Rust 1.83.0-beta.5
eb6e3fa1a
extern "C" functions.& in elided self lifetimes.#[expect] for lints (RFC 2383), like #[allow] with a warning if the lint is not fulfilled.elided_lifetimes_in_associated_constant to deny.offset_from: always allow pointers to point to the same address.-Cinline-threshold=....transmute size checks.box_pointers lint.no_std Xtensa targets: xtensa-esp32-none-elf, xtensa-esp32s2-none-elf, xtensa-esp32s3-none-elfstd Xtensa targets: xtensa-esp32-espidf, xtensa-esp32s2-espidf, xtensa-esp32s3-espidfi686-unknown-redoxarm64ec-pc-windows-msvc to Tier 2.loongarch64-unknown-linux-musl to Tier 2 with host tools.wasm32-wasi. (see compatibility note below)PanicInfo and std’s PanicInfo. (see compatibility note below){Rc,Arc}::make_mut() to unsized types.driftsort and unstable ipnsort. All slice::sort* and slice::select_nth* methods are expected to see significant performance improvements. See the research project for more details.create_dir_all with respect to empty paths.core::errorhint::assert_uncheckedfs::existsAtomicBool::fetch_notDuration::abs_diffIoSlice::advanceIoSlice::advance_slicesIoSliceMut::advanceIoSliceMut::advance_slicesPanicHookInfoPanicInfo::messagePanicMessageThese APIs are now stable in const contexts:
char::from_u32_unchecked (function)char::from_u32_unchecked (method)CStr::count_bytesCStr::from_ptr.cargo_vcs_info.json is always included, even when --allow-dirty is passed.package.license-file and package.readme pointing to non-existent files during packaging.--release/--debug flag along with the --profile flag.lib.plugin key support in Cargo.toml. Rust plugin support has been deprecated for four years and was removed in 1.75.0.Usage of the wasm32-wasi target will now issue a compiler warning and request users switch to the wasm32-wasip1 target instead. Both targets are the same, wasm32-wasi is only being renamed, and this change to the WASI target is being done to enable removing wasm32-wasi in January 2025.
We have renamed std::panic::PanicInfo to std::panic::PanicHookInfo. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0.
core::panic::PanicInfo will remain unchanged, however, as this is now a different type.
The reason is that these types have different roles: std::panic::PanicHookInfo is the argument to the panic hook in std context (where panics can have an arbitrary payload), while core::panic::PanicInfo is the argument to the #[panic_handler] in no_std context (where panics always carry a formatted message). Separating these types allows us to add more useful methods to these types, such as std::panic::PanicHookInfo::payload_as_str() and core::panic::PanicInfo::message().
The new sort implementations may panic if a type’s implementation of Ord (or the given comparison function) does not implement a total order as the trait requires. Ord’s supertraits (PartialOrd, Eq, and PartialEq) must also be consistent. The previous implementations would not “notice” any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data.
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.
dead_code lint from 1.80.0exclusive_range_pattern featureResult in some scenariosrepr(packed(1))for_loops_over_fallibles lint to lint on fallibles behind references.-fuse-ld=lld on CCs that don’t support it...) as a type in trait bounds-fuse-ld=lldfoo.into_iter() resolving to &Box<[T]>: IntoIteratorsize_of and size_of_val and align_of and align_of_val to the preludePathBuf::set_extension would add a path separatorc_char on AIX to use the correct typeoffset_of! no longer returns a temporarystr.to_lowercase correctlyDEFAULT_MIN_STACK_SIZE to at least 64KiBimpl 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>LazyCellLazyLockDuration::div_duration_f32Duration::div_duration_f64Option::take_ifSeek::seek_relativeBinaryHeap::as_sliceNonNull::offsetNonNull::byte_offsetNonNull::addNonNull::byte_addNonNull::subNonNull::byte_subNonNull::offset_fromNonNull::byte_offset_fromNonNull::readNonNull::read_volatileNonNull::read_unalignedNonNull::writeNonNull::write_volatileNonNull::write_unalignedNonNull::write_bytesNonNull::copy_toNonNull::copy_to_nonoverlappingNonNull::copy_fromNonNull::copy_from_nonoverlappingNonNull::replaceNonNull::swapNonNull::drop_in_placeNonNull::align_offset<[T]>::split_at_checked<[T]>::split_at_mut_checkedstr::split_at_checkedstr::split_at_mut_checkedstr::trim_asciistr::trim_ascii_startstr::trim_ascii_end<[u8]>::trim_ascii<[u8]>::trim_ascii_start<[u8]>::trim_ascii_endIpv4Addr::BITSIpv4Addr::to_bitsIpv4Addr::from_bitsIpv6Addr::BITSIpv6Addr::to_bitsIpv6Addr::from_bitsVec::<[T; N]>::into_flattened<[[T; N]]>::as_flattened<[[T; N]]>::as_flattened_mutThese APIs are now stable in const contexts:
-Zcheck-cfg as always enabledcheck-cfg lint config for the unexpected_cfgs lintcargo update --precise <yanked>Cargo.toml when using cargo addcargo fix on IPv6-only networkscustom_code_classes_in_docs feature-std::env::{set_var, remove_var} can no longer be converted to safe function pointers and no longer implement the Fn family of traitsSelf constructor from outer item is referenced in inner nested itemindirect_structural_match and pointer_structural_match lints into hard errorswhere_clause_object_safety lint a regular object safety violationproc_macro_back_compat lint into a hard error.std::sync::ReentrantLockGuard<T> is no longer Sync if T: !Sync which means std::io::StdoutLock and std::io::StderrLock are no longer SyncFromIterator for Box<str>.
Notably, this breaks versions of the time crate before 0.3.35, due to no longer inferring the implementation for Box<[_]>.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.
const {} expressions.redundant_lifetimes lint to detect lifetimes which are semantically redundant.unnameable_types lint for public types that can’t be named.-C collapse-macro-debuginfo and #[collapse_debuginfo].if and match expressions.const fn calls.refining_impl_trait lint.main from other modules or crates.impl Trait lifetime inference-C strip to only affect binaries, not artifacts like .pdb.-Crelro-level for controlling runtime link hardening.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.aarch64-apple-visionos and aarch64-apple-visionos-sim tier 3 targets.riscv32ima-unknown-none-elf tier 3 target.aarch64-pc-windows-gnullvm, i686-pc-windows-gnullvm, and x86_64-pc-windows-gnullvm.Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
FromIterator for (impl Default + Extend, impl Default + Extend).{Div,Rem}Assign<NonZero<X>> on X.clone_from() in core/std.transmute between pointers and integers.{integer}::unchecked_add{integer}::unchecked_mul{integer}::unchecked_sub<[T]>::split_at_unchecked<[T]>::split_at_mut_unchecked<[u8]>::utf8_chunksstr::Utf8Chunksstr::Utf8Chunk<*const T>::is_aligned<*mut T>::is_alignedNonNull::is_aligned<*const [T]>::len<*mut [T]>::len<*const [T]>::is_empty<*mut [T]>::is_emptyNonNull::<[T]>::is_emptyCStr::count_bytesio::Error::downcastnum::NonZero<T>path::absoluteproc_macro::Literal::byte_characterproc_macro::Literal::c_stringThese APIs are now stable in const contexts:
Atomic*::into_innerio::Cursor::newio::Cursor::get_refio::Cursor::positionio::emptyio::repeatio::sinkpanic::Location::callerpanic::Location::filepanic::Location::linepanic::Location::columnlib.name, always normalizing to _.cargo add.gitoxide by default for listing files./ in docs to begin a search.RustcEncodable and RustcDecodable are soft-destabilized, to be removed
from the prelude in next edition.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.#[cfg(target_abi = ...)]#[diagnostic] namespace and #[diagnostic::on_unimplemented] attributeillegal_floating_point_literal_patterninvalid_reference_casting to include references casting to bigger memory layoutnon_contiguous_range_endpoints lint for singleton gaps after exclusive rangeswasm_c_abi lint for use of older wasm-bindgen versions
This lint currently only works when using Cargo.indirect_structural_match and pointer_structural_match lints to match RFCPartialEq-typed consts as patterns a hard errorrefining_impl_trait lint into _reachable, _internal variantswhere-boundstrait Trait: Auto {}: allow upcasting from dyn Trait to dyn Trait + AutoINVALID_DOC_ATTRIBUTES lint deny by defaultuse checkingTarget changes:
wasm32-wasip1 tier 2 (without host tools) targetwasm32-wasip2 tier 3 targetwasm32-wasi-preview1-threads to wasm32-wasip1-threadsarm64ec-pc-windows-msvc tier 3 targetarmv8r-none-eabihf tier 3 target for the Cortex-R52loongarch64-unknown-linux-musl tier 3 targetRefer to Rust’s platform support page for more information on Rust’s tiered platform support.
RwLock with custom implementationchar::is_grapheme_extendedimpl Read for &Stdin'static lifetimes for several std::error::Error related implementationsimpl<Fd: AsFd> impl take ?Sizedimpl From<TryReserveError> for io::ErrorThese APIs are now stable in const contexts:
rust-version when generating lockfile--charset via auto-detecting config valuetarget.<triple>.rustdocflags officiallyimpl Traitarithmetic_overflow lintconst 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.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.
rustc with 1CGU on x86_64-pc-windows-msvcrustc with 1CGU on x86_64-apple-darwinrun-make V2 infrastructure, a run_make_support library and port over 2 tests as examplestatic_mut_refs to warn on references to mutable statics.unstable_features and make use of it in the compiler.soft_unstable in future breakage reports.i128 and u128 16-byte aligned on x86-based targets.--verbose in diagnostic output.unused_tuple_struct_fields lint into dead_code.fn/const items implied bounds and well-formedness check.riscv32{im|imafc}-unknown-none-elf targets to tier 2.Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
array::each_refarray::each_mutcore::netf32::round_ties_evenf64::round_ties_evenmem::offset_of!slice::first_chunkslice::first_chunk_mutslice::split_first_chunkslice::split_first_chunk_mutslice::last_chunkslice::last_chunk_mutslice::split_last_chunkslice::split_last_chunk_mutslice::chunk_byslice::chunk_by_mutBound::mapFile::create_newMutex::clear_poisonRwLock::clear_poisoncargo::.id format as PackageIDSpec.cargo-util-schemas as a crate.().localStorage.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.
ambiguous_wide_pointer_comparisons that supersedes clippy::vtable_address_comparisons#[must_use] pointers (in particular, Box<T> where T is #[must_use]) in unused_must_use.$message_type field to distinguish json diagnostic outputsRefer to Rust’s platform support page for more information on Rust’s tiered platform support.
dbg!()std::hash::{DefaultHasher, RandomState} exportsRwLockReadGuard and RwLockWriteGuard’s Debug impls.File::create to work on hidden filesArc::unwrap_or_cloneRc::unwrap_or_cloneResult::inspectResult::inspect_errOption::inspecttype_name_of_valstd::hash::{DefaultHasher, RandomState}
These were previously available only through std::collections::hash_map.ptr::{from_ref, from_mut}ptr::addr_eqSee Cargo release notes.
() with user-provided spans,
which means that this lint will warn for user code.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.IMPLIED_BOUNDS_ENTAILMENT into a hard error from a lintimpl FromIterator for Vec
for more details.default on free const itemsasync fn and return-position impl Trait in traits.&mut T in const contexts.usize/isize exhaustively with half-open ranges.char has the same size and alignment as u32.match.COINDUCTIVE_OVERLAP_IN_COHERENCE to deny, and warn in dependencies.riscv64-linux-android target spec.Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Waker::clone_from to avoid cloning Wakers unnecessarily.BufRead for VecDeque<u8>.FusedIterator for DecodeUtf16 when the inner iterator does.Not, Bit{And,Or}{,Assign} for IP addresses.Default for ExitCode.str::SplitInclusive’s DoubleEndedIterator implcfg(unix) platforms.Atomic*::from_ptrFileTimesFileTimesExtFile::set_modifiedFile::set_timesIpAddr::to_canonicalIpv6Addr::to_canonicalOption::as_sliceOption::as_mut_slicepointer::byte_addpointer::byte_offsetpointer::byte_offset_frompointer::byte_subpointer::wrapping_byte_addpointer::wrapping_byte_offsetpointer::wrapping_byte_subThese APIs are now stable in const contexts:
Ipv6Addr::to_ipv4_mappedMaybeUninit::assume_init_readMaybeUninit::zeroedmem::discriminantmem::zeroed[workspace.members] automatically.Cargo.toml manifests.#[repr(transparent)] if it isn’t part of the public ABI.const contexts.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.
librustc_driver.so with BOLT.rustc-codegen-cranelift as rustup component on the nightly channel.std::mem::Discriminant<T> does not depend on any lifetimes in Tprivate_in_public lint with private_interfaces and private_bounds per RFC 2145.
Read more in RFC 2145.#[repr(Rust)]async blocksimpl_trait_projectionsPATH option for --print KIND=PATH*-apple-ios-macabii686-pc-windows-gnullvm as a tier 3 targetFrom<OwnedFd/Handle> for ChildStdin/out/errFrom<{&,&mut} [T; N]> for Vec<T> where T: CloneFrom<[T; N]> for Rc<[T]> and Arc<[T]>impl TryFrom<char> for u16io_error_other featureSaturating typecore::num::Saturatingimpl From<io::Stdout> for std::process::Stdioimpl From<io::Stderr> for std::process::Stdioimpl 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_uncheckedstd::ffi::OsString::into_encoded_bytesstd::ffi::OsStr::from_encoded_bytes_uncheckedstd::ffi::OsStr::as_encoded_bytesstd::io::Error::otherimpl TryFrom<char> for u16impl<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:
Cargo.toml, stabilize [lints]--keep-going build flag--help outputcargo clean, add --dry-run flag and summary line at the endcargo update, make --package more convenient by being positionalcargo update, clarify meaning of –aggressive as –recursive--dry-run--package flags) to resolve ambiguities.cargo/config.toml, merge lists in precedence ordertarget.'cfg(..)'.linker--externimpl 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.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.
clippy::fn_null_check lint as useless_ptr_null_checks.noop_method_call warn by default.try and async in macros.unconditional_recursion lint detect recursive drops.invalid_reference_casting lint is now deny-by-default (instead of allow-by-default).comment section like GCC/Clang.extern "thiscall" and "thiscall-unwind" ABIs.wasm32-wasi-preview1-threads as a tier 2 target.Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Read, Write and Seek impls for Arc<File>.io::Sink into io::Empty.RefUnwindSafe for BacktraceExitStatus implement Defaultimpl SliceIndex<str> for (Bound<usize>, Bound<usize>)assert_eq! & assert_ne! panic messages.stat struct definitions.{integer}::div_ceil{integer}::next_multiple_of{integer}::checked_next_multiple_ofstd::ffi::FromBytesUntilNulErrorstd::os::unix::fs::chownstd::os::unix::fs::fchownstd::os::unix::fs::lchownLocalKey::<Cell<T>>::getLocalKey::<Cell<T>>::setLocalKey::<Cell<T>>::takeLocalKey::<Cell<T>>::replaceLocalKey::<RefCell<T>>::with_borrowLocalKey::<RefCell<T>>::with_borrow_mutLocalKey::<RefCell<T>>::setLocalKey::<RefCell<T>>::takeLocalKey::<RefCell<T>>::replaceThese APIs are now stable in const contexts:
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.
rustc_apfloat with the new version of the crate.internal_features lint for internal unstable features.#![cfg(FALSE)] behaves on crate rootclippy::undropped_manually_drops lintclippy::invalid_utf8_in_unchecked lint as invalid_from_utf8_unchecked and invalid_from_utf8clippy::cast_ref_to_mut lint as invalid_reference_castingclippy::cmp_nan lint as invalid_nan_comparisonsdyn Trait objectscfg-ed out items to mention them in diagnostics- is given as output fileloongarch64-unknown-none*.eh_frame from being emitted for -C panic=abortRefer to Rust’s platform support page for more information on Rust’s tiered platform support.
thread::{park, unpark}T: Sized bounds on BufReader<T>, BufWriter<T> and LineWriter<T>select_nth_unstableOk on kill if process has already exitedVecs over different allocators{Arc,Rc,Weak}::ptr_eq ignore pointer metadata[]These APIs are now stable in const contexts:
-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
#12288build.jobs
parallelism back to the default.
#12222Display for Ipv6Addr for IPv4-compatible addressesmips*-unknown-linux-gnu* targets from host tier 2 to target tier 3 support.suspicious_double_ref_op lint when calling borrow()can_eq in derive(..) suggestion for missing methodraw-dylib, link_ordinal, import_name_type and -Cdlltool.clippy::{drop,forget}_{ref,copy} lints.Drop impl compatibilityPlaceMention,
making let _ = patterns more consistent with respect to the borrow checker.--print deployment-target flag for Apple targets.extern "C-unwind" and friends.
The existing extern "C" etc. may change behavior for cross-language unwinding in a future release.*-linux-musl targets to 1.2.3,
enabling time64 on 32-bit systems.debugger_visualizer
for embedding metadata like Microsoft’s Natvis.Self respect tuple constructor privacy.apple-m1 as the target CPU for aarch64-apple-darwin.x86_64h-apple-darwin target.loongarch64-unknown-linux-gnu to Tier 2 with host tools.Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Drop implementation, but panicking within a panic hook is now an immediate abort.From<&[T]> for Box<[T]> bound to T: Clone.T: Send bound
in Error for mpsc::SendError<T> and TrySendError<T>.alloc::realloc
to match Layout requirements that the size must not exceed isize::MAX.const {} syntax for std::thread_local.
This syntax was stabilized in Rust 1.59, but not previously mentioned in release notes.CStr::is_emptyBuildHasher::hash_oneNonZeroI*::is_positiveNonZeroI*::is_negativeNonZeroI*::checked_negNonZeroI*::overflowing_negNonZeroI*::saturating_negNonZeroI*::wrapping_negNeg 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_unalignedptr::readptr::read_unaligned<[T]>::split_atCargo.toml.workspace_default_members to the output of cargo metadata.cargo new/cargo init.rustdoc::unescaped_backticks lint for broken inline code.~~old~~ vs. ~new~)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.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.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.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.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.
asm! operandsformat_args invocations to uses captureslet _ = expr position.-Cdebuginfo=line-tables-only), which may eventually become the default for -Cdebuginfo=1.unused_allocation lint against Box::new tooloongarch64-unknown-linux-gnui586-pc-nto-qnx700 (QNX Neutrino RTOS, version 7.0),Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Command prefer non-verbatim pathsconcat!Cellpartial_cmp to implement tuple lt/le/ge/gtatomic_as_ptrnonnull_slice_from_raw_partsonce_cellnonzero_min_maxFnPtr 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.NonZero*::MIN/MAXBinaryHeap::retainDefault for std::collections::binary_heap::IntoIterDefault 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::RangeDefault for std::collections::btree_set::{IntoIter, Iter}Default for std::collections::btree_set::RangeDefault for std::collections::linked_list::{IntoIter, Iter, IterMut}Default for std::vec::IntoIterDefault for std::iter::ChainDefault for std::iter::ClonedDefault for std::iter::CopiedDefault for std::iter::EnumerateDefault for std::iter::FlattenDefault for std::iter::FuseDefault for std::iter::RevDefault for std::slice::IterDefault for std::slice::IterMutRc::into_innerArc::into_innerstd::cell::OnceCellOption::is_some_andNonNull::slice_from_raw_partsResult::is_ok_andResult::is_err_andstd::sync::atomic::Atomic*::as_ptrstd::io::IsTerminalstd::os::linux::net::SocketAddrExtstd::os::unix::net::UnixDatagram::bind_addrstd::os::unix::net::UnixDatagram::connect_addrstd::os::unix::net::UnixDatagram::send_to_addrstd::os::unix::net::UnixListener::bind_addrstd::path::Path::as_mut_os_strstd::sync::OnceLockCARGO_PKG_READMEsparse the default protocol for crates.iocargo logoutlibtest from supporting -Zunstable-optionslet _ = expr position.sign-ext and mutable-globals features in codegen
This may cause incompatibility with older execution environments.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.
Copy fields.cmpxchg16b target feature on x86 and x86_64.Self: Autotrait bounds on dyn-safe trait methods.str as containing [u8] for auto trait purposes.*-pc-windows-gnu on CI to mingw-w64 v10 and GCC 12.2.true and false as boolean flags in compiler arguments.repr(C) enums to c_int size.DispatchFromDyn for cell types, allowing downstream experimentation with custom method receivers.fmt::Arguments::as_str() may return Some(_) in more cases after optimization, subject to change.AsFd and AsRawFd for Rc.These APIs are now stable in const contexts:
SocketAddr::newSocketAddr::ipSocketAddr::portSocketAddr::is_ipv4SocketAddr::is_ipv6SocketAddrV4::newSocketAddrV4::ipSocketAddrV4::portSocketAddrV6::newSocketAddrV6::ipSocketAddrV6::portSocketAddrV6::flowinfoSocketAddrV6::scope_idcargo fix or cargo clippy --fix when compilation warnings are auto-fixable.cargo add if you try to install a library crate.CARGO_BIN_NAME environment variable also for binary examples.rustdoc::all group.!.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.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_HOME in the [env] configuration table. Cargo itself doesn’t pick up this value, but recursive calls to cargo would, which was not intended.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.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.
