOSIGNAL for UnixStream
• proc_macro::Ident::new now supports $crate.
• Guarantee the pointer returned from Thread::into_raw has at least 8 bytes of alignment

Stabilized APIs

• u{n}::checked_sub_signed
• u{n}::overflowing_sub_signed
• u{n}::saturating_sub_signed
• u{n}::wrapping_sub_signed
• impl Copy for IntErrorKind
• impl Hash for IntErrorKind
• impl PartialEq<&CStr> for CStr
• impl PartialEq<CString> for CStr
• impl PartialEq<Cow<CStr>> for CStr
• impl PartialEq<&CStr> for CString
• impl PartialEq<CStr> for CString
• impl PartialEq<Cow<CStr>> for CString
• impl PartialEq<&CStr> for Cow<CStr>
• impl PartialEq<CStr> for Cow<CStr>
• impl PartialEq<CString> for Cow<CStr>

These previously stable APIs are now stable in const contexts:

• <[T]>::reverse
• f32::floor
• f32::ceil
• f32::trunc
• f32::fract
• f32::round
• f32::round_ties_even
• f64::floor
• f64::ceil
• f64::trunc
• f64::fract
• f64::round
• f64::round_ties_even

Cargo

• Add http.proxy-cainfo config for proxy certs
• Use gix for cargo package
• feat(publish): Stabilize multi-package publishing

Rustdoc

• Add ways to collapse all impl blocks. Previously the "Summary" button and "-" keyboard shortcut would never collapse impl blocks, now they do when shift is held
• Display unsafe attributes with unsafe() wrappers

Compatibility Notes

• Use lld by default on x86_64-unknown-linux-gnu. See also https://blog.rust-lang.org/2025/09/01/rust-lld-on-1.90.0-stable/.
• Make core::iter::Fuse's Default impl construct I::default() internally as promised in the docs instead of always being empty
• Set MSG_NOSIGNAL for UnixStream This may change program behavior but results in the same behavior as other primitives (e.g., stdout, network sockets). Programs relying on signals to terminate them should update handling of sockets to handle errors on write by exiting.
• On Unix std::env::home_dir will use the fallback if the HOME environment variable is empty
• We now reject unsupported extern "{abi}"s consistently in all positions. This primarily affects the use of implementing traits on an extern "{abi}" function pointer, like extern "stdcall" fn(), on a platform that doesn't support that, like aarch64-unknown-linux-gnu. Direct usage of these unsupported ABI strings by declaring or defining functions was already rejected, so this is only a change for consistency.
• const-eval: error when initializing a static writes to that static
• Check that the proc_macro_derive macro has correct arguments when applied to the crate root

Rust 1.89.0

Language

• Stabilize explicitly inferred const arguments (feature(generic_arg_infer))
• Add a warn-by-default mismatched_lifetime_syntaxes lint. This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code. This lint supersedes the warn-by-default elided_named_lifetimes lint.
• Expand unpredictable_function_pointer_comparisons to also lint on function pointer comparisons in external macros
• Make the dangerous_implicit_autorefs lint deny-by-default
• Stabilize the avx512 target features
• Stabilize kl and widekl target features for x86
• Stabilize sha512, sm3 and sm4 target features for x86
• Stabilize LoongArch target features f, d, frecipe, lasx, lbt, lsx, and lvz
• Remove i128 and u128 from improper_ctypes_definitions
• Stabilize repr128 (#[repr(u128)], #[repr(i128)])
• Allow #![doc(test(attr(..)))] everywhere
• Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors
• extern "C" functions on the wasm32-unknown-unknown target now have a standards compliant ABI

Compiler

• Default to non-leaf frame pointers on aarch64-linux
• Enable non-leaf frame pointers for Arm64EC Windows
• Set Apple frame pointers by architecture

Platform Support

• Add new Tier-3 targets loongarch32-unknown-none and loongarch32-unknown-none-softfloat
• x86_64-apple-darwin is in the process of being demoted to Tier 2 with host tools

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

Libraries

• Specify the base path for file!
• Allow storing format_args!() in a variable
• Add #[must_use] to [T; N]::map
• Implement DerefMut for Lazy{Cell,Lock}
• Implement Default for array::IntoIter
• Implement Clone for slice::ChunkBy
• Implement io::Seek for io::Take

Stabilized APIs

• NonZero<char>
• Many intrinsics for x86, not enumerated here
  • AVX512 intrinsics
  • SHA512, SM3 and SM4 intrinsics
• File::lock
• File::lock_shared
• File::try_lock
• File::try_lock_shared
• File::unlock
• NonNull::from_ref
• NonNull::from_mut
• NonNull::without_provenance
• NonNull::with_exposed_provenance
• NonNull::expose_provenance
• OsString::leak
• PathBuf::leak
• Result::flatten
• std::os::linux::net::TcpStreamExt::quickack
• std::os::linux::net::TcpStreamExt::set_quickack

These previously stable APIs are now stable in const contexts:

• <[T; N]>::as_mut_slice
• <[u8]>::eq_ignore_ascii_case
• str::eq_ignore_ascii_case

Cargo

• cargo fix and cargo clippy --fix now default to the same Cargo target selection as other build commands. Previously it would apply to all targets (like binaries, examples, tests, etc.). The --edition flag still applies to all targets.
• Stabilize doctest-xcompile. Doctests are now tested when cross-compiling. Just like other tests, it will use the runner setting to run the tests. If you need to disable tests for a target, you can use the ignore doctest attribute to specify the targets to ignore.

Rustdoc

• On mobile, make the sidebar full width and linewrap. This makes long section and item names much easier to deal with on mobile.

Compatibility Notes

• Make missing_fragment_specifier an unconditional error
• Enabling the neon target feature on aarch64-unknown-none-softfloat causes a warning because mixing code with and without that target feature is not properly supported by LLVM
• Sized Hierarchy: Part I
  • Introduces a small breaking change affecting ?Sized bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the sized_hierarchy unstable feature. See the FCP report for a code example.
• The warn-by-default elided_named_lifetimes lint is superseded by the warn-by-default mismatched_lifetime_syntaxes lint.
• Error on recursive opaque types earlier in the type checker
• Type inference side effects from requiring element types of array repeat expressions are Copy are now only available at the end of type checking
• The deprecated accidentally-stable std::intrinsics::{copy,copy_nonoverlapping,write_bytes} are now proper intrinsics. There are no debug assertions guarding against UB, and they cannot be coerced to function pointers.
• Remove long-deprecated std::intrinsics::drop_in_place
• Make well-formedness predicates no longer coinductive
• Remove hack when checking impl method compatibility
• Remove unnecessary type inference due to built-in trait object impls
• Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets
• Future incompatibility warnings relating to the never type (!) are now reported in dependencies
• Ensure std::ptr::copy_* intrinsics also perform the static self-init checks
• extern "C" functions on the wasm32-unknown-unknown target now have a standards compliant ABI

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.

• Correctly un-remap compiler sources paths with the rustc-dev component

Rust 1.88.0

Language

• Stabilize #![feature(let_chains)] in the 2024 edition. This feature allows &&-chaining let statements inside if and while, allowing intermixture with boolean expressions. The patterns inside the let sub-expressions can be irrefutable or refutable.
• Stabilize #![feature(naked_functions)]. Naked functions allow writing functions with no compiler-generated epilogue and prologue, allowing full control over the generated assembly for a particular function.
• Stabilize #![feature(cfg_boolean_literals)]. This allows using boolean literals as cfg predicates, e.g. #[cfg(true)] and #[cfg(false)].
• Fully de-stabilize the #[bench] attribute. Usage of #[bench] without #![feature(custom_test_frameworks)] already triggered a deny-by-default future-incompatibility lint since Rust 1.77, but will now become a hard error.
• Add warn-by-default dangerous_implicit_autorefs lint against implicit autoref of raw pointer dereference. The lint will be bumped to deny-by-default in the next version of Rust.
• Add invalid_null_arguments lint to prevent invalid usage of null pointers. This lint is uplifted from clippy::invalid_null_ptr_usage.
• Change trait impl candidate preference for builtin impls and trivial where-clauses.
• Check types of generic const parameter defaults

Compiler

• Stabilize -Cdwarf-version for selecting the version of DWARF debug information to generate.

Platform Support

• Demote i686-pc-windows-gnu to Tier 2.

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

Libraries

• Remove backticks from #[should_panic] test failure message.
• Guarantee that [T; N]::from_fn is generated in order of increasing indices., for those passing it a stateful closure.
• The libtest flag --nocapture is deprecated in favor of the more consistent --no-capture flag.
• Guarantee that {float}::NAN is a quiet NaN.

Stabilized APIs

• Cell::update
• impl Default for *const T
• impl Default for *mut T
• HashMap::extract_if
• HashSet::extract_if
• hint::select_unpredictable
• proc_macro::Span::line
• proc_macro::Span::column
• proc_macro::Span::start
• proc_macro::Span::end
• proc_macro::Span::file
• proc_macro::Span::local_file
• <[T]>::as_chunks
• <[T]>::as_chunks_mut
• <[T]>::as_chunks_unchecked
• <[T]>::as_chunks_unchecked_mut
• <[T]>::as_rchunks
• <[T]>::as_rchunks_mut
• mod ffi::c_str

These previously stable APIs are now stable in const contexts:

• NonNull<T>::replace
• <*mut T>::replace
• std::ptr::swap_nonoverlapping
• Cell::replace
• Cell::get
• Cell::get_mut
• Cell::from_mut
• Cell::as_slice_of_cells

Cargo

• Stabilize automatic garbage collection.
• use zlib-rs for gzip compression in rust code

Rustdoc

• Doctests can be ignored based on target names using ignore-* attributes.
• Stabilize the --test-runtool and --test-runtool-arg CLI options to specify a program (like qemu) and its arguments to run a doctest.

Compatibility Notes

• Finish changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
• Fully de-stabilize the #[bench] attribute. Usage of #[bench] without #![feature(custom_test_frameworks)] already triggered a deny-by-default future-incompatibility lint since Rust 1.77, but will now become a hard error.
• Fix borrow checking some always-true patterns. The borrow checker was overly permissive in some cases, allowing programs that shouldn't have compiled.
• Update the minimum external LLVM to 19.
• Make it a hard error to use a vector type with a non-Rust ABI without enabling the required target feature.

Rust 1.87.0

Language

• Stabilize asm_goto feature
• Allow parsing open beginning ranges (..EXPR) after unary operators !, -, and *.
• Don't require method impls for methods with Self: Sized bounds in impls for unsized types
• Stabilize feature(precise_capturing_in_traits) allowing use<...> bounds on return position impl Trait in traits

Compiler

• x86: make SSE2 required for i686 targets and use it to pass SIMD types

Platform Support

• Remove i586-pc-windows-msvc target

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

Libraries

• Stabilize the anonymous pipe API
• Add support for unbounded left/right shift operations
• Print pointer metadata in Debug impl of raw pointers
• Vec::with_capacity guarantees it allocates with the amount requested, even if Vec::capacity returns a different number.
• Most std::arch intrinsics which don't take pointer arguments can now be called from safe code if the caller has the appropriate target features already enabled (rust-lang/stdarch#1714, rust-lang/stdarch#1716, rust-lang/stdarch#1717)
• Undeprecate env::home_dir
• Denote ControlFlow as #[must_use]
• Macros such as assert_eq! and vec! now support const {...} expressions

Stabilized APIs

• Vec::extract_if
• vec::ExtractIf
• LinkedList::extract_if
• linked_list::ExtractIf
• <[T]>::split_off
• <[T]>::split_off_mut
• <[T]>::split_off_first
• <[T]>::split_off_first_mut
• <[T]>::split_off_last
• <[T]>::split_off_last_mut
• String::extend_from_within
• os_str::Display
• OsString::display
• OsStr::display
• io::pipe
• io::PipeReader
• io::PipeWriter
• impl From<PipeReader> for OwnedHandle
• impl From<PipeWriter> for OwnedHandle
• impl From<PipeReader> for Stdio
• impl From<PipeWriter> for Stdio
• impl From<PipeReader> for OwnedFd
• impl From<PipeWriter> for OwnedFd
• Box<MaybeUninit<T>>::write
• impl TryFrom<Vec<u8>> for String
• <*const T>::offset_from_unsigned
• <*const T>::byte_offset_from_unsigned
• <*mut T>::offset_from_unsigned
• <*mut T>::byte_offset_from_unsigned
• NonNull::offset_from_unsigned
• NonNull::byte_offset_from_unsigned
• <uN>::cast_signed
• NonZero::<uN>::cast_signed.
• <iN>::cast_unsigned.
• NonZero::<iN>::cast_unsigned.
• <uN>::is_multiple_of
• <uN>::unbounded_shl
• <uN>::unbounded_shr
• <iN>::unbounded_shl
• <iN>::unbounded_shr
• <iN>::midpoint
• <str>::from_utf8
• <str>::from_utf8_mut
• <str>::from_utf8_unchecked
• <str>::from_utf8_unchecked_mut

These previously stable APIs are now stable in const contexts:

• core::str::from_utf8_mut
• <[T]>::copy_from_slice
• SocketAddr::set_ip
• SocketAddr::set_port,
• SocketAddrV4::set_ip
• SocketAddrV4::set_port,
• SocketAddrV6::set_ip
• SocketAddrV6::set_port
• SocketAddrV6::set_flowinfo
• SocketAddrV6::set_scope_id
• char::is_digit
• char::is_whitespace
• <[[T; N]]>::as_flattened
• <[[T; N]]>::as_flattened_mut
• String::into_bytes
• String::as_str
• String::capacity
• String::as_bytes
• String::len
• String::is_empty
• String::as_mut_str
• String::as_mut_vec
• Vec::as_ptr
• Vec::as_slice
• [Vec::capacity](https://doc.r...

Rust 1.86.0

Language

• Stabilize upcasting trait objects to supertraits.
• Allow safe functions to be marked with the #[target_feature] attribute.
• The missing_abi lint now warns-by-default.
• Rust now lints about double negations, to catch cases that might have intended to be a prefix decrement operator (--x) as written in other languages. This was previously a clippy lint, clippy::double_neg, and is now available directly in Rust as double_negations.
• More pointers are now detected as definitely not-null based on their alignment in const eval.
• Empty repr() attribute applied to invalid items are now correctly rejected.
• Inner attributes #![test] and #![rustfmt::skip] are no longer accepted in more places than intended.

Compiler

• Debug-assert that raw pointers are non-null on access.
• Change -O to mean -C opt-level=3 instead of -C opt-level=2 to match Cargo's defaults.
• Fix emission of overflowing_literals under certain macro environments.

