Rust 1.22.1

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

Rust 1.22.0

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

Rust 1.21.0

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

Rust 1.20.0

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.

Rust 1.19.0

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

Rust 1.18.0

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)

Rust 1.17.0

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<U>. 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<U>, e.g. coercing &mut [&'a X; N] to &mut [&'b X] requires 'a be equal to 'b. Soundness fix.
• format! and Display::to_string panic if an underlying formatting implementation returns an error. Previously the error was silently ignored. It is incorrect for write_fmt to return an error when writing to a string.
• 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 i...

Rust 1.16.0

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.

Rust 1.15.1

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

Rust 1.15.0

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 [`lega...