@revoked and a better error message for @cert-authority in Cargo’s SSH host key verification$prefix-clang as clang in linker detection codealloc on stable without requiring the
definition of a handler for allocation failure. Defining custom handlers is still unstable.efiapi calling convention.bindings_with_variant_name to deny-by-defaultarmv7-sony-vita-newlibeabihf as a tier 3 targetstd::task::Context !Send and !SyncOnceWith & RepeatWithVec -> VecDeque conversion guarantee{core,std}::pin::pin!impl From<bool> for {f32,f64}std::path::MAIN_SEPARATOR_STRimpl DerefMut for PathBufThese APIs are now stable in const contexts:
cargo build --verbose tells you more about why it recompiles.net.git-fetch-with-cli option enabledSEMICOLON_IN_EXPRESSIONS_FROM_MACROS to future-incompat report--target by default for -Zgcc-ld=lld on wasmIMPLIED_BOUNDS_ENTAILMENT to Deny + ReportNowstd::task::Context no longer implements Send and SyncThese changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.
x86_64-pc-windows-msvcx86_64-apple-darwinclippy::uninlined_format_args to pedantic.Sized predicates coinductive, allowing cycles.#[must_use] annotations on async fn also affect the Future::Output.cfg(FALSE).C or cdecl.verbatim.Added, updated, and removed targets:
powerpc64-ibm-aix.mipsel-sony-psx.no_std targets for the QNX Neutrino RTOS,
aarch64-unknown-nto-qnx710 and x86_64-pc-nto-qnx710.aarch64-unknown-uefi, i686-unknown-uefi, and x86_64-unknown-uefi.linuxkernel targets (not used by the actual kernel).Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
crossbeam-channel into std::sync::mpsc.Eq and Hash for ControlFlow.compiler_builtins with -C panic=abort.{integer}::checked_ilog{integer}::checked_ilog2{integer}::checked_ilog10{integer}::ilog{integer}::ilog2{integer}::ilog10NonZeroU*::ilog2NonZeroU*::ilog10NonZero*::BITSThese APIs are now stable in const contexts:
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.&& 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.-export-dynamic to wasm-ld.main is now mangled as __main_void on wasm32-wasi.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.
repr(Int) enums
must_use on impl Trait for supertraits
This makes impl ExactSizeIterator respect the existing #[must_use] annotation on Iterator...=X in patternsclippy::for_loops_over_fallibles lint into rustcsym operands in inline assembly#[derive(Default)] on a generic #[default] enum adding unnecessary Default boundsproc_macro::Span::source_textuX::{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}AsFd implementations for stdio lock types on WASI.impl TryFrom<Vec<T>> for Box<[T; N]>core::hint::black_boxDuration::try_from_secs_{f32,f64}Option::unzipstd::os::fdcargo remove to remove dependencies from Cargo.tomlcargo publish now waits for the new version to be downloadable before exitingSee detailed release notes for more.
ProceduralMasquerade hack to older versions of rental__heap_base and __data_end on wasm32-wasi.__wasm_init_memory on WebAssembly.__tls_* on wasm32-unknown-unknown.libresolv in libstd on Darwinlibstd no longer pull in libiconv.dylib on Darwin)order_dependent_trait_objects show up in future-breakage reportsThese changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.
as casts of enums with #[non_exhaustive] variantslet elselet_underscore_drop and let_underscore_lock from Clippybreaking from arbitrary labeled blocks (“label-break-value”)MaybeUninit is the correct way to work with uninitialized memory.Drop impl on foreign ADTsspecial_module_name lint-C instrument-coverageNew targets:
PartialEq::ne in derive(PartialEq)BCRYPT_RNG_ALG_HANDLE by defaultSystem with direct system allocator callsstd::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.std::backtrace::BacktraceBound::as_refstd::io::read_to_string<*const T>::cast_mut<*mut T>::cast_constThese APIs are now stable in const contexts:
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.#![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.lld. For more information, see issue 102754.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.
x.sh and x.ps1 shell scripts&T if every byte in T is inside an UnsafeCellunused_tuple_struct_fields, similar to the existing warning for unused struct fields. This lint will become warn-by-default in the future.#[used] as llvm.compiler.used for ELF targets--diagnostic-width compiler flag to define the terminal width.rust-lld for iOS, tvOS and watchOSwrite! or writeln! into an OsString: Implement fmt::Write for OsStringFusedIterator for std::net::[Into]Incomingimpl<T: AsRawFd> AsRawFd for {Arc,Box}<T>ptr::copy and ptr::swap are doing untyped copiesavailable_parallelismmem::uninitializedfuture::IntoFuturefuture::poll_fntask::ready!num::NonZero*::checked_mulnum::NonZero*::checked_pownum::NonZero*::saturating_mulnum::NonZero*::saturating_pownum::NonZeroI*::absnum::NonZeroI*::checked_absnum::NonZeroI*::overflowing_absnum::NonZeroI*::saturating_absnum::NonZeroI*::unsigned_absnum::NonZeroI*::wrapping_absnum::NonZeroU*::checked_addnum::NonZeroU*::checked_next_power_of_twonum::NonZeroU*::saturating_addos::unix::process::CommandExt::process_groupos::windows::fs::FileTypeExt::is_symlink_diros::windows::fs::FileTypeExt::is_symlink_fileThese types were previously stable in std::ffi, but are now also available in core and alloc:
core::ffi::CStrcore::ffi::FromBytesWithNulErroralloc::ffi::CStringalloc::ffi::FromVecWithNulErroralloc::ffi::IntoStringErroralloc::ffi::NulErrorThese types were previously stable in std::os::raw, but are now also available in core::ffi and std::ffi:
ffi::c_charffi::c_doubleffi::c_floatffi::c_intffi::c_longffi::c_longlongffi::c_scharffi::c_shortffi::c_ucharffi::c_uintffi::c_ulongffi::c_ulonglongffi::c_ushortThese APIs are now usable in const contexts:
workspace.package
and
workspace.dependencies
for more details on how to define these common settings.--target flags to build for
multiple targets at once, and the
build.target
config option may now take an array of multiple targets.--jobs argument can now take a negative number to count backwards from
the max CPUs.cargo add will now update Cargo.lock.--crate-type
flag to cargo rustc to override the crate type.rev field.-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 versionstransmute_copy’s U is not larger than TBTreeMap was fixed that allowed data it was borrowing to be dropped before the container.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.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.
Vec::insert for the case where index == len.impl Trait args.cenum_impl_drop_cast warnings deny-by-default.-C panic=abort is used regardless of declared ABI.bundle native library modifier, also removing the
deprecated static-nobundle linking kind.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Copy, Clone, PartialEq and Eq for core::fmt::Alignment.ptr::null and null_mut to all thin (including extern) types.impl Read and Write for VecDeque<u8>.[OsStr]::join.Hash for core::alloc::Layout.OsString.std::mem::needs_drop accept ?Sized.impl Termination for Infallible and then make the Result impls of Termination more generic./proc/self/mem.array::from_fnBox::into_pinBinaryHeap::try_reserveBinaryHeap::try_reserve_exactOsString::try_reserveOsString::try_reserve_exactPathBuf::try_reservePathBuf::try_reserve_exactPath::try_existsRef::filter_mapRefMut::filter_mapNonNull::<[T]>::lenToOwned::clone_intoIpv6Addr::to_ipv4_mappedunix::io::AsFdunix::io::BorrowedFd<'fd>unix::io::OwnedFdwindows::io::AsHandlewindows::io::BorrowedHandle<'handle>windows::io::OwnedHandlewindows::io::HandleOrInvalidwindows::io::HandleOrNullwindows::io::InvalidHandleErrorwindows::io::NullHandleErrorwindows::io::AsSocketwindows::io::BorrowedSocket<'handle>windows::io::OwnedSocketthread::scopethread::Scopethread::ScopedJoinHandleThese APIs are now usable in const contexts:
array::from_refslice::from_refintrinsics::copyintrinsics::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_nonoverlappingstr::from_utf8Utf8Error::error_lenUtf8Error::valid_up_toCondvar::newMutex::newRwLock::new--config path command-line argument.CARGO_PKG_RUST_VERSION.#[link] attributes are now checked more strictly, which may introduce
errors for invalid attribute arguments that were previously ignored.Duration. The converted
duration can differ slightly from what it was.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
Rust 1.62.1 addresses a few recent regressions in the compiler and standard library, and also mitigates a CPU vulnerability on Intel SGX.
impl Trait return types.async fn lifetimes.x86_64-fortanix-unknown-sgx target added a mitigation for the
MMIO stale data vulnerability, advisory INTEL-SA-00615.#[derive(Default)] on enums with a #[default] variantconst functions may now specify extern "C" or extern "Rust"unaligned_references lint deny-by-default
This lint is also a future compatibility lint, and is expected to eventually
become a hard error.#[thread_local] attribute on non-static itemsaarch64-pc-windows-gnullvm and x86_64-pc-windows-gnullvm targets*x86_64-unknown-none target to Tier 2** Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
bool::then_somef32::total_cmpf64::total_cmpStdin::lineswindows::CommandExt::raw_argimpl<T: Default> Default for AssertUnwindSafe<T>From<Rc<str>> for Rc<[u8]>From<Arc<str>> for Arc<[u8]>FusedIterator for EncodeWidecargo add command for adding dependencies to Cargo.toml from
the command-line.
docsname@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.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).@ argfile support, which will use “response files” if the
command-line to rustc exceeds the operating system’s limit.cargo test now passes --target to rustdoc if the specified target is
the same as the host target.
#10594macro_rules! macros, matching other private itemsFile reads or writes cannot
complete synchronously.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
const fn signatures can now include generic trait boundsconst fn signatures can now use impl Trait in argument and return positionconst fnimpl Trait return type#[link] attributes and on the command line, as well as the whole-archive modifier specifically, are now supportedchar type is now described as UTF-32 in debuginfo#[target_feature] attribute can now be used with aarch64 features#[target_feature = "adx"] is now stableManuallyDrop<T> is now documented to have the same layout as T#[ignore = "…"] messages are printed when running testsstd::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 inputsstd::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.Pin::static_mutPin::static_refVec::retain_mutVecDeque::retain_mutWrite for Cursor<[u8; N]>std::os::unix::net::SocketAddr::from_pathnamestd::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_finishedThese 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_rangeNo feature changes, but see compatibility notes.
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
a depends on b then a should go first and b second)+whole-archive modifier.ident matchers wrapped in groups# in r# raw string literals is now required to be less than 256cargo vendor now only accepts one value for each --sync flagcfg 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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
#[cfg(panic = "...")] for either "unwind" or "abort".#[cfg(target_has_atomic = "...")] for each integer size and "ptr".+crt-static and relocation-model=pic on x86_64-unknown-linux-gnuunreachable_pub lints on nested and glob public reexport-Z instrument-coverage as -C instrument-coverage-Z print-link-args as --print link-argsmips64-openwrt-linux-musl*armv7-unknown-linux-uclibceabi (softfloat)*RUST_BACKTRACE=full by default* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
sort_by_cached_keyDuration::try_from_secs_f32/f64 accuracy by directly processing exponent and mantissaInstant::{duration_since, elapsed, sub} saturatingInstant::nowBuildHasherDefault, iter::Empty and future::Pending covariantArc::new_cyclicRc::new_cyclicslice::EscapeAscii<[u8]>::escape_asciiu8::escape_asciiVec::spare_capacity_mutMaybeUninit::assume_init_dropMaybeUninit::assume_init_readi8::abs_diffi16::abs_diffi32::abs_diffi64::abs_diffi128::abs_diffisize::abs_diffu8::abs_diffu16::abs_diffu32::abs_diffu64::abs_diffu128::abs_diffusize::abs_diffDisplay for io::ErrorKindFrom<u8> for ExitCodeNot for ! (the “never” type)Assign<$t> for Wrapping<$t>arch::is_aarch64_feature_detected!toml-rs to toml_edit-Ztimings as --timingscargo:rustc-link-arg-* types from build script output.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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
-Cremark#[test]-like built-in attribute macro is present multiple times.-Z emit-future-incompat as --json future-incompatThis 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.
std::thread::available_parallelismResult::copiedResult::clonedarch::asm!arch::global_asm!ops::ControlFlow::is_breakops::ControlFlow::is_continueTryFrom<char> for u8char::TryFromCharError
implementing Clone, Debug, Display, PartialEq, Copy, Eq, Erroriter::zipNonZeroU8::is_power_of_twoNonZeroU16::is_power_of_twoNonZeroU32::is_power_of_twoNonZeroU64::is_power_of_twoNonZeroU128::is_power_of_twoNonZeroUsize::is_power_of_twoDoubleEndedIterator for ToLowercaseDoubleEndedIterator for ToUppercaseTryFrom<&mut [T]> for [T; N]UnwindSafe for OnceRefUnwindSafe for OnceConst-stable:
mem::MaybeUninit::as_ptrmem::MaybeUninit::assume_initmem::MaybeUninit::assume_init_refffi::CStr::from_bytes_with_nul_uncheckedstrip profile option--release as -rterm.quiet configuration--host from cargo {publish,search,login}#![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.#[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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
std::fs::remove_dir_all (CVE-2022-21658)useless_format Clippy lintnon_send_fields_in_send_ty Clippy lint to nursery{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.Unsize have been relaxed.strip option to remove these symbols to produce smaller release binaries. Note that this release only includes support in rustc, not directly in cargo.-Cremarkx86_64-unknown-none at Tier 3** Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
#[must_use] annotations where appropriate, 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.copy and copy_nonoverlappingRefUnwindSafe for Rc<T>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).Metadata::is_symlinkPath::is_symlink{integer}::saturating_divOption::unwrap_uncheckedResult::unwrap_uncheckedResult::unwrap_err_uncheckedFile::optionsThese APIs are now usable in const contexts:
Duration::newDuration::checked_addDuration::saturating_addDuration::checked_subDuration::saturating_subDuration::checked_mulDuration::saturating_mulDuration::checked_divstd::process::Command will no longer search the current directory for executables.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
#[derive] and will see the original (pre-cfg) input.m!{ .. }.method() and m!{ .. }?.Clone and Debug implementations during dead code analysis.armv6k-nintendo-3ds at Tier 3*.armv7-unknown-linux-uclibceabihf at Tier 3*.m68k-unknown-linux-gnu at Tier 3*.aarch64-kmc-solid_asp3, armv7a-kmc-solid_asp3-eabi, armv7a-kmc-solid_asp3-eabihf* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
Vec::leak#[repr(i8)] to OrderingFile::read_to_end and read_to_string#[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.[T; N]::as_mut_slice[T; N]::as_slicecollections::TryReserveErrorHashMap::try_reserveHashSet::try_reserveString::try_reserveString::try_reserve_exactVec::try_reserveVec::try_reserve_exactVecDeque::try_reserveVecDeque::try_reserve_exactIterator::map_whileiter::MapWhileproc_macro::is_availableCommand::get_programCommand::get_argsCommand::get_envsCommand::get_current_dirCommandArgsCommandEnvsThese APIs are now usable in const contexts:
Clone and Debug implementations during dead code analysis.
This will break some builds that set #![deny(dead_code)].These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
binding @ pattern can now also introduce new bindings.const fn.--force-warn.
This feature is primarily intended for usage by cargo fix, rather than end users.aarch64-apple-ios-sim to Tier 2*.powerpc-unknown-freebsd at Tier 3*.riscv32imc-esp-espidf at Tier 3*.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
AtomicU{64,128} over Mutex for Instant backsliding protection.
For this use case, atomics scale much better under contention.Extend<(A, B)> for (Extend<A>, Extend<B>)impl From<[(K, V); N]> for all collections.P: Unpin bound on impl Future for Pin.=). 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.std::os::unix::fs::chrootUnsafeCell::raw_getBufWriter::into_partscore::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}
These APIs were previously stable in std, but are now also available in core.Vec::shrink_toString::shrink_toOsString::shrink_toPathBuf::shrink_toBinaryHeap::shrink_toVecDeque::shrink_toHashMap::shrink_toHashSet::shrink_toThese APIs are now usable in const contexts:
SEMICOLON_IN_EXPRESSIONS_FROM_MACROS warn by defaultlibc::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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
X..), which will start at X and
will end at the maximum value of the integer.std::prelude (e.g. use std::prelude::rust_2021::*;).* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
string::Drain now implements AsRef<str> and AsRef<[u8]>.Bound::clonedDrain::as_strIntoInnerError::into_errorIntoInnerError::into_partsMaybeUninit::assume_init_mutMaybeUninit::assume_init_refMaybeUninit::writearray::mapops::ControlFlowx86::_bittestx86::_bittestandcomplementx86::_bittestandresetx86::_bittestandsetx86_64::_bittest64x86_64::_bittestandcomplement64x86_64::_bittestandreset64x86_64::_bittestandset64The following previously stable functions are now const.
cargo test.cargo metadata now includes the "default_run"
field from the manifest.cargo d as an alias for cargo doc.{lib} as formatting option for cargo tree to print the "lib_name"
of packages.CTRL+F in your browser.#[doc(hidden)] will no longer appear in the
“Trait Implementations” section.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.process::Command on Windows now
behaves as expected. Previously using environment variables with
Command would cause them to be ASCII-uppercased.rustdoc::RUSTFLAGS is no longer set for build scripts. Build scripts
should use CARGO_ENCODED_RUSTFLAGS instead. See the
documentation
for more details.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:
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.
/lib/rustlib/<target-triple>/target.json where / is the “sysroot”
directory. You can find your sysroot directory by running
rustc --print sysroot.wasm as a target_family for WebAssembly platforms.#[target_feature] on safe functions when targeting
WebAssembly platforms.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 for more information on Rust’s tiered platform support.
panic::panic_any will now #[track_caller].OutOfMemory as a variant of io::ErrorKind.proc_macro::Literal now implements FromStr.BTreeMap::into_keysBTreeMap::into_valuesHashMap::into_keysHashMap::into_valuesarch::wasm32VecDeque::binary_searchVecDeque::binary_search_byVecDeque::binary_search_by_keyVecDeque::partition_point--prune <spec> option to cargo-tree to remove a package from
the dependency graph.--depth option to cargo-tree to print only to a certain depth
in the tree no-proc-macro value to cargo-tree --edges to hide procedural
macro dependencies.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.? is no longer permitted in closures for inferred types.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.◆ 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.| (OR) on complete patterns. E.g.
: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.wasm64-unknown-unknown target.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
android_set_abort_message on
Android platforms when available.slice::IterMut<'_, T> now implements AsRef<[T]>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.(Bound<usize>, Bound<usize>).BITS associated constant to all numeric types.AtomicBool::fetch_updateAtomicPtr::fetch_updateBTreeMap::retainBTreeSet::retainBufReader::seek_relativeDebugStruct::non_exhaustiveDuration::MAXDuration::ZERODuration::is_zeroDuration::saturating_addDuration::saturating_mulDuration::saturating_subErrorKind::UnsupportedOption::insertOrdering::is_eqOrdering::is_geOrdering::is_gtOrdering::is_leOrdering::is_ltOrdering::is_neOsStr::is_asciiOsStr::make_ascii_lowercaseOsStr::make_ascii_uppercaseOsStr::to_ascii_lowercaseOsStr::to_ascii_uppercasePeekable::peek_mutRc::decrement_strong_countRc::increment_strong_countVec::extend_from_withinarray::from_mutarray::from_refcmp::max_by_keycmp::max_bycmp::min_by_keycmp::min_byf32::is_subnormalf64::is_subnormalHEAD branch is not
“master”. This also includes a switch to the version 3 Cargo.lock format
which can handle default branches correctly.unpacked split-debuginfo.authors field is no longer included in Cargo.toml for new
projects.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.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.RUSTC_FORCE_INCREMENTAL=1 environment variable added in 1.52.1.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
std::sys::windows::alloc implementation.get_blanket_implsThis 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.
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.Added tier 3* support for the following targets.
s390x-unknown-linux-muslriscv32gc-unknown-linux-musl & riscv64gc-unknown-linux-muslpowerpc-unknown-openbsd* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
OsString now implements Extend and FromIterator.cmp::Reverse now has #[repr(transparent)] representation.Arc<impl Error> now implements error::Error.const.Arguments::as_strchar::MAXchar::REPLACEMENT_CHARACTERchar::UNICODE_VERSIONchar::decode_utf16char::from_digitchar::from_u32_uncheckedchar::from_u32slice::partition_pointstr::rsplit_oncestr::split_onceThe following previously stable APIs are now const.
char::len_utf8char::len_utf16char::to_ascii_uppercasechar::to_ascii_lowercasechar::eq_ignore_ascii_caseu8::to_ascii_uppercaseu8::to_ascii_lowercaseu8::eq_ignore_ascii_caserustdoc:: (e.g. #[warn(rustdoc::broken_intra_doc_links)]).
