Rust 0.12.0

* ~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 . 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 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.