less aggressive needless_borrows_for_generic_args#12706
Merged
bors merged 1 commit intorust-lang:masterfrom May 15, 2024
Merged
less aggressive needless_borrows_for_generic_args#12706bors merged 1 commit intorust-lang:masterfrom
bors merged 1 commit intorust-lang:masterfrom
Conversation
Collaborator
|
Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dswij (or someone else) some time within the next two weeks. Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (
|
rustbot
added
the
S-waiting-on-review
pacak
force-pushed
the
less-aggressive-needless-borrows
branch
2 times, most recently
from
9a5a614 to
8e67bf1
Compare
dswij
reviewed
May 5, 2024
Current implementation looks for significant drops, that can change the behavior, but that's not enough - value might not have a Drop itself but one of its children might have it. A good example is passing a reference to `PathBuf` to `std::fs::File::open`. There's no benefits to pass `PathBuf` by value, but since clippy can't see `Drop` on `Vec` several layers down it complains forcing pass by value and making it impossible to use the same name later. New implementation only looks at copy values or values created inplace so existing variable will never be moved but things that take a string reference created and value is created inplace `&"".to_owned()` will make it to suggest to use `"".to_owned()` still. Fixes rust-lang#12454
pacak
force-pushed
the
less-aggressive-needless-borrows
branch
from
8e67bf1 to
79a14de
Compare
dswij
approved these changes
May 15, 2024
Member
|
Thank you. @bors r+ |
Contributor
Contributor
Contributor
|
☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test |
meithecatte
added a commit
to meithecatte/rust-clippy
that referenced
this pull request
Jun 5, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
meithecatte
added a commit
to meithecatte/rust-clippy
that referenced
this pull request
Jun 5, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
meithecatte
added a commit
to meithecatte/rust-clippy
that referenced
this pull request
Jun 6, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
meithecatte
added a commit
to meithecatte/rust-clippy
that referenced
this pull request
Jun 6, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
xFrednet
pushed a commit
to xFrednet/rust-clippy
that referenced
this pull request
Jul 23, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
xFrednet
pushed a commit
to xFrednet/rust-clippy
that referenced
this pull request
Jul 23, 2024
This commit fixes a bug introduced in rust-lang#12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, rust-lang#12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus rust-lang#12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes rust-lang#12856
bors
added a commit
that referenced
this pull request
Jul 25, 2024
needless_borrows_for_generic_args: Fix for &mut This commit fixes a bug introduced in #12706, where the behavior of the lint has been changed, to avoid suggestions that introduce a move. The motivation in the commit message is quite poor (if the detection for significant drops is not sufficient because it's not transitive, the proper fix would be to make it transitive). However, #12454, the linked issue, provides a good reason for the change — if the value being borrowed is bound to a variable, then moving it will only introduce friction into future refactorings. Thus #12706 changes the logic so that the lint triggers if the value being borrowed is Copy, or is the result of a function call, simplifying the logic to the point where analysing "is this the only use of this value" isn't necessary. However, said PR also introduces an undocumented carveout, where referents that themselves are mutable references are treated as Copy, to catch some cases that we do want to lint against. However, that is not sound — it's possible to consume a mutable reference by moving it. To avoid emitting false suggestions, this PR reintroduces the referent_used_exactly_once logic and runs that check for referents that are themselves mutable references. Thinking about the code shape of &mut x, where x: &mut T, raises the point that while removing the &mut outright won't work, the extra indirection is still undesirable, and perhaps instead we should suggest reborrowing: &mut *x. That, however, is left as possible future work. Fixes #12856 changelog: none
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Current implementation looks for significant drops, that can change the behavior, but that's not enough - value might not have a
Dropitself but one of its children might have it.A good example is passing a reference to
PathBuftostd::fs::File::open. There's no benefits to passPathBufby value, but sinceclippycan't seeDroponVecseveral layers down it complains forcing pass by value and making it impossible to use the same name later.New implementation only looks at copy values or values created in place so existing variable will never be moved but things that take a string reference created and value is created inplace
&"".to_owned()will make it to suggest to use"".to_owned()still.Fixes #12454
changelog: [
needless_borrows_for_generic_args]: avoid moving variables