Uplift `clippy::{drop,forget}_{ref,copy}` lints #109732

Urgau · 2023-03-29T17:09:21Z

This PR aims at uplifting the clippy::drop_ref, clippy::drop_copy, clippy::forget_ref and clippy::forget_copy lints.

Those lints are/were declared in the correctness category of clippy because they lint on useless and most probably is not what the developer wanted.

`drop_ref` and `forget_ref`

ℹ️ The lints have been renamed to dropping_copy_types and forgetting_copy_types in #111756

The drop_ref and forget_ref lint checks for calls to std::mem::drop or std::mem::forget with a reference instead of an owned value.

Example

let mut lock_guard = mutex.lock();
std::mem::drop(&lock_guard) // Should have been drop(lock_guard), mutex
// still locked
operation_that_requires_mutex_to_be_unlocked();

Explanation

Calling drop or forget on a reference will only drop the reference itself, which is a no-op. It will not call the drop or forget method on the underlying referenced value, which is likely what was intended.

`drop_copy` and `forget_copy`

ℹ️ The lints have been renamed to dropping_references and forgetting_references in #111756

The drop_copy and forget_copy lint checks for calls to std::mem::forget or std::mem::drop with a value that derives the Copy trait.

Example

let x: i32 = 42; // i32 implements Copy
std::mem::forget(x) // A copy of x is passed to the function, leaving the
                    // original unaffected

Explanation

Calling std::mem::forget does nothing for types that implement Copy since the value will be copied and moved into the function on invocation.

Followed the instructions for uplift a clippy describe here: #99696 (review)

cc @m-ou-se (as T-libs-api leader because the uplifting was discussed in a recent meeting)

rustbot · 2023-03-29T17:09:28Z

r? @TaKO8Ki

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rustbot · 2023-03-29T17:09:31Z

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

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Noratrieb

some cases in rustc, fun (can't wait for clippy to finally work on rustc^^)

compiler/rustc_infer/src/infer/nll_relate/mod.rs

compiler/rustc_middle/src/mir/visit.rs

src/tools/clippy/clippy_lints/src/drop_forget_ref.rs

src/tools/clippy/tests/ui/deprecated.rs

Urgau · 2023-04-04T17:21:44Z

Nominating for T-lang approval, as it seems to be the norm.

@rustbot label: +I-lang-nominated

nikomatsakis · 2023-04-04T18:26:14Z

@rustbot labels -I-lang-nominated

@rfcbot fcp merge

We discussed this our @rust-lang/lang meeting and we agree that, when this occurs, it is very likely to be a bug or misunderstanding, which is our usual criteria for uplift.

GuillaumeGomez · 2023-05-11T18:29:35Z

@bors r=davidtwco

bors · 2023-05-11T18:29:36Z

📌 Commit f5aede9 has been approved by davidtwco

It is now in the queue for this repository.

bors · 2023-05-11T18:29:37Z

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

bors · 2023-05-12T12:04:35Z

⌛ Testing commit f5aede9 with merge 077fc26...

bors · 2023-05-12T14:50:25Z

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 077fc26 to master...

bors · 2023-05-12T14:50:26Z

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 077fc26 to master...

rust-timer · 2023-05-12T16:05:21Z

Finished benchmarking commit (077fc26): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.4%, 0.8%]	5
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.4%	[-1.9%, -1.0%]	4
All ❌✅ (primary)	0.5%	[0.4%, 0.8%]	5

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.2%	[0.7%, 1.6%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-2.9%, -2.4%]	2
All ❌✅ (primary)	1.2%	[0.7%, 1.6%]	2

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 659.774s -> 659.596s (-0.03%)

Remove useless drop of copy type ### What does this PR try to resolve? This PR aims to remove useless drop of copy type to clear warnings that reported after rust-lang/rust#109732 ``` warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing --> src/cargo/core/compiler/job_queue/mod.rs:1048:21 | 1048 | drop(write!( | ______________________^____- | | _____________________| | || 1049 | || message, 1050 | || " (run `{command} --{args}` to apply {suggestions})" 1051 | || )) | ||_____________________-^ | |______________________| | argument has type `Result<(), std::fmt::Error>` | = note: use `let _ = ...` to ignore the expression or result = note: `#[warn(drop_copy)]` on by default ``` ### How should we test and review this PR? ```bash cargo build && cargo test # without any warnings ``` ### Additional information None

