Version 0.12.0 (2014-10-09)

• ~1900 changes, numerous bugfixes

• Highlights

  • The introductory documentation (now called The Rust Guide) has been completely rewritten, as have a number of supplementary guides.
  • Rust's package manager, Cargo, continues to improve and is sometimes considered to be quite awesome.
  • Many API's in std have been reviewed and updated for consistency with the in-development Rust coding guidelines. The standard library documentation tracks stabilization progress.
  • Minor libraries have been moved out-of-tree to the rust-lang org on GitHub: uuid, semver, glob, num, hexfloat, fourcc. They can be installed with Cargo.
  • Lifetime elision allows lifetime annotations to be left off of function declarations in many common scenarios.
  • Rust now works on 64-bit Windows.

• Language

  • Indexing can be overloaded with the Index and IndexMut traits.
  • The if let construct takes a branch only if the let pattern matches, currently behind the 'if_let' feature gate.
  • 'where clauses', a more flexible syntax for specifying trait bounds that is more aesthetic, have been added for traits and free functions. Where clauses will in the future make it possible to constrain associated types, which would be impossible with the existing syntax.
  • A new slicing syntax (e.g. [0..4]) has been introduced behind the 'slicing_syntax' feature gate, and can be overloaded with the Slice or SliceMut traits.
  • The syntax for matching of sub-slices has been changed to use a postfix .. instead of prefix (.e.g. [a, b, c..]), for consistency with other uses of .. and to future-proof potential additional uses of the syntax.
  • The syntax for matching inclusive ranges in patterns has changed from 0..3 to 0...4 to be consistent with the exclusive range syntax for slicing.
  • Matching of sub-slices in non-tail positions (e.g. [a.., b, c]) has been put behind the 'advanced_slice_patterns' feature gate and may be removed in the future.
  • Components of tuples and tuple structs can be extracted using the value.0 syntax, currently behind the tuple_indexing feature gate.
  • The #[crate_id] attribute is no longer supported; versioning is handled by the package manager.
  • Renaming crate imports are now written extern crate foo as bar instead of extern crate bar = foo.
  • Renaming use statements are now written use foo as bar instead of use bar = foo.
  • let and match bindings and argument names in macros are now hygienic.
  • The new, more efficient, closure types ('unboxed closures') have been added under a feature gate, 'unboxed_closures'. These will soon replace the existing closure types, once higher-ranked trait lifetimes are added to the language.
  • move has been added as a keyword, for indicating closures that capture by value.
  • Mutation and assignment is no longer allowed in pattern guards.
  • Generic structs and enums can now have trait bounds.
  • The Share trait is now called Sync to free up the term 'shared' to refer to 'shared reference' (the default reference type.
  • Dynamically-sized types have been mostly implemented, unifying the behavior of fat-pointer types with the rest of the type system.
  • As part of dynamically-sized types, the Sized trait has been introduced, which qualifying types implement by default, and which type parameters expect by default. To specify that a type parameter does not need to be sized, write <Sized? T>. Most types are Sized, notable exceptions being unsized arrays ([T]) and trait types.
  • Closures can return !, as in || -> ! or proc() -> !.
  • Lifetime bounds can now be applied to type parameters and object types.
  • The old, reference counted GC type, Gc<T> which was once denoted by the @ sigil, has finally been removed. GC will be revisited in the future.

• Libraries

  • Library documentation has been improved for a number of modules.
  • Bit-vectors, collections::bitv has been modernized.
  • The url crate is deprecated in favor of http://github.com/servo/rust-url, which can be installed with Cargo.
  • Most I/O stream types can be cloned and subsequently closed from a different thread.
  • A std::time::Duration type has been added for use in I/O methods that rely on timers, as well as in the 'time' crate's Timespec arithmetic.
  • The runtime I/O abstraction layer that enabled the green thread scheduler to do non-thread-blocking I/O has been removed, along with the libuv-based implementation employed by the green thread scheduler. This will greatly simplify the future I/O work.
  • collections::btree has been rewritten to have a more idiomatic and efficient design.

• Tooling

  • rustdoc output now indicates the stability levels of API's.
  • The --crate-name flag can specify the name of the crate being compiled, like #[crate_name].
  • The -C metadata specifies additional metadata to hash into symbol names, and -C extra-filename specifies additional information to put into the output filename, for use by the package manager for versioning.
  • debug info generation has continued to improve and should be more reliable under both gdb and lldb.
  • rustc has experimental support for compiling in parallel using the -C codegen-units flag.
  • rustc no longer encodes rpath information into binaries by default.

• Misc

  • Stack usage has been optimized with LLVM lifetime annotations.
  • Official Rust binaries on Linux are more compatible with older kernels and distributions, built on CentOS 5.10.