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Rust 1.39.0

Released on November 7, 2019

What's Changed

  • [You can now create async functions and blocks with async fn, async move {}, and
  • [You can now use certain attributes on function, closure, and function pointer
  • [You can now take shared references to bind-by-move patterns in the if guards

  • [Added tier 3\* support for the i686-unknown-uefi target.][64334]
  • [Added tier 3 support for the sparc64-unknown-openbsd target.][63595]
  • [rustc will now trim code snippets in diagnostics to fit in your terminal.][63402]
  • [You can now pass --show-output argument to test binaries to print the

  • [Vec::new and String::new are now const functions.][64028]
  • [LinkedList::new is now a const function.][63684]
  • [str::len, [T]::len and str::as_bytes are now const functions.][63770]
  • [The abs, wrapping_abs, and overflowing_abs numeric functions are
  • [Pin::into_inner]
  • [Instant::checked_duration_since]
  • [Instant::saturating_duration_since]

  • [You can now publish git dependencies if supplied with a version.][cargo/7237]
  • [The --all flag has been renamed to --workspace.][cargo/7241] Using

  • [Code that was previously accepted by the old borrow checker, but rejected by
  • [rustdoc now requires rustc to be installed and in the same directory to
  • [The try! macro will now issue a deprecation warning.][62672] It is
  • [asinh(-0.0) now correctly returns -0.0.][63698] Previously this

  • [You can now pass -Clinker to rustdoc to control the linker used
Full Changelog

Language

--------

- [You can now create async functions and blocks with async fn, async move {}, and

async {} respectively, and you can now call .await on async expressions.][63209]

- [You can now use certain attributes on function, closure, and function pointer

parameters.][64010] These attributes include cfg, cfg_attr, allow, warn,

deny, forbid as well as inert helper attributes used by procedural macro

attributes applied to items. e.g.

  fn len(

#[cfg(windows)] slice: &[u16],


#[cfg(not(windows))] slice: &[u8],


) -> usize {


slice.len()


}

- [You can now take shared references to bind-by-move patterns in the if guards

of match arms.][63118] e.g.

  fn main() {

let array: Box<[u8; 4]> = Box::new([1, 2, 3, 4]);


match array {


nums


//      ---- nums is bound by move.


if nums.iter().sum::() == 10


//                 ^------ .iter() implicitly takes a reference to nums.


=> {


drop(nums);


//          ----------- Legal as nums was bound by move and so we have ownership.


}


_ => unreachable!(),


}


}

Compiler

--------

- [Added tier 3\* support for the i686-unknown-uefi target.][64334]

- [Added tier 3 support for the sparc64-unknown-openbsd target.][63595]

- [rustc will now trim code snippets in diagnostics to fit in your terminal.][63402]

Note Cargo currently doesn't use this feature. Refer to

[cargo#7315][cargo/7315] to track this feature's progress.

- [You can now pass --show-output argument to test binaries to print the

output of successful tests.][62600]

\* Refer to Rust's [platform support page][platform-support-doc] for more

information on Rust's tiered platform support.

Libraries

---------

- [Vec::new and String::new are now const functions.][64028]

- [LinkedList::new is now a const function.][63684]

- [str::len, [T]::len and str::as_bytes are now const functions.][63770]

- [The abs, wrapping_abs, and overflowing_abs numeric functions are

now const.][63786]

Stabilized APIs

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

- [Pin::into_inner]

- [Instant::checked_duration_since]

- [Instant::saturating_duration_since]

Cargo

-----

- [You can now publish git dependencies if supplied with a version.][cargo/7237]

- [The --all flag has been renamed to --workspace.][cargo/7241] Using

--all is now deprecated.

Misc

----

- [You can now pass -Clinker to rustdoc to control the linker used

for compiling doctests.][63834]

Compatibility Notes

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

- [Code that was previously accepted by the old borrow checker, but rejected by

the NLL borrow checker is now a hard error in Rust 2018.][63565] This was

previously a warning, and will also become a hard error in the Rust 2015

edition in the 1.40.0 release.

- [rustdoc now requires rustc to be installed and in the same directory to

run tests.][63827] This should improve performance when running a large

amount of doctests.

- [The try! macro will now issue a deprecation warning.][62672] It is

recommended to use the ? operator instead.

- [asinh(-0.0) now correctly returns -0.0.][63698] Previously this

returned 0.0.

[62600]: https://github.com/rust-lang/rust/pull/62600/

[62672]: https://github.com/rust-lang/rust/pull/62672/

[63118]: https://github.com/rust-lang/rust/pull/63118/

[63209]: https://github.com/rust-lang/rust/pull/63209/

[63402]: https://github.com/rust-lang/rust/pull/63402/

[63565]: https://github.com/rust-lang/rust/pull/63565/

[63595]: https://github.com/rust-lang/rust/pull/63595/

[63684]: https://github.com/rust-lang/rust/pull/63684/

[63698]: https://github.com/rust-lang/rust/pull/63698/

[63770]: https://github.com/rust-lang/rust/pull/63770/

[63786]: https://github.com/rust-lang/rust/pull/63786/

[63827]: https://github.com/rust-lang/rust/pull/63827/

[63834]: https://github.com/rust-lang/rust/pull/63834/

[64010]: https://github.com/rust-lang/rust/pull/64010/

[64028]: https://github.com/rust-lang/rust/pull/64028/

[64334]: https://github.com/rust-lang/rust/pull/64334/

[cargo/7237]: https://github.com/rust-lang/cargo/pull/7237/

[cargo/7241]: https://github.com/rust-lang/cargo/pull/7241/

[cargo/7315]: https://github.com/rust-lang/cargo/pull/7315/

[Pin::into_inner]: https://doc.rust-lang.org/std/pin/struct.Pin.html#method.into_inner

[Instant::checked_duration_since]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.checked_duration_since

[Instant::saturating_duration_since]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.saturating_duration_since