Version 1.80.0 (2024-07-25)

Language

• Document maximum allocation size
• Allow zero-byte offsets and ZST read/writes on arbitrary pointers
• Support C23's variadics without a named parameter
• Stabilize exclusive_range_pattern feature
• Guarantee layout and ABI of Result in some scenarios

Compiler

• Update cc crate to v1.0.97 allowing additional spectre mitigations on MSVC targets
• Allow field reordering on types marked repr(packed(1))
• Add a lint against never type fallback affecting unsafe code
• Disallow cast with trailing braced macro in let-else
• Expand for_loops_over_fallibles lint to lint on fallibles behind references.
• self-contained linker: retry linking without -fuse-ld=lld on CCs that don't support it
• Do not parse CVarArgs (...) as a type in trait bounds
• Improvements to LLDB formatting #124458 #124500
• For the wasm32-wasip2 target default to PIC and do not use -fuse-ld=lld
• Add x86_64-unknown-linux-none as a tier 3 target
• Lint on foo.into_iter() resolving to &Box<[T]>: IntoIterator

Libraries

• Add size_of and size_of_val and align_of and align_of_val to the prelude
• Abort a process when FD ownership is violated
• io::Write::write_fmt: panic if the formatter fails when the stream does not fail
• Panic if PathBuf::set_extension would add a path separator
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods
• Update c_char on AIX to use the correct type
• offset_of! no longer returns a temporary
• Handle sigma in str.to_lowercase correctly
• Raise DEFAULT_MIN_STACK_SIZE to at least 64KiB

Stabilized APIs

• impl Default for Rc<CStr>
• impl Default for Rc<str>
• impl Default for Rc<[T]>
• impl Default for Arc<str>
• impl Default for Arc<CStr>
• impl Default for Arc<[T]>
• impl IntoIterator for Box<[T]>
• impl FromIterator<String> for Box<str>
• impl FromIterator<char> for Box<str>
• LazyCell
• LazyLock
• Duration::div_duration_f32
• Duration::div_duration_f64
• Option::take_if
• Seek::seek_relative
• BinaryHeap::as_slice
• NonNull::offset
• NonNull::byte_offset
• NonNull::add
• NonNull::byte_add
• NonNull::sub
• NonNull::byte_sub
• NonNull::offset_from
• NonNull::byte_offset_from
• NonNull::read
• NonNull::read_volatile
• NonNull::read_unaligned
• NonNull::write
• NonNull::write_volatile
• NonNull::write_unaligned
• NonNull::write_bytes
• NonNull::copy_to
• NonNull::copy_to_nonoverlapping
• NonNull::copy_from
• NonNull::copy_from_nonoverlapping
• NonNull::replace
• NonNull::swap
• NonNull::drop_in_place
• NonNull::align_offset
• <[T]>::split_at_checked
• <[T]>::split_at_mut_checked
• str::split_at_checked
• str::split_at_mut_checked
• str::trim_ascii
• str::trim_ascii_start
• str::trim_ascii_end
• <[u8]>::trim_ascii
• <[u8]>::trim_ascii_start
• <[u8]>::trim_ascii_end
• Ipv4Addr::BITS
• Ipv4Addr::to_bits
• Ipv4Addr::from_bits
• Ipv6Addr::BITS
• Ipv6Addr::to_bits
• Ipv6Addr::from_bits
• Vec::<[T; N]>::into_flattened
• <[[T; N]]>::as_flattened
• <[[T; N]]>::as_flattened_mut

These APIs are now stable in const contexts:

• <[T]>::last_chunk
• BinaryHeap::new

Cargo

• Stabilize -Zcheck-cfg as always enabled
• Warn, rather than fail publish, if a target is excluded
• Add special check-cfg lint config for the unexpected_cfgs lint
• Stabilize cargo update --precise <yanked>
• Don't change file permissions on Cargo.toml when using cargo add
• Support using cargo fix on IPv6-only networks

Rustdoc

• Allow searching for references
• Stabilize custom_code_classes_in_docs feature
• fix: In cross-crate scenarios show enum variants on type aliases of enums

Compatibility Notes

• rustfmt estimates line lengths differently when using non-ascii characters
• Type aliases are now handled correctly in orphan check
• Allow instructing rustdoc to read from stdin via -
• std::env::{set_var, remove_var} can no longer be converted to safe function pointers and no longer implement the Fn family of traits
• Warn (or error) when Self constructor from outer item is referenced in inner nested item
• Turn indirect_structural_match and pointer_structural_match lints into hard errors
• Make where_clause_object_safety lint a regular object safety violation
• Turn proc_macro_back_compat lint into a hard error.
• Detect unused structs even when implementing private traits
• std::sync::ReentrantLockGuard<T> is no longer Sync if T: !Sync which means std::io::StdoutLock and std::io::StderrLock are no longer Sync
• Type inference will fail in some cases due to new implementations of FromIterator for Box<str>. Notably, this breaks versions of the time crate before 0.3.35, due to no longer inferring the implementation for Box<[_]>.

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.

• Misc improvements to size of generated html by rustdoc e.g. #124738 and #123734
• MSVC targets no longer depend on libc

Version 1.79.0 (2024-06-13)

Language

• Stabilize inline const {} expressions.
• Prevent opaque types being instantiated twice with different regions within the same function.
• Stabilize WebAssembly target features that are in phase 4 and 5.
• Add the redundant_lifetimes lint to detect lifetimes which are semantically redundant.
• Stabilize the unnameable_types lint for public types that can't be named.
• Enable debuginfo in macros, and stabilize -C collapse-macro-debuginfo and #[collapse_debuginfo].
• Propagate temporary lifetime extension into if and match expressions.
• Restrict promotion of const fn calls.
• Warn against refining impls of crate-private traits with refining_impl_trait lint.
• Stabilize associated type bounds (RFC 2289).
• Stabilize importing main from other modules or crates.
• Check return types of function types for well-formedness
• Rework impl Trait lifetime inference
• Change inductive trait solver cycles to be ambiguous

Compiler

• Define -C strip to only affect binaries, not artifacts like .pdb.
• Stabilize -Crelro-level for controlling runtime link hardening.
• Stabilize checking of cfg names and values at compile-time with --check-cfg. Note that this only stabilizes the compiler part, the Cargo part is still unstable in this release.
• Add aarch64-apple-visionos and aarch64-apple-visionos-sim tier 3 targets.
• Add riscv32ima-unknown-none-elf tier 3 target.
• Promote several Windows targets to tier 2: aarch64-pc-windows-gnullvm, i686-pc-windows-gnullvm, and x86_64-pc-windows-gnullvm.

Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Implement FromIterator for (impl Default + Extend, impl Default + Extend).
• Implement {Div,Rem}Assign<NonZero<X>> on X.
• Document overrides of clone_from() in core/std.
• Link MSVC default lib in core.
• Caution against using transmute between pointers and integers.
• Enable frame pointers for the standard library.

Stabilized APIs

• {integer}::unchecked_add
• {integer}::unchecked_mul
• {integer}::unchecked_sub
• <[T]>::split_at_unchecked
• <[T]>::split_at_mut_unchecked
• <[u8]>::utf8_chunks
• str::Utf8Chunks
• str::Utf8Chunk
• <*const T>::is_aligned
• <*mut T>::is_aligned
• NonNull::is_aligned
• <*const [T]>::len
• <*mut [T]>::len
• <*const [T]>::is_empty
• <*mut [T]>::is_empty
• NonNull::<[T]>::is_empty
• CStr::count_bytes
• io::Error::downcast
• num::NonZero<T>
• path::absolute
• proc_macro::Literal::byte_character
• proc_macro::Literal::c_string

These APIs are now stable in const contexts:

• Atomic*::into_inner
• io::Cursor::new
• io::Cursor::get_ref
• io::Cursor::position
• io::empty
• io::repeat
• io::sink
• panic::Location::caller
• panic::Location::file
• panic::Location::line
• panic::Location::column

Cargo

• Prevent dashes in lib.name, always normalizing to _.
• Stabilize MSRV-aware version requirement selection in cargo add.
• Switch to using gitoxide by default for listing files.

Rustdoc

• Always display stability version even if it's the same as the containing item.
• Show a single search result for items with multiple paths.
• Support typing / in docs to begin a search.

Misc

Compatibility Notes

• Update the minimum external LLVM to 17.
• RustcEncodable and RustcDecodable are soft-destabilized, to be removed from the prelude in next edition.
• The wasm_c_abi future-incompatibility lint will warn about use of the non-spec-compliant C ABI. Use wasm-bindgen v0.2.88 to generate forward-compatible bindings.
• Check return types of function types for well-formedness

Version 1.78.0 (2024-05-02)

Language

• Stabilize #[cfg(target_abi = ...)]
• Stabilize the #[diagnostic] namespace and #[diagnostic::on_unimplemented] attribute
• Make async-fn-in-trait implementable with concrete signatures
• Make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern
• static mut: allow mutable reference to arbitrary types, not just slices and arrays
• Extend invalid_reference_casting to include references casting to bigger memory layout
• Add non_contiguous_range_endpoints lint for singleton gaps after exclusive ranges
• Add wasm_c_abi lint for use of older wasm-bindgen versions This lint currently only works when using Cargo.
• Update indirect_structural_match and pointer_structural_match lints to match RFC
• Make non-PartialEq-typed consts as patterns a hard error
• Split refining_impl_trait lint into _reachable, _internal variants
• Remove unnecessary type inference when using associated types inside of higher ranked where-bounds
• Weaken eager detection of cyclic types during type inference
• trait Trait: Auto {}: allow upcasting from dyn Trait to dyn Trait + Auto

Compiler

• Made INVALID_DOC_ATTRIBUTES lint deny by default
• Increase accuracy of redundant use checking
• Suggest moving definition if non-found macro_rules! is defined later
• Lower transmutes from int to pointer type as gep on null

Target changes:

• Windows tier 1 targets now require at least Windows 10
  • Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows
• Add wasm32-wasip1 tier 2 (without host tools) target
• Add wasm32-wasip2 tier 3 target
• Rename wasm32-wasi-preview1-threads to wasm32-wasip1-threads
• Add arm64ec-pc-windows-msvc tier 3 target
• Add armv8r-none-eabihf tier 3 target for the Cortex-R52
• Add loongarch64-unknown-linux-musl tier 3 target

Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Bump Unicode to version 15.1.0, regenerate tables
• Make align_offset, align_to well-behaved in all cases
• PartialEq, PartialOrd: document expectations for transitive chains
• Optimize away poison guards when std is built with panic=abort
• Replace pthread RwLock with custom implementation
• Implement unwind safety for Condvar on all platforms
• Add ASCII fast-path for char::is_grapheme_extended

Stabilized APIs

• impl Read for &Stdin
• Accept non 'static lifetimes for several std::error::Error related implementations
• Make impl<Fd: AsFd> impl take ?Sized
• impl From<TryReserveError> for io::Error

These APIs are now stable in const contexts:

• Barrier::new()

Cargo

• Stabilize lockfile v4
• Respect rust-version when generating lockfile
• Control --charset via auto-detecting config value
• Support target.<triple>.rustdocflags officially
• Stabilize global cache data tracking

Misc

• rustdoc: add --test-builder-wrapper arg to support wrappers such as RUSTC_WRAPPER when building doctests

Compatibility Notes

• Many unsafe precondition checks now run for user code with debug assertions enabled This change helps users catch undefined behavior in their code, though the details of how much is checked are generally not stable.
• riscv only supports split_debuginfo=off for now
• Consistently check bounds on hidden types of impl Trait
• Change equality of higher ranked types to not rely on subtyping
• When called, additionally check bounds on normalized function return type
• Expand coverage for arithmetic_overflow lint
• Fix detection of potential interior mutability in const initializers This code was accidentally accepted. The fix can break generic code that borrows a value of unknown type, as there is currently no way to declare "this type has no interior mutability". In the future, stabilizing the Freeze trait will allow proper support for such code.

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.

• Update to LLVM 18
• Build rustc with 1CGU on x86_64-pc-windows-msvc
• Build rustc with 1CGU on x86_64-apple-darwin
• Introduce run-make V2 infrastructure, a run_make_support library and port over 2 tests as example
• Windows: Implement condvar, mutex and rwlock using futex

Version 1.77.2 (2024-04-09)

• CVE-2024-24576: fix escaping of Windows batch file arguments in std::process::Command

Version 1.77.1 (2024-03-28)

• 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

Version 1.77.0 (2024-03-21)

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][platform-support-doc] 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.

Version 1.76.0 (2024-02-08)

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][platform-support-doc] 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

Version 1.75.0 (2023-12-28)

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][platform-support-doc] 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.

Version 1.74.1 (2023-12-07)

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

Version 1.74.0 (2023-11-16)

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.

Version 1.73.0 (2023-10-05)

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][platform-support-doc] 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.

Version 1.72.1 (2023-09-19)

• 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

Version 1.72.0 (2023-08-24)

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][platform-support-doc] 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.

Version 1.71.1 (2023-08-03)

• 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

Version 1.71.0 (2023-07-13)

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][platform-support-doc] 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.

Version 1.70.0 (2023-06-01)

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][platform-support-doc] 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

Version 1.69.0 (2023-04-20)

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)

Version 1.68.2 (2023-03-28)

• 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

Version 1.68.1 (2023-03-23)

• 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

Version 1.68.0 (2023-03-09)

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

Version 1.67.1 (2023-02-09)

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

Version 1.67.0 (2023-01-26)

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][platform-support-doc] 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.

Version 1.66.1 (2023-01-10)

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

Version 1.66.0 (2022-12-15)

Language

• Permit specifying explicit discriminants on all repr(Int) enums

  #![allow(unused)]
  fn main() {
  #[repr(u8)]
  enum Foo {
      A(u8) = 0,
      B(i8) = 1,
      C(bool) = 42,
  }
  }

• Allow transmutes between the same type differing only in lifetimes
• Change constant evaluation errors from a deny-by-default lint to a hard error
• Trigger must_use on impl Trait for supertraits This makes impl ExactSizeIterator respect the existing #[must_use] annotation on Iterator.
• Allow ..=X in patterns
• Uplift clippy::for_loops_over_fallibles lint into rustc
• Stabilize sym operands in inline assembly
• Update to Unicode 15
• Opaque types no longer imply lifetime bounds This is a soundness fix which may break code that was erroneously relying on this behavior.

Compiler

• Add armv5te-none-eabi and thumbv5te-none-eabi tier 3 targets
  • Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.
• Add support for linking against macOS universal libraries

Libraries

• Fix #[derive(Default)] on a generic #[default] enum adding unnecessary Default bounds
• Update to Unicode 15

Stabilized APIs

• proc_macro::Span::source_text
• uX::{checked_add_signed, overflowing_add_signed, saturating_add_signed, wrapping_add_signed}
• iX::{checked_add_unsigned, overflowing_add_unsigned, saturating_add_unsigned, wrapping_add_unsigned}
• iX::{checked_sub_unsigned, overflowing_sub_unsigned, saturating_sub_unsigned, wrapping_sub_unsigned}
• BTreeSet::{first, last, pop_first, pop_last}
• BTreeMap::{first_key_value, last_key_value, first_entry, last_entry, pop_first, pop_last}
• Add AsFd implementations for stdio lock types on WASI.
• impl TryFrom<Vec<T>> for Box<[T; N]>
• core::hint::black_box
• Duration::try_from_secs_{f32,f64}
• Option::unzip
• std::os::fd

Rustdoc

• Add Rustdoc warning for invalid HTML tags in the documentation

Cargo

• Added cargo remove to remove dependencies from Cargo.toml
• cargo publish now waits for the new version to be downloadable before exiting

See detailed release notes for more.

Compatibility Notes

• Only apply ProceduralMasquerade hack to older versions of rental
• Don't export __heap_base and __data_end on wasm32-wasi.
• Don't export __wasm_init_memory on WebAssembly.
• Only export __tls_* on wasm32-unknown-unknown.
• Don't link to libresolv in libstd on Darwin
• Update libstd's libc to 0.2.135 (to make libstd no longer pull in libiconv.dylib on Darwin)
• Opaque types no longer imply lifetime bounds This is a soundness fix which may break code that was erroneously relying on this behavior.
• Make order_dependent_trait_objects show up in future-breakage reports
• Change std::process::Command spawning to default to inheriting the parent's signal mask

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.

• Enable BOLT for LLVM compilation
• Enable LTO for rustc_driver.so

Version 1.65.0 (2022-11-03)

Language

• Error on as casts of enums with #[non_exhaustive] variants
• Stabilize let else
• Stabilize generic associated types (GATs)
• Add lints let_underscore_drop and let_underscore_lock from Clippy
• Stabilize breaking from arbitrary labeled blocks ("label-break-value")
• Uninitialized integers, floats, and raw pointers are now considered immediate UB. Usage of MaybeUninit is the correct way to work with uninitialized memory.
• Stabilize raw-dylib for Windows x86_64, aarch64, and thumbv7a
• Do not allow Drop impl on foreign ADTs

Compiler

• Stabilize -Csplit-debuginfo on Linux
• Use niche-filling optimization even when multiple variants have data
• Associated type projections are now verified to be well-formed prior to resolving the underlying type
• Stringify non-shorthand visibility correctly
• Normalize struct field types when unsizing
• Update to LLVM 15
• Fix aarch64 call abi to correctly zeroext when needed
• debuginfo: Generalize C++-like encoding for enums
• Add special_module_name lint
• Add support for generating unique profraw files by default when using -C instrument-coverage
• Allow dynamic linking for iOS/tvOS targets

New targets:

• Add armv4t-none-eabi as a tier 3 target
• Add powerpc64-unknown-openbsd and riscv64-unknown-openbsd as tier 3 targets
  • Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Don't generate PartialEq::ne in derive(PartialEq)
• Windows RNG: Use BCRYPT_RNG_ALG_HANDLE by default
• Forbid mixing System with direct system allocator calls
• Document no support for writing to non-blocking stdio/stderr
• std::layout::Layout size must not overflow isize::MAX when rounded up to align This also changes the safety conditions on Layout::from_size_align_unchecked.

Stabilized APIs

• std::backtrace::Backtrace
• Bound::as_ref
• std::io::read_to_string
• <*const T>::cast_mut
• <*mut T>::cast_const

These APIs are now stable in const contexts:

• <*const T>::offset_from
• <*mut T>::offset_from

Cargo

• Apply GitHub fast path even for partial hashes
• Do not add home bin path to PATH if it's already there
• Take priority into account within the pending queue. This slightly optimizes job scheduling by Cargo, with typically small improvements on larger crate graph builds.

Compatibility Notes

• std::layout::Layout size must not overflow isize::MAX when rounded up to align. This also changes the safety conditions on Layout::from_size_align_unchecked.
• PollFn now only implements Unpin if the closure is Unpin. This is a possible breaking change if users were relying on the blanket unpin implementation. See discussion on the PR for details of why this change was made.
• Drop ExactSizeIterator impl from std::char::EscapeAscii This is a backwards-incompatible change to the standard library's surface area, but is unlikely to affect real world usage.
• Do not consider a single repeated lifetime eligible for elision in the return type This behavior was unintentionally changed in 1.64.0, and this release reverts that change by making this an error again.
• Reenable disabled early syntax gates as future-incompatibility lints
• Update the minimum external LLVM to 13
• Don't duplicate file descriptors into stdio fds
• Sunset RLS
• Deny usage of #![cfg_attr(..., crate_type = ...)] to set the crate type This strengthens the forward compatibility lint deprecated_cfg_attr_crate_type_name to deny.
• llvm-has-rust-patches allows setting the build system to treat the LLVM as having Rust-specific patches This option may need to be set for distributions that are building Rust with a patched LLVM via llvm-config, not the built-in LLVM.
• Combining three or more languages (e.g. Objective C, C++ and Rust) into one binary may hit linker limitations when using lld. For more information, see issue 102754.

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 x.sh and x.ps1 shell scripts
• compiletest: use target cfg instead of hard-coded tables
• Use object instead of LLVM for reading bitcode from rlibs
• Enable MIR inlining for optimized compilations This provides a 3-10% improvement in compiletimes for real world crates. See perf results.

Version 1.64.0 (2022-09-22)

Language

• Unions with mutable references or tuples of allowed types are now allowed
• It is now considered valid to deallocate memory pointed to by a shared reference &T if every byte in T is inside an UnsafeCell
• Unused tuple struct fields are now warned against in an allow-by-default lint, unused_tuple_struct_fields, similar to the existing warning for unused struct fields. This lint will become warn-by-default in the future.

Compiler

• Add Nintendo Switch as tier 3 target
  • Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.
• Only compile #[used] as llvm.compiler.used for ELF targets
• Add the --diagnostic-width compiler flag to define the terminal width.
• Add support for link-flavor rust-lld for iOS, tvOS and watchOS

Libraries

• Remove restrictions on compare-exchange memory ordering.
• You can now write! or writeln! into an OsString: Implement fmt::Write for OsString
• Make RwLockReadGuard covariant
• Implement FusedIterator for std::net::[Into]Incoming
• impl<T: AsRawFd> AsRawFd for {Arc,Box}<T>
• ptr::copy and ptr::swap are doing untyped copies
• Add cgroupv1 support to available_parallelism
• Mitigate many incorrect uses of mem::uninitialized

Stabilized APIs

• future::IntoFuture
• future::poll_fn
• task::ready!
• num::NonZero*::checked_mul
• num::NonZero*::checked_pow
• num::NonZero*::saturating_mul
• num::NonZero*::saturating_pow
• num::NonZeroI*::abs
• num::NonZeroI*::checked_abs
• num::NonZeroI*::overflowing_abs
• num::NonZeroI*::saturating_abs
• num::NonZeroI*::unsigned_abs
• num::NonZeroI*::wrapping_abs
• num::NonZeroU*::checked_add
• num::NonZeroU*::checked_next_power_of_two
• num::NonZeroU*::saturating_add
• os::unix::process::CommandExt::process_group
• os::windows::fs::FileTypeExt::is_symlink_dir
• os::windows::fs::FileTypeExt::is_symlink_file

These types were previously stable in std::ffi, but are now also available in core and alloc:

• core::ffi::CStr
• core::ffi::FromBytesWithNulError
• alloc::ffi::CString
• alloc::ffi::FromVecWithNulError
• alloc::ffi::IntoStringError
• alloc::ffi::NulError

These types were previously stable in std::os::raw, but are now also available in core::ffi and std::ffi:

• ffi::c_char
• ffi::c_double
• ffi::c_float
• ffi::c_int
• ffi::c_long
• ffi::c_longlong
• ffi::c_schar
• ffi::c_short
• ffi::c_uchar
• ffi::c_uint
• ffi::c_ulong
• ffi::c_ulonglong
• ffi::c_ushort

These APIs are now usable in const contexts:

• slice::from_raw_parts

Cargo

• Packages can now inherit settings from the workspace so that the settings can be centralized in one place. See workspace.package and workspace.dependencies for more details on how to define these common settings.
• Cargo commands can now accept multiple --target flags to build for multiple targets at once, and the build.target config option may now take an array of multiple targets.
• The --jobs argument can now take a negative number to count backwards from the max CPUs.
• cargo add will now update Cargo.lock.
• Added the --crate-type flag to cargo rustc to override the crate type.
• Significantly improved the performance fetching git dependencies from GitHub when using a hash in the rev field.

Misc

• The rust-analyzer rustup component is now available on the stable channel.

Compatibility Notes

• The minimum required versions for all -linux-gnu targets are now at least kernel 3.2 and glibc 2.17, for targets that previously supported older versions: Increase the minimum linux-gnu versions
• Network primitives are now implemented with the ideal Rust layout, not the C system layout. This can cause problems when transmuting the types.
• Add assertion that transmute_copy's U is not larger than T
• A soundness bug in BTreeMap was fixed that allowed data it was borrowing to be dropped before the container.
• The Drop behavior of C-like enums cast to ints has changed. These are already discouraged by a compiler warning.
• Relate late-bound closure lifetimes to parent fn in NLL
• Errors at const-eval time are now in future incompatibility reports
• On the thumbv6m-none-eabi target, some incorrect asm! statements were erroneously accepted if they used the high registers (r8 to r14) as an input/output operand. This is no longer accepted.
• impl Trait was accidentally accepted as the associated type value of return-position impl Trait, without fulfilling all the trait bounds of that associated type, as long as the hidden type satisfies said bounds. This has been fixed.

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.

• Windows builds now use profile-guided optimization, providing 10-20% improvements to compiler performance: Utilize PGO for windows x64 rustc dist builds
• Stop keeping metadata in memory before writing it to disk
• compiletest: strip debuginfo by default for mode=ui
• Many improvements to generated code for derives, including performance improvements:
  • Don't use match-destructuring for derived ops on structs.
  • Many small deriving cleanups
  • More derive output improvements
  • Clarify deriving code
  • Final derive output improvements
  • Stop injecting #[allow(unused_qualifications)] in generated derive implementations
  • Improve derive(Debug)
• Bump to clap 3
• fully move dropck to mir
• Optimize Vec::insert for the case where index == len.
• Convert rust-analyzer to an in-tree tool

Version 1.63.0 (2022-08-11)

Language

• Remove migrate borrowck mode for pre-NLL errors.
• Modify MIR building to drop repeat expressions with length zero.
• Remove label/lifetime shadowing warnings.
• Allow explicit generic arguments in the presence of impl Trait args.
• Make cenum_impl_drop_cast warnings deny-by-default.
• Prevent unwinding when -C panic=abort is used regardless of declared ABI.
• lub: don't bail out due to empty binders.

Compiler

• Stabilize the bundle native library modifier, also removing the deprecated static-nobundle linking kind.
• Add Apple WatchOS compile targets*.
• Add a Windows application manifest to rustc-main.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Implement Copy, Clone, PartialEq and Eq for core::fmt::Alignment.
• Extend ptr::null and null_mut to all thin (including extern) types.
• impl Read and Write for VecDeque<u8>.
• STD support for the Nintendo 3DS.
• Use rounding in float to Duration conversion methods.
• Make write/print macros eagerly drop temporaries.
• Implement internal traits that enable [OsStr]::join.
• Implement Hash for core::alloc::Layout.
• Add capacity documentation for OsString.
• Put a bound on collection misbehavior.
• Make std::mem::needs_drop accept ?Sized.
• impl Termination for Infallible and then make the Result impls of Termination more generic.
• Document Rust's stance on /proc/self/mem.

Stabilized APIs

• array::from_fn
• Box::into_pin
• BinaryHeap::try_reserve
• BinaryHeap::try_reserve_exact
• OsString::try_reserve
• OsString::try_reserve_exact
• PathBuf::try_reserve
• PathBuf::try_reserve_exact
• Path::try_exists
• Ref::filter_map
• RefMut::filter_map
• NonNull::<[T]>::len
• ToOwned::clone_into
• Ipv6Addr::to_ipv4_mapped
• unix::io::AsFd
• unix::io::BorrowedFd<'fd>
• unix::io::OwnedFd
• windows::io::AsHandle
• windows::io::BorrowedHandle<'handle>
• windows::io::OwnedHandle
• windows::io::HandleOrInvalid
• windows::io::HandleOrNull
• windows::io::InvalidHandleError
• windows::io::NullHandleError
• windows::io::AsSocket
• windows::io::BorrowedSocket<'handle>
• windows::io::OwnedSocket
• thread::scope
• thread::Scope
• thread::ScopedJoinHandle

These APIs are now usable in const contexts:

• array::from_ref
• slice::from_ref
• intrinsics::copy
• intrinsics::copy_nonoverlapping
• <*const T>::copy_to
• <*const T>::copy_to_nonoverlapping
• <*mut T>::copy_to
• <*mut T>::copy_to_nonoverlapping
• <*mut T>::copy_from
• <*mut T>::copy_from_nonoverlapping
• str::from_utf8
• Utf8Error::error_len
• Utf8Error::valid_up_to
• Condvar::new
• Mutex::new
• RwLock::new

Cargo

• Stabilize the --config path command-line argument.
• Expose rust-version in the environment as CARGO_PKG_RUST_VERSION.

Compatibility Notes

• #[link] attributes are now checked more strictly, which may introduce errors for invalid attribute arguments that were previously ignored.
• Rounding is now used when converting a float to a Duration. The converted duration can differ slightly from what it was.

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Prepare Rust for LLVM opaque pointers.

Version 1.62.1 (2022-07-19)

Rust 1.62.1 addresses a few recent regressions in the compiler and standard library, and also mitigates a CPU vulnerability on Intel SGX.

• The compiler fixed unsound function coercions involving impl Trait return types.
• The compiler fixed an incremental compilation bug with async fn lifetimes.
• Windows added a fallback for overlapped I/O in synchronous reads and writes.
• The x86_64-fortanix-unknown-sgx target added a mitigation for the MMIO stale data vulnerability, advisory INTEL-SA-00615.

Version 1.62.0 (2022-06-30)

Language

• Stabilize #[derive(Default)] on enums with a #[default] variant
• Teach flow sensitive checks that visibly uninhabited call expressions never return
• Fix constants not getting dropped if part of a diverging expression
• Support unit struct/enum variant in destructuring assignment
• Remove mutable_borrow_reservation_conflict lint and allow the code pattern
• const functions may now specify extern "C" or extern "Rust"

Compiler

• linker: Stop using whole-archive on dependencies of dylibs
• Make unaligned_references lint deny-by-default This lint is also a future compatibility lint, and is expected to eventually become a hard error.
• Only add codegen backend to dep info if -Zbinary-dep-depinfo is used
• Reject #[thread_local] attribute on non-static items
• Add tier 3 aarch64-pc-windows-gnullvm and x86_64-pc-windows-gnullvm targets*
• Implement a lint to warn about unused macro rules
• Promote x86_64-unknown-none target to Tier 2*

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Windows: Use a pipe relay for chaining pipes
• Replace Linux Mutex and Condvar with futex based ones.
• Replace RwLock by a futex based one on Linux
• std: directly use pthread in UNIX parker implementation

Stabilized APIs

• bool::then_some
• f32::total_cmp
• f64::total_cmp
• Stdin::lines
• windows::CommandExt::raw_arg
• impl<T: Default> Default for AssertUnwindSafe<T>
• From<Rc<str>> for Rc<[u8]>
• From<Arc<str>> for Arc<[u8]>
• FusedIterator for EncodeWide
• RDM intrinsics on aarch64

Clippy

• Create clippy lint against unexpectedly late drop for temporaries in match scrutinee expressions

Cargo

• Added the cargo add command for adding dependencies to Cargo.toml from the command-line. docs
• Package ID specs now support name@version syntax in addition to the previous name:version to align with the behavior in cargo add and other tools. cargo install and cargo yank also now support this syntax so the version does not need to passed as a separate flag.
• The git and registry directories in Cargo's home directory (usually ~/.cargo) are now marked as cache directories so that they are not included in backups or content indexing (on Windows).
• Added automatic @ argfile support, which will use "response files" if the command-line to rustc exceeds the operating system's limit.

Compatibility Notes

• cargo test now passes --target to rustdoc if the specified target is the same as the host target. #10594
• rustdoc: doctests are now run on unexported macro_rules! macros, matching other private items
• rustdoc: Remove .woff font files
• Enforce Copy bounds for repeat elements while considering lifetimes
• Windows: Fix potential unsoundness by aborting if File reads or writes cannot complete synchronously.

Internal Changes

• Unify ReentrantMutex implementations across all platforms

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

Version 1.61.0 (2022-05-19)

Language

• const fn signatures can now include generic trait bounds
• const fn signatures can now use impl Trait in argument and return position
• Function pointers can now be created, cast, and passed around in a const fn
• Recursive calls can now set the value of a function's opaque impl Trait return type

Compiler

• Linking modifier syntax in #[link] attributes and on the command line, as well as the whole-archive modifier specifically, are now supported
• The char type is now described as UTF-32 in debuginfo
• The #[target_feature] attribute can now be used with aarch64 features
• X86 #[target_feature = "adx"] is now stable

Libraries

• ManuallyDrop<T> is now documented to have the same layout as T
• #[ignore = "…"] messages are printed when running tests
• Consistently show absent stdio handles on Windows as NULL handles
• Make std::io::stdio::lock() return 'static handles. Previously, the creation of locked handles to stdin/stdout/stderr would borrow the handles being locked, which prevented writing let out = std::io::stdout().lock(); because out would outlive the return value of stdout(). Such code now works, eliminating a common pitfall that affected many Rust users.
• Vec::from_raw_parts is now less restrictive about its inputs
• std::thread::available_parallelism now takes cgroup quotas into account. Since available_parallelism is often used to create a thread pool for parallel computation, which may be CPU-bound for performance, available_parallelism will return a value consistent with the ability to use that many threads continuously, if possible. For instance, in a container with 8 virtual CPUs but quotas only allowing for 50% usage, available_parallelism will return 4.

Stabilized APIs

• Pin::static_mut
• Pin::static_ref
• Vec::retain_mut
• VecDeque::retain_mut
• Write for Cursor<[u8; N]>
• std::os::unix::net::SocketAddr::from_pathname
• std::process::ExitCode and std::process::Termination. The stabilization of these two APIs now makes it possible for programs to return errors from main with custom exit codes.
• std::thread::JoinHandle::is_finished

These APIs are now usable in const contexts:

• <*const T>::offset and <*mut T>::offset
• <*const T>::wrapping_offset and <*mut T>::wrapping_offset
• <*const T>::add and <*mut T>::add
• <*const T>::sub and <*mut T>::sub
• <*const T>::wrapping_add and <*mut T>::wrapping_add
• <*const T>::wrapping_sub and <*mut T>::wrapping_sub
• <[T]>::as_mut_ptr
• <[T]>::as_ptr_range
• <[T]>::as_mut_ptr_range

Cargo

No feature changes, but see compatibility notes.

Compatibility Notes

• Previously native static libraries were linked as whole-archive in some cases, but now rustc tries not to use whole-archive unless explicitly requested. This change may result in linking errors in some cases. To fix such errors, native libraries linked from the command line, build scripts, or #[link] attributes need to
  • (more common) either be reordered to respect dependencies between them (if a depends on b then a should go first and b second)
  • (less common) or be updated to use the +whole-archive modifier.
• Catching a second unwind from FFI code while cleaning up from a Rust panic now causes the process to abort
• Proc macros no longer see ident matchers wrapped in groups
• The number of # in r# raw string literals is now required to be less than 256
• When checking that a dyn type satisfies a trait bound, supertrait bounds are now enforced
• cargo vendor now only accepts one value for each --sync flag
• cfg predicates in all() and any() are always evaluated to detect errors, instead of short-circuiting. The compatibility considerations here arise in nightly-only code that used the short-circuiting behavior of all to write something like cfg(all(feature = "nightly", syntax-requiring-nightly)), which will now fail to compile. Instead, use either cfg_attr(feature = "nightly", ...) or nested uses of cfg.
• bootstrap: static-libstdcpp is now enabled by default, and can now be disabled when llvm-tools is enabled

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• debuginfo: Refactor debuginfo generation for types
• Remove the everybody loops pass

Version 1.60.0 (2022-04-07)

Language

• Stabilize #[cfg(panic = "...")] for either "unwind" or "abort".
• Stabilize #[cfg(target_has_atomic = "...")] for each integer size and "ptr".

Compiler

• Enable combining +crt-static and relocation-model=pic on x86_64-unknown-linux-gnu
• Fixes wrong unreachable_pub lints on nested and glob public reexport
• Stabilize -Z instrument-coverage as -C instrument-coverage
• Stabilize -Z print-link-args as --print link-args
• Add new Tier 3 target mips64-openwrt-linux-musl*
• Add new Tier 3 target armv7-unknown-linux-uclibceabi (softfloat)*
• Fix invalid removal of newlines from doc comments
• Add kernel target for RustyHermit
• Deny mixing bin crate type with lib crate types
• Make rustc use RUST_BACKTRACE=full by default
• Upgrade to LLVM 14

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Guarantee call order for sort_by_cached_key
• Improve Duration::try_from_secs_f32/f64 accuracy by directly processing exponent and mantissa
• Make Instant::{duration_since, elapsed, sub} saturating
• Remove non-monotonic clocks workarounds in Instant::now
• Make BuildHasherDefault, iter::Empty and future::Pending covariant

Stabilized APIs

• Arc::new_cyclic
• Rc::new_cyclic
• slice::EscapeAscii
• <[u8]>::escape_ascii
• u8::escape_ascii
• Vec::spare_capacity_mut
• MaybeUninit::assume_init_drop
• MaybeUninit::assume_init_read
• i8::abs_diff
• i16::abs_diff
• i32::abs_diff
• i64::abs_diff
• i128::abs_diff
• isize::abs_diff
• u8::abs_diff
• u16::abs_diff
• u32::abs_diff
• u64::abs_diff
• u128::abs_diff
• usize::abs_diff
• Display for io::ErrorKind
• From<u8> for ExitCode
• Not for ! (the "never" type)
• OpAssign<$t> for Wrapping<$t>
• arch::is_aarch64_feature_detected!

Cargo

• Port cargo from toml-rs to toml_edit
• Stabilize -Ztimings as --timings
• Stabilize namespaced and weak dependency features.
• Accept more cargo:rustc-link-arg-* types from build script output.
• cargo-new should not add ignore rule on Cargo.lock inside subdirs

Misc

• Ship docs on Tier 2 platforms by reusing the closest Tier 1 platform docs
• Drop rustc-docs from complete profile
• bootstrap: tidy up flag handling for llvm build

Compatibility Notes

• Remove compiler-rt linking hack on Android
• Mitigations for platforms with non-monotonic clocks have been removed from Instant::now. On platforms that don't provide monotonic clocks, an instant is not guaranteed to be greater than an earlier instant anymore.
• Instant::{duration_since, elapsed, sub} do not panic anymore on underflow, saturating to 0 instead. In the real world the panic happened mostly on platforms with buggy monotonic clock implementations rather than catching programming errors like reversing the start and end times. Such programming errors will now results in 0 rather than a panic.
• In a future release we're planning to increase the baseline requirements for the Linux kernel to version 3.2, and for glibc to version 2.17. We'd love your feedback in PR #95026.

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Switch all libraries to the 2021 edition

Version 1.59.0 (2022-02-24)

Language

• Stabilize default arguments for const parameters and remove the ordering restriction for type and const parameters
• Stabilize destructuring assignment
• Relax private in public lint on generic bounds and where clauses of trait impls
• Stabilize asm! and global_asm! for x86, x86_64, ARM, Aarch64, and RISC-V

Compiler

• Stabilize new symbol mangling format, leaving it opt-in (-Csymbol-mangling-version=v0)
• Emit LLVM optimization remarks when enabled with -Cremark
• Fix sparc64 ABI for aggregates with floating point members
• Warn when a #[test]-like built-in attribute macro is present multiple times.
• Add support for riscv64gc-unknown-freebsd
• Stabilize -Z emit-future-incompat as --json future-incompat
• Soft disable incremental compilation

This release disables incremental compilation, unless the user has explicitly opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable. This is due to a known and relatively frequently occurring bug in incremental compilation, which causes builds to issue internal compiler errors. This particular bug is already fixed on nightly, but that fix has not yet rolled out to stable and is deemed too risky for a direct stable backport.

