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 # Clippy

 [![Clippy Test](https://github.com/rust-lang/rust-clippy/workflows/Clippy%20Test/badge.svg?branch=auto&event=push)](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test%22+event%3Apush+branch%3Aauto)
 [![License: MIT OR Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)

 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.

 [There are over 500 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)

 Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html).
 You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category.

 | Category              | Description                                                                         | Default level |
 | --------------------- | ----------------------------------------------------------------------------------- | ------------- |
 | `clippy::all`         | all lints that are on by default (correctness, suspicious, style, complexity, perf) | **warn/deny** |
 | `clippy::correctness` | code that is outright wrong or useless                                              | **deny**      |
 | `clippy::suspicious`  | code that is most likely wrong or useless                                           | **warn**      |
 | `clippy::style`       | code that should be written in a more idiomatic way                                 | **warn**      |
 | `clippy::complexity`  | code that does something simple but in a complex way                                | **warn**      |
 | `clippy::perf`        | code that can be written to run faster                                              | **warn**      |
 | `clippy::pedantic`    | lints which are rather strict or have occasional false positives                    | allow         |
 | `clippy::nursery`     | new lints that are still under development                                          | allow         |
 | `clippy::cargo`       | lints for the cargo manifest                                                        | allow         |

 More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!

 The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are
 for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
 very selectively, if at all.

 Table of contents:

 *   [Usage instructions](#usage)
 *   [Configuration](#configuration)
 *   [Contributing](#contributing)
 *   [License](#license)

 ## Usage

 Below are instructions on how to use Clippy as a cargo subcommand,
 in projects that do not use cargo, or in Travis CI.

 ### As a cargo subcommand (`cargo clippy`)

 One way to use Clippy is by installing Clippy through rustup as a cargo
 subcommand.

 #### Step 1: Install Rustup

 You can install [Rustup](https://rustup.rs/) on supported platforms. This will help
 us install Clippy and its dependencies.

 If you already have Rustup installed, update to ensure you have the latest
 Rustup and compiler:

 ```terminal
 rustup update
 ```

 #### Step 2: Install Clippy

 Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:

 ```terminal
 rustup component add clippy
 ```
 If it says that it can't find the `clippy` component, please run `rustup self update`.

 #### Step 3: Run Clippy

 Now you can run Clippy by invoking the following command:

 ```terminal
 cargo clippy
 ```

 #### Automatically applying Clippy suggestions

 Clippy can automatically apply some lint suggestions, just like the compiler.

 ```terminal
 cargo clippy --fix
 ```

 #### Workspaces

 All the usual workspace options should work with Clippy. For example the following command
 will run Clippy on the `example` crate:

 ```terminal
 cargo clippy -p example
 ```

 As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies.
 If you want to run Clippy **only** on the given crate, use the `--no-deps` option like this:

 ```terminal
 cargo clippy -p example -- --no-deps
 ```

 ### Using `clippy-driver`

 Clippy can also be used in projects that do not use cargo. To do so, run `clippy-driver`
 with the same arguments you use for `rustc`. For example:

 ```terminal
 clippy-driver --edition 2018 -Cpanic=abort foo.rs
 ```

 Note that `clippy-driver` is designed for running Clippy only and should not be used as a general
 replacement for `rustc`. `clippy-driver` may produce artifacts that are not optimized as expected,
 for example.

 ### