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Allow #[must_use] on traits #55663

Merged
merged 6 commits into from
Nov 20, 2018
Merged

Allow #[must_use] on traits #55663

merged 6 commits into from
Nov 20, 2018

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varkor
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@varkor varkor commented Nov 3, 2018

Addresses #55506, but we'll probably want to add it to some library traits like Iterator before the issue is considered fixed. Fixes #51560.

#[must_use] is already permitted on traits, with no effect, so this seems like a bug fix, but I might be overlooking something. This currently warns for impl Trait or dyn Trait when the Trait is #[must_use] (although I don't think the latter is currently possible, so it's simply future-proofed).

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r? @nikomatsakis

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Nov 3, 2018
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TimNN commented Nov 13, 2018

Ping from triage @nikomatsakis / @rust-lang/compiler: This PR requires your review.

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@bors r+

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bors commented Nov 15, 2018

📌 Commit 17020e711ce0a634f98122370917943947e66777 has been approved by estebank

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 15, 2018
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@bors r-

This caused a failure in the rollup:

[00:20:51] error[E0507]: cannot move out of an `Rc`
[00:20:51]   --> librustc_lint/unused.rs:71:43
[00:20:51]    |
[00:20:51] 71 |                     for (predicate, _) in cx.tcx.predicates_of(def).predicates {
[00:20:51]    |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of an `Rc`
[00:20:52] error: aborting due to previous error

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 15, 2018
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varkor commented Nov 19, 2018

@bors r=estebank

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bors commented Nov 19, 2018

📌 Commit 0ab70fa has been approved by estebank

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 19, 2018
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varkor commented Nov 19, 2018

Forgot to push...

@bors r=estebank

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bors commented Nov 19, 2018

📌 Commit 737dec0 has been approved by estebank

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bors commented Nov 20, 2018

⌛ Testing commit 737dec0 with merge d0c9930a43bbdda941c819cfafe166e8908b2828...

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bors commented Nov 20, 2018

💔 Test failed - status-travis

@bors bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 20, 2018
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The job dist-mips64el-linux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.
[00:04:49] [RUSTC-TIMING] rustc_rayon_core test:false 2.026
[00:04:49]    Compiling rustc-rayon v0.1.1
[00:04:52] [RUSTC-TIMING] rustc_rayon test:false 2.867
[00:04:52]    Compiling rustc_data_structures v0.0.0 (/checkout/src/librustc_data_structures)
No output has been received in the last 30m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

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@bors retry (30min timeout)

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 20, 2018
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bors commented Nov 20, 2018

⌛ Testing commit 737dec0 with merge 3991bfb...

bors added a commit that referenced this pull request Nov 20, 2018
Allow #[must_use] on traits

Addresses #55506, but we'll probably want to add it to some library traits like `Iterator` before the issue is considered fixed. Fixes #51560.

`#[must_use]` is already permitted on traits, with no effect, so this seems like a bug fix, but I might be overlooking something. This currently warns for `impl Trait` or `dyn Trait` when the `Trait` is `#[must_use]` (although I don't think the latter is currently possible, so it's simply future-proofed).
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bors commented Nov 20, 2018

☀️ Test successful - status-appveyor, status-travis
Approved by: estebank
Pushing 3991bfb to master...

@bors bors merged commit 737dec0 into rust-lang:master Nov 20, 2018
@varkor varkor deleted the must_use-traits branch November 20, 2018 18:26
@Havvy Havvy added the relnotes Marks issues that should be documented in the release notes of the next release. label Nov 28, 2018
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 19, 2019
Changelog:
Version 1.32.0 (2019-01-17)
==========================

Language
--------
#### 2018 edition
- [You can now use the `?` operator in macro definitions.][56245] The `?`
  operator allows you to specify zero or one repetitions similar to the `*` and
  `+` operators.
- [Module paths with no leading keyword like `super`, `self`, or `crate`, will
  now always resolve to the item (`enum`, `struct`, etc.) available in the
  module if present, before resolving to a external crate or an item the prelude.][56759]
  E.g.
  ```rust
  enum Color { Red, Green, Blue }

  use Color::*;
  ```