As always, we encourage users to test with nightly and report bugs so that we can track failures and fix issues earlier.

See 94124 for more details.

Libraries

• Remove unnecessary bounds for some Hash{Map,Set} methods

Stabilized APIs

• std::thread::available_parallelism
• Result::copied
• Result::cloned
• arch::asm!
• arch::global_asm!
• ops::ControlFlow::is_break
• ops::ControlFlow::is_continue
• TryFrom<char> for u8
• char::TryFromCharError implementing Clone, Debug, Display, PartialEq, Copy, Eq, Error
• iter::zip
• NonZeroU8::is_power_of_two
• NonZeroU16::is_power_of_two
• NonZeroU32::is_power_of_two
• NonZeroU64::is_power_of_two
• NonZeroU128::is_power_of_two
• NonZeroUsize::is_power_of_two
• DoubleEndedIterator for ToLowercase
• DoubleEndedIterator for ToUppercase
• TryFrom<&mut [T]> for [T; N]
• UnwindSafe for Once
• RefUnwindSafe for Once
• armv8 neon intrinsics for aarch64

Const-stable:

• mem::MaybeUninit::as_ptr
• mem::MaybeUninit::assume_init
• mem::MaybeUninit::assume_init_ref
• ffi::CStr::from_bytes_with_nul_unchecked

Cargo

• Stabilize the strip profile option
• Stabilize future-incompat-report
• Support abbreviating --release as -r
• Support term.quiet configuration
• Remove --host from cargo {publish,search,login}

Compatibility Notes

• Refactor weak symbols in std::sys::unix This may add new, versioned, symbols when building with a newer glibc, as the standard library uses weak linkage rather than dynamically attempting to load certain symbols at runtime.
• Deprecate crate_type and crate_name nested inside #![cfg_attr] This adds a future compatibility lint to supporting the use of cfg_attr wrapping either crate_type or crate_name specification within Rust files; it is recommended that users migrate to setting the equivalent command line flags.
• Remove effect of #[no_link] attribute on name resolution This may expose new names, leading to conflicts with preexisting names in a given namespace and a compilation failure.
• Cargo will document libraries before binaries.
• Respect doc=false in dependencies, not just the root crate
• Weaken guarantee around advancing underlying iterators in zip
• Make split_inclusive() on an empty slice yield an empty output
• Update std::env::temp_dir to use GetTempPath2 on Windows when available.
• unreachable! was updated to match other formatting macro behavior on Rust 2021

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Fix many cases of normalization-related ICEs

• Replace dominators algorithm with simple Lengauer-Tarjan

• Store liveness in interval sets for region inference

• Remove in_band_lifetimes from the compiler and standard library, in preparation for removing this unstable feature.

Version 1.58.1 (2022-01-20)

• Fix race condition in std::fs::remove_dir_all (CVE-2022-21658)
• Handle captured arguments in the useless_format Clippy lint
• Move non_send_fields_in_send_ty Clippy lint to nursery
• Fix wrong error message displayed when some imports are missing
• Fix rustfmt not formatting generated files from stdin

Version 1.58.0 (2022-01-13)

Language

• Format strings can now capture arguments simply by writing {ident} in the string. This works in all macros accepting format strings. Support for this in panic! (panic!("{ident}")) requires the 2021 edition; panic invocations in previous editions that appear to be trying to use this will result in a warning lint about not having the intended effect.
• *const T pointers can now be dereferenced in const contexts.
• The rules for when a generic struct implements Unsize have been relaxed.

Compiler

• Add LLVM CFI support to the Rust compiler
• Stabilize -Z strip as -C strip. Note that while release builds already don't add debug symbols for the code you compile, the compiled standard library that ships with Rust includes debug symbols, so you may want to use the strip option to remove these symbols to produce smaller release binaries. Note that this release only includes support in rustc, not directly in cargo.
• Add support for LLVM coverage mapping format versions 5 and 6
• Emit LLVM optimization remarks when enabled with -Cremark
• Update the minimum external LLVM to 12
• Add x86_64-unknown-none at Tier 3*
• Build musl dist artifacts with debuginfo enabled. When building release binaries using musl, you may want to use the newly stabilized strip option to remove these debug symbols, reducing the size of your binaries.
• Don't abort compilation after giving a lint error
• Error messages point at the source of trait bound obligations in more places

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• [All remaining functions in the standard library have #[must_use] annotations where appropriate][89692], producing a warning when ignoring their return value. This helps catch mistakes such as expecting a function to mutate a value in place rather than return a new value.
• Paths are automatically canonicalized on Windows for operations that support it
• Re-enable debug checks for copy and copy_nonoverlapping
• Implement RefUnwindSafe for Rc<T>
• Make RSplit<T, P>: Clone not require T: Clone
• Implement Termination for Result<Infallible, E>. This allows writing fn main() -> Result<Infallible, ErrorType>, for a program whose successful exits never involve returning from main (for instance, a program that calls exit, or that uses exec to run another program).

Stabilized APIs

• Metadata::is_symlink
• Path::is_symlink
• {integer}::saturating_div
• Option::unwrap_unchecked
• Result::unwrap_unchecked
• Result::unwrap_err_unchecked
• File::options

These APIs are now usable in const contexts:

• Duration::new
• [Duration::checked_add]
• [Duration::saturating_add]
• [Duration::checked_sub]
• [Duration::saturating_sub]
• [Duration::checked_mul]
• [Duration::saturating_mul]
• [Duration::checked_div]

Cargo

• Add --message-format for install command
• Warn when alias shadows external subcommand

Rustdoc

• Show all Deref implementations recursively in rustdoc
• Use computed visibility in rustdoc

Compatibility Notes

• Try all stable method candidates first before trying unstable ones. This change ensures that adding new nightly-only methods to the Rust standard library will not break code invoking methods of the same name from traits outside the standard library.
• Windows: std::process::Command will no longer search the current directory for executables.
• All proc-macro backward-compatibility lints are now deny-by-default.
• proc_macro: Append .0 to unsuffixed float if it would otherwise become int token
• Refactor weak symbols in std::sys::unix. This optimizes accesses to glibc functions, by avoiding the use of dlopen. This does not increase the minimum expected version of glibc. However, software distributions that use symbol versions to detect library dependencies, and which take weak symbols into account in that analysis, may detect rust binaries as requiring newer versions of glibc.
• rustdoc now rejects some unexpected semicolons in doctests

Internal Changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Implement coherence checks for negative trait impls
• Add rustc lint, warning when iterating over hashmaps
• Optimize live point computation
• Enable verification for 1/32nd of queries loaded from disk
• Implement version of normalize_erasing_regions that allows for normalization failure

Version 1.57.0 (2021-12-02)

Language

• Macro attributes may follow #[derive] and will see the original (pre-cfg) input.
• Accept curly-brace macros in expressions, like m!{ .. }.method() and m!{ .. }?.
• Allow panicking in constant evaluation.
• Ignore derived Clone and Debug implementations during dead code analysis.

Compiler

• Create more accurate debuginfo for vtables.
• Add armv6k-nintendo-3ds at Tier 3*.
• Add armv7-unknown-linux-uclibceabihf at Tier 3*.
• Add m68k-unknown-linux-gnu at Tier 3*.
• Add SOLID targets at Tier 3*: aarch64-kmc-solid_asp3, armv7a-kmc-solid_asp3-eabi, armv7a-kmc-solid_asp3-eabihf

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Avoid allocations and copying in Vec::leak
• Add #[repr(i8)] to Ordering
• Optimize File::read_to_end and read_to_string
• Update to Unicode 14.0
• Many more functions are marked #[must_use], producing a warning when ignoring their return value. This helps catch mistakes such as expecting a function to mutate a value in place rather than return a new value.

Stabilised APIs

• [T; N]::as_mut_slice
• [T; N]::as_slice
• collections::TryReserveError
• HashMap::try_reserve
• HashSet::try_reserve
• String::try_reserve
• String::try_reserve_exact
• Vec::try_reserve
• Vec::try_reserve_exact
• VecDeque::try_reserve
• VecDeque::try_reserve_exact
• Iterator::map_while
• iter::MapWhile
• proc_macro::is_available
• Command::get_program
• Command::get_args
• Command::get_envs
• Command::get_current_dir
• CommandArgs
• CommandEnvs

These APIs are now usable in const contexts:

• [hint::unreachable_unchecked]

Cargo

• Stabilize custom profiles

Compatibility notes

• Ignore derived Clone and Debug implementations during dead code analysis. This will break some builds that set #![deny(dead_code)].

Internal changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Added an experimental backend for codegen with libgccjit.

Version 1.56.1 (2021-11-01)

• New lints to detect the presence of bidirectional-override Unicode codepoints in the compiled source code (CVE-2021-42574)

Version 1.56.0 (2021-10-21)

Language

• The 2021 Edition is now stable. See the edition guide for more details.
• The pattern in binding @ pattern can now also introduce new bindings.
• Union field access is permitted in const fn.

Compiler

• Upgrade to LLVM 13.
• Support memory, address, and thread sanitizers on aarch64-unknown-freebsd.
• Allow specifying a deployment target version for all iOS targets
• Warnings can be forced on with --force-warn. This feature is primarily intended for usage by cargo fix, rather than end users.
• Promote aarch64-apple-ios-sim to Tier 2*.
• Add powerpc-unknown-freebsd at Tier 3*.
• Add riscv32imc-esp-espidf at Tier 3*.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Allow writing of incomplete UTF-8 sequences via stdout/stderr on Windows. The Windows console still requires valid Unicode, but this change allows splitting a UTF-8 character across multiple write calls. This allows, for instance, programs that just read and write data buffers (e.g. copying a file to stdout) without regard for Unicode or character boundaries.
• Prefer AtomicU{64,128} over Mutex for Instant backsliding protection. For this use case, atomics scale much better under contention.
• Implement Extend<(A, B)> for (Extend<A>, Extend<B>)
• impl Default, Copy, Clone for std::io::Sink and std::io::Empty
• impl From<[(K, V); N]> for all collections.
• Remove P: Unpin bound on impl Future for Pin.
• Treat invalid environment variable names as nonexistent. Previously, the environment functions would panic if given a variable name with an internal null character or equal sign (=). Now, these functions will just treat such names as nonexistent variables, since the OS cannot represent the existence of a variable with such a name.

Stabilised APIs

• std::os::unix::fs::chroot
• UnsafeCell::raw_get
• BufWriter::into_parts
• core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe} These APIs were previously stable in std, but are now also available in core.
• Vec::shrink_to
• String::shrink_to
• OsString::shrink_to
• PathBuf::shrink_to
• BinaryHeap::shrink_to
• VecDeque::shrink_to
• HashMap::shrink_to
• HashSet::shrink_to

These APIs are now usable in const contexts:

• std::mem::transmute
• [T]::first
• [T]::split_first
• [T]::last
• [T]::split_last

Cargo

• Cargo supports specifying a minimum supported Rust version in Cargo.toml. This has no effect at present on dependency version selection. We encourage crates to specify their minimum supported Rust version, and we encourage CI systems that support Rust code to include a crate's specified minimum version in the test matrix for that crate by default.

Compatibility notes

• Update to new argument parsing rules on Windows. This adjusts Rust's standard library to match the behavior of the standard libraries for C/C++. The rules have changed slightly over time, and this PR brings us to the latest set of rules (changed in 2008).
• Disallow the aapcs calling convention on aarch64 This was already not supported by LLVM; this change surfaces this lack of support with a better error message.
• Make SEMICOLON_IN_EXPRESSIONS_FROM_MACROS warn by default
• Warn when an escaped newline skips multiple lines.
• Calls to libc::getpid / std::process::id from Command::pre_exec may return different values on glibc <= 2.24. Rust now invokes the clone3 system call directly, when available, to use new functionality available via that system call. Older versions of glibc cache the result of getpid, and only update that cache when calling glibc's clone/fork functions, so a direct system call bypasses that cache update. glibc 2.25 and newer no longer cache getpid for exactly this reason.

Internal changes

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• LLVM is compiled with PGO in published x86_64-unknown-linux-gnu artifacts. This improves the performance of most Rust builds.
• Unify representation of macros in internal data structures. This change fixes a host of bugs with the handling of macros by the compiler, as well as rustdoc.

Version 1.55.0 (2021-09-09)

Language

• You can now write open "from" range patterns (X..), which will start at X and will end at the maximum value of the integer.
• You can now explicitly import the prelude of different editions through std::prelude (e.g. use std::prelude::rust_2021::*;).

Compiler

• Added tier 3* support for powerpc64le-unknown-freebsd.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Updated std's float parsing to use the Eisel-Lemire algorithm. These improvements should in general provide faster string parsing of floats, no longer reject certain valid floating point values, and reduce the produced code size for non-stripped artifacts.
• string::Drain now implements AsRef<str> and AsRef<[u8]>.

Stabilised APIs

• Bound::cloned
• Drain::as_str
• IntoInnerError::into_error
• IntoInnerError::into_parts
• MaybeUninit::assume_init_mut
• MaybeUninit::assume_init_ref
• MaybeUninit::write
• array::map
• ops::ControlFlow
• x86::_bittest
• x86::_bittestandcomplement
• x86::_bittestandreset
• x86::_bittestandset
• x86_64::_bittest64
• x86_64::_bittestandcomplement64
• x86_64::_bittestandreset64
• x86_64::_bittestandset64

The following previously stable functions are now const.

• str::from_utf8_unchecked

Cargo

• Cargo will now deduplicate compiler diagnostics to the terminal when invoking rustc in parallel such as when using cargo test.
• The package definition in cargo metadata now includes the "default_run" field from the manifest.
• Added cargo d as an alias for cargo doc.
• Added {lib} as formatting option for cargo tree to print the "lib_name" of packages.

Rustdoc

• Added "Go to item on exact match" search option.
• The "Implementors" section on traits no longer shows redundant method definitions.
• Trait implementations are toggled open by default. This should make the implementations more searchable by tools like CTRL+F in your browser.
• Intra-doc links should now correctly resolve associated items (e.g. methods) through type aliases.
• Traits which are marked with #[doc(hidden)] will no longer appear in the "Trait Implementations" section.

Compatibility Notes

• std functions that return an io::Error will no longer use the ErrorKind::Other variant. This is to better reflect that these kinds of errors could be categorised into newer more specific ErrorKind variants, and that they do not represent a user error.
• Using environment variable names with process::Command on Windows now behaves as expected. Previously using environment variables with Command would cause them to be ASCII-uppercased.
• Rustdoc will now warn on using rustdoc lints that aren't prefixed with rustdoc::
• RUSTFLAGS is no longer set for build scripts. Build scripts should use CARGO_ENCODED_RUSTFLAGS instead. See the documentation for more details.

Version 1.54.0 (2021-07-29)

Language

• You can now use macros for values in some built-in attributes. This primarily allows you to call macros within the #[doc] attribute. For example, to include external documentation in your crate, you can now write the following:

  #![allow(unused)]
  #![doc = include_str!("README.md")]
  fn main() {
  }

• You can now cast between unsized slice types (and types which contain unsized slices) in const fn.

• You can now use multiple generic lifetimes with impl Trait where the lifetimes don't explicitly outlive another. In code this means that you can now have impl Trait<'a, 'b> where as before you could only have impl Trait<'a, 'b> where 'b: 'a.

Compiler

• Rustc will now search for custom JSON targets in /lib/rustlib/<target-triple>/target.json where / is the "sysroot" directory. You can find your sysroot directory by running rustc --print sysroot.
• Added wasm as a target_family for WebAssembly platforms.
• You can now use #[target_feature] on safe functions when targeting WebAssembly platforms.
• Improved debugger output for enums on Windows MSVC platforms.
• Added tier 3* support for bpfel-unknown-none and bpfeb-unknown-none.
• -Zmutable-noalias=yes is enabled by default when using LLVM 12 or above.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• panic::panic_any will now #[track_caller].
• Added OutOfMemory as a variant of io::ErrorKind.
• proc_macro::Literal now implements FromStr.
• The implementations of vendor intrinsics in core::arch have been significantly refactored. The main user-visible changes are a 50% reduction in the size of libcore.rlib and stricter validation of constant operands passed to intrinsics. The latter is technically a breaking change, but allows Rust to more closely match the C vendor intrinsics API.

Stabilized APIs

• BTreeMap::into_keys
• BTreeMap::into_values
• HashMap::into_keys
• HashMap::into_values
• arch::wasm32
• VecDeque::binary_search
• VecDeque::binary_search_by
• VecDeque::binary_search_by_key
• VecDeque::partition_point

Cargo

• Added the --prune <spec> option to cargo-tree to remove a package from the dependency graph.
• Added the --depth option to cargo-tree to print only to a certain depth in the tree
• Added the no-proc-macro value to cargo-tree --edges to hide procedural macro dependencies.
• A new environment variable named CARGO_TARGET_TMPDIR is available. This variable points to a directory that integration tests and benches can use as a "scratchpad" for testing filesystem operations.

Compatibility Notes

• Mixing Option and Result via ? is no longer permitted in closures for inferred types.
• Previously unsound code is no longer permitted where different constructors in branches could require different lifetimes.
• As previously mentioned the std::arch intrinsics now uses stricter const checking than before and may reject some previously accepted code.
• i128 multiplication on Cortex M0+ platforms currently unconditionally causes overflow when compiled with codegen-units = 1.

Version 1.53.0 (2021-06-17)

Language

• You can now use unicode for identifiers. This allows multilingual identifiers but still doesn't allow glyphs that are not considered characters such as ◆ or 🦀. More specifically you can now use any identifier that matches the UAX #31 "Unicode Identifier and Pattern Syntax" standard. This is the same standard as languages like Python, however Rust uses NFC normalization which may be different from other languages.
• You can now specify "or patterns" inside pattern matches. Previously you could only use | (OR) on complete patterns. E.g.

  #![allow(unused)]
  fn main() {
  let x = Some(2u8);
  // Before
  matches!(x, Some(1) | Some(2));
  // Now
  matches!(x, Some(1 | 2));
  }

• Added the :pat_param macro_rules! matcher. This matcher has the same semantics as the :pat matcher. This is to allow :pat to change semantics to being a pattern fragment in a future edition.

Compiler

• Updated the minimum external LLVM version to LLVM 10.
• Added Tier 3* support for the wasm64-unknown-unknown target.
• Improved debuginfo for closures and async functions on Windows MSVC.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Abort messages will now forward to android_set_abort_message on Android platforms when available.
• slice::IterMut<'_, T> now implements AsRef<[T]>
• Arrays of any length now implement IntoIterator. Currently calling .into_iter() as a method on an array will return impl Iterator<Item=&T>, but this may change in a future edition to change Item to T. Calling IntoIterator::into_iter directly on arrays will provide impl Iterator<Item=T> as expected.
• leading_zeros, and trailing_zeros are now available on all NonZero integer types.
• {f32, f64}::from_str now parse and print special values (NaN, -0) according to IEEE 754.
• You can now index into slices using (Bound<usize>, Bound<usize>).
• Add the BITS associated constant to all numeric types.

Stabilised APIs

• AtomicBool::fetch_update
• AtomicPtr::fetch_update
• BTreeMap::retain
• BTreeSet::retain
• BufReader::seek_relative
• DebugStruct::non_exhaustive
• Duration::MAX
• Duration::ZERO
• Duration::is_zero
• Duration::saturating_add
• Duration::saturating_mul
• Duration::saturating_sub
• ErrorKind::Unsupported
• Option::insert
• Ordering::is_eq
• Ordering::is_ge
• Ordering::is_gt
• Ordering::is_le
• Ordering::is_lt
• Ordering::is_ne
• OsStr::is_ascii
• OsStr::make_ascii_lowercase
• OsStr::make_ascii_uppercase
• OsStr::to_ascii_lowercase
• OsStr::to_ascii_uppercase
• Peekable::peek_mut
• Rc::decrement_strong_count
• Rc::increment_strong_count
• Vec::extend_from_within
• array::from_mut
• array::from_ref
• cmp::max_by_key
• cmp::max_by
• cmp::min_by_key
• cmp::min_by
• f32::is_subnormal
• f64::is_subnormal

Cargo

• Cargo now supports git repositories where the default HEAD branch is not "master". This also includes a switch to the version 3 Cargo.lock format which can handle default branches correctly.
• macOS targets now default to unpacked split-debuginfo.
• The authors field is no longer included in Cargo.toml for new projects.

Rustdoc

• Added the rustdoc::bare_urls lint that warns when you have URLs without hyperlinks.

Compatibility Notes

• Implement token-based handling of attributes during expansion
• Ipv4::from_str will now reject octal format IP addresses in addition to rejecting hexadecimal IP addresses. The octal format can lead to confusion and potential security vulnerabilities and is no longer recommended.
• The added BITS constant may conflict with external definitions. In particular, this was known to be a problem in the lexical-core crate, but they have published fixes for semantic versions 0.4 through 0.7. To update this dependency alone, use cargo update -p lexical-core.
• Incremental compilation remains off by default, unless one uses the RUSTC_FORCE_INCREMENTAL=1 environment variable added in 1.52.1.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Rework the std::sys::windows::alloc implementation.
• rustdoc: Don't enter an infer_ctxt in get_blanket_impls for impls that aren't blanket impls.
• rustdoc: Only look at blanket impls in get_blanket_impls
• Rework rustdoc const type

Version 1.52.1 (2021-05-10)

This release disables incremental compilation, unless the user has explicitly opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable.

This is due to the widespread, and frequently occurring, breakage encountered by Rust users due to newly enabled incremental verification in 1.52.0. Notably, Rust users should upgrade to 1.52.0 or 1.52.1: the bugs that are detected by newly added incremental verification are still present in past stable versions, and are not yet fixed on any channel. These bugs can lead to miscompilation of Rust binaries.

These problems only affect incremental builds, so release builds with Cargo should not be affected unless the user has explicitly opted into incremental. Debug and check builds are affected.

See 84970 for more details.

Version 1.52.0 (2021-05-06)

Language

• Added the unsafe_op_in_unsafe_fn lint, which checks whether the unsafe code in an unsafe fn is wrapped in a unsafe block. This lint is allowed by default, and may become a warning or hard error in a future edition.
• You can now cast mutable references to arrays to a pointer of the same type as the element.

Compiler

• Upgraded the default LLVM to LLVM 12.

Added tier 3* support for the following targets.

• s390x-unknown-linux-musl
• riscv32gc-unknown-linux-musl & riscv64gc-unknown-linux-musl
• powerpc-unknown-openbsd

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• OsString now implements Extend and FromIterator.
• cmp::Reverse now has #[repr(transparent)] representation.
• Arc<impl Error> now implements error::Error.
• All integer division and remainder operations are now const.

Stabilised APIs

• Arguments::as_str
• char::MAX
• char::REPLACEMENT_CHARACTER
• char::UNICODE_VERSION
• char::decode_utf16
• char::from_digit
• char::from_u32_unchecked
• char::from_u32
• slice::partition_point
• str::rsplit_once
• str::split_once

The following previously stable APIs are now const.

• char::len_utf8
• char::len_utf16
• char::to_ascii_uppercase
• char::to_ascii_lowercase
• char::eq_ignore_ascii_case
• u8::to_ascii_uppercase
• u8::to_ascii_lowercase
• u8::eq_ignore_ascii_case

Rustdoc

• Rustdoc lints are now treated as a tool lint, meaning that lints are now prefixed with rustdoc:: (e.g. #[warn(rustdoc::broken_intra_doc_links)]). Using the old style is still allowed, and will become a warning in a future release.
• Rustdoc now supports argument files.
• Rustdoc now generates smart punctuation for documentation.
• You can now use "task lists" in Rustdoc Markdown. E.g.

  - [x] Complete
  - [ ] Todo
  

Misc

• You can now pass multiple filters to tests. E.g. cargo test -- foo bar will run all tests that match foo and bar.
• Rustup now distributes PDB symbols for the std library on Windows, allowing you to see std symbols when debugging.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Check the result cache before the DepGraph when ensuring queries
• Try fast_reject::simplify_type in coherence before doing full check
• Only store a LocalDefId in some HIR nodes
• Store HIR attributes in a side table

Compatibility Notes

• Cargo build scripts are now forbidden from setting RUSTC_BOOTSTRAP.
• Removed support for the x86_64-rumprun-netbsd target.
• Deprecated the x86_64-sun-solaris target in favor of x86_64-pc-solaris.
• Rustdoc now only accepts ,, , and \t as delimiters for specifying languages in code blocks.
• Rustc now catches more cases of pub_use_of_private_extern_crate
• Changes in how proc macros handle whitespace may lead to panics when used with older proc-macro-hack versions. A cargo update should be sufficient to fix this in all cases.
• Turn #[derive] into a regular macro attribute

Version 1.51.0 (2021-03-25)

Language

• You can now parameterize items such as functions, traits, and structs by constant values in addition to by types and lifetimes. Also known as "const generics" E.g. you can now write the following. Note: Only values of primitive integers, bool, or char types are currently permitted.

  #![allow(unused)]
  fn main() {
  struct GenericArray<T, const LENGTH: usize> {
      inner: [T; LENGTH]
  }
  
  impl<T, const LENGTH: usize> GenericArray<T, LENGTH> {
      const fn last(&self) -> Option<&T> {
          if LENGTH == 0 {
              None
          } else {
              Some(&self.inner[LENGTH - 1])
          }
      }
  }
  }

Compiler

• Added the -Csplit-debuginfo codegen option for macOS platforms. This option controls whether debug information is split across multiple files or packed into a single file. Note This option is unstable on other platforms.
• Added tier 3* support for aarch64_be-unknown-linux-gnu, aarch64-unknown-linux-gnu_ilp32, and aarch64_be-unknown-linux-gnu_ilp32 targets.
• Added tier 3 support for i386-unknown-linux-gnu and i486-unknown-linux-gnu targets.
• The target-cpu=native option will now detect individual features of CPUs.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Box::downcast is now also implemented for any dyn Any + Send + Sync object.
• str now implements AsMut<str>.
• u64 and u128 now implement From<char>.
• Error is now implemented for &T where T implements Error.
• Poll::{map_ok, map_err} are now implemented for Poll<Option<Result<T, E>>>.
• unsigned_abs is now implemented for all signed integer types.
• io::Empty now implements io::Seek.
• rc::Weak<T> and sync::Weak<T>'s methods such as as_ptr are now implemented for T: ?Sized types.
• Div and Rem by their NonZero variant is now implemented for all unsigned integers.

Stabilized APIs

• Arc::decrement_strong_count
• Arc::increment_strong_count
• Once::call_once_force
• Peekable::next_if_eq
• Peekable::next_if
• Seek::stream_position
• array::IntoIter
• panic::panic_any
• ptr::addr_of!
• ptr::addr_of_mut!
• slice::fill_with
• slice::split_inclusive_mut
• slice::split_inclusive
• slice::strip_prefix
• slice::strip_suffix
• str::split_inclusive
• sync::OnceState
• task::Wake
• VecDeque::range
• VecDeque::range_mut

Cargo

• Added the split-debuginfo profile option to control the -Csplit-debuginfo codegen option.
• Added the resolver field to Cargo.toml to enable the new feature resolver and CLI option behavior. Version 2 of the feature resolver will try to avoid unifying features of dependencies where that unification could be unwanted. Such as using the same dependency with a std feature in a build scripts and proc-macros, while using the no-std feature in the final binary. See the Cargo book documentation for more information on the feature.

Rustdoc

• Rustdoc will now include documentation for methods available from nested Deref traits.
• You can now provide a --default-theme flag which sets the default theme to use for documentation.

Various improvements to intra-doc links:

• You can link to non-path primitives such as slice.
• You can link to associated items.
• You can now include generic parameters when linking to items, like Vec<T>.

Misc

• You can now pass --include-ignored to tests (e.g. with cargo test -- --include-ignored) to include testing tests marked #[ignore].

Compatibility Notes

• WASI platforms no longer use the wasm-bindgen ABI, and instead use the wasm32 ABI.
• rustc no longer promotes division, modulo and indexing operations to const that could fail.
• The minimum version of glibc for the following platforms has been bumped to version 2.31 for the distributed artifacts.
  • armv5te-unknown-linux-gnueabi
  • sparc64-unknown-linux-gnu
  • thumbv7neon-unknown-linux-gnueabihf
  • armv7-unknown-linux-gnueabi
  • x86_64-unknown-linux-gnux32
• atomic::spin_loop_hint has been deprecated. It's recommended to use hint::spin_loop instead.

Internal Only

• Consistently avoid constructing optimized MIR when not doing codegen

Version 1.50.0 (2021-02-11)

Language

• You can now use const values for x in [x; N] array expressions. This has been technically possible since 1.38.0, as it was unintentionally stabilized.
• Assignments to ManuallyDrop<T> union fields are now considered safe.

Compiler

• Added tier 3* support for the armv5te-unknown-linux-uclibceabi target.
• Added tier 3 support for the aarch64-apple-ios-macabi target.
• The x86_64-unknown-freebsd is now built with the full toolset.
• Dropped support for all cloudabi targets.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• proc_macro::Punct now implements PartialEq<char>.
• ops::{Index, IndexMut} are now implemented for fixed sized arrays of any length.
• On Unix platforms, the std::fs::File type now has a "niche" of -1. This value cannot be a valid file descriptor, and now means Option<File> takes up the same amount of space as File.

Stabilized APIs

• bool::then
• btree_map::Entry::or_insert_with_key
• f32::clamp
• f64::clamp
• hash_map::Entry::or_insert_with_key
• Ord::clamp
• RefCell::take
• slice::fill
• UnsafeCell::get_mut

The following previously stable methods are now const.

• IpAddr::is_ipv4
• IpAddr::is_ipv6
• IpAddr::is_unspecified
• IpAddr::is_loopback
• IpAddr::is_multicast
• Ipv4Addr::octets
• Ipv4Addr::is_loopback
• Ipv4Addr::is_private
• Ipv4Addr::is_link_local
• Ipv4Addr::is_multicast
• Ipv4Addr::is_broadcast
• Ipv4Addr::is_documentation
• Ipv4Addr::to_ipv6_compatible
• Ipv4Addr::to_ipv6_mapped
• Ipv6Addr::segments
• Ipv6Addr::is_unspecified
• Ipv6Addr::is_loopback
• Ipv6Addr::is_multicast
• Ipv6Addr::to_ipv4
• Layout::size
• Layout::align
• Layout::from_size_align
• pow for all integer types.
• checked_pow for all integer types.
• saturating_pow for all integer types.
• wrapping_pow for all integer types.
• next_power_of_two for all unsigned integer types.
• checked_next_power_of_two for all unsigned integer types.

Cargo

• Added the [build.rustc-workspace-wrapper] option. This option sets a wrapper to execute instead of rustc, for workspace members only.
• cargo:rerun-if-changed will now, if provided a directory, scan the entire contents of that directory for changes.
• Added the --workspace flag to the cargo update command.

Misc

• The search results tab and the help button are focusable with keyboard in rustdoc.
• Running tests will now print the total time taken to execute.

Compatibility Notes

• The compare_and_swap method on atomics has been deprecated. It's recommended to use the compare_exchange and compare_exchange_weak methods instead.
• Changes in how TokenStreams are checked have fixed some cases where you could write unhygenic macro_rules! macros.
• #![test] as an inner attribute is now considered unstable like other inner macro attributes, and reports an error by default through the soft_unstable lint.
• Overriding a forbid lint at the same level that it was set is now a hard error.
• You can no longer intercept panic! calls by supplying your own macro. It's recommended to use the #[panic_handler] attribute to provide your own implementation.
• Semi-colons after item statements (e.g. struct Foo {};) now produce a warning.

Version 1.49.0 (2020-12-31)

Language

• Unions can now implement Drop, and you can now have a field in a union with ManuallyDrop<T>.
• You can now cast uninhabited enums to integers.
• You can now bind by reference and by move in patterns. This allows you to selectively borrow individual components of a type. E.g.

  #![allow(unused)]
  fn main() {
  #[derive(Debug)]
  struct Person {
      name: String,
      age: u8,
  }
  
  let person = Person {
      name: String::from("Alice"),
      age: 20,
  };
  
  // `name` is moved out of person, but `age` is referenced.
  let Person { name, ref age } = person;
  println!("{} {}", name, age);
  }

Compiler

• Added tier 1* support for aarch64-unknown-linux-gnu.
• Added tier 2 support for aarch64-apple-darwin.
• Added tier 2 support for aarch64-pc-windows-msvc.
• Added tier 3 support for mipsel-unknown-none.
• Raised the minimum supported LLVM version to LLVM 9.
• Output from threads spawned in tests is now captured.
• Change os and vendor values to "none" and "unknown" for some targets

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• RangeInclusive now checks for exhaustion when calling contains and indexing.
• ToString::to_string now no longer shrinks the internal buffer in the default implementation.

Stabilized APIs

• slice::select_nth_unstable
• slice::select_nth_unstable_by
• slice::select_nth_unstable_by_key

The following previously stable methods are now const.

• Poll::is_ready
• Poll::is_pending

Cargo

• Building a crate with cargo-package should now be independently reproducible.
• cargo-tree now marks proc-macro crates.
• Added CARGO_PRIMARY_PACKAGE build-time environment variable. This variable will be set if the crate being built is one the user selected to build, either with -p or through defaults.
• You can now use glob patterns when specifying packages & targets.

Compatibility Notes

• Demoted i686-unknown-freebsd from host tier 2 to target tier 2 support.
• Macros that end with a semi-colon are now treated as statements even if they expand to nothing.
• Rustc will now check for the validity of some built-in attributes on enum variants. Previously such invalid or unused attributes could be ignored.
• Leading whitespace is stripped more uniformly in documentation comments, which may change behavior. You read this post about the changes for more details.
• Trait bounds are no longer inferred for associated types.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• rustc's internal crates are now compiled using the initial-exec Thread Local Storage model.
• Calculate visibilities once in resolve.
• Added system to the llvm-libunwind bootstrap config option.
• Added --color for configuring terminal color support to bootstrap.

Version 1.48.0 (2020-11-19)

Language

• The unsafe keyword is now syntactically permitted on modules. This is still rejected semantically, but can now be parsed by procedural macros.

Compiler

• Stabilised the -C link-self-contained=<yes|no> compiler flag. This tells rustc whether to link its own C runtime and libraries or to rely on a external linker to find them. (Supported only on windows-gnu, linux-musl, and wasi platforms.)
• You can now use -C target-feature=+crt-static on linux-gnu targets. Note: If you're using cargo you must explicitly pass the --target flag.
• Added tier 2* support for aarch64-unknown-linux-musl.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• io::Write is now implemented for &ChildStdin &Sink, &Stdout, and &Stderr.
• All arrays of any length now implement TryFrom<Vec<T>>.
• The matches! macro now supports having a trailing comma.
• Vec<A> now implements PartialEq<[B]> where A: PartialEq<B>.
• The RefCell::{replace, replace_with, clone} methods now all use #[track_caller].

Stabilized APIs

• slice::as_ptr_range
• slice::as_mut_ptr_range
• VecDeque::make_contiguous
• future::pending
• future::ready

The following previously stable methods are now const fn's:

• Option::is_some
• Option::is_none
• Option::as_ref
• Result::is_ok
• Result::is_err
• Result::as_ref
• Ordering::reverse
• Ordering::then

Cargo

Rustdoc

• You can now link to items in rustdoc using the intra-doc link syntax. E.g. /// Uses [`std::future`] will automatically generate a link to std::future's documentation. See "Linking to items by name" for more information.
• You can now specify #[doc(alias = "<alias>")] on items to add search aliases when searching through rustdoc's UI.

Compatibility Notes

• Promotion of references to 'static lifetime inside const fn now follows the same rules as inside a fn body. In particular, &foo() will not be promoted to 'static lifetime any more inside const fns.
• Associated type bindings on trait objects are now verified to meet the bounds declared on the trait when checking that they implement the trait.
• When trait bounds on associated types or opaque types are ambiguous, the compiler no longer makes an arbitrary choice on which bound to use.
• Fixed recursive nonterminals not being expanded in macros during pretty-print/reparse check. This may cause errors if your macro wasn't correctly handling recursive nonterminal tokens.
• &mut references to non zero-sized types are no longer promoted.
• rustc will now warn if you use attributes like #[link_name] or #[cold] in places where they have no effect.
• Updated _mm256_extract_epi8 and _mm256_extract_epi16 signatures in arch::{x86, x86_64} to return i32 to match the vendor signatures.
• mem::uninitialized will now panic if any inner types inside a struct or enum disallow zero-initialization.
• #[target_feature] will now error if used in a place where it has no effect.
• Foreign exceptions are now caught by catch_unwind and will cause an abort. Note: This behaviour is not guaranteed and is still considered undefined behaviour, see the catch_unwind documentation for further information.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• Building rustc from source now uses ninja by default over make. You can continue building with make by setting ninja=false in your config.toml.
• cg_llvm: fewer_names in uncached_llvm_type
• Made ensure_sufficient_stack() non-generic

Version 1.47.0 (2020-10-08)

Language

• Closures will now warn when not used.

Compiler

• Stabilized the -C control-flow-guard codegen option, which enables Control Flow Guard for Windows platforms, and is ignored on other platforms.
• Upgraded to LLVM 11.
• Added tier 3* support for the thumbv4t-none-eabi target.
• Upgrade the FreeBSD toolchain to version 11.4
• RUST_BACKTRACE's output is now more compact.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• CStr now implements Index<RangeFrom<usize>>.
• Traits in std/core are now implemented for arrays of any length, not just those of length less than 33.
• ops::RangeFull and ops::Range now implement Default.
• panic::Location now implements Copy, Clone, Eq, Hash, Ord, PartialEq, and PartialOrd.

Stabilized APIs

• Ident::new_raw
• Range::is_empty
• RangeInclusive::is_empty
• Result::as_deref
• Result::as_deref_mut
• Vec::leak
• pointer::offset_from
• f32::TAU
• f64::TAU

The following previously stable APIs have now been made const.

