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