Using the old style is still allowed, and will become a warning in
a future release.- [x] Complete
- [ ] Todocargo test -- foo bar will run all tests that match foo and bar.std library on Windows,
allowing you to see std symbols when debugging.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
RUSTC_BOOTSTRAP.x86_64-rumprun-netbsd target.x86_64-sun-solaris target in favor of x86_64-pc-solaris.,, , and \t as delimiters for specifying
languages in code blocks.pub_use_of_private_extern_crateproc-macro-hack versions. A cargo update should be sufficient to fix this in all cases.#[derive] into a regular macro attributestructs 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.
-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.aarch64_be-unknown-linux-gnu,
aarch64-unknown-linux-gnu_ilp32, and aarch64_be-unknown-linux-gnu_ilp32 targets.i386-unknown-linux-gnu and i486-unknown-linux-gnu targets.target-cpu=native option will now detect individual features of CPUs.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
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.Arc::decrement_strong_countArc::increment_strong_countOnce::call_once_forcePeekable::next_if_eqPeekable::next_ifSeek::stream_positionarray::IntoIterpanic::panic_anyptr::addr_of!ptr::addr_of_mut!slice::fill_withslice::split_inclusive_mutslice::split_inclusiveslice::strip_prefixslice::strip_suffixstr::split_inclusivesync::OnceStatetask::WakeVecDeque::rangeVecDeque::range_mutsplit-debuginfo profile option to control the -Csplit-debuginfo
codegen option.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.Deref traits.--default-theme flag which sets the default theme to use for
documentation.Various improvements to intra-doc links:
slice.Vec<T>.wasm-bindgen ABI, and instead use the wasm32 ABI.rustc no longer promotes division, modulo and indexing operations to const that
could fail.armv5te-unknown-linux-gnueabisparc64-unknown-linux-gnuthumbv7neon-unknown-linux-gnueabihfarmv7-unknown-linux-gnueabix86_64-unknown-linux-gnux32atomic::spin_loop_hint has been deprecated. It’s recommended to use hint::spin_loop instead.const values for x in [x; N] array expressions.
This has been technically possible since 1.38.0, as it was unintentionally stabilized.ManuallyDrop<T> union fields are now considered safe.armv5te-unknown-linux-uclibceabi target.aarch64-apple-ios-macabi target.x86_64-unknown-freebsd is now built with the full toolset.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
proc_macro::Punct now implements PartialEq<char>.ops::{Index, IndexMut} are now implemented for fixed sized arrays of any length.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.bool::thenbtree_map::Entry::or_insert_with_keyf32::clampf64::clamphash_map::Entry::or_insert_with_keyOrd::clampRefCell::takeslice::fillUnsafeCell::get_mutThe following previously stable methods are now const.
IpAddr::is_ipv4IpAddr::is_ipv6IpAddr::is_unspecifiedIpAddr::is_loopbackIpAddr::is_multicastIpv4Addr::octetsIpv4Addr::is_loopbackIpv4Addr::is_privateIpv4Addr::is_link_localIpv4Addr::is_multicastIpv4Addr::is_broadcastIpv4Addr::is_documentationIpv4Addr::to_ipv6_compatibleIpv4Addr::to_ipv6_mappedIpv6Addr::segmentsIpv6Addr::is_unspecifiedIpv6Addr::is_loopbackIpv6Addr::is_multicastIpv6Addr::to_ipv4Layout::sizeLayout::alignLayout::from_size_alignpow 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.[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.--workspace flag to the cargo update command.compare_and_swap method on atomics has been deprecated. It’s
recommended to use the compare_exchange and compare_exchange_weak methods instead.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.forbid lint at the same level that it was set is now a hard error.panic! calls by supplying your own macro. It’s
recommended to use the #[panic_handler] attribute to provide your own implementation.struct Foo {};) now produce a warning.Drop, and you can now have a field in a union
with ManuallyDrop<T>.aarch64-unknown-linux-gnu.aarch64-apple-darwin.aarch64-pc-windows-msvc.mipsel-unknown-none.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
RangeInclusive now checks for exhaustion when calling contains and indexing.ToString::to_string now no longer shrinks the internal buffer in the default implementation.The following previously stable methods are now const.
cargo-package should now be independently reproducible.cargo-tree now marks proc-macro crates.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.i686-unknown-freebsd from host tier 2 to target tier 2 support.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
initial-exec Thread
Local Storage model.system to the llvm-libunwind bootstrap config option.--color for configuring terminal color support to bootstrap.unsafe keyword is now syntactically permitted on modules. This
is still rejected semantically, but can now be parsed by procedural macros.-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.)-C target-feature=+crt-static on linux-gnu targets.
Note: If you’re using cargo you must explicitly pass the --target flag.aarch64-unknown-linux-musl.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
io::Write is now implemented for &ChildStdin &Sink, &Stdout,
and &Stderr.TryFrom<Vec<T>>.matches! macro now supports having a trailing comma.Vec<A> now implements PartialEq<[B]> where A: PartialEq<B>.RefCell::{replace, replace_with, clone} methods now all use #[track_caller].The following previously stable methods are now const fn’s:
Option::is_someOption::is_noneOption::as_refResult::is_okResult::is_errResult::as_refOrdering::reverseOrdering::thenrustdoc 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.#[doc(alias = "<alias>")] on items to add search aliases
when searching through rustdoc’s UI.'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.&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._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.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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
rustc from source now uses ninja by default over make.
You can continue building with make by setting ninja=false in
your config.toml.fewer_names in uncached_llvm_typeensure_sufficient_stack() non-generic-C control-flow-guard codegen option, which enables
Control Flow Guard for Windows platforms, and is ignored on other
platforms.thumbv4t-none-eabi target.RUST_BACKTRACE’s output is now more compact.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
CStr now implements Index<RangeFrom<usize>>.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.Ident::new_rawRange::is_emptyRangeInclusive::is_emptyResult::as_derefResult::as_deref_mutVec::leakpointer::offset_fromf32::TAUf64::TAUThe following previously stable APIs have now been made const.
new method for all NonZero integers.checked_add,checked_sub,checked_mul,checked_neg, checked_shl,
checked_shr, saturating_add, saturating_sub, and saturating_mul
methods for all integers.checked_abs, saturating_abs, saturating_neg, and signum for all
signed integers.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.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 = 3cargo-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.{} && false in tail expressions.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.linux-gnu targets now require minimum kernel 2.6.32 and glibc 2.11.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.)x.py. You can read details about this change in the “Changes to x.py defaults” post on the Inside Rust blog.if, match, and loop expressions can now be used in const functions.&[T]) in
const functions.#[track_caller] attribute can now be added to functions to use the
function’s caller’s location information for panic messages.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.cdylib target on Apple iOS and tvOS platforms.x86_64-unknown-linux-musl.mem::forget is now a const fn.String now implements From<char>.leading_ones, and trailing_ones methods have been stabilised for all
integer types.vec::IntoIter<T> now implements AsRef<[T]>.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]>.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.abi_blacklist has been renamed
to unsupported_abis. The old name will still continue to work.Drop.
This was previously accepted but will become a hard error in a future release.#[repr(i128)] or #[repr(u128)]. This representation is currently only
allowed on enums.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.{f32, f64}::asinh now returns the correct values for negative numbers.rustc would erroneously allow
you to pass a shorter lifetime than expected.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.#[should_panic] are broken on ARMv7 while running
under QEMU.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.macro_rules!) macro.target-feature
flag. E.g. -C target-feature=+avx2 -C target-feature=+fma is now
equivalent to -C target-feature=+avx2,+fma.force-unwind-tables flag. This option allows
rustc to always generate unwind tables regardless of panic strategy.embed-bitcode flag. This codegen flag allows rustc
to include LLVM bitcode into generated rlibs (this is on by default).tiny value to the code-model codegen flag.mipsel-sony-psp target.thumbv7a-uwp-windows-msvc target.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
net::{SocketAddr, SocketAddrV4, SocketAddrV6} now implements PartialOrd
and Ord.proc_macro::TokenStream now implements Default.char with
ops::{Range, RangeFrom, RangeFull, RangeInclusive, RangeTo} to iterate over
a range of codepoints. E.g.
you can now write the following;
OsString now implements FromStr.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.fetch_min, and fetch_max methods have been added to all atomic
integer types.fetch_update method has been added to all atomic integer types.Arc::as_ptrBTreeMap::remove_entryRc::as_ptrrc::Weak::as_ptrrc::Weak::from_rawrc::Weak::into_rawstr::strip_prefixstr::strip_suffixsync::Weak::as_ptrsync::Weak::from_rawsync::Weak::into_rawchar::UNICODE_VERSIONSpan::resolved_atSpan::located_atSpan::mixed_siteunix::process::CommandExt::arg0~~outdated information~~ becomes “{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.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.Syntax-only changes
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.
-C codegen-units flag in incremental mode.
Additionally when in incremental mode rustc defaults to 256 codegen units.catch_unwind to have zero-cost, unless unwinding is enabled and
a panic is thrown.aarch64-unknown-none and
aarch64-unknown-none-softfloat targets.arm64-apple-tvos and
x86_64-apple-tvos targets.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.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.PathBuf::with_capacityPathBuf::capacityPathBuf::clearPathBuf::reservePathBuf::reserve_exactPathBuf::shrink_to_fitf32::to_int_uncheckedf64::to_int_uncheckedLayout::align_toLayout::pad_to_alignLayout::arrayLayout::extendcargo 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
...cargo tree -d (short for cargo tree --duplicates)..a extension, rather than the previous .lib.-C no_integrated_as flag from rustc.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.mem::{zeroed, uninitialised} will now panic when used with types that do
not allow zero initialization such as NonZeroU8. This was
previously a warning.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.These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools.
cargo package --list not working with unpublished dependencies.&{number} (e.g. &1.0) not having
the type inferred correctly.#[cfg()] can now be used on if expressions.Syntax only changes
type Foo: Ord syntactically.self in all fn contexts.fn syntax + cleanup item parsing.item macro fragments can be interpolated into traits, impls, and extern blocks.
For example, you may now write:
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.
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).windows-gnu.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.u32::MAX or
f32::NAN with no imports.u8::is_ascii is now const.String now implements AsMut<str>.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.HashMap and HashSet.string::FromUtf8Error now implements Clone + Eq.[profile]s in your .cargo/config, or through
your environment.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").const_err lint were deemed unrelated to const
evaluation, and have been moved to the unconditional_panic and
arithmetic_overflow lints.assert! macro is now a hard error. This
has been a warning since 1.36.0.Self not having the correctly inferred type. This incorrectly
led to some instances being accepted, and now correctly emits a hard error.These changes provide no direct user facing benefits, but represent significant
improvements to the internals and overall performance of rustc and
related tools.
opt-level=3 instead of 2.#[inline]-ing certain hot functions.Drop terminators for enum variants without drop glueYou can now use the slice pattern syntax with subslices. e.g.
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.impls (i.e. consts, types, and fns) may syntactically
leave out their bodies in favor of ;.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.
armv7a-none-eabi.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 for more information on Rust’s tiered platform support.
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.riscv64gc-unknown-linux-gnu.CondVar::wait_whileCondVar::wait_timeout_whileDebugMap::keyDebugMap::valueManuallyDrop::takematches!ptr::slice_from_raw_parts_mutptr::slice_from_raw_partsError::description has been deprecated, and its use will now produce a
warning. It’s recommended to use Display/to_string instead.Copy implsLayout::repeatimpl<T> From<Foo> for Vec<T> {}.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.format_args macro.
Previously identifiers starting with an underscore were not allowed.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.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.'labels.i686-unknown-dragonfly target.riscv64gc-unknown-linux-gnu target.@path syntax
to rustc. Note that the format differs somewhat from what is
found in other tooling; please see the documentation for
more information.--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 for more information on Rust’s tiered platform support.
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.Result::map_orResult::map_or_elsestd::rc::Weak::weak_countstd::rc::Weak::strong_countstd::sync::Weak::weak_countstd::sync::Weak::strong_countcargo-install will now reinstall the package if it detects that it is out
of date.[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.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.--theme, and check the
current theme with --check-theme.#[cfg(doc)] to compile an item when building documentation.You can now use tuple structs and tuple enum variant’s constructors in
const contexts. e.g.
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!();
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)].
thumbv7neon-unknown-linux-musleabihf target.aarch64-unknown-none-softfloat target.mips64-unknown-linux-muslabi64, and
mips64el-unknown-linux-muslabi64 targets.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
BTreeMap::get_key_valueHashMap::get_key_valueOption::as_deref_mutOption::as_derefOption::flattenUdpSocket::peer_addrf32::to_be_bytesf32::to_le_bytesf32::to_ne_bytesf64::to_be_bytesf64::to_le_bytesf64::to_ne_bytesf32::from_be_bytesf32::from_le_bytesf32::from_ne_bytesf64::from_be_bytesf64::from_le_bytesf64::from_ne_bytesmem::takeslice::repeattodo!--all-features) passed to a virtual workspace will
now produce an error. Previously these flags were ignored.dev-dependencies without including
a version.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.#[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.async functions and blocks with async fn, async move {}, and
async {} respectively, and you can now call .await on async expressions.cfg, cfg_attr, allow, warn,
deny, forbid as well as inert helper attributes used by procedural macro
attributes applied to items. e.g.
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!(),
}
}i686-unknown-uefi target.sparc64-unknown-openbsd target.--show-output argument to test binaries to print the
output of successful tests.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
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.abs, wrapping_abs, and overflowing_abs numeric functions are
now const.version.--all flag has been renamed to --workspace. Using
--all is now deprecated.rustdoc now requires rustc to be installed and in the same directory to
run tests. This should improve performance when running a large
amount of doctests.try! macro will now issue a deprecation warning. It is
recommended to use the ? operator instead.asinh(-0.0) now correctly returns -0.0. Previously this
returned 0.0.#[global_allocator] attribute can now be used in submodules.#[deprecated] attribute can now be used on macros.rustc. This will
improve compilation times in some cases. For further information please refer
to the “Evaluating pipelined rustc compilation” thread.aarch64-uwp-windows-msvc, i686-uwp-windows-gnu,
i686-uwp-windows-msvc, x86_64-uwp-windows-gnu, and
x86_64-uwp-windows-msvc targets.armv7-unknown-linux-gnueabi and
armv7-unknown-linux-musleabi targets.hexagon-unknown-linux-musl target.riscv32i-unknown-none-elf target.* Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
ascii::EscapeDefault now implements Clone and Display.Clone, Debug, Hash) are now
available at the same path as the trait. (e.g. The Clone derive macro
is available at std::clone::Clone). This also makes all built-in macros
available in std/core root. e.g. std::include_bytes!.str::Chars now implements Debug.slice::{concat, connect, join} now accepts &[T] in addition to &T.*const T and *mut T now implement marker::Unpin.Arc<[T]> and Rc<[T]> now implement FromIterator<T>.div_euclid,
rem_euclid) to all numeric primitives. Additionally checked,
overflowing, and wrapping versions are available for all
integer primitives.thread::AccessError now implements Clone, Copy, Eq, Error, and
PartialEq.iter::{StepBy, Peekable, Take} now implement DoubleEndedIterator.<*const T>::cast<*mut T>::castDuration::as_secs_f32Duration::as_secs_f64Duration::div_f32Duration::div_f64Duration::from_secs_f32Duration::from_secs_f64Duration::mul_f32Duration::mul_f64any::type_namecargo.--features option multiple times to enable
multiple features.x86_64-unknown-uefi platform can not be built with rustc
1.38.0.armv7-unknown-linux-gnueabihf platform is known to have
issues with certain crates such as libc.#[must_use] will now warn if the type is contained in a tuple,
Box, or an array and unused.cfg and cfg_attr attributes on
generic parameters._ as an identifier for consts. e.g. You can write
const _: u32 = 5;.#[repr(align(X)] on enums.? Kleene macro operator is now available in the
2015 edition.-C profile-generate
and -C profile-use flags. For more information on how to use profile
guided optimization, please refer to the rustc book.rust-lldb wrapper script should now work again.BufReader::bufferBufWriter::bufferCell::from_mutCell<[T]>::as_slice_of_cellsDoubleEndedIterator::nth_backOption::xorWrapping::reverse_bitsi128::reverse_bitsi16::reverse_bitsi32::reverse_bitsi64::reverse_bitsi8::reverse_bitsisize::reverse_bitsslice::copy_withinu128::reverse_bitsu16::reverse_bitsu32::reverse_bitsu64::reverse_bitsu8::reverse_bitsusize::reverse_bitsCargo.lock files are now included by default when publishing executable crates
with executables.default-run="foo" in [package] to specify the
default executable to use for cargo run.... for inclusive range patterns will now warn by default.
Please transition your code to using the ..= syntax for inclusive
ranges instead.dyn will now warn by default.
Please transition your code to use dyn Trait for trait objects instead.dyn Send + fmt::Debug is now equivalent to
dyn fmt::Debug + Send, where this was previously not the case.HashMap’s implementation has been replaced with hashbrown::HashMap implementation.TryFromSliceError now implements From<Infallible>.mem::needs_drop is now available as a const fn.alloc::Layout::from_size_align_unchecked is now available as a const fn.String now implements BorrowMut<str>.io::Cursor now implements Default.NonNull::{dangling, cast} are now const fns.alloc crate is now stable. alloc allows you to use a subset
of std (e.g. Vec, Box, Arc) in #![no_std] environments if the
environment has access to heap memory allocation.String now implements From<&String>.dbg! macro. dbg! will
return a tuple of each argument when there is multiple arguments.Result::{is_err, is_ok} are now #[must_use] and will produce a warning if
not used.VecDeque::rotate_leftVecDeque::rotate_rightIterator::copiedio::IoSliceio::IoSliceMutRead::read_vectoredWrite::write_vectoredstr::as_mut_ptrmem::MaybeUninitpointer::align_offsetfuture::Futuretask::Contexttask::RawWakertask::RawWakerVTabletask::Wakertask::Poll--offline flag to run cargo without accessing the network.You can find further change’s in Cargo’s 1.36.0 release notes.
There have been numerous additions and fixes to clippy, see Clippy’s 1.36.0 release notes for more details.
mem::MaybeUninit, mem::uninitialized use is no
longer recommended, and will be deprecated in 1.39.0.FnOnce, FnMut, and the Fn traits are now implemented for Box<FnOnce>,
Box<FnMut>, and Box<Fn> respectively.armv6-unknown-freebsd-gnueabihf and
armv7-unknown-freebsd-gnueabihf targets.wasm32-unknown-wasi target.Thread will now show its ID in Debug output.StdinLock, StdoutLock, and StderrLock now implement AsRawFd.alloc::System now implements Default.Debug output ({:#?}) for structs now has a trailing comma on the
last field.char::{ToLowercase, ToUppercase} now
implement ExactSizeIterator.NonZero numeric types now implement FromStr.Read trait bounds
on the BufReader::{get_ref, get_mut, into_inner} methods.dbg! macro without any parameters to print the file
and line where it is called.str::make_ascii_lowercasehash_map::{OccupiedEntry, VacantEntry} now implement Sync
and Send.f32::copysignf64::copysignRefCell::replace_withRefCell::map_splitptr::hashRange::containsRangeFrom::containsRangeTo::containsRangeInclusive::containsRangeToInclusive::containsOption::copiedcargo:rustc-cdylib-link-arg at build time to pass custom
linker arguments when building a cdylib. Its usage is highly
platform specific.redundant_closure Clippy lintmissing_const_for_fn Clippy lint#[deprecated = "reason"] as a shorthand for
#[deprecated(note = "reason")]. This was previously allowed by mistake
but had no effect.#[attr()],#[attr[]], and
#[attr{}] procedural macros.extern crate self as foo; to import your
crate’s root into the extern prelude.riscv64imac-unknown-none-elf and
riscv64gc-unknown-none-elf.-C linker-plugin-lto. This allows rustc to compile your Rust code
into LLVM bitcode allowing LLVM to perform LTO optimisations across C/C++ FFI
boundaries.powerpc64-unknown-freebsd.HashMap<K, V, S>’s and
HashSet<T, S>’s basic methods. Most notably you no longer require
the Hash trait to create an iterator.Ord trait bounds have been removed on some of BinaryHeap<T>’s basic
methods. Most notably you no longer require the Ord trait to create
an iterator.overflowing_neg and wrapping_neg are now const functions
for all numeric types.str is now generic over all types that
implement SliceIndex<str>.str::trim, str::trim_matches, str::trim_{start, end}, and
str::trim_{start, end}_matches are now #[must_use] and will
produce a warning if their returning type is unused.checked_pow, saturating_pow, wrapping_pow, and
overflowing_pow are now available for all numeric types. These are
equivalent to methods such as wrapping_add for the pow operation.Any::type_idError::type_idatomic::AtomicI16atomic::AtomicI32atomic::AtomicI64atomic::AtomicI8atomic::AtomicU16atomic::AtomicU32atomic::AtomicU64atomic::AtomicU8convert::Infallibleconvert::TryFromconvert::TryIntoiter::from_fniter::successorsnum::NonZeroI128num::NonZeroI16num::NonZeroI32num::NonZeroI64num::NonZeroI8num::NonZeroIsizeslice::sort_by_cached_keystr::escape_debugstr::escape_defaultstr::escape_unicodestr::split_ascii_whitespaceCommand::before_exec is being replaced by the unsafe method
Command::pre_exec and will be deprecated with Rust 1.37.0.ATOMIC_{BOOL, ISIZE, USIZE}_INIT is now deprecated as you
can now use const functions in static variables.cfg(target_vendor) attribute. E.g.