• The new method for all NonZero integers.
• The checked_add,checked_sub,checked_mul,checked_neg, checked_shl, checked_shr, saturating_add, saturating_sub, and saturating_mul methods for all integers.
• The checked_abs, saturating_abs, saturating_neg, and signum for all signed integers.
• The is_ascii_alphabetic, is_ascii_uppercase, is_ascii_lowercase, is_ascii_alphanumeric, is_ascii_digit, is_ascii_hexdigit, is_ascii_punctuation, is_ascii_graphic, is_ascii_whitespace, and is_ascii_control methods for char and u8.

Cargo

• build-dependencies are now built with opt-level 0 by default. You can override this by setting the following in your Cargo.toml.

  [profile.release.build-override]
  opt-level = 3
  

• cargo-help will now display man pages for commands rather just the --help text.
• cargo-metadata now emits a test field indicating if a target has tests enabled.
• workspace.default-members now respects workspace.exclude.
• cargo-publish will now use an alternative registry by default if it's the only registry specified in package.publish.

Misc

• Added a help button beside Rustdoc's searchbar that explains rustdoc's type based search.
• Added the Ayu theme to rustdoc.

Compatibility Notes

• Bumped the minimum supported Emscripten version to 1.39.20.
• Fixed a regression parsing {} && false in tail expressions.
• Added changes to how proc-macros are expanded in macro_rules! that should help to preserve more span information. These changes may cause compilation errors if your macro was unhygenic or didn't correctly handle Delimiter::None.
• Moved support for the CloudABI target to tier 3.
• linux-gnu targets now require minimum kernel 2.6.32 and glibc 2.11.
• Added the rustc-docs component. This allows you to install and read the documentation for the compiler internal APIs. (Currently only available for x86_64-unknown-linux-gnu.)

Internal Only

• Improved default settings for bootstrapping in x.py. You can read details about this change in the "Changes to x.py defaults" post on the Inside Rust blog.

Version 1.46.0 (2020-08-27)

Language

• if, match, and loop expressions can now be used in const functions.
• Additionally you are now also able to coerce and cast to slices (&[T]) in const functions.
• The #[track_caller] attribute can now be added to functions to use the function's caller's location information for panic messages.
• Recursively indexing into tuples no longer needs parentheses. E.g. x.0.0 over (x.0).0.
• mem::transmute can now be used in statics and constants. Note You currently can't use mem::transmute in constant functions.

Compiler

• You can now use the cdylib target on Apple iOS and tvOS platforms.
• Enabled static "Position Independent Executables" by default for x86_64-unknown-linux-musl.

Libraries

• mem::forget is now a const fn.
• String now implements From<char>.
• The leading_ones, and trailing_ones methods have been stabilised for all integer types.
• vec::IntoIter<T> now implements AsRef<[T]>.
• All non-zero integer types (NonZeroU8) now implement TryFrom for their zero-able equivalent (e.g. TryFrom<u8>).
• &[T] and &mut [T] now implement PartialEq<Vec<T>>.
• (String, u16) now implements ToSocketAddrs.
• vec::Drain<'_, T> now implements AsRef<[T]>.

Stabilized APIs

• Option::zip
• vec::Drain::as_slice

Cargo

Added a number of new environment variables that are now available when compiling your crate.

• CARGO_BIN_NAME and CARGO_CRATE_NAME Providing the name of the specific binary being compiled and the name of the crate.
• CARGO_PKG_LICENSE The license from the manifest of the package.
• CARGO_PKG_LICENSE_FILE The path to the license file.

Compatibility Notes

• The target configuration option abi_blacklist has been renamed to unsupported_abis. The old name will still continue to work.
• Rustc will now warn if you cast a C-like enum that implements Drop. This was previously accepted but will become a hard error in a future release.
• Rustc will fail to compile if you have a struct with #[repr(i128)] or #[repr(u128)]. This representation is currently only allowed on enums.
• Tokens passed to macro_rules! are now always captured. This helps ensure that spans have the correct information, and may cause breakage if you were relying on receiving spans with dummy information.
• The InnoSetup installer for Windows is no longer available. This was a legacy installer that was replaced by a MSI installer a few years ago but was still being built.
• {f32, f64}::asinh now returns the correct values for negative numbers.
• Rustc will no longer accept overlapping trait implementations that only differ in how the lifetime was bound.
• Rustc now correctly relates the lifetime of an existential associated type. This fixes some edge cases where rustc would erroneously allow you to pass a shorter lifetime than expected.
• Rustc now dynamically links to libz (also called zlib) on Linux. The library will need to be installed for rustc to work, even though we expect it to be already available on most systems.
• Tests annotated with #[should_panic] are broken on ARMv7 while running under QEMU.
• Pretty printing of some tokens in procedural macros changed. The exact output returned by rustc's pretty printing is an unstable implementation detail: we recommend any macro relying on it to switch to a more robust parsing system.

Version 1.45.2 (2020-08-03)

• Fix bindings in tuple struct patterns
• Fix track_caller integration with trait objects

Version 1.45.1 (2020-07-30)

• Fix const propagation with references.
• rustfmt accepts rustfmt_skip in cfg_attr again.
• Avoid spurious implicit region bound.
• Install clippy on x.py install

Version 1.45.0 (2020-07-16)

Language

• Out of range float to int conversions using as has been defined as a saturating conversion. This was previously undefined behaviour, but you can use the {f64, f32}::to_int_unchecked methods to continue using the current behaviour, which may be desirable in rare performance sensitive situations.
• mem::Discriminant<T> now uses T's discriminant type instead of always using u64.
• Function like procedural macros can now be used in expression, pattern, and statement positions. This means you can now use a function-like procedural macro anywhere you can use a declarative (macro_rules!) macro.

Compiler

• You can now override individual target features through the target-feature flag. E.g. -C target-feature=+avx2 -C target-feature=+fma is now equivalent to -C target-feature=+avx2,+fma.
• Added the force-unwind-tables flag. This option allows rustc to always generate unwind tables regardless of panic strategy.
• Added the embed-bitcode flag. This codegen flag allows rustc to include LLVM bitcode into generated rlibs (this is on by default).
• Added the tiny value to the code-model codegen flag.
• Added tier 3 support* for the mipsel-sony-psp target.
• Added tier 3 support for the thumbv7a-uwp-windows-msvc target.
• Upgraded to LLVM 10.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• net::{SocketAddr, SocketAddrV4, SocketAddrV6} now implements PartialOrd and Ord.
• proc_macro::TokenStream now implements Default.
• You can now use char with ops::{Range, RangeFrom, RangeFull, RangeInclusive, RangeTo} to iterate over a range of codepoints. E.g. you can now write the following;

  #![allow(unused)]
  fn main() {
  for ch in 'a'..='z' {
      print!("{}", ch);
  }
  println!();
  // Prints "abcdefghijklmnopqrstuvwxyz"
  }

• OsString now implements FromStr.
• The saturating_neg method has been added to all signed integer primitive types, and the saturating_abs method has been added for all integer primitive types.
• Arc<T>, Rc<T> now implement From<Cow<'_, T>>, and Box now implements From<Cow> when T is [T: Copy], str, CStr, OsStr, or Path.
• Box<[T]> now implements From<[T; N]>.
• BitOr and BitOrAssign are implemented for all NonZero integer types.
• The fetch_min, and fetch_max methods have been added to all atomic integer types.
• The fetch_update method has been added to all atomic integer types.

Stabilized APIs

• Arc::as_ptr
• BTreeMap::remove_entry
• Rc::as_ptr
• rc::Weak::as_ptr
• rc::Weak::from_raw
• rc::Weak::into_raw
• str::strip_prefix
• str::strip_suffix
• sync::Weak::as_ptr
• sync::Weak::from_raw
• sync::Weak::into_raw
• char::UNICODE_VERSION
• Span::resolved_at
• Span::located_at
• Span::mixed_site
• unix::process::CommandExt::arg0

Cargo

• Cargo uses the embed-bitcode flag to optimize disk usage and build time.

Misc

• Rustdoc now supports strikethrough text in Markdown. E.g. ~~outdated information~~ becomes "outdated information".
• Added an emoji to Rustdoc's deprecated API message.

Compatibility Notes

• Trying to self initialize a static value (that is creating a value using itself) is unsound and now causes a compile error.
• {f32, f64}::powi now returns a slightly different value on Windows. This is due to changes in LLVM's intrinsics which {f32, f64}::powi uses.
• Rustdoc's CLI's extra error exit codes have been removed. These were previously undocumented and not intended for public use. Rustdoc still provides a non-zero exit code on errors.
• Rustc's lto flag is incompatible with the new embed-bitcode=no. This may cause issues if LTO is enabled through RUSTFLAGS or cargo rustc flags while cargo is adding embed-bitcode itself. The recommended way to control LTO is with Cargo profiles, either in Cargo.toml or .cargo/config, or by setting CARGO_PROFILE_<name>_LTO in the environment.

Internals Only

• Make clippy a git subtree instead of a git submodule
• Unify the undo log of all snapshot types

Version 1.44.1 (2020-06-18)

• rustfmt accepts rustfmt_skip in cfg_attr again.
• Don't hash executable filenames on apple platforms, fixing backtraces.
• Fix crashes when finding backtrace on macOS.
• Clippy applies lint levels into different files.

Version 1.44.0 (2020-06-04)

Language

• You can now use async/.await with #[no_std] enabled.
• Added the unused_braces lint.

Syntax-only changes

• Expansion-driven outline module parsing

#![allow(unused)]
fn main() {
#[cfg(FALSE)]
mod foo {
    mod bar {
        mod baz; // `foo/bar/baz.rs` doesn't exist, but no error!
    }
}
}

These are still rejected semantically, so you will likely receive an error but these changes can be seen and parsed by macros and conditional compilation.

Compiler

• Rustc now respects the -C codegen-units flag in incremental mode. Additionally when in incremental mode rustc defaults to 256 codegen units.
• Refactored catch_unwind to have zero-cost, unless unwinding is enabled and a panic is thrown.
• Added tier 3* support for the aarch64-unknown-none and aarch64-unknown-none-softfloat targets.
• Added tier 3 support for arm64-apple-tvos and x86_64-apple-tvos targets.

Libraries

• Special cased vec![] to map directly to Vec::new(). This allows vec![] to be able to be used in const contexts.
• convert::Infallible now implements Hash.
• OsString now implements DerefMut and IndexMut returning a &mut OsStr.
• Unicode 13 is now supported.
• String now implements From<&mut str>.
• IoSlice now implements Copy.
• Vec<T> now implements From<[T; N]>. Where N is at most 32.
• proc_macro::LexError now implements fmt::Display and Error.
• from_le_bytes, to_le_bytes, from_be_bytes, to_be_bytes, from_ne_bytes, and to_ne_bytes methods are now const for all integer types.

Stabilized APIs

• PathBuf::with_capacity
• PathBuf::capacity
• PathBuf::clear
• PathBuf::reserve
• PathBuf::reserve_exact
• PathBuf::shrink_to_fit
• f32::to_int_unchecked
• f64::to_int_unchecked
• Layout::align_to
• Layout::pad_to_align
• Layout::array
• Layout::extend

Cargo

• Added the cargo tree command which will print a tree graph of your dependencies. E.g.

    mdbook v0.3.2 (/Users/src/rust/mdbook)
  ├── ammonia v3.0.0
  │   ├── html5ever v0.24.0
  │   │   ├── log v0.4.8
  │   │   │   └── cfg-if v0.1.9
  │   │   ├── mac v0.1.1
  │   │   └── markup5ever v0.9.0
  │   │       ├── log v0.4.8 (*)
  │   │       ├── phf v0.7.24
  │   │       │   └── phf_shared v0.7.24
  │   │       │       ├── siphasher v0.2.3
  │   │       │       └── unicase v1.4.2
  │   │       │           [build-dependencies]
  │   │       │           └── version_check v0.1.5
  ...
  

  You can also display dependencies on multiple versions of the same crate with cargo tree -d (short for cargo tree --duplicates).

Misc

• Rustdoc now allows you to specify --crate-version to have rustdoc include the version in the sidebar.

Compatibility Notes

• Rustc now correctly generates static libraries on Windows GNU targets with the .a extension, rather than the previous .lib.
• Removed the -C no_integrated_as flag from rustc.
• The file_name property in JSON output of macro errors now points the actual source file rather than the previous format of <NAME macros>. Note: this may not point to a file that actually exists on the user's system.
• The minimum required external LLVM version has been bumped to LLVM 8.
• mem::{zeroed, uninitialised} will now panic when used with types that do not allow zero initialization such as NonZeroU8. This was previously a warning.
• In 1.45.0 (the next release) converting a f64 to u32 using the as operator has been defined as a saturating operation. This was previously undefined behaviour, but you can use the {f64, f32}::to_int_unchecked methods to continue using the current behaviour, which may be desirable in rare performance sensitive situations.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• dep_graph Avoid allocating a set on when the number reads are small.
• Replace big JS dict with JSON parsing.

Version 1.43.1 (2020-05-07)

• Updated openssl-src to 1.1.1g for CVE-2020-1967.
• Fixed the stabilization of AVX-512 features.
• Fixed cargo package --list not working with unpublished dependencies.

