Rust 1.26.1

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.

Rust 1.26.0

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.

Rust 1.25.0

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].

Rust 1.24.1

• 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.

Rust 1.24.0

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

Rust 1.23.0

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

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.