Implement tuple<->array convertions via `From` #97594

WaffleLapkin · 2022-05-31T18:44:21Z

This PR adds the following impls that convert between homogeneous tuples and arrays of the corresponding lengths:

impl<T> From<[T; 1]> for (T,) { ... }
impl<T> From<[T; 2]> for (T, T) { ... }
/* ... */
impl<T> From<[T; 12]> for (T, T, T, T, T, T, T, T, T, T, T, T) { ... }

impl<T> From<(T,)> for [T; 1] { ... }
impl<T> From<(T, T)> for [T; 2] { ... }
/* ... */
impl<T> From<(T, T, T, T, T, T, T, T, T, T, T, T)> for [T; 12] { ... }

IMO these are quite uncontroversial but note that they are, just like any other trait impls, insta-stable.

rust-highfive · 2022-05-31T18:44:23Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs to request review from a libs-api team reviewer. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

rust-highfive · 2022-05-31T18:44:25Z

r? @Mark-Simulacrum

(rust-highfive has picked a reviewer for you, use r? to override)

WaffleLapkin · 2022-05-31T18:44:42Z

r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs

WaffleLapkin · 2022-05-31T19:44:53Z

@rustbot label -S-waiting-on-review +S-waiting-on-author

library/core/src/tuple.rs

WaffleLapkin · 2022-06-02T09:24:44Z

I've removed () <-> [] impls because they break inference in the following tests:

ui/hygiene/hir-res-hygiene.rs
ui/suggestions/type-ascription-instead-of-path-2.rs
ui/issues/issue-32709.rs

They all basically do the following:

fn f() -> Result<(), ()> {
    Ok(())?; // <--
    Ok(())
}

For this to work you need to infer ?T in Result<(), ?T> having only (): From<?T>. Currently this works because the only impl From for () is the identity impl, so rustc picks it up and infers ?T = ().

IIRC this is not considered a breaking change per rust rules, because it can be fixed by adding types:

fn f() -> Result<(), ()> {
    Ok::<_, ()>(())?; 
    //^^^^^^^^^
    Ok(())
}

However I'm not sure how widespread this pattern is and if this is worth the potential breakage.

WaffleLapkin · 2022-06-02T13:16:54Z

@rustbot ready

bors · 2022-08-19T00:15:53Z

☔ The latest upstream changes (presumably #98807) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2022-08-19T13:11:26Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

camelid · 2023-02-11T04:35:47Z

ping from triage: What's the status of this PR?

scottmcm · 2023-02-12T04:47:20Z

Looks like this is old enough that it pre-dates ACPs, so I'll nominate it for libs-api to say what they want.

WaffleLapkin · 2023-02-13T07:03:08Z

@camelid pretty much what the tags say: this is waiting on a T-libs-api decision

m-ou-se · 2023-02-28T16:51:59Z

We briefly discussed this in the libs-api meeting, and we were wondering if there are any motivating use cases.

ChrisDenton · 2023-05-02T18:15:05Z

This has passed FCP and the implementation looks good to me. The only thing I would ask for is some tests that exercise this properly. Especially because this is insta stable. Maybe doc tests? Some documentation wouldn't hurt either. E,g,, here,

ChrisDenton · 2023-05-03T21:16:47Z

Thanks!

@bors r+

bors · 2023-05-03T21:16:49Z

📌 Commit de10516 has been approved by ChrisDenton

It is now in the queue for this repository.

…risDenton Implement tuple<->array convertions via `From` This PR adds the following impls that convert between homogeneous tuples and arrays of the corresponding lengths: ```rust impl<T> From<[T; 1]> for (T,) { ... } impl<T> From<[T; 2]> for (T, T) { ... } /* ... */ impl<T> From<[T; 12]> for (T, T, T, T, T, T, T, T, T, T, T, T) { ... } impl<T> From<(T,)> for [T; 1] { ... } impl<T> From<(T, T)> for [T; 2] { ... } /* ... */ impl<T> From<(T, T, T, T, T, T, T, T, T, T, T, T)> for [T; 12] { ... } ``` IMO these are quite uncontroversial but note that they are, just like any other trait impls, insta-stable.