#[cfg(target_vendor="apple")] fn main() { println!("Hello Apple!"); }u8 that covers 0..=255 and
you would no longer be required to have a _ => unreachable!() case.if let and while let
expressions. You can do this with the same syntax as a match
expression. E.g.
if let and while let patterns. Using
this feature will by default produce a warning as this behaviour can be
unintuitive. E.g. if let _ = 5 {}let bindings, assignments, expression statements,
and irrefutable pattern destructuring in const functions.cfg_attr attribute.
E.g. #[cfg_attr(all(), must_use, optimize)]#[repr(packed)]
attribute. E.g. #[repr(packed(2))] struct Foo(i16, i32); is a struct
with an alignment of 2 bytes and a size of 6 bytes._. This allows you to
import a trait’s impls, and not have the name in the namespace. E.g.
Rc, Arc, and Pin as method receivers.rustc with the -Clinker-flavor
command line argument.x86_64-fortanix-unknown-sgx target support has been upgraded to
tier 2 support. Visit the platform support page for
information on Rust’s platform support.thumbv7neon-linux-androideabi and
thumbv7neon-unknown-linux-gnueabihf targets.x86_64-unknown-uefi target.overflowing_{add, sub, mul, shl, shr} are now const
functions for all numeric types.rotate_left, rotate_right, and wrapping_{add, sub, mul, shl, shr}
are now const functions for all numeric types.is_positive and is_negative are now const functions for
all signed numeric types.get method for all NonZero types is now const.count_ones, count_zeros, leading_zeros, trailing_zeros,
swap_bytes, from_be, from_le, to_be, to_le are now const for all
numeric types.Ipv4Addr::new is now a const functionunix::FileExt::read_exact_atunix::FileExt::write_all_atOption::transposeResult::transposeconvert::identitypin::Pinmarker::Unpinmarker::PhantomPinnedVec::resize_withVecDeque::resize_withDuration::as_millisDuration::as_microsDuration::as_nanoscargo publish --features or cargo publish --all-features.str::{trim_left, trim_right, trim_left_matches, trim_right_matches}
are now deprecated in the standard library, and their usage will now produce a warning.
Please use the str::{trim_start, trim_end, trim_start_matches, trim_end_matches}
methods instead.Error::cause method has been deprecated in favor of Error::source which supports
downcasting.--test-threads=1. It also runs the tests in deterministic order? operator in macro definitions. The ?
operator allows you to specify zero or one repetitions similar to the * and
+ operators.super, self, or crate, will
now always resolve to the item (enum, struct, etc.) available in the
module if present, before resolving to a external crate or an item the prelude.
E.g.
PhantomData<T> types.literal
specifier. This will match against a literal of any type.
E.g. 1, 'A', "Hello World"#[must_use]. This provides a warning if
a impl Trait or dyn Trait is returned and unused in the program.aarch64-pc-windows-msvc target.PathBuf now implements FromStr.Box<[T]> now implements FromIterator<T>.dbg! macro has been stabilized. This macro enables you to
easily debug expressions in your rust program. E.g.
The following APIs are now const functions and can be used in a
const context.
Cell::as_ptrUnsafeCell::getchar::is_asciiiter::emptyManuallyDrop::newManuallyDrop::into_innerRangeInclusive::startRangeInclusive::endNonNull::as_ptrslice::as_ptrstr::as_ptrDuration::as_secsDuration::subsec_millisDuration::subsec_microsDuration::subsec_nanosCStr::as_ptrIpv4Addr::is_unspecifiedIpv6Addr::newIpv6Addr::octetsi8::to_be_bytesi8::to_le_bytesi8::to_ne_bytesi8::from_be_bytesi8::from_le_bytesi8::from_ne_bytesi16::to_be_bytesi16::to_le_bytesi16::to_ne_bytesi16::from_be_bytesi16::from_le_bytesi16::from_ne_bytesi32::to_be_bytesi32::to_le_bytesi32::to_ne_bytesi32::from_be_bytesi32::from_le_bytesi32::from_ne_bytesi64::to_be_bytesi64::to_le_bytesi64::to_ne_bytesi64::from_be_bytesi64::from_le_bytesi64::from_ne_bytesi128::to_be_bytesi128::to_le_bytesi128::to_ne_bytesi128::from_be_bytesi128::from_le_bytesi128::from_ne_bytesisize::to_be_bytesisize::to_le_bytesisize::to_ne_bytesisize::from_be_bytesisize::from_le_bytesisize::from_ne_bytesu8::to_be_bytesu8::to_le_bytesu8::to_ne_bytesu8::from_be_bytesu8::from_le_bytesu8::from_ne_bytesu16::to_be_bytesu16::to_le_bytesu16::to_ne_bytesu16::from_be_bytesu16::from_le_bytesu16::from_ne_bytesu32::to_be_bytesu32::to_le_bytesu32::to_ne_bytesu32::from_be_bytesu32::from_le_bytesu32::from_ne_bytesu64::to_be_bytesu64::to_le_bytesu64::to_ne_bytesu64::from_be_bytesu64::from_le_bytesu64::from_ne_bytesu128::to_be_bytesu128::to_le_bytesu128::to_ne_bytesu128::from_be_bytesu128::from_le_bytesu128::from_ne_bytesusize::to_be_bytesusize::to_le_bytesusize::to_ne_bytesusize::from_be_bytesusize::from_le_bytesusize::from_ne_bytescargo c as an alias for cargo check._mm256_stream_si256, _mm256_stream_pd, _mm256_stream_ps have
been changed from *const to *mut as the previous implementation
was unsound.powerpc-unknown-netbsdimpl<'a> Reader for BufReader<'a> {} can now be
impl Reader for BufReader<'_> {}. Lifetimes are still required to be defined
in structs.const functions. These are currently
a strict minimal subset of the const fn RFC. Refer to the
language reference for what exactly is available.#[allow(clippy::filter_map)].#[no_mangle] and #[export_name] attributes can now be located anywhere in
a crate, not just in exported functions.num::NonZero* types to their raw equivalents using the
From trait. E.g. u8 now implements From<NonZeroU8>.&Option<T> into Option<&T> and &mut Option<T>
into Option<&mut T> using the From trait.*) a time::Duration by a u32.slice::align_toslice::align_to_mutslice::chunks_exactslice::chunks_exact_mutslice::rchunksslice::rchunks_mutslice::rchunks_exactslice::rchunks_exact_mutOption::replacepackage key in your dependencies.r#), e.g. let r#for = true;crate in paths. This allows you to refer to the
crate root in the path, e.g. use crate::foo; refers to foo in src/lib.rs.::.
Previously, using a external crate in a module without a use statement
required let json = ::serde_json::from_str(foo); but can now be written
as let json = serde_json::from_str(foo);.#[used] attribute to static items to prevent the
compiler from optimising them away, even if they appear to be unused,
e.g. #[used] static FOO: u32 = 1;use
syntax. Macros exported with #[macro_export] are now placed into
the root module of the crate. If your macro relies on calling other local
macros, it is recommended to export with the
#[macro_export(local_inner_macros)] attribute so users won’t have to import
those macros.pub, pub(crate)) in macros
using the vis specifier.#[attr("true")], and you can now
write #[attr(true)].#[panic_handler] attribute.riscv32imc-unknown-none-elf target.aarch64-unknown-netbsd targetThe following methods are replacement methods for trim_left, trim_right,
trim_left_matches, and trim_right_matches, which will be deprecated
in 1.33.0:
cargo run doesn’t require specifying a package in workspaces.cargo doc now supports --message-format=json. This is
equivalent to calling rustdoc --error-format=json.rustdoc allows you to specify what edition to treat your code as with the
--edition option.rustdoc now has the --color (specify whether to output color) and
--error-format (specify error format, e.g. json) options.rust-gdbgui script that invokes gdbgui with Rust
debug symbols.rustfmt or clippy are now
available, e.g. #[rustfmt::skip] will skip formatting the next item.rls-preview component on the windows-gnu targets has been restored.The standard library’s str::repeat function contained an out of bounds write
caused by an integer overflow. This has been fixed by deterministically
panicking when an overflow happens.
Thank you to Scott McMurray for responsibly disclosing this vulnerability to us.
powerpc64le-unknown-linux-musl target.aarch64-unknown-hermit and x86_64-unknown-hermit targets.Once::call_once no longer requires Once to be 'static.BuildHasherDefault now implements PartialEq and Eq.Box<CStr>, Box<OsStr>, and Box<Path> now implement Clone.PartialEq<&str> for OsString and PartialEq<OsString>
for &str.Cell<T> now allows T to be unsized.SocketAddr is now stable on Redox.--locked to disable this behavior.cargo-install will now allow you to cross compile an install
using --target.cargo-fix subcommand to automatically move project code from
2015 edition to 2018.cargo doc can now optionally document private types using the
--document-private-items flag.rustdoc now has the --cap-lints option which demotes all lints above
the specified level to that level. For example --cap-lints warn
will demote deny and forbid lints to warn.rustc and rustdoc will now have the exit code of 1 if compilation
fails and 101 if there is a panic.rustup component add clippy-preview.str::{slice_unchecked, slice_unchecked_mut} are now deprecated.
Use str::get_unchecked(begin..end) instead.std::env::home_dir is now deprecated for its unintuitive behavior.
Consider using the home_dir function from
https://crates.io/crates/dirs instead.rustc will no longer silently ignore invalid data in target spec.cfg attributes and --cfg command line flags are now more
strictly validated.#[repr(transparent)] attribute is now stable. This attribute
allows a Rust newtype wrapper (struct NewType<T>(T);) to be represented as
the inner type across Foreign Function Interface (FFI) boundaries.pure, sizeof, alignof, and offsetof have been unreserved
and can now be used as identifiers.GlobalAlloc trait and #[global_allocator] attribute are now
stable. This will allow users to specify a global allocator for
their program.#[test] attribute can now return
Result<(), E: Debug> in addition to ().lifetime specifier for macro_rules! is now stable. This
allows macros to easily target lifetimes.s and z optimisation levels are now stable. These optimisations
prioritise making smaller binary sizes. z is the same as s with the
exception that it does not vectorise loops, which typically results in an even
smaller binary.--error-format=short this option will provide a more compressed output of
rust error messages.macro_exports.Default for &mut str.From<bool> for all integer and unsigned number types.Extend for ().Debug implementation of time::Duration should now be more easily
human readable. Previously a Duration of one second would printed as
Duration { secs: 1, nanos: 0 } and will now be printed as 1s.From<&String> for Cow<str>, From<&Vec<T>> for Cow<[T]>,
From<Cow<CStr>> for CString, From<CString>, From<CStr>, From<&CString>
for Cow<CStr>, From<OsString>, From<OsStr>, From<&OsString> for
Cow<OsStr>, From<&PathBuf> for Cow<Path>, and From<Cow<Path>>
for PathBuf.Shl and Shr for Wrapping<u128>
and Wrapping<i128>.DirEntry::metadata now uses fstatat instead of lstat when
possible. This can provide up to a 40% speed increase.format!.Iterator::step_byPath::ancestorsSystemTime::UNIX_EPOCHalloc::GlobalAllocalloc::Layoutalloc::LayoutErralloc::Systemalloc::allocalloc::alloc_zeroedalloc::deallocalloc::reallocalloc::handle_alloc_errorbtree_map::Entry::or_defaultfmt::Alignmenthash_map::Entry::or_defaultiter::repeat_withnum::NonZeroUsizenum::NonZeroU128num::NonZeroU16num::NonZeroU32num::NonZeroU64num::NonZeroU8ops::RangeBoundsslice::SliceIndexslice::from_mutslice::from_ref{Any + Send + Sync}::downcast_mut{Any + Send + Sync}::downcast_ref{Any + Send + Sync}::issrc directory. The src directory in a crate should be
considered to be immutable.suggestion_applicability field in rustc’s json output is now
stable. This will allow dev tools to check whether a code suggestion
would apply to them.rustdoc would execute plugins in the /tmp/rustdoc/plugins directory when running, which enabled executing code as some other user on a given machine. This release fixes that vulnerability; you can read more about this on the blog. The associated CVE is CVE-2018-1000622.
Thank you to Red Hat for responsibly disclosing this vulnerability to us.
proc to
be used as an identifier.Trait syntax, and should make it clearer when being used in tandem with
impl Trait because it is equivalent to the following syntax:
&Trait == &dyn Trait, &mut Trait == &mut dyn Trait, and
Box<Trait> == Box<dyn Trait>.fn foo<#[lifetime_attr] 'a, #[type_attr] T: 'a>() {}#[must_use] attribute can now also be used on functions as well as
types. It provides a lint that by default warns users when the
value returned by a function has not been used.arch::x86 & arch::x86_64 modules which contain
SIMD intrinsics, a new macro called is_x86_feature_detected!, the
#[target_feature(enable="")] attribute, and adding target_feature = "" to
the cfg attribute.[u8], f32, and f64 previously only available in
std are now available in core.Rhs type parameter on ops::{Shl, ShlAssign, Shr} now defaults
to Self.std::str::replace now has the #[must_use] attribute to clarify
that the operation isn’t done in place.Clone::clone, Iterator::collect, and ToOwned::to_owned now have
the #[must_use] attribute to warn about unused potentially
expensive allocations.DoubleEndedIterator::rfindDoubleEndedIterator::rfoldDoubleEndedIterator::try_rfoldDuration::from_microsDuration::from_nanosDuration::subsec_microsDuration::subsec_millisHashMap::remove_entryIterator::try_foldIterator::try_for_eachNonNull::castOption::filterString::replace_rangeTake::set_limithint::unreachable_uncheckedos::unix::process::parent_idptr::swap_nonoverlappingslice::rsplit_mutslice::rsplitslice::swap_with_slicecargo-metadata now includes authors, categories, keywords,
readme, and repository fields.cargo-metadata now includes a package’s metadata table.--target-dir optional argument. This allows you to specify
a different directory than target for placing compilation artifacts.[[bin]], and have other binaries in locations
where cargo would infer a binary, Cargo will produce a warning. You can
disable this feature ahead of time by setting any of the following to false:
autobins, autobenches, autoexamples, autotests.CARGO_CACHE_RUSTC_INFO=0 in your environment.doc.rust-lang.org are now searchable.CharExt or StrExt method directly on core will no longer
work. e.g. ::core::prelude::v1::StrExt::is_empty("") will not
compile, "".is_empty() will still compile.Debug output on atomic::{AtomicBool, AtomicIsize, AtomicPtr, AtomicUsize}
will only print the inner type. E.g.
print!("{:?}", AtomicBool::new(true)) will print true,
not AtomicBool(true).repr(align(N)) is now 2²⁹. Previously you
could enter higher numbers but they were not supported by LLVM. Up to 512MB
alignment should cover all use cases..description() method on the std::error::Error trait
has been soft-deprecated. It is no longer required to implement it.fn main() -> impl Trait no longer works for non-Termination
trait.
This reverts an accidental stabilization.NaN > NaN no longer returns true in const-fn contexts.impl Trait in method arguments.Copy and/or Clone if all captured variables
implement either or both traits.for x in 0..=10 is now stable.'_ lifetime is now stable. The underscore lifetime can be used anywhere a
lifetime can be elided.impl Trait is now stable allowing you to have abstract types in returns
or in function parameters. E.g. fn foo() -> impl Iterator<Item=u8> or
fn open(path: impl AsRef<Path>).u128 and i128 are now stable.main can now return Result<(), E: Debug> in addition to ().wasm32-unknown-unknown.--remap-path-prefix option to rustc. Allowing you
to remap path prefixes outputted by the compiler.powerpc-unknown-netbsd target.From<u16> for usize & From<{u8, i16}> for isize.assert!(format!("{:02x?}", b"Foo\0") == "[46, 6f, 6f, 00]")Default, Hash for cmp::Reverse.str::repeat being 8x faster in large cases.ascii::escape_default is now available in libcore.Copy, Clone for cmp::ReverseClone for char::{ToLowercase, ToUppercase}.*const T::add*const T::copy_to_nonoverlapping*const T::copy_to*const T::read_unaligned*const T::read_volatile*const T::read*const T::sub*const T::wrapping_add*const T::wrapping_sub*mut T::add*mut T::copy_to_nonoverlapping*mut T::copy_to*mut T::read_unaligned*mut T::read_volatile*mut T::read*mut T::replace*mut T::sub*mut T::swap*mut T::wrapping_add*mut T::wrapping_sub*mut T::write_bytes*mut T::write_unaligned*mut T::write_volatile*mut T::writeBox::leakFromUtf8Error::as_bytesLocalKey::try_withOption::clonedbtree_map::Entry::and_modifyfs::read_to_stringfs::readfs::writehash_map::Entry::and_modifyiter::FusedIteratorops::RangeInclusiveops::RangeToInclusiveprocess::idslice::rotate_leftslice::rotate_rightString::retain-v is
passed with --listFn trait as dyn no longer works. E.g. the following
syntax is now invalid.
'static.
e.g.
AsciiExt trait in favor of inherent methods.".e0" will now no longer parse as 0.0 and will instead cause
an error.#[repr(align(x))] attribute is now stable. RFC 1358use std::{fs::File, io::Read, path::{Path, PathBuf}};| at the start of a match arm. e.g.enum Foo { A, B, C }
fn main() {
let x = Foo::A;
match x {
| Foo::A
| Foo::B => println!("AB"),
| Foo::C => println!("C"),
}
}process::Command on Unix.ParseCharError.UnsafeCell::into_inner is now safe.Float::{from_bits, to_bits} is now available in libcore.AsRef<Path> for ComponentWrite for Cursor<&mut Vec<u8>>Duration to libcore.The following functions can now be used in a constant expression.
eg. static MINUTE: Duration = Duration::from_secs(60);
cargo new no longer removes rust or rs prefixes/suffixes.cargo new now defaults to creating a binary crate, instead of a
library crate.net::lookup_host.rustdoc has switched to pulldown as the default markdown renderer.#[simd].sysv64 ffi is now available.
eg. extern "sysv64" fn foo () {}codegen-units=1.armv4t-unknown-linux-gnueabi target.aarch64-unknown-openbsd supportstr::find::<char> now uses memchr. This should lead to a 10x
improvement in performance in the majority of cases.OsStr’s Debug implementation is now lossless and consistent
with Windows.time::{SystemTime, Instant} now implement Hash.From<bool> for AtomicBoolFrom<{CString, &CStr}> for {Arc<CStr>, Rc<CStr>}From<{OsString, &OsStr}> for {Arc<OsStr>, Rc<OsStr>}From<{PathBuf, &Path}> for {Arc<Path>, Rc<Path>}AsciiExt methods onto charT: Sized requirement on ptr::is_null()From<RecvError> for {TryRecvError, RecvTimeoutError}f32::{min, max} to generate more efficient x86 assembly[u8]::contains now uses memchr which provides a 3x speed improvementThe following functions can now be used in a constant expression.
eg. let buffer: [u8; size_of::<usize>()];, static COUNTER: AtomicUsize = AtomicUsize::new(1);
AtomicBool::newAtomicUsize::newAtomicIsize::newAtomicPtr::newCell::new{integer}::min_value{integer}::max_valuemem::size_ofmem::align_ofptr::nullptr::null_mutRefCell::newUnsafeCell::newworkspace.default-members config that
overrides implied --all in virtual workspaces.Cargo.toml and .cargo/config to disable on a
per-project or global basis respectively.Debug impl now always prints a decimal point.Ipv6Addr now rejects superfluous ::’s in IPv6 addresses This is
in accordance with IETF RFC 4291 §2.2.Formatter::flags method is now deprecated. The sign_plus,
sign_minus, alternate, and sign_aware_zero_pad should be used instead.column!() macro is one-based instead of zero-basedfmt::Arguments can no longer be shared across threads#[repr(packed)] struct fields is now unsafeauto traits are now permitted in trait objects.TrapUnreachable in LLVM which should mitigate the impact of
undefined behavior.assert_eq/ne macroFrom<*mut T> for AtomicPtr<T>From<usize/isize> for AtomicUsize/AtomicIsize.T: Sync requirement for RwLock<T>: SendT: Sized requirement for {<*const T>, <*mut T>}::as_ref
and <*mut T>::as_mutThread::{park, unpark} implementationSliceExt::binary_search performance.FromIterator<()> for ()AsciiExt trait methods to primitive types. Use of AsciiExt
is now deprecated.cargo uninstall foo bar uninstalls foo and bar.cargo checkcargo install --versionchar::escape_debug now uses Unicode 10 over 9.non_snake_case lint now allows extern no-mangle functionsT op= &T now works for numeric types. eg. let mut x = 2; x += &8;Drop are now allowed in const and static typesle32-unknown-naclarmv5te_unknown_linux_gnueabiBox<Error> now impls From<Cow<str>>std::mem::Discriminant is now guaranteed to be Send + Syncfs::copy now returns the length of the main stream on NTFS.Instant += Duration.Hasher for {&mut Hasher, Box<Hasher>}fmt::Debug for SplitWhitespace.Option<T> now impls Try This allows for using ? with Option types.examples
folder that have a main.rs file.[root] to [package] in Cargo.lock Packages with
the old format will continue to work and can be updated with cargo update.libbacktrace is now available on Apple platforms.compile_fail attribute for code fences in doc-comments.
