Rust 1.8.0

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...

Rust 1.7.0

Libraries

• Stabilized APIs
  • Path
    • Path::strip_prefix (renamed from relative_from)
    • path::StripPrefixError (new error type returned from strip_prefix)
  • Ipv4Addr
    • Ipv4Addr::is_loopback
    • Ipv4Addr::is_private
    • Ipv4Addr::is_link_local
    • Ipv4Addr::is_multicast
    • Ipv4Addr::is_broadcast
    • Ipv4Addr::is_documentation
  • Ipv6Addr
    • Ipv6Addr::is_unspecified
    • Ipv6Addr::is_loopback
    • Ipv6Addr::is_multicast
  • 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
    • std::hash::BuildHasher
    • BuildHasher::Hasher
    • BuildHasher::build_hasher
    • std::hash::BuildHasherDefault
    • HashMap::with_hasher
    • HashMap::with_capacity_and_hasher
    • HashSet::with_hasher
    • HashSet::with_capacity_and_hasher
    • std::collections::hash_map::RandomState
    • RandomState::new
• 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 br...

Rust 1.6.0

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.

Rust 1.5.0

• ~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 implement...

Rust 1.4.0

• ~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.

Rust 1.3.0

• ~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 ...

Rust 1.2.0

• ~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.

Rust 1.1.0

• ~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.

Rust 1.0.0

• ~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.

Rust 1.0.0-alpha.2

• ~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<U> now automatically coerce to references to the dereferenced type U, e.g. &T where T: Deref<U> automatically coerces to &U. This should eliminate many unsightly uses of &*, as when converting from references to vectors into references to slices. RFC.
  • 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.