#### All editions
- [You can now match against `PhantomData<T>` types.][55837]
- [You can now match against literals in macros with the `literal`
  specifier.][56072] This will match against a literal of any type.
  E.g. `1`, `'A'`, `"Hello World"`
- [Self can now be used as a constructor and pattern for unit and tuple structs.][56365] E.g.
  ```rust
  struct Point(i32, i32);

  impl Point {
      pub fn new(x: i32, y: i32) -> Self {
          Self(x, y)
      }

      pub fn is_origin(&self) -> bool {
          match self {
              Self(0, 0) => true,
              _ => false,
          }
      }
  }
  ```
- [Self can also now be used in type definitions.][56366] E.g.
  ```rust
  enum List<T>
  where
      Self: PartialOrd<Self> // can write `Self` instead of `List<T>`
  {
      Nil,
      Cons(T, Box<Self>) // likewise here
  }
  ```
- [You can now mark traits with `#[must_use]`.][55663] This provides a warning if
  a `impl Trait` or `dyn Trait` is returned and unused in the program.

Compiler
--------
- [The default allocator has changed from jemalloc to the default allocator on
  your system.][55238] The compiler itself on Linux & macOS will still use
  jemalloc, but programs compiled with it will use the system allocator.
- [Added the `aarch64-pc-windows-msvc` target.][55702]

Libraries
---------
- [`PathBuf` now implements `FromStr`.][55148]
- [`Box<[T]>` now implements `FromIterator<T>`.][55843]
- [The `dbg!` macro has been stabilized.][56395] This macro enables you to
  easily debug expressions in your rust program. E.g.
  ```rust
  let a = 2;
  let b = dbg!(a * 2) + 1;
  //      ^-- prints: [src/main.rs:4] a * 2 = 4
  assert_eq!(b, 5);
  ```

The following APIs are now `const` functions and can be used in a
`const` context.

- [`Cell::as_ptr`]
- [`UnsafeCell::get`]
- [`char::is_ascii`]
- [`iter::empty`]
- [`ManuallyDrop::new`]
- [`ManuallyDrop::into_inner`]
- [`RangeInclusive::start`]
- [`RangeInclusive::end`]
- [`NonNull::as_ptr`]
- [`slice::as_ptr`]
- [`str::as_ptr`]
- [`Duration::as_secs`]
- [`Duration::subsec_millis`]
- [`Duration::subsec_micros`]
- [`Duration::subsec_nanos`]
- [`CStr::as_ptr`]
- [`Ipv4Addr::is_unspecified`]
- [`Ipv6Addr::new`]
- [`Ipv6Addr::octets`]

Stabilized APIs
---------------
- [`i8::to_be_bytes`]
- [`i8::to_le_bytes`]
- [`i8::to_ne_bytes`]
- [`i8::from_be_bytes`]
- [`i8::from_le_bytes`]
- [`i8::from_ne_bytes`]
- [`i16::to_be_bytes`]
- [`i16::to_le_bytes`]
- [`i16::to_ne_bytes`]
- [`i16::from_be_bytes`]
- [`i16::from_le_bytes`]
- [`i16::from_ne_bytes`]
- [`i32::to_be_bytes`]
- [`i32::to_le_bytes`]
- [`i32::to_ne_bytes`]
- [`i32::from_be_bytes`]
- [`i32::from_le_bytes`]
- [`i32::from_ne_bytes`]
- [`i64::to_be_bytes`]
- [`i64::to_le_bytes`]
- [`i64::to_ne_bytes`]
- [`i64::from_be_bytes`]
- [`i64::from_le_bytes`]
- [`i64::from_ne_bytes`]
- [`i128::to_be_bytes`]
- [`i128::to_le_bytes`]
- [`i128::to_ne_bytes`]
- [`i128::from_be_bytes`]
- [`i128::from_le_bytes`]
- [`i128::from_ne_bytes`]
- [`isize::to_be_bytes`]
- [`isize::to_le_bytes`]
- [`isize::to_ne_bytes`]
- [`isize::from_be_bytes`]
- [`isize::from_le_bytes`]
- [`isize::from_ne_bytes`]
- [`u8::to_be_bytes`]
- [`u8::to_le_bytes`]
- [`u8::to_ne_bytes`]
- [`u8::from_be_bytes`]
- [`u8::from_le_bytes`]
- [`u8::from_ne_bytes`]
- [`u16::to_be_bytes`]
- [`u16::to_le_bytes`]
- [`u16::to_ne_bytes`]
- [`u16::from_be_bytes`]
- [`u16::from_le_bytes`]
- [`u16::from_ne_bytes`]
- [`u32::to_be_bytes`]
- [`u32::to_le_bytes`]
- [`u32::to_ne_bytes`]
- [`u32::from_be_bytes`]
- [`u32::from_le_bytes`]
- [`u32::from_ne_bytes`]
- [`u64::to_be_bytes`]
- [`u64::to_le_bytes`]
- [`u64::to_ne_bytes`]
- [`u64::from_be_bytes`]
- [`u64::from_le_bytes`]
- [`u64::from_ne_bytes`]
- [`u128::to_be_bytes`]
- [`u128::to_le_bytes`]
- [`u128::to_ne_bytes`]
- [`u128::from_be_bytes`]
- [`u128::from_le_bytes`]
- [`u128::from_ne_bytes`]
- [`usize::to_be_bytes`]
- [`usize::to_le_bytes`]
- [`usize::to_ne_bytes`]
- [`usize::from_be_bytes`]
- [`usize::from_le_bytes`]
- [`usize::from_ne_bytes`]