This now lets you specify that a given code example will fail to compile.4.0 from 2.3T op= &T for numeric types has broken some type
inference cases:: before < is now allowed in all contexts.
Example:
Clone for all arrays and tuples that
are T: CloneStdin, Stdout, and Stderr now implement AsRawFd.Rc and Arc now implement From<&[T]> where T: Clone, From<str>,
From<String>, From<Box<T>> where T: ?Sized, and From<Vec<T>>.cargo install with multiple package names--all[patch] section to Cargo.toml to handle
prepublication dependencies RFC 1969include & exclude fields in Cargo.toml now accept gitignore
like patterns--all-targets optionrustup component add rls-previewstd::os documentation for Unix, Linux, and Windows now appears on doc.rust-lang.org
Previously only showed std::os::unix.CodeMap struct which
required the unstable library libsyntax to correctly use.unused_results lint no longer ignores booleanswasm32-experimental-emscripten target.msp430-none-elf target.{HashMap,BTreeMap}::{Keys,Values}.PartialEq, Eq, PartialOrd, Ord, Debug, Hash for unsized
tuples.fmt::{Display, Debug} for Ref, RefMut, MutexGuard,
RwLockReadGuard, RwLockWriteGuardClone for DefaultHasher.Sync for SyncSender.FromStr for char{f32, f64}::{is_sign_negative, is_sign_positive} handles
NaN.unimplemented!() macro.
ie. unimplemented!("Waiting for 1.21 to be stable")pub(restricted) is now supported in the thread_local! macro.{f32, f64}::{min, max} in Rust instead of using CMath.ops::{Range, RangeFrom} is now done in O(1) time#[repr(align(N))] attribute max number is now 2^31 - 1. This was
previously 2^15.{OsStr, Path}::Display now avoids allocations where possibleCStr::into_c_stringCString::as_c_strCString::into_boxed_c_strChain::get_mutChain::get_refChain::into_innerOption::get_or_insert_withOption::get_or_insertOsStr::into_os_stringOsString::into_boxed_os_strTake::get_mutTake::get_refUtf8Error::error_lenchar::EscapeDebugchar::escape_debugcompile_error!f32::from_bitsf32::to_bitsf64::from_bitsf64::to_bitsmem::ManuallyDropslice::sort_unstable_by_keyslice::sort_unstable_byslice::sort_unstablestr::from_boxed_utf8_uncheckedstr::as_bytes_mutstr::as_bytes_mutstr::from_utf8_mutstr::from_utf8_unchecked_mutstr::get_mutstr::get_unchecked_mutstr::get_uncheckedstr::getstr::into_boxed_bytes~/.cargo/config to
~/.cargo/credentials.main.rs binaries that are in sub-directories of
src/bin. ie. Having src/bin/server/main.rs and
src/bin/client/main.rs generates target/debug/server and target/debug/clientcargo install using --vers.--no-fail-fast flag to cargo to run all benchmarks regardless of
failure.'static in their return types will now not be as usable as
if they were using lifetime parameters instead.{f32, f64}::is_sign_{negative, positive} now
takes the sign of NaN into account where previously didn’t.struct Point(u32, u32); let x = Point { 0: 7, 1: 0 };.loop can now return a value with break. RFC 1624
For example: let x = loop { break 7; };unions are now available. RFC 1444 They can only
contain Copy types and cannot have a Drop implementation.
Example: union Foo { bar: u8, baz: usize }fns, RFC 1558
Example: let foo: fn(u8) -> u8 = |v: u8| { v };arm-linux-androideabi to correspond to the armeabi
official ABI. If you wish to continue targeting the armeabi-v7a ABI
you should use --target armv7-linux-androideabi.aborting due to previous error(s) instead of
aborting due to N previous errors This was previously inaccurate and
would only count certain kinds of errors.target-feature=+crt-static option RFC 1721 Which allows
libraries with C Run-time Libraries(CRT) to be statically linked.String now implements FromIterator<Cow<'a, str>> and
Extend<Cow<'a, str>>Vec now implements From<&mut [T]>Box<[u8]> now implements From<Box<str>>SplitWhitespace now implements Clone[u8]::reverse is now 5x faster and [u16]::reverse is now
1.5x fastereprint! and eprintln! macros added to prelude. Same as the print!
macros, but for printing to stderr.println!("cargo:rustc-env=FOO=bar");--all flag to the cargo bench subcommand to run benchmarks of all
the members in a given workspace.libssh2-sys to 0.2.6--exclude option for excluding certain packages when using the
--all option--features option now accepts multiple comma or space
delimited values.rust-windbg.cmd for loading rust .natvis files in the
Windows Debugger.# in rust documentation By adding
additional #’s ie. ## is now #MutexGuard<T> may only be Sync if T is Sync.-Z flags are now no longer allowed to be used on the stable
compiler. This has been a warning for a year previous to this.-Z flag change, the cargo-check plugin no
longer works. Users should migrate to the built-in check
command, which has been available since 1.16.._ is now a hard error.
Example: 42._ .extern crate outside of its module is now a
hard error. This was previously a warning.use ::self::foo; is now a hard error. self paths are always
relative while the :: prefix makes a path absolute, but was ignored and the
path was relative regardless.PartialEq & Eq used
match patterns is now a hard error This was previously a warning.'_ are no longer allowed. This was previously
a warning.#s are
now visibleVCINSTALLDIR is set incorrectly, rustc will try
to use it to find the linker, and the build will fail where it did
not previouslypub can now accept a module path to
make the item visible to just that module tree. Also accepts the keyword
crate to make something public to the whole crate but not users of the
library. Example: pub(crate) mod utils;. RFC 1422.#![windows_subsystem] attribute conservative exposure of the
/SUBSYSTEM linker flag on Windows platforms. RFC 1665.ty in macros can accept
types like Write + Send, trailing + are now supported in trait objects,
and better error reporting for trait objects starting with ?Sized.repr attribute or with
#[repr(Rust)] are reordered to minimize padding and produce a smaller
representation in some cases.--emit mirVec::from_iter being passed vec::IntoIter if the
iterator hasn’t been advanced the original Vec is reassembled with no actual
iteration or reallocation.AtomicBool::fetch_nandChild::try_waitHashMap::retainHashSet::retainPeekMut::popTcpStream::peekUdpSocket::peekUdpSocket::peek_fromcargo new --vcs pijul--bins and --tests flags now you can build all programs
of a certain type, for example cargo build --bins will build all
binaries.--enable-commonmark flag# at the start of filesChanges to how the 0 flag works in format! Padding zeroes are now
always placed after the sign if it exists and before the digits. With the #
flag the zeroes are placed after the prefix and before the digits.
Due to the struct field optimisation, using transmute on structs
that have no repr attribute or #[repr(Rust)] will no longer work. This has
always been undefined behavior, but is now more likely to break in practice.
The refactor of trait object type parsing fixed a bug where + was
receiving the wrong priority parsing things like &for<'a> Tr<'a> + Send as
&(for<'a> Tr<'a> + Send) instead of (&for<'a> Tr<'a>) + Send
rustc main.rs -o out --emit=asm,llvm-ir Now will output
out.asm and out.ll instead of only one of the filetypes.
calling a function that returns Self will no longer work when
the size of Self cannot be statically determined.
rustc now builds with a “pthreads” flavour of MinGW for Windows GNU this has caused a few regressions namely:
'static. RFC 1623Self may be included in the where clause of impls. RFC 1647T and U when T: Unsize<U>. For example,
coercing &mut [&'a X; N] to &mut [&'b X] requires 'a be equal to
'b. Soundness fix.[], automatically coerce--emit dep-info-C relocation-model more correctly determine whether the linker
creates a position-independent executable-C overflow-checks to directly control whether integer overflow
panicsSelf to appear in impl where clauses.usepanic=abort&str + &strArc::into_rawArc::from_rawArc::ptr_eqRc::into_rawRc::from_rawRc::ptr_eqOrdering::thenOrdering::then_withBTreeMap::rangeBTreeMap::range_mutcollections::Boundprocess::abortptr::read_unalignedptr::write_unalignedResult::expect_errCell::swapCell::replaceCell::into_innerCell::takeBTreeMap and BTreeSet can iterate over rangesCell can store non-Copy types. RFC 1651String implements FromIterator<&char>Box implements a number of new conversions:
From<Box<str>> for String,
From<Box<[T]>> for Vec<T>,
From<Box<CStr>> for CString,
From<Box<OsStr>> for OsString,
From<Box<Path>> for PathBuf,
Into<Box<str>> for String,
Into<Box<[T]>> for Vec<T>,
Into<Box<CStr>> for CString,
Into<Box<OsStr>> for OsString,
Into<Box<Path>> for PathBuf,
Default for Box<str>,
Default for Box<CStr>,
Default for Box<OsStr>,
From<&CStr> for Box<CStr>,
From<&OsStr> for Box<OsStr>,
From<&Path> for Box<Path>ffi::FromBytesWithNulError implements Error and DisplayPartialOrd<A> for [A] where A: Ordslice::sortToString trait specialization for Cow<'a, str> and StringBox<[T]> implements From<&[T]> where T: Copy,
Box<str> implements From<&str>IpAddr implements From for various arrays. SocketAddr implements
From<(I, u16)> where I: Into<IpAddr>format! estimates the needed capacity before writing a stringPathBuf implements DefaultPartialEq<[A]> for VecDeque<A>HashMap resizes adaptively to guard against DOS attacks
and poor hash functions.cargo check --allcargo run --packagerequired_featuresbuild.rs is a build scriptworkspace_root link in containing memberrustbooki128rustc is linked statically on Windows MSVC targets, allowing it to
run without installing the MSVC runtime.rustdoc --test includes file names in test namesstd for sparc64-unknown-linux-gnu,
aarch64-unknown-linux-fuchsia, and x86_64-unknown-linux-fuchsia.aarch64-unknown-freebsdi686-unknown-netbsdTypeId implements PartialOrd and Ord--test-threads=0 produces an errorrustup installs documentation by defaultT and U when T: Unsize<U>, e.g. coercing
&mut [&'a X; N] to &mut [&'b X] requires 'a be equal to 'b. Soundness
fix.format! and Display::to_string panic if an underlying formatting
implementation returns an error. Previously the error was silently
ignored. It is incorrect for write_fmt to return an error when writing
to a string.proc_macro_deriveshr_lifetime_in_assoc_type future-compatibility lint has been in effect since
April of 2016.dead_code lint now accounts for type aliases.self in an import listSelf may appear in impl headersSelf may appear in struct expressionsrustc now supports --emit=metadata, which causes rustc to emit
a .rmeta file containing only crate metadata. This can be
used by tools like the Rust Language Service to perform
metadata-only builds.transmute::<T, U> where T requires a bigger alignment than
Urustc no longer attempts to provide “consider using an explicit
lifetime” suggestions. They were inaccurate.VecDeque::truncateVecDeque::resizeString::insert_strDuration::checked_addDuration::checked_subDuration::checked_divDuration::checked_mulstr::replacenstr::repeatSocketAddr::is_ipv4SocketAddr::is_ipv6IpAddr::is_ipv4IpAddr::is_ipv6Vec::dedup_byVec::dedup_by_keyResult::unwrap_or_default<*const T>::wrapping_offset<*mut T>::wrapping_offsetCommandExt::creation_flagsFile::set_permissionsString::split_off[T]::binary_search and [T]::binary_search_by_key now take
their argument by Borrow parameterDebugIpAddr implements From<Ipv4Addr> and From<Ipv6Addr>Ipv6Addr implements From<[u16; 8]>Stdin.read() when reading from the console on
WindowsLineWriter&str slicing errorsTcpListener::set_only_v6 is deprecated. This
functionality cannot be achieved in std currently.writeln!, like println!, now accepts a form with no string
or formatting arguments, to just print a newlineiter::Sum and iter::Product for Resultstd_unicode::tableschar::EscapeDebug, EscapeDefault, EscapeUnicode,
CaseMappingIter, ToLowercase, ToUppercase, implement
DisplayDuration implements SumString implements ToSocketAddrscargo check command does a type check of a project without
building itdebug, in addition
to true and false. These are passed to rustc as the value to
-C debuginfocargo --version --verbosebuild --alldoc --allrustdoc has a --sysroot argument that, like rustc, specifies
the path to the Rust implementationarmv7-linux-androideabi target no longer enables NEON
extensions, per Google’s ABI guidedead_code lint now accounts for type aliases.Stdin.read() when reading from the console on
Windowsself in an import list#[derive], aka “macros 1.1”, are
stable. This allows popular code-generating crates like Serde and Diesel to
work ergonomically. RFC 1681.legacy_imports lint since 1.14, with no known regressions.macro_rules, path fragments can now be parsed as type parameter
bounds?Sized can be used in where clauses#![type_size_limit] crate attribute, similarly to
the #![recursion_limit] attribute--test flag works with procedural macro cratesextern "aapcs" fn ABI-C no-stack-check flag is deprecated. It does nothing.format! expander recognizes incorrect printf and shell-style
formatting directives and suggests the correct format.mk_ty calls in Ty::super_fold_withmk_ty calls in Ty::super_fold_withUnificationTable::probescope_auxiliary to cut RSS by 10%HirVec<P<T>> to HirVec<T> in hir::Exprstd::iter::Iterator::min_bystd::iter::Iterator::max_bystd::os::*::fs::FileExtstd::sync::atomic::Atomic*::get_mutstd::sync::atomic::Atomic*::into_innerstd::vec::IntoIter::as_slicestd::vec::IntoIter::as_mut_slicestd::sync::mpsc::Receiver::try_iterstd::os::unix::process::CommandExt::before_execstd::rc::Rc::strong_countstd::rc::Rc::weak_countstd::sync::Arc::strong_countstd::sync::Arc::weak_countstd::char::encode_utf8std::char::encode_utf16std::cell::Ref::clonestd::io::Take::into_innerIterator::nth no longer has a Sized boundExtend<&T> is specialized for Vec where T: Copy to improve
performance.chars().count() is much faster and so are chars().last()
and char_indices().last()std::env::argsfmt::DebugDefault for Durationmpsc::RecvTimeoutError implements ErrorOUT_DIR
environment variable at build time via env!("OUT_DIR"). They
should instead check the variable at runtime with std::env. That the value
was set at build time was a bug, and incorrect when cross-compiling. This
change is known to cause breakage.--all flag to cargo testcargo install --vers to take a semver versionbuild.rustflags config keybuild.rs in the same directory as Cargo.toml is a build script--message-format JSON when rustc emits non-JSON warnings--test) now support a --list argument
that lists the tests it contains--exact argument that makes the test filter
match exactly, instead of matching only a substring of the test name--playground-url flag#[should_panic] errors--disable-rustbuild to the
configure script, but they will be deleted soon. Note that the new build
system uses a different on-disk layout that will likely affect any scripts
building Rust.legacy_imports lint since 1.14, with no known regressions.OUT_DIR
environment variable at build time via env!("OUT_DIR"). They
should instead check the variable at runtime with std::env. That the value
was set at build time was a bug, and incorrect when cross-compiling. This
change is known to cause breakage.hr_lifetime_in_assoc_type lint has been a warning since
1.10 and is now an error by default. It will become a hard error in the near
future.legacy_directory_ownership
lint, which is a warning in this release, and will become a hard error in the
future.Peekable peeks a None it will return that None without re-querying
the underlying iterator.. matches multiple tuple fields in enum variants, structs
and tuples. RFC 1492.fn items can be coerced to unsafe fn pointersuse * and use ::* both glob-import from the crate rootVec<Box<Fn()>> without explicit
dereferencingstatic mut names are linted like other
statics and consts[u8; m!()])x”--version --verboseExpr_::ExprInlineAsmIchHasherSmallVector in CombineFields::instantiateArrayVec and AccumulateVec to reduce heap allocations
during interning of sliceswrite_metadataCrateConfig clonesSubsts::super_fold_withObligationForest’s NodeState handlingplug_leaksprintln!(), with no arguments, prints newline.
Previously, an empty string was required to achieve the same.Wrapping impls standard binary and unary operators, as well as
the Sum and Product iteratorsFrom<Cow<str>> for String and From<Cow<[T]>> for Vec<T>fold performance for chain, cloned, map, and
VecDeque iteratorsSipHasher performance on small values.zip() specialization to .map() and .cloned()ReadDir implements DebugRefUnwindSafe for atomic typesVec::extend to Vec::extend_from_sliceDecoder::read_strio::Error implements From<io::ErrorKind>Debug for raw pointers to unsized dataHashMap random seedsHashMap is more cache-friendly, for
significant improvements in some operationsHashMap uses less memory on 32-bit architecturesAdd<{str, Cow<str>}> for Cow<str>CARGO_HOMEreplace sections from lock filespanic configuration for test/bench profilesrustup target add. The new target triples are:
mips-unknown-linux-gnumipsel-unknown-linux-gnumips64-unknown-linux-gnuabi64mips64el-unknown-linux-gnuabi64 powerpc-unknown-linux-gnupowerpc64-unknown-linux-gnupowerpc64le-unknown-linux-gnus390x-unknown-linux-gnu rustup target add:
arm-unknown-linux-musleabiarm-unknown-linux-musleabihfarmv7-unknown-linux-musleabihfwasm32-unknown-emscripten target. This target is known to have major
defects. Please test, report, and fix.rustup component add rust-docs to install.#[derive(PartialEq, Eq)]”'_ were erroneously allowed”Ordering enum may not be matched exhaustively#[no_link] breaks some obscure cases$crate macro variable is accepted in fewer locations? operator. ? is a simple way to propagate
errors, like the try! macro, described in RFC 0243.#[derive] for empty tuple structs/variants-C link-arg argumentuse self when such an import resolvesassert_ne! and debug_assert_ne!vec_deque::Drain, hash_map::Drain, and hash_set::Drain
covariantAsRef<[T]> for std::slice::IterDebug for std::vec::IntoIterCString: avoid excessive growth just to 0-terminateCoerceUnsized for {Cell, RefCell, UnsafeCell}Debug for std::path::{Components,Iter}charDebug for DirEntrygetaddrinfo returns EAI_SYSTEM retrieve actual error from
errnoSipHasher is deprecated. Use DefaultHasher.std::io::ErrorKindVec::extend_from_slice,
extend_with_elementcargo packagecargo installCommandExt::exec for cargo run on Unix--sysroot argument! from macro URLs and titlesSipHasher is deprecated. Use DefaultHasher.#[derive] for empty tuple structs/variants.
Part of RFC 1506.ethcore crate fails with LLVM errorrustc translates code to LLVM IR via its own “middle” IR (MIR).
This translation pass is far simpler than the previous AST->LLVM pass, and
creates opportunities to perform new optimizations directly on the MIR. It
was previously described on the Rust blog.rustc presents a new, more readable error format, along with
machine-readable JSON error output for use by IDEs.
Most common editors supporting Rust have been updated to work with it. It was
previously described on the Rust blog.rustc translates code to LLVM IR via its own “middle” IR (MIR).
This translation pass is far simpler than the previous AST->LLVM pass, and
creates opportunities to perform new optimizations directly on the MIR. It
was previously described on the Rust blog.--print target-listTypeId is correct in some cases where it was previously
producing inconsistent resultsmips-unknown-linux-gnu target uses hardware floating point by defaultrustc arguments, --print target-cpus, --print target-features,
--print relocation-models, and --print code-models print the available
options to the -C target-cpu, -C target-feature, -C relocation-model and
-C code-model code generation argumentsrustc supports three new MUSL targets on ARM: arm-unknown-linux-musleabi,
arm-unknown-linux-musleabihf, and armv7-unknown-linux-musleabihf.
These targets produce statically-linked binaries. There are no binary release
builds yet though.rustc presents a new, more readable error format, along with
machine-readable JSON error output for use by IDEs.
