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Lint against RefCell::borrow/borrow_mut on &mut RefCell #9044
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A-lint
Area: New lints
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Dylan-DPC
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Sep 19, 2022
Tone down explanation on RefCell::get_mut The language around `RefCell::get_mut` is remarkably sketchy and especially to the novice seems to quite strongly discourage using the method ("be cautious", "Also, please be aware", "special circumstances", "usually not what you want"). It was added six years ago in rust-lang#40634 due to confusion about when to use `get_mut` and `borrow_mut`. While its signature limits the use-cases for `get_mut`, there is no chance for a safety footgun, and readers can be made aware of `borrow_mut` more softly. I've also just sent a [PR](rust-lang/rust-clippy#9044) to lint situations where `get_mut` could be used to improve ergonomics and performance. So this PR tones down the language around `get_mut` and also brings it more in line with [`std::sync::Mutex::get_mut()`](https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.get_mut).
matthiaskrgr
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Sep 19, 2022
Tone down explanation on RefCell::get_mut The language around `RefCell::get_mut` is remarkably sketchy and especially to the novice seems to quite strongly discourage using the method ("be cautious", "Also, please be aware", "special circumstances", "usually not what you want"). It was added six years ago in rust-lang#40634 due to confusion about when to use `get_mut` and `borrow_mut`. While its signature limits the use-cases for `get_mut`, there is no chance for a safety footgun, and readers can be made aware of `borrow_mut` more softly. I've also just sent a [PR](rust-lang/rust-clippy#9044) to lint situations where `get_mut` could be used to improve ergonomics and performance. So this PR tones down the language around `get_mut` and also brings it more in line with [`std::sync::Mutex::get_mut()`](https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.get_mut).
thomcc
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Feb 10, 2023
Tone down explanation on RefCell::get_mut The language around `RefCell::get_mut` is remarkably sketchy and especially to the novice seems to quite strongly discourage using the method ("be cautious", "Also, please be aware", "special circumstances", "usually not what you want"). It was added six years ago in #40634 due to confusion about when to use `get_mut` and `borrow_mut`. While its signature limits the use-cases for `get_mut`, there is no chance for a safety footgun, and readers can be made aware of `borrow_mut` more softly. I've also just sent a [PR](rust-lang/rust-clippy#9044) to lint situations where `get_mut` could be used to improve ergonomics and performance. So this PR tones down the language around `get_mut` and also brings it more in line with [`std::sync::Mutex::get_mut()`](https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.get_mut).
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What it does
On this code:
the lint would suggest to use
get_mut()
rather thanborrow_mut()
. (Same forborrow()
, of course.)Lint Name
unnecessary_runtime_borrow
Category
perf
Advantage
RefCell
Drawbacks
None that I know if
Example
See above.
Mutex
andRwLock
also haveget_mut
functions, so the same kind of lint could be added for them.The text was updated successfully, but these errors were encountered: