Version 1.90.0 (2025-09-18)

Language

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

Compiler

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

Platform Support

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

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

Libraries

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

Stabilized APIs

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

These previously stable APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Version 1.89.0 (2025-08-07)

Language

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

Compiler

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

Platform Support

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

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

Libraries

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

Stabilized APIs

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

These previously stable APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.88.0 (2025-06-26)

Language

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

Compiler

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

Platform Support

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

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

Libraries

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

Stabilized APIs

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

These previously stable APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Version 1.87.0 (2025-05-15)

Language

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

Compiler

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

Platform Support

Remove i586-pc-windows-msvc target

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

Libraries

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

Stabilized APIs

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

These previously stable APIs are now stable in const contexts:

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

Cargo

Add terminal integration via ANSI OSC 9;4 sequences
chore: bump openssl to v3
feat(package): add --exclude-lockfile flag

Compatibility Notes

Rust now raises an error for macro invocations inside the #![crate_name] attribute
Unstable fields are now always considered to be inhabited
Macro arguments of unary operators followed by open beginning ranges may now be matched differently
Make Debug impl of raw pointers print metadata if present
Warn against function pointers using unsupported ABI strings in dependencies
Associated types on dyn types are no longer deduplicated
Forbid attributes on .. inside of struct patterns (let Struct { #[attribute] .. }) =
Make ptr_cast_add_auto_to_object lint into hard error
Many std::arch intrinsics are now safe to call in some contexts, there may now be new unused_unsafe warnings in existing codebases.
Limit width and precision formatting options to 16 bits on all targets
Turn order dependent trait objects future incompat warning into a hard error
Denote ControlFlow as #[must_use]
Windows: The standard library no longer links advapi32, except on win7. Code such as C libraries that were relying on this assumption may need to explicitly link advapi32.
Proc macros can no longer observe expanded cfg(true) attributes.
Start changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
Don't allow flattened format_args in const.

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Update to LLVM 20

Version 1.86.0 (2025-04-03)

Language

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

Compiler

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

Platform Support

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

Add a sans-serif font setting.

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.85.1 (2025-03-18)

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

Version 1.85.0 (2025-02-20)

Language

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

Compiler

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

Platform Support

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

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

Libraries

Panics in the standard library now have a leading library/ in their path
std::env::home_dir() on Windows now ignores the non-standard $HOME environment variable

It will be un-deprecated in a subsequent release.
Add AsyncFn* to the prelude in all editions.

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

rustc no longer treats the test cfg as a well known check-cfg, instead it is up to the build systems and users of --check-cfg¹ to set it as a well known cfg using --check-cfg=cfg(test).

This is done to enable build systems like Cargo to set it conditionally, as not all source files are suitable for unit tests. Cargo (for now) unconditionally sets the test cfg as a well known cfg.
Disable potentially incorrect type inference if there are trivial and non-trivial where-clauses
std::env::home_dir() has been deprecated for years, because it can give surprising results in some Windows configurations if the HOME environment variable is set (which is not the normal configuration on Windows). We had previously avoided changing its behavior, out of concern for compatibility with code depending on this non-standard configuration. Given how long this function has been deprecated, we're now fixing its behavior as a bugfix. A subsequent release will remove the deprecation for this function.
Make core::ffi::c_char signedness more closely match that of the platform-default char

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

The libc crate matches this change as of its 0.2.169 release.
When compiling a nested macro_rules macro from an external crate, the content of the inner macro_rules is now built with the edition of the external crate, not the local crate.
Increase sparcv9-sun-solaris and x86_64-pc-solaris Solaris baseline to 11.4.
Show abi_unsupported_vector_types lint in future breakage reports
Error if multiple super-trait instantiations of dyn Trait need associated types to be specified but only one is provided
Change powerpc64-ibm-aix default codemodel to large

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.84.1 (2025-01-30)

Fix ICE 132920 in duplicate-crate diagnostics.
Fix errors for overlapping impls in incremental rebuilds.
Fix slow compilation related to the next-generation trait solver.
Fix debuginfo when LLVM's location discriminator value limit is exceeded.
Fixes for building Rust from source:

Version 1.84.0 (2025-01-09)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts

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

Cargo

Stabilize MSRV-aware resolver config
Stabilize resolver v3

Rustdoc

rustdoc-search: improve type-driven search

Compatibility Notes

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

Version 1.83.0 (2024-11-28)

Language

Stabilize &mut, *mut, &Cell, and *const Cell in const.
Allow creating references to statics in const initializers.
Implement raw lifetimes and labels ('r#ident).
Define behavior when atomic and non-atomic reads race.
Non-exhaustive structs may now be empty.
Disallow implicit coercions from places of type !
const extern functions can now be defined for other calling conventions.
Stabilize expr_2021 macro fragment specifier in all editions.
The non_local_definitions lint now fires on less code and warns by default.

Compiler

Deprecate unsound -Csoft-float flag.
Add many new tier 3 targets:

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

Libraries

Implement PartialEq for ExitCode.
Document that catch_unwind can deal with foreign exceptions without UB, although the exact behavior is unspecified.
Implement Default for HashMap/HashSet iterators that don't already have it.
Bump Unicode to version 16.0.0.
Change documentation of ptr::add/sub to not claim equivalence with offset.

Stabilized APIs

BufRead::skip_until
ControlFlow::break_value
ControlFlow::continue_value
ControlFlow::map_break
ControlFlow::map_continue
DebugList::finish_non_exhaustive
DebugMap::finish_non_exhaustive
DebugSet::finish_non_exhaustive
DebugTuple::finish_non_exhaustive
ErrorKind::ArgumentListTooLong
ErrorKind::Deadlock
ErrorKind::DirectoryNotEmpty
ErrorKind::ExecutableFileBusy
ErrorKind::FileTooLarge
ErrorKind::HostUnreachable
ErrorKind::IsADirectory
ErrorKind::NetworkDown
ErrorKind::NetworkUnreachable
ErrorKind::NotADirectory
ErrorKind::NotSeekable
ErrorKind::ReadOnlyFilesystem
ErrorKind::ResourceBusy
ErrorKind::StaleNetworkFileHandle
ErrorKind::StorageFull
ErrorKind::TooManyLinks
Option::get_or_insert_default
Waker::data
Waker::new
Waker::vtable
char::MIN
hash_map::Entry::insert_entry
hash_map::VacantEntry::insert_entry

These APIs are now stable in const contexts:

Cell::into_inner
Duration::as_secs_f32
Duration::as_secs_f64
Duration::div_duration_f32
Duration::div_duration_f64
MaybeUninit::as_mut_ptr
NonNull::as_mut
NonNull::copy_from
NonNull::copy_from_nonoverlapping
NonNull::copy_to
NonNull::copy_to_nonoverlapping
NonNull::slice_from_raw_parts
NonNull::write
NonNull::write_bytes
NonNull::write_unaligned
OnceCell::into_inner
Option::as_mut
Option::expect
Option::replace
Option::take
Option::unwrap
Option::unwrap_unchecked
Option::<&_>::copied
Option::<&mut _>::copied
Option::<Option<_>>::flatten
Option::<Result<_, _>>::transpose
RefCell::into_inner
Result::as_mut
Result::<&_, _>::copied
Result::<&mut _, _>::copied
Result::<Option<_>, _>::transpose
UnsafeCell::get_mut
UnsafeCell::into_inner
array::from_mut
char::encode_utf8
{float}::classify
{float}::is_finite
{float}::is_infinite
{float}::is_nan
{float}::is_normal
{float}::is_sign_negative
{float}::is_sign_positive
{float}::is_subnormal
{float}::from_bits
{float}::from_be_bytes
{float}::from_le_bytes
{float}::from_ne_bytes
{float}::to_bits
{float}::to_be_bytes
{float}::to_le_bytes
{float}::to_ne_bytes
mem::replace
ptr::replace
ptr::slice_from_raw_parts_mut
ptr::write
ptr::write_unaligned
<*const _>::copy_to
<*const _>::copy_to_nonoverlapping
<*mut _>::copy_from
<*mut _>::copy_from_nonoverlapping
<*mut _>::copy_to
<*mut _>::copy_to_nonoverlapping
<*mut _>::write
<*mut _>::write_bytes
<*mut _>::write_unaligned
slice::from_mut
slice::from_raw_parts_mut
<[_]>::first_mut
<[_]>::last_mut
<[_]>::first_chunk_mut
<[_]>::last_chunk_mut
<[_]>::split_at_mut
<[_]>::split_at_mut_checked
<[_]>::split_at_mut_unchecked
<[_]>::split_first_mut
<[_]>::split_last_mut
<[_]>::split_first_chunk_mut
<[_]>::split_last_chunk_mut
str::as_bytes_mut
str::as_mut_ptr
str::from_utf8_unchecked_mut

Cargo

Introduced a new CARGO_MANIFEST_PATH environment variable, similar to CARGO_MANIFEST_DIR but pointing directly to the manifest file.
Added package.autolib to the manifest, allowing [lib] auto-discovery to be disabled.
Declare support level for each crate in Cargo's Charter / crate docs.
Declare new Intentional Artifacts as 'small' changes.

Rustdoc

The sidebar / hamburger menu table of contents now includes the # headers from the main item's doc comment. This is similar to a third-party feature provided by the rustdoc-search-enhancements browser extension.

Compatibility Notes

Warn against function pointers using unsupported ABI strings.
Check well-formedness of the source type's signature in fn pointer casts. This partly closes a soundness hole that comes when casting a function item to function pointer
Use equality instead of subtyping when resolving type dependent paths.
Linking on macOS now correctly includes Rust's default deployment target. Due to a linker bug, you might have to pass MACOSX_DEPLOYMENT_TARGET or fix your #[link] attributes to point to the correct frameworks. See #129369.
Rust will now correctly raise an error for repr(Rust) written on non-struct/enum/union items, since it previous did not have any effect.
The future incompatibility lint deprecated_cfg_attr_crate_type_name has been made into a hard error. It was used to deny usage of #![crate_type] and #![crate_name] attributes in #![cfg_attr], which required a hack in the compiler to be able to change the used crate type and crate name after cfg expansion. Users can use --crate-type instead of #![cfg_attr(..., crate_type = "...")] and --crate-name instead of #![cfg_attr(..., crate_name = "...")] when running rustc/cargo rustc on the command line. Use of those two attributes outside of #![cfg_attr] continue to be fully supported.

Until now, paths into the sysroot were always prefixed with /rustc/$hash in diagnostics, codegen, backtrace, e.g.

thread 'main' panicked at 'hello world', map-panic.rs:2:50
stack backtrace:
   0: std::panicking::begin_panic
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:616:12
   1: map_panic::main::{{closure}}
             at ./map-panic.rs:2:50
   2: core::option::Option<T>::map
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/option.rs:929:29
   3: map_panic::main
             at ./map-panic.rs:2:30
   4: core::ops::function::FnOnce::call_once
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/ops/function.rs:248:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

RFC 3127 said

We want to change this behaviour such that, when rust-src source files can be discovered, the virtual path is discarded and therefore the local path will be embedded, unless there is a --remap-path-prefix that causes this local path to be remapped in the usual way.

#129687 implements this behaviour, when rust-src is present at compile time, rustc replaces /rustc/$hash with a real path into the local rust-src component with best effort. To sanitize this, users must explicitly supply --remap-path-prefix=<path to rust-src>=foo or not have the rust-src component installed.

The allow-by-default missing_docs lint used to disable itself when invoked through rustc --test/cargo test, resulting in #[expect(missing_docs)] emitting false positives due to the expectation being wrongly unfulfilled. This behavior has now been removed, which allows #[expect(missing_docs)] to be fulfilled in all scenarios, but will also report new missing_docs diagnostics for publicly reachable #[cfg(test)] items, integration test crate-level documentation, and publicly reachable items in integration tests.
The armv8r-none-eabihf target now uses the Armv8-R required set of floating-point features.
Fix a soundness bug where rustc wouldn't detect unconstrained higher-ranked lifetimes in a dyn Trait's associated types that occur due to supertraits.
Update the minimum external LLVM version to 18.
Remove aarch64-fuchsia and x86_64-fuchsia target aliases in favor of aarch64-unknown-fuchsia and x86_64-unknown-fuchsia respectively.
The ABI-level exception class of a Rust panic is now encoded with native-endian bytes, so it is legible in hex dumps.
Visual Studio 2013 is no longer supported for MSVC targets.
The sysroot no longer contains the std dynamic library in its top-level lib/ dir.

Version 1.82.0 (2024-10-17)

Language

Don't make statement nonterminals match pattern nonterminals
Patterns matching empty types can now be omitted in common cases
Enforce supertrait outlives obligations when using trait impls
addr_of(_mut)! macros and the newly stabilized &raw (const|mut) are now safe to use with all static items
size_of_val_raw: for length 0 this is safe to call
Reorder trait bound modifiers after for<...> binder in trait bounds
Stabilize + use<'lt> opaque type precise capturing (RFC 3617)
Stabilize &raw const and &raw mut operators (RFC 2582)
Stabilize unsafe extern blocks (RFC 3484)
Stabilize nested field access in offset_of!
Do not require T to be live when dropping [T; 0]
Stabilize const operands in inline assembly
Stabilize floating-point arithmetic in const fn
Stabilize explicit opt-in to unsafe attributes
Document NaN bit patterns guarantees

Compiler

Promote riscv64gc-unknown-linux-musl to tier 2
Promote Mac Catalyst targets aarch64-apple-ios-macabi and x86_64-apple-ios-macabi to Tier 2, and ship them with rustup
Add tier 3 NuttX based targets for RISC-V and ARM
Add tier 3 powerpc-unknown-linux-muslspe target
Improved diagnostics to explain why a pattern is unreachable
The compiler now triggers the unreachable code warning properly for async functions that don't return/are -> !
Promote aarch64-apple-darwin to Tier 1
Add Trusty OS target aarch64-unknown-trusty and armv7-unknown-trusty as tier 3 targets
Promote wasm32-wasip2 to Tier 2.

Libraries

Generalize {Rc,Arc}::make_mut() to Path, OsStr, and CStr.

Stabilized APIs

std::thread::Builder::spawn_unchecked
std::str::CharIndices::offset
std::option::Option::is_none_or
[T]::is_sorted
[T]::is_sorted_by
[T]::is_sorted_by_key
Iterator::is_sorted
Iterator::is_sorted_by
Iterator::is_sorted_by_key
std::future::Ready::into_inner
std::iter::repeat_n
impl<T: Clone> DoubleEndedIterator for Take<Repeat<T>>
impl<T: Clone> ExactSizeIterator for Take<Repeat<T>>
impl<T: Clone> ExactSizeIterator for Take<RepeatWith<T>>
impl Default for std::collections::binary_heap::Iter
impl Default for std::collections::btree_map::RangeMut
impl Default for std::collections::btree_map::ValuesMut
impl Default for std::collections::vec_deque::Iter
impl Default for std::collections::vec_deque::IterMut
Rc<T>::new_uninit
Rc<MaybeUninit<T>>::assume_init
Rc<[T]>::new_uninit_slice
Rc<[MaybeUninit<T>]>::assume_init
Arc<T>::new_uninit
Arc<MaybeUninit<T>>::assume_init
Arc<[T]>::new_uninit_slice
Arc<[MaybeUninit<T>]>::assume_init
Box<T>::new_uninit
Box<MaybeUninit<T>>::assume_init
Box<[T]>::new_uninit_slice
Box<[MaybeUninit<T>]>::assume_init
core::arch::x86_64::_bextri_u64
core::arch::x86_64::_bextri_u32
core::arch::x86::_mm_broadcastsi128_si256
core::arch::x86::_mm256_stream_load_si256
core::arch::x86::_tzcnt_u16
core::arch::x86::_mm_extracti_si64
core::arch::x86::_mm_inserti_si64
core::arch::x86::_mm_storeu_si16
core::arch::x86::_mm_storeu_si32
core::arch::x86::_mm_storeu_si64
core::arch::x86::_mm_loadu_si16
core::arch::x86::_mm_loadu_si32
core::arch::wasm32::u8x16_relaxed_swizzle
core::arch::wasm32::i8x16_relaxed_swizzle
core::arch::wasm32::i32x4_relaxed_trunc_f32x4
core::arch::wasm32::u32x4_relaxed_trunc_f32x4
core::arch::wasm32::i32x4_relaxed_trunc_f64x2_zero
core::arch::wasm32::u32x4_relaxed_trunc_f64x2_zero
core::arch::wasm32::f32x4_relaxed_madd
core::arch::wasm32::f32x4_relaxed_nmadd
core::arch::wasm32::f64x2_relaxed_madd
core::arch::wasm32::f64x2_relaxed_nmadd
core::arch::wasm32::i8x16_relaxed_laneselect
core::arch::wasm32::u8x16_relaxed_laneselect
core::arch::wasm32::i16x8_relaxed_laneselect
core::arch::wasm32::u16x8_relaxed_laneselect
core::arch::wasm32::i32x4_relaxed_laneselect
core::arch::wasm32::u32x4_relaxed_laneselect
core::arch::wasm32::i64x2_relaxed_laneselect
core::arch::wasm32::u64x2_relaxed_laneselect
core::arch::wasm32::f32x4_relaxed_min
core::arch::wasm32::f32x4_relaxed_max
core::arch::wasm32::f64x2_relaxed_min
core::arch::wasm32::f64x2_relaxed_max
core::arch::wasm32::i16x8_relaxed_q15mulr
core::arch::wasm32::u16x8_relaxed_q15mulr
core::arch::wasm32::i16x8_relaxed_dot_i8x16_i7x16
core::arch::wasm32::u16x8_relaxed_dot_i8x16_i7x16
core::arch::wasm32::i32x4_relaxed_dot_i8x16_i7x16_add
core::arch::wasm32::u32x4_relaxed_dot_i8x16_i7x16_add

These APIs are now stable in const contexts:

std::task::Waker::from_raw
std::task::Context::from_waker
std::task::Context::waker
{integer}::from_str_radix
std::num::ParseIntError::kind

Cargo

feat: Add info cargo subcommand

Compatibility Notes

We now disallow setting some built-in cfgs via the command-line with the newly added explicit_builtin_cfgs_in_flags lint in order to prevent incoherent state, eg. windows cfg active but target is Linux based. The appropriate rustc flag should be used instead.
The standard library has a new implementation of binary_search which is significantly improves performance (#128254). However when a sorted slice has multiple values which compare equal, the new implementation may select a different value among the equal ones than the old implementation.
illumos/Solaris now sets MSG_NOSIGNAL when writing to sockets. This avoids killing the process with SIGPIPE when writing to a closed socket, which matches the existing behavior on other UNIX targets.
Removes a problematic hack that always passed the --whole-archive linker flag for tests, which may cause linker errors for code accidentally relying on it.
The WebAssembly target features multivalue and reference-types are now both enabled by default. These two features both have subtle changes implied for generated WebAssembly binaries. For the multivalue feature, WebAssembly target support has changed when upgrading to LLVM 19. Support for generating functions with multiple returns no longer works and -Ctarget-feature=+multivalue has a different meaning than it did in LLVM 18 and prior. There is no longer any supported means to generate a module that has a function with multiple returns in WebAssembly from Rust source code. For the reference-types feature the encoding of immediates in the call_indirect, a commonly used instruction by the WebAssembly backend, has changed. Validators and parsers which don't understand the reference-types proposal will no longer accept modules produced by LLVM due to this change in encoding of immediates. Additionally these features being enabled are encoded in the target_features custom section and may affect downstream tooling such as wasm-opt consuming the module. Generating a WebAssembly module that disables default features requires -Zbuild-std support from Cargo and more information can be found at rust-lang/rust#128511.
Rust now raises unsafety errors for union patterns in parameter-position

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Update to LLVM 19

Version 1.81.0 (2024-09-05)

Language

Abort on uncaught panics in extern "C" functions.
Fix ambiguous cases of multiple & in elided self lifetimes.
Stabilize #[expect] for lints (RFC 2383), like #[allow] with a warning if the lint is not fulfilled.
Change method resolution to constrain hidden types instead of rejecting method candidates.
Bump elided_lifetimes_in_associated_constant to deny.
offset_from: always allow pointers to point to the same address.
Allow constraining opaque types during subtyping in the trait system.
Allow constraining opaque types during various unsizing casts.
Deny keyword lifetimes pre-expansion.

Compiler

Make casts of pointers to trait objects stricter.
Check alias args for well-formedness even if they have escaping bound vars.
Deprecate no-op codegen option -Cinline-threshold=....
Re-implement a type-size based limit.
Properly account for alignment in transmute size checks.
Remove the box_pointers lint.
Ensure the interpreter checks bool/char for validity when they are used in a cast.
Improve coverage instrumentation for functions containing nested items.
Target changes:
- Add Tier 3 no_std Xtensa targets: xtensa-esp32-none-elf, xtensa-esp32s2-none-elf, xtensa-esp32s3-none-elf
- Add Tier 3 std Xtensa targets: xtensa-esp32-espidf, xtensa-esp32s2-espidf, xtensa-esp32s3-espidf
- Add Tier 3 i686 Redox OS target: i686-unknown-redox
- Promote arm64ec-pc-windows-msvc to Tier 2.
- Promote loongarch64-unknown-linux-musl to Tier 2 with host tools.
- Enable full tools and profiler for LoongArch Linux targets.
- Unconditionally warn on usage of wasm32-wasi. (see compatibility note below)
- Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

Split core's PanicInfo and std's PanicInfo. (see compatibility note below)
Generalize {Rc,Arc}::make_mut() to unsized types.
Replace sort implementations with stable 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.
Document behavior of create_dir_all with respect to empty paths.
Fix interleaved output in the default panic hook when multiple threads panic simultaneously.
Fix Command's batch files argument escaping not working when file name has trailing whitespace or periods (CVE-2024-43402).

Stabilized APIs

core::error
hint::assert_unchecked
fs::exists
AtomicBool::fetch_not
Duration::abs_diff
IoSlice::advance
IoSlice::advance_slices
IoSliceMut::advance
IoSliceMut::advance_slices
PanicHookInfo
PanicInfo::message
PanicMessage

These APIs are now stable in const contexts:

char::from_u32_unchecked (function)
char::from_u32_unchecked (method)
CStr::count_bytes
CStr::from_ptr

Cargo

Generated .cargo_vcs_info.json is always included, even when --allow-dirty is passed.
Disallow package.license-file and package.readme pointing to non-existent files during packaging.
Disallow passing --release/--debug flag along with the --profile flag.
Remove lib.plugin key support in Cargo.toml. Rust plugin support has been deprecated for four years and was removed in 1.75.0.

Compatibility Notes

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.
In very rare cases, a change in the internal evaluation order of the trait solver may result in new fatal overflow errors.

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Add a Rust-for Linux auto CI job to check kernel builds.

Version 1.80.1 (2024-08-08)

Fix miscompilation in the jump threading MIR optimization when comparing floats
Revert changes to the dead_code lint from 1.80.0

Version 1.80.0 (2024-07-25)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

<[T]>::last_chunk
BinaryHeap::new

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.79.0 (2024-06-13)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Misc

Compatibility Notes

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

Version 1.78.0 (2024-05-02)

Language

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

Compiler

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

Target changes:

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

Barrier::new()

Cargo

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.77.2 (2024-04-09)

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

Version 1.77.1 (2024-03-28)

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

Version 1.77.0 (2024-03-21)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Rustdoc

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

Misc

Recommend version-sorting for all sorting in style guide.

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Add more weirdness to weird-exprs.rs.

Version 1.76.0 (2024-02-08)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

See Cargo release notes.

Rustdoc

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

Compatibility Notes

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

Version 1.75.0 (2023-12-28)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.74.1 (2023-12-07)

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

Version 1.74.0 (2023-11-16)

Language

Codify that std::mem::Discriminant<T> does not depend on any lifetimes in T
Replace private_in_public lint with private_interfaces and private_bounds per RFC 2145. Read more in RFC 2145.
Allow explicit #[repr(Rust)]
closure field capturing: don't depend on alignment of packed fields
Enable MIR-based drop-tracking for async blocks
Stabilize impl_trait_projections

Compiler

stabilize combining +bundle and +whole-archive link modifiers
Stabilize PATH option for --print KIND=PATH
Enable ASAN/LSAN/TSAN for *-apple-ios-macabi
Promote loongarch64-unknown-none* to Tier 2
Add i686-pc-windows-gnullvm as a tier 3 target

Libraries

Implement From<OwnedFd/Handle> for ChildStdin/out/err
Implement From<{&,&mut} [T; N]> for Vec<T> where T: Clone
impl Step for IP addresses
Implement From<[T; N]> for Rc<[T]> and Arc<[T]>
impl TryFrom<char> for u16
Stabilize io_error_other feature
Stabilize the Saturating type
Stabilize const_transmute_copy

Stabilized APIs

core::num::Saturating
impl From<io::Stdout> for std::process::Stdio
impl From<io::Stderr> for std::process::Stdio
impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}
impl From<OwnedFd> for std::process::Child{Stdin, Stdout, Stderr}
std::ffi::OsString::from_encoded_bytes_unchecked
std::ffi::OsString::into_encoded_bytes
std::ffi::OsStr::from_encoded_bytes_unchecked
std::ffi::OsStr::as_encoded_bytes
std::io::Error::other
impl TryFrom<char> for u16
impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T>
impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T>
impl<T, const N: usize> From<[T; N]> for Arc<[T]>
impl<T, const N: usize> From<[T; N]> for Rc<[T]>

These APIs are now stable in const contexts:

core::mem::transmute_copy
str::is_ascii
[u8]::is_ascii

Cargo

In Cargo.toml, stabilize [lints]
Stabilize credential-process and registry-auth
Stabilize --keep-going build flag
Add styling to --help output
For cargo clean, add --dry-run flag and summary line at the end
For cargo update, make --package more convenient by being positional
For cargo update, clarify meaning of --aggressive as --recursive
Add '-n' as an alias for --dry-run
Allow version-prefixes in pkgid's (e.g. --package flags) to resolve ambiguities
In .cargo/config.toml, merge lists in precedence order
Add support for target.'cfg(..)'.linker

Rustdoc

Add warning block support in rustdoc
rustdoc-search: add support for type parameters
rustdoc: show inner enum and struct in type definition for concrete type

Compatibility Notes

Raise minimum supported Apple OS versions
make Cell::swap panic if the Cells partially overlap
Reject invalid crate names in --extern
Don't resolve generic impls that may be shadowed by dyn built-in impls
The new impl From<{&,&mut} [T; N]> for Vec<T> is known to cause some inference failures with overly-generic code. In those examples using the tui crate, the combination of AsRef<_> and Into<Vec> leaves the middle type ambiguous, and the new impl adds another possibility, so it now requires an explicit type annotation.

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

None this cycle.

Version 1.73.0 (2023-10-05)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Misc

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.72.1 (2023-09-19)

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

Version 1.72.0 (2023-08-24)

Language

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

Compiler

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

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

Libraries

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

Rustdoc

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Compatibility Notes

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

Version 1.71.1 (2023-08-03)

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

Version 1.71.0 (2023-07-13)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Misc

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Version 1.70.0 (2023-06-01)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Misc

Stabilize rustdoc --test-run-directory

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.69.0 (2023-04-20)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

CStr::from_bytes_until_nul
core::ffi::FromBytesUntilNulError

These APIs are now stable in const contexts:

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.68.2 (2023-03-28)

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

Version 1.68.1 (2023-03-23)

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

Version 1.68.0 (2023-03-09)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

VecDeque::new

Cargo

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

Misc

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.67.1 (2023-02-09)

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

Version 1.67.0 (2023-01-26)

Language

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

Compiler

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

Added, updated, and removed targets:

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

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Rewrite LLVM's archive writer in Rust.

Version 1.66.1 (2023-01-10)

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

Version 1.66.0 (2022-12-15)

Language

Permit specifying explicit discriminants on all repr(Int) enums

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

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

Compiler

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

Libraries

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

Stabilized APIs

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

Rustdoc

Add Rustdoc warning for invalid HTML tags in the documentation

Cargo

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

See detailed release notes for more.

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Enable BOLT for LLVM compilation
Enable LTO for rustc_driver.so

Version 1.65.0 (2022-11-03)

Language

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

Compiler

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

New targets:

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

Libraries

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

Stabilized APIs

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

These APIs are now stable in const contexts:

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

Cargo

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

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

Version 1.64.0 (2022-09-22)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

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

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

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

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

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

These APIs are now usable in const contexts:

slice::from_raw_parts

Cargo

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

Misc

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

Compatibility Notes

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

Internal Changes

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

Windows builds now use profile-guided optimization, providing 10-20% improvements to compiler performance: Utilize PGO for windows x64 rustc dist builds
Stop keeping metadata in memory before writing it to disk
compiletest: strip debuginfo by default for mode=ui
Many improvements to generated code for derives, including performance improvements:
Bump to clap 3
fully move dropck to mir
Optimize Vec::insert for the case where index == len.
Convert rust-analyzer to an in-tree tool

Version 1.63.0 (2022-08-11)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

These APIs are now usable in const contexts:

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

Cargo

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

Compatibility Notes

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

Internal Changes

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

Prepare Rust for LLVM opaque pointers.

Version 1.62.1 (2022-07-19)

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

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

Version 1.62.0 (2022-06-30)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Clippy

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

Cargo

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

Compatibility Notes

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

Internal Changes

Unify ReentrantMutex implementations across all platforms

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

Version 1.61.0 (2022-05-19)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

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

These APIs are now usable in const contexts:

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

Cargo

No feature changes, but see compatibility notes.

Compatibility Notes

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

Internal Changes

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

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

Version 1.60.0 (2022-04-07)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Misc

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

Compatibility Notes

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

Internal Changes

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

Switch all libraries to the 2021 edition

Version 1.59.0 (2022-02-24)

Language

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

Compiler

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

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

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

See 94124 for more details.

Libraries

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

Stabilized APIs

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

Const-stable:

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

Cargo

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

Compatibility Notes

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

Internal Changes

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

Fix many cases of normalization-related ICEs
Replace dominators algorithm with simple Lengauer-Tarjan
Store liveness in interval sets for region inference
Remove in_band_lifetimes from the compiler and standard library, in preparation for removing this unstable feature.

Version 1.58.1 (2022-01-20)

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

Version 1.58.0 (2022-01-13)

Language

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

Compiler

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

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

Libraries

All remaining functions in the standard library have #[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.
Paths are automatically canonicalized on Windows for operations that support it
Re-enable debug checks for copy and copy_nonoverlapping
Implement RefUnwindSafe for Rc<T>
Make RSplit<T, P>: Clone not require T: Clone
Implement Termination for Result<Infallible, E>. This allows writing fn main() -> Result<Infallible, ErrorType>, for a program whose successful exits never involve returning from main (for instance, a program that calls exit, or that uses exec to run another program).

Stabilized APIs

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

These APIs are now usable in const contexts:

Duration::new
Duration::checked_add
Duration::saturating_add
Duration::checked_sub
Duration::saturating_sub
Duration::checked_mul
Duration::saturating_mul
Duration::checked_div

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Changes

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

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

Version 1.57.0 (2021-12-02)

Language

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

Compiler

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

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

Libraries

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

Stabilised APIs

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

These APIs are now usable in const contexts:

hint::unreachable_unchecked

Cargo

Stabilize custom profiles

Compatibility notes

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

Internal changes

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

Added an experimental backend for codegen with libgccjit.

Version 1.56.1 (2021-11-01)

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

Version 1.56.0 (2021-10-21)

Language

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

Compiler

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

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

Libraries

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

Stabilised APIs

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

These APIs are now usable in const contexts:

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

Cargo

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

Compatibility notes

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

Internal changes

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

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

Version 1.55.0 (2021-09-09)

Language

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

Compiler

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

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

Libraries

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

Stabilised APIs

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

The following previously stable functions are now const.

str::from_utf8_unchecked

Cargo

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

Rustdoc

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

Compatibility Notes

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

Version 1.54.0 (2021-07-29)

Language

You can now use macros for values in some built-in attributes. This primarily allows you to call macros within the #[doc] attribute. For example, to include external documentation in your crate, you can now write the following:
```
#![doc = include_str!("README.md")]
```
You can now cast between unsized slice types (and types which contain unsized slices) in const fn.
You can now use multiple generic lifetimes with impl Trait where the lifetimes don't explicitly outlive another. In code this means that you can now have impl Trait<'a, 'b> where as before you could only have impl Trait<'a, 'b> where 'b: 'a.

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Compatibility Notes

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

Version 1.53.0 (2021-06-17)

Language

You can now use unicode for identifiers. This allows multilingual identifiers but still doesn't allow glyphs that are not considered characters such as ◆ or 🦀. More specifically you can now use any identifier that matches the UAX #31 "Unicode Identifier and Pattern Syntax" standard. This is the same standard as languages like Python, however Rust uses NFC normalization which may be different from other languages.
You can now specify "or patterns" inside pattern matches. Previously you could only use | (OR) on complete patterns. E.g.
```
let x = Some(2u8);
// Before
matches!(x, Some(1) | Some(2));
// Now
matches!(x, Some(1 | 2));
```
Added the :pat_param macro_rules! matcher. This matcher has the same semantics as the :pat matcher. This is to allow :pat to change semantics to being a pattern fragment in a future edition.

Compiler

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

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

Libraries

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

Stabilised APIs

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

Cargo

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

Rustdoc

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

Compatibility Notes

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

Internal Only

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

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

Version 1.52.1 (2021-05-10)

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

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

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

See 84970 for more details.

Version 1.52.0 (2021-05-06)

Language

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

Compiler

Upgraded the default LLVM to LLVM 12.

Added tier 3* support for the following targets.

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

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

Libraries

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

Stabilised APIs

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

The following previously stable APIs are now const.

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

Rustdoc

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

Misc

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

Internal Only

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

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

Compatibility Notes

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

Version 1.51.0 (2021-03-25)

Language

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

struct GenericArray<T, const LENGTH: usize> {
    inner: [T; LENGTH]
}

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Rustdoc

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

Various improvements to intra-doc links:

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

Misc

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

Compatibility Notes

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

Internal Only

Consistently avoid constructing optimized MIR when not doing codegen

Version 1.50.0 (2021-02-11)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

The following previously stable methods are now const.

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

Cargo

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

Misc

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

Compatibility Notes

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

Version 1.49.0 (2020-12-31)

Language

Unions can now implement Drop, and you can now have a field in a union with ManuallyDrop<T>.
You can now cast uninhabited enums to integers.

You can now bind by reference and by move in patterns. This allows you to selectively borrow individual components of a type. E.g.

#[derive(Debug)]
struct Person {
    name: String,
    age: u8,
}

let person = Person {
    name: String::from("Alice"),
    age: 20,
};

// `name` is moved out of person, but `age` is referenced.
let Person { name, ref age } = person;
println!("{} {}", name, age);

Compiler

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

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

Libraries

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

Stabilized APIs

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

The following previously stable methods are now const.

Poll::is_ready
Poll::is_pending

Cargo

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

Compatibility Notes

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

Internal Only

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

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

Version 1.48.0 (2020-11-19)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

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

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

Cargo

Rustdoc

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

Compatibility Notes

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

Internal Only

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

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

Version 1.47.0 (2020-10-08)

Language

Closures will now warn when not used.

Compiler

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

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

Libraries

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

Stabilized APIs

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

The following previously stable APIs have now been made const.

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

Cargo

build-dependencies are now built with opt-level 0 by default. You can override this by setting the following in your Cargo.toml.
```
[profile.release.build-override]
opt-level = 3
```
cargo-help will now display man pages for commands rather just the --help text.
cargo-metadata now emits a test field indicating if a target has tests enabled.
workspace.default-members now respects workspace.exclude.
cargo-publish will now use an alternative registry by default if it's the only registry specified in package.publish.

Misc

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

Compatibility Notes

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

Internal Only

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

Version 1.46.0 (2020-08-27)

Language

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

Compiler

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

Libraries

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

Stabilized APIs

Option::zip
vec::Drain::as_slice

Cargo

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

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

Compatibility Notes

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

Version 1.45.2 (2020-08-03)

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

Version 1.45.1 (2020-07-30)

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

Version 1.45.0 (2020-07-16)

Language

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

Compiler

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

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

Libraries

net::{SocketAddr, SocketAddrV4, SocketAddrV6} now implements PartialOrd and Ord.
proc_macro::TokenStream now implements Default.
You can now use char with ops::{Range, RangeFrom, RangeFull, RangeInclusive, RangeTo} to iterate over a range of codepoints. E.g. you can now write the following;
```
for ch in 'a'..='z' {
    print!("{}", ch);
}
println!();
// Prints "abcdefghijklmnopqrstuvwxyz"
```
OsString now implements FromStr.
The saturating_neg method has been added to all signed integer primitive types, and the saturating_abs method has been added for all integer primitive types.
Arc<T>, Rc<T> now implement From<Cow<'_, T>>, and Box now implements From<Cow> when T is [T: Copy], str, CStr, OsStr, or Path.
Box<[T]> now implements From<[T; N]>.
BitOr and BitOrAssign are implemented for all NonZero integer types.
The fetch_min, and fetch_max methods have been added to all atomic integer types.
The fetch_update method has been added to all atomic integer types.

Stabilized APIs

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

Cargo

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

Misc

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

Compatibility Notes

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

Internals Only

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

Version 1.44.1 (2020-06-18)

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

Version 1.44.0 (2020-06-04)

Language

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

Syntax-only changes

Expansion-driven outline module parsing

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

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

Compiler

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

Libraries

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

Stabilized APIs

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

Cargo

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

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

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

Misc

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

Compatibility Notes

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

Internal Only

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

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

Version 1.43.1 (2020-05-07)

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

Version 1.43.0 (2020-04-23)

Language

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

Syntax only changes

Allow type Foo: Ord syntactically.
Fuse associated and extern items up to defaultness.
Syntactically allow self in all fn contexts.
Merge fn syntax + cleanup item parsing.

item macro fragments can be interpolated into traits, impls, and extern blocks. For example, you may now write:

macro_rules! mac_trait {
    ($i:item) => {
        trait T { $i }
    }
}
mac_trait! {
    fn foo() {}
}

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

Compiler

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

Libraries

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

Stabilized APIs

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

Cargo

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

Misc

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

Compatibility Notes

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

Internal Only

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

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

Version 1.42.0 (2020-03-12)

Language

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

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

You can now use #[repr(transparent)] on univariant enums. Meaning that you can create an enum that has the exact layout and ABI of the type it contains.
You can now use outer attribute procedural macros on inline modules.
There are some syntax-only changes:
- default is syntactically allowed before items in trait definitions.
- Items in impls (i.e. consts, types, and fns) may syntactically leave out their bodies in favor of ;.
- Bounds on associated types in impls are now syntactically allowed (e.g. type Foo: Ord;).
- ... (the C-variadic type) may occur syntactically directly as the type of any function parameter.
These are still rejected semantically, so you will likely receive an error but these changes can be seen and parsed by procedural macros and conditional compilation.

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Compatibility Notes

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

Version 1.41.1 (2020-02-27)

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

Version 1.41.0 (2020-01-30)

Language

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

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Misc

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

Compatibility Notes

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

Version 1.40.0 (2019-12-19)

Language

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

pub struct Point(i32, i32);

const ORIGIN: Point = {
    let constructor = Point;

    constructor(0, 0)
};

You can now mark structs, enums, and enum variants with the #[non_exhaustive] attribute to indicate that there may be variants or fields added in the future. For example this requires adding a wild-card branch (_ => {}) to any match statements on a non-exhaustive enum. (RFC 2008)
You can now use function-like procedural macros in extern blocks and in type positions. e.g. type Generated = macro!();
Function-like and attribute procedural macros can now emit macro_rules! items, so you can now have your macros generate macros.
The meta pattern matcher in macro_rules! now correctly matches the modern attribute syntax. For example (#[$m:meta]) now matches #[attr], #[attr{tokens}], #[attr[tokens]], and #[attr(tokens)].

Compiler

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

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

Libraries

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

Stabilized APIs

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

Cargo

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

Misc

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

Compatibility Notes

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

Version 1.39.0 (2019-11-07)

Language

You can now create async functions and blocks with async fn, async move {}, and async {} respectively, and you can now call .await on async expressions.
You can now use certain attributes on function, closure, and function pointer parameters. These attributes include cfg, cfg_attr, allow, warn, deny, forbid as well as inert helper attributes used by procedural macro attributes applied to items. e.g.
```
fn len(
    #[cfg(windows)] slice: &[u16],
    #[cfg(not(windows))] slice: &[u8],
) -> usize {
    slice.len()
}
```

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

fn main() {
    let array: Box<[u8; 4]> = Box::new([1, 2, 3, 4]);

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

Compiler

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

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

Libraries

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

Stabilized APIs

Pin::into_inner
Instant::checked_duration_since
Instant::saturating_duration_since

Cargo

You can now publish git dependencies if supplied with a version.
The --all flag has been renamed to --workspace. Using --all is now deprecated.

Misc

You can now pass -Clinker to rustdoc to control the linker used for compiling doctests.

Compatibility Notes

Code that was previously accepted by the old borrow checker, but rejected by the NLL borrow checker is now a hard error in Rust 2018. This was previously a warning, and will also become a hard error in the Rust 2015 edition in the 1.40.0 release.
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.
The 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.

Version 1.38.0 (2019-09-26)

Language

The #[global_allocator] attribute can now be used in submodules.
The #[deprecated] attribute can now be used on macros.

Compiler

Added pipelined compilation support to rustc. This will improve compilation times in some cases. For further information please refer to the "Evaluating pipelined rustc compilation" thread.
Added tier 3* support for the aarch64-uwp-windows-msvc, i686-uwp-windows-gnu, i686-uwp-windows-msvc, x86_64-uwp-windows-gnu, and x86_64-uwp-windows-msvc targets.
Added tier 3 support for the armv7-unknown-linux-gnueabi and armv7-unknown-linux-musleabi targets.
Added tier 3 support for the hexagon-unknown-linux-musl target.
Added tier 3 support for the riscv32i-unknown-none-elf target.
Upgraded to LLVM 9.

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

Libraries

ascii::EscapeDefault now implements Clone and Display.
Derive macros for prelude traits (e.g. 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>.
Added euclidean remainder and division operations (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.

Stabilized APIs

<*const T>::cast
<*mut T>::cast
Duration::as_secs_f32
Duration::as_secs_f64
Duration::div_f32
Duration::div_f64
Duration::from_secs_f32
Duration::from_secs_f64
Duration::mul_f32
Duration::mul_f64
any::type_name

Cargo

Added pipelined compilation support to cargo.
You can now pass the --features option multiple times to enable multiple features.

Rustdoc

Documentation on pub use statements is prepended to the documentation of the re-exported item

Misc

rustc will now warn about some incorrect uses of mem::{uninitialized, zeroed} that are known to cause undefined behaviour.

Compatibility Notes

The x86_64-unknown-uefi platform can not be built with rustc 1.38.0.
The armv7-unknown-linux-gnueabihf platform is known to have issues with certain crates such as libc.

Version 1.37.0 (2019-08-15)

Language

#[must_use] will now warn if the type is contained in a tuple, Box, or an array and unused.
You can now use the cfg and cfg_attr attributes on generic parameters.

You can now use enum variants through type alias. e.g. You can write the following:

type MyOption = Option<u8>;

fn increment_or_zero(x: MyOption) -> u8 {
    match x {
        MyOption::Some(y) => y + 1,
        MyOption::None => 0,
    }
}

You can now use _ as an identifier for consts. e.g. You can write const _: u32 = 5;.
You can now use #[repr(align(X)] on enums.
The ? Kleene macro operator is now available in the 2015 edition.

Compiler

You can now enable Profile-Guided Optimization with the -C profile-generate and -C profile-use flags. For more information on how to use profile guided optimization, please refer to the rustc book.
The rust-lldb wrapper script should now work again.

Libraries

mem::MaybeUninit<T> is now ABI-compatible with T.

Stabilized APIs

BufReader::buffer
BufWriter::buffer
Cell::from_mut
Cell<[T]>::as_slice_of_cells
DoubleEndedIterator::nth_back
Option::xor
Wrapping::reverse_bits
i128::reverse_bits
i16::reverse_bits
i32::reverse_bits
i64::reverse_bits
i8::reverse_bits
isize::reverse_bits
slice::copy_within
u128::reverse_bits
u16::reverse_bits
u32::reverse_bits
u64::reverse_bits
u8::reverse_bits
usize::reverse_bits

Cargo

Cargo.lock files are now included by default when publishing executable crates with executables.
You can now specify default-run="foo" in [package] to specify the default executable to use for cargo run.

Misc

Compatibility Notes

Using ... for inclusive range patterns will now warn by default. Please transition your code to using the ..= syntax for inclusive ranges instead.
Using a trait object without the dyn will now warn by default. Please transition your code to use dyn Trait for trait objects instead.

Version 1.36.0 (2019-07-04)

Language

Non-Lexical Lifetimes are now enabled on the 2015 edition.
The order of traits in trait objects no longer affects the semantics of that object. e.g. dyn Send + fmt::Debug is now equivalent to dyn fmt::Debug + Send, where this was previously not the case.

Libraries

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.
Both NonNull::{dangling, cast} are now const fns.
The 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>.
You can now pass multiple arguments to the 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.

Stabilized APIs

VecDeque::rotate_left
VecDeque::rotate_right
Iterator::copied
io::IoSlice
io::IoSliceMut
Read::read_vectored
Write::write_vectored
str::as_mut_ptr
mem::MaybeUninit
pointer::align_offset
future::Future
task::Context
task::RawWaker
task::RawWakerVTable
task::Waker
task::Poll

Cargo

Cargo will now produce an error if you attempt to use the name of a required dependency as a feature.
You can now pass the --offline flag to run cargo without accessing the network.

You can find further change's in Cargo's 1.36.0 release notes.

Clippy

There have been numerous additions and fixes to clippy, see Clippy's 1.36.0 release notes for more details.

Misc

Compatibility Notes

With the stabilisation of mem::MaybeUninit, mem::uninitialized use is no longer recommended, and will be deprecated in 1.39.0.

Version 1.35.0 (2019-05-23)

Language

FnOnce, FnMut, and the Fn traits are now implemented for Box<FnOnce>, Box<FnMut>, and Box<Fn> respectively.

You can now coerce closures into unsafe function pointers. e.g.

unsafe fn call_unsafe(func: unsafe fn()) {
    func()
}

pub fn main() {
    unsafe { call_unsafe(|| {}); }
}

Compiler

Added the armv6-unknown-freebsd-gnueabihf and armv7-unknown-freebsd-gnueabihf targets.
Added the wasm32-unknown-wasi target.

Libraries

Thread will now show its ID in Debug output.
StdinLock, StdoutLock, and StderrLock now implement AsRawFd.
alloc::System now implements Default.
Expanded Debug output ({:#?}) for structs now has a trailing comma on the last field.
char::{ToLowercase, ToUppercase} now implement ExactSizeIterator.
All NonZero numeric types now implement FromStr.
Removed the Read trait bounds on the BufReader::{get_ref, get_mut, into_inner} methods.
You can now call the dbg! macro without any parameters to print the file and line where it is called.
In place ASCII case conversions are now up to 4× faster. e.g. str::make_ascii_lowercase
hash_map::{OccupiedEntry, VacantEntry} now implement Sync and Send.

Stabilized APIs

f32::copysign
f64::copysign
RefCell::replace_with
RefCell::map_split
ptr::hash
Range::contains
RangeFrom::contains
RangeTo::contains
RangeInclusive::contains
RangeToInclusive::contains
Option::copied

Cargo

You can now set cargo:rustc-cdylib-link-arg at build time to pass custom linker arguments when building a cdylib. Its usage is highly platform specific.

Misc

The Rust toolchain is now available natively for musl based distros.

Version 1.34.2 (2019-05-14)

Destabilize the Error::type_id function due to a security vulnerability (CVE-2019-12083)

Version 1.34.1 (2019-04-25)

Fix false positives for the redundant_closure Clippy lint
Fix false positives for the missing_const_for_fn Clippy lint
Fix Clippy panic when checking some macros

Version 1.34.0 (2019-04-11)

Language

You can now use #[deprecated = "reason"] as a shorthand for #[deprecated(note = "reason")]. This was previously allowed by mistake but had no effect.
You can now accept token streams in #[attr()],#[attr[]], and #[attr{}] procedural macros.
You can now write extern crate self as foo; to import your crate's root into the extern prelude.