Most common editors supporting Rust have been updated to work with it. It was
previously described on the Rust blog.{integer} or
{float} instead of _rustc emits a clearer error when inner attributes follow a doc commentmacro_rules! invocations can be made within macro_rules! invocationsmacro_rules! meta-variables are hygienicmacro_rules! tt matchers can be reparsed correctly, making them much more
usefulmacro_rules! stmt matchers correctly consume the entire contents when
inside non-braces invocationsmacro_rules! invocationscfg_attr works on path attributesCell::as_ptrRefCell::as_ptrIpAddr::is_unspecifiedIpAddr::is_loopbackIpAddr::is_multicastIpv4Addr::is_unspecifiedIpv6Addr::octetsLinkedList::containsVecDeque::containsExitStatusExt::from_raw.
Both on Unix and Windows.Receiver::recv_timeoutRecvTimeoutErrorBinaryHeap::peek_mutPeekMutiter::Productiter::SumOccupiedEntry::remove_entryVacantEntry::into_keyformat! macro and friends now allow a single argument to be formatted
in multiple styles[T]::binary_search_by and
[T]::binary_search_by_key have been adjusted to be more flexibleOption implements From for its contained typeCell, RefCell and UnsafeCell implement From for their contained typeRwLock panics if the reader count overflowsvec_deque::Drain, hash_map::Drain and hash_set::Drain are covariantvec::Drain and binary_heap::Drain are covariantCow<str> implements FromIterator for char, &str and StringSOCK_CLOEXEChash_map::Entry, hash_map::VacantEntry and hash_map::OccupiedEntry
implement Debugbtree_map::Entry, btree_map::VacantEntry and btree_map::OccupiedEntry
implement DebugString implements AddAssignextern fn pointers implement the Clone, PartialEq, Eq,
PartialOrd, Ord, Hash, fmt::Pointer, and fmt::Debug traitsFileType implements DebugMutex and RwLock are unwind-safempsc::sync_channel Receivers return any available message before
reporting a disconnectenv iterators implement DoubleEndedIteratoropt-level="s" / opt-level="z" in profile overridescargo doc --open --target work as expected--panic=abort with plugins-C metadata to the compiler--lib flag to cargo newhttp.cainfo for custom certs--features--jobs flag to cargo package--dry-run to cargo publishRUSTDOCFLAGSpanic::catch_unwind is more optimizedpanic::catch_unwind no longer accesses thread-local storage on entry--test-threads argument to specify the number
of threads used to run tests, and which acts the same as the
RUST_TEST_THREADS environment variablerust-lldb warns about unsupported versions of LLDBrustup component add rust-src.
The resulting source code can be used by tools and IDES, located in the
sysroot under lib/rustlib/src.OsStrs, unpaired surrogate codepoints are escaped
with the lowercase format instead of the uppercaseDebug impl for strings no longer escapes all non-ASCII characterscfg_attr attributes#[macro_use] works properly when it is itself expanded from a macroBinaryHeap::appendBTreeMap::appendBTreeMap::split_offBTreeSet::appendBTreeSet::split_offf32::to_degrees
(in libcore - previously stabilized in libstd)f32::to_radians
(in libcore - previously stabilized in libstd)f64::to_degrees
(in libcore - previously stabilized in libstd)f64::to_radians
(in libcore - previously stabilized in libstd)Iterator::sumIterator::productCell::get_mutRefCell::get_mutthread_local! macro supports multiple definitions in a single
invocation, and can apply attributesCow implements DefaultWrapping implements binary, octal, lower-hex and upper-hex
Display formattingHashlookup_host ignores unknown address typesassert_eq! accepts a custom error message, like assert! doesharness = false on [lib] sectionslinks contains a ‘.’-vv prints warnings for all crates.package.metadata keys.
This provides room for expansion by arbitrary tools.cargo doc --open on WindowsHashMap hasher is SipHash 1-3 instead of SipHash 2-4
This hasher is faster, but is believed to provide sufficient
protection from collision attacks.Ipv4Addr is 10x fasterconsts and statics may not have unsized typesmacro_rules!
in order to ensure syntax forward-compatibility have been enabled
This was an amendment to RFC 550,
and has been a warning since 1.10.cfg attribute process has been refactored to fix various bugs.
This causes breakage in some corner cases.Copy types are required to have a trivial implementation of Clone.
RFC 1521.#[repr(..)] attribute.#[derive(RustcEncodable)] in the presence of other encode methods.panic! can be converted to a runtime abort with the
-C panic=abort flag.
RFC 1513.os::windows::fs::OpenOptionsExt::access_modeos::windows::fs::OpenOptionsExt::share_modeos::windows::fs::OpenOptionsExt::custom_flagsos::windows::fs::OpenOptionsExt::attributesos::windows::fs::OpenOptionsExt::security_qos_flagsos::unix::fs::OpenOptionsExt::custom_flagssync::Weak::newDefault for sync::Weakpanic::set_hookpanic::take_hookpanic::PanicInfopanic::PanicInfo::payloadpanic::PanicInfo::locationpanic::Locationpanic::Location::filepanic::Location::lineffi::CStr::from_bytes_with_nulffi::CStr::from_bytes_with_nul_uncheckedffi::FromBytesWithNulErrorfs::Metadata::modifiedfs::Metadata::accessedfs::Metadata::createdsync::atomic::Atomic{Usize,Isize,Bool,Ptr}::compare_exchangesync::atomic::Atomic{Usize,Isize,Bool,Ptr}::compare_exchange_weakcollections::{btree,hash}_map::{Occupied,Vacant,}Entry::keyos::unix::net::{UnixStream, UnixListener, UnixDatagram, SocketAddr}SocketAddr::is_unnamedSocketAddr::as_pathnameUnixStream::connectUnixStream::pairUnixStream::try_cloneUnixStream::local_addrUnixStream::peer_addrUnixStream::set_read_timeoutUnixStream::set_write_timeoutUnixStream::read_timeoutUnixStream::write_timeoutUnixStream::set_nonblockingUnixStream::take_errorUnixStream::shutdownUnixStreamUnixListener::bindUnixListener::acceptUnixListener::try_cloneUnixListener::local_addrUnixListener::set_nonblockingUnixListener::take_errorUnixListener::incomingUnixListenerUnixDatagram::bindUnixDatagram::unboundUnixDatagram::pairUnixDatagram::connectUnixDatagram::try_cloneUnixDatagram::local_addrUnixDatagram::peer_addrUnixDatagram::recv_fromUnixDatagram::recvUnixDatagram::send_toUnixDatagram::sendUnixDatagram::set_read_timeoutUnixDatagram::set_write_timeoutUnixDatagram::read_timeoutUnixDatagram::write_timeoutUnixDatagram::set_nonblockingUnixDatagram::take_errorUnixDatagram::shutdownUnixDatagram{BTree,Hash}Map::values_mut<[_]>::binary_search_by_keyabs_sub method of floats is deprecated.
The semantics of this minor method are subtle and probably not what
most people want.HashMaps can’t be initialized with getrandom they
will fall back to /dev/urandom temporarily to avoid blocking
during early boot.Clone for binary_heap::IntoIter.Display and Hash for std::num::Wrapping.Default implementation for &CStr, CString.From<Vec<T>> and Into<Vec<T>> for VecDeque<T>.Default for UnsafeCell, fmt::Error, Condvar,
Mutex, RwLock.profile.*.panic option.
This controls the runtime behavior of the panic! macro
and can be either “unwind” (the default), or “abort”.
RFC 1513.-p arguments.CARGO_MANIFEST_LINKS environment
variable that corresponds to the links field of the manifest.CARGO_HOME on Windows.net.retry value in .cargo/config.--force flag to cargo install.flock on NFS mounts.cargo install artifacts in temporary directories.
Makes it possible to install multiple crates in parallel.cargo test --doc.cargo --explain.-q is passed.cargo doc --lib and --bin.HashMaps by caching the random keys used
to initialize the hash state.find implementation for Chain iterators is 2x faster.#[derive(Copy, Clone)] to avoid bloat.fn type.&mut self to &mut mut self.std no longer prints backtraces on platforms where the running
module must be loaded with env::current_exe, which can’t be relied
on.rust-gdb and rust-lldb scripts are distributed on all
Unix platforms.libc::abort instead of
generating an illegal instruction.AtomicBool is now bool-sized, not word-sized.target_env for Linux ARM targets is just gnu, not
gnueabihf, gnueabi, etc.Duration::new.String::truncate to panic less.:block to the follow set for :ty and :path.
Affects how macros are parsed.#[deprecated] attribute when applied to an API will generate
warnings when used. The warnings may be suppressed with
#[allow(deprecated)]. RFC 1270.fn item types are zero sized, and each fn names a unique
type. This will break code that transmutes fns, so calling
transmute on a fn type will generate a warning for a few cycles,
then will be converted to an error.PATTERN_WHITE_SPACE category to be whitespace.std::panicstd::panic::catch_unwind (renamed from recover)std::panic::resume_unwind (renamed from propagate)std::panic::AssertUnwindSafe (renamed from AssertRecoverSafe)std::panic::UnwindSafe (renamed from RecoverSafe)str::is_char_boundary<*const T>::as_ref<*mut T>::as_ref<*mut T>::as_mutAsciiExt::make_ascii_uppercaseAsciiExt::make_ascii_lowercasechar::decode_utf16char::DecodeUtf16char::DecodeUtf16Errorchar::DecodeUtf16Error::unpaired_surrogateBTreeSet::takeBTreeSet::replaceBTreeSet::getHashSet::takeHashSet::replaceHashSet::getOsString::with_capacityOsString::clearOsString::capacityOsString::reserveOsString::reserve_exactOsStr::is_emptyOsStr::lenstd::os::unix::threadRawPthreadJoinHandleExtJoinHandleExt::as_pthread_tJoinHandleExt::into_pthread_tHashSet::hasherHashMap::hasherCommandExt::execFile::try_cloneSocketAddr::set_ipSocketAddr::set_portSocketAddrV4::set_ipSocketAddrV4::set_portSocketAddrV6::set_ipSocketAddrV6::set_portSocketAddrV6::set_flowinfoSocketAddrV6::set_scope_idslice::copy_from_sliceptr::read_volatileptr::write_volatileOpenOptions::create_newTcpStream::set_nodelayTcpStream::nodelayTcpStream::set_ttlTcpStream::ttlTcpStream::set_only_v6TcpStream::only_v6TcpStream::take_errorTcpStream::set_nonblockingTcpListener::set_ttlTcpListener::ttlTcpListener::set_only_v6TcpListener::only_v6TcpListener::take_errorTcpListener::set_nonblockingUdpSocket::set_broadcastUdpSocket::broadcastUdpSocket::set_multicast_loop_v4UdpSocket::multicast_loop_v4UdpSocket::set_multicast_ttl_v4UdpSocket::multicast_ttl_v4UdpSocket::set_multicast_loop_v6UdpSocket::multicast_loop_v6UdpSocket::set_multicast_ttl_v6UdpSocket::multicast_ttl_v6UdpSocket::set_ttlUdpSocket::ttlUdpSocket::set_only_v6UdpSocket::only_v6UdpSocket::join_multicast_v4UdpSocket::join_multicast_v6UdpSocket::leave_multicast_v4UdpSocket::leave_multicast_v6UdpSocket::take_errorUdpSocket::connectUdpSocket::sendUdpSocket::recvUdpSocket::set_nonblockingstd::sync::Once is poisoned if its initialization function
fails.cell::Ref and cell::RefMut can contain unsized types.fmt::Debug.BufReader and BufWriter was
reduced to 8K, from 64K. This is in line with the buffer size
used by other languages.Instant, SystemTime and Duration implement += and -=.
Duration additionally implements *= and /=.Skip is a DoubleEndedIterator.From<[u8; 4]> is implemented for Ipv4Addr.Chain implements BufRead.HashMap, HashSet and iterators are covariant.CARGO_PKG_AUTHORS environment variable.RUSTFLAGS variable to rustc
on the commandline. rustc arguments can also be specified
in the build.rustflags configuration key.ToString is specialized for str, giving it the same performance
as to_owned.Command::output no longer creates extra
threads.#[derive(PartialEq)] and #[derive(PartialOrd)] emit less code
for C-like enums.--quiet flag to a test runner will produce
much-abbreviated output.mips-unknown-linux-musl, mipsel-unknown-linux-musl, and
i586-pc-windows-msvc targets.std::sync::Once is poisoned if its initialization function
fails.impl blocks.fn item types are zero sized, and each fn names a unique
type. This will break code that transmutes fns, so calling
transmute on a fn type will generate a warning for a few cycles,
then will be converted to an error.+= by implementing the AddAssign, SubAssign,
MulAssign, DivAssign, RemAssign, BitAndAssign,
BitOrAssign, BitXorAssign, ShlAssign, or ShrAssign
traits. RFC 953.struct Foo { }, in
addition to the non-braced form, struct Foo;. RFC 218.str::encode_utf16 (renamed from utf16_units)str::EncodeUtf16 (renamed from Utf16Units)Ref::mapRefMut::mapptr::drop_in_placetime::Instanttime::SystemTimeInstant::nowInstant::duration_since (renamed from duration_from_earlier)Instant::elapsedSystemTime::nowSystemTime::duration_since (renamed from duration_from_earlier)SystemTime::elapsedAdd/Sub impls for Time and SystemTimeSystemTimeErrorSystemTimeError::durationSystemTimeErrorUNIX_EPOCHAddAssign, SubAssign, MulAssign, DivAssign,
RemAssign, BitAndAssign, BitOrAssign,
BitXorAssign, ShlAssign, ShrAssign.write! and writeln! macros correctly emit errors if any of
their arguments can’t be formatted.raw modules, which contain a number of
redefined C types are deprecated, including os::raw::unix,
os::raw::macos, and os::raw::linux. These modules defined types
such as ino_t and dev_t. The inconsistency of these definitions
across platforms was making it difficult to implement std
correctly. Those that need these definitions should use the libc
crate. RFC 1415.MetadataExt traits, including
os::unix::fs::MetadataExt, which expose values such as inode
numbers no longer return platform-specific types, but
instead return widened integers. RFC 1415.btree_set::{IntoIter, Iter, Range} are covariant.sync::mpsc implement fmt::Debug.--print targets flag prints a list of supported targets.--print cfg flag prints the cfgs defined for the current
target.rustc can be built with an new Cargo-based build system, written
in Rust. It will eventually replace Rust’s Makefile-based
build system. To enable it configure with configure --rustbuild.match patterns now list up to 3 missing
variants while also indicating the total number of missing variants
if more than 3.armv7-unknown-linux-gnueabihf, powerpc-unknown-linux-gnu,
powerpc64-unknown-linux-gnu, powerpc64le-unknown-linux-gnu
x86_64-rumprun-netbsd. These can be installed with
tools such as multirust.cargo init creates a new Cargo project in the current
directory. It is otherwise like cargo new.-v and
--color. verbose and color, respectively, go in the
[term] section of .cargo/config.build.jobs key
can be set via CARGO_BUILD_JOBS. Environment variables take
precedence over config files.cfg syntax for
describing targets so that dependencies for multiple
targets can be specified together. RFC 1361.CARGO_TARGET_ROOT, RUSTC, and
RUSTDOC take precedence over the build.target-dir,
build.rustc, and build.rustdoc configuration values.build.target configuration value sets the target platform,
like --target.-Z flags have been considered unstable, and other flags that
were considered unstable additionally required passing -Z unstable-options to access. Unlike unstable language and library
features though, these options have been accessible on the stable
release channel. Going forward, new unstable flags will not be
available on the stable release channel, and old unstable flags
will warn about their usage. In the future, all unstable flags will
be unavailable on the stable release channel.match on empty enum variants using
the Variant(..) syntax. This has been a warning since 1.6.MetadataExt traits, including
os::unix::fs::MetadataExt, which expose values such as inode
numbers no longer return platform-specific types, but
instead return widened integers. RFC 1415.--cfg compiler flags are parsed strictly as identifiers.Command::spawn and its equivalents return an error if any of
its command-line arguments contain interior NULs.rustc emits .lib files for the staticlib library
type instead of .a files. Additionally, for the MSVC
toolchain, rustc emits import libraries named foo.dll.lib
instead of foo.lib.Path
Path::strip_prefix (renamed from relative_from)path::StripPrefixError (new error type returned from strip_prefix)Ipv4Addr
Ipv6Addr
Vec
String
<[T]>::clone_from_slice, which now requires the two slices to
be the same length<[T]>::sort_by_keyi32::checked_rem, i32::checked_neg, i32::checked_shl, i32::checked_shri32::saturating_muli32::overflowing_add, i32::overflowing_sub, i32::overflowing_mul, i32::overflowing_divi32::overflowing_rem, i32::overflowing_neg, i32::overflowing_shl, i32::overflowing_shru32::checked_rem, u32::checked_neg, u32::checked_shl, u32::checked_shlu32::saturating_mulu32::overflowing_add, u32::overflowing_sub, u32::overflowing_mul, u32::overflowing_divu32::overflowing_rem, u32::overflowing_neg, u32::overflowing_shl, u32::overflowing_shrffi::IntoStringErrorCString::into_stringCString::into_bytesCString::into_bytes_with_nulFrom<CString> for Vec<u8>IntoStringError
IntoStringError::into_cstringIntoStringError::utf8_errorError for IntoStringErrorStrings and strs
from bytes is faster.LineWriter (and thus io::stdout) was
improved by using memchr to search for newlines.f32::to_degrees and f32::to_radians are stable. The
f64 variants were stabilized previously.BTreeMap was rewritten to use less memory and improve the performance
of insertion and iteration, the latter by as much as 5x.BTreeSet and its iterators, Iter, IntoIter, and Range are
covariant over their contained type.LinkedList and its iterators, Iter and IntoIter are covariant
over their contained type.str::replace now accepts a Pattern, like other string
searching methods.Any is implemented for unsized types.Hash is implemented for Duration.--test, rustdoc will pass --cfg
arguments to the compiler.rustc when installed in
unusual configurations without configuring the dynamic linker search
path explicitly.rustc passes --enable-new-dtags to GNU ld. This makes
any RPATH entries (emitted with -C rpath) not take precedence
over LD_LIBRARY_PATH.cargo rustc accepts a --profile flag that runs rustc under
any of the compilation profiles, ‘dev’, ‘bench’, or ‘test’.rerun-if-changed build script directive no longer causes the
build script to incorrectly run twice in certain scenarios.private_in_public lint.".".parse::<f32>() returns Err, not Ok(0.0).#![no_std] attribute causes a crate to not be linked to the
standard library, but only the core library, as described
in RFC 1184. The core library defines common types and traits but
has no platform dependencies whatsoever, and is the basis for Rust
software in environments that cannot support a full port of the
standard library, such as operating systems. Most of the core
library is now stable.Read::read_exact,
ErrorKind::UnexpectedEof (renamed from UnexpectedEOF),
fs::DirBuilder, fs::DirBuilder::new,
fs::DirBuilder::recursive, fs::DirBuilder::create,
os::unix::fs::DirBuilderExt,
os::unix::fs::DirBuilderExt::mode, vec::Drain,
vec::Vec::drain, string::Drain, string::String::drain,
vec_deque::Drain, vec_deque::VecDeque::drain,
collections::hash_map::Drain,
collections::hash_map::HashMap::drain,
collections::hash_set::Drain,
collections::hash_set::HashSet::drain,
collections::binary_heap::Drain,
collections::binary_heap::BinaryHeap::drain,
Vec::extend_from_slice (renamed from push_all),
Mutex::get_mut, Mutex::into_inner, RwLock::get_mut,
RwLock::into_inner,
Iterator::min_by_key (renamed from min_by),
Iterator::max_by_key (renamed from max_by).assert_eq! macro supports arguments that don’t implement
Sized, such as arrays. In this way it behaves more like
assert!.Duration. These
include Condvar::wait_timeout_ms, thread::sleep_ms, and
thread::park_timeout_ms.Vec reserves additional elements was
tweaked to not allocate excessive space while still growing
exponentially.From conversions are implemented from integers to floats
in cases where the conversion is lossless. Thus they are not
implemented for 32-bit ints to f32, nor for 64-bit ints to f32
or f64. They are also not implemented for isize and usize
because the implementations would be platform-specific. From is
also implemented from f32 to f64.From<&Path> and From<PathBuf> are implemented for Cow<Path>.From<T> is implemented for Box<T>, Rc<T> and Arc<T>.IntoIterator is implemented for &PathBuf and &Path.BinaryHeap was refactored for modest performance
improvements.$CARGO_HOME/bin for subcommands by default.rerun-if-changed key.cargo clean accepts a --release flag to clean the
release folder. A variety of artifacts that Cargo failed to clean
are now correctly deleted.unreachable_code lint warns when a function call’s argument
diverges.RUST_PATH
environment variable when locating crates. This was a pre-cargo
feature for integrating with the package manager that was
accidentally never removed.Foo(..)) can no longer be used to match
unit structs. This is a warning now, but will become an error in
future releases. Patterns that share the same name as a const are
now an error.BinaryHeap::from, BinaryHeap::into_sorted_vec,
BinaryHeap::into_vec, Condvar::wait_timeout,
FileTypeExt::is_block_device, FileTypeExt::is_char_device,
FileTypeExt::is_fifo, FileTypeExt::is_socket,
FileTypeExt, Formatter::alternate, Formatter::fill,
Formatter::precision, Formatter::sign_aware_zero_pad,
Formatter::sign_minus, Formatter::sign_plus,
Formatter::width, Iterator::cmp, Iterator::eq,
Iterator::ge, Iterator::gt, Iterator::le,
Iterator::lt, Iterator::ne, Iterator::partial_cmp,
Path::canonicalize, Path::exists, Path::is_dir,
Path::is_file, Path::metadata, Path::read_dir,
Path::read_link, Path::symlink_metadata,
Utf8Error::valid_up_to, Vec::resize,
VecDeque::as_mut_slices, VecDeque::as_slices,
VecDeque::insert, VecDeque::shrink_to_fit,
VecDeque::swap_remove_back, VecDeque::swap_remove_front,
slice::split_first_mut, slice::split_first,
slice::split_last_mut, slice::split_last,
char::from_u32_unchecked, fs::canonicalize,
str::MatchIndices, str::RMatchIndices,
str::match_indices, str::rmatch_indices,
str::slice_mut_unchecked, string::ParseError.~/.cargo/bin with the cargo install command. Among other
things this makes it easier to augment Cargo with new subcommands:
when a binary named e.g. cargo-foo is found in $PATH it can be
invoked as cargo foo.*) dependencies will emit warnings when
published. In 1.6 it will no longer be possible to publish
crates with wildcard dependencies.AsRef and AsMut were added to Box, Rc,
and Arc. Because these smart pointer types implement
Deref, this causes breakage in cases where the interior type
contains methods of the same name.Self are not object
safe. Soundness fix.no_default_libraries
setting that controls whether -nodefaultlibs is passed to the
linker, and in turn the is_like_windows setting no longer affects
the -nodefaultlibs flag.#[derive(Show)], long-deprecated, has been removed.#[inline] and #[repr] attributes can only appear
in valid locations.#[no_debug] and
#[omit_gdb_pretty_printer_section] are feature gated.use statements to import unstable
features.improper_ctypes lint no longer warns about using isize and
usize in FFI.Arc<T> and Rc<T> are covariant with respect to T instead of
invariant.Default is implemented for mutable slices.FromStr is implemented for SockAddrV4 and SockAddrV6.From conversions between floating point
types where the conversions are lossless.From conversions between integer types where
the conversions are lossless.fs::Metadata implements Clone.parse method accepts a leading “+” when parsing
integers.AsMut is implemented for Vec.clone_from implementations for String and BinaryHeap have
been optimized and no longer rely on the default impl.extern "Rust", extern "C", unsafe extern "Rust" and
unsafe extern "C" function types now implement Clone,
