Stabilize some Result methods as const #76136

CDirkx · 2020-08-31T00:53:37Z

Stabilize the following methods of Result as const:

is_ok
is_err
as_ref

A test is also included, analogous to the test for const_option.

These methods are currently const under the unstable feature const_result (tracking issue: #67520).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: PR#75463 and PR#76135.

Note: these methods are the only methods currently under the const_result feature, thus this PR results in the removal of the feature.

Related: #76225

Stabilize the following methods of `Result` as const: - `is_ok` - `is_err` - `as_ref` Possible because of stabilization of rust-lang#49146 (Allow if and match in constants).

rust-highfive · 2020-08-31T00:53:41Z

r? @cramertj

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

CDirkx · 2020-08-31T00:57:01Z

r? @ecstatic-morse

ecstatic-morse · 2020-08-31T16:16:00Z

r? @KodrAus (Needs FCP)

CDirkx · 2020-09-01T23:43:16Z

Created an issue for similar stabilizations: #76225

Part of rust-lang#76268

KodrAus · 2020-09-04T05:38:55Z

For reference, there's also an equivalent push to constify some Option methods at #76135

@rfcbot fcp merge

KodrAus · 2020-09-04T07:01:37Z

@rfcbot fcp merge

rfcbot · 2020-09-04T07:01:38Z

Team member @KodrAus has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

rfcbot · 2020-09-07T03:34:54Z

🔔 This is now entering its final comment period, as per the review above. 🔔

josephlr · 2020-09-12T09:32:01Z

~~There are some other methods we should also make const (either in this PR or a followup). They all have trivial match implementations and doesn't use any trait bounds:~~

Result::ok()
Result::err()
Result::iter()
Result::and()
Result::or()
Result::unwrap_or()
Result::transpose()

~~Result::flatten() also has a trivial impl, but that's unstable anyway (see #70142 (comment))~~

EDIT: Nevermind, these all require const fn Drop
EDIT2: Actually, we can implement transpose without dropping anything
EDIT3: Nevermind, transpose requires const_precise_live_drops, which isn't stable.

bors · 2020-09-17T06:42:25Z

⌛ Testing commit 787b270 with merge a51855f645eb6b86d1c6eb5656ae3394c9949a05...

bors · 2020-09-17T07:25:06Z

💔 Test failed - checks-actions

ecstatic-morse · 2020-09-17T16:05:36Z

@CDirkx Test failures are legit. Clippy has a lint that suggests is_err() instead of if let Err(_), but it's disabled in const fn. With this PR, that exception is no longer necessary and the test output can be updated.

Update the test `redundant_pattern_matching`: check if `is_ok` and `is_err` are suggested within const contexts. Also removes the `redundant_pattern_matching_const_result` test, as it is no longer needed.

CDirkx · 2020-09-20T01:35:46Z

I updated the testcases, when this get's merged I'll update the testcases using Option as well and sync these changes to the Clippy repo.

RalfJung · 2020-09-20T07:24:48Z

How can it be enough to update the testcases, doesn't the clippy code emitting these lints also need to be updated?

ebroto · 2020-09-20T07:50:39Z

Clippy is checking if the suggested methods are const fn in const contexts, so it works without changing the logic because they are after this change.

But once the Option methods are stabilized as const fn the function can_suggest and calls to it should be removed as there would be no special cases left.

CDirkx · 2020-09-20T08:20:00Z

That's what I thought as well (#76135 (comment)), but the implementation of can_suggest was not specific to is_err etc., so at first I thought it could be used in the future if Clippy were to ever suggest other unstable const methods. However then it should probably be a more general pass and not a specific function that lives in matches.rs, so I'm indeed removing it.

I removed the can_suggest check for is_ok and is_err, but for now can_suggest is still used to not suggest the unstable const is_some and is_none from #76135, I will remove it entirely in that PR.