Compiler

You can now target riscv64imac-unknown-none-elf and riscv64gc-unknown-none-elf.
You can now enable linker plugin LTO optimisations with -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.
You can now target powerpc64-unknown-freebsd.

Libraries

The trait bounds have been removed on some of 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.
The 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.
The methods overflowing_neg and wrapping_neg are now const functions for all numeric types.
Indexing a 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.
The methods 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.

Stabilized APIs

std & core

Any::type_id
Error::type_id
atomic::AtomicI16
atomic::AtomicI32
atomic::AtomicI64
atomic::AtomicI8
atomic::AtomicU16
atomic::AtomicU32
atomic::AtomicU64
atomic::AtomicU8
convert::Infallible
convert::TryFrom
convert::TryInto
iter::from_fn
iter::successors
num::NonZeroI128
num::NonZeroI16
num::NonZeroI32
num::NonZeroI64
num::NonZeroI8
num::NonZeroIsize
slice::sort_by_cached_key
str::escape_debug
str::escape_default
str::escape_unicode
str::split_ascii_whitespace

std

Instant::checked_add
Instant::checked_sub
SystemTime::checked_add
SystemTime::checked_sub

Cargo

You can now use alternative registries to crates.io.

Misc

You can now use the ? operator in your documentation tests without manually adding fn main() -> Result<(), _> {}.

Compatibility Notes

Command::before_exec is being replaced by the unsafe method Command::pre_exec and will be deprecated with Rust 1.37.0.
Use of ATOMIC_{BOOL, ISIZE, USIZE}_INIT is now deprecated as you can now use const functions in static variables.

Version 1.33.0 (2019-02-28)

Language

You can now use the cfg(target_vendor) attribute. E.g. #[cfg(target_vendor="apple")] fn main() { println!("Hello Apple!"); }
Integer patterns such as in a match expression can now be exhaustive. E.g. You can have match statement on a u8 that covers 0..=255 and you would no longer be required to have a _ => unreachable!() case.

You can now have multiple patterns in if let and while let expressions. You can do this with the same syntax as a match expression. E.g.

enum Creature {
    Crab(String),
    Lobster(String),
    Person(String),
}

fn main() {
    let state = Creature::Crab("Ferris");

    if let Creature::Crab(name) | Creature::Person(name) = state {
        println!("This creature's name is: {}", name);
    }
}

You can now have irrefutable 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 {}
You can now use let bindings, assignments, expression statements, and irrefutable pattern destructuring in const functions.

You can now call unsafe const functions. E.g.

const unsafe fn foo() -> i32 { 5 }
const fn bar() -> i32 {
    unsafe { foo() }
}

You can now specify multiple attributes in a cfg_attr attribute. E.g. #[cfg_attr(all(), must_use, optimize)]
You can now specify a specific alignment with the #[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.
You can now import an item from a module as an _. This allows you to import a trait's impls, and not have the name in the namespace. E.g.
```
use std::io::Read as _;

// Allowed as there is only one `Read` in the module.
pub trait Read {}
```
You may now use Rc, Arc, and Pin as method receivers.

Compiler

You can now set a linker flavor for rustc with the -Clinker-flavor command line argument.
The minimum required LLVM version has been bumped to 6.0.
Added support for the PowerPC64 architecture on FreeBSD.
The 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.
Added support for the thumbv7neon-linux-androideabi and thumbv7neon-unknown-linux-gnueabihf targets.
Added support for the x86_64-unknown-uefi target.

Libraries

The methods overflowing_{add, sub, mul, shl, shr} are now const functions for all numeric types.
The methods rotate_left, rotate_right, and wrapping_{add, sub, mul, shl, shr} are now const functions for all numeric types.
The methods is_positive and is_negative are now const functions for all signed numeric types.
The get method for all NonZero types is now const.
The methods 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 function

Stabilized APIs

unix::FileExt::read_exact_at
unix::FileExt::write_all_at
Option::transpose
Result::transpose
convert::identity
pin::Pin
marker::Unpin
marker::PhantomPinned
Vec::resize_with
VecDeque::resize_with
Duration::as_millis
Duration::as_micros
Duration::as_nanos

Cargo

You can now publish crates that require a feature flag to compile with cargo publish --features or cargo publish --all-features.
Cargo should now rebuild a crate if a file was modified during the initial build.

Compatibility Notes

The methods 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.
The Error::cause method has been deprecated in favor of Error::source which supports downcasting.
Libtest no longer creates a new thread for each test when --test-threads=1. It also runs the tests in deterministic order

Version 1.32.0 (2019-01-17)

Language

2018 edition

You can now use the ? operator in macro definitions. The ? operator allows you to specify zero or one repetitions similar to the * and + operators.
Module paths with no leading keyword like 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.
```
enum Color { Red, Green, Blue }

use Color::*;
```

All editions

You can now match against PhantomData<T> types.
You can now match against literals in macros with the literal specifier. This will match against a literal of any type. E.g. 1, 'A', "Hello World"

Self can now be used as a constructor and pattern for unit and tuple structs. E.g.

struct Point(i32, i32);

impl Point {
    pub fn new(x: i32, y: i32) -> Self {
        Self(x, y)
    }

    pub fn is_origin(&self) -> bool {
        match self {
            Self(0, 0) => true,
            _ => false,
        }
    }
}

Self can also now be used in type definitions. E.g.

enum List<T>
where
    Self: PartialOrd<Self> // can write `Self` instead of `List<T>`
{
    Nil,
    Cons(T, Box<Self>) // likewise here
}

You can now mark traits with #[must_use]. This provides a warning if a impl Trait or dyn Trait is returned and unused in the program.

Compiler

The default allocator has changed from jemalloc to the default allocator on your system. The compiler itself on Linux & macOS will still use jemalloc, but programs compiled with it will use the system allocator.
Added the aarch64-pc-windows-msvc target.

Libraries

PathBuf now implements FromStr.
Box<[T]> now implements FromIterator<T>.

The dbg! macro has been stabilized. This macro enables you to easily debug expressions in your rust program. E.g.

let a = 2;
let b = dbg!(a * 2) + 1;
//      ^-- prints: [src/main.rs:4] a * 2 = 4
assert_eq!(b, 5);

The following APIs are now const functions and can be used in a const context.

Cell::as_ptr
UnsafeCell::get
char::is_ascii
iter::empty
ManuallyDrop::new
ManuallyDrop::into_inner
RangeInclusive::start
RangeInclusive::end
NonNull::as_ptr
slice::as_ptr
str::as_ptr
Duration::as_secs
Duration::subsec_millis
Duration::subsec_micros
Duration::subsec_nanos
CStr::as_ptr
Ipv4Addr::is_unspecified
Ipv6Addr::new
Ipv6Addr::octets

Stabilized APIs

i8::to_be_bytes
i8::to_le_bytes
i8::to_ne_bytes
i8::from_be_bytes
i8::from_le_bytes
i8::from_ne_bytes
i16::to_be_bytes
i16::to_le_bytes
i16::to_ne_bytes
i16::from_be_bytes
i16::from_le_bytes
i16::from_ne_bytes
i32::to_be_bytes
i32::to_le_bytes
i32::to_ne_bytes
i32::from_be_bytes
i32::from_le_bytes
i32::from_ne_bytes
i64::to_be_bytes
i64::to_le_bytes
i64::to_ne_bytes
i64::from_be_bytes
i64::from_le_bytes
i64::from_ne_bytes
i128::to_be_bytes
i128::to_le_bytes
i128::to_ne_bytes
i128::from_be_bytes
i128::from_le_bytes
i128::from_ne_bytes
isize::to_be_bytes
isize::to_le_bytes
isize::to_ne_bytes
isize::from_be_bytes
isize::from_le_bytes
isize::from_ne_bytes
u8::to_be_bytes
u8::to_le_bytes
u8::to_ne_bytes
u8::from_be_bytes
u8::from_le_bytes
u8::from_ne_bytes
u16::to_be_bytes
u16::to_le_bytes
u16::to_ne_bytes
u16::from_be_bytes
u16::from_le_bytes
u16::from_ne_bytes
u32::to_be_bytes
u32::to_le_bytes
u32::to_ne_bytes
u32::from_be_bytes
u32::from_le_bytes
u32::from_ne_bytes
u64::to_be_bytes
u64::to_le_bytes
u64::to_ne_bytes
u64::from_be_bytes
u64::from_le_bytes
u64::from_ne_bytes
u128::to_be_bytes
u128::to_le_bytes
u128::to_ne_bytes
u128::from_be_bytes
u128::from_le_bytes
u128::from_ne_bytes
usize::to_be_bytes
usize::to_le_bytes
usize::to_ne_bytes
usize::from_be_bytes
usize::from_le_bytes
usize::from_ne_bytes

Cargo

You can now run cargo c as an alias for cargo check.
Usernames are now allowed in alt registry URLs.

Misc

libproc_macro has been added to the rust-src distribution.

Compatibility Notes

The argument types for AVX's _mm256_stream_si256, _mm256_stream_pd, _mm256_stream_ps have been changed from *const to *mut as the previous implementation was unsound.

Version 1.31.1 (2018-12-20)

Fix Rust failing to build on powerpc-unknown-netbsd
Fix broken go-to-definition in RLS
Fix infinite loop on hover in RLS

Version 1.31.0 (2018-12-06)

Language

🎉 This version marks the release of the 2018 edition of Rust. 🎉
New lifetime elision rules now allow for eliding lifetimes in functions and impl headers. E.g. impl<'a> Reader for BufReader<'a> {} can now be impl Reader for BufReader<'_> {}. Lifetimes are still required to be defined in structs.
You can now define and use const functions. These are currently a strict minimal subset of the const fn RFC. Refer to the language reference for what exactly is available.
You can now use tool lints, which allow you to scope lints from external tools using attributes. E.g. #[allow(clippy::filter_map)].
#[no_mangle] and #[export_name] attributes can now be located anywhere in a crate, not just in exported functions.
You can now use parentheses in pattern matches.

Compiler

Updated musl to 1.1.20

Libraries

You can now convert num::NonZero* types to their raw equivalents using the From trait. E.g. u8 now implements From<NonZeroU8>.
You can now convert a &Option<T> into Option<&T> and &mut Option<T> into Option<&mut T> using the From trait.
You can now multiply (*) a time::Duration by a u32.

Stabilized APIs

slice::align_to
slice::align_to_mut
slice::chunks_exact
slice::chunks_exact_mut
slice::rchunks
slice::rchunks_mut
slice::rchunks_exact
slice::rchunks_exact_mut
Option::replace

Cargo

Cargo will now download crates in parallel using HTTP/2.
You can now rename packages in your Cargo.toml We have a guide on how to use the package key in your dependencies.

Version 1.30.1 (2018-11-08)

Fixed overflow ICE in rustdoc
Cap Cargo progress bar width at 60 in MSYS terminals

Version 1.30.0 (2018-10-25)

Language

Procedural macros are now available. These kinds of macros allow for more powerful code generation. There is a new chapter available in the Rust Programming Language book that goes further in depth.
You can now use keywords as identifiers using the raw identifiers syntax (r#), e.g. let r#for = true;
Using anonymous parameters in traits is now deprecated with a warning and will be a hard error in the 2018 edition.
You can now use 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.
Using a external crate no longer requires being prefixed with ::. 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);.
You can now apply the #[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;
You can now import and reexport macros from other crates with the 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.
You can now catch visibility keywords (e.g. pub, pub(crate)) in macros using the vis specifier.
Non-macro attributes now allow all forms of literals, not just strings. Previously, you would write #[attr("true")], and you can now write #[attr(true)].
You can now specify a function to handle a panic in the Rust runtime with the #[panic_handler] attribute.

Compiler

Added the riscv32imc-unknown-none-elf target.
Added the aarch64-unknown-netbsd target
Upgraded to LLVM 8.

Libraries

ManuallyDrop now allows the inner type to be unsized.

Stabilized APIs

Ipv4Addr::BROADCAST
Ipv4Addr::LOCALHOST
Ipv4Addr::UNSPECIFIED
Ipv6Addr::LOCALHOST
Ipv6Addr::UNSPECIFIED
Iterator::find_map

The 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:
str::trim_end_matches
str::trim_end
str::trim_start_matches
str::trim_start

Cargo

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.
Cargo will now provide a progress bar for builds.

Misc

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.
We now distribute a rust-gdbgui script that invokes gdbgui with Rust debug symbols.
Attributes from Rust tools such as rustfmt or clippy are now available, e.g. #[rustfmt::skip] will skip formatting the next item.

Version 1.29.2 (2018-10-11)

Workaround for an aliasing-related LLVM bug, which caused miscompilation.
The rls-preview component on the windows-gnu targets has been restored.

Version 1.29.1 (2018-09-25)

Security Notes

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.

Version 1.29.0 (2018-09-13)

Compiler

Bumped minimum LLVM version to 5.0.
Added powerpc64le-unknown-linux-musl target.
Added aarch64-unknown-hermit and x86_64-unknown-hermit targets.
Upgraded to LLVM 7.

Libraries

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.
Implemented PartialEq<&str> for OsString and PartialEq<OsString> for &str.
Cell<T> now allows T to be unsized.
SocketAddr is now stable on Redox.

Stabilized APIs

Arc::downcast
Iterator::flatten
Rc::downcast

Cargo

Cargo can silently fix some bad lockfiles. You can use --locked to disable this behavior.
cargo-install will now allow you to cross compile an install using --target.
Added the 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.

Misc

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.
A preview of clippy has been made available through rustup. You can install the preview with rustup component add clippy-preview.

Compatibility Notes

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.

Version 1.28.0 (2018-08-02)

Language

The #[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.
The keywords pure, sizeof, alignof, and offsetof have been unreserved and can now be used as identifiers.
The GlobalAlloc trait and #[global_allocator] attribute are now stable. This will allow users to specify a global allocator for their program.
Unit test functions marked with the #[test] attribute can now return Result<(), E: Debug> in addition to ().
The lifetime specifier for macro_rules! is now stable. This allows macros to easily target lifetimes.

Compiler

The 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.
The short error format is now stable. Specified with --error-format=short this option will provide a more compressed output of rust error messages.
Added a lint warning when you have duplicated macro_exports.
Reduced the number of allocations in the macro parser. This can improve compile times of macro heavy crates on average by 5%.

Libraries

Implemented Default for &mut str.
Implemented From<bool> for all integer and unsigned number types.
Implemented Extend for ().
The 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.
Implemented 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.
Implemented 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.
Improved error messages when using format!.

Stabilized APIs

Iterator::step_by
Path::ancestors
SystemTime::UNIX_EPOCH
alloc::GlobalAlloc
alloc::Layout
alloc::LayoutErr
alloc::System
alloc::alloc
alloc::alloc_zeroed
alloc::dealloc
alloc::realloc
alloc::handle_alloc_error
btree_map::Entry::or_default
fmt::Alignment
hash_map::Entry::or_default
iter::repeat_with
num::NonZeroUsize
num::NonZeroU128
num::NonZeroU16
num::NonZeroU32
num::NonZeroU64
num::NonZeroU8
ops::RangeBounds
slice::SliceIndex
slice::from_mut
slice::from_ref
{Any + Send + Sync}::downcast_mut
{Any + Send + Sync}::downcast_ref
{Any + Send + Sync}::is

Cargo

Cargo will now no longer allow you to publish crates with build scripts that modify the src directory. The src directory in a crate should be considered to be immutable.

Misc

The 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.

Compatibility Notes

Rust will consider trait objects with duplicated constraints to be the same type as without the duplicated constraint. For example the below code will now fail to compile.

trait Trait {}

impl Trait + Send {
    fn test(&self) { println!("one"); } //~ ERROR duplicate definitions with name `test`
}

impl Trait + Send + Send {
    fn test(&self) { println!("two"); }
}

Version 1.27.2 (2018-07-20)

Compatibility Notes

The borrow checker was fixed to avoid potential unsoundness when using match ergonomics: #52213.

Version 1.27.1 (2018-07-10)

Security Notes

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.

Compatibility Notes

The borrow checker was fixed to avoid an additional potential unsoundness when using match ergonomics: #51415, #49534.

Version 1.27.0 (2018-06-21)

Language

Removed 'proc' from the reserved keywords list. This allows proc to be used as an identifier.
The dyn syntax is now available. This syntax is equivalent to the bare 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>.
Attributes on generic parameters such as types and lifetimes are now stable. e.g. fn foo<#[lifetime_attr] 'a, #[type_attr] T: 'a>() {}
The #[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.

Compiler

Added the armv5te-unknown-linux-musleabi target.

Libraries

SIMD (Single Instruction Multiple Data) on x86/x86_64 is now stable. This includes 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.
A lot of methods for [u8], f32, and f64 previously only available in std are now available in core.
The generic 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.

Stabilized APIs

DoubleEndedIterator::rfind
DoubleEndedIterator::rfold
DoubleEndedIterator::try_rfold
Duration::from_micros
Duration::from_nanos
Duration::subsec_micros
Duration::subsec_millis
HashMap::remove_entry
Iterator::try_fold
Iterator::try_for_each
NonNull::cast
Option::filter
String::replace_range
Take::set_limit
hint::unreachable_unchecked
os::unix::process::parent_id
ptr::swap_nonoverlapping
slice::rsplit_mut
slice::rsplit
slice::swap_with_slice

Cargo

cargo-metadata now includes authors, categories, keywords, readme, and repository fields.
cargo-metadata now includes a package's metadata table.
Added the --target-dir optional argument. This allows you to specify a different directory than target for placing compilation artifacts.
Cargo will be adding automatic target inference for binaries, benchmarks, examples, and tests in the Rust 2018 edition. If your project specifies specific targets, e.g. using [[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 will now cache compiler information. This can be disabled by setting CARGO_CACHE_RUSTC_INFO=0 in your environment.

Misc

Added “The Rustc book” into the official documentation. “The Rustc book” documents and teaches how to use the rustc compiler.
All books available on doc.rust-lang.org are now searchable.

Compatibility Notes

Calling a 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).
The maximum number for 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.
The .description() method on the std::error::Error trait has been soft-deprecated. It is no longer required to implement it.

Version 1.26.2 (2018-06-05)

Compatibility Notes

The borrow checker was fixed to avoid unsoundness when using match ergonomics.

Version 1.26.1 (2018-05-29)

Tools

RLS now works on Windows.
Rustfmt stopped badly formatting text in some cases.

Compatibility Notes

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.
Prohibit using turbofish for impl Trait in method arguments.

Version 1.26.0 (2018-05-10)

Language

Closures now implement Copy and/or Clone if all captured variables implement either or both traits.
The inclusive range syntax e.g. for x in 0..=10 is now stable.
The '_ 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>).
Pattern matching will now automatically apply dereferences.
128-bit integers in the form of u128 and i128 are now stable.
main can now return Result<(), E: Debug> in addition to ().
A lot of operations are now available in a const context. E.g. You can now index into constant arrays, reference and dereference into constants, and use tuple struct constructors.

Fixed entry slice patterns are now stable. E.g.

let points = [1, 2, 3, 4];
match points {
    [1, 2, 3, 4] => println!("All points were sequential."),
    _ => println!("Not all points were sequential."),
}

Compiler

LLD is now used as the default linker for wasm32-unknown-unknown.
Fixed exponential projection complexity on nested types. This can provide up to a ~12% reduction in compile times for certain crates.
Added the --remap-path-prefix option to rustc. Allowing you to remap path prefixes outputted by the compiler.
Added powerpc-unknown-netbsd target.

Libraries

Implemented From<u16> for usize & From<{u8, i16}> for isize.
Added hexadecimal formatting for integers with fmt::Debug e.g. assert!(format!("{:02x?}", b"Foo\0") == "[46, 6f, 6f, 00]")
Implemented Default, Hash for cmp::Reverse.
Optimized str::repeat being 8x faster in large cases.
ascii::escape_default is now available in libcore.
Trailing commas are now supported in std and core macros.
Implemented Copy, Clone for cmp::Reverse
Implemented Clone for char::{ToLowercase, ToUppercase}.

Stabilized APIs

*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::write
Box::leak
FromUtf8Error::as_bytes
LocalKey::try_with
Option::cloned
btree_map::Entry::and_modify
fs::read_to_string
fs::read
fs::write
hash_map::Entry::and_modify
iter::FusedIterator
ops::RangeInclusive
ops::RangeToInclusive
process::id
slice::rotate_left
slice::rotate_right
String::retain

Cargo

Cargo will now output path to custom commands when -v is passed with --list
The Cargo binary version is now the same as the Rust version

Misc

The second edition of "The Rust Programming Language" book is now recommended over the first.

Compatibility Notes

aliasing a Fn trait as dyn no longer works. E.g. the following syntax is now invalid.
```
use std::ops::Fn as dyn;
fn g(_: Box<dyn(std::fmt::Debug)>) {}
```

The result of dereferences are no longer promoted to 'static. e.g.

fn main() {
    const PAIR: &(i32, i32) = &(0, 1);
    let _reversed_pair: &'static _ = &(PAIR.1, PAIR.0); // Doesn't work
}

Deprecate AsciiExt trait in favor of inherent methods.
".e0" will now no longer parse as 0.0 and will instead cause an error.
Removed hoedown from rustdoc.
Bounds on higher-kinded lifetimes a hard error.

Version 1.25.0 (2018-03-29)

Language

The #[repr(align(x))] attribute is now stable. RFC 1358
You can now use nested groups of imports. e.g. use std::{fs::File, io::Read, path::{Path, PathBuf}};
You can now have | 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"),
    }
}

Compiler

Upgraded to LLVM 6.
Added -C lto=val option.
Added i586-unknown-linux-musl target

Libraries

Impl Send for process::Command on Unix.
Impl PartialEq and Eq for ParseCharError.
UnsafeCell::into_inner is now safe.
Implement libstd for CloudABI.
Float::{from_bits, to_bits} is now available in libcore.
Implement AsRef<Path> for Component
Implemented Write for Cursor<&mut Vec<u8>>
Moved Duration to libcore.

Stabilized APIs

Location::column
ptr::NonNull

The following functions can now be used in a constant expression. eg. static MINUTE: Duration = Duration::from_secs(60);

Duration::new
Duration::from_secs
Duration::from_millis

Cargo

cargo new no longer removes rust or rs prefixes/suffixes.
cargo new now defaults to creating a binary crate, instead of a library crate.

Misc

Rust by example is now shipped with new releases

Compatibility Notes

Deprecated net::lookup_host.
rustdoc has switched to pulldown as the default markdown renderer.
The borrow checker was sometimes incorrectly permitting overlapping borrows around indexing operations (see #47349). This has been fixed (which also enabled some correct code that used to cause errors (e.g. #33903 and #46095).
Removed deprecated unstable attribute #[simd].

Version 1.24.1 (2018-03-01)

Do not abort when unwinding through FFI
Emit UTF-16 files for linker arguments on Windows
Make the error index generator work again
Cargo will warn on Windows 7 if an update is needed.

Version 1.24.0 (2018-02-15)

Language

External sysv64 ffi is now available. eg. extern "sysv64" fn foo () {}

Compiler

rustc now uses 16 codegen units by default for release builds. For the fastest builds, utilize codegen-units=1.
Added armv4t-unknown-linux-gnueabi target.
Add aarch64-unknown-openbsd support

Libraries

str::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.
impl From<bool> for AtomicBool
impl From<{CString, &CStr}> for {Arc<CStr>, Rc<CStr>}
impl From<{OsString, &OsStr}> for {Arc<OsStr>, Rc<OsStr>}
impl From<{PathBuf, &Path}> for {Arc<Path>, Rc<Path>}
float::from_bits now just uses transmute. This provides some optimisations from LLVM.
Copied AsciiExt methods onto char
Remove T: Sized requirement on ptr::is_null()
impl From<RecvError> for {TryRecvError, RecvTimeoutError}
Optimised f32::{min, max} to generate more efficient x86 assembly
[u8]::contains now uses memchr which provides a 3x speed improvement

Stabilized APIs

RefCell::replace
RefCell::swap
atomic::spin_loop_hint

The following functions can now be used in a constant expression. eg. let buffer: [u8; size_of::<usize>()];, static COUNTER: AtomicUsize = AtomicUsize::new(1);

AtomicBool::new
AtomicUsize::new
AtomicIsize::new
AtomicPtr::new
Cell::new
{integer}::min_value
{integer}::max_value
mem::size_of
mem::align_of
ptr::null
ptr::null_mut
RefCell::new
UnsafeCell::new

Cargo

Added a workspace.default-members config that overrides implied --all in virtual workspaces.
Enable incremental by default on development builds. Also added configuration keys to Cargo.toml and .cargo/config to disable on a per-project or global basis respectively.

