Rust release · Apr 27, 2017

Rust 1.17: what's new, what was stabilized

Short answerRust 1.17 was released on Apr 27, 2017: 19 newly stable APIs (Arc::into_raw, Arc::from_raw, Arc::ptr_eq, Rc::into_raw, ...); 12 compatibility notes that can affect existing code.

Apr 27, 2017release date

0language stabilizations

19APIs stabilized

-new edition

← Rust 1.16 All versions Rust 1.18 →

19 APIs stabilized

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

Can it break my build?

The release lists these compatibility notes. Most only affect rare code, but read them before you raise your toolchain in CI:

[Rust 1.17 does not correctly detect the MSVC 2017 linker][38584]. As a
[When coercing to an unsized type lifetimes must be equal][40319]. That is,
[format! and Display::to_string panic if an underlying formatting
[In-tree crates are verified to be unstable][39851]. Previously, some minor
[Rust git source no longer includes vendored crates][39728]. Those that need
[Fix inert attributes from proc_macro_derives][39572]
[During crate resolution, rustc prefers a crate in the sysroot if two crates
[Fixed bugs around how type inference interacts with dead-code][39485]. The
[Tuple-struct constructors with private fields are no longer visible][38932]
[Lifetime parameters that do not appear in the arguments are now considered
[rustdoc: fix doctests with non-feature crate attributes][38161]
[Make transmuting from fn item types to pointer-sized types a hard

Use it

rustup update stable        # get the newest release
rustup install 1.17          # or exactly this one
rustup override set 1.17     # pin a project to it

To require at least this version from users of your crate, set rust-version = "1.17" under [package] in Cargo.toml. Cargo then refuses to build it on older compilers with a clear message, and with resolver 3 (the default on the 2024 edition, Rust 1.85+) it also prefers dependency versions that support it.

Full release notes

Language

[The lifetime of statics and consts defaults to 'static][39265]. [RFC 1623]
[Fields of structs may be initialized without duplicating the field/variable names][39761]. [RFC 1682]
[Self may be included in the where clause of impls][38864]. [RFC 1647]
[When coercing to an unsized type lifetimes must be equal][40319]. 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][40166]
[Static variables may contain references to other statics][40027]

Compiler

[Exit quickly on only --emit dep-info][40336]
[Make -C relocation-model more correctly determine whether the linker creates a position-independent executable][40245]
[Add -C overflow-checks to directly control whether integer overflow panics][40037]
[The rustc type checker now checks items on demand instead of in a single in-order pass][40008]. 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][39995]
[Turn off vectorization for Emscripten targets][39990]
[Provide suggestions for unknown macros imported with use][39953]
[Fix ICEs in path resolution][39939]
[Strip exception handling code on Emscripten when panic=abort][39193]
[Add clearer error message using &str + &str][39116]

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][27787]
[Cell can store non-Copy types][39793]. [RFC 1651]
[String implements FromIterator<&char>][40028]
Box [implements][40009] 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][39960]
[Specialize PartialOrd<A> for [A] where A: Ord][39642]
[Slightly optimize slice::sort][39538]
[Add ToString trait specialization for Cow<'a, str> and String][39440]
[Box<[T]> implements From<&[T]> where T: Copy, Box<str> implements From<&str>][39438]
[IpAddr implements From for various arrays. SocketAddr implements From<(I, u16)> where I: Into<IpAddr>][39372]
[format! estimates the needed capacity before writing a string][39356]
[Support unprivileged symlink creation in Windows][38921]
[PathBuf implements Default][38764]
[Implement PartialEq<[A]> for VecDeque<A>][38661]
[HashMap resizes adaptively][38368] to guard against DOS attacks and poor hash functions.

Cargo

[Add cargo check --all][cargo/3731]
[Add an option to ignore SSL revocation checking][cargo/3699]
[Add cargo run --package][cargo/3691]
[Add required_features][cargo/3667]
[Assume build.rs is a build script][cargo/3664]
[Find workspace via workspace_root link in containing member][cargo/3562]

Misc

[Documentation is rendered with mdbook instead of the obsolete, in-tree rustbook][39633]
[The "Unstable Book" documents nightly-only features][ubook]
[Improve the style of the sidebar in rustdoc output][40265]
[Configure build correctly on 64-bit CPU's with the armhf ABI][40261]
[Fix MSP430 breakage due to i128][40257]
[Preliminary Solaris/SPARCv9 support][39903]
[rustc is linked statically on Windows MSVC targets][39837], allowing it to run without installing the MSVC runtime.
[rustdoc --test includes file names in test names][39788]
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][39491]
[Initial support for i686-unknown-netbsd][39426]
[This release no longer includes the old makefile build system][39431]. Rust is built with a custom build system, written in Rust, and with Cargo.
[Add Debug implementations for libcollection structs][39002]
[TypeId implements PartialOrd and Ord][38981]
[--test-threads=0 produces an error][38945]
[rustup installs documentation by default][40526]
[The Rust source includes NatVis visualizations][39843]. 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 inert attributes from proc_macro_derives
During crate resolution, rustc prefers a crate in the sysroot if two crates are otherwise identical. Unlikely to be encountered outside the Rust build system.
Fixed bugs around how type inference interacts with dead-code. The existing code generally ignores the type of dead-code unless a type-hint is provided; this can cause surprising inference interactions particularly around defaulting. The new code uniformly ignores the result type of dead-code.
Tuple-struct constructors with private fields are no longer visible
Lifetime parameters that do not appear in the arguments are now considered early-bound, resolving a soundness bug (#32330). The hr_lifetime_in_assoc_type future-compatibility lint has been in effect since April of 2016.
rustdoc: fix doctests with non-feature crate attributes
Make transmuting from fn item types to pointer-sized types a hard error

Release notes from the Rust project's RELEASES.md (MIT or Apache-2.0); summaries above are ours.