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 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