Cargo
-----
- [You can now run `cargo c` as an alias for `cargo check`.][cargo/6218]
- [Usernames are now allowed in alt registry URLs.][cargo/6242]

Misc
----
- [`libproc_macro` has been added to the `rust-src` distribution.][55280]

Compatibility Notes
-------------------
- [The argument types for AVX's
  `_mm256_stream_si256`, `_mm256_stream_pd`, `_mm256_stream_ps`][55610] have
  been changed from `*const` to `*mut` as the previous implementation
  was unsound.


[55148]: rust-lang/rust#55148
[55238]: rust-lang/rust#55238
[55280]: rust-lang/rust#55280
[55610]: rust-lang/rust#55610
[55663]: rust-lang/rust#55663
[55702]: https://github.com/rust-lag/rust/pull/55702/
[55837]: rust-lang/rust#55837
[55843]: rust-lang/rust#55843
[56072]: rust-lang/rust#56072
[56245]: rust-lang/rust#56245
[56365]: https:/ttps://github.com/rust-lang/rust/pull/56395/
[56759]: rust-lang/rust#56759
[cargo/6218]: rust-lang/cargo#6218
[cargo/6242]: rust-lang/cargo#6242
[`CStr::as_ptr`]: https://doc.rust-`Duration::as_secs`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_secs
[`Duration::subsec_micros`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.subsec_micros
[`Duration::subsec_millis`]: https://doc.rust-lang.org/sct.Duration.html#method.subsec_nanos
[`Ipv4Addr::is_unspecified`]: https://doc.rust-lang.org/std/net/struct.Ipv4Addr.html#method.is_unspecified
[`Ipv6Addr::new`]: https://doc.rust-lang.org/std/net/struct.Ipv6Addr.html#method.new
[`Ipv6Addr::octets`]: httpw`]: https://doc.rust-lang.org/std/mem/struct.ManuallyDrop.html#method.new
[`NonNull::as_ptr`]: https://doc.rust-lang.org/std/ptr/struct.NonNull.html#method.as_ptr
[`RangeInclusive::end`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html#method.end
[`RangeInclusive::start`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html#method.start
[`UnsafeCell::get`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html#method.get
[`slice::as_ptr`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_ptr
[`char::is_ascii`]: https://doc.rust-lang.org/std/primitive.char.html#method.is_ascii
[`i128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_be_bytes
[`i128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_le_bytes
[`i128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_ne_bytes
[`i128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_be_bytes
[`i128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_le_bytes
[`i128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_ne_bytes
[`i16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_be_bytes
[`i16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_le_bytes
[`i16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_ne_bytes
[`i16::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_be_bytes
[`i16::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_le_bytes
[`i16::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_ne_bytes
[`i32::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_be_bytes
[`i32::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_le_bytes
[`i32::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_ne_bytes
[`i32::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_be_bytes
[`i32::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_le_bytes
[`i32::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_ne_bytes
[`i64::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_be_bytes
[`i64::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_le_bytes
[`i64::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_ne_bytes
[`i64::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_be_bytes
[`i64::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_le_bytes
[`i64::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_ne_bytes
[`i8::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_be_bytes
[`i8::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_le_bytes
[`i8::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_ne_bytes
[`i8::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_be_bytes
[`i8::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_le_bytes
[`i8::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_ne_bytes
[`isize::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_be_bytes
[`isize::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_le_bytes
[`isize::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_ne_bytes
[`isize::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_be_bytes
[`isize::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_le_bytes
[`isize::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_ne_bytes
[`iter::empty`]: https://doc.rust-lang.org/std/iter/fn.empty.html
[`str::as_ptr`]: https://doc.rust-lang.org/std/primitive.str.html#method.as_ptr
[`u128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_be_bytes
[`u128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_le_bytes
[`u128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_ne_bytes
[`u128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_be_bytes
[`u128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_le_bytes
[`u128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_ne_bytes
[`u16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_be_bytes
[`u16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_le_bytes
[`u16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_ne_bytes
[`u16::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_be_bytes
[`u16::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_le_bytes
[`u16::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_ne_bytes
[`u32::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_be_bytes
[`u32::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_le_bytes
[`u32::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_ne_bytes
[`u32::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_be_bytes
[`u32::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_le_bytes
[`u32::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_ne_bytes
[`u64::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_be_bytes
[`u64::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_le_bytes
[`u64::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_ne_bytes
[`u64::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_be_bytes
[`u64::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_le_bytes
[`u64::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_ne_bytes
[`u8::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_be_bytes
[`u8::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_le_bytes
[`u8::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_ne_bytes
[`u8::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_be_bytes
[`u8::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_le_bytes
[`u8::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ne_bytes
[`usize::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_be_bytes
[`usize::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_le_bytes
[`usize::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_ne_bytes
[`usize::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_be_bytes
[`usize::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_le_bytes
[`usize::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_ne_bytes
@Centril Centril added this to the 1.32 milestone Apr 26, 2019
jperkin pushed a commit to TritonDataCenter/pkgsrc that referenced this pull request Jun 20, 2019
Changelog:
Version 1.32.0 (2019-01-17)
==========================