`is_ok` and `is_err` are stabilized as const and can thus always be suggested.

src/tools/clippy/clippy_lints/src/matches.rs

Co-authored-by: Ralf Jung <post@ralfj.de>

RalfJung · 2020-09-20T10:45:45Z

@bors r=dtolnay

bors · 2020-09-20T10:45:46Z

📌 Commit bf70e21 has been approved by dtolnay

bors · 2020-09-20T13:07:16Z

⌛ Testing commit bf70e21 with merge b873fa6...

bors · 2020-09-20T15:12:33Z

☀️ Test successful - checks-actions, checks-azure
Approved by: dtolnay
Pushing b873fa6 to master...

Stabilize some Result methods as const Stabilize the following methods of Result as const: - `is_ok` - `is_err` - `as_ref` A test is also included, analogous to the test for `const_option`. These methods are currently const under the unstable feature `const_result` (tracking issue: rust-lang#67520). I believe these methods to be eligible for stabilization because of the stabilization of rust-lang#49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](rust-lang#75463) and [PR#76135](rust-lang#76135). Note: these methods are the only methods currently under the `const_result` feature, thus this PR results in the removal of the feature. Related: rust-lang#76225

Stabilize some Result methods as const

518f1cc

Stabilize the following methods of `Result` as const: - `is_ok` - `is_err` - `as_ref` Possible because of stabilization of rust-lang#49146 (Allow if and match in constants).

rust-highfive assigned cramertj Aug 31, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 31, 2020

rust-highfive assigned ecstatic-morse and BurntSushi and unassigned cramertj and ecstatic-morse Aug 31, 2020

rust-highfive assigned KodrAus and unassigned BurntSushi Aug 31, 2020

CDirkx mentioned this pull request Sep 1, 2020

Stabilize enum is_variant methods as const #76225

Closed

6 tasks

jyn514 added A-const-fn Area: const fn foo(..) {..}. Pure functions which can be applied at compile time. needs-fcp This change is insta-stable, so needs a completed FCP to proceed. labels Sep 3, 2020

Move const tests for Result to library\core

787b270

Part of rust-lang#76268

KodrAus mentioned this pull request Sep 4, 2020

Stabilize some Option methods as const #76135

Merged

KodrAus added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Sep 4, 2020

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Sep 7, 2020

jonas-schievink added the relnotes Marks issues that should be documented in the release notes of the next release. label Sep 13, 2020

rfcbot added the finished-final-comment-period The final comment period is finished for this PR / Issue. label Sep 17, 2020

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Sep 17, 2020

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 Sep 17, 2020

spastorino removed the to-announce Announce this issue on triage meeting label Sep 17, 2020

CDirkx mentioned this pull request Sep 19, 2020

redundant_pattern_matching: Option and Result methods stabilized as const rust-lang/rust-clippy#6067

Closed

Update Clippy testcases

ab4fa21

Update the test `redundant_pattern_matching`: check if `is_ok` and `is_err` are suggested within const contexts. Also removes the `redundant_pattern_matching_const_result` test, as it is no longer needed.

Remove can_suggest check for is_ok and is_err.

a59d480

`is_ok` and `is_err` are stabilized as const and can thus always be suggested.

RalfJung reviewed Sep 20, 2020

View reviewed changes

src/tools/clippy/clippy_lints/src/matches.rs Outdated Show resolved Hide resolved

Update src/tools/clippy/clippy_lints/src/matches.rs

bf70e21

Co-authored-by: Ralf Jung <post@ralfj.de>

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 Sep 20, 2020

bors added the merged-by-bors This PR was explicitly merged by bors. label Sep 20, 2020

bors merged commit b873fa6 into rust-lang:master Sep 20, 2020

rustbot added this to the 1.48.0 milestone Sep 20, 2020

CDirkx deleted the const-result branch September 20, 2020 16:03

lukaslueg mentioned this pull request Sep 26, 2020

Tracking issue for const Result #67520

Closed

dtolnay self-assigned this Mar 24, 2024

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Stabilize some Result methods as const #76136

Stabilize some Result methods as const #76136

CDirkx commented Aug 31, 2020 •

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Stabilize some Result methods as const #76136

Stabilize some Result methods as const #76136

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