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Rust 1.41.0

Released on January 30, 2020

What's Changed

  • [You can now pass type parameters to foreign items when implementing
  • [You can now arbitrarily nest receiver types in the self position.][64325] E.g. you can
  • [You can now use any valid identifier in a format_args macro.][66847]
  • [Visibility modifiers (e.g. pub) are now syntactically allowed on trait items and
  • [You can now define a Rust extern "C" function with Box and use T* as the corresponding

  • [Rustc will now warn if you have unused loop 'labels.][66325]
  • [Removed support for the i686-unknown-dragonfly target.][67255]
  • [Added tier 3 support\* for the riscv64gc-unknown-linux-gnu target.][66661]
  • [You can now pass an arguments file passing the @path syntax
  • [You can now provide --extern flag without a path, indicating that it is

  • [The core::panic module is now stable.][66771] It was already stable
  • [NonZero numerics now implement From> if it's a smaller integer
  • [MaybeUninit now implements fmt::Debug.][65013]
  • [Result::map_or]
  • [Result::map_or_else]
  • [std::rc::Weak::weak_count]
  • [std::rc::Weak::strong_count]
  • [std::sync::Weak::weak_count]
  • [std::sync::Weak::strong_count]

  • [Cargo will now document all the private items for binary crates
  • [cargo-install will now reinstall the package if it detects that it is out
  • [Cargo.lock now uses a more git friendly format that should help to reduce
  • [You can now override specific dependencies's build settings][cargo/7591] E.g.

  • [As previously announced 1.41 will be the last tier 1 release for 32-bit

  • [You can now specify edition in documentation code blocks to compile the block
  • [You can now provide custom themes to rustdoc with --theme, and check the
  • [You can use #[cfg(doc)] to compile an item when building documentation.][61351]
Full Changelog

Language

--------

- [You can now pass type parameters to foreign items when implementing

traits.][65879] E.g. You can now write impl From for Vec {}.

- [You can now arbitrarily nest receiver types in the self position.][64325] E.g. you can

now write fn foo(self: Box>) {}. Previously only Self, &Self,

&mut Self, Arc, Rc, and Box were allowed.

- [You can now use any valid identifier in a format_args macro.][66847]

Previously identifiers starting with an underscore were not allowed.

- [Visibility modifiers (e.g. pub) are now syntactically allowed on trait items and

enum variants.][66183] These are still rejected semantically, but

can be seen and parsed by procedural macros and conditional compilation.

- [You can now define a Rust extern "C" function with Box and use T* as the corresponding

type on the C side.][62514] Please see [the documentation][box-memory-layout] for more information,

including the important caveat about preferring to avoid Box in Rust signatures for functions defined in C.

[box-memory-layout]: https://doc.rust-lang.org/std/boxed/index.html#memory-layout

Compiler

--------

- [Rustc will now warn if you have unused loop 'labels.][66325]

- [Removed support for the i686-unknown-dragonfly target.][67255]

- [Added tier 3 support\* for the riscv64gc-unknown-linux-gnu target.][66661]

- [You can now pass an arguments file passing the @path syntax

to rustc.][66172] Note that the format differs somewhat from what is

found in other tooling; please see [the documentation][argfile-docs] for

more information.

- [You can now provide --extern flag without a path, indicating that it is

available from the search path or specified with an -L flag.][64882]

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

information on Rust's tiered platform support.

[argfile-docs]: https://doc.rust-lang.org/nightly/rustc/command-line-arguments.html#path-load-command-line-flags-from-a-path

Libraries

---------

- [The core::panic module is now stable.][66771] It was already stable

through std.

- [NonZero numerics now implement From> if it's a smaller integer

width.][66277] E.g. NonZeroU16 now implements From.

- [MaybeUninit now implements fmt::Debug.][65013]

Stabilized APIs

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

- [Result::map_or]

- [Result::map_or_else]

- [std::rc::Weak::weak_count]

- [std::rc::Weak::strong_count]

- [std::sync::Weak::weak_count]

- [std::sync::Weak::strong_count]

Cargo

-----

- [Cargo will now document all the private items for binary crates

by default.][cargo/7593]

- [cargo-install will now reinstall the package if it detects that it is out

of date.][cargo/7560]

- [Cargo.lock now uses a more git friendly format that should help to reduce

merge conflicts.][cargo/7579]

- [You can now override specific dependencies's build settings][cargo/7591] E.g.

[profile.dev.package.image] opt-level = 2 sets the image crate's

optimisation level to 2 for debug builds. You can also use

[profile..build-override] to override build scripts and

their dependencies.

Misc

----

- [You can now specify edition in documentation code blocks to compile the block

for that edition.][66238] E.g. edition2018 tells rustdoc that the code sample

should be compiled the 2018 edition of Rust.

- [You can now provide custom themes to rustdoc with --theme, and check the

current theme with --check-theme.][54733]

- [You can use #[cfg(doc)] to compile an item when building documentation.][61351]

Compatibility Notes

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

- [As previously announced 1.41 will be the last tier 1 release for 32-bit

Apple targets.][apple-32bit-drop] This means that the source code is still

available to build, but the targets are no longer being tested and release

binaries for those platforms will no longer be distributed by the Rust project.

Please refer to the linked blog post for more information.

[54733]: https://github.com/rust-lang/rust/pull/54733/

[61351]: https://github.com/rust-lang/rust/pull/61351/

[62514]: https://github.com/rust-lang/rust/pull/62514/

[67255]: https://github.com/rust-lang/rust/pull/67255/

[66661]: https://github.com/rust-lang/rust/pull/66661/

[66771]: https://github.com/rust-lang/rust/pull/66771/

[66847]: https://github.com/rust-lang/rust/pull/66847/

[66238]: https://github.com/rust-lang/rust/pull/66238/

[66277]: https://github.com/rust-lang/rust/pull/66277/

[66325]: https://github.com/rust-lang/rust/pull/66325/

[66172]: https://github.com/rust-lang/rust/pull/66172/

[66183]: https://github.com/rust-lang/rust/pull/66183/

[65879]: https://github.com/rust-lang/rust/pull/65879/

[65013]: https://github.com/rust-lang/rust/pull/65013/

[64882]: https://github.com/rust-lang/rust/pull/64882/

[64325]: https://github.com/rust-lang/rust/pull/64325/

[cargo/7560]: https://github.com/rust-lang/cargo/pull/7560/

[cargo/7579]: https://github.com/rust-lang/cargo/pull/7579/

[cargo/7591]: https://github.com/rust-lang/cargo/pull/7591/

[cargo/7593]: https://github.com/rust-lang/cargo/pull/7593/

[Result::map_or_else]: https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or_else

[Result::map_or]: https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or

[std::rc::Weak::weak_count]: https://doc.rust-lang.org/std/rc/struct.Weak.html#method.weak_count

[std::rc::Weak::strong_count]: https://doc.rust-lang.org/std/rc/struct.Weak.html#method.strong_count

[std::sync::Weak::weak_count]: https://doc.rust-lang.org/std/sync/struct.Weak.html#method.weak_count

[std::sync::Weak::strong_count]: https://doc.rust-lang.org/std/sync/struct.Weak.html#method.strong_count

[apple-32bit-drop]: https://blog.rust-lang.org/2020/01/03/reducing-support-for-32-bit-apple-targets.html