Rust 1.44.0

Language

--------

- [You can now use async/.await with #[no_std] enabled.][69033]

- [Added the unused_braces lint.][70081]

Syntax-only changes

- [Expansion-driven outline module parsing][69838]

#[cfg(FALSE)]
mod foo {
mod bar {
mod baz; // foo/bar/baz.rs doesn't exist, but no error!
}
}

These are still rejected semantically, so you will likely receive an error but

these changes can be seen and parsed by macros and conditional compilation.

Compiler

--------

- [Rustc now respects the -C codegen-units flag in incremental mode.][70156]

Additionally when in incremental mode rustc defaults to 256 codegen units.

- [Refactored catch_unwind to have zero-cost, unless unwinding is enabled and

a panic is thrown.][67502]

- [Added tier 3\* support for the aarch64-unknown-none and

aarch64-unknown-none-softfloat targets.][68334]

- [Added tier 3 support for arm64-apple-tvos and

x86_64-apple-tvos targets.][68191]

Libraries

---------

- [Special cased vec![] to map directly to Vec::new().][70632] This allows

vec![] to be able to be used in const contexts.

- [convert::Infallible now implements Hash.][70281]

- [OsString now implements DerefMut and IndexMut returning

a &mut OsStr.][70048]

- [Unicode 13 is now supported.][69929]

- [String now implements From<&mut str>.][69661]

- [IoSlice now implements Copy.][69403]

- [Vec now implements From<[T; N]>.][68692] Where N is at most 32.

- [proc_macro::LexError now implements fmt::Display and Error.][68899]

- [from_le_bytes, to_le_bytes, from_be_bytes, to_be_bytes,

from_ne_bytes, and to_ne_bytes methods are now const for all

integer types.][69373]

Stabilized APIs

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

- [PathBuf::with_capacity]

- [PathBuf::capacity]

- [PathBuf::clear]

- [PathBuf::reserve]

- [PathBuf::reserve_exact]

- [PathBuf::shrink_to_fit]

- [f32::to_int_unchecked]

- [f64::to_int_unchecked]

- [Layout::align_to]

- [Layout::pad_to_align]

- [Layout::array]

- [Layout::extend]

Cargo

-----

- [Added the cargo tree command which will print a tree graph of

your dependencies.][cargo/8062] E.g.

    mdbook v0.3.2 (/Users/src/rust/mdbook)
├── ammonia v3.0.0
│   ├── html5ever v0.24.0
│   │   ├── log v0.4.8
│   │   │   └── cfg-if v0.1.9
│   │   ├── mac v0.1.1
│   │   └── markup5ever v0.9.0
│   │       ├── log v0.4.8 (*)
│   │       ├── phf v0.7.24
│   │       │   └── phf_shared v0.7.24
│   │       │       ├── siphasher v0.2.3
│   │       │       └── unicase v1.4.2
│   │       │           [build-dependencies]
│   │       │           └── version_check v0.1.5
...

You can also display dependencies on multiple versions of the same crate with

cargo tree -d (short for cargo tree --duplicates).

Misc

----

- [Rustdoc now allows you to specify --crate-version to have rustdoc include

the version in the sidebar.][69494]

Compatibility Notes

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

- [Rustc now correctly generates static libraries on Windows GNU targets with

the .a extension, rather than the previous .lib.][70937]

- [Removed the -C no_integrated_as flag from rustc.][70345]

- [The file_name property in JSON output of macro errors now points the actual

source file rather than the previous format of .][70969]

Note: this may not point to a file that actually exists on the user's system.

- [The minimum required external LLVM version has been bumped to LLVM 8.][71147]

- [mem::{zeroed, uninitialised} will now panic when used with types that do

not allow zero initialization such as NonZeroU8.][66059] This was

previously a warning.

- [In 1.45.0 (the next release) converting a f64 to u32 using the as

operator has been defined as a saturating operation.][71269] This was previously

undefined behaviour, but you can use the {f64, f32}::to_int_unchecked methods to

continue using the current behaviour, which may be desirable in rare performance

sensitive situations.

Internal Only

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

These changes provide no direct user facing benefits, but represent significant

improvements to the internals and overall performance of rustc and

related tools.

- [dep_graph Avoid allocating a set on when the number reads are small.][69778]

- [Replace big JS dict with JSON parsing.][71250]

[69373]: https://github.com/rust-lang/rust/pull/69373/

[66059]: https://github.com/rust-lang/rust/pull/66059/

[68191]: https://github.com/rust-lang/rust/pull/68191/

[68899]: https://github.com/rust-lang/rust/pull/68899/

[71147]: https://github.com/rust-lang/rust/pull/71147/

[71250]: https://github.com/rust-lang/rust/pull/71250/

[70937]: https://github.com/rust-lang/rust/pull/70937/

[70969]: https://github.com/rust-lang/rust/pull/70969/

[70632]: https://github.com/rust-lang/rust/pull/70632/

[70281]: https://github.com/rust-lang/rust/pull/70281/

[70345]: https://github.com/rust-lang/rust/pull/70345/

[70048]: https://github.com/rust-lang/rust/pull/70048/

[70081]: https://github.com/rust-lang/rust/pull/70081/

[70156]: https://github.com/rust-lang/rust/pull/70156/

[71269]: https://github.com/rust-lang/rust/pull/71269/

[69838]: https://github.com/rust-lang/rust/pull/69838/

[69929]: https://github.com/rust-lang/rust/pull/69929/

[69661]: https://github.com/rust-lang/rust/pull/69661/

[69778]: https://github.com/rust-lang/rust/pull/69778/

[69494]: https://github.com/rust-lang/rust/pull/69494/

[69403]: https://github.com/rust-lang/rust/pull/69403/

[69033]: https://github.com/rust-lang/rust/pull/69033/

[68692]: https://github.com/rust-lang/rust/pull/68692/

[68334]: https://github.com/rust-lang/rust/pull/68334/

[67502]: https://github.com/rust-lang/rust/pull/67502/

[cargo/8062]: https://github.com/rust-lang/cargo/pull/8062/

[PathBuf::with_capacity]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.with_capacity

[PathBuf::capacity]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.capacity

[PathBuf::clear]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.clear

[PathBuf::reserve]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.reserve

[PathBuf::reserve_exact]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.reserve_exact

[PathBuf::shrink_to_fit]: https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.shrink_to_fit

[f32::to_int_unchecked]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_int_unchecked

[f64::to_int_unchecked]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_int_unchecked

[Layout::align_to]: https://doc.rust-lang.org/std/alloc/struct.Layout.html#method.align_to

[Layout::pad_to_align]: https://doc.rust-lang.org/std/alloc/struct.Layout.html#method.pad_to_align

[Layout::array]: https://doc.rust-lang.org/std/alloc/struct.Layout.html#method.array

[Layout::extend]: https://doc.rust-lang.org/std/alloc/struct.Layout.html#method.extend