Rust 1.29.1

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.

Rust 1.29.0

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.

Rust 1.28.0

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"); }
  }

Rust 1.27.2

Compatibility Notes

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

Rust 1.27.1

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.

Rust 1.27.0

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.

Rust 1.26.2

Compatibility Notes

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

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].