Version 1.43.0 (2020-04-23)

Language

• Fixed using binary operations with &{number} (e.g. &1.0) not having the type inferred correctly.
• Attributes such as #[cfg()] can now be used on if expressions.

Syntax only changes

• Allow type Foo: Ord syntactically.
• Fuse associated and extern items up to defaultness.
• Syntactically allow self in all fn contexts.
• Merge fn syntax + cleanup item parsing.
• item macro fragments can be interpolated into traits, impls, and extern blocks. For example, you may now write:

  #![allow(unused)]
  fn main() {
  macro_rules! mac_trait {
      ($i:item) => {
          trait T { $i }
      }
  }
  mac_trait! {
      fn foo() {}
  }
  }

These are still rejected semantically, so you will likely receive an error but these changes can be seen and parsed by macros and conditional compilation.

Compiler

• You can now pass multiple lint flags to rustc to override the previous flags. For example; rustc -D unused -A unused-variables denies everything in the unused lint group except unused-variables which is explicitly allowed. However, passing rustc -A unused-variables -D unused denies everything in the unused lint group including unused-variables since the allow flag is specified before the deny flag (and therefore overridden).
• rustc will now prefer your system MinGW libraries over its bundled libraries if they are available on windows-gnu.
• rustc now buffers errors/warnings printed in JSON.

Libraries

• Arc<[T; N]>, Box<[T; N]>, and Rc<[T; N]>, now implement TryFrom<Arc<[T]>>,TryFrom<Box<[T]>>, and TryFrom<Rc<[T]>> respectively. Note These conversions are only available when N is 0..=32.
• You can now use associated constants on floats and integers directly, rather than having to import the module. e.g. You can now write u32::MAX or f32::NAN with no imports.
• u8::is_ascii is now const.
• String now implements AsMut<str>.
• Added the primitive module to std and core. This module reexports Rust's primitive types. This is mainly useful in macros where you want avoid these types being shadowed.
• Relaxed some of the trait bounds on HashMap and HashSet.
• string::FromUtf8Error now implements Clone + Eq.

Stabilized APIs

• Once::is_completed
• f32::LOG10_2
• f32::LOG2_10
• f64::LOG10_2
• f64::LOG2_10
• iter::once_with

Cargo

• You can now set config [profile]s in your .cargo/config, or through your environment.
• Cargo will now set CARGO_BIN_EXE_<name> pointing to a binary's executable path when running integration tests or benchmarks. <name> is the name of your binary as-is e.g. If you wanted the executable path for a binary named my-programyou would use env!("CARGO_BIN_EXE_my-program").

Misc

• Certain checks in the const_err lint were deemed unrelated to const evaluation, and have been moved to the unconditional_panic and arithmetic_overflow lints.

Compatibility Notes

• Having trailing syntax in the assert! macro is now a hard error. This has been a warning since 1.36.0.
• Fixed Self not having the correctly inferred type. This incorrectly led to some instances being accepted, and now correctly emits a hard error.

Internal Only

These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.

• All components are now built with opt-level=3 instead of 2.
• Improved how rustc generates drop code.
• Improved performance from #[inline]-ing certain hot functions.
• traits: preallocate 2 Vecs of known initial size
• Avoid exponential behaviour when relating types
• Skip Drop terminators for enum variants without drop glue
• Improve performance of coherence checks
• Deduplicate types in the generator witness
• Invert control in struct_lint_level.

Version 1.42.0 (2020-03-12)

Language

• You can now use the slice pattern syntax with subslices. e.g.

  #![allow(unused)]
  fn main() {
  fn foo(words: &[&str]) {
      match words {
          ["Hello", "World", "!", ..] => println!("Hello World!"),
          ["Foo", "Bar", ..] => println!("Baz"),
          rest => println!("{:?}", rest),
      }
  }
  }

• You can now use #[repr(transparent)] on univariant enums. Meaning that you can create an enum that has the exact layout and ABI of the type it contains.

• You can now use outer attribute procedural macros on inline modules.

• There are some syntax-only changes:

  • default is syntactically allowed before items in trait definitions.
  • Items in impls (i.e. consts, types, and fns) may syntactically leave out their bodies in favor of ;.
  • Bounds on associated types in impls are now syntactically allowed (e.g. type Foo: Ord;).
  • ... (the C-variadic type) may occur syntactically directly as the type of any function parameter.

  These are still rejected semantically, so you will likely receive an error but these changes can be seen and parsed by procedural macros and conditional compilation.

Compiler

• Added tier 2* support for armv7a-none-eabi.
• Added tier 2 support for riscv64gc-unknown-linux-gnu.
• Option::{expect,unwrap} and Result::{expect, expect_err, unwrap, unwrap_err} now produce panic messages pointing to the location where they were called, rather than core's internals.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• iter::Empty<T> now implements Send and Sync for any T.
• Pin::{map_unchecked, map_unchecked_mut} no longer require the return type to implement Sized.
• io::Cursor now derives PartialEq and Eq.
• Layout::new is now const.
• Added Standard Library support for riscv64gc-unknown-linux-gnu.

Stabilized APIs

• CondVar::wait_while
• CondVar::wait_timeout_while
• DebugMap::key
• DebugMap::value
• ManuallyDrop::take
• matches!
• ptr::slice_from_raw_parts_mut
• ptr::slice_from_raw_parts

Cargo

• You no longer need to include extern crate proc_macro; to be able to use proc_macro; in the 2018 edition.

Compatibility Notes

• Error::description has been deprecated, and its use will now produce a warning. It's recommended to use Display/to_string instead.

Version 1.41.1 (2020-02-27)

• Always check types of static items
• Always check lifetime bounds of Copy impls
• Fix miscompilation in callers of Layout::repeat
• Rust 1.41.0 was announced as the last Rust release with tier 1 or tier 2 support for 32-bit Apple targets. That announcement did not expect a patch release. 1.41.1 also includes release binaries for these targets.

Version 1.41.0 (2020-01-30)

Language

• You can now pass type parameters to foreign items when implementing traits. E.g. You can now write impl<T> From<Foo> for Vec<T> {}.
• You can now arbitrarily nest receiver types in the self position. E.g. you can now write fn foo(self: Box<Box<Self>>) {}. Previously only Self, &Self, &mut Self, Arc<Self>, Rc<Self>, and Box<Self> were allowed.
• You can now use any valid identifier in a format_args macro. Previously identifiers starting with an underscore were not allowed.
• Visibility modifiers (e.g. pub) are now syntactically allowed on trait items and enum variants. These are still rejected semantically, but can be seen and parsed by procedural macros and conditional compilation.
• You can now define a Rust extern "C" function with Box<T> and use T* as the corresponding type on the C side. Please see the documentation for more information, including the important caveat about preferring to avoid Box<T> in Rust signatures for functions defined in C.

Compiler

• Rustc will now warn if you have unused loop 'labels.
• Removed support for the i686-unknown-dragonfly target.
• Added tier 3 support* for the riscv64gc-unknown-linux-gnu target.
• You can now pass an arguments file passing the @path syntax to rustc. Note that the format differs somewhat from what is found in other tooling; please see the documentation for more information.
• You can now provide --extern flag without a path, indicating that it is available from the search path or specified with an -L flag.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• The core::panic module is now stable. It was already stable through std.
• NonZero* numerics now implement From<NonZero*> if it's a smaller integer width. E.g. NonZeroU16 now implements From<NonZeroU8>.
• MaybeUninit<T> now implements fmt::Debug.

Stabilized APIs

• Result::map_or
• Result::map_or_else
• std::rc::Weak::weak_count
• std::rc::Weak::strong_count
• std::sync::Weak::weak_count
• std::sync::Weak::strong_count

Cargo

• Cargo will now document all the private items for binary crates by default.
• cargo-install will now reinstall the package if it detects that it is out of date.
• Cargo.lock now uses a more git friendly format that should help to reduce merge conflicts.
• You can now override specific dependencies's build settings E.g. [profile.dev.package.image] opt-level = 2 sets the image crate's optimisation level to 2 for debug builds. You can also use [profile.<profile>.build-override] to override build scripts and their dependencies.

Misc

• You can now specify edition in documentation code blocks to compile the block for that edition. E.g. edition2018 tells rustdoc that the code sample should be compiled the 2018 edition of Rust.
• You can now provide custom themes to rustdoc with --theme, and check the current theme with --check-theme.
• You can use #[cfg(doc)] to compile an item when building documentation.

Compatibility Notes

• As previously announced 1.41 will be the last tier 1 release for 32-bit Apple targets. This means that the source code is still available to build, but the targets are no longer being tested and release binaries for those platforms will no longer be distributed by the Rust project. Please refer to the linked blog post for more information.

Version 1.40.0 (2019-12-19)

Language

• You can now use tuple structs and tuple enum variant's constructors in const contexts. e.g.

  #![allow(unused)]
  fn main() {
  pub struct Point(i32, i32);
  
  const ORIGIN: Point = {
      let constructor = Point;
  
      constructor(0, 0)
  };
  }

• You can now mark structs, enums, and enum variants with the #[non_exhaustive] attribute to indicate that there may be variants or fields added in the future. For example this requires adding a wild-card branch (_ => {}) to any match statements on a non-exhaustive enum. (RFC 2008)

• You can now use function-like procedural macros in extern blocks and in type positions. e.g. type Generated = macro!();

• Function-like and attribute procedural macros can now emit macro_rules! items, so you can now have your macros generate macros.

• The meta pattern matcher in macro_rules! now correctly matches the modern attribute syntax. For example (#[$m:meta]) now matches #[attr], #[attr{tokens}], #[attr[tokens]], and #[attr(tokens)].

Compiler

• Added tier 3 support* for the thumbv7neon-unknown-linux-musleabihf target.
• Added tier 3 support for the aarch64-unknown-none-softfloat target.
• Added tier 3 support for the mips64-unknown-linux-muslabi64, and mips64el-unknown-linux-muslabi64 targets.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• The is_power_of_two method on unsigned numeric types is now a const function.

Stabilized APIs

• BTreeMap::get_key_value
• HashMap::get_key_value
• Option::as_deref_mut
• Option::as_deref
• Option::flatten
• UdpSocket::peer_addr
• f32::to_be_bytes
• f32::to_le_bytes
• f32::to_ne_bytes
• f64::to_be_bytes
• f64::to_le_bytes
• f64::to_ne_bytes
• f32::from_be_bytes
• f32::from_le_bytes
• f32::from_ne_bytes
• f64::from_be_bytes
• f64::from_le_bytes
• f64::from_ne_bytes
• mem::take
• slice::repeat
• todo!

Cargo

• Cargo will now always display warnings, rather than only on fresh builds.
• Feature flags (except --all-features) passed to a virtual workspace will now produce an error. Previously these flags were ignored.
• You can now publish dev-dependencies without including a version.

Misc

• You can now specify the #[cfg(doctest)] attribute to include an item only when running documentation tests with rustdoc.

Compatibility Notes

• As previously announced, any previous NLL warnings in the 2015 edition are now hard errors.
• The include! macro will now warn if it failed to include the entire file. The include! macro unintentionally only includes the first expression in a file, and this can be unintuitive. This will become either a hard error in a future release, or the behavior may be fixed to include all expressions as expected.
• Using #[inline] on function prototypes and consts now emits a warning under unused_attribute lint. Using #[inline] anywhere else inside traits or extern blocks now correctly emits a hard error.

Version 1.39.0 (2019-11-07)

Language

• You can now create async functions and blocks with async fn, async move {}, and async {} respectively, and you can now call .await on async expressions.
• You can now use certain attributes on function, closure, and function pointer parameters. These attributes include cfg, cfg_attr, allow, warn, deny, forbid as well as inert helper attributes used by procedural macro attributes applied to items. e.g.

  #![allow(unused)]
  fn main() {
  fn len(
      #[cfg(windows)] slice: &[u16],
      #[cfg(not(windows))] slice: &[u8],
  ) -> usize {
      slice.len()
  }
  }

• You can now take shared references to bind-by-move patterns in the if guards of match arms. e.g.

  fn main() {
      let array: Box<[u8; 4]> = Box::new([1, 2, 3, 4]);
  
      match array {
          nums
  //      ---- `nums` is bound by move.
              if nums.iter().sum::<u8>() == 10
  //                 ^------ `.iter()` implicitly takes a reference to `nums`.
          => {
              drop(nums);
  //          ----------- Legal as `nums` was bound by move and so we have ownership.
          }
          _ => unreachable!(),
      }
  }

Compiler

• Added tier 3* support for the i686-unknown-uefi target.
• Added tier 3 support for the sparc64-unknown-openbsd target.
• rustc will now trim code snippets in diagnostics to fit in your terminal. Note Cargo currently doesn't use this feature. Refer to cargo#7315 to track this feature's progress.
• You can now pass --show-output argument to test binaries to print the output of successful tests.

* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support.

Libraries

• Vec::new and String::new are now const functions.
• LinkedList::new is now a const function.
• str::len, [T]::len and str::as_bytes are now const functions.
• The abs, wrapping_abs, and overflowing_abs numeric functions are now const.