1.32.0

1.32.0 (17 January, 2019) #

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.
```
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.

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.

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.

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.