Language
--------
#### 2018 edition
- [You can now use the `?` operator in macro definitions.][56245] The `?`
  operator allows you to specify zero or one repetitions similar to the `*` and
  `+` operators.
- [Module paths with no leading keyword like `super`, `self`, or `crate`, will
  now always resolve to the item (`enum`, `struct`, etc.) available in the
  module if present, before resolving to a external crate or an item the prelude.][56759]
  E.g.
  ```rust
  enum Color { Red, Green, Blue }

  use Color::*;
  ```

#### All editions
- [You can now match against `PhantomData<T>` types.][55837]
- [You can now match against literals in macros with the `literal`
  specifier.][56072] This will match against a literal of any type.
  E.g. `1`, `'A'`, `"Hello World"`
- [Self can now be used as a constructor and pattern for unit and tuple structs.][56365] E.g.
  ```rust
  struct Point(i32, i32);

  impl Point {
      pub fn new(x: i32, y: i32) -> Self {
          Self(x, y)
      }

      pub fn is_origin(&self) -> bool {
          match self {
              Self(0, 0) => true,
              _ => false,
          }
      }
  }
  ```
- [Self can also now be used in type definitions.][56366] E.g.
  ```rust
  enum List<T>
  where
      Self: PartialOrd<Self> // can write `Self` instead of `List<T>`
  {
      Nil,
      Cons(T, Box<Self>) // likewise here
  }
  ```
- [You can now mark traits with `#[must_use]`.][55663] This provides a warning if
  a `impl Trait` or `dyn Trait` is returned and unused in the program.

Compiler
--------
- [The default allocator has changed from jemalloc to the default allocator on
  your system.][55238] The compiler itself on Linux & macOS will still use
  jemalloc, but programs compiled with it will use the system allocator.
- [Added the `aarch64-pc-windows-msvc` target.][55702]

Libraries
---------
- [`PathBuf` now implements `FromStr`.][55148]
- [`Box<[T]>` now implements `FromIterator<T>`.][55843]
- [The `dbg!` macro has been stabilized.][56395] This macro enables you to
  easily debug expressions in your rust program. E.g.
  ```rust
  let a = 2;
  let b = dbg!(a * 2) + 1;
  //      ^-- prints: [src/main.rs:4] a * 2 = 4
  assert_eq!(b, 5);
  ```

The following APIs are now `const` functions and can be used in a
`const` context.

