Rust 1.32.0

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.

• Cell::as_ptr
• UnsafeCell::get
• char::is_ascii
• iter::empty
• ManuallyDrop::new
• ManuallyDrop::into_inner
• RangeInclusive::start
• RangeInclusive::end
• NonNull::as_ptr
• slice::as_ptr
• str::as_ptr
• Duration::as_secs
• Duration::subsec_millis
• Duration::subsec_micros
• Duration::subsec_nanos
• CStr::as_ptr
• Ipv4Addr::is_unspecified
• Ipv6Addr::new
• Ipv6Addr::octets

Stabilized APIs

• i8::to_be_bytes
• i8::to_le_bytes
• i8::to_ne_bytes
• i8::from_be_bytes
• i8::from_le_bytes
• i8::from_ne_bytes
• i16::to_be_bytes
• i16::to_le_bytes
• i16::to_ne_bytes
• i16::from_be_bytes
• i16::from_le_bytes
• i16::from_ne_bytes
• i32::to_be_bytes
• i32::to_le_bytes
• i32::to_ne_bytes
• i32::from_be_bytes
• i32::from_le_bytes
• i32::from_ne_bytes
• i64::to_be_bytes
• i64::to_le_bytes
• i64::to_ne_bytes
• i64::from_be_bytes
• i64::from_le_bytes
• i64::from_ne_bytes
• i128::to_be_bytes
• i128::to_le_bytes
• i128::to_ne_bytes
• i128::from_be_bytes
• i128::from_le_bytes
• i128::from_ne_bytes
• isize::to_be_bytes
• isize::to_le_bytes
• isize::to_ne_bytes
• isize::from_be_bytes
• isize::from_le_bytes
• isize::from_ne_bytes
• u8::to_be_bytes
• u8::to_le_bytes
• u8::to_ne_bytes
• u8::from_be_bytes
• u8::from_le_bytes
• u8::from_ne_bytes
• u16::to_be_bytes
• u16::to_le_bytes
• u16::to_ne_bytes
• u16::from_be_bytes
• u16::from_le_bytes
• u16::from_ne_bytes
• u32::to_be_bytes
• u32::to_le_bytes
• u32::to_ne_bytes
• u32::from_be_bytes
• u32::from_le_bytes
• u32::from_ne_bytes
• u64::to_be_bytes
• u64::to_le_bytes
• u64::to_ne_bytes
• u64::from_be_bytes
• u64::from_le_bytes
• u64::from_ne_bytes
• u128::to_be_bytes
• u128::to_le_bytes
• u128::to_ne_bytes
• u128::from_be_bytes
• u128::from_le_bytes
• u128::from_ne_bytes
• usize::to_be_bytes
• usize::to_le_bytes
• usize::to_ne_bytes
• usize::from_be_bytes
• usize::from_le_bytes
• usize::from_ne_bytes

Cargo

• You can now run cargo c as an alias for cargo check.
• Usernames are now allowed in alt registry URLs.

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.