…lints, r=fee1-dead Rename `{drop,forget}_{copy,ref}` lints to more consistent naming This PR renames previous uplifted lints in rust-lang#109732 to more consistent naming. I followed the renaming done [here](rust-lang#53224) and also advocated in this [clippy issue](rust-lang/rust-clippy#2845): - `drop_copy` to `dropping_copy_types` - `forget_copy` to `forgetting_copy_types` - `drop_ref` to `dropping_references` - `forget_ref` to `forgetting_references`

…fee1-dead Rename `{drop,forget}_{copy,ref}` lints to more consistent naming This PR renames previous uplifted lints in rust-lang/rust#109732 to more consistent naming. I followed the renaming done [here](rust-lang/rust#53224) and also advocated in this [clippy issue](rust-lang/rust-clippy#2845): - `drop_copy` to `dropping_copy_types` - `forget_copy` to `forgetting_copy_types` - `drop_ref` to `dropping_references` - `forget_ref` to `forgetting_references`

Followed up of d36e390d8176babedcf326581959958d447170cd See rust-lang/rust#109732 (comment) for more details. Co-authored-by: Jethro Beekman <jethro@fortanix.com>

…fee1-dead Rename `{drop,forget}_{copy,ref}` lints to more consistent naming This PR renames previous uplifted lints in rust-lang/rust#109732 to more consistent naming. I followed the renaming done [here](rust-lang/rust#53224) and also advocated in this [clippy issue](rust-lang/rust-clippy#2845): - `drop_copy` to `dropping_copy_types` - `forget_copy` to `forgetting_copy_types` - `drop_ref` to `dropping_references` - `forget_ref` to `forgetting_references`

rustbot assigned TaKO8Ki Mar 29, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Mar 29, 2023

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Urgau force-pushed the uplift_drop_forget_ref_lints branch from 026278d to 5c6fed5 Compare March 29, 2023 17:38

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Noratrieb reviewed Mar 29, 2023

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Alexendoo reviewed Mar 29, 2023

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Urgau force-pushed the uplift_drop_forget_ref_lints branch from c3edde2 to fad236f Compare April 2, 2023 13:38

rustbot added the I-lang-nominated Nominated for discussion during a lang team meeting. label Apr 4, 2023

rustbot removed the I-lang-nominated Nominated for discussion during a lang team meeting. label Apr 4, 2023

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 11, 2023

bors added merged-by-bors This PR was explicitly merged by bors. labels May 12, 2023

bors merged commit 077fc26 into rust-lang:master May 12, 2023

rustbot added this to the 1.71.0 milestone May 12, 2023

This was referenced May 12, 2023

Remove unstable Poll::ready #107060

Merged

Enable -Zdrop-tracking-mir by default #107421

Merged

do not allow inference in predicate_must_hold (alternative approach) #110100

Merged

Combine three generalizer implementations #111221

Merged

rustbot added the perf-regression Performance regression. label May 12, 2023

heiher mentioned this pull request May 13, 2023

Remove useless drop of copy type rust-lang/cargo#12136

Merged

Urgau deleted the uplift_drop_forget_ref_lints branch May 13, 2023 09:26

sffc mentioned this pull request May 15, 2023

ZeroVec Yoke impl started failing "forget-copy" on Nightly unicode-org/icu4x#3436

Closed

This was referenced May 16, 2023

Uplift clippy::undropped_manually_drops lint #111530

Merged

Rename {drop,forget}_{copy,ref} lints to more consistent naming #111756

Merged

samkearney mentioned this pull request Jun 3, 2023

Add a config default for QNX 7.0 JohnTitor/ctest2#52

Merged

thomcc pushed a commit to tcdi/postgrestd that referenced this pull request Jul 18, 2023

Improve code around SGX waitqueue

a15064d

Followed up of d36e390d8176babedcf326581959958d447170cd See rust-lang/rust#109732 (comment) for more details. Co-authored-by: Jethro Beekman <jethro@fortanix.com>

Urgau mentioned this pull request Jun 11, 2024

Enhance suggestions of dropping_* lints #126275

Closed

Uplift clippy::{drop,forget}_{ref,copy} lints #109732

Uplift clippy::{drop,forget}_{ref,copy} lints #109732

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Urgau commented Mar 29, 2023 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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drop_ref and forget_ref

Example

Explanation

drop_copy and forget_copy

Example

Explanation

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Urgau commented Apr 4, 2023

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rust-timer commented May 12, 2023

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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Uplift `clippy::{drop,forget}_{ref,copy}` lints #109732

Uplift `clippy::{drop,forget}_{ref,copy}` lints #109732

Urgau commented Mar 29, 2023 •

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`drop_ref` and `forget_ref`

`drop_copy` and `forget_copy`