Add 1.60.0 blog post

posts/2022-04-07-Rust-1.60.0.md

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+---
+layout: post
+title: "Announcing Rust 1.60.0"
+author: The Rust Release Team
+release: true
+---
+
+The Rust team is happy to announce a new version of Rust, 1.60.0. Rust is a programming language empowering everyone to build reliable and efficient software.
+
+If you have a previous version of Rust installed via rustup, you can get 1.60.0 with:
+
+```console
+rustup update stable
+```
+
+If you don't have it already, you can [get `rustup`][install]
+from the appropriate page on our website, and check out the
+[detailed release notes for 1.60.0][notes] on GitHub.
+If you'd like to help us out by testing future releases, you might consider updating locally to use
+the beta channel (`rustup default beta`) or the nightly channel (`rustup default nightly`). Please [report] any bugs you might come across!
+
+[install]: https://www.rust-lang.org/install.html
+[notes]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1600-2022-04-07
+[report]: https://github.com/rust-lang/rust/issues/new/choose
+
+## What's in 1.60.0 stable
+
+### Instrumentation-based Code Coverage
+
+Support for LLVM-based coverage instrumentation has been stabilized in rustc, enabled with `-C instrument-coverage`. You can try this out on your code by rebuilding your code with `-Cinstrument-coverage`:
+
+```shell=
+RUSTFLAGS="-C instrument-coverage" cargo build
+```
+
+After that, you can run the resulting binary, which will produce
+a `default.profraw` file in the current directory. That can be consumed
+by the `llvm-cov` binary shipped with rustc as part of the llvm-tools-preview
+component.
+
+```shell=
+rustup component add llvm-tools-preview
+$(rustc --print sysroot)/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-profdata merge -sparse default.profraw -o default.profdata
+$(rustc --print sysroot)/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-cov show -Xdemangler=rustfilt target/debug/coverage-testing \
+    -instr-profile=default.profdata \
+    -show-line-counts-or-regions \
+    -show-instantiations
+```
+
+The above commands on a simple helloworld binary produce this annotated report, showing that each line of the input was covered.
+
+```
+    1|      1|fn main() {
+    2|      1|    println!("Hello, world!");
+    3|      1|}
+```
+
+For more details, please read the [documentation](https://doc.rust-lang.org/rustc/instrument-coverage.html) in the rustc book. The specific output format and LLVM tooling to consume it are both not guaranteed to exist in this specific form, but the baseline functionality will continue to exist for future Rust releases.
+
+### `cargo --timings`
+
+Cargo has stabilized support for collecting information on build with the `--timings` flag.
+
+```shell
+$ cargo build --timings
+   Compiling hello-world v0.1.0 (hello-world)
+      Timing report saved to target/cargo-timings/cargo-timing-20220318T174818Z.html
+    Finished dev [unoptimized + debuginfo] target(s) in 0.98s
+```
+
+The report is also copied to `target/cargo-timings/cargo-timing.html`. A report on the release build of Cargo has been put up [here](/images/2022-04-07-timing.html). These reports can be useful for improving build performance.
+More information about the timing reports may be found in the [documentation](https://doc.rust-lang.org/nightly/cargo/reference/timings.html).
+
+### New syntax for Cargo features
+
+This release introduces two new changes to improve support for [Cargo features](https://doc.rust-lang.org/cargo/reference/features.html) and how they interact with [optional dependencies](https://doc.rust-lang.org/cargo/reference/features.html#optional-dependencies): Namespaced dependencies and weak dependency features.
+
+Cargo has long supported features along with optional dependencies, as illustrated by the snippet below.
+
+```toml
+[dependencies]
+jpeg-decoder = { version = "0.1.20", default-features = false, optional = true }
+
+[features]
+# Enables parallel processing support by enabling the "rayon" feature of jpeg-decoder.
+parallel = ["jpeg-decoder/rayon"]
+```
+
+There are two things to note in this example.  First, the optional dependency `jpeg-decoder` implicitly defines a feature of the same name, which provides a means to enable the dependency. Second, the `"jpeg-decoder/rayon"` syntax enables the `rayon` feature of the `jpeg-decoder` dependency, *and* also enables the `jpeg-decoder` dependency.
+
+Namespaced features tackles the first issue that optional dependencies are implicitly exposed as part of a package's public interface. You can now use the `dep:` prefix in the `[features]` table to explicitly refer to an optional dependency. This gives you more control to define the feature corresponding to the optional dependency, and to hide optional dependencies behind more descriptive feature names.
+
+Weak dependency features tackles the second issue where the `"package-name/feature-name"` syntax would enable `package-name` if it is an optional dependency. Often this is not what you want, and starting in 1.60, you can add a ? as in `"package-name?/feature-name"` which will only enable the given feature if something else enables the optional dependency.
+
+For example, let's say we have added some serialization support to our library, and it requires enabling a corresponding feature in some optional dependencies. That can be done like this:
+
+```toml
+[dependencies]
+serde = { version = "1.0.133", optional = true }
+rgb = { version = "0.8.25", optional = true }
+
+[features]
+serde = ["dep:serde", "rgb?/serde"]
+```
+
+In this example, enabling the serde feature will enable the serde dependency. It will also enable the serde feature for the rgb dependency, but only if something else has enabled the rgb dependency.
+
+### Incremental compilation status
+
+Incremental compilation is re-enabled for the 1.60 release. The Rust team continues to work on fixing bugs in incremental, but no problems causing widespread breakage are known at this time, so we have chosen to reenable incremental compilation. Additionally, the compiler team is continuing to work on long-term strategy to avoid future problems of this kind. That process is in relatively early days, so we don't have anything to share yet on that front. 
+
+### Stabilized APIs
+
+The following methods and trait implementations are now stabilized:
+
+- [`Arc::new_cyclic`][arc_new_cyclic]
+- [`Rc::new_cyclic`][rc_new_cyclic]
+- [`slice::EscapeAscii`][slice_escape_ascii]
+- [`<[u8]>::escape_ascii`][slice_u8_escape_ascii]
+- [`u8::escape_ascii`][u8_escape_ascii]
+- [`Vec::spare_capacity_mut`][vec_spare_capacity_mut]
+- [`MaybeUninit::assume_init_drop`][assume_init_drop]
+- [`MaybeUninit::assume_init_read`][assume_init_read]
+- [`i8::abs_diff`][i8_abs_diff]
+- [`i16::abs_diff`][i16_abs_diff]
+- [`i32::abs_diff`][i32_abs_diff]
+- [`i64::abs_diff`][i64_abs_diff]
+- [`i128::abs_diff`][i128_abs_diff]
+- [`isize::abs_diff`][isize_abs_diff]
+- [`u8::abs_diff`][u8_abs_diff]
+- [`u16::abs_diff`][u16_abs_diff]
+- [`u32::abs_diff`][u32_abs_diff]
+- [`u64::abs_diff`][u64_abs_diff]
+- [`u128::abs_diff`][u128_abs_diff]
+- [`usize::abs_diff`][usize_abs_diff]
+- [`Display for io::ErrorKind`][display_error_kind]
+- [`From<u8> for ExitCode`][from_u8_exit_code]
+- [`Not for !` (the "never" type)][not_never]
+- [_Op_`Assign<$t> for Wrapping<$t>`][wrapping_assign_ops]
+- [`arch::is_aarch64_feature_detected!`][is_aarch64_feature_detected]
+
+### Other changes
+
+There are other changes in the Rust 1.60.0 release. Check out what changed in
+[Rust](https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1600-2022-04-07),
+[Cargo](https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-160-2022-04-07),
+and [Clippy](https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-160).
+
+### Contributors to 1.60.0
+
+Many people came together to create Rust 1.60.0.
+We couldn't have done it without all of you.
+[Thanks!](https://thanks.rust-lang.org/rust/1.60.0/)
+
+[arc_new_cyclic]: https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.new_cyclic
+[rc_new_cyclic]: https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.new_cyclic
+[slice_escape_ascii]: https://doc.rust-lang.org/stable/std/slice/struct.EscapeAscii.html
+[slice_u8_escape_ascii]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.escape_ascii
+[u8_escape_ascii]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.escape_ascii
+[vec_spare_capacity_mut]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.spare_capacity_mut
+[assume_init_drop]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_drop
+[assume_init_read]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_read
+[i8_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.abs_diff
+[i16_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.abs_diff
+[i32_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.abs_diff
+[i64_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.abs_diff
+[i128_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.abs_diff
+[isize_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.abs_diff
+[u8_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.abs_diff
+[u16_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.abs_diff
+[u32_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.abs_diff
+[u64_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.abs_diff
+[u128_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.abs_diff
+[usize_abs_diff]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.abs_diff
+[display_error_kind]: https://doc.rust-lang.org/stable/std/io/enum.ErrorKind.html#impl-Display
+[from_u8_exit_code]: https://doc.rust-lang.org/stable/std/process/struct.ExitCode.html#impl-From%3Cu8%3E
+[not_never]: https://doc.rust-lang.org/stable/std/primitive.never.html#impl-Not
+[wrapping_assign_ops]: https://doc.rust-lang.org/stable/std/num/struct.Wrapping.html#trait-implementations
+[is_aarch64_feature_detected]: https://doc.rust-lang.org/stable/std/arch/macro.is_aarch64_feature_detected.html