Misc

Compatibility Notes

Floating point types 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.
Unwinding will no longer go past FFI boundaries, and will instead abort.
Formatter::flags method is now deprecated. The sign_plus, sign_minus, alternate, and sign_aware_zero_pad should be used instead.
Leading zeros in tuple struct members is now an error
column!() macro is one-based instead of zero-based
fmt::Arguments can no longer be shared across threads
Access to #[repr(packed)] struct fields is now unsafe
Cargo sets a different working directory for the compiler

Version 1.23.0 (2018-01-04)

Language

Arbitrary auto traits are now permitted in trait objects.
rustc now uses subtyping on the left hand side of binary operations. Which should fix some confusing errors in some operations.

Compiler

Enabled TrapUnreachable in LLVM which should mitigate the impact of undefined behavior.
rustc now suggests renaming import if names clash.
Display errors/warnings correctly when there are zero-width or wide characters.
rustc now avoids unnecessary copies of arguments that are simple bindings This should improve memory usage on average by 5-10%.
Updated musl used to build musl rustc to 1.1.17

Libraries

Allow a trailing comma in assert_eq/ne macro
Implement Hash for raw pointers to unsized types
impl From<*mut T> for AtomicPtr<T>
impl From<usize/isize> for AtomicUsize/AtomicIsize.
Removed the T: Sync requirement for RwLock<T>: Send
Removed T: Sized requirement for {<*const T>, <*mut T>}::as_ref and <*mut T>::as_mut
Optimized Thread::{park, unpark} implementation
Improved SliceExt::binary_search performance.
impl FromIterator<()> for ()
Copied AsciiExt trait methods to primitive types. Use of AsciiExt is now deprecated.

Stabilized APIs

Cargo

Cargo now supports uninstallation of multiple packages eg. cargo uninstall foo bar uninstalls foo and bar.
Added unit test checking to cargo check
Cargo now lets you install a specific version using cargo install --version

Misc

Releases now ship with the Cargo book documentation.
rustdoc now prints rendering warnings on every run.

Compatibility Notes

Changes have been made to type equality to make it more correct, in rare cases this could break some code. Tracking issue for further information
char::escape_debug now uses Unicode 10 over 9.
Upgraded Android SDK to 27, and NDK to r15c. This drops support for Android 9, the minimum supported version is Android 14.
Bumped the minimum LLVM to 3.9

Version 1.22.1 (2017-11-22)

Update Cargo to fix an issue with macOS 10.13 "High Sierra"

Version 1.22.0 (2017-11-22)

Language

non_snake_case lint now allows extern no-mangle functions
Now accepts underscores in unicode escapes
T op= &T now works for numeric types. eg. let mut x = 2; x += &8;
types that impl Drop are now allowed in const and static types

Compiler

rustc now defaults to having 16 codegen units at debug on supported platforms.
rustc will no longer inline in codegen units when compiling for debug This should decrease compile times for debug builds.
strict memory alignment now enabled on ARMv6
Remove support for the PNaCl target le32-unknown-nacl

Libraries

Allow atomic operations up to 32 bits on armv5te_unknown_linux_gnueabi
Box<Error> now impls From<Cow<str>>
std::mem::Discriminant is now guaranteed to be Send + Sync
fs::copy now returns the length of the main stream on NTFS.
Properly detect overflow in Instant += Duration.
impl Hasher for {&mut Hasher, Box<Hasher>}
impl fmt::Debug for SplitWhitespace.
Option<T> now impls Try This allows for using ? with Option types.

Stabilized APIs

Cargo

Cargo will now build multi file examples in subdirectories of the examples folder that have a main.rs file.
Changed [root] to [package] in Cargo.lock Packages with the old format will continue to work and can be updated with cargo update.
Now supports vendoring git repositories

Misc

libbacktrace is now available on Apple platforms.
Stabilised the compile_fail attribute for code fences in doc-comments. This now lets you specify that a given code example will fail to compile.

Compatibility Notes

The minimum Android version that rustc can build for has been bumped to 4.0 from 2.3
Allowing T op= &T for numeric types has broken some type inference cases

Version 1.21.0 (2017-10-12)

Language

You can now use static references for literals. Example:

fn main() {
    let x: &'static u32 = &0;
}

Relaxed path syntax. Optional :: before < is now allowed in all contexts. Example:

my_macro!(Vec<i32>::new); // Always worked
my_macro!(Vec::<i32>::new); // Now works

Compiler

Upgraded jemalloc to 4.5.0
Enabled unwinding panics on Redox
Now runs LLVM in parallel during translation phase. This should reduce peak memory usage.

Libraries

Generate builtin impls for Clone for all arrays and tuples that are T: Clone
Stdin, 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>>.

Stabilized APIs

std::mem::discriminant

Cargo

You can now call cargo install with multiple package names
Cargo commands inside a virtual workspace will now implicitly pass --all
Added a [patch] section to Cargo.toml to handle prepublication dependencies RFC 1969
include & exclude fields in Cargo.toml now accept gitignore like patterns
Added the --all-targets option
Using required dependencies as a feature is now deprecated and emits a warning

Misc

Cargo docs are moving to doc.rust-lang.org/cargo
The rustdoc book is now available at doc.rust-lang.org/rustdoc
Added a preview of RLS has been made available through rustup Install with rustup component add rls-preview
std::os documentation for Unix, Linux, and Windows now appears on doc.rust-lang.org Previously only showed std::os::unix.

Compatibility Notes

Changes in method matching against higher-ranked types This may cause breakage in subtyping corner cases. A more in-depth explanation is available.
rustc's JSON error output's byte position start at top of file. Was previously relative to the rustc's internal CodeMap struct which required the unstable library libsyntax to correctly use.
unused_results lint no longer ignores booleans

Version 1.20.0 (2017-08-31)

Language

Associated constants are now stabilised.
A lot of macro bugs are now fixed.

Compiler

Struct fields are now properly coerced to the expected field type.
Enabled wasm LLVM backend WASM can now be built with the wasm32-experimental-emscripten target.
Changed some of the error messages to be more helpful.
Add support for RELRO(RELocation Read-Only) for platforms that support it.
rustc now reports the total number of errors on compilation failure previously this was only the number of errors in the pass that failed.
Expansion in rustc has been sped up 29x.
added msp430-none-elf target.
rustc will now suggest one-argument enum variant to fix type mismatch when applicable
Fixes backtraces on Redox
rustc now identifies different versions of same crate when absolute paths of different types match in an error message.

Libraries

Relaxed Debug constraints on {HashMap,BTreeMap}::{Keys,Values}.
Impl PartialEq, Eq, PartialOrd, Ord, Debug, Hash for unsized tuples.
Impl fmt::{Display, Debug} for Ref, RefMut, MutexGuard, RwLockReadGuard, RwLockWriteGuard
Impl Clone for DefaultHasher.
Impl Sync for SyncSender.
Impl FromStr for char
Fixed how {f32, f64}::{is_sign_negative, is_sign_positive} handles NaN.
allow messages in the unimplemented!() macro. ie. unimplemented!("Waiting for 1.21 to be stable")
pub(restricted) is now supported in the thread_local! macro.
Upgrade to Unicode 10.0.0
Reimplemented {f32, f64}::{min, max} in Rust instead of using CMath.
Skip the main thread's manual stack guard on Linux
Iterator::nth for 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 possible

Stabilized APIs

CStr::into_c_string
CString::as_c_str
CString::into_boxed_c_str
Chain::get_mut
Chain::get_ref
Chain::into_inner
Option::get_or_insert_with
Option::get_or_insert
OsStr::into_os_string
OsString::into_boxed_os_str
Take::get_mut
Take::get_ref
Utf8Error::error_len
char::EscapeDebug
char::escape_debug
compile_error!
f32::from_bits
f32::to_bits
f64::from_bits
f64::to_bits
mem::ManuallyDrop
slice::sort_unstable_by_key
slice::sort_unstable_by
slice::sort_unstable
str::from_boxed_utf8_unchecked
str::as_bytes_mut
str::as_bytes_mut
str::from_utf8_mut
str::from_utf8_unchecked_mut
str::get_mut
str::get_unchecked_mut
str::get_unchecked
str::get
str::into_boxed_bytes

Cargo

Cargo API token location moved from ~/.cargo/config to ~/.cargo/credentials.
Cargo will now build 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/client
You can now specify version of a binary when installed through cargo install using --vers.
Added --no-fail-fast flag to cargo to run all benchmarks regardless of failure.
Changed the convention around which file is the crate root.

Compatibility Notes

Functions with 'static in their return types will now not be as usable as if they were using lifetime parameters instead.
The reimplementation of {f32, f64}::is_sign_{negative, positive} now takes the sign of NaN into account where previously didn't.

Version 1.19.0 (2017-07-20)

Language

Numeric fields can now be used for creating tuple structs. RFC 1506 For example struct Point(u32, u32); let x = Point { 0: 7, 1: 0 };.
Macro recursion limit increased to 1024 from 64.
Added lint for detecting unused macros.
loop can now return a value with break. RFC 1624 For example: let x = loop { break 7; };
C compatible 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 }
Non capturing closures can now be coerced into fns, RFC 1558 Example: let foo: fn(u8) -> u8 = |v: u8| { v };

Compiler

Add support for bootstrapping the Rust compiler toolchain on Android.
Change 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.
Fixed ICE when removing a source file between compilation sessions.
Minor optimisation of string operations.
Compiler error message is now 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.
The compiler now supports Visual Studio 2017
The compiler is now built against LLVM 4.0.1 by default
Added a lot of new error codes
Added target-feature=+crt-static option RFC 1721 Which allows libraries with C Run-time Libraries(CRT) to be statically linked.
Fixed various ARM codegen bugs

Libraries

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 faster
eprint! and eprintln! macros added to prelude. Same as the print! macros, but for printing to stderr.

Stabilized APIs

OsString::shrink_to_fit
cmp::Reverse
Command::envs
thread::ThreadId

Cargo

Build scripts can now add environment variables to the environment the crate is being compiled in. Example: println!("cargo:rustc-env=FOO=bar");
Subcommands now replace the current process rather than spawning a new child process
Workspace members can now accept glob file patterns
Added --all flag to the cargo bench subcommand to run benchmarks of all the members in a given workspace.
Updated libssh2-sys to 0.2.6
Target directory path is now in the cargo metadata
Cargo no longer checks out a local working directory for the crates.io index This should provide smaller file size for the registry, and improve cloning times, especially on Windows machines.
Added an --exclude option for excluding certain packages when using the --all option
Cargo will now automatically retry when receiving a 5xx error from crates.io
The --features option now accepts multiple comma or space delimited values.
Added support for custom target specific runners

Misc

Added rust-windbg.cmd for loading rust .natvis files in the Windows Debugger.
Rust will now release XZ compressed packages
rustup will now prefer to download rust packages with XZ compression over GZip packages.
Added the ability to escape # in rust documentation By adding additional #'s ie. ## is now #

Compatibility Notes

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.
As a result of the -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.
Ending a float literal with ._ is now a hard error. Example: 42._ .
Any use of a private 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.
Floating point constants in match patterns is now a hard error This was previously a warning.
Struct or enum constants that don't derive PartialEq & Eq used match patterns is now a hard error This was previously a warning.
Lifetimes named '_ are no longer allowed. This was previously a warning.
From the pound escape, lines consisting of multiple #s are now visible
It is an error to re-export private enum variants. This is known to break a number of crates that depend on an older version of mustache.
On Windows, if VCINSTALLDIR is set incorrectly, rustc will try to use it to find the linker, and the build will fail where it did not previously

Version 1.18.0 (2017-06-08)

Language

Stabilize pub(restricted) pub 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.
Stabilize #![windows_subsystem] attribute conservative exposure of the /SUBSYSTEM linker flag on Windows platforms. RFC 1665.
Refactor of trait object type parsing Now 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.
0e+10 is now a valid floating point literal
Now warns if you bind a lifetime parameter to 'static
Tuples, Enum variant fields, and structs with no repr attribute or with #[repr(Rust)] are reordered to minimize padding and produce a smaller representation in some cases.

Compiler

rustc can now emit mir with --emit mir
Improved LLVM IR for trivial functions
Added explanation for E0090(Wrong number of lifetimes are supplied)
rustc compilation is now 15%-20% faster Thanks to optimisation opportunities found through profiling
Improved backtrace formatting when panicking

Libraries

Specialized Vec::from_iter being passed vec::IntoIter if the iterator hasn't been advanced the original Vec is reassembled with no actual iteration or reallocation.
Simplified HashMap Bucket interface provides performance improvements for iterating and cloning.
Specialize Vec::from_elem to use calloc
Fixed Race condition in fs::create_dir_all
No longer caching stdio on Windows
Optimized insertion sort in slice insertion sort in some cases 2.50%~ faster and in one case now 12.50% faster.
Optimized AtomicBool::fetch_nand

Stabilized APIs

Child::try_wait
HashMap::retain
HashSet::retain
PeekMut::pop
TcpStream::peek
UdpSocket::peek
UdpSocket::peek_from

Cargo

Added partial Pijul support Pijul is a version control system in Rust. You can now create new cargo projects with Pijul using cargo new --vcs pijul
Now always emits build script warnings for crates that fail to build
Added Android build support
Added --bins and --tests flags now you can build all programs of a certain type, for example cargo build --bins will build all binaries.
Added support for haiku

Misc

rustdoc can now use pulldown-cmark with the --enable-commonmark flag
Rust now uses the official cross compiler for NetBSD
rustdoc now accepts # at the start of files
Fixed jemalloc support for musl

Compatibility Notes

Changes 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
Overlapping inherent impls are now a hard error
PartialOrd and Ord must agree on the ordering.
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:
- Changed the link order of local static/dynamic libraries (respecting the order on given rather than having the compiler reorder).
- Changed how MinGW is linked, native code linked to dynamic libraries may require manually linking to the gcc support library (for the native code itself)

Version 1.17.0 (2017-04-27)

Language

The lifetime of statics and consts defaults to 'static. RFC 1623
Fields of structs may be initialized without duplicating the field/variable names. RFC 1682
Self may be included in the where clause of impls. RFC 1647
When coercing to an unsized type lifetimes must be equal. That is, there is no subtyping between T and U when T: Unsize. For example, coercing &mut [&'a X; N] to &mut [&'b X] requires 'a be equal to 'b. Soundness fix.
Values passed to the indexing operator, [], automatically coerce
Static variables may contain references to other statics

Compiler

Exit quickly on only --emit dep-info
Make -C relocation-model more correctly determine whether the linker creates a position-independent executable
Add -C overflow-checks to directly control whether integer overflow panics
The rustc type checker now checks items on demand instead of in a single in-order pass. This is mostly an internal refactoring in support of future work, including incremental type checking, but also resolves RFC 1647, allowing Self to appear in impl where clauses.
Optimize vtable loads
Turn off vectorization for Emscripten targets
Provide suggestions for unknown macros imported with use
Fix ICEs in path resolution
Strip exception handling code on Emscripten when panic=abort
Add clearer error message using &str + &str

Stabilized APIs

Arc::into_raw
Arc::from_raw
Arc::ptr_eq
Rc::into_raw
Rc::from_raw
Rc::ptr_eq
Ordering::then
Ordering::then_with
BTreeMap::range
BTreeMap::range_mut
collections::Bound
process::abort
ptr::read_unaligned
ptr::write_unaligned
Result::expect_err
Cell::swap
Cell::replace
Cell::into_inner
Cell::take

Libraries

BTreeMap and BTreeSet can iterate over ranges
Cell can store non-Copy types. RFC 1651
String 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 Display
Specialize PartialOrd<A> for [A] where A: Ord
Slightly optimize slice::sort
Add ToString trait specialization for Cow<'a, str> and String
Box<[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 string
Support unprivileged symlink creation in Windows
PathBuf implements Default
Implement PartialEq<[A]> for VecDeque<A>
HashMap resizes adaptively to guard against DOS attacks and poor hash functions.

Cargo

Add cargo check --all
Add an option to ignore SSL revocation checking
Add cargo run --package
Add required_features
Assume build.rs is a build script
Find workspace via workspace_root link in containing member

Misc

Documentation is rendered with mdbook instead of the obsolete, in-tree rustbook
The "Unstable Book" documents nightly-only features
Improve the style of the sidebar in rustdoc output
Configure build correctly on 64-bit CPU's with the armhf ABI
Fix MSP430 breakage due to i128
Preliminary Solaris/SPARCv9 support
rustc is linked statically on Windows MSVC targets, allowing it to run without installing the MSVC runtime.
rustdoc --test includes file names in test names
This release includes builds of std for sparc64-unknown-linux-gnu, aarch64-unknown-linux-fuchsia, and x86_64-unknown-linux-fuchsia.
Initial support for aarch64-unknown-freebsd
Initial support for i686-unknown-netbsd
This release no longer includes the old makefile build system. Rust is built with a custom build system, written in Rust, and with Cargo.
Add Debug implementations for libcollection structs
TypeId implements PartialOrd and Ord
--test-threads=0 produces an error
rustup installs documentation by default
The Rust source includes NatVis visualizations. These can be used by WinDbg and Visual Studio to improve the debugging experience.

Compatibility Notes

Rust 1.17 does not correctly detect the MSVC 2017 linker. As a workaround, either use MSVC 2015 or run vcvars.bat.
When coercing to an unsized type lifetimes must be equal. That is, disallow subtyping between T and U when T: Unsize, 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.
In-tree crates are verified to be unstable. Previously, some minor crates were marked stable and could be accessed from the stable toolchain.
Rust git source no longer includes vendored crates. Those that need to build with vendored crates should build from release tarballs.
Fix inert attributes from proc_macro_derives
During crate resolution, rustc prefers a crate in the sysroot if two crates are otherwise identical. Unlikely to be encountered outside the Rust build system.
Fixed bugs around how type inference interacts with dead-code. The existing code generally ignores the type of dead-code unless a type-hint is provided; this can cause surprising inference interactions particularly around defaulting. The new code uniformly ignores the result type of dead-code.
Tuple-struct constructors with private fields are no longer visible
Lifetime parameters that do not appear in the arguments are now considered early-bound, resolving a soundness bug (#32330). The hr_lifetime_in_assoc_type future-compatibility lint has been in effect since April of 2016.
rustdoc: fix doctests with non-feature crate attributes
Make transmuting from fn item types to pointer-sized types a hard error

Version 1.16.0 (2017-03-16)

Language

The compiler's dead_code lint now accounts for type aliases.
Uninhabitable enums (those without any variants) no longer permit wildcard match patterns
Clean up semantics of self in an import list
Self may appear in impl headers
Self may appear in struct expressions

Compiler

rustc 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.
Levenshtein based typo suggestions now work in most places, while previously they worked only for fields and sometimes for local variables. Together with the overhaul of "no resolution"/"unexpected resolution" errors (#38154) they result in large and systematic improvement in resolution diagnostics.
Fix transmute::<T, U> where T requires a bigger alignment than U
rustc: use -Xlinker when specifying an rpath with ',' in it
rustc no longer attempts to provide "consider using an explicit lifetime" suggestions. They were inaccurate.

Stabilized APIs

VecDeque::truncate
VecDeque::resize
String::insert_str
Duration::checked_add
Duration::checked_sub
Duration::checked_div
Duration::checked_mul
str::replacen
str::repeat
SocketAddr::is_ipv4
SocketAddr::is_ipv6
IpAddr::is_ipv4
IpAddr::is_ipv6
Vec::dedup_by
Vec::dedup_by_key
Result::unwrap_or_default
<*const T>::wrapping_offset
<*mut T>::wrapping_offset
CommandExt::creation_flags
File::set_permissions
String::split_off

Libraries

[T]::binary_search and [T]::binary_search_by_key now take their argument by Borrow parameter
All public types in std implement Debug
IpAddr implements From<Ipv4Addr> and From<Ipv6Addr>
Ipv6Addr implements From<[u16; 8]>
Ctrl-Z returns from Stdin.read() when reading from the console on Windows
std: Fix partial writes in LineWriter
std: Clamp max read/write sizes on Unix
Use more specific panic message for &str slicing errors
TcpListener::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 newline
Implement iter::Sum and iter::Product for Result
Reduce the size of static data in std_unicode::tables
char::EscapeDebug, EscapeDefault, EscapeUnicode, CaseMappingIter, ToLowercase, ToUppercase, implement Display
Duration implements Sum
String implements ToSocketAddrs

Cargo

The cargo check command does a type check of a project without building it
crates.io will display CI badges from Travis and AppVeyor, if specified in Cargo.toml
crates.io will display categories listed in Cargo.toml
Compilation profiles accept integer values for debug, in addition to true and false. These are passed to rustc as the value to -C debuginfo
Implement cargo --version --verbose
All builds now output 'dep-info' build dependencies compatible with make and ninja
Build all workspace members with build --all
Document all workspace members with doc --all
Path deps outside workspace are not members

Misc

rustdoc has a --sysroot argument that, like rustc, specifies the path to the Rust implementation
The armv7-linux-androideabi target no longer enables NEON extensions, per Google's ABI guide
The stock standard library can be compiled for Redox OS
Rust has initial SPARC support. Tier 3. No builds available.
Rust has experimental support for Nvidia PTX. Tier 3. No builds available.
Fix backtraces on i686-pc-windows-gnu by disabling FPO

Compatibility Notes

Uninhabitable enums (those without any variants) no longer permit wildcard match patterns
In this release, references to uninhabited types can not be pattern-matched. This was accidentally allowed in 1.15.
The compiler's dead_code lint now accounts for type aliases.
Ctrl-Z returns from Stdin.read() when reading from the console on Windows
Clean up semantics of self in an import list
Reimplemented lifetime elision. This change was almost entirely compatible with existing code, but it did close a number of small bugs and loopholes, as well as being more accepting in some other cases.

Version 1.15.1 (2017-02-09)

Fix IntoIter::as_mut_slice's signature
Compile compiler builtins with -fPIC on 32-bit platforms

Version 1.15.0 (2017-02-02)

Language

Basic procedural macros allowing custom #[derive], aka "macros 1.1", are stable. This allows popular code-generating crates like Serde and Diesel to work ergonomically. RFC 1681.
Tuple structs may be empty. Unary and empty tuple structs may be instantiated with curly braces. Part of RFC 1506.
A number of minor changes to name resolution have been activated. They add up to more consistent semantics, allowing for future evolution of Rust macros. Specified in RFC 1560, see its section on "changes" for details of what is different. The breaking changes here have been transitioned through the legacy_imports lint since 1.14, with no known regressions.
In macro_rules, path fragments can now be parsed as type parameter bounds
?Sized can be used in where clauses
There is now a limit on the size of monomorphized types and it can be modified with the #![type_size_limit] crate attribute, similarly to the #![recursion_limit] attribute

Compiler

On Windows, the compiler will apply dllimport attributes when linking to extern functions. Additional attributes and flags can control which library kind is linked and its name. RFC 1717.
Rust-ABI symbols are no longer exported from cdylibs
The --test flag works with procedural macro crates
Fix extern "aapcs" fn ABI
The -C no-stack-check flag is deprecated. It does nothing.
The format! expander recognizes incorrect printf and shell-style formatting directives and suggests the correct format.
Only report one error for all unused imports in an import list

Compiler Performance

Avoid unnecessary mk_ty calls in Ty::super_fold_with
Avoid more unnecessary mk_ty calls in Ty::super_fold_with
Don't clone in UnificationTable::probe
Remove scope_auxiliary to cut RSS by 10%
Use small vectors in type walker
Macro expansion performance was improved
Change HirVec<P<T>> to HirVec<T> in hir::Expr
Replace FNV with a faster hash function

Stabilized APIs

std::iter::Iterator::min_by
std::iter::Iterator::max_by
std::os::*::fs::FileExt
std::sync::atomic::Atomic*::get_mut
std::sync::atomic::Atomic*::into_inner
std::vec::IntoIter::as_slice
std::vec::IntoIter::as_mut_slice
std::sync::mpsc::Receiver::try_iter
std::os::unix::process::CommandExt::before_exec
std::rc::Rc::strong_count
std::rc::Rc::weak_count
std::sync::Arc::strong_count
std::sync::Arc::weak_count
std::char::encode_utf8
std::char::encode_utf16
std::cell::Ref::clone
std::io::Take::into_inner

Libraries

The standard sorting algorithm has been rewritten for dramatic performance improvements. It is a hybrid merge sort, drawing influences from Timsort. Previously it was a naive merge sort.
Iterator::nth no longer has a Sized bound
Extend<&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()
Fix ARM Objective-C ABI in std::env::args
Chinese characters display correctly in fmt::Debug
Derive Default for Duration
Support creation of anonymous pipes on WinXP/2k
mpsc::RecvTimeoutError implements Error
Don't pass overlapped handles to processes

Cargo

In this release, Cargo build scripts no longer have access to the 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.
Add --all flag to cargo test
Compile statically against the MSVC CRT
Mix feature flags into fingerprint/metadata shorthash
Link OpenSSL statically on OSX
Apply new fingerprinting to build dir outputs
Test for bad path overrides with summaries
Require cargo install --vers to take a semver version
Fix retrying crate downloads for network errors
Implement string lookup for build.rustflags config key
Emit more info on --message-format=json
Assume build.rs in the same directory as Cargo.toml is a build script
Don't ignore errors in workspace manifest
Fix --message-format JSON when rustc emits non-JSON warnings

Tooling

Test runners (binaries built with --test) now support a --list argument that lists the tests it contains
Test runners now support a --exact argument that makes the test filter match exactly, instead of matching only a substring of the test name
rustdoc supports a --playground-url flag
rustdoc provides more details about #[should_panic] errors

Misc

The Rust build system is now written in Rust. The Makefiles may continue to be used in this release by passing --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.
Rust supports i686-unknown-openbsd. Tier 3 support. No testing or releases.
Rust supports the MSP430. Tier 3 support. No testing or releases.
Rust supports the ARMv5TE architecture. Tier 3 support. No testing or releases.

