Updatify / Rust | Release notes

Language

• You can now use tuple structs and tuple enum variant’s constructors in const contexts. e.g.

  pub struct Point(i32, i32);
  
  const ORIGIN: Point = {
      let constructor = Point;
  
      constructor(0, 0)
  };

• You can now mark structs, enums, and enum variants with the #[non_exhaustive] attribute to indicate that there may be variants or fields added in the future. For example this requires adding a wild-card branch (_ => {}) to any match statements on a non-exhaustive enum. (RFC 2008)

• You can now use function-like procedural macros in extern blocks and in type positions. e.g. type Generated = macro!();

• Function-like and attribute procedural macros can now emit macro_rules! items, so you can now have your macros generate macros.

• The meta pattern matcher in macro_rules! now correctly matches the modern attribute syntax. For example (#[$m:meta]) now matches #[attr], #[attr{tokens}], #[attr[tokens]], and #[attr(tokens)].

Compiler

• Added tier 3 support* for the thumbv7neon-unknown-linux-musleabihf target.

• Fix bindings in tuple struct patterns
• Fix track_caller integration with trait objects

Compiler

• Bumped minimum LLVM version to 5.0.
• Added powerpc64le-unknown-linux-musl target.
• Added aarch64-unknown-hermit and x86_64-unknown-hermit targets.
• Upgraded to LLVM 7.

Libraries

• Once::call_once no longer requires Once to be 'static.
• BuildHasherDefault now implements PartialEq and Eq.
• Box<CStr>, Box<OsStr>, and Box<Path> now implement Clone.
• Implemented PartialEq<&str> for OsString and PartialEq<OsString> for &str.
• Cell<T> now allows T to be unsized.
• SocketAddr is now stable on Redox.

Stabilized APIs

• Arc::downcast
• Iterator::flatten
• Rc::downcast

Cargo

• Cargo can silently fix some bad lockfiles. You can use --locked to disable this behavior.

• rustfmt accepts rustfmt_skip in cfg_attr again.
• Don’t hash executable filenames on apple platforms, fixing backtraces.
• Fix crashes when finding backtrace on macOS.
• Clippy applies lint levels into different files.

Language

• if, match, and loop expressions can now be used in const functions.
• Additionally you are now also able to coerce and cast to slices (&[T]) in const functions.
• The #[track_caller] attribute can now be added to functions to use the function’s caller’s location information for panic messages.
• Recursively indexing into tuples no longer needs parentheses. E.g. x.0.0 over (x.0).0.
• mem::transmute can now be used in statics and constants. Note You currently can’t use mem::transmute in constant functions.

Compiler

• You can now use the cdylib target on Apple iOS and tvOS platforms.
• Enabled static “Position Independent Executables” by default for x86_64-unknown-linux-musl.

Libraries

• mem::forget is now a const fn.
• String now implements From<char>.
• The leading_ones, and trailing_ones methods have been stabilised for all integer types.