- [`Cell::as_ptr`]
- [`UnsafeCell::get`]
- [`char::is_ascii`]
- [`iter::empty`]
- [`ManuallyDrop::new`]
- [`ManuallyDrop::into_inner`]
- [`RangeInclusive::start`]
- [`RangeInclusive::end`]
- [`NonNull::as_ptr`]
- [`slice::as_ptr`]
- [`str::as_ptr`]
- [`Duration::as_secs`]
- [`Duration::subsec_millis`]
- [`Duration::subsec_micros`]
- [`Duration::subsec_nanos`]
- [`CStr::as_ptr`]
- [`Ipv4Addr::is_unspecified`]
- [`Ipv6Addr::new`]
- [`Ipv6Addr::octets`]

Stabilized APIs
---------------
- [`i8::to_be_bytes`]
- [`i8::to_le_bytes`]
- [`i8::to_ne_bytes`]
- [`i8::from_be_bytes`]
- [`i8::from_le_bytes`]
- [`i8::from_ne_bytes`]
- [`i16::to_be_bytes`]
- [`i16::to_le_bytes`]
- [`i16::to_ne_bytes`]
- [`i16::from_be_bytes`]
- [`i16::from_le_bytes`]
- [`i16::from_ne_bytes`]
- [`i32::to_be_bytes`]
- [`i32::to_le_bytes`]
- [`i32::to_ne_bytes`]
- [`i32::from_be_bytes`]
- [`i32::from_le_bytes`]
- [`i32::from_ne_bytes`]
- [`i64::to_be_bytes`]
- [`i64::to_le_bytes`]
- [`i64::to_ne_bytes`]
- [`i64::from_be_bytes`]
- [`i64::from_le_bytes`]
- [`i64::from_ne_bytes`]
- [`i128::to_be_bytes`]
- [`i128::to_le_bytes`]
- [`i128::to_ne_bytes`]
- [`i128::from_be_bytes`]
- [`i128::from_le_bytes`]
- [`i128::from_ne_bytes`]
- [`isize::to_be_bytes`]
- [`isize::to_le_bytes`]
- [`isize::to_ne_bytes`]
- [`isize::from_be_bytes`]
- [`isize::from_le_bytes`]
- [`isize::from_ne_bytes`]
- [`u8::to_be_bytes`]
- [`u8::to_le_bytes`]
- [`u8::to_ne_bytes`]
- [`u8::from_be_bytes`]
- [`u8::from_le_bytes`]
- [`u8::from_ne_bytes`]
- [`u16::to_be_bytes`]
- [`u16::to_le_bytes`]
- [`u16::to_ne_bytes`]
- [`u16::from_be_bytes`]
- [`u16::from_le_bytes`]
- [`u16::from_ne_bytes`]
- [`u32::to_be_bytes`]
- [`u32::to_le_bytes`]
- [`u32::to_ne_bytes`]
- [`u32::from_be_bytes`]
- [`u32::from_le_bytes`]
- [`u32::from_ne_bytes`]
- [`u64::to_be_bytes`]
- [`u64::to_le_bytes`]
- [`u64::to_ne_bytes`]
- [`u64::from_be_bytes`]
- [`u64::from_le_bytes`]
- [`u64::from_ne_bytes`]
- [`u128::to_be_bytes`]
- [`u128::to_le_bytes`]
- [`u128::to_ne_bytes`]
- [`u128::from_be_bytes`]
- [`u128::from_le_bytes`]
- [`u128::from_ne_bytes`]
- [`usize::to_be_bytes`]
- [`usize::to_le_bytes`]
- [`usize::to_ne_bytes`]
- [`usize::from_be_bytes`]
- [`usize::from_le_bytes`]
- [`usize::from_ne_bytes`]

Cargo
-----
- [You can now run `cargo c` as an alias for `cargo check`.][cargo/6218]
- [Usernames are now allowed in alt registry URLs.][cargo/6242]

Misc
----
- [`libproc_macro` has been added to the `rust-src` distribution.][55280]

Compatibility Notes
-------------------
- [The argument types for AVX's
  `_mm256_stream_si256`, `_mm256_stream_pd`, `_mm256_stream_ps`][55610] have
  been changed from `*const` to `*mut` as the previous implementation
  was unsound.