Compatibility Notes

A number of minor changes to name resolution have been activated. They add up to more consistent semantics, allowing for future evolution of Rust macros. Specified in RFC 1560, see its section on "changes" for details of what is different. The breaking changes here have been transitioned through the legacy_imports lint since 1.14, with no known regressions.
In this release, Cargo build scripts no longer have access to the 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.
Higher-ranked lifetimes are no longer allowed to appear only in associated types. The 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.
The semantics relating modules to file system directories are changing in minor ways. This is captured in the new legacy_directory_ownership lint, which is a warning in this release, and will become a hard error in the future.
Rust-ABI symbols are no longer exported from cdylibs
Once Peekable peeks a None it will return that None without re-querying the underlying iterator

Version 1.14.0 (2016-12-22)

Language

.. matches multiple tuple fields in enum variants, structs and tuples. RFC 1492.
Safe fn items can be coerced to unsafe fn pointers
use * and use ::* both glob-import from the crate root
It's now possible to call a Vec<Box<Fn()>> without explicit dereferencing

Compiler

Mark enums with non-zero discriminant as non-zero
Lower-case static mut names are linted like other statics and consts
Fix ICE on some macros in const integer positions (e.g. [u8; m!()])
Improve error message and snippet for "did you mean x"
Add a panic-strategy field to the target specification
Include LLVM version in --version --verbose

Compile-time Optimizations

Improve macro expansion performance
Shrink Expr_::ExprInlineAsm
Replace all uses of SHA-256 with BLAKE2b
Reduce the number of bytes hashed by IchHasher
Avoid more allocations when compiling html5ever
Use SmallVector in CombineFields::instantiate
Avoid some allocations in the macro parser
Use a faster deflate setting
Add ArrayVec and AccumulateVec to reduce heap allocations during interning of slices
Optimize write_metadata
Don't process obligation forest cycles when stalled
Avoid many CrateConfig clones
Optimize Substs::super_fold_with
Optimize ObligationForest's NodeState handling
Speed up plug_leaks

Libraries

println!(), 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 iterators
Implement From<Cow<str>> for String and From<Cow<[T]>> for Vec<T>
Improve fold performance for chain, cloned, map, and VecDeque iterators
Improve SipHasher performance on small values
Add Iterator trait TrustedLen to enable better FromIterator / Extend
Expand .zip() specialization to .map() and .cloned()
ReadDir implements Debug
Implement RefUnwindSafe for atomic types
Specialize Vec::extend to Vec::extend_from_slice
Avoid allocations in Decoder::read_str
io::Error implements From<io::ErrorKind>
Impl Debug for raw pointers to unsized data
Don't reuse HashMap random seeds
The internal memory layout of HashMap is more cache-friendly, for significant improvements in some operations
HashMap uses less memory on 32-bit architectures
Impl Add<{str, Cow<str>}> for Cow<str>

Cargo

Expose rustc cfg values to build scripts
Allow cargo to work with read-only CARGO_HOME
Fix passing --features when testing multiple packages
Use a single profile set per workspace
Load replace sections from lock files
Ignore panic configuration for test/bench profiles

Tooling

rustup is the recommended Rust installation method
This release includes host (rustc) builds for Linux on MIPS, PowerPC, and S390x. These are tier 2 platforms and may have major defects. Follow the instructions on the website to install, or add the targets to an existing installation with rustup target add. The new target triples are:
- mips-unknown-linux-gnu
- mipsel-unknown-linux-gnu
- mips64-unknown-linux-gnuabi64
- mips64el-unknown-linux-gnuabi64
- powerpc-unknown-linux-gnu
- powerpc64-unknown-linux-gnu
- powerpc64le-unknown-linux-gnu
- s390x-unknown-linux-gnu
This release includes target (std) builds for ARM Linux running MUSL libc. These are tier 2 platforms and may have major defects. Add the following triples to an existing rustup installation with rustup target add:
- arm-unknown-linux-musleabi
- arm-unknown-linux-musleabihf
- armv7-unknown-linux-musleabihf
This release includes experimental support for WebAssembly, via the wasm32-unknown-emscripten target. This target is known to have major defects. Please test, report, and fix.
rustup no longer installs documentation by default. Run rustup component add rust-docs to install.
Fix line stepping in debugger
Enable line number debuginfo in releases

Misc

Disable jemalloc on aarch64/powerpc/mips
Add support for Fuchsia OS
Detect local-rebuild by only MAJOR.MINOR version

Compatibility Notes

A number of forward-compatibility lints used by the compiler to gradually introduce language changes have been converted to deny by default:
Prohibit patterns in trait methods without bodies
The atomic Ordering enum may not be matched exhaustively
Future-proofing #[no_link] breaks some obscure cases
The $crate macro variable is accepted in fewer locations
Impls specifying extra region requirements beyond the trait they implement are rejected
Enums may not be unsized. Unsized enums are intended to work but never have. For now they are forbidden.
Enforce the shadowing restrictions from RFC 1560 for today's macros

Version 1.13.0 (2016-11-10)

Language

Stabilize the ? operator. ? is a simple way to propagate errors, like the try! macro, described in RFC 0243.
Stabilize macros in type position. Described in RFC 873.
Stabilize attributes on statements. Described in RFC 0016.
Fix #[derive] for empty tuple structs/variants
Fix lifetime rules for 'if' conditions
Avoid loading and parsing unconfigured non-inline modules

Compiler

Add the -C link-arg argument
Remove the old AST-based backend from rustc_trans
Don't enable NEON by default on armv7 Linux
Fix debug line number info for macro expansions
Do not emit "class method" debuginfo for types that are not DICompositeType
Warn about multiple conflicting #[repr] hints
When sizing DST, don't double-count nested struct prefixes
Default RUST_MIN_STACK to 16MiB for now
Improve rlib metadata format. Reduces rlib size significantly.
Reject macros with empty repetitions to avoid infinite loop
Expand macros without recursing to avoid stack overflows

Diagnostics

Replace macro backtraces with labeled local uses
Improve error message for misplaced doc comments
Buffer unix and lock windows to prevent message interleaving
Update lifetime errors to specifically note temporaries
Special case a few colors for Windows
Suggest use self when such an import resolves
Be more specific when type parameter shadows primitive type
Many minor improvements

Compile-time Optimizations

Compute and cache HIR hashes at beginning
Don't hash types in loan paths
Cache projections in trans
Optimize the parser's last token handling
Only instantiate #[inline] functions in codegen units referencing them. This leads to big improvements in cases where crates export define many inline functions without using them directly.
Lazily allocate TypedArena's first chunk
Don't allocate during default HashSet creation

Stabilized APIs

checked_abs
wrapping_abs
overflowing_abs
RefCell::try_borrow
RefCell::try_borrow_mut

Libraries

Add assert_ne! and debug_assert_ne!
Make vec_deque::Drain, hash_map::Drain, and hash_set::Drain covariant
Implement AsRef<[T]> for std::slice::Iter
Implement Debug for std::vec::IntoIter
CString: avoid excessive growth just to 0-terminate
Implement CoerceUnsized for {Cell, RefCell, UnsafeCell}
Use arc4rand on FreeBSD
memrchr: Correct aligned offset computation
Improve Demangling of Rust Symbols
Use monotonic time in condition variables
Implement Debug for std::path::{Components,Iter}
Implement conversion traits for char
Fix illegal instruction caused by overflow in channel cloning
Zero first byte of CString on drop
Inherit overflow checks for sum and product
Add missing Eq implementations
Implement Debug for DirEntry
When getaddrinfo returns EAI_SYSTEM retrieve actual error from errno
SipHasher is deprecated. Use DefaultHasher.
Implement more traits for std::io::ErrorKind
Optimize BinaryHeap bounds checking
Work around pointer aliasing issue in Vec::extend_from_slice, extend_with_element
Fix overflow checking in unsigned pow()

Cargo

This release includes security fixes to both curl and OpenSSL.
Fix transitive doctests when panic=abort
Add --all-features flag to cargo
Reject path-based dependencies in cargo package
Don't parse the home directory more than once
Don't try to generate Cargo.lock on empty workspaces
Update OpenSSL to 1.0.2j
Add license and license_file to cargo metadata output
Make crates-io registry URL optional in config; ignore all changes to source.crates-io
Don't download dependencies from other platforms
Build transitive dev-dependencies when needed
Add support for per-target rustflags in .cargo/config
Avoid updating registry when adding existing deps
Warn about path overrides that won't work
Use workspaces during cargo install
Leak mspdbsrv.exe processes on Windows
Add --message-format flag
Pass target environment for rustdoc
Use CommandExt::exec for cargo run on Unix
Update curl and curl-sys
Call rustdoc test with the correct cfg flags of a package

Tooling

rustdoc: Add the --sysroot argument
rustdoc: Fix a couple of issues with the search results
rustdoc: remove the ! from macro URLs and titles
gdb: Fix pretty-printing special-cased Rust types
rustdoc: Filter more incorrect methods inherited through Deref

Misc

Remove unmaintained style guide
Add s390x support
Initial work at Haiku OS support
Add mips-uclibc targets
Crate-ify compiler-rt into compiler-builtins
Add rustc version info (git hash + date) to dist tarball
Many documentation improvements

Compatibility Notes

SipHasher is deprecated. Use DefaultHasher.
Deny (by default) transmuting from fn item types to pointer-sized types. Continuing the long transition to zero-sized fn items, per RFC 401.
Fix #[derive] for empty tuple structs/variants. Part of RFC 1506.
Issue deprecation warnings for safe accesses to extern statics
Fix lifetime rules for 'if' conditions.
Inherit overflow checks for sum and product.
Forbid user-defined macros named "macro_rules".

Version 1.12.1 (2016-10-20)

Regression Fixes

ICE: 'rustc' panicked at 'assertion failed: concrete_substs.is_normalized_for_trans()' #36381
Confusion with double negation and booleans
rustc 1.12.0 fails with SIGSEGV in release mode (syn crate 0.8.0)
Rustc 1.12.0 Windows build of ethcore crate fails with LLVM error
1.12.0: High memory usage when linking in release mode with debug info
Corrupted memory after updated to 1.12
"Let NullaryConstructor = something;" causes internal compiler error: "tried to overwrite interned AdtDef"
Fix ICE: inject bitcast if types mismatch for invokes/calls/stores
debuginfo: Handle spread_arg case in MIR-trans in a more stable way.

Version 1.12.0 (2016-09-29)

Highlights

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.
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.

Compiler

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 the Rust target name, not the LLVM target name, with --print target-list
The computation of TypeId is correct in some cases where it was previously producing inconsistent results
The mips-unknown-linux-gnu target uses hardware floating point by default
The rustc 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 arguments
rustc 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.

Diagnostics

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.
In error descriptions, references are now described in plain English, instead of as "&-ptr"
In error type descriptions, unknown numeric types are named {integer} or {float} instead of _
rustc emits a clearer error when inner attributes follow a doc comment

Language

macro_rules! invocations can be made within macro_rules! invocations
macro_rules! meta-variables are hygienic
macro_rules! tt matchers can be reparsed correctly, making them much more useful
macro_rules! stmt matchers correctly consume the entire contents when inside non-braces invocations
Semicolons are properly required as statement delimiters inside macro_rules! invocations
cfg_attr works on path attributes

Stabilized APIs

Cell::as_ptr
RefCell::as_ptr
IpAddr::is_unspecified
IpAddr::is_loopback
IpAddr::is_multicast
Ipv4Addr::is_unspecified
Ipv6Addr::octets
LinkedList::contains
VecDeque::contains
ExitStatusExt::from_raw. Both on Unix and Windows.
Receiver::recv_timeout
RecvTimeoutError
BinaryHeap::peek_mut
PeekMut
iter::Product
iter::Sum
OccupiedEntry::remove_entry
VacantEntry::into_key

Libraries

The format! macro and friends now allow a single argument to be formatted in multiple styles
The lifetime bounds on [T]::binary_search_by and [T]::binary_search_by_key have been adjusted to be more flexible
Option implements From for its contained type
Cell, RefCell and UnsafeCell implement From for their contained type
RwLock panics if the reader count overflows
vec_deque::Drain, hash_map::Drain and hash_set::Drain are covariant
vec::Drain and binary_heap::Drain are covariant
Cow<str> implements FromIterator for char, &str and String
Sockets on Linux are correctly closed in subprocesses via SOCK_CLOEXEC
hash_map::Entry, hash_map::VacantEntry and hash_map::OccupiedEntry implement Debug
btree_map::Entry, btree_map::VacantEntry and btree_map::OccupiedEntry implement Debug
String implements AddAssign
Variadic extern fn pointers implement the Clone, PartialEq, Eq, PartialOrd, Ord, Hash, fmt::Pointer, and fmt::Debug traits
FileType implements Debug
References to Mutex and RwLock are unwind-safe
mpsc::sync_channel Receivers return any available message before reporting a disconnect
Unicode definitions have been updated to 9.0
env iterators implement DoubleEndedIterator

Cargo

Support local mirrors of registries
Add support for command aliases
Allow opt-level="s" / opt-level="z" in profile overrides
Make cargo doc --open --target work as expected
Speed up noop registry updates
Update OpenSSL
Fix --panic=abort with plugins
Always pass -C metadata to the compiler
Fix depending on git repos with workspaces
Add a --lib flag to cargo new
Add http.cainfo for custom certs
Indicate the compilation profile after compiling
Allow enabling features for dependencies with --features
Add --jobs flag to cargo package
Add --dry-run to cargo publish
Add support for RUSTDOCFLAGS

Performance

panic::catch_unwind is more optimized
panic::catch_unwind no longer accesses thread-local storage on entry

Tooling

Test binaries now support a --test-threads argument to specify the number of threads used to run tests, and which acts the same as the RUST_TEST_THREADS environment variable
The test runner now emits a warning when tests run over 60 seconds
rustdoc: Fix methods in search results
rust-lldb warns about unsupported versions of LLDB
Rust releases now come with source packages that can be installed by rustup via rustup component add rust-src. The resulting source code can be used by tools and IDES, located in the sysroot under lib/rustlib/src.

Misc

The compiler can now be built against LLVM 3.9
Many minor improvements to the documentation.
The Rust exception handling "personality" routine is now written in Rust

Compatibility Notes

When printing Windows OsStrs, unpaired surrogate codepoints are escaped with the lowercase format instead of the uppercase
When formatting strings, if "precision" is specified, the "fill", "align" and "width" specifiers are no longer ignored
The Debug impl for strings no longer escapes all non-ASCII characters

Version 1.11.0 (2016-08-18)

Language

Support nested cfg_attr attributes
Allow statement-generating braced macro invocations at the end of blocks
Macros can be expanded inside of trait definitions
#[macro_use] works properly when it is itself expanded from a macro

Stabilized APIs

BinaryHeap::append
BTreeMap::append
BTreeMap::split_off
BTreeSet::append
BTreeSet::split_off
f32::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::sum
Iterator::product
Cell::get_mut
RefCell::get_mut

Libraries

The thread_local! macro supports multiple definitions in a single invocation, and can apply attributes
Cow implements Default
Wrapping implements binary, octal, lower-hex and upper-hex Display formatting
The range types implement Hash
lookup_host ignores unknown address types
assert_eq! accepts a custom error message, like assert! does
The main thread is now called "main" instead of "<main>"

Cargo

Disallow specifying features of transitive deps
Add color support for Windows consoles
Fix harness = false on [lib] sections
Don't panic when links contains a '.'
Build scripts can emit warnings, and -vv prints warnings for all crates.
Ignore file locks on OS X NFS mounts
Don't warn about package.metadata keys. This provides room for expansion by arbitrary tools.
Add support for cdylib crate types
Prevent publishing crates when files are dirty
Don't fetch all crates on clean
Propagate --color option to rustc
Fix cargo doc --open on Windows
Improve autocompletion
Configure colors of stderr as well as stdout

Performance

Caching projections speeds up type check dramatically for some workloads
The default HashMap hasher is SipHash 1-3 instead of SipHash 2-4 This hasher is faster, but is believed to provide sufficient protection from collision attacks.
Comparison of Ipv4Addr is 10x faster

Rustdoc

Fix empty implementation section on some module pages
Fix inlined renamed re-exports in import lists
Fix search result layout for enum variants and struct fields
Fix issues with source links to external crates
Fix redirect pages for renamed re-exports

Tooling

rustc is better at finding the MSVC toolchain
When emitting debug info, rustc emits frame pointers for closures, shims and glue, as it does for all other functions
rust-lldb warns about unsupported versions of LLDB
Many more errors have been given error codes and extended explanations
API documentation continues to be improved, with many new examples

Misc

rustc no longer hangs when dependencies recursively re-export submodules
rustc requires LLVM 3.7+
The 'How Safe and Unsafe Interact' chapter of The Rustonomicon was rewritten
rustc support 16-bit pointer sizes. No targets use this yet, but it works toward AVR support.

Compatibility Notes

consts and statics may not have unsized types
The new follow-set rules that place restrictions on macro_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.

Version 1.10.0 (2016-07-07)

Language

Copy types are required to have a trivial implementation of Clone. RFC 1521.
Single-variant enums support the #[repr(..)] attribute.
Fix #[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.
Add a new crate type, 'cdylib'. cdylibs are dynamic libraries suitable for loading by non-Rust hosts. RFC 1510. Note that Cargo does not yet directly support cdylibs.

Stabilized APIs

os::windows::fs::OpenOptionsExt::access_mode
os::windows::fs::OpenOptionsExt::share_mode
os::windows::fs::OpenOptionsExt::custom_flags
os::windows::fs::OpenOptionsExt::attributes
os::windows::fs::OpenOptionsExt::security_qos_flags
os::unix::fs::OpenOptionsExt::custom_flags
sync::Weak::new
Default for sync::Weak
panic::set_hook
panic::take_hook
panic::PanicInfo
panic::PanicInfo::payload
panic::PanicInfo::location
panic::Location
panic::Location::file
panic::Location::line
ffi::CStr::from_bytes_with_nul
ffi::CStr::from_bytes_with_nul_unchecked
ffi::FromBytesWithNulError
fs::Metadata::modified
fs::Metadata::accessed
fs::Metadata::created
sync::atomic::Atomic{Usize,Isize,Bool,Ptr}::compare_exchange
sync::atomic::Atomic{Usize,Isize,Bool,Ptr}::compare_exchange_weak
collections::{btree,hash}_map::{Occupied,Vacant,}Entry::key
os::unix::net::{UnixStream, UnixListener, UnixDatagram, SocketAddr}
SocketAddr::is_unnamed
SocketAddr::as_pathname
UnixStream::connect
UnixStream::pair
UnixStream::try_clone
UnixStream::local_addr
UnixStream::peer_addr
UnixStream::set_read_timeout
UnixStream::set_write_timeout
UnixStream::read_timeout
UnixStream::write_timeout
UnixStream::set_nonblocking
UnixStream::take_error
UnixStream::shutdown
Read/Write/RawFd impls for UnixStream
UnixListener::bind
UnixListener::accept
UnixListener::try_clone
UnixListener::local_addr
UnixListener::set_nonblocking
UnixListener::take_error
UnixListener::incoming
RawFd impls for UnixListener
UnixDatagram::bind
UnixDatagram::unbound
UnixDatagram::pair
UnixDatagram::connect
UnixDatagram::try_clone
UnixDatagram::local_addr
UnixDatagram::peer_addr
UnixDatagram::recv_from
UnixDatagram::recv
UnixDatagram::send_to
UnixDatagram::send
UnixDatagram::set_read_timeout
UnixDatagram::set_write_timeout
UnixDatagram::read_timeout
UnixDatagram::write_timeout
UnixDatagram::set_nonblocking
UnixDatagram::take_error
UnixDatagram::shutdown
RawFd impls for UnixDatagram
{BTree,Hash}Map::values_mut
<[_]>::binary_search_by_key

Libraries

The abs_sub method of floats is deprecated. The semantics of this minor method are subtle and probably not what most people want.
Add implementation of Ord for Cell and RefCell where T: Ord.
On Linux, if HashMaps can't be initialized with getrandom they will fall back to /dev/urandom temporarily to avoid blocking during early boot.
Implemented negation for wrapping numerals.
Implement Clone for binary_heap::IntoIter.
Implement Display and Hash for std::num::Wrapping.
Add Default implementation for &CStr, CString.
Implement From<Vec<T>> and Into<Vec<T>> for VecDeque<T>.
Implement Default for UnsafeCell, fmt::Error, Condvar, Mutex, RwLock.

Cargo

Cargo.toml supports the profile.*.panic option. This controls the runtime behavior of the panic! macro and can be either "unwind" (the default), or "abort". RFC 1513.
Don't throw away errors with -p arguments.
Report status to stderr instead of stdout.
Build scripts are passed a CARGO_MANIFEST_LINKS environment variable that corresponds to the links field of the manifest.
Ban keywords from crate names.
Canonicalize CARGO_HOME on Windows.
Retry network requests. By default they are retried twice, which can be customized with the net.retry value in .cargo/config.
Don't print extra error info for failing subcommands.
Add --force flag to cargo install.
Don't use flock on NFS mounts.
Prefer building cargo install artifacts in temporary directories. Makes it possible to install multiple crates in parallel.
Add cargo test --doc.
Add cargo --explain.
Don't print warnings when -q is passed.
Add cargo doc --lib and --bin.
Don't require build script output to be UTF-8.
Correctly attempt multiple git usernames.

Performance

rustc memory usage was reduced by refactoring the context used for type checking.
Speed up creation of HashMaps by caching the random keys used to initialize the hash state.
The find implementation for Chain iterators is 2x faster.
Trait selection optimizations speed up type checking by 15%.
Efficient trie lookup for boolean Unicode properties. 10x faster than the previous lookup tables.
Special case #[derive(Copy, Clone)] to avoid bloat.

Usability

Many incremental improvements to documentation and rustdoc.
rustdoc: List blanket trait impls.
rustdoc: Clean up ABI rendering.
Indexing with the wrong type produces a more informative error.
Improve diagnostics for constants being used in irrefutable patterns.
When many method candidates are in scope limit the suggestions to 10.
Remove confusing suggestion when calling a fn type.
Do not suggest changing &mut self to &mut mut self.

Misc

Update i686-linux-android features to match Android ABI.
Update aarch64-linux-android features to match Android ABI.
std no longer prints backtraces on platforms where the running module must be loaded with env::current_exe, which can't be relied on.
This release includes std binaries for the i586-unknown-linux-gnu, i686-unknown-linux-musl, and armv7-linux-androideabi targets. The i586 target is for old x86 hardware without SSE2, and the armv7 target is for Android running on modern ARM architectures.
The rust-gdb and rust-lldb scripts are distributed on all Unix platforms.
On Unix the runtime aborts by calling libc::abort instead of generating an illegal instruction.
Rust is now bootstrapped from the previous release of Rust, instead of a snapshot from an arbitrary commit.

Compatibility Notes

AtomicBool is now bool-sized, not word-sized.
target_env for Linux ARM targets is just gnu, not gnueabihf, gnueabi, etc.
Consistently panic on overflow in Duration::new.
Change String::truncate to panic less.
Add :block to the follow set for :ty and :path. Affects how macros are parsed.
Fix macro hygiene bug.
Feature-gated attributes on macro-generated macro invocations are now rejected.
Suppress fallback and ambiguity errors during type inference. This caused some minor changes to type inference.

Version 1.9.0 (2016-05-26)

Language

The #[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.
Field and method resolution understand visibility, so private fields and methods cannot prevent the proper use of public fields and methods.
The parser considers unicode codepoints in the PATTERN_WHITE_SPACE category to be whitespace.

Stabilized APIs

std::panic
std::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_mut
AsciiExt::make_ascii_uppercase
AsciiExt::make_ascii_lowercase
char::decode_utf16
char::DecodeUtf16
char::DecodeUtf16Error
char::DecodeUtf16Error::unpaired_surrogate
BTreeSet::take
BTreeSet::replace
BTreeSet::get
HashSet::take
HashSet::replace
HashSet::get
OsString::with_capacity
OsString::clear
OsString::capacity
OsString::reserve
OsString::reserve_exact
OsStr::is_empty
OsStr::len
std::os::unix::thread
RawPthread
JoinHandleExt
JoinHandleExt::as_pthread_t
JoinHandleExt::into_pthread_t
HashSet::hasher
HashMap::hasher
CommandExt::exec
File::try_clone
SocketAddr::set_ip
SocketAddr::set_port
SocketAddrV4::set_ip
SocketAddrV4::set_port
SocketAddrV6::set_ip
SocketAddrV6::set_port
SocketAddrV6::set_flowinfo
SocketAddrV6::set_scope_id
slice::copy_from_slice
ptr::read_volatile
ptr::write_volatile
OpenOptions::create_new
TcpStream::set_nodelay
TcpStream::nodelay
TcpStream::set_ttl
TcpStream::ttl
TcpStream::set_only_v6
TcpStream::only_v6
TcpStream::take_error
TcpStream::set_nonblocking
TcpListener::set_ttl
TcpListener::ttl
TcpListener::set_only_v6
TcpListener::only_v6
TcpListener::take_error
TcpListener::set_nonblocking
UdpSocket::set_broadcast
UdpSocket::broadcast
UdpSocket::set_multicast_loop_v4
UdpSocket::multicast_loop_v4
UdpSocket::set_multicast_ttl_v4
UdpSocket::multicast_ttl_v4
UdpSocket::set_multicast_loop_v6
UdpSocket::multicast_loop_v6
UdpSocket::set_multicast_ttl_v6
UdpSocket::multicast_ttl_v6
UdpSocket::set_ttl
UdpSocket::ttl
UdpSocket::set_only_v6
UdpSocket::only_v6
UdpSocket::join_multicast_v4
UdpSocket::join_multicast_v6
UdpSocket::leave_multicast_v4
UdpSocket::leave_multicast_v6
UdpSocket::take_error
UdpSocket::connect
UdpSocket::send
UdpSocket::recv
UdpSocket::set_nonblocking

Libraries

std::sync::Once is poisoned if its initialization function fails.
cell::Ref and cell::RefMut can contain unsized types.
Most types implement fmt::Debug.
The default buffer size used by 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

Cargo can now run concurrently.
Top-level overrides allow specific revisions of crates to be overridden through the entire crate graph. This is intended to make upgrades easier for large projects, by allowing crates to be forked temporarily until they've been upgraded and republished.
Cargo exports a CARGO_PKG_AUTHORS environment variable.
Cargo will pass the contents of the RUSTFLAGS variable to rustc on the commandline. rustc arguments can also be specified in the build.rustflags configuration key.

Performance

The time complexity of comparing variables for equivalence during type unification is reduced from O(n!) to O(n). This leads to major compilation time improvement in some scenarios.
ToString is specialized for str, giving it the same performance as to_owned.
Spawning processes with Command::output no longer creates extra threads.
#[derive(PartialEq)] and #[derive(PartialOrd)] emit less code for C-like enums.

Misc

Passing the --quiet flag to a test runner will produce much-abbreviated output.
The Rust Project now publishes std binaries for the mips-unknown-linux-musl, mipsel-unknown-linux-musl, and i586-pc-windows-msvc targets.

Compatibility Notes

std::sync::Once is poisoned if its initialization function fails.
It is illegal to define methods with the same name in overlapping inherent 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.
Improvements to const evaluation may trigger new errors when integer literals are out of range.

Version 1.8.0 (2016-04-14)

Language

Rust supports overloading of compound assignment statements like += by implementing the AddAssign, SubAssign, MulAssign, DivAssign, RemAssign, BitAndAssign, BitOrAssign, BitXorAssign, ShlAssign, or ShrAssign traits. RFC 953.
Empty structs can be defined with braces, as in struct Foo { }, in addition to the non-braced form, struct Foo;. RFC 218.

Libraries

Stabilized APIs:
- str::encode_utf16 (renamed from utf16_units)
- str::EncodeUtf16 (renamed from Utf16Units)
- Ref::map
- RefMut::map
- ptr::drop_in_place
- time::Instant
- time::SystemTime
- Instant::now
- Instant::duration_since (renamed from duration_from_earlier)
- Instant::elapsed
- SystemTime::now
- SystemTime::duration_since (renamed from duration_from_earlier)
- SystemTime::elapsed
- Various Add/Sub impls for Time and SystemTime
- SystemTimeError
- SystemTimeError::duration
- Various impls for SystemTimeError
- UNIX_EPOCH
- AddAssign, SubAssign, MulAssign, DivAssign, RemAssign, BitAndAssign, BitOrAssign, BitXorAssign, ShlAssign, ShrAssign.
The write! and writeln! macros correctly emit errors if any of their arguments can't be formatted.
Various I/O functions support large files on 32-bit Linux.
The Unix-specific 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.
The Unix-specific 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.
Atomic loads and stores are not volatile.
All types in sync::mpsc implement fmt::Debug.

Performance

Inlining hash functions lead to a 3% compile-time improvement in some workloads.
When using jemalloc, its symbols are unprefixed so that it overrides the libc malloc implementation. This means that for rustc, LLVM is now using jemalloc, which results in a 6% compile-time improvement on a specific workload.
Avoid quadratic growth in function size due to cleanups.

Misc

32-bit MSVC builds finally implement unwinding. i686-pc-windows-msvc is now considered a tier-1 platform.
The --print targets flag prints a list of supported targets.
The --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.
Errors for non-exhaustive match patterns now list up to 3 missing variants while also indicating the total number of missing variants if more than 3.
Executable stacks are disabled on Linux and BSD.
The Rust Project now publishes binary releases of the standard library for a number of tier-2 targets: 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

cargo init creates a new Cargo project in the current directory. It is otherwise like cargo new.
Cargo has configuration keys for -v and --color. verbose and color, respectively, go in the [term] section of .cargo/config.
Configuration keys that evaluate to strings or integers can be set via environment variables. For example the build.jobs key can be set via CARGO_BUILD_JOBS. Environment variables take precedence over config files.
Target-specific dependencies support Rust cfg syntax for describing targets so that dependencies for multiple targets can be specified together. RFC 1361.
The environment variables CARGO_TARGET_ROOT, RUSTC, and RUSTDOC take precedence over the build.target-dir, build.rustc, and build.rustdoc configuration values.
The child process tree is killed on Windows when Cargo is killed.
The build.target configuration value sets the target platform, like --target.

Compatibility Notes

Unstable compiler flags have been further restricted. Since 1.0 -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.
It is no longer possible to match on empty enum variants using the Variant(..) syntax. This has been a warning since 1.6.
The Unix-specific 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.
Modules sourced from the filesystem cannot appear within arbitrary blocks, but only within other modules.
--cfg compiler flags are parsed strictly as identifiers.
On Unix, stack overflow triggers a runtime abort instead of a SIGSEGV.
Command::spawn and its equivalents return an error if any of its command-line arguments contain interior NULs.
Tuple and unit enum variants from other crates are in the type namespace.
On Windows 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.

Version 1.7.0 (2016-03-03)

Libraries

Stabilized APIs
- Path
 - Path::strip_prefix (renamed from relative_from)
 - path::StripPrefixError (new error type returned from strip_prefix)
- Ipv4Addr
- Ipv6Addr
- Vec
 - Vec::as_slice
 - Vec::as_mut_slice
- String
 - String::as_str
 - String::as_mut_str
- Slices
 - <[T]>::clone_from_slice, which now requires the two slices to be the same length
 - <[T]>::sort_by_key
- checked, saturated, and overflowing operations
 - i32::checked_rem, i32::checked_neg, i32::checked_shl, i32::checked_shr
 - i32::saturating_mul
 - i32::overflowing_add, i32::overflowing_sub, i32::overflowing_mul, i32::overflowing_div
 - i32::overflowing_rem, i32::overflowing_neg, i32::overflowing_shl, i32::overflowing_shr
 - u32::checked_rem, u32::checked_neg, u32::checked_shl, u32::checked_shl
 - u32::saturating_mul
 - u32::overflowing_add, u32::overflowing_sub, u32::overflowing_mul, u32::overflowing_div
 - u32::overflowing_rem, u32::overflowing_neg, u32::overflowing_shl, u32::overflowing_shr
 - and checked, saturated, and overflowing operations for other primitive types
- FFI
 - ffi::IntoStringError
 - CString::into_string
 - CString::into_bytes
 - CString::into_bytes_with_nul
 - From<CString> for Vec<u8>
- IntoStringError
 - IntoStringError::into_cstring
 - IntoStringError::utf8_error
 - Error for IntoStringError
- Hashing
Validating UTF-8 is faster by a factor of between 7 and 14x for ASCII input. This means that creating Strings and strs from bytes is faster.
The performance of 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.

Misc

When running tests with --test, rustdoc will pass --cfg arguments to the compiler.
The compiler is built with RPATH information by default. This means that it will be possible to run 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

cargo rustc accepts a --profile flag that runs rustc under any of the compilation profiles, 'dev', 'bench', or 'test'.
The rerun-if-changed build script directive no longer causes the build script to incorrectly run twice in certain scenarios.

Compatibility Notes

Soundness fixes to the interactions between associated types and lifetimes, specified in RFC 1214, now generate errors for code that violates the new rules. This is a significant change that is known to break existing code, so it has emitted warnings for the new error cases since 1.4 to give crate authors time to adapt. The details of what is changing are subtle; read the RFC for more.
Several bugs in the compiler's visibility calculations were fixed. Since this was found to break significant amounts of code, the new errors will be emitted as warnings for several release cycles, under the private_in_public lint.
Defaulted type parameters were accidentally accepted in positions that were not intended. In this release, defaulted type parameters appearing outside of type definitions will generate a warning, which will become an error in future releases.
Parsing "." as a float results in an error instead of 0. That is, ".".parse::<f32>() returns Err, not Ok(0.0).
Borrows of closure parameters may not outlive the closure.

Version 1.6.0 (2016-01-21)

Language

The #![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.

Libraries

Stabilized APIs: 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).
The core library is stable, as are most of its APIs.
The assert_eq! macro supports arguments that don't implement Sized, such as arrays. In this way it behaves more like assert!.
Several timer functions that take duration in milliseconds are deprecated in favor of those that take Duration. These include Condvar::wait_timeout_ms, thread::sleep_ms, and thread::park_timeout_ms.
The algorithm by which 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.
Sorting slices that are already sorted is 50% faster in some cases.

Cargo

Cargo will look in $CARGO_HOME/bin for subcommands by default.
Cargo build scripts can specify their dependencies by emitting the rerun-if-changed key.
crates.io will reject publication of crates with dependencies that have a wildcard version constraint. Crates with wildcard dependencies were seen to cause a variety of problems, as described in RFC 1241. Since 1.5 publication of such crates has emitted a warning.
cargo clean accepts a --release flag to clean the release folder. A variety of artifacts that Cargo failed to clean are now correctly deleted.

Misc

The unreachable_code lint warns when a function call's argument diverges.
The parser indicates failures that may be caused by confusingly-similar Unicode characters
Certain macro errors are reported at definition time, not expansion.

Compatibility Notes

The compiler no longer makes use of the RUST_PATH environment variable when locating crates. This was a pre-cargo feature for integrating with the package manager that was accidentally never removed.
A number of bugs were fixed in the privacy checker that could cause previously-accepted code to break.
Modules and unit/tuple structs may not share the same name.
Bugs in pattern matching unit structs were fixed. The tuple struct pattern syntax (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.
A bug was fixed that causes rustc not to apply default type parameters when resolving certain method implementations of traits defined in other crates.

Version 1.5.0 (2015-12-10)

~700 changes, numerous bugfixes

Highlights

Stabilized APIs: 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.
Rust applications hosted on crates.io can be installed locally to ~/.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.
Crates with wildcard (*) dependencies will emit warnings when published. In 1.6 it will no longer be possible to publish crates with wildcard dependencies.

Breaking Changes

The rules determining when a particular lifetime must outlive a particular value (known as 'dropck') have been modified to not rely on parametricity.
Implementations of 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.
Correct a bug in Rc/Arc that caused dropck to be unaware that they could drop their content. Soundness fix.
All method invocations are properly checked for well-formedness. Soundness fix.
Traits whose supertraits contain Self are not object safe. Soundness fix.
Target specifications support a 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.
The #[inline] and #[repr] attributes can only appear in valid locations.
Native libraries linked from the local crate are passed to the linker before native libraries from upstream crates.
Two rarely-used attributes, #[no_debug] and #[omit_gdb_pretty_printer_section] are feature gated.
Negation of unsigned integers, which has been a warning for several releases, is now behind a feature gate and will generate errors.
The parser accidentally accepted visibility modifiers on enum variants, a bug which has been fixed.
A bug was fixed that allowed use statements to import unstable features.

Language

When evaluating expressions at compile-time that are not compile-time constants (const-evaluating expressions in non-const contexts), incorrect code such as overlong bitshifts and arithmetic overflow will generate a warning instead of an error, delaying the error until runtime. This will allow the const-evaluator to be expanded in the future backwards-compatibly.
The improper_ctypes lint no longer warns about using isize and usize in FFI.

Libraries

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.
There are now From conversions between floating point types where the conversions are lossless.
There are now From conversions between integer types where the conversions are lossless.
fs::Metadata implements Clone.
The parse method accepts a leading "+" when parsing integers.
AsMut is implemented for Vec.
The clone_from implementations for String and BinaryHeap have been optimized and no longer rely on the default impl.
The 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.
Dropping Vecs is much faster in unoptimized builds when the element types don't implement Drop.
A bug that caused in incorrect behavior when combining VecDeque with zero-sized types was resolved.
PartialOrd for slices is faster.

Miscellaneous

Crate metadata size was reduced by 20%.
Improvements to code generation reduced the size of libcore by 3.3 MB and rustc's memory usage by 18MB.
Improvements to deref translation increased performance in unoptimized builds.
Various errors in trait resolution are deduplicated to only be reported once.
Rust has preliminary support for rumprun kernels.
Rust has preliminary support for NetBSD on amd64.

Version 1.4.0 (2015-10-29)

~1200 changes, numerous bugfixes

Highlights

Windows builds targeting the 64-bit MSVC ABI and linker (instead of GNU) are now supported and recommended for use.

Breaking Changes

Several changes have been made to fix type soundness and improve the behavior of associated types. See RFC 1214. Although we have mostly introduced these changes as warnings this release, to become errors next release, there are still some scenarios that will see immediate breakage.
The str::lines and BufRead::lines iterators treat \r\n as line breaks in addition to \n.
Loans of '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.

Language

use statements that import multiple items can now rename them, as in use foo::{bar as kitten, baz as puppy}.
Binops work correctly on fat pointers.
pub extern crate, which does not behave as expected, issues a warning until a better solution is found.

Libraries

Many APIs were stabilized: <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.
Some APIs were deprecated: 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.
Reverse-searching strings is faster with the 'two-way' algorithm.
std::io::copy allows ?Sized arguments.
The 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.
String comparison is faster.
&mut T where T: std::fmt::Write also implements std::fmt::Write.
A stable regression in VecDeque::push_back and other capacity-altering methods that caused panics for zero-sized types was fixed.
Function pointers implement traits for up to 12 parameters.

Miscellaneous

The compiler no longer uses the 'morestack' feature to prevent stack overflow. Instead it uses guard pages and stack probes (though stack probes are not yet implemented on any platform but Windows).
The compiler matches traits faster when projections are involved.
The 'improper_ctypes' lint no longer warns about use of isize and usize.
Cargo now displays useful information about what its doing during cargo update.

Version 1.3.0 (2015-09-17)

~900 changes, numerous bugfixes

Highlights

The new object lifetime defaults have been turned on after a cycle of warnings about the change. Now types like &'a Box<Trait> (or &'a Rc<Trait>, etc) will change from being interpreted as &'a Box<Trait+'a> to &'a Box<Trait+'static>.
The Rustonomicon is a new book in the official documentation that dives into writing unsafe Rust.
The Duration API, has been stabilized. This basic unit of timekeeping is employed by other std APIs, as well as out-of-tree time crates.

Breaking Changes

The new object lifetime defaults have been turned on after a cycle of warnings about the change.
There is a known regression in how object lifetime elision is interpreted, the proper solution for which is undetermined.
The #[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.
The behavior of 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.
The 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.

Language

The new object lifetime defaults have been turned on after a cycle of warnings about the change.
Semicolons may now follow types and paths in macros.
The behavior of 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.
The dropck rules, which checks that destructors can't access destroyed values, have been updated to match the RFC.

Libraries

The 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.
The owned C string, 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.
Searching for substrings now employs the two-way algorithm instead of doing a naive search. This gives major speedups to a number of methods, including contains, find, rfind, split. starts_with and ends_with are also faster.
The performance of PartialEq for slices is much faster.
The Hash trait offers the default method, hash_slice, which is overridden and optimized by the implementations for scalars.
The Hasher trait now has a number of specialized write_* methods for primitive types, for efficiency.
The I/O-specific error type, 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.
The 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).
The Div operator is implemented for Wrapping types.
DerefMut is implemented for String.
Performance of SipHash (the default hasher for HashMap) is better for long data.
AtomicPtr implements Send.
The read_to_end implementations for Stdin and File are now specialized to use uninitialized buffers for increased performance.
Lifetime parameters of foreign functions are now resolved properly.

Misc

Rust can now, with some coercion, produce programs that run on Windows XP, though XP is not considered a supported platform.
Porting Rust on Windows from the GNU toolchain to MSVC continues (1, 2, 3, 4). It is still not recommended for use in 1.3, though should be fully-functional in the 64-bit 1.4 beta.
On Fedora-based systems installation will properly configure the dynamic linker.
The compiler gained many new extended error descriptions, which can be accessed with the --explain flag.
The 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.
Rust has preliminary support for i686 FreeBSD (it has long supported FreeBSD on x86_64).
The unused_mut, unconditional_recursion, improper_ctypes, and negate_unsigned lints are more strict.
If landing pads are disabled (with -Z no-landing-pads), panic! will kill the process instead of leaking.

Version 1.2.0 (2015-08-07)

~1200 changes, numerous bugfixes

Highlights

Dynamically-sized-type coercions allow smart pointer types like Rc to contain types without a fixed size, arrays and trait objects, finally enabling use of Rc<[T]> and completing the implementation of DST.
Parallel codegen is now working again, which can substantially speed up large builds in debug mode; It also gets another ~33% speedup when bootstrapping on a 4 core machine (using 8 jobs). It's not enabled by default, but will be "in the near future". It can be activated with the -C codegen-units=N flag to rustc.
This is the first release with experimental support for linking with the MSVC linker and lib C on Windows (instead of using the GNU variants via MinGW). It is yet recommended only for the most intrepid Rustaceans.
Benchmark compilations are showing a 30% improvement in bootstrapping over 1.1.

Breaking Changes

The 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.
The #[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 are now behind the 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.

Language

Patterns with ref mut now correctly invoke DerefMut when matching against dereferenceable values.

Libraries

The 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.
The iter::once function returns an iterator that yields a single element, and iter::empty returns an iterator that yields no elements.
The matches and rmatches methods on str return iterators over substring matches.
Cell and RefCell both implement Eq.
A number of methods for wrapping arithmetic are added to the integral types, 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.
The {:#?} 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.
It is now easier to handle poisoned locks. The 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.
On Unix the 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.

Misc

rustc employs smarter heuristics for guessing at typos.
rustc emits more efficient code for no-op conversions between unsafe pointers.
Fat pointers are now passed in pairs of immediate arguments, resulting in faster compile times and smaller code.

Version 1.1.0 (2015-06-25)

~850 changes, numerous bugfixes

Highlights

The 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.
- A symlink_metadata function has been added.
- The fs::Metadata structure now lowers to its OS counterpart, providing access to all underlying information.
The compiler now contains extended explanations of many errors. When an error with an explanation occurs the compiler suggests using the --explain flag to read the explanation. Error explanations are also available online.
Thanks to multiple improvements to type checking, as well as other work, the time to bootstrap the compiler decreased by 32%.

Libraries

The str::split_whitespace method splits a string on unicode whitespace boundaries.
On both Windows and Unix, new extension traits provide conversion of I/O types to and from the underlying system handles. On Unix, these traits are 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.
On Unix, std::os::unix::symlink creates symlinks. On Windows, symlinks can be created with std::os::windows::symlink_dir and std::os::windows::symlink_file.
The 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.
The Debug implementation for RangeFull creates output that is more consistent with other implementations.
Debug is implemented for File.
The Default implementation for Arc no longer requires Sync + Send.
The Iterator methods count, nth, and last have been overridden for slices to have O(1) performance instead of O(n).
Incorrect handling of paths on Windows has been improved in both the compiler and the standard library.
AtomicPtr gained a Default implementation.
In accordance with Rust's policy on arithmetic overflow abs now panics on overflow when debug assertions are enabled.
The Cloned iterator, which was accidentally left unstable for 1.0 has been stabilized.
The 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.
The split_off method of LinkedList no longer corrupts the list in certain scenarios.

Misc

Type checking performance has improved notably with multiple improvements.
The compiler suggests code changes for more errors.
rustc and it's build system have experimental support for building toolchains against MUSL instead of glibc on Linux.
The compiler defines the 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.
The cargo rustc command invokes a build with custom flags to rustc.
Android executables are always position independent.
The drop_with_repr_extern lint warns about mixing repr(C) with Drop.

Version 1.0.0 (2015-05-15)

~1500 changes, numerous bugfixes

Highlights

The vast majority of the standard library is now #[stable]. It is no longer possible to use unstable features with a stable build of the compiler.
Many popular crates on crates.io now work on the stable release channel.
Arithmetic on basic integer types now checks for overflow in debug builds.

Language

Several restrictions have been added to trait coherence in order to make it easier for upstream authors to change traits without breaking downstream code.
Digits of binary and octal literals are lexed more eagerly to improve error messages and macro behavior. For example, 0b1234 is now lexed as 0b1234 instead of two tokens, 0b1 and 234.
Trait bounds are always invariant, eliminating the need for the PhantomFn and MarkerTrait lang items, which have been removed.
"-" is no longer a valid character in crate names, the 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.
Lifetime shadowing is an error.
Send no longer implies 'static.
UFCS now supports trait-less associated paths like MyType::default().
Primitive types now have inherent methods, obviating the need for extension traits like SliceExt.
Methods with Self: Sized in their where clause are considered object-safe, allowing many extension traits like IteratorExt to be merged into the traits they extended.
You can now refer to associated types whose corresponding trait bounds appear only in a where clause.
The final bits of OIBIT landed, meaning that traits like Send and Sync are now library-defined.
A Reflect trait was introduced, which means that downcasting via the 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.
The unsafe_destructor feature is now deprecated in favor of the new dropck. This change is a major reduction in unsafe code.

