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Markdown
105 lines
4.6 KiB
Markdown
# Clippy's Lints
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Clippy offers a bunch of additional lints, to help its users write more correct
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and idiomatic Rust code. A full list of all lints, that can be filtered by
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category, lint level or keywords, can be found in the [Clippy lint
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documentation].
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This chapter will give an overview of the different lint categories, which kind
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of lints they offer and recommended actions when you should see a lint out of
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that category. For examples, see the [Clippy lint documentation] and filter by
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category.
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The different lint groups were defined in the [Clippy 1.0 RFC].
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## Correctness
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The `clippy::correctness` group is the only lint group in Clippy which lints are
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deny-by-default and abort the compilation when triggered. This is for good
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reason: If you see a `correctness` lint, it means that your code is outright
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wrong or useless, and you should try to fix it.
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Lints in this category are carefully picked and should be free of false
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positives. So just `#[allow]`ing those lints is not recommended.
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## Suspicious
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The `clippy::suspicious` group is similar to the correctness lints in that it
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contains lints that trigger on code that is really _sus_ and should be fixed. As
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opposed to correctness lints, it might be possible that the linted code is
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intentionally written like it is.
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It is still recommended to fix code that is linted by lints out of this group
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instead of `#[allow]`ing the lint. In case you intentionally have written code
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that offends the lint you should specifically and locally `#[allow]` the lint
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and add give a reason why the code is correct as written.
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## Complexity
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The `clippy::complexity` group offers lints that give you suggestions on how to
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simplify your code. It mostly focuses on code that can be written in a shorter
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and more readable way, while preserving the semantics.
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If you should see a complexity lint, it usually means that you can remove or
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replace some code, and it is recommended to do so. However, if you need the more
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complex code for some expressiveness reason, it is recommended to allow
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complexity lints on a case-by-case basis.
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## Perf
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The `clippy::perf` group gives you suggestions on how you can increase the
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performance of your code. Those lints are mostly about code that the compiler
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can't trivially optimize, but has to be written in a slightly different way to
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make the optimizer job easier.
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Perf lints are usually easy to apply, and it is recommended to do so.
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## Style
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The `clippy::style` group is mostly about writing idiomatic code. Because style
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is subjective, this lint group is the most opinionated warn-by-default group in
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Clippy.
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If you see a style lint, applying the suggestion usually makes your code more
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readable and idiomatic. But because we know that this is opinionated, feel free
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to sprinkle `#[allow]`s for style lints in your code or `#![allow]` a style lint
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on your whole crate if you disagree with the suggested style completely.
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## Pedantic
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The `clippy::pedantic` group makes Clippy even more _pedantic_. You can enable
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the whole group with `#![warn(clippy::pedantic)]` in the `lib.rs`/`main.rs` of
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your crate. This lint group is for Clippy power users that want an in depth
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check of their code.
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> _Note:_ Instead of enabling the whole group (like Clippy itself does), you may
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> want to cherry-pick lints out of the pedantic group.
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If you enable this group, expect to also use `#[allow]` attributes generously
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throughout your code. Lints in this group are designed to be pedantic and false
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positives sometimes are intentional in order to prevent false negatives.
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## Restriction
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The `clippy::restriction` group contains lints that will _restrict_ you from
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using certain parts of the Rust language. It is **not** recommended to enable
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the whole group, but rather cherry-pick lints that are useful for your code base
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and your use case.
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> _Note:_ Clippy will produce a warning if it finds a
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> `#![warn(clippy::restriction)]` attribute in your code!
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Lints from this group will restrict you in some way. If you enable a restriction
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lint for your crate it is recommended to also fix code that this lint triggers
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on. However, those lints are really strict by design, and you might want to
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`#[allow]` them in some special cases, with a comment justifying that.
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## Cargo
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The `clippy::cargo` group gives you suggestions on how to improve your
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`Cargo.toml` file. This might be especially interesting if you want to publish
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your crate and are not sure if you have all useful information in your
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`Cargo.toml`.
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[Clippy lint documentation]: https://rust-lang.github.io/rust-clippy/
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[Clippy 1.0 RFC]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#lint-audit-and-categories
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