Cautiously add IntoIterator for arrays by value #84147

cuviper · 2021-04-13T00:10:09Z

Add the attribute described in #84133, #[rustc_skip_array_during_method_dispatch], which effectively hides a trait from method dispatch when the receiver type is an array.

Then cherry-pick IntoIterator for [T; N] from #65819 and gate it with that attribute. Arrays can now be used as IntoIterator normally, but array.into_iter() has edition-dependent behavior, returning slice::Iter for 2015 and 2018 editions, or array::IntoIter for 2021 and later.

r? @nikomatsakis
cc @LukasKalbertodt @rust-lang/libs

Mark-Simulacrum · 2021-04-13T00:15:35Z

@bors try @rust-timer queue

Let's get a perf build kicked off (mostly because why not), and additionally collect some try artifacts for a possible crater run (though the queue is a bit long right now).

rust-timer · 2021-04-13T00:15:36Z

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

bors · 2021-04-13T00:15:44Z

⌛ Trying commit 825ca8d73698753903a95b6448ac9785cf9db67d with merge 559cfb990fcbcf093cb2f03a253eec5b7822e126...

src/test/ui/iterators/array-of-ranges.stderr

bors · 2021-04-13T01:16:16Z

☀️ Try build successful - checks-actions
Build commit: 559cfb990fcbcf093cb2f03a253eec5b7822e126 (559cfb990fcbcf093cb2f03a253eec5b7822e126)

rust-timer · 2021-04-13T01:16:17Z

Queued 559cfb990fcbcf093cb2f03a253eec5b7822e126 with parent d0695c9, future comparison URL.

rust-timer · 2021-04-13T04:23:11Z

Finished benchmarking try commit (559cfb990fcbcf093cb2f03a253eec5b7822e126): comparison url.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying rollup- to bors.

Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf

nikomatsakis

from the POV of the code, this looks good to me

cuviper · 2021-04-13T17:57:39Z

r? @m-ou-se for libs? I suppose this needs FCP for the immediate stabilization.

nikomatsakis · 2021-04-13T17:59:35Z

I think some kind of lang FCP is required, at least.

scottmcm · 2021-04-13T19:14:11Z

Being able to finally have this impl would be a huge win, so I'll make the motion that we do this.

@rfcbot fcp merge

See the first two comments in #84133 for more details about it.

It's my understanding that the name resolution hack:

Means that the impl is available everywhere, so things like .chain([1, 2, 3]) will start working.
Affects only method resolution, so IntoIterator::into_iter([1, 2, 3]) will work on all editions.
Is restricted to only array-typed receivers, so cannot affect any user types or other containers.
And that's not after deref, so this will still give slice iterators for &[impl Copy; N].
Could still be removed in future, as the addition is officially "minor" under the evolution RFC.
(just that it's heavily impactful in practice, so we've wanted to be extra careful.)

This is tagged both libs+lang, which seems appropriate. Libs clearly needs to sign off on the trait impl, and we discussed in a previous lang meeting that anything with user-visible effects on language semantics for stable APIs should have lang FCPs, even if they're implemented as not-planned-to-ever-stabilize rustc_* attributes.

rfcbot · 2021-04-13T19:14:13Z

nikomatsakis · 2021-04-13T19:17:04Z

@scottmcm

Is restricted to only array-typed receivers, so cannot affect any existing code.

I'm not sure what this means. Existing code is not affected, but that's because of the behavior is tied to an edition. That is, in Rust 2021, code that does array.into_iter()will behave differently than it would in Rust 2018.

nikomatsakis · 2021-04-13T19:17:15Z

@rfcbot reviewed

bors · 2021-04-25T07:26:54Z

⌛ Testing commit f6a90ca with merge 13a2615...

bors · 2021-04-25T09:57:08Z

☀️ Test successful - checks-actions
Approved by: nikomatsakis,m-ou-se
Pushing 13a2615 to master...

Point out that behavior might be switched on 2015 and 2018 too one day Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already. cc rust-lang#25725, rust-lang#65819, rust-lang#66145, rust-lang#84147 , and rust-lang#84133 (comment)