Libraries

The thread_local module has been renamed to std::thread.
The methods of IteratorExt have been moved to the Iterator trait itself.
Several traits that implement Rust's conventions for type conversions, AsMut, AsRef, From, and Into have been centralized in the std::convert module.
The FromError trait was removed in favor of From.
The basic sleep function has moved to std::thread::sleep_ms.
The splitn function now takes an n parameter that represents the number of items yielded by the returned iterator instead of the number of 'splits'.
On Unix, all file descriptors are CLOEXEC by default.
Derived implementations of PartialOrd now order enums according to their explicitly-assigned discriminants.
Methods for searching strings are generic over Patterns, implemented presently by &char, &str, FnMut(char) -> bool and some others.
In method resolution, object methods are resolved before inherent methods.
String::from_str has been deprecated in favor of the From impl, String::from.
io::Error implements Sync.
The words method on &str has been replaced with split_whitespace, to avoid answering the tricky question, 'what is a word?'
The new path and IO modules are complete and #[stable]. This was the major library focus for this cycle.
The path API was revised to normalize ., adjusting the tradeoffs in favor of the most common usage.
A large number of remaining APIs in std were also stabilized during this cycle; about 75% of the non-deprecated API surface is now stable.
The new string pattern API landed, which makes the string slice API much more internally consistent and flexible.
A new set of generic conversion traits replaced many existing ad hoc traits.
Generic numeric traits were completely removed. This was made possible thanks to inherent methods for primitive types, and the removal gives maximal flexibility for designing a numeric hierarchy in the future.
The Fn traits are now related via inheritance and provide ergonomic blanket implementations.
The 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.

Misc

Many errors now have extended explanations that can be accessed with the --explain flag to rustc.
Many new examples have been added to the standard library documentation.
rustdoc has received a number of improvements focused on completion and polish.
Metadata was tuned, shrinking binaries by 27%.
Much headway was made on ecosystem-wide CI, making it possible to compare builds for breakage.

Version 1.0.0-alpha.2 (2015-02-20)

~1300 changes, numerous bugfixes
Highlights
- The various I/O modules were overhauled to reduce unnecessary abstractions and provide better interoperation with the underlying platform. The old io module remains temporarily at std::old_io.
- The standard library now participates in feature gating, so use of unstable libraries now requires a #![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.
- Objects now have default lifetime bounds, so you don't have to write Box<Trait+'static> when you don't care about storing references. RFC.
- In types that implement 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.
- The fully qualified ::X syntax lets you set the Self type for a trait method or associated type. RFC.
- References to types that implement Deref now automatically coerce to references to the dereferenced type U, e.g. &T where T: Deref automatically coerces to &U. This should eliminate many unsightly uses of &*, as when converting from references to vectors into references to slices. RFC.
- The explicit closure kind syntax (|&:|, |&mut:|, |:|) is obsolete and closure kind is inferred from context.
- Self is a keyword.
Libraries
- The 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)].
- Abstract OS-specific string types, std::ff::{OsString, OsStr}, provide strings in platform-specific encodings for easier interop with system APIs. RFC.
- The boxed::into_raw and Box::from_raw functions convert between Box<T> and *mut T, a common pattern for creating raw pointers.
Tooling
- Certain long error messages of the form 'expected foo found bar' are now split neatly across multiple lines. Examples in the PR.
- On Unix Rust can be uninstalled by running /usr/local/lib/rustlib/uninstall.sh.
- The #[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
- Rust is tested against a LALR grammar, which parses almost all the Rust files that rustc does.

Version 1.0.0-alpha (2015-01-09)

~2400 changes, numerous bugfixes
Highlights
- The language itself is considered feature complete for 1.0, though there will be many usability improvements and bugfixes before the final release.
- Nearly 50% of the public API surface of the standard library has been declared 'stable'. Those interfaces are unlikely to change before 1.0.
- The long-running debate over integer types has been settled: Rust will ship with types named isize and usize, rather than int and uint, for pointer-sized integers. Guidelines will be rolled out during the alpha cycle.
- Most crates that are not 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'.
- Documentation continues to be expanded with more API coverage, more examples, and more in-depth explanations. The guides have been consolidated into The Rust Programming Language.
- "Rust By Example" is now maintained by the Rust team.
- All official Rust binary installers now come with Cargo, the Rust package manager.
Language
- Closures have been completely redesigned to be implemented in terms of traits, can now be used as generic type bounds and thus monomorphized and inlined, or via an opaque pointer (boxed) as in the old system. The new system is often referred to as 'unboxed' closures.
- Traits now support associated types, allowing families of related types to be defined together and used generically in powerful ways.
- Enum variants are namespaced by their type names.
- where clauses provide a more versatile and attractive syntax for specifying generic bounds, though the previous syntax remains valid.
- Rust again picks a fallback (either i32 or f64) for uninferred numeric types.
- Rust no longer has a runtime of any description, and only supports OS threads, not green threads.
- At long last, Rust has been overhauled for 'dynamically-sized types' (DST), which integrates 'fat pointers' (object types, arrays, and str) more deeply into the type system, making it more consistent.
- Rust now has a general range syntax, 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].
- The new range syntax revealed an ambiguity in the fixed-length array syntax, so now fixed length arrays are written [T; N].
- The 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).
- Operator traits now take their operands by value, and comparison traits can use multidispatch to compare one type against multiple other types, allowing e.g. String to be compared with &str.
- if let and while let are no longer feature-gated.
- Rust has adopted a more uniform syntax for escaping unicode characters.
- 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.
- The prelude has been pared back significantly such that it is the minimum necessary to support the most pervasive code patterns, and through generalized where clauses many of the prelude extension traits have been consolidated.
- Rust's rudimentary reflection has been removed, as it incurred too much code generation for little benefit.
- Struct variants are no longer feature-gated.
- Trait bounds can be polymorphic over lifetimes. Also known as 'higher-ranked trait bounds', this crucially allows unboxed closures to work.
- Macros invocations surrounded by parens or square brackets and not terminated by a semicolon are parsed as expressions, which makes expressions like vec![1i32, 2, 3].len() work as expected.
- Trait objects now implement their traits automatically, and traits that can be coerced to objects now must be object safe.
- Automatically deriving traits is now done with #[derive(...)] not #[deriving(...)] for consistency with other naming conventions.
- Importing the containing module or enum at the same time as items or variants they contain is now done with self instead of mod, as in use foo::{self, bar}
- Glob imports are no longer feature-gated.
- The 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
- A series of efforts to establish conventions for collections types has resulted in API improvements throughout the standard library.
- New APIs for error handling provide ergonomic interop between error types, and new conventions describe more clearly the recommended error handling strategies in Rust.
- The 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.
- On Linux, OsRng prefers the new, more reliable getrandom syscall when available.
- The 'serialize' crate has been renamed 'rustc-serialize' and moved out of the distribution to Cargo. Although it is widely used now, it is expected to be superseded in the near future.
- The 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
- Flexible target specification allows rustc's code generation to be configured to support otherwise-unsupported platforms.
- Rust comes with rust-gdb and rust-lldb scripts that launch their respective debuggers with Rust-appropriate pretty-printing.
- The Windows installation of Rust is distributed with the MinGW components currently required to link binaries on that platform.
Misc
- Nullable enum optimizations have been extended to more types so that e.g. Option<Vec<T>> and Option<String> take up no more space than the inner types themselves.
- Work has begun on supporting AArch64.

Version 0.12.0 (2014-10-09)

~1900 changes, numerous bugfixes
Highlights
- The introductory documentation (now called The Rust Guide) has been completely rewritten, as have a number of supplementary guides.
- Rust's package manager, Cargo, continues to improve and is sometimes considered to be quite awesome.
- Many API's in std have been reviewed and updated for consistency with the in-development Rust coding guidelines. The standard library documentation tracks stabilization progress.
- Minor libraries have been moved out-of-tree to the rust-lang org on GitHub: uuid, semver, glob, num, hexfloat, fourcc. They can be installed with Cargo.
- Lifetime elision allows lifetime annotations to be left off of function declarations in many common scenarios.
- Rust now works on 64-bit Windows.
Language
- Indexing can be overloaded with the Index and IndexMut traits.
- The if let construct takes a branch only if the let pattern matches, currently behind the 'if_let' feature gate.
- 'where clauses', a more flexible syntax for specifying trait bounds that is more aesthetic, have been added for traits and free functions. Where clauses will in the future make it possible to constrain associated types, which would be impossible with the existing syntax.
- A new slicing syntax (e.g. [0..4]) has been introduced behind the 'slicing_syntax' feature gate, and can be overloaded with the Slice or SliceMut traits.
- The syntax for matching of sub-slices has been changed to use a postfix .. instead of prefix (.e.g. [a, b, c..]), for consistency with other uses of .. and to future-proof potential additional uses of the syntax.
- The syntax for matching inclusive ranges in patterns has changed from 0..3 to 0...4 to be consistent with the exclusive range syntax for slicing.
- Matching of sub-slices in non-tail positions (e.g. [a.., b, c]) has been put behind the 'advanced_slice_patterns' feature gate and may be removed in the future.
- Components of tuples and tuple structs can be extracted using the value.0 syntax, currently behind the tuple_indexing feature gate.
- The #[crate_id] attribute is no longer supported; versioning is handled by the package manager.
- Renaming crate imports are now written extern crate foo as bar instead of extern crate bar = foo.
- Renaming use statements are now written use foo as bar instead of use bar = foo.
- let and match bindings and argument names in macros are now hygienic.
- The new, more efficient, closure types ('unboxed closures') have been added under a feature gate, 'unboxed_closures'. These will soon replace the existing closure types, once higher-ranked trait lifetimes are added to the language.
- move has been added as a keyword, for indicating closures that capture by value.
- Mutation and assignment is no longer allowed in pattern guards.
- Generic structs and enums can now have trait bounds.
- The Share trait is now called Sync to free up the term 'shared' to refer to 'shared reference' (the default reference type.
- Dynamically-sized types have been mostly implemented, unifying the behavior of fat-pointer types with the rest of the type system.
- As part of dynamically-sized types, the 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.
- Closures can return !, as in || -> ! or proc() -> !.
- Lifetime bounds can now be applied to type parameters and object types.
- The old, reference counted GC type, Gc<T> which was once denoted by the @ sigil, has finally been removed. GC will be revisited in the future.
Libraries
- Library documentation has been improved for a number of modules.
- Bit-vectors, collections::bitv has been modernized.
- The url crate is deprecated in favor of http://github.com/servo/rust-url, which can be installed with Cargo.
- Most I/O stream types can be cloned and subsequently closed from a different thread.
- A 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.
- The runtime I/O abstraction layer that enabled the green thread scheduler to do non-thread-blocking I/O has been removed, along with the libuv-based implementation employed by the green thread scheduler. This will greatly simplify the future I/O work.
- collections::btree has been rewritten to have a more idiomatic and efficient design.
Tooling
- rustdoc output now indicates the stability levels of API's.
- The --crate-name flag can specify the name of the crate being compiled, like #[crate_name].
- The -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.
- debug info generation has continued to improve and should be more reliable under both gdb and lldb.
- rustc has experimental support for compiling in parallel using the -C codegen-units flag.
- rustc no longer encodes rpath information into binaries by default.
Misc
- Stack usage has been optimized with LLVM lifetime annotations.
- Official Rust binaries on Linux are more compatible with older kernels and distributions, built on CentOS 5.10.

Version 0.11.0 (2014-07-02)

~1700 changes, numerous bugfixes
Language
- ~[T] has been removed from the language. This type is superseded by the Vec type.
- ~str has been removed from the language. This type is superseded by the String type.
- ~T has been removed from the language. This type is superseded by the Box type.
- @T has been removed from the language. This type is superseded by the standard library's std::gc::Gc type.
- Struct fields are now all private by default.
- Vector indices and shift amounts are both required to be a uint instead of any integral type.
- Byte character, byte string, and raw byte string literals are now all supported by prefixing the normal literal with a b.
- Multiple ABIs are no longer allowed in an ABI string
- The syntax for lifetimes on closures/procedures has been tweaked slightly: <'a>|A, B|: 'b + K -> T
- Floating point modulus has been removed from the language; however it is still provided by a library implementation.
- Private enum variants are now disallowed.
- The priv keyword has been removed from the language.
- A closure can no longer be invoked through a &-pointer.
- The use foo, bar, baz; syntax has been removed from the language.
- The transmute intrinsic no longer works on type parameters.
- Statics now allow blocks/items in their definition.
- Trait bounds are separated from objects with + instead of : now.
- Objects can no longer be read while they are mutably borrowed.
- The address of a static is now marked as insignificant unless the #[inline(never)] attribute is placed it.
- The #[unsafe_destructor] attribute is now behind a feature gate.
- Struct literals are no longer allowed in ambiguous positions such as if, while, match, and for..in.
- Declaration of lang items and intrinsics are now feature-gated by default.
- Integral literals no longer default to 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.
- The Box type is no longer implicitly borrowed to &mut T.
- Procedures are now required to not capture borrowed references.
Libraries
- The standard library is now a "facade" over a number of underlying libraries. This means that development on the standard library should be speedier due to smaller crates, as well as a clearer line between all dependencies.
- A new library, libcore, lives under the standard library's facade which is Rust's "0-assumption" library, suitable for embedded and kernel development for example.
- A regex crate has been added to the standard distribution. This crate includes statically compiled regular expressions.
- The unwrap/unwrap_err methods on Result require a Show bound for better error messages.
- The return types of the std::comm primitives have been centralized around the Result type.
- A number of I/O primitives have gained the ability to time out their operations.
- A number of I/O primitives have gained the ability to close their reading/writing halves to cancel pending operations.
- Reverse iterator methods have been removed in favor of rev() on their forward-iteration counterparts.
- A bitflags! macro has been added to enable easy interop with C and management of bit flags.
- A debug_assert! macro is now provided which is disabled when --cfg ndebug is passed to the compiler.
- A graphviz crate has been added for creating .dot files.
- The std::cast module has been migrated into std::mem.
- The std::local_data api has been migrated from freestanding functions to being based on methods.
- The Pod trait has been renamed to Copy.
- jemalloc has been added as the default allocator for types.
- The API for allocating memory has been changed to use proper alignment and sized deallocation
- Connecting a TcpStream or binding a TcpListener is now based on a string address and a u16 port. This allows connecting to a hostname as opposed to an IP.
- The Reader trait now contains a core method, read_at_least(), which correctly handles many repeated 0-length reads.
- The process-spawning API is now centered around a builder-style Command struct.
- The :? printing qualifier has been moved from the standard library to an external libdebug crate.
- Eq/Ord have been renamed to PartialEq/PartialOrd. TotalEq/TotalOrd have been renamed to Eq/Ord.
- The select/plural methods have been removed from format!. The escapes for { and } have also changed from { and } to {{ and }}, respectively.
- The TaskBuilder API has been re-worked to be a true builder, and extension traits for spawning native/green tasks have been added.
Tooling
- All breaking changes to the language or libraries now have their commit message annotated with [breaking-change] to allow for easy discovery of breaking changes.
- The compiler will now try to suggest how to annotate lifetimes if a lifetime-related error occurs.
- Debug info continues to be improved greatly with general bug fixes and better support for situations like link time optimization (LTO).
- Usage of syntax extensions when cross-compiling has been fixed.
- Functionality equivalent to GCC & Clang's -ffunction-sections, -fdata-sections and --gc-sections has been enabled by default
- The compiler is now stricter about where it will load module files from when a module is declared via mod foo;.
- The #[phase(syntax)] attribute has been renamed to #[phase(plugin)]. Syntax extensions are now discovered via a "plugin registrar" type which will be extended in the future to other various plugins.
- Lints have been restructured to allow for dynamically loadable lints.
- A number of rustdoc improvements:
  - The HTML output has been visually redesigned.
  - Markdown is now powered by hoedown instead of sundown.
  - Searching heuristics have been greatly improved.
  - The search index has been reduced in size by a great amount.
  - Cross-crate documentation via pub use has been greatly improved.
  - Primitive types are now hyperlinked and documented.
- Documentation has been moved from static.rust-lang.org/doc to doc.rust-lang.org
- A new sandbox, play.rust-lang.org, is available for running and sharing rust code examples on-line.
- Unused attributes are now more robustly warned about.
- The dead_code lint now warns about unused struct fields.
- Cross-compiling to iOS is now supported.
- Cross-compiling to mipsel is now supported.
- Stability attributes are now inherited by default and no longer apply to intra-crate usage, only inter-crate usage.
- Error message related to non-exhaustive match expressions have been greatly improved.

Version 0.10 (2014-04-03)

~1500 changes, numerous bugfixes
Language
- A new RFC process is now in place for modifying the language.
- Patterns with @-pointers have been removed from the language.
- Patterns with unique vectors (~[T]) have been removed from the language.
- Patterns with unique strings (~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.
- Headers on ~ allocations which contain @ boxes inside the type for reference counting have been removed.
- The semantics around the lifetimes of temporary expressions have changed, see #3511 and #11585 for more information.
- Cross-crate syntax extensions are now possible, but feature gated. See #11151 for more information. This includes both macro_rules! macros as well as syntax extensions such as format!.
- New lint modes have been added, and older ones have been turned on to be warn-by-default.
  - Unnecessary parentheses
  - Uppercase statics
  - Camel Case types
  - Uppercase variables
  - Publicly visible private types
  - #[deriving] with raw pointers
- Unsafe functions can no longer be coerced to closures.
- Various obscure macros such as log_syntax! are now behind feature gates.
- The #[simd] attribute is now behind a feature gate.
- Visibility is no longer allowed on extern crate statements, and unnecessary visibility (priv) is no longer allowed on use statements.
- Trailing commas are now allowed in argument lists and tuple patterns.
- The do keyword has been removed, it is now a reserved keyword.
- Default type parameters have been implemented, but are feature gated.
- Borrowed variables through captures in closures are now considered soundly.
- extern mod is now extern crate
- The Freeze trait has been removed.
- The Share trait has been added for types that can be shared among threads.
- Labels in macros are now hygienic.
- Expression/statement macro invocations can be delimited with {} now.
- Treatment of types allowed in static mut locations has been tweaked.
- The * and . operators are now overloadable through the Deref and DerefMut traits.
- ~Trait and proc no longer have Send bounds by default.
- Partial type hints are now supported with the _ type marker.
- An Unsafe type was introduced for interior mutability. It is now considered undefined to transmute from &T to &mut T without using the Unsafe type.
- The #[linkage] attribute was implemented for extern statics/functions.
- The inner attribute syntax has changed from #[foo]; to #![foo].
- Pod was renamed to Copy.
Libraries
- The 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: 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.
- std: The vec module has been renamed to slice.
- std: A new vector type, Vec<T>, has been added in preparation for DST. This will become the only growable vector in the future.
- std: 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.
- std: print and println are no longer in the prelude, the print! and println! macros are intended to be used instead.
- std: Rc now has a Weak pointer for breaking cycles, and it no longer attempts to statically prevent cycles.
- std: The standard distribution is adopting the policy of pushing failure to the user rather than failing in libraries. Many functions (such as slice::last()) now return Option<T> instead of T + failing.
- std: fmt::Default has been renamed to fmt::Show, and it now has a new deriving mode: #[deriving(Show)].
- std: ToStr is now implemented for all types implementing Show.
- std: The formatting trait methods now take &self instead of &T
- std: The invert() method on iterators has been renamed to rev()
- std: std::num has seen a reduction in the genericity of its traits, consolidating functionality into a few core traits.
- std: Backtraces are now printed on task failure if the environment variable RUST_BACKTRACE is present.
- std: Naming conventions for iterators have been standardized. More details can be found on the wiki's style guide.
- std: eof() has been removed from the Reader trait. Specific types may still implement the function.
- std: Networking types are now cloneable to allow simultaneous reads/writes.
- std: assert_approx_eq! has been removed
- std: The e and E formatting specifiers for floats have been added to print them in exponential notation.
- std: The Times trait has been removed
- std: Indications of variance and opting out of builtin bounds is done through marker types in std::kinds::marker now
- std: hash has been rewritten, IterBytes has been removed, and #[deriving(Hash)] is now possible.
- std: SharedChan has been removed, Sender is now cloneable.
- std: Chan and Port were renamed to Sender and Receiver.
- std: Chan::new is now channel().
- std: A new synchronous channel type has been implemented.
- std: A select! macro is now provided for selecting over Receivers.
- std: hashmap and trie have been moved to libcollections
- std: run has been rolled into io::process
- std: assert_eq! now uses {} instead of {:?}
- std: The equality and comparison traits have seen some reorganization.
- std: rand has moved to librand.
- std: to_{lower,upper}case has been implemented for char.
- std: Logging has been moved to liblog.
- collections: HashMap has been rewritten for higher performance and less memory usage.
- native: The default runtime is now libnative. If libgreen is desired, it can be booted manually. The runtime guide has more information and examples.
- native: All I/O functionality except signals has been implemented.
- green: Task spawning with libgreen has been optimized with stack caching and various trimming of code.
- green: Tasks spawned by libgreen now have an unmapped guard page.
- sync: The extra::sync module has been updated to modern rust (and moved to the sync library), tweaking and improving various interfaces while dropping redundant functionality.
- sync: A new Barrier type has been added to the sync library.
- sync: An efficient mutex for native and green tasks has been implemented.
- serialize: The base64 module has seen some improvement. It treats newlines better, has non-string error values, and has seen general cleanup.
- fourcc: A fourcc! macro was introduced
- hexfloat: A hexfloat! 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.
- Nightly builds of rust are now available
- The memory usage of rustc has been improved many times throughout this release cycle.
- The build process supports disabling rpath support for the rustc binary itself.
- Code generation has improved in some cases, giving more information to the LLVM optimization passes to enable more extensive optimizations.
- Debuginfo compatibility with lldb on OSX has been restored.
- The master branch is now gated on an android bot, making building for android much more reliable.
- Output flags have been centralized into one --emit flag.
- Crate type flags have been centralized into one --crate-type flag.
- Codegen flags have been consolidated behind a -C flag.
- Linking against outdated crates now has improved error messages.
- Error messages with lifetimes will often suggest how to annotate the function to fix the error.
- Many more types are documented in the standard library, and new guides were written.
- Many rustdoc improvements:
  - code blocks are syntax highlighted.
  - render standalone markdown files.
  - the --test flag tests all code blocks by default.
  - exported macros are displayed.
  - re-exported types have their documentation inlined at the location of the first re-export.
  - search works across crates that have been rendered to the same output directory.