Platform Support

• Replace i686-unknown-redox target with i586-unknown-redox.
• Increase baseline CPU of i686-unknown-hurd-gnu to Pentium 4.
• New tier 3 targets:
  • {aarch64-unknown,x86_64-pc}-nto-qnx710_iosock. For supporting Neutrino QNX 7.1 with io-socket network stack.
  • {aarch64-unknown,x86_64-pc}-nto-qnx800. For supporting Neutrino QNX 8.0 (no_std-only).
  • {x86_64,i686}-win7-windows-gnu. Intended for backwards compatibility with Windows 7. {x86_64,i686}-win7-windows-msvc are the Windows MSVC counterparts that already exist as Tier 3 targets.
  • amdgcn-amd-amdhsa.
  • x86_64-pc-cygwin.
  • {mips,mipsel}-mti-none-elf. Initial bare-metal support.
  • m68k-unknown-none-elf.
  • armv7a-nuttx-{eabi,eabihf}, aarch64-unknown-nuttx, and thumbv7a-nuttx-{eabi,eabihf}.

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

Libraries

• The type of FromBytesWithNulError in CStr::from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError> was changed from an opaque struct to an enum, allowing users to examine why the conversion failed.
• Remove RustcDecodable and RustcEncodable.
• Deprecate libtest's --logfile option.
• On recent versions of Windows, std::fs::remove_file will now remove read-only files.

Stabilized APIs

• {float}::next_down
• {float}::next_up
• <[_]>::get_disjoint_mut
• <[_]>::get_disjoint_unchecked_mut
• slice::GetDisjointMutError
• HashMap::get_disjoint_mut
• HashMap::get_disjoint_unchecked_mut
• NonZero::count_ones
• Vec::pop_if
• sync::Once::wait
• sync::Once::wait_force
• sync::OnceLock::wait

These APIs are now stable in const contexts:

• hint::black_box
• io::Cursor::get_mut
• io::Cursor::set_position
• str::is_char_boundary
• str::split_at
• str::split_at_checked
• str::split_at_mut
• str::split_at_mut_checked

Cargo

• When merging, replace rather than combine configuration keys that refer to a program path and its arguments.
• Error if both --package and --workspace are passed but the requested package is missing. This was previously silently ignored, which was considered a bug since missing packages should be reported.
• Deprecate the token argument in cargo login to avoid shell history leaks.
• Simplify the implementation of SourceID comparisons. This may potentially change behavior if the canonicalized URL compares differently in alternative registries.

Rustdoc

• Add a sans-serif font setting.

Compatibility Notes

• The wasm_c_abi future compatibility warning is now a hard error. Users of wasm-bindgen should upgrade to at least version 0.2.89, otherwise compilation will fail.
• Remove long-deprecated no-op attributes #![no_start] and #![crate_id].
• The future incompatibility lint cenum_impl_drop_cast has been made into a hard error. This means it is now an error to cast a field-less enum to an integer if the enum implements Drop.
• SSE2 is now required for "i686" 32-bit x86 hard-float targets; disabling it causes a warning that will become a hard error eventually. To compile for pre-SSE2 32-bit x86, use a "i586" target instead.

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.

• Build the rustc on AArch64 Linux with ThinLTO + PGO. The ARM 64-bit compiler (AArch64) on Linux is now optimized with ThinLTO and PGO, similar to the optimizations we have already performed for the x86-64 compiler on Linux. This should make it up to 30% faster.

Rust 1.85.1

• Fix the doctest-merging feature of the 2024 Edition.
• Relax some target_feature checks when generating docs.
• Fix errors in std::fs::rename on Windows 10, version 1607.
• Downgrade bootstrap cc to fix custom targets.
• Skip submodule updates when building Rust from a source tarball.

Rust 1.85.0

Language

• The 2024 Edition is now stable. See the edition guide for more details.
• Stabilize async closures See RFC 3668 for more details.
• Stabilize #[diagnostic::do_not_recommend]
• Add unpredictable_function_pointer_comparisons lint to warn against function pointer comparisons
• Lint on combining #[no_mangle] and #[export_name] attributes.

Compiler

• The unstable flag -Zpolymorphize has been removed, see rust-lang/compiler-team#810 for some background.

Platform Support

• Promote powerpc64le-unknown-linux-musl to tier 2 with host tools

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

Libraries

• Panics in the standard library now have a leading library/ in their path

• std::env::home_dir() on Windows now ignores the non-standard $HOME environment variable

  It will be un-deprecated in a subsequent release.

• Add AsyncFn* to the prelude in all editions.

Stabilized APIs

• BuildHasherDefault::new
• ptr::fn_addr_eq
• io::ErrorKind::QuotaExceeded
• io::ErrorKind::CrossesDevices
• {float}::midpoint
• Unsigned {integer}::midpoint
• NonZeroU*::midpoint
• impl std::iter::Extend for tuples with arity 1 through 12
• FromIterator<(A, ...)> for tuples with arity 1 through 12
• std::task::Waker::noop

These APIs are now stable in const contexts:

• mem::size_of_val
• mem::align_of_val
• Layout::for_value
• Layout::align_to
• Layout::pad_to_align
• Layout::extend
• Layout::array
• std::mem::swap
• std::ptr::swap
• NonNull::new
• HashMap::with_hasher
• HashSet::with_hasher
• BuildHasherDefault::new
• <float>::recip
• <float>::to_degrees
• <float>::to_radians
• <float>::max
• <float>::min
• <float>::clamp
• <float>::abs
• <float>::signum
• <float>::copysign
• MaybeUninit::write

Cargo

• Add future-incompatibility warning against keywords in cfgs and add raw-idents
• Stabilize higher precedence trailing flags
• Pass CARGO_CFG_FEATURE to build scripts

Rustdoc

• Doc comment on impl blocks shows the first line, even when the impl block is collapsed

Compatibility Notes

• rustc no longer treats the test cfg as a well known check-cfg, instead it is up to the build systems and users of --check-cfg[^check-cfg] to set it as a well known cfg using --check-cfg=cfg(test).

  This is done to enable build systems like Cargo to set it conditionally, as not all source files are suitable for unit tests. Cargo (for now) unconditionally sets the test cfg as a well known cfg. [^check-cfg]: https://doc.rust-lang.org/nightly/rustc/check-cfg.html

• Disable potentially incorrect type inference if there are trivial and non-trivial where-clauses

• std::env::home_dir() has been deprecated for years, because it can give surprising results in some Windows configurations if the HOME environment variable is set (which is not the normal configuration on Windows). We had previously avoided changing its behavior, out of concern for compatibility with code depending on this non-standard configuration. Given how long this function has been deprecated, we're now fixing its behavior as a bugfix. A subsequent release will remove the deprecation for this function.

• Make core::ffi::c_char signedness more closely match that of the platform-default char

  This changed c_char from an i8 to u8 or vice versa on many Tier 2 and 3 targets (mostly Arm and RISC-V embedded targets). The new definition may result in compilation failures but fixes compatibility issues with C.

  The libc crate matches this change as of its 0.2.169 release.

• When compiling a nested macro_rules macro from an external crate, the content of the inner macro_rules is now built with the edition of the external crate, not the local crate.

• Increase sparcv9-sun-solaris and x86_64-pc-solaris Solaris baseline to 11.4.

• Show abi_unsupported_vector_types lint in future breakage reports

• Error if multiple super-trait instantiations of dyn Trait need associated types to be specified but only one is provided

• Change powerpc64-ibm-aix default codemodel to large

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.

• Build x86_64-unknown-linux-gnu with LTO for C/C++ code (e.g., jemalloc)

Rust 1.84.1

• Fix ICE 132920 in duplicate-crate diagnostics.
• Fix errors for overlapping impls in incremental rebuilds.
• Fix slow compilation related to the next-generation trait solver.
• Fix debuginfo when LLVM's location discriminator value limit is exceeded.
• Fixes for building Rust from source:
  • Only try to distribute llvm-objcopy if llvm tools are enabled.
  • Add Profile Override for Non-Git Sources.
  • Resolve symlinks of LLVM tool binaries before copying them.
  • Make it possible to use ci-rustc on tarball sources.