Pkgsrc changes: * Bump bootstrap requirements to 1.52.1 * Adjust patches, adapt to upstream changes, adjust cargo checksums * If using an external llvm, require >= 10.0 Upsteream changes: Version 1.53.0 (2021-06-17) ============================ Language ----------------------- - [You can now use unicode for identifiers.][83799] This allows multilingual identifiers but still doesn't allow glyphs that are not considered characters such as `#` (diamond) or `<U+1F980>` (crab). More specifically you can now use any identifier that matches the UAX #31 "Unicode Identifier and Pattern Syntax" standard. This is the same standard as languages like Python, however Rust uses NFC normalization which may be different from other languages. - [You can now specify "or patterns" inside pattern matches.][79278] Previously you could only use `|` (OR) on complete patterns. E.g. ```rust let x = Some(2u8); // Before matches!(x, Some(1) | Some(2)); // Now matches!(x, Some(1 | 2)); ``` - [Added the `:pat_param` `macro_rules!` matcher.][83386] This matcher has the same semantics as the `:pat` matcher. This is to allow `:pat` to change semantics to being a pattern fragment in a future edition. Compiler ----------------------- - [Updated the minimum external LLVM version to LLVM 10.][83387] - [Added Tier 3\* support for the `wasm64-unknown-unknown` target.][80525] - [Improved debuginfo for closures and async functions on Windows MSVC.][83941] \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries ----------------------- - [Abort messages will now forward to `android_set_abort_message` on Android platforms when available.][81469] - [`slice::IterMut<'_, T>` now implements `AsRef<[T]>`][82771] - [Arrays of any length now implement `IntoIterator`.][84147] Currently calling `.into_iter()` as a method on an array will return `impl Iterator<Item=&T>`, but this may change in a future edition to change `Item` to `T`. Calling `IntoIterator::into_iter` directly on arrays will provide `impl Iterator<Item=T>` as expected. - [`leading_zeros`, and `trailing_zeros` are now available on all `NonZero` integer types.][84082] - [`{f32, f64}::from_str` now parse and print special values (`NaN`, `-0`) according to IEEE RFC 754.][78618] - [You can now index into slices using `(Bound<usize>, Bound<usize>)`.][77704] - [Add the `BITS` associated constant to all numeric types.][82565] Stabilised APIs --------------- - [`AtomicBool::fetch_update`] - [`AtomicPtr::fetch_update`] - [`BTreeMap::retain`] - [`BTreeSet::retain`] - [`BufReader::seek_relative`] - [`DebugStruct::non_exhaustive`] - [`Duration::MAX`] - [`Duration::ZERO`] - [`Duration::is_zero`] - [`Duration::saturating_add`] - [`Duration::saturating_mul`] - [`Duration::saturating_sub`] - [`ErrorKind::Unsupported`] - [`Option::insert`] - [`Ordering::is_eq`] - [`Ordering::is_ge`] - [`Ordering::is_gt`] - [`Ordering::is_le`] - [`Ordering::is_lt`] - [`Ordering::is_ne`] - [`OsStr::is_ascii`] - [`OsStr::make_ascii_lowercase`] - [`OsStr::make_ascii_uppercase`] - [`OsStr::to_ascii_lowercase`] - [`OsStr::to_ascii_uppercase`] - [`Peekable::peek_mut`] - [`Rc::decrement_strong_count`] - [`Rc::increment_strong_count`] - [`Vec::extend_from_within`] - [`array::from_mut`] - [`array::from_ref`] - [`char::MAX`] - [`char::REPLACEMENT_CHARACTER`] - [`char::UNICODE_VERSION`] - [`char::decode_utf16`] - [`char::from_digit`] - [`char::from_u32_unchecked`] - [`char::from_u32`] - [`cmp::max_by_key`] - [`cmp::max_by`] - [`cmp::min_by_key`] - [`cmp::min_by`] - [`f32::is_subnormal`] - [`f64::is_subnormal`] Cargo ----------------------- - [Cargo now supports git repositories where the default `HEAD` branch is not "master".][cargo/9392] This also includes a switch to the version 3 `Cargo.lock` format which can handle default branches correctly. - [macOS targets now default to `unpacked` split-debuginfo.][cargo/9298] - [The `authors` field is no longer included in `Cargo.toml` for new projects.][cargo/9282] Rustdoc ----------------------- - [Added the `rustdoc::bare_urls` lint that warns when you have URLs without hyperlinks.][81764] Compatibility Notes ------------------- - [Implement token-based handling of attributes during expansion][82608] - [`Ipv4::from_str` will now reject octal format IP addresses in addition to rejecting hexadecimal IP addresses.][83652] The octal format can lead to confusion and potential security vulnerabilities and [is no longer recommended][ietf6943]. 