…earth Rollup of 10 pull requests Successful merges: - rust-lang#97594 (Implement tuple<->array convertions via `From`) - rust-lang#105452 (Add cross-language LLVM CFI support to the Rust compiler) - rust-lang#105695 (Replace generic thread parker with explicit no-op parker) - rust-lang#110371 (rustdoc: restructure type search engine to pick-and-use IDs) - rust-lang#110928 (tests: Add tests for LoongArch64) - rust-lang#110970 (tidy: remove ENTRY_LIMIT maximum checking and set it to 900) - rust-lang#111104 (Update ICU4X to 1.2) - rust-lang#111127 (Constify slice flatten method) - rust-lang#111146 (rustc_middle: Fix `opt_item_ident` for non-local def ids) - rust-lang#111154 (Use builtin FFX isolation for Fuchsia test runner) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

library/core/src/tuple.rs

Fixup "since" dates for `array_tuple_conv` feature Fixes a mistake from rust-lang#97594

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label May 31, 2022

rust-highfive assigned Mark-Simulacrum May 31, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 31, 2022

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rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label May 31, 2022

rust-highfive unassigned Mark-Simulacrum May 31, 2022

rustbot removed the T-libs Relevant to the library team, which will review and decide on the PR/issue. label May 31, 2022

WaffleLapkin marked this pull request as draft May 31, 2022 19:44

rustbot 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-review Status: Awaiting review from the assignee but also interested parties. labels May 31, 2022

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m-ou-se added the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Jun 1, 2022

WaffleLapkin marked this pull request as ready for review June 2, 2022 13:16

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 2, 2022

WaffleLapkin force-pushed the array_tuple_conv branch from 46a44a8 to 156c906 Compare August 19, 2022 13:11

scottmcm added the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Feb 12, 2023

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Mention array<->tuple convs in docs

de10516

rust-cloud-vms bot force-pushed the array_tuple_conv branch from 8ac5f61 to de10516 Compare May 3, 2023 20:35

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 May 3, 2023

ChrisDenton added relnotes Marks issues that should be documented in the release notes of the next release. and removed needs-fcp This change is insta-stable, so needs a completed FCP to proceed. labels May 3, 2023

Manishearth mentioned this pull request May 3, 2023

Rollup of 8 pull requests #111162

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Manishearth mentioned this pull request May 3, 2023

Rollup of 10 pull requests #111163

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This was referenced May 3, 2023

Rollup of 11 pull requests #111165

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Rollup of 10 pull requests #111169

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bors merged commit 84d8159 into rust-lang:master May 4, 2023

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WaffleLapkin deleted the array_tuple_conv branch May 4, 2023 18:13

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Fixup "since" dates for array_tuple_conv feature #111213

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matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request May 4, 2023

Rollup merge of rust-lang#111213 - WaffleLapkin:fixup_dates, r=scottmcm

ab693f7

Fixup "since" dates for `array_tuple_conv` feature Fixes a mistake from rust-lang#97594

JohnTitor added a commit to JohnTitor/rust that referenced this pull request May 5, 2023

Rollup merge of rust-lang#111213 - WaffleLapkin:fixup_dates, r=scottmcm

17a6c08

Fixup "since" dates for `array_tuple_conv` feature Fixes a mistake from rust-lang#97594

leonardo-m mentioned this pull request May 5, 2023

Simpler tuple <=> array conversions rust-lang/rust-clippy#10748

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lowr mentioned this pull request May 22, 2023

Autocomplete/hover broken in IndexMap with tuple key rust-lang/rust-analyzer#14871

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cuviper mentioned this pull request Jul 7, 2023

the trait bound &[u8]: std::convert::From<&[_; 0]> is not satisfied #113238

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Implement tuple<->array convertions via `From` #97594

Implement tuple<->array convertions via `From` #97594

WaffleLapkin commented May 31, 2022 •

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Implement tuple<->array convertions via From #97594

Implement tuple<->array convertions via From #97594

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Implement tuple<->array convertions via `From` #97594

Implement tuple<->array convertions via `From` #97594

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