Version 0.9 (2014-01-09)

~1800 changes, numerous bugfixes
Language
- The float type has been removed. Use f32 or f64 instead.
- A new facility for enabling experimental features (feature gating) has been added, using the crate-level #[feature(foo)] attribute.
- Managed boxes (@) are now behind a feature gate (#[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.
- Jumping back to the top of a loop is now done with continue instead of loop.
- Strings can no longer be mutated through index assignment.
- Raw strings can be created via the basic 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.
- The &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.
- Single-element tuple-like structs can no longer be dereferenced to obtain the inner value. A more comprehensive solution for overloading the dereference operator will be provided in the future.
- The #[link(...)] attribute has been replaced with #[crate_id = "name#vers"].
- Empty impls must be terminated with empty braces and may not be terminated with a semicolon.
- Keywords are no longer allowed as lifetime names; the self lifetime no longer has any special meaning.
- The old 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);.
- The extern mod foo (name = "bar") syntax has been removed. Use extern mod foo = "bar" instead.
- New reserved keywords: alignof, offsetof, sizeof.
- Macros can have attributes.
- Macros can expand to items with attributes.
- Macros can expand to multiple items.
- The asm! macro is feature-gated (#[feature(asm)]).
- Comments may be nested.
- Values automatically coerce to trait objects they implement, without an explicit as.
- Enum discriminants are no longer an entire word but as small as needed to contain all the variants. The repr attribute can be used to override the discriminant size, as in #[repr(int)] for integer-sized, and #[repr(C)] to match C enums.
- Non-string literals are not allowed in attributes (they never worked).
- The FFI now supports variadic functions.
- Octal numeric literals, as in 0o7777.
- The concat! syntax extension performs compile-time string concatenation.
- The #[fixed_stack_segment] and #[rust_stack] attributes have been removed as Rust no longer uses segmented stacks.
- Non-ascii identifiers are feature-gated (#[feature(non_ascii_idents)]).
- Ignoring all fields of an enum variant or tuple-struct is done with .., 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.
- The type_overflow lint (default: warn) checks literals for overflow.
- The unsafe_block lint (default: allow) checks for usage of unsafe.
- The attribute_usage lint (default: warn) warns about unknown attributes.
- The unknown_features lint (default: warn) warns about unknown feature gates.
- The dead_code lint (default: warn) checks for dead code.
- Rust libraries can be linked statically to one another
- #[link_args] is behind the link_args feature gate.
- Native libraries are now linked with #[link(name = "foo")]
- Native libraries can be statically linked to a rust crate (#[link(name = "foo", kind = "static")]).
- Native OS X frameworks are now officially supported (#[link(name = "foo", kind = "framework")]).
- The #[thread_local] attribute creates thread-local (not task-local) variables. Currently behind the thread_local feature gate.
- The return keyword may be used in closures.
- Types that can be copied via a memcpy implement the Pod kind.
- The cfg attribute can now be used on struct fields and enum variants.
Libraries
- std: The option and result API's have been overhauled to make them simpler, more consistent, and more composable.
- std: The entire 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.
- std: io::util contains a number of useful implementations of Reader and Writer, including NullReader, NullWriter, ZeroReader, TeeReader.
- std: The reference counted pointer type extra::rc moved into std.
- std: The Gc type in the gc module will replace @ (it is currently just a wrapper around it).
- std: The Either type has been removed.
- std: fmt::Default can be implemented for any type to provide default formatting to the format! macro, as in format!("{}", myfoo).
- std: The rand API continues to be tweaked.
- std: The rust_begin_unwind function, useful for inserting breakpoints on failure in gdb, is now named rust_fail.
- std: The each_key and each_value methods on HashMap have been replaced by the keys and values iterators.
- std: Functions dealing with type size and alignment have moved from the sys module to the mem module.
- std: The path module was written and API changed.
- std: str::from_utf8 has been changed to cast instead of allocate.
- std: starts_with and ends_with methods added to vectors via the ImmutableEqVector trait, which is in the prelude.
- std: Vectors can be indexed with the get_opt method, which returns None if the index is out of bounds.
- std: Task failure no longer propagates between tasks, as the model was complex, expensive, and incompatible with thread-based tasks.
- std: The Any type can be used for dynamic typing.
- std: ~Any can be passed to the fail! macro and retrieved via task::try.
- std: Methods that produce iterators generally do not have an _iter suffix now.
- std: cell::Cell and cell::RefCell can be used to introduce mutability roots (mutable fields, etc.). Use instead of e.g. @mut.
- std: util::ignore renamed to prelude::drop.
- std: Slices have sort and sort_by methods via the MutableVector trait.
- std: vec::raw has seen a lot of cleanup and API changes.
- std: The standard library no longer includes any C++ code, and very minimal C, eliminating the dependency on libstdc++.
- std: Runtime scheduling and I/O functionality has been factored out into extensible interfaces and is now implemented by two different crates: libnative, for native threading and I/O; and libgreen, for green threading and I/O. This paves the way for using the standard library in more limited embedded environments.
- std: The comm module has been rewritten to be much faster, have a simpler, more consistent API, and to work for both native and green threading.
- std: All libuv dependencies have been moved into the rustuv crate.
- native: New implementations of runtime scheduling on top of OS threads.
- native: New native implementations of TCP, UDP, file I/O, process spawning, and other I/O.
- green: The green thread scheduler and message passing types are almost entirely lock-free.
- extra: The flatpipes module had bitrotted and was removed.
- extra: All crypto functions have been removed and Rust now has a policy of not reimplementing crypto in the standard library. In the future crypto will be provided by external crates with bindings to established libraries.
- extra: c_vec has been modernized.
- extra: The sort module has been removed. Use the sort method on mutable slices.
Tooling
- The 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.
- Executables and static libraries can be built with LTO (-Z lto)
- rustc adds a --dep-info flag for communicating dependencies to build tools.

Version 0.8 (2013-09-26)

~2200 changes, numerous bugfixes
Language
- The for loop syntax has changed to work with the Iterator trait.
- At long last, unwinding works on Windows.
- Default methods are ready for use.
- Many trait inheritance bugs fixed.
- Owned and borrowed trait objects work more reliably.
- copy is no longer a keyword. It has been replaced by the Clone trait.
- rustc can omit emission of code for the debug! macro if it is passed --cfg ndebug
- mod.rs is now "blessed". When loading mod foo;, rustc will now look for foo.rs, then foo/mod.rs, and will generate an error when both are present.
- Strings no longer contain trailing nulls. The new std::c_str module provides new mechanisms for converting to C strings.
- The type of foreign functions is now extern "C" fn instead of `*u8'.
- The FFI has been overhauled such that foreign functions are called directly, instead of through a stack-switching wrapper.
- Calling a foreign function must be done through a Rust function with the #[fixed_stack_segment] attribute.
- The 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.
- Casting to 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.
- Crates may be imported by URL with extern mod foo = "url";.
- Explicit enum discriminants may be given as uints as in enum E { V = 0u }
- Static vectors can be initialized with repeating elements, e.g. static foo: [u8, .. 100]: [0, .. 100];.
- Static structs can be initialized with functional record update, e.g. static foo: Foo = Foo { a: 5, .. bar };.
- cfg! can be used to conditionally execute code based on the crate configuration, similarly to #[cfg(...)].
- The unnecessary_qualification lint detects unneeded module prefixes (default: allow).
- Arithmetic operations have been implemented on the SIMD types in std::unstable::simd.
- Exchange allocation headers were removed, reducing memory usage.
- 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.
- The library section in which a function or static is placed may be specified with #[link_section = "..."].
- The proto! syntax extension for defining bounded message protocols was removed.
- macro_rules! is hygienic for let declarations.
- The #[export_name] attribute specifies the name of a symbol.
- unreachable! can be used to indicate unreachable code, and fails if executed.
Libraries
- std: Transitioned to the new runtime, written in Rust.
- std: Added an experimental I/O library, rt::io, based on the new runtime.
- std: A new generic range function was added to the prelude, replacing uint::range and friends.
- std: range_rev no longer exists. Since range is an iterator it can be reversed with range(lo, hi).invert().
- std: The chain method on option renamed to and_then; unwrap_or_default renamed to unwrap_or.
- std: The iterator module was renamed to iter.
- std: Integral types now support the checked_add, checked_sub, and checked_mul operations for detecting overflow.
- std: Many methods in str, vec, option, result` were renamed for consistency.
- std: Methods are standardizing on conventions for casting methods: to_foo for copying, into_foo for moving, as_foo for temporary and cheap casts.
- std: The CString type in c_str provides new ways to convert to and from C strings.
- std: DoubleEndedIterator can yield elements in two directions.
- std: The mut_split method on vectors partitions an &mut [T] into two splices.
- std: str::from_bytes renamed to str::from_utf8.
- std: pop_opt and shift_opt methods added to vectors.
- std: The task-local data interface no longer uses @, and keys are no longer function pointers.
- std: The swap_unwrap method of Option renamed to take_unwrap.
- std: Added SharedPort to comm.
- std: Eq has a default method for ne; only eq is required in implementations.
- std: Ord has default methods for le, gt and ge; only lt is required in implementations.
- std: is_utf8 performance is improved, impacting many string functions.
- std: os::MemoryMap provides cross-platform mmap.
- std: ptr::offset is now unsafe, but also more optimized. Offsets that are not 'in-bounds' are considered undefined.
- std: Many freestanding functions in vec removed in favor of methods.
- std: Many freestanding functions on scalar types removed in favor of methods.
- std: Many options to task builders were removed since they don't make sense in the new scheduler design.
- std: More containers implement FromIterator so can be created by the collect method.
- std: More complete atomic types in unstable::atomics.
- std: comm::PortSet removed.
- std: Mutating methods in the 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.
- std: Various from_str functions were removed in favor of a generic from_str which is available in the prelude.
- std: util::unreachable removed in favor of the unreachable! macro.
- extra: dlist, the doubly-linked list was modernized.
- extra: Added a hex module with ToHex and FromHex traits.
- extra: Added glob module, replacing std::os::glob.
- extra: rope was removed.
- extra: deque was renamed to ringbuf. RingBuf implements Deque.
- extra: net, and timer were removed. The experimental replacements are std::rt::io::net and std::rt::io::timer.
- extra: Iterators implemented for SmallIntMap.
- extra: Iterators implemented for Bitv and BitvSet.
- extra: SmallIntSet removed. Use BitvSet.
- extra: Performance of JSON parsing greatly improved.
- extra: semver updated to SemVer 2.0.0.
- extra: term handles more terminals correctly.
- extra: dbg module removed.
- extra: par module removed.
- extra: future was cleaned up, with some method renames.
- extra: Most free functions in getopts were converted to methods.
Other
- rustc's debug info generation (-Z debug-info) is greatly improved.
- rustc accepts --target-cpu to compile to a specific CPU architecture, similarly to gcc's --march flag.
- rustc's performance compiling small crates is much better.
- rustpkg has received many improvements.
- rustpkg supports git tags as package IDs.
- rustpkg builds into target-specific directories so it can be used for cross-compiling.
- The number of concurrent test tasks is controlled by the environment variable RUST_TEST_TASKS.
- The test harness can now report metrics for benchmarks.
- All tools have man pages.
- Programs compiled with --test now support the -h and --help flags.
- The runtime uses jemalloc for allocations.
- Segmented stacks are temporarily disabled as part of the transition to the new runtime. Stack overflows are possible!
- A new documentation backend, rustdoc_ng, is available for use. It is still invoked through the normal rustdoc command.

Version 0.7 (2013-07-03)

~2000 changes, numerous bugfixes
Language
- impls no longer accept a visibility qualifier. Put them on methods instead.
- The borrow checker has been rewritten with flow-sensitivity, fixing many bugs and inconveniences.
- The self parameter no longer implicitly means &'self self, and can be explicitly marked with a lifetime.
- Overloadable compound operators (+=, etc.) have been temporarily removed due to bugs.
- The for loop protocol now requires for-iterators to return bool so they compose better.
- The Durable trait is replaced with the 'static bounds.
- Trait default methods work more often.
- Structs with the #[packed] attribute have byte alignment and no padding between fields.
- Type parameters bound by Copy must now be copied explicitly with the copy keyword.
- It is now illegal to move out of a dereferenced unsafe pointer.
- Option<~T> is now represented as a nullable pointer.
- @mut does dynamic borrow checks correctly.
- The main function is only detected at the topmost level of the crate. The #[main] attribute is still valid anywhere.
- Struct fields may no longer be mutable. Use inherited mutability.
- The #[no_send] attribute makes a type that would otherwise be Send, not.
- The #[no_freeze] attribute makes a type that would otherwise be Freeze, not.
- Unbounded recursion will abort the process after reaching the limit specified by the RUST_MAX_STACK environment variable (default: 1GB).
- The vecs_implicitly_copyable lint mode has been removed. Vectors are never implicitly copyable.
- #[static_assert] makes compile-time assertions about static bools.
- At long last, 'argument modes' no longer exist.
- The rarely used 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(...)].
- The bytes! macro returns a vector of bytes for string, u8, char, and unsuffixed integer literals.
Libraries
- The core crate was renamed to std.
- The std crate was renamed to extra.
- More and improved documentation.
- std: iterator module for external iterator objects.
- Many old-style (internal, higher-order function) iterators replaced by implementations of Iterator.
- std: Many old internal vector and string iterators, incl. any, all. removed.
- std: The finalize method of Drop renamed to drop.
- std: The drop method now takes &mut self instead of &self.
- std: The prelude no longer re-exports any modules, only types and traits.
- std: Prelude additions: print, println, FromStr, ApproxEq, Equiv, Iterator, IteratorUtil, many numeric traits, many tuple traits.
- std: New numeric traits: Fractional, Real, RealExt, Integer, Ratio, Algebraic, Trigonometric, Exponential, Primitive.
- std: Tuple traits and accessors defined for up to 12-tuples, e.g. (0, 1, 2).n2() or (0, 1, 2).n2_ref().
- std: Many types implement Clone.
- std: path type renamed to Path.
- std: mut module and Mut type removed.
- std: Many standalone functions removed in favor of methods and iterators in vec, str. In the future methods will also work as functions.
- std: reinterpret_cast removed. Use transmute.
- std: ascii string handling in std::ascii.
- std: Rand is implemented for ~/@.
- std: run module for spawning processes overhauled.
- std: Various atomic types added to unstable::atomic.
- std: Various types implement Zero.
- std: LinearMap and LinearSet renamed to HashMap and HashSet.
- std: Borrowed pointer functions moved from ptr to borrow.
- std: Added os::mkdir_recursive.
- std: Added os::glob function performs filesystems globs.
- std: FuzzyEq renamed to ApproxEq.
- std: Map now defines pop and swap methods.
- std: Cell constructors converted to static methods.
- extra: rc module adds the reference counted pointers, Rc and RcMut.
- extra: flate module moved from std to extra.
- extra: fileinput module for iterating over a series of files.
- extra: Complex number type and complex module.
- extra: Rational number type and rational module.
- extra: BigInt, BigUint implement numeric and comparison traits.
- extra: term uses terminfo now, is more correct.
- extra: arc functions converted to methods.
- extra: Implementation of fixed output size variations of SHA-2.
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).
- The rusti command has been rewritten and a number of bugs addressed.
- rustc outputs in color on more terminals.
- rustc accepts a --link-args flag to pass arguments to the linker.
- rustc accepts a -Z print-link-args flag for debugging linkage.
- Compiling with -g will make the binary record information about dynamic borrowcheck failures for debugging.
- rustdoc has a nicer stylesheet.
- Various improvements to rustdoc.
- Improvements to rustpkg (see the detailed release notes).

Version 0.6 (2013-04-03)

~2100 changes, numerous bugfixes
Syntax changes
- The self type parameter in traits is now spelled Self
- The self parameter in trait and impl methods must now be explicitly named (for example: fn f(&self) { }). Implicit self is deprecated.
- Static methods no longer require the static keyword and instead are distinguished by the lack of a self parameter
- Replaced the Durable trait with the 'static lifetime
- The old closure type syntax with the trailing sigil has been removed in favor of the more consistent leading sigil
- super is a keyword, and may be prefixed to paths
- Trait bounds are separated with + instead of whitespace
- Traits are implemented with impl Trait for Type instead of impl Type: Trait
- Lifetime syntax is now &'l foo instead of &l/foo
- The export keyword has finally been removed
- The move keyword has been removed (see "Semantic changes")
- The interior mutability qualifier on vectors, [mut T], has been removed. Use &mut [T], etc.
- mut is no longer valid in ~mut T. Use inherited mutability
- fail is no longer a keyword. Use fail!()
- assert is no longer a keyword. Use assert!()
- log is no longer a keyword. use debug!, etc.
- 1-tuples may be represented as (T,)
- Struct fields may no longer be mut. Use inherited mutability, @mut T, core::mut or core::cell
- extern mod { ... } is no longer valid syntax for foreign function modules. Use extern blocks: extern { ... }
- Newtype enums removed. Use tuple-structs.
- Trait implementations no longer support visibility modifiers
- Pattern matching over vectors improved and expanded
- const renamed to static to correspond to lifetime name, and make room for future static mut unsafe mutable globals.
- Replaced #[deriving_eq] with #[deriving(Eq)], etc.
- Clone implementations can be automatically generated with #[deriving(Clone)]
- Casts to traits must use a pointer sigil, e.g. @foo as @Bar instead of foo as Bar.
- Fixed length vector types are now written as [int, .. 3] instead of [int * 3].
- Fixed length vector types can express the length as a constant expression. (ex: [int, .. GL_BUFFER_SIZE - 2])
Semantic changes
- Types with owned pointers or custom destructors move by default, eliminating the move keyword
- All foreign functions are considered unsafe
- &mut is now unaliasable
- Writes to borrowed @mut pointers are prevented dynamically
- () has size 0
- The name of the main function can be customized using #[main]
- The default type of an inferred closure is &fn instead of @fn
- use statements may no longer be "chained" - they cannot import identifiers imported by previous use statements
- use 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.
- Method visibility is inherited from the implementation declaration
- Structural records have been removed
- Many more types can be used in static items, including enums 'static-lifetime pointers and vectors
- Pattern matching over vectors improved and expanded
- Typechecking of closure types has been overhauled to improve inference and eliminate unsoundness
- Macros leave scope at the end of modules, unless that module is tagged with #[macro_escape]
Libraries
- Added big integers to std::bigint
- Removed core::oldcomm module
- Added pipe-based core::comm module
- Numeric traits have been reorganized under core::num
- vec::slice finally returns a slice
- debug! and friends don't require a format string, e.g. debug!(Foo)
- Containers reorganized around traits in core::container
- core::dvec removed, ~[T] is a drop-in replacement
- core::send_map renamed to core::hashmap
- std::map removed; replaced with core::hashmap
- std::treemap reimplemented as an owned balanced tree
- std::deque and std::smallintmap reimplemented as owned containers
- core::trie added as a fast ordered map for integer keys
- Set types added to core::hashmap, core::trie and std::treemap
- Ord split into Ord and TotalOrd. Ord is still used to overload the comparison operators, whereas TotalOrd is used by certain container types
Other
- Replaced the 'cargo' package manager with 'rustpkg'
- Added all-purpose 'rust' tool
- rustc --test now supports benchmarks with the #[bench] attribute
- rustc now attempts to offer spelling suggestions
- Improved support for ARM and Android
- Preliminary MIPS backend
- Improved foreign function ABI implementation for x86, x86_64
- Various memory usage improvements
- Rust code may be embedded in foreign code under limited circumstances
- Inline assembler supported by new asm!() syntax extension.

Version 0.5 (2012-12-21)

~900 changes, numerous bugfixes
Syntax changes
- Removed <- move operator
- Completed the transition from the #fmt extension syntax to fmt!
- Removed old fixed length vector syntax - [T]/N
- New token-based quasi-quoters, quote_tokens!, quote_expr!, etc.
- Macros may now expand to items and statements
- a.b() is always parsed as a method call, never as a field projection
- Eq and IterBytes implementations can be automatically generated with #[deriving_eq] and #[deriving_iter_bytes] respectively
- Removed the special crate language for .rc files
- Function arguments may consist of any irrefutable pattern
Semantic changes
- & and ~ pointers may point to objects
- Tuple structs - struct Foo(Bar, Baz). Will replace newtype enums.
- Enum variants may be structs
- Destructors can be added to all nominal types with the Drop trait
- Structs and nullary enum variants may be constants
- Values that cannot be implicitly copied are now automatically moved without writing move explicitly
- &T may now be coerced to *T
- Coercions happen in let statements as well as function calls
- use statements now take crate-relative paths
- The module and type namespaces have been merged so that static method names can be resolved under the trait in which they are declared
Improved support for language features
- Trait inheritance works in many scenarios
- More support for explicit self arguments in methods - self, &self @self, and ~self all generally work as expected
- Static methods work in more situations
- Experimental: Traits may declare default methods for the implementations to use
Libraries
- New condition handling system in core::condition
- Timsort added to std::sort
- New priority queue, std::priority_queue
- Pipes for serializable types, `std::flatpipes'
- Serialization overhauled to be trait-based
- Expanded getopts definitions
- Moved futures to std
- More functions are pure now
- core::comm renamed to oldcomm. Still deprecated
- rustdoc and cargo are libraries now
Misc
- Added a preliminary REPL, rusti
- License changed from MIT to dual MIT/APL2

Version 0.4 (2012-10-15)

~2000 changes, numerous bugfixes
Syntax
- All keywords are now strict and may not be used as identifiers anywhere
- Keyword removal: 'again', 'import', 'check', 'new', 'owned', 'send', 'of', 'with', 'to', 'class'.
- Classes are replaced with simpler structs
- Explicit method self types
- ret became return and alt became match
- import is now use; use is now extern mod`
- extern mod { ... } is now extern { ... }
- use mod is the recommended way to import modules
- pub and priv replace deprecated export lists
- The syntax of match pattern arms now uses fat arrow (=>)
- main no longer accepts an args vector; use os::args instead
Semantics
- Trait implementations are now coherent, ala Haskell typeclasses
- Trait methods may be static
- Argument modes are deprecated
- Borrowed pointers are much more mature and recommended for use
- Strings and vectors in the static region are stored in constant memory
- Typestate was removed
- Resolution rewritten to be more reliable
- Support for 'dual-mode' data structures (freezing and thawing)
Libraries
- Most binary operators can now be overloaded via the traits in `core::ops'
- std::net::url for representing URLs
- Sendable hash maps in core::send_map
- `core::task' gained a (currently unsafe) task-local storage API
Concurrency
- An efficient new intertask communication primitive called the pipe, along with a number of higher-level channel types, in core::pipes
- std::arc, an atomically reference counted, immutable, shared memory type
- std::sync, various exotic synchronization tools based on arcs and pipes
- Futures are now based on pipes and sendable
- More robust linked task failure
- Improved task builder API
Other
- Improved error reporting
- Preliminary JIT support
- Preliminary work on precise GC
- Extensive architectural improvements to rustc
- Begun a transition away from buggy C++-based reflection (shape) code to Rust-based (visitor) code
- All hash functions and tables converted to secure, randomized SipHash

Version 0.3 (2012-07-12)

~1900 changes, numerous bugfixes
New coding conveniences
- Integer-literal suffix inference
- Per-item control over warnings, errors
- #[cfg(windows)] and #[cfg(unix)] attributes
- Documentation comments
- More compact closure syntax
- 'do' expressions for treating higher-order functions as control structures
- *-patterns (wildcard extended to all constructor fields)
Semantic cleanup
- Name resolution pass and exhaustiveness checker rewritten
- Region pointers and borrow checking supersede alias analysis
- Init-ness checking is now provided by a region-based liveness pass instead of the typestate pass; same for last-use analysis
- Extensive work on region pointers
Experimental new language features
- Slices and fixed-size, interior-allocated vectors
- #!-comments for lang versioning, shell execution
- Destructors and iface implementation for classes; type-parameterized classes and class methods
- 'const' type kind for types that can be used to implement shared-memory concurrency patterns
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
- Syntax-layer of compiler split into separate crate
- Clang (from LLVM project) integrated into build
- Typechecker split into sub-modules
New library code
- New time functions
- Extension methods for many built-in types
- Arc: atomic-refcount read-only / exclusive-use shared cells
- Par: parallel map and search routines
- Extensive work on libuv interface
- Much vector code moved to libraries
- Syntax extensions: #line, #col, #file, #mod, #stringify, #include, #include_str, #include_bin
Tool improvements
- Cargo automatically resolves dependencies

Version 0.2 (2012-03-29)

1500 changes, numerous bugfixes
New docs and doc tooling
New port: FreeBSD x86_64
Compilation model enhancements
- Generics now specialized, multiply instantiated
- Functions now inlined across separate crates
Scheduling, stack and threading fixes
- Noticeably improved message-passing performance
- Explicit schedulers
- Callbacks from C
- Helgrind clean
Experimental new language features
- Operator overloading
- Region pointers
- Classes
Various language extensions
- C-callback function types: 'crust fn ...'
- Infinite-loop construct: 'loop { ... }'
- Shorten 'mutable' to 'mut'
- Required mutable-local qualifier: 'let mut ...'
- Basic glob-exporting: 'export foo::*;'
- Alt now exhaustive, 'alt check' for runtime-checked
- Block-function form of 'for' loop, with 'break' and 'ret'.
New library code
- AST quasi-quote syntax extension
- Revived libuv interface
- New modules: core::{future, iter}, std::arena
- Merged per-platform std::{os*, fs*} to core::{libc, os}
- Extensive cleanup, regularization in libstd, libcore

Version 0.1 (2012-01-20)

Most language features work, including:
- Unique pointers, unique closures, move semantics
- Interface-constrained generics
- Static interface dispatch
- Stack growth
- Multithread task scheduling
- Typestate predicates
- Failure unwinding, destructors
- Pattern matching and destructuring assignment
- Lightweight block-lambda syntax
- Preliminary macro-by-example
Compiler works with the following configurations:
- Linux: x86 and x86_64 hosts and targets
- macOS: x86 and x86_64 hosts and targets
- Windows: x86 hosts and targets
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.

Footnotes

https://doc.rust-lang.org/nightly/rustc/check-cfg.html ↩

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