Warn on unused results for operation methods on nums #59839
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Kimundi (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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You can prepend a |
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I do also have a It might be worth looking at how we want to decide what numeric operations should have a |
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ping from triage @KodrAus any updates on this? can you get someone from the team to review it? |
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r? @SimonSapin |
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Sorry @SimonSapin I don't mean to be assigning you all the PRs today :) r? @sfackler |
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@bors r+ rollup |
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📌 Commit 23154db has been approved by |
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kennytm
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Warn on unused results for operation methods on nums From a suggestion by @llogiq Adds a `#[must_use]` attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutating `self`, which is the source of a rather embarrassing bug I had in a codebase of mine recently... As an example: ```rust struct Int { value: i64, } impl Int { fn add(&mut self, other: i64) { self.value.wrapping_add(other); } } ``` Will produce a warning like: ``` warning: unused return value of `core::num::<impl i64>::wrapping_add` that must be used --> src/main.rs:7:7 | 7 | self.value.wrapping_add(other); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_must_use)] on by default = note: this returns the result of the operation, without modifying the original ``` If this is something we're on board with, we could do something similar for `f32` and `f64` too. There are probably other methods on integers that make sense.
Centril
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Apr 23, 2019
Warn on unused results for operation methods on nums From a suggestion by @llogiq Adds a `#[must_use]` attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutating `self`, which is the source of a rather embarrassing bug I had in a codebase of mine recently... As an example: ```rust struct Int { value: i64, } impl Int { fn add(&mut self, other: i64) { self.value.wrapping_add(other); } } ``` Will produce a warning like: ``` warning: unused return value of `core::num::<impl i64>::wrapping_add` that must be used --> src/main.rs:7:7 | 7 | self.value.wrapping_add(other); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_must_use)] on by default = note: this returns the result of the operation, without modifying the original ``` If this is something we're on board with, we could do something similar for `f32` and `f64` too. There are probably other methods on integers that make sense.
Centril
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Apr 23, 2019
Warn on unused results for operation methods on nums From a suggestion by @llogiq Adds a `#[must_use]` attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutating `self`, which is the source of a rather embarrassing bug I had in a codebase of mine recently... As an example: ```rust struct Int { value: i64, } impl Int { fn add(&mut self, other: i64) { self.value.wrapping_add(other); } } ``` Will produce a warning like: ``` warning: unused return value of `core::num::<impl i64>::wrapping_add` that must be used --> src/main.rs:7:7 | 7 | self.value.wrapping_add(other); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_must_use)] on by default = note: this returns the result of the operation, without modifying the original ``` If this is something we're on board with, we could do something similar for `f32` and `f64` too. There are probably other methods on integers that make sense.
Centril
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to Centril/rust
that referenced
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Apr 23, 2019
Warn on unused results for operation methods on nums From a suggestion by @llogiq Adds a `#[must_use]` attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutating `self`, which is the source of a rather embarrassing bug I had in a codebase of mine recently... As an example: ```rust struct Int { value: i64, } impl Int { fn add(&mut self, other: i64) { self.value.wrapping_add(other); } } ``` Will produce a warning like: ``` warning: unused return value of `core::num::<impl i64>::wrapping_add` that must be used --> src/main.rs:7:7 | 7 | self.value.wrapping_add(other); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_must_use)] on by default = note: this returns the result of the operation, without modifying the original ``` If this is something we're on board with, we could do something similar for `f32` and `f64` too. There are probably other methods on integers that make sense.
Centril
added a commit
to Centril/rust
that referenced
this pull request
Apr 23, 2019
Warn on unused results for operation methods on nums From a suggestion by @llogiq Adds a `#[must_use]` attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutating `self`, which is the source of a rather embarrassing bug I had in a codebase of mine recently... As an example: ```rust struct Int { value: i64, } impl Int { fn add(&mut self, other: i64) { self.value.wrapping_add(other); } } ``` Will produce a warning like: ``` warning: unused return value of `core::num::<impl i64>::wrapping_add` that must be used --> src/main.rs:7:7 | 7 | self.value.wrapping_add(other); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_must_use)] on by default = note: this returns the result of the operation, without modifying the original ``` If this is something we're on board with, we could do something similar for `f32` and `f64` too. There are probably other methods on integers that make sense.
bors
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Apr 23, 2019
Rollup of 6 pull requests Successful merges: - #59823 ([wg-async-await] Drop `async fn` arguments in async block ) - #59839 (Warn on unused results for operation methods on nums) - #60146 (Update fonts used by rustdoc) - #60169 (Warn when ignore-tidy-linelength is present, but no lines are too long) - #60177 (Promote rust comments to rustdoc) - #60191 (Add f16c target_feature) Failed merges: r? @ghost
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From a suggestion by @llogiq
Adds a
#[must_use]attribute to operation methods on integers that take self by value as the first operand and another value as the second. It makes it clear that these methods return the result of the operation instead of mutatingself, which is the source of a rather embarrassing bug I had in a codebase of mine recently...As an example:
Will produce a warning like:
If this is something we're on board with, we could do something similar for
f32andf64too. There are probably other methods on integers that make sense.