Removed DeepClone #12706
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Removed DeepClone #12706
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Can you reference the issue number in the commit message as well? It's helpful with rollups (not that we need one right now), and also with later historical digging. |
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I don't agree with removing this, as stated on the issue. |
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Indeed, it seems useful. Assume you have a simulation whose state is a bunch of interlinked objects, implemented with At most, I think it could be moved to a loadable syntax extension, since indeed there should not be any use cases in core libraries. That might be an interesting idea to explore as it would allow to add more specialized functionality that would meet resistance in the core libraries, such as support for deep cloning cyclic graphs using an HashMap. |
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A big part of me agrees with @brson that it shouldn't be in stdlib because there is no consumer for it. I also see everyone's point that it should have a use case somewhere. Should it be placed in some lib outside of libstd? It seems weird to have libdeepclone though! |
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Libextra?
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It needs to be in libstd if it's going to exist because it's implemented by types in libstd. |
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You are right of course. I will leave the PR here for the time being while we try to reach a consensus. |
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We have reached a consensus that this trait does not belong in libstd. If this trait should exist it belongs in a separate library. @pongad, with an expansion of the commit message, I will r+ |
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It can't be implemented in another library, because there's no way to implement it on libstd types due to their fields being private. There would also be no way to derive the implementations. |
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That is incorrect. impl<T: DeepClone> DeepClone for Rc<T> {
fn deep_clone(&self) -> Rc<T> {
Rc::new(self.borrow().deep_clone())
}
} |
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(Friendly reminder that the commit message needs updating still. :) ) |
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Updated. |
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@pongad The patch needs rebase. |
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Rebased. Unfortunately I have an errand to run and cannot make check it just yet. If Travis or bors fails, I'll fix when I get back this evening. |
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@brson I took a glance at Bors queue just now and apparently this PR is still in discussing state. Did bors not see the r+? |
bors
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Mar 9, 2014
chris-morgan
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Mar 10, 2014
Rust update: `DeepClone` was removed (rust-lang/rust#12706)
bors
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Jul 25, 2022
…r=DorianListens fix: Extract Function misses locals used in closures This change fixes rust-lang#12705. In `FunctionBody::analyze`, we need to search any `ClosureExpr`s we encounter for any `NameRef`s, to ensure they aren't missed.
flip1995
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May 17, 2024
…s, r=dswij less aggressive needless_borrows_for_generic_args 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 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 rust-lang/rust-clippy#12454 changelog: [`needless_borrows_for_generic_args`]: avoid moving variables
dingxiangfei2009
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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
dingxiangfei2009
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Jul 28, 2024
… r=xFrednet needless_borrows_for_generic_args: Fix for &mut 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 changelog: none
Jarcho
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Aug 26, 2024
… r=xFrednet needless_borrows_for_generic_args: Fix for &mut 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 changelog: none
Jarcho
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Aug 26, 2024
… r=xFrednet needless_borrows_for_generic_args: Fix for &mut 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 changelog: none
MabezDev
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Sep 3, 2024
… r=xFrednet needless_borrows_for_generic_args: Fix for &mut 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 changelog: none
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Fixes #12698