Rust 1.21.0

Language

--------

- [You can now use static references for literals.][43838]

Example:

  fn main() {
let x: &'static u32 = &0;
}

- [Relaxed path syntax. Optional :: before < is now allowed in all contexts.][43540]

Example:

  my_macro!(Vec::new); // Always worked
my_macro!(Vec::::new); // Now works

Compiler

--------

- [Upgraded jemalloc to 4.5.0][43911]

- [Enabled unwinding panics on Redox][43917]

- [Now runs LLVM in parallel during translation phase.][43506]

This should reduce peak memory usage.

Libraries

---------

- [Generate builtin impls for Clone for all arrays and tuples that

are T: Clone][43690]

- [Stdin, Stdout, and Stderr now implement AsRawFd.][43459]

- [Rc and Arc now implement From<&[T]> where T: Clone, From,

From, From> where T: ?Sized, and From>.][42565]

Stabilized APIs

---------------

[std::mem::discriminant]

Cargo

-----

- [You can now call cargo install with multiple package names][cargo/4216]

- [Cargo commands inside a virtual workspace will now implicitly

pass --all][cargo/4335]

- [Added a [patch] section to Cargo.toml to handle

prepublication dependencies][cargo/4123] [RFC 1969]

- [include & exclude fields in Cargo.toml now accept gitignore

like patterns][cargo/4270]

- [Added the --all-targets option][cargo/4400]

- [Using required dependencies as a feature is now deprecated and emits

a warning][cargo/4364]

Misc

----

- [Cargo docs are moving][43916]

to doc.rust-lang.org/cargo

- [The rustdoc book is now available][43863]

at doc.rust-lang.org/rustdoc

- [Added a preview of RLS has been made available through rustup][44204]

Install with rustup component add rls-preview

- [std::os documentation for Unix, Linux, and Windows now appears on doc.rust-lang.org][43348]

Previously only showed std::os::unix.

Compatibility Notes

-------------------

- [Changes in method matching against higher-ranked types][43880] This may cause

breakage in subtyping corner cases. [A more in-depth explanation is available.][info/43880]

- [rustc's JSON error output's byte position start at top of file.][42973]

Was previously relative to the rustc's internal CodeMap struct which

required the unstable library libsyntax to correctly use.

- [unused_results lint no longer ignores booleans][43728]

[42565]: https://github.com/rust-lang/rust/pull/42565

[42973]: https://github.com/rust-lang/rust/pull/42973

[43348]: https://github.com/rust-lang/rust/pull/43348

[43459]: https://github.com/rust-lang/rust/pull/43459

[43506]: https://github.com/rust-lang/rust/pull/43506

[43540]: https://github.com/rust-lang/rust/pull/43540

[43690]: https://github.com/rust-lang/rust/pull/43690

[43728]: https://github.com/rust-lang/rust/pull/43728

[43838]: https://github.com/rust-lang/rust/pull/43838

[43863]: https://github.com/rust-lang/rust/pull/43863

[43880]: https://github.com/rust-lang/rust/pull/43880

[43911]: https://github.com/rust-lang/rust/pull/43911

[43916]: https://github.com/rust-lang/rust/pull/43916

[43917]: https://github.com/rust-lang/rust/pull/43917

[44204]: https://github.com/rust-lang/rust/pull/44204

[cargo/4123]: https://github.com/rust-lang/cargo/pull/4123

[cargo/4216]: https://github.com/rust-lang/cargo/pull/4216

[cargo/4270]: https://github.com/rust-lang/cargo/pull/4270

[cargo/4335]: https://github.com/rust-lang/cargo/pull/4335

[cargo/4364]: https://github.com/rust-lang/cargo/pull/4364

[cargo/4400]: https://github.com/rust-lang/cargo/pull/4400

[RFC 1969]: https://github.com/rust-lang/rfcs/pull/1969

[info/43880]: https://github.com/rust-lang/rust/issues/44224#issuecomment-330058902

[std::mem::discriminant]: https://doc.rust-lang.org/std/mem/fn.discriminant.html