Version 1.32.0 (2019-01-17)

Language

2018 edition

You can now use the ? operator in macro definitions. The ? operator allows you to specify zero or one repetitions similar to the * and + operators.

Module paths with no leading keyword like super, self, or crate, will now always resolve to the item (enum, struct, etc.) available in the module if present, before resolving to a external crate or an item the prelude. E.g.

#![allow(unused)]
fn main() {
enum Color { Red, Green, Blue }

use Color::*;
}

All editions

You can now match against PhantomData<T> types.
You can now match against literals in macros with the literal specifier. This will match against a literal of any type. E.g. 1, 'A', "Hello World"

Self can now be used as a constructor and pattern for unit and tuple structs. E.g.

#![allow(unused)]
fn main() {
struct Point(i32, i32);

impl Point {
    pub fn new(x: i32, y: i32) -> Self {
        Self(x, y)
    }

    pub fn is_origin(&self) -> bool {
        match self {
            Self(0, 0) => true,
            _ => false,
        }
    }
}
}

Self can also now be used in type definitions. E.g.

#![allow(unused)]
fn main() {
enum List<T>
where
    Self: PartialOrd<Self> // can write `Self` instead of `List<T>`
{
    Nil,
    Cons(T, Box<Self>) // likewise here
}
}

You can now mark traits with #[must_use]. This provides a warning if a impl Trait or dyn Trait is returned and unused in the program.

Compiler

The default allocator has changed from jemalloc to the default allocator on your system. The compiler itself on Linux & macOS will still use jemalloc, but programs compiled with it will use the system allocator.
Added the aarch64-pc-windows-msvc target.

Libraries

PathBuf now implements FromStr.
Box<[T]> now implements FromIterator<T>.

The dbg! macro has been stabilized. This macro enables you to easily debug expressions in your rust program. E.g.

#![allow(unused)]
fn main() {
let a = 2;
let b = dbg!(a * 2) + 1;
//      ^-- prints: [src/main.rs:4] a * 2 = 4
assert_eq!(b, 5);
}

The following APIs are now const functions and can be used in a const context.

Stabilized APIs

Cargo

Misc

libproc_macro has been added to the rust-src distribution.

Compatibility Notes

The argument types for AVX's _mm256_stream_si256, _mm256_stream_pd, _mm256_stream_ps have been changed from *const to *mut as the previous implementation was unsound.