Rust 1.84.0

Language

• Allow #[deny] inside #[forbid] as a no-op
• Show a warning when -Ctarget-feature is used to toggle features that can lead to unsoundness due to ABI mismatches
• Use the next-generation trait solver in coherence
• Allow coercions to drop the principal of trait objects
• Support / as the path separator for include!() in all cases on Windows
• Taking a raw ref (raw (const|mut)) of a deref of a pointer (*ptr) is now safe
• Stabilize s390x inline assembly
• Stabilize Arm64EC inline assembly
• Lint against creating pointers to immediately dropped temporaries
• Execute drop glue when unwinding in an extern "C" function

Compiler

• Add --print host-tuple flag to print the host target tuple and affirm the "target tuple" terminology over "target triple"
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• Set up indirect access to external data for loongarch64-unknown-linux-{musl,ohos}
• Enable XRay instrumentation for LoongArch Linux targets
• Extend the unexpected_cfgs lint to also warn in external macros
• Stabilize WebAssembly multivalue, reference-types, and tail-call target features
• Added Tier 2 support for the wasm32v1-none target

Libraries

• Implement From<&mut {slice}> for Box/Rc/Arc<{slice}>
• Move <float>::copysign, <float>::abs, <float>::signum to core
• Add LowerExp and UpperExp implementations to NonZero
• Implement FromStr for CString and TryFrom<CString> for String
• std::os::darwin has been made public

Stabilized APIs

• Ipv6Addr::is_unique_local
• Ipv6Addr::is_unicast_link_local
• core::ptr::with_exposed_provenance
• core::ptr::with_exposed_provenance_mut
• <ptr>::addr
• <ptr>::expose_provenance
• <ptr>::with_addr
• <ptr>::map_addr
• <int>::isqrt
• <int>::checked_isqrt
• <uint>::isqrt
• NonZero::isqrt
• core::ptr::without_provenance
• core::ptr::without_provenance_mut
• core::ptr::dangling
• core::ptr::dangling_mut
• Pin::as_deref_mut

These APIs are now stable in const contexts

• AtomicBool::from_ptr
• AtomicPtr::from_ptr
• AtomicU8::from_ptr
• AtomicU16::from_ptr
• AtomicU32::from_ptr
• AtomicU64::from_ptr
• AtomicUsize::from_ptr
• AtomicI8::from_ptr
• AtomicI16::from_ptr
• AtomicI32::from_ptr
• AtomicI64::from_ptr
• AtomicIsize::from_ptr
• <ptr>::is_null
• <ptr>::as_ref
• <ptr>::as_mut
• Pin::new
• Pin::new_unchecked
• Pin::get_ref
• Pin::into_ref
• Pin::get_mut
• Pin::get_unchecked_mut
• Pin::static_ref
• Pin::static_mut

Cargo

• Stabilize MSRV-aware resolver config
• Stabilize resolver v3

Rustdoc

• rustdoc-search: improve type-driven search

Compatibility Notes

• Enable by default the LSX target feature for LoongArch Linux targets
• The unstable -Zprofile flag (“gcov-style” coverage instrumentation) has been removed. This does not affect the stable flags for coverage instrumentation (-Cinstrument-coverage) and profile-guided optimization (-Cprofile-generate, -Cprofile-use), which are unrelated and remain available.
• Support for the target named wasm32-wasi has been removed as the target is now named wasm32-wasip1. This completes the transition plan for this target following the introduction of wasm32-wasip1 in Rust 1.78. Compiler warnings on use of wasm32-wasi introduced in Rust 1.81 are now gone as well as the target is removed.
• The syntax &pin (mut|const) T is now parsed as a type which in theory could affect macro expansion results in some edge cases
• Legacy syntax for calling std::arch functions is no longer permitted to declare items or bodies (such as closures, inline consts, or async blocks).
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• The next-generation trait solver is now enabled for coherence, fixing multiple soundness issues