PartialEq, Eq, PartialOrd, Ord, Hash, fmt::Pointer, and
fmt::Debug for up to 12 arguments.Vecs is much faster in unoptimized builds when the
element types don’t implement Drop.VecDeque
with zero-sized types was resolved.PartialOrd for slices is faster.str::lines and BufRead::lines iterators treat \r\n as
line breaks in addition to \n.'static lifetime extend to the end of a function.str::parse no longer introduces avoidable rounding error when
parsing floating point numbers. Together with earlier changes to
float formatting/output, “round trips” like f.to_string().parse()
now preserve the value of f exactly. Additionally, leading plus
signs are now accepted.use statements that import multiple items can now rename
them, as in use foo::{bar as kitten, baz as puppy}.pub extern crate, which does not behave as expected, issues a
warning until a better solution is found.<Box<str>>::into_string,
Arc::downgrade, Arc::get_mut, Arc::make_mut,
Arc::try_unwrap, Box::from_raw, Box::into_raw, CStr::to_str,
CStr::to_string_lossy, CString::from_raw, CString::into_raw,
IntoRawFd::into_raw_fd, IntoRawFd,
IntoRawHandle::into_raw_handle, IntoRawHandle,
IntoRawSocket::into_raw_socket, IntoRawSocket, Rc::downgrade,
Rc::get_mut, Rc::make_mut, Rc::try_unwrap, Result::expect,
String::into_boxed_str, TcpStream::read_timeout,
TcpStream::set_read_timeout, TcpStream::set_write_timeout,
TcpStream::write_timeout, UdpSocket::read_timeout,
UdpSocket::set_read_timeout, UdpSocket::set_write_timeout,
UdpSocket::write_timeout, Vec::append, Vec::split_off,
VecDeque::append, VecDeque::retain, VecDeque::split_off,
rc::Weak::upgrade, rc::Weak, slice::Iter::as_slice,
slice::IterMut::into_slice, str::CharIndices::as_str,
str::Chars::as_str, str::split_at_mut, str::split_at,
sync::Weak::upgrade, sync::Weak, thread::park_timeout,
thread::sleep.BTreeMap::with_b,
BTreeSet::with_b, Option::as_mut_slice, Option::as_slice,
Result::as_mut_slice, Result::as_slice, f32::from_str_radix,
f64::from_str_radix.std::io::copy allows ?Sized arguments.Windows, Chunks, and ChunksMut iterators over slices all
override count, nth and last with an O(1)
implementation.Default is implemented for arrays up to [T; 32].IntoRawFd has been added to the Unix-specific prelude,
IntoRawSocket and IntoRawHandle to the Windows-specific
prelude.Extend<String> and FromIterator<String are both implemented for
String.IntoIterator is implemented for references to Option and
Result.HashMap and HashSet implement Extend<&T> where T: Copy as part of RFC 839. This will cause type inference
breakage in rare situations.BinaryHeap implements Debug.Borrow and BorrowMut are implemented for fixed-size
arrays.extern fns with the “Rust” and “C” ABIs implement common
traits including Eq, Ord, Debug, Hash.&mut T where T: std::fmt::Write also implements
std::fmt::Write.VecDeque::push_back and other
capacity-altering methods that caused panics for zero-sized types
was fixed.isize and
usize.cargo update.&'a Box<Trait> (or &'a Rc<Trait>, etc) will change from
being interpreted as &'a Box<Trait+'a> to &'a Box<Trait+'static>.Duration API, has been stabilized. This basic unit of
timekeeping is employed by other std APIs, as well as out-of-tree
time crates.#[prelude_import] attribute, an internal implementation
detail, was accidentally stabilized previously. It has been put
behind the prelude_import feature gate. This change is
believed to break no existing code.size_of_val and align_of_val is
more sane for dynamically sized types. Code that relied on
the previous behavior is thought to be broken.dropck rules, which checks that destructors can’t access
destroyed values, have been updated to match the
RFC. This fixes some soundness holes, and as such will
cause some previously-compiling code to no longer build.size_of_val and align_of_val is
more sane for dynamically sized types. Code that relied on
the previous behavior is not known to exist, and suspected to be
broken.'static variables may now be recursive.ref bindings choose between Deref and DerefMut
implementations correctly.dropck rules, which checks that destructors can’t access
destroyed values, have been updated to match the
RFC.Duration API, has been stabilized, as well as the
std::time module, which presently contains only Duration.Box<str> and Box<[T]> both implement Clone.CString, implements Borrow and the
borrowed C string, CStr, implements ToOwned. The two of
these allow C strings to be borrowed and cloned in generic code.CStr implements Debug.AtomicPtr implements Debug.Error trait objects can be downcast to their concrete types
in many common configurations, using the is, downcast,
downcast_ref and downcast_mut methods, similarly to the
Any trait.contains, find,
rfind, split. starts_with and
ends_with are also faster.PartialEq for slices is much faster.Hash trait offers the default method, hash_slice, which
is overridden and optimized by the implementations for scalars.Hasher trait now has a number of specialized write_*
methods for primitive types, for efficiency.std::io::Error, gained a set of
methods for accessing the ‘inner error’, if any: get_ref,
get_mut, into_inner. As well, the implementation
of std::error::Error::cause also delegates to the inner
error.process::Child gained the id method, which returns a
u32 representing the platform-specific process identifier.connect method on slices is deprecated, replaced by the new
join method (note that both of these are on the unstable
SliceConcatExt trait, but through the magic of the prelude are
available to stable code anyway).Div operator is implemented for Wrapping types.DerefMut is implemented for String.HashMap) is
better for long data.AtomicPtr implements Send.read_to_end implementations for Stdin and File
are now specialized to use uninitialized buffers for increased
performance.--explain flag.dropck pass, which checks that destructors can’t access
destroyed values, has been rewritten. This fixes some
soundness holes, and as such will cause some previously-compiling
code to no longer build.rustc now uses LLVM to write archive files where possible.
Eventually this will eliminate the compiler’s dependency on the ar
utility.unused_mut, unconditional_recursion,
improper_ctypes, and negate_unsigned lints are
more strict.-Z no-landing-pads), panic!
will kill the process instead of leaking.Rc to contain types without a fixed size, arrays and trait
objects, finally enabling use of Rc<[T]> and completing the
implementation of DST.-C codegen-units=N flag to
rustc.to_uppercase and to_lowercase methods on char now do
unicode case mapping, which is a previously-planned change in
behavior and considered a bugfix.mem::align_of now specifies the minimum alignment for
T, which is usually the alignment programs are interested
in, and the same value reported by clang’s
alignof. mem::min_align_of is deprecated. This is not known to
break real code.#[packed] attribute is no longer silently accepted by the
compiler. This attribute did nothing and code that
mentioned it likely did not work as intended.associated_type_defaults feature gate. In 1.1 associated type
defaults did not work, but could be mentioned syntactically. As
such this breakage has minimal impact.ref mut now correctly invoke DerefMut when
matching against dereferenceable values.Extend trait, which grows a collection from an iterator, is
implemented over iterators of references, for String, Vec,
LinkedList, VecDeque, EnumSet, BinaryHeap, VecMap,
BTreeSet and BTreeMap. RFC.iter::once function returns an iterator that yields a single
element, and iter::empty returns an iterator that yields no
elements.matches and rmatches methods on str return iterators
over substring matches.Cell and RefCell both implement Eq.wrapping_div, wrapping_rem,
wrapping_neg, wrapping_shl, wrapping_shr. These are in
addition to the existing wrapping_add, wrapping_sub, and
wrapping_mul methods, and alternatives to the Wrapping
type.. It is illegal for the default arithmetic operations in Rust
to overflow; the desire to wrap must be explicit.{:#?} formatting specifier displays the alternate,
pretty-printed form of the Debug formatter. This
feature was actually introduced prior to 1.0 with little
fanfare.fmt::Formatter implements fmt::Write, a fmt-specific trait
for writing data to formatted strings, similar to io::Write.fmt::Formatter adds ‘debug builder’ methods, debug_struct,
debug_tuple, debug_list, debug_set, debug_map. These
are used by code generators to emit implementations of Debug.str has new to_uppercase and to_lowercase
methods that convert case, following Unicode case mapping.PoisonError
type, returned by failing lock operations, exposes into_inner,
get_ref, and get_mut, which all give access to the inner lock
guard, and allow the poisoned lock to continue to operate. The
is_poisoned method of RwLock and Mutex can poll for a
poisoned lock without attempting to take the lock.FromRawFd trait is implemented for Stdio, and
AsRawFd for ChildStdin, ChildStdout, ChildStderr.
On Windows the FromRawHandle trait is implemented for Stdio,
and AsRawHandle for ChildStdin, ChildStdout,
ChildStderr.io::ErrorKind has a new variant, InvalidData, which indicates
malformed input.rustc employs smarter heuristics for guessing at typos.rustc emits more efficient code for no-op conversions between
unsafe pointers.std::fs module has been expanded to expand the set of
functionality exposed:
DirEntry now supports optimizations like file_type and metadata which
don’t incur a syscall on some platforms.symlink_metadata function has been added.fs::Metadata structure now lowers to its OS counterpart, providing
access to all underlying information.--explain flag
to read the explanation. Error explanations are also available online.str::split_whitespace method splits a string on unicode
whitespace boundaries.FromRawFd and AsRawFd, on Windows FromRawHandle
and AsRawHandle. These are implemented for File, TcpStream,
TcpListener, and UpdSocket. Further implementations for
std::process will be stabilized later.std::os::unix::symlink creates symlinks. On
Windows, symlinks can be created with
std::os::windows::symlink_dir and
std::os::windows::symlink_file.mpsc::Receiver type can now be converted into an iterator with
into_iter on the IntoIterator trait.Ipv4Addr can be created from u32 with the From<u32>
implementation of the From trait.Debug implementation for RangeFull creates output that is
more consistent with other implementations.Debug is implemented for File.Default implementation for Arc no longer requires Sync + Send.Iterator methods count, nth, and last have been
overridden for slices to have O(1) performance instead of O(n).AtomicPtr gained a Default implementation.abs now
panics on overflow when debug assertions are enabled.Cloned iterator, which was accidentally left unstable for
1.0 has been stabilized.Incoming iterator, which iterates over incoming TCP
connections, and which was accidentally unnamable in 1.0, is now
properly exported.BinaryHeap no longer corrupts itself when functions called by
sift_up or sift_down panic.split_off method of LinkedList no longer corrupts
the list in certain scenarios.target_env cfg value, which is used for
distinguishing toolchains that are otherwise for the same
platform. Presently this is set to gnu for common GNU Linux
targets and for MinGW targets, and musl for MUSL Linux targets.cargo rustc command invokes a build with custom flags
to rustc.drop_with_repr_extern lint warns about mixing repr(C)
with Drop.#[stable]. It is
no longer possible to use unstable features with a stable build of
the compiler.0b1234 is
now lexed as 0b1234 instead of two tokens, 0b1 and 234.PhantomFn and MarkerTrait lang items, which have been
removed.extern crate "foo" as bar syntax has been replaced with extern crate foo as bar, and Cargo now automatically translates “-” in package names
to underscore for the crate name.Send no longer implies 'static.MyType::default().SliceExt.Self: Sized in their where clause are considered
object-safe, allowing many extension traits like
IteratorExt to be merged into the traits they extended.where clause.Send and Sync are now library-defined.Any trait is effectively limited to concrete
types. This helps retain the potentially-important “parametricity”
property: generic code cannot behave differently for different type
arguments except in minor ways.unsafe_destructor feature is now deprecated in favor of the
new dropck. This change is a major reduction in unsafe
code.thread_local module has been renamed to std::thread.IteratorExt have been moved to the Iterator
trait itself.AsMut, AsRef, From, and Into have been
centralized in the std::convert module.FromError trait was removed in favor of From.std::thread::sleep_ms.splitn function now takes an n parameter that represents the
number of items yielded by the returned iterator instead of the
number of ‘splits’.CLOEXEC by default.PartialOrd now order enums according
to their explicitly-assigned discriminants.Patterns,
implemented presently by &char, &str, FnMut(char) -> bool and
some others.String::from_str has been deprecated in favor of the From impl,
String::from.io::Error implements Sync.words method on &str has been replaced with
split_whitespace, to avoid answering the tricky question, ‘what is
a word?’#[stable]. This
was the major library focus for this cycle..,
adjusting the tradeoffs in favor of the most common usage.std were also stabilized
during this cycle; about 75% of the non-deprecated API surface
is now stable.Fn traits are now related via inheritance
and provide ergonomic blanket implementations.Index and IndexMut traits were changed to
take the index by value, enabling code like
hash_map["string"] to work.Copy now inherits from Clone, meaning that all
Copy data is known to be Clone as well.--explain flag to rustc.~1300 changes, numerous bugfixes
Highlights
io module remains temporarily
at std::old_io.#![feature(...)]
attribute. The impact of this change is described on the
forum. RFC.Language
for loops now operate on the IntoIterator trait,
which eliminates the need to call .iter(), etc. to iterate
over collections. There are some new subtleties to remember
though regarding what sort of iterators various types yield, in
particular that for foo in bar { } yields values from a move
iterator, destroying the original collection. RFC.Box<Trait+'static> when you don’t care about
storing references. RFC.Drop, lifetimes must outlive the
value. This will soon make it possible to safely
implement Drop for types where #[unsafe_destructor] is now
required. Read the gorgeous RFC for details.Deref<U> now automatically
coerce to references to the dereferenced type U,
e.g. &T where T: Deref<U> automatically coerces to &U. This
should eliminate many unsightly uses of &*, as when converting
from references to vectors into references to
slices. RFC.|&:|, |&mut:|,
|:|) is obsolete and closure kind is inferred from context.Self is a keyword.Libraries
Show and String formatting traits have been
renamed to Debug and Display to more clearly reflect
their related purposes. Automatically getting a string
conversion to use with format!("{:?}", something_to_debug) is
now written #[derive(Debug)].std::ff::{OsString, OsStr}, provide strings in platform-specific encodings for easier
interop with system APIs. RFC.boxed::into_raw and Box::from_raw functions convert
between Box<T> and *mut T, a common pattern for
creating raw pointers.Tooling
/usr/local/lib/rustlib/uninstall.sh.#[rustc_on_unimplemented] attribute, requiring the
‘on_unimplemented’ feature, lets rustc display custom error
messages when a trait is expected to be implemented for a type
but is not.Misc
~2400 changes, numerous bugfixes
Highlights
isize and
usize, rather than int and uint, for pointer-sized
integers. Guidelines will be rolled out during the alpha cycle.std have been moved out of the Rust
distribution into the Cargo ecosystem so they can evolve
separately and don’t need to be stabilized as quickly, including
‘time’, ‘getopts’, ‘num’, ‘regex’, and ‘term’.Language
where clauses provide a more versatile and attractive
syntax for specifying generic bounds, though the previous syntax
remains valid.str) more deeply into the type system, making it
more consistent.i..j, i.., and
..j that produce range types and which, when combined with the
Index operator and multidispatch, leads to a convenient slice
notation, [i..j].[T; N].Copy trait is no longer implemented automatically. Unsafe
pointers no longer implement Sync and Send so types
containing them don’t automatically either. Sync and Send
are now ‘unsafe traits’ so one can “forcibly” implement them via
unsafe impl if a type confirms to the requirements for them
even though the internals do not (e.g. structs containing unsafe
pointers like Arc). These changes are intended to prevent some
footguns and are collectively known as opt-in built-in
traits (though Sync and Send will soon become pure
library types unknown to the compiler).String to be
compared with &str.if let and while let are no longer feature-gated.macro_rules! has been declared stable. Though it is a
flawed system it is sufficiently popular that it must be usable
for 1.0. Effort has gone into future-proofing it
in ways that will allow other macro systems to be developed in
parallel, and won’t otherwise impact the evolution of the
language.vec![1i32, 2, 3].len() work as expected.#[derive(...)]
not #[deriving(...)] for consistency with other naming
conventions.self instead
of mod, as in use foo::{self, bar}box operator and box patterns have been feature-gated
pending a redesign. For now unique boxes should be allocated
like other containers, with Box::new.Libraries
fail! macro has been renamed to panic! so that
it is easier to discuss failure in the context of error handling
without making clarifications as to whether you are referring to
the ‘fail’ macro or failure more generally.OsRng prefers the new, more reliable getrandom
syscall when available.Show formatter, typically implemented with
#[derive(Show)] is now requested with the {:?}
specifier and is intended for use by all types, for uses
such as println! debugging. The new String formatter must be
implemented by hand, uses the {} specifier, and is intended
for full-fidelity conversions of things that can logically be
represented as strings.Tooling
Misc
Option<Vec<T>> and Option<String> take up no more
space than the inner types themselves.~1900 changes, numerous bugfixes
Highlights
std have been reviewed and updated for
consistency with the in-development Rust coding
guidelines. The standard library documentation tracks
stabilization progress.Language
Index and IndexMut
traits.if let construct takes a branch only if the let pattern
matches, currently behind the ‘if_let’ feature gate.[0..4]) has been introduced behind
the ‘slicing_syntax’ feature gate, and can be overloaded with
the Slice or SliceMut traits... instead of prefix (.e.g. [a, b, c..]), for
consistency with other uses of .. and to future-proof
potential additional uses of the syntax.0..3 to 0...4 to be consistent with the exclusive range
syntax for slicing.[a.., b, c]) has been put behind the ‘advanced_slice_patterns’ feature
gate and may be removed in the future.value.0 syntax, currently behind the tuple_indexing
feature gate.#[crate_id] attribute is no longer supported; versioning
is handled by the package manager.extern crate foo as bar
instead of extern crate bar = foo.use foo as bar instead
of use bar = foo.let and match bindings and argument names in macros are now
hygienic.move has been added as a keyword, for indicating closures
that capture by value.Share trait is now called Sync to free up the term
‘shared’ to refer to ‘shared reference’ (the default reference
type.Sized trait has been
introduced, which qualifying types implement by default, and
which type parameters expect by default. To specify that a type
parameter does not need to be sized, write <Sized? T>. Most
types are Sized, notable exceptions being unsized arrays
([T]) and trait types.!, as in || -> ! or proc() -> !.Gc<T> which was once
denoted by the @ sigil, has finally been removed. GC will be
revisited in the future.Libraries
std::time::Duration type has been added for use in I/O
methods that rely on timers, as well as in the ‘time’ crate’s
Timespec arithmetic.collections::btree has been rewritten to have a more
idiomatic and efficient design.Tooling
--crate-name flag can specify the name of the crate
being compiled, like #[crate_name].-C metadata specifies additional metadata to hash into
symbol names, and -C extra-filename specifies additional
information to put into the output filename, for use by the
package manager for versioning.-C codegen-units flag.Misc
~1700 changes, numerous bugfixes
Language
uint
instead of any integral type.b.<'a>|A, B|: 'b + K -> Tpriv keyword has been removed from the language.use foo, bar, baz; syntax has been removed from the language.int, and floating point
literals no longer default to f64. Literals must be suffixed with an
appropriate type if inference cannot determine the type of the
literal.Libraries
rev() on
their forward-iteration counterparts.--cfg ndebug is passed to the compiler.Tooling
[breaking-change] to allow for easy
discovery of breaking changes.mod foo;.pub use has been greatly improved.~1500 changes, numerous bugfixes
Language
@-pointers have been removed from the language.~[T]) have been removed from the
language.~str) have been removed from the
language.@str has been removed from the language.@[T] has been removed from the language.@self has been removed from the language.@Trait has been removed from the language.~ allocations which contain @ boxes inside the type for
reference counting have been removed.macro_rules! macros as
well as syntax extensions such as format!.#[deriving] with raw pointerslog_syntax! are now behind feature gates.#[simd] attribute is now behind a feature gate.extern crate statements, and
unnecessary visibility (priv) is no longer allowed on use statements.do keyword has been removed, it is now a reserved keyword.extern mod is now extern crateFreeze trait has been removed.Share trait has been added for types that can be shared among
threads.{} now.static mut locations has been tweaked.* and . operators are now overloadable through the Deref and
DerefMut traits.~Trait and proc no longer have Send bounds by default._ type marker.Unsafe type was introduced for interior mutability. It is now
considered undefined to transmute from &T to &mut T without using the
Unsafe type.#[foo]; to #![foo].Pod was renamed to Copy.Libraries
libextra library has been removed. It has now been decomposed into
component libraries with smaller and more focused nuggets of
functionality. The full list of libraries can be found on the
documentation index page.std::condition has been removed. All I/O errors are now propagated
through the Result type. In order to assist with error handling, a
try! macro for unwrapping errors with an early return and a lint for
unused results has been added. See #12039 for more information.vec module has been renamed to slice.Vec<T>, has been added in preparation for DST.