[55148]: rust-lang/rust#55148
[55238]: rust-lang/rust#55238
[55280]: rust-lang/rust#55280
[55610]: rust-lang/rust#55610
[55663]: rust-lang/rust#55663
[55702]: https://github.com/rust-lag/rust/pull/55702/
[55837]: rust-lang/rust#55837
[55843]: rust-lang/rust#55843
[56072]: rust-lang/rust#56072
[56245]: rust-lang/rust#56245
[56365]: https:/ttps://github.com/rust-lang/rust/pull/56395/
[56759]: rust-lang/rust#56759
[cargo/6218]: rust-lang/cargo#6218
[cargo/6242]: rust-lang/cargo#6242
[`CStr::as_ptr`]: https://doc.rust-`Duration::as_secs`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_secs
[`Duration::subsec_micros`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.subsec_micros
[`Duration::subsec_millis`]: https://doc.rust-lang.org/sct.Duration.html#method.subsec_nanos
[`Ipv4Addr::is_unspecified`]: https://doc.rust-lang.org/std/net/struct.Ipv4Addr.html#method.is_unspecified
[`Ipv6Addr::new`]: https://doc.rust-lang.org/std/net/struct.Ipv6Addr.html#method.new
[`Ipv6Addr::octets`]: httpw`]: https://doc.rust-lang.org/std/mem/struct.ManuallyDrop.html#method.new
[`NonNull::as_ptr`]: https://doc.rust-lang.org/std/ptr/struct.NonNull.html#method.as_ptr
[`RangeInclusive::end`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html#method.end
[`RangeInclusive::start`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html#method.start
[`UnsafeCell::get`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html#method.get
[`slice::as_ptr`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_ptr
[`char::is_ascii`]: https://doc.rust-lang.org/std/primitive.char.html#method.is_ascii
[`i128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_be_bytes
[`i128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_le_bytes
[`i128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_ne_bytes
[`i128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_be_bytes
[`i128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_le_bytes
[`i128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_ne_bytes
[`i16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_be_bytes
[`i16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_le_bytes
[`i16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_ne_bytes
[`i16::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_be_bytes
[`i16::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_le_bytes
[`i16::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.to_ne_bytes
[`i32::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_be_bytes
[`i32::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_le_bytes
[`i32::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.from_ne_bytes
[`i32::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_be_bytes
[`i32::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_le_bytes
[`i32::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i32.html#method.to_ne_bytes
[`i64::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_be_bytes
[`i64::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_le_bytes
[`i64::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.from_ne_bytes
[`i64::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_be_bytes
[`i64::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_le_bytes
[`i64::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i64.html#method.to_ne_bytes
[`i8::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_be_bytes
[`i8::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_le_bytes
[`i8::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.from_ne_bytes
[`i8::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_be_bytes
[`i8::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_le_bytes
[`i8::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.to_ne_bytes
[`isize::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_be_bytes
[`isize::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_le_bytes
[`isize::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.from_ne_bytes
[`isize::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_be_bytes
[`isize::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_le_bytes
[`isize::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_ne_bytes
[`iter::empty`]: https://doc.rust-lang.org/std/iter/fn.empty.html
[`str::as_ptr`]: https://doc.rust-lang.org/std/primitive.str.html#method.as_ptr
[`u128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_be_bytes
[`u128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_le_bytes
[`u128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_ne_bytes
[`u128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_be_bytes
[`u128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_le_bytes
[`u128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_ne_bytes
[`u16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_be_bytes
[`u16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_le_bytes
[`u16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_ne_bytes
[`u16::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_be_bytes
[`u16::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_le_bytes
[`u16::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.to_ne_bytes
[`u32::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_be_bytes
[`u32::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_le_bytes
[`u32::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.from_ne_bytes
[`u32::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_be_bytes
[`u32::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_le_bytes
[`u32::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u32.html#method.to_ne_bytes
[`u64::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_be_bytes
[`u64::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_le_bytes
[`u64::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.from_ne_bytes
[`u64::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_be_bytes
[`u64::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_le_bytes
[`u64::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u64.html#method.to_ne_bytes
[`u8::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_be_bytes
[`u8::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_le_bytes
[`u8::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.from_ne_bytes
[`u8::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_be_bytes
[`u8::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_le_bytes
[`u8::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u8.html#method.to_ne_bytes
[`usize::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_be_bytes
[`usize::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_le_bytes
[`usize::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.from_ne_bytes
[`usize::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_be_bytes
[`usize::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_le_bytes
[`usize::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.usize.html#method.to_ne_bytes
Centril added a commit to Centril/rust that referenced this pull request Jun 29, 2019
…tril

Extend the #[must_use] lint to boxed types

Fixes rust-lang#55506 (comment) (cc @Nemo157).

This should have been included as part of rust-lang#55663, but was overlooked.
Centril added a commit to Centril/rust that referenced this pull request Jun 30, 2019
…tril

Extend the #[must_use] lint to boxed types

Fixes rust-lang#55506 (comment) (cc @Nemo157).

This should have been included as part of rust-lang#55663, but was overlooked.
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It is too easy to lose #[must_use] annotations when using impl Trait, leading to footguns
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