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. - [Rework the `std::sys::windows::alloc` implementation.][83065] - [rustdoc: Don't enter an infer_ctxt in get_blanket_impls for impls that aren't blanket impls.][82864] - [rustdoc: Only look at blanket impls in `get_blanket_impls`][83681] - [Rework rustdoc const type][82873] [83386]: rust-lang/rust#83386 [82771]: rust-lang/rust#82771 [84147]: rust-lang/rust#84147 [84082]: rust-lang/rust#84082 [83799]: rust-lang/rust#83799 [83681]: rust-lang/rust#83681 [83652]: rust-lang/rust#83652 [83387]: rust-lang/rust#83387 [82873]: rust-lang/rust#82873 [82864]: rust-lang/rust#82864 [82608]: rust-lang/rust#82608 [82565]: rust-lang/rust#82565 [80525]: rust-lang/rust#80525 [79278]: rust-lang/rust#79278 [78618]: rust-lang/rust#78618 [77704]: rust-lang/rust#77704 [83941]: rust-lang/rust#83941 [83065]: rust-lang/rust#83065 [81764]: rust-lang/rust#81764 [81469]: rust-lang/rust#81469 [cargo/9298]: rust-lang/cargo#9298 [cargo/9282]: rust-lang/cargo#9282 [cargo/9392]: rust-lang/cargo#9392 [`char::MAX`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.MAX [`char::REPLACEMENT_CHARACTER`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.REPLACEMENT_CHARACTER [`char::UNICODE_VERSION`]: https://doc.rust-lang.org/std/primitive.char.html#associatedconstant.UNICODE_VERSION [`char::decode_utf16`]: https://doc.rust-lang.org/std/primitive.char.html#method.decode_utf16 [`char::from_u32`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32 [`char::from_u32_unchecked`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_u32_unchecked [`char::from_digit`]: https://doc.rust-lang.org/std/primitive.char.html#method.from_digit [`AtomicBool::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicBool.html#method.fetch_update [`AtomicPtr::fetch_update`]: https://doc.rust-lang.org/std/sync/atomic/struct.AtomicPtr.html#method.fetch_update [`BTreeMap::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.retain [`BTreeSet::retain`]: https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.retain [`BufReader::seek_relative`]: https://doc.rust-lang.org/std/io/struct.BufReader.html#method.seek_relative [`DebugStruct::non_exhaustive`]: https://doc.rust-lang.org/std/fmt/struct.DebugStruct.html#method.finish_non_exhaustive [`Duration::MAX`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.MAX [`Duration::ZERO`]: https://doc.rust-lang.org/std/time/struct.Duration.html#associatedconstant.ZERO [`Duration::is_zero`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.is_zero [`Duration::saturating_add`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_add [`Duration::saturating_mul`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_mul [`Duration::saturating_sub`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.saturating_sub [`ErrorKind::Unsupported`]: https://doc.rust-lang.org/std/io/enum.ErrorKind.html#variant.Unsupported [`Option::insert`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.insert [`Ordering::is_eq`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_eq [`Ordering::is_ge`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ge [`Ordering::is_gt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_gt [`Ordering::is_le`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_le [`Ordering::is_lt`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_lt [`Ordering::is_ne`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.is_ne [`OsStr::eq_ignore_ascii_case`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.eq_ignore_ascii_case [`OsStr::is_ascii`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.is_ascii [`OsStr::make_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_lowercase [`OsStr::make_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.make_ascii_uppercase [`OsStr::to_ascii_lowercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_lowercase [`OsStr::to_ascii_uppercase`]: https://doc.rust-lang.org/std/ffi/struct.OsStr.html#method.to_ascii_uppercase [`Peekable::peek_mut`]: https://doc.rust-lang.org/std/iter/struct.Peekable.html#method.peek_mut [`Rc::decrement_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count [`Rc::increment_strong_count`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.increment_strong_count [`Vec::extend_from_within`]: https://doc.rust-lang.org/beta/std/vec/struct.Vec.html#method.extend_from_within [`array::from_mut`]: https://doc.rust-lang.org/beta/std/array/fn.from_mut.html [`array::from_ref`]: https://doc.rust-lang.org/beta/std/array/fn.from_ref.html [`cmp::max_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by_key.html [`cmp::max_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.max_by.html [`cmp::min_by_key`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by_key.html [`cmp::min_by`]: https://doc.rust-lang.org/beta/std/cmp/fn.min_by.html [`f32::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal [`f64::is_subnormal`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_subnormal [ietf6943]: https://datatracker.ietf.org/doc/html/rfc6943#section-3.1.1