This will become the only growable vector in the future.std::io now has more public re-exports. Types such as BufferedReader
are now found at std::io::BufferedReader instead of
std::io::buffered::BufferedReader.print and println are no longer in the prelude, the print! and
println! macros are intended to be used instead.Rc now has a Weak pointer for breaking cycles, and it no longer
attempts to statically prevent cycles.slice::last()) now return Option<T> instead of T + failing.fmt::Default has been renamed to fmt::Show, and it now has a new
deriving mode: #[deriving(Show)].ToStr is now implemented for all types implementing Show.&self instead of &Tinvert() method on iterators has been renamed to rev()std::num has seen a reduction in the genericity of its traits,
consolidating functionality into a few core traits.RUST_BACKTRACE is present.eof() has been removed from the Reader trait. Specific types may
still implement the function.assert_approx_eq! has been removede and E formatting specifiers for floats have been added to
print them in exponential notation.Times trait has been removedstd::kinds::marker nowhash has been rewritten, IterBytes has been removed, and
#[deriving(Hash)] is now possible.SharedChan has been removed, Sender is now cloneable.Chan and Port were renamed to Sender and Receiver.Chan::new is now channel().select! macro is now provided for selecting over Receivers.hashmap and trie have been moved to libcollectionsrun has been rolled into io::processassert_eq! now uses {} instead of {:?}rand has moved to librand.to_{lower,upper}case has been implemented for char.liblog.HashMap has been rewritten for higher performance and less
memory usage.libnative. If libgreen is desired,
it can be booted manually. The runtime guide has more information and
examples.libgreen has been optimized with stack caching
and various trimming of code.libgreen now have an unmapped guard page.extra::sync module has been updated to modern rust (and moved
to the sync library), tweaking and improving various interfaces while
dropping redundant functionality.Barrier type has been added to the sync library.base64 module has seen some improvement. It treats
newlines better, has non-string error values, and has seen general
cleanup.fourcc! macro was introducedhexfloat! macro was implemented for specifying floats via a
hexadecimal literal.Tooling
rustpkg has been deprecated and removed from the main repository. Its
replacement, cargo, is under development.--emit flag.--crate-type flag.-C flag.rustdoc improvements:
~1800 changes, numerous bugfixes
Language
float type has been removed. Use f32 or f64 instead.#[feature(foo)] attribute.#[feature(managed_boxes)]) in preparation for future removal. Use the
standard library’s Gc or Rc types instead.@mut has been removed. Use std::cell::{Cell, RefCell} instead.continue instead of
loop.r"foo" syntax or with matched
hash delimiters, as in r###"foo"###.~fn is now written proc (args) -> retval { ... } and may only be
called once.&fn type is now written |args| -> ret to match the literal form.@fns have been removed.do only works with procs in order to make it obvious what the cost
of do is.#[link(...)] attribute has been replaced with
#[crate_id = "name#vers"].impls must be terminated with empty braces and may not be
terminated with a semicolon.self lifetime
no longer has any special meaning.fmt! string formatting macro has been removed.printf! and printfln! (old-style formatting) removed in favor of
print! and println!.mut works in patterns now, as in let (mut x, y) = (1, 2);.extern mod foo (name = "bar") syntax has been removed. Use
extern mod foo = "bar" instead.alignof, offsetof, sizeof.asm! macro is feature-gated (#[feature(asm)]).as.repr attribute can be used to override
the discriminant size, as in #[repr(int)] for integer-sized, and
#[repr(C)] to match C enums.0o7777.concat! syntax extension performs compile-time string concatenation.#[fixed_stack_segment] and #[rust_stack] attributes have been
removed as Rust no longer uses segmented stacks.#[feature(non_ascii_idents)])...,
not *; ignoring remaining fields of a struct is also done with ..,
not _; ignoring a slice of a vector is done with .., not .._.rustc supports the “win64” calling convention via extern "win64".rustc supports the “system” calling convention, which defaults to the
preferred convention for the target platform, “stdcall” on 32-bit Windows,
“C” elsewhere.type_overflow lint (default: warn) checks literals for overflow.unsafe_block lint (default: allow) checks for usage of unsafe.attribute_usage lint (default: warn) warns about unknown
attributes.unknown_features lint (default: warn) warns about unknown
feature gates.dead_code lint (default: warn) checks for dead code.#[link_args] is behind the link_args feature gate.#[link(name = "foo")]#[link(name = "foo", kind = "static")]).#[link(name = "foo", kind = "framework")]).#[thread_local] attribute creates thread-local (not task-local)
variables. Currently behind the thread_local feature gate.return keyword may be used in closures.Pod kind.cfg attribute can now be used on struct fields and enum variants.Libraries
option and result API’s have been overhauled to make them
simpler, more consistent, and more composable.std::io module has been replaced with one that is
more comprehensive and that properly interfaces with the underlying
scheduler. File, TCP, UDP, Unix sockets, pipes, and timers are all
implemented.io::util contains a number of useful implementations of
Reader and Writer, including NullReader, NullWriter,
ZeroReader, TeeReader.extra::rc moved into std.Gc type in the gc module will replace @ (it is currently
just a wrapper around it).Either type has been removed.fmt::Default can be implemented for any type to provide default
formatting to the format! macro, as in format!("{}", myfoo).rand API continues to be tweaked.rust_begin_unwind function, useful for inserting breakpoints
on failure in gdb, is now named rust_fail.each_key and each_value methods on HashMap have been
replaced by the keys and values iterators.sys module to the mem module.path module was written and API changed.str::from_utf8 has been changed to cast instead of allocate.starts_with and ends_with methods added to vectors via the
ImmutableEqVector trait, which is in the prelude.get_opt method, which returns None
if the index is out of bounds.Any type can be used for dynamic typing.~Any can be passed to the fail! macro and retrieved via
task::try._iter
suffix now.cell::Cell and cell::RefCell can be used to introduce mutability
roots (mutable fields, etc.). Use instead of e.g. @mut.util::ignore renamed to prelude::drop.sort and sort_by methods via the MutableVector
trait.vec::raw has seen a lot of cleanup and API changes.comm module has been rewritten to be much faster, have a
simpler, more consistent API, and to work for both native and green
threading.flatpipes module had bitrotted and was removed.c_vec has been modernized.sort module has been removed. Use the sort method on
mutable slices.Tooling
rust and rusti commands have been removed, due to lack of
maintenance.rustdoc was completely rewritten.rustdoc can test code examples in documentation.rustpkg can test packages with the argument, ‘test’.rustpkg supports arbitrary dependencies, including C libraries.rustc’s support for generating debug info is improved again.rustc has better error reporting for unbalanced delimiters.rustc’s JIT support was removed due to bitrot.rustc adds a --dep-info flag for communicating dependencies to
build tools.~2200 changes, numerous bugfixes
Language
for loop syntax has changed to work with the Iterator trait.copy is no longer a keyword. It has been replaced by the Clone trait.debug! macro if it is passed
--cfg ndebugmod foo;, rustc will now look
for foo.rs, then foo/mod.rs, and will generate an error when both are
present.std::c_str module
provides new mechanisms for converting to C strings.extern "C" fn instead of `*u8’.#[fixed_stack_segment] attribute.externfn! macro can be used to declare both a foreign function and
a #[fixed_stack_segment] wrapper at once.pub and priv modifiers on extern blocks are no longer parsed.unsafe is no longer allowed on extern fns - they are all unsafe.priv is disallowed everywhere except for struct fields and enum variants.&T (besides &'static T) is no longer allowed in @T.ref bindings in irrefutable patterns work correctly now.char is now prevented from containing invalid code points.bool is no longer allowed.\0 is now accepted as an escape in chars and strings.yield is a reserved keyword.typeof is a reserved keyword.extern mod foo = "url";.enum E { V = 0u }static foo: [u8, .. 100]: [0, .. 100];.static foo: Foo = Foo { a: 5, .. bar };.cfg! can be used to conditionally execute code based on the crate
configuration, similarly to #[cfg(...)].unnecessary_qualification lint detects unneeded module
prefixes (default: allow).std::unstable::simd.format! implements a completely new, extensible, and higher-performance
string formatting system. It will replace fmt!.print! and println! write formatted strings (using the format!
extension) to stdout.write! and writeln! write formatted strings (using the format!
extension) to the new Writers in std::rt::io.#[link_section = "..."].proto! syntax extension for defining bounded message protocols
was removed.macro_rules! is hygienic for let declarations.#[export_name] attribute specifies the name of a symbol.unreachable! can be used to indicate unreachable code, and fails
if executed.Libraries
rt::io, based on the new
runtime.range function was added to the prelude, replacing
uint::range and friends.range_rev no longer exists. Since range is an iterator it can be
reversed with range(lo, hi).invert().chain method on option renamed to and_then; unwrap_or_default
renamed to unwrap_or.iterator module was renamed to iter.checked_add, checked_sub, and
checked_mul operations for detecting overflow.str, vec, option, result` were renamed for
consistency.to_foo for copying, into_foo for moving, as_foo for temporary
and cheap casts.CString type in c_str provides new ways to convert to and
from C strings.DoubleEndedIterator can yield elements in two directions.mut_split method on vectors partitions an &mut [T] into
two splices.str::from_bytes renamed to str::from_utf8.pop_opt and shift_opt methods added to vectors.swap_unwrap method of Option renamed to take_unwrap.SharedPort to comm.Eq has a default method for ne; only eq is required
in implementations.Ord has default methods for le, gt and ge; only lt
is required in implementations.is_utf8 performance is improved, impacting many string functions.os::MemoryMap provides cross-platform mmap.ptr::offset is now unsafe, but also more optimized. Offsets that
are not ‘in-bounds’ are considered undefined.vec removed in favor of methods.FromIterator so can be created by the
collect method.unstable::atomics.comm::PortSet removed.Set and Map traits have been moved into
the MutableSet and MutableMap traits. Container::is_empty,
Map::contains_key, MutableMap::insert, and MutableMap::remove have
default implementations.from_str functions were removed in favor of a generic
from_str which is available in the prelude.util::unreachable removed in favor of the unreachable! macro.dlist, the doubly-linked list was modernized.hex module with ToHex and FromHex traits.glob module, replacing std::os::glob.rope was removed.deque was renamed to ringbuf. RingBuf implements Deque.net, and timer were removed. The experimental replacements
are std::rt::io::net and std::rt::io::timer.SmallIntMap.Bitv and BitvSet.SmallIntSet removed. Use BitvSet.semver updated to SemVer 2.0.0.term handles more terminals correctly.dbg module removed.par module removed.future was cleaned up, with some method renames.getopts were converted to methods.Other
-Z debug-info) is greatly improved.--target-cpu to compile to a specific CPU architecture,
similarly to gcc’s --march flag.--test now support the -h and --help flags.rustdoc command.~2000 changes, numerous bugfixes
Language
impls no longer accept a visibility qualifier. Put them on methods
instead.self parameter no longer implicitly means &'self self,
and can be explicitly marked with a lifetime.+=, etc.) have been temporarily
removed due to bugs.for loop protocol now requires for-iterators to return bool
so they compose better.Durable trait is replaced with the 'static bounds.#[packed] attribute have byte alignment and
no padding between fields.Copy must now be copied explicitly with
the copy keyword.Option<~T> is now represented as a nullable pointer.@mut does dynamic borrow checks correctly.main function is only detected at the topmost level of the crate.
The #[main] attribute is still valid anywhere.#[no_send] attribute makes a type that would otherwise be
Send, not.#[no_freeze] attribute makes a type that would otherwise be
Freeze, not.RUST_MAX_STACK environment variable (default: 1GB).vecs_implicitly_copyable lint mode has been removed. Vectors
are never implicitly copyable.#[static_assert] makes compile-time assertions about static bools.use mod statement no longer exists.Syntax extensions
fail! and assert! accept ~str, &'static str or fmt!-style
argument list.Encodable, Decodable, Ord, TotalOrd, TotalEq, DeepClone,
Rand, Zero and ToStr can all be automatically derived with
#[deriving(...)].bytes! macro returns a vector of bytes for string, u8, char,
and unsuffixed integer literals.Libraries
core crate was renamed to std.std crate was renamed to extra.iterator module for external iterator objects.Iterator.any, all. removed.finalize method of Drop renamed to drop.drop method now takes &mut self instead of &self.print, println, FromStr, ApproxEq, Equiv,
Iterator, IteratorUtil, many numeric traits, many tuple traits.Fractional, Real, RealExt, Integer, Ratio,
Algebraic, Trigonometric, Exponential, Primitive.(0, 1, 2).n2() or (0, 1, 2).n2_ref().Clone.path type renamed to Path.mut module and Mut type removed.vec, str. In the future methods will also work as functions.reinterpret_cast removed. Use transmute.std::ascii.Rand is implemented for ~/@.run module for spawning processes overhauled.unstable::atomic.Zero.LinearMap and LinearSet renamed to HashMap and HashSet.ptr to borrow.os::mkdir_recursive.os::glob function performs filesystems globs.FuzzyEq renamed to ApproxEq.Map now defines pop and swap methods.Cell constructors converted to static methods.rc module adds the reference counted pointers, Rc and RcMut.flate module moved from std to extra.fileinput module for iterating over a series of files.Complex number type and complex module.Rational number type and rational module.BigInt, BigUint implement numeric and comparison traits.term uses terminfo now, is more correct.arc functions converted to methods.Tooling
unused_variables lint mode for unused variables (default: warn).unused_unsafe lint mode for detecting unnecessary unsafe blocks
(default: warn).unused_mut lint mode for identifying unused mut qualifiers
(default: warn).dead_assignment lint mode for unread variables (default: warn).unnecessary_allocation lint mode detects some heap allocations that are
immediately borrowed so could be written without allocating (default: warn).missing_doc lint mode (default: allow).unreachable_code lint mode (default: warn).rusti command has been rewritten and a number of bugs addressed.--link-args flag to pass arguments to the linker.-Z print-link-args flag for debugging linkage.-g will make the binary record information about
dynamic borrowcheck failures for debugging.~2100 changes, numerous bugfixes
Syntax changes
Selfself parameter in trait and impl methods must now be explicitly
named (for example: fn f(&self) { }). Implicit self is deprecated.static keyword and instead
are distinguished by the lack of a self parameterDurable trait with the 'static lifetimesuper is a keyword, and may be prefixed to paths+ instead of whitespaceimpl Trait for Type
instead of impl Type: Trait&'l foo instead of &l/fooexport keyword has finally been removedmove keyword has been removed (see “Semantic changes”)[mut T], has been
removed. Use &mut [T], etc.mut is no longer valid in ~mut T. Use inherited mutabilityfail is no longer a keyword. Use fail!()assert is no longer a keyword. Use assert!()log is no longer a keyword. use debug!, etc.(T,)mut. Use inherited mutability,
@mut T, core::mut or core::cellextern mod { ... } is no longer valid syntax for foreign
function modules. Use extern blocks: extern { ... }const renamed to static to correspond to lifetime name,
and make room for future static mut unsafe mutable globals.#[deriving_eq] with #[deriving(Eq)], etc.Clone implementations can be automatically generated with
#[deriving(Clone)]@foo as @Bar
instead of foo as Bar.[int, .. 3]
instead of [int * 3].[int, .. GL_BUFFER_SIZE - 2])Semantic changes
move keyworduse statements may no longer be “chained” - they cannot import
identifiers imported by previous use statementsuse statements are crate relative, importing from the “top”
of the crate by default. Paths may be prefixed with super::
or self:: to change the search behavior.Libraries
std::bigintcore::oldcomm modulecore::comm modulecore::numvec::slice finally returns a slicedebug! and friends don’t require a format string, e.g. debug!(Foo)core::containercore::dvec removed, ~[T] is a drop-in replacementcore::send_map renamed to core::hashmapstd::map removed; replaced with core::hashmapstd::treemap reimplemented as an owned balanced treestd::deque and std::smallintmap reimplemented as owned containerscore::trie added as a fast ordered map for integer keyscore::hashmap, core::trie and std::treemapOrd split into Ord and TotalOrd. Ord is still used to
overload the comparison operators, whereas TotalOrd is used
by certain container typesOther
rustc --test now supports benchmarks with the #[bench] attribute~900 changes, numerous bugfixes
Syntax changes
<- move operator#fmt extension syntax to fmt![T]/Nquote_tokens!, quote_expr!, etc.a.b() is always parsed as a method call, never as a field projectionEq and IterBytes implementations can be automatically generated
with #[deriving_eq] and #[deriving_iter_bytes] respectively.rc filesSemantic changes
& and ~ pointers may point to objectsstruct Foo(Bar, Baz). Will replace newtype enums.move explicitly&T may now be coerced to *Tlet statements as well as function callsuse statements now take crate-relative pathsImproved support for language features
self, &self
@self, and ~self all generally work as expectedLibraries
core::conditionstd::sortstd::priority_queuegetopts definitionsstdcore::comm renamed to oldcomm. Still deprecatedrustdoc and cargo are libraries nowMisc
rusti~2000 changes, numerous bugfixes
Syntax
ret became return and alt became matchimport is now use; use is now extern mod`extern mod { ... } is now extern { ... }use mod is the recommended way to import modulespub and priv replace deprecated export listsmatch pattern arms now uses fat arrow (=>)main no longer accepts an args vector; use os::args insteadSemantics
Libraries
std::net::url for representing URLscore::send_mapConcurrency
core::pipesstd::arc, an atomically reference counted, immutable, shared memory
typestd::sync, various exotic synchronization tools based on arcs and pipesOther
~1900 changes, numerous bugfixes
New coding conveniences
Semantic cleanup
Experimental new language features
Type reflection
Removal of various obsolete features
Keywords: ‘be’, ‘prove’, ‘syntax’, ‘note’, ‘mutable’, ‘bind’, ‘crust’, ‘native’ (now ‘extern’), ‘cont’ (now ‘again’)
Constructs: do-while loops (‘do’ repurposed), fn binding, resources (replaced by destructors)
Compiler reorganization
New library code
Tool improvements
1500 changes, numerous bugfixes
New docs and doc tooling
New port: FreeBSD x86_64
Compilation model enhancements
Scheduling, stack and threading fixes
Experimental new language features
Various language extensions
New library code
Most language features work, including:
Compiler works with the following configurations:
Cross compilation / multi-target configuration supported.
Preliminary API-documentation and package-management tools included.
Known issues:
Documentation is incomplete.
Performance is below intended target.
Standard library APIs are subject to extensive change, reorganization.
Language-level versioning is not yet operational - future code will break unexpectedly.