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#[derive(Clone)] should explicitly override clone_from #13281

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huonw opened this issue Apr 3, 2014 · 3 comments
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#[derive(Clone)] should explicitly override clone_from #13281

huonw opened this issue Apr 3, 2014 · 3 comments
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C-enhancement Category: An issue proposing an enhancement or a PR with one. I-slow Issue: Problems and improvements with respect to performance of generated code.

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@huonw
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huonw commented Apr 3, 2014

This would mean derived clone implementations can reuse the resources of interior types (especially important with types containing things like Vec) when cloning into an already-created instance.

Currently doing this is difficult with how #[deriving] works internally (needs a mutable borrow of the contents of self, and needs to avoid borrowing self for enum variants that mismatch or else the requisite *self = other.clone() implementation won't work).
Diggsey added a commit to Diggsey/rust that referenced this issue Aug 22, 2015
@Diggsey
Implement clone_from via #[derive(Clone)], fixes rust-lang#13281
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@Diggsey Diggsey mentioned this issue Aug 22, 2015
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@steveklabnik
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Triage: no change that i'm aware of.

@mcarton mcarton mentioned this issue Oct 8, 2016
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@tbu-
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tbu- commented Mar 21, 2017

Seems like we could close this issue (see reasoning in #27939).

@Mark-Simulacrum Mark-Simulacrum added the I-slow Issue: Problems and improvements with respect to performance of generated code. label Jun 13, 2017
@Mark-Simulacrum Mark-Simulacrum added C-enhancement Category: An issue proposing an enhancement or a PR with one. and removed I-papercut labels Jul 20, 2017
@dtolnay dtolnay changed the title #[deriving(Clone)] should explicitly override clone_from #[derive(Clone)] should explicitly override clone_from Dec 3, 2017
@dtolnay
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dtolnay commented Dec 3, 2017

The reasoning in #27939 still applies as to why this should not be provided by the built-in derive(Clone). A custom derive for clone_from is provided in the derivative crate

@dtolnay dtolnay closed this as completed Dec 3, 2017
@ChayimFriedman2 ChayimFriedman2 mentioned this issue Jun 22, 2022
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Jarcho pushed a commit to Jarcho/rust that referenced this issue Aug 24, 2024
@bors
Auto merge of rust-lang#13281 - alex-semenyuk:string_slice_fix, r=y21
d0e637d 
 Trigger [`string_slice`] if expression is reference to `&str`

Close rust-lang#12708
changelog: [`string_slice`]: trigger lint if expression is reference to `&str`
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C-enhancement Category: An issue proposing an enhancement or a PR with one. I-slow Issue: Problems and improvements with respect to performance of generated code.
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Implement specialised clone_from via #[derive(Clone)] Diggsey/rust
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@steveklabnik @huonw @dtolnay @Mark-Simulacrum @tbu-