…, r=estebank Upgrade array_into_iter lint to include Deref-to-array types. Fixes rust-lang#88099 Fixes the issue mentioned here: rust-lang#84147 (comment)

rust-highfive assigned nikomatsakis Apr 13, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 13, 2021

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 13, 2021

cuviper commented Apr 13, 2021

View reviewed changes

src/test/ui/iterators/array-of-ranges.stderr Show resolved Hide resolved

cuviper mentioned this pull request Apr 13, 2021

Stabilize impl From<[(K, V); N]> for HashMap (and friends) #84111

Merged

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 13, 2021

nikomatsakis mentioned this pull request Apr 13, 2021

Add IntoIterator impl for arrays by value (for [T; N]) #65819

Closed

5 tasks

nikomatsakis approved these changes Apr 13, 2021

View reviewed changes

rust-highfive assigned m-ou-se and unassigned nikomatsakis Apr 13, 2021

nikomatsakis added I-nominated T-lang Relevant to the language team, which will review and decide on the PR/issue. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Apr 13, 2021

nikomatsakis removed the I-nominated label Apr 13, 2021

scottmcm added the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Apr 13, 2021

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Apr 13, 2021

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Apr 25, 2021

bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 25, 2021

bors merged commit 13a2615 into rust-lang:master Apr 25, 2021

rustbot added this to the 1.53.0 milestone Apr 25, 2021

cuviper deleted the array-method-dispatch branch April 25, 2021 16:33

m-ou-se mentioned this pull request Apr 26, 2021

IntoIterator should be implemented for [T; N] not just references #25725

Closed

est31 mentioned this pull request Apr 26, 2021

Point out that behavior might be switched on 2015 and 2018 too one day #84590

Merged

apiraino removed the to-announce Announce this issue on triage meeting label Apr 29, 2021

steffahn mentioned this pull request May 2, 2021

Edition 2021 blog post rust-lang/blog.rust-lang.org#825

Merged

SkiFire13 mentioned this pull request Jul 14, 2021

rustc_skip_array_during_method_dispatch is bypassed by method calls implemented for any I: IntoIterator #87132

Closed

m-ou-se mentioned this pull request Aug 17, 2021

array_into_iter does not fire for lazy_static arrays #88099

Closed

m-ou-se mentioned this pull request Aug 30, 2021

Upgrade array_into_iter lint to include Deref-to-array types. #88512

Merged

m-ou-se mentioned this pull request Sep 3, 2021

🎉 Rust 2021 celebration and thanks #88623

Closed

lcnr mentioned this pull request Dec 11, 2021

Tracking issue for const generics (RFC 2000) #44580

Closed

16 tasks

0HyperCube mentioned this pull request Dec 28, 2021

Update intoiter syntax GraphiteEditor/Graphite#436

Merged

mattheww mentioned this pull request Feb 1, 2022

Document pre-Rust-2021 special case for IntoIterator method lookup rust-lang/reference#1154

Merged

matthiaskrgr mentioned this pull request Oct 16, 2023

ice: 'ty::Const::eval' called on a non-valtree-compatible type #116796

Closed

GrigorenkoPV mentioned this pull request Sep 2, 2024

impl AsRef<[T; N]> and AsMut<[T; N]> for [T; N] #129872

Draft

6 tasks

matthiaskrgr mentioned this pull request Nov 2, 2024

ICE: When translating generic parameters from DefId, the expected specialization failed to hold #132519

Open

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Cautiously add IntoIterator for arrays by value #84147

Cautiously add IntoIterator for arrays by value #84147

cuviper commented Apr 13, 2021

Mark-Simulacrum commented Apr 13, 2021

rust-timer commented Apr 13, 2021

bors commented Apr 13, 2021

bors commented Apr 13, 2021

rust-timer commented Apr 13, 2021

rust-timer commented Apr 13, 2021

nikomatsakis left a comment

cuviper commented Apr 13, 2021

nikomatsakis commented Apr 13, 2021

scottmcm commented Apr 13, 2021 •

edited

Loading

rfcbot commented Apr 13, 2021 •

edited by joshtriplett

Loading

nikomatsakis commented Apr 13, 2021

nikomatsakis commented Apr 13, 2021

bors commented Apr 25, 2021

bors commented Apr 25, 2021

Cautiously add IntoIterator for arrays by value #84147

Cautiously add IntoIterator for arrays by value #84147

Conversation

cuviper commented Apr 13, 2021

Mark-Simulacrum commented Apr 13, 2021

rust-timer commented Apr 13, 2021

bors commented Apr 13, 2021

bors commented Apr 13, 2021

rust-timer commented Apr 13, 2021

rust-timer commented Apr 13, 2021

nikomatsakis left a comment

Choose a reason for hiding this comment

cuviper commented Apr 13, 2021

nikomatsakis commented Apr 13, 2021

scottmcm commented Apr 13, 2021 • edited Loading

rfcbot commented Apr 13, 2021 • edited by joshtriplett Loading

nikomatsakis commented Apr 13, 2021

nikomatsakis commented Apr 13, 2021

bors commented Apr 25, 2021

bors commented Apr 25, 2021

scottmcm commented Apr 13, 2021 •

edited

Loading

rfcbot commented Apr 13, 2021 •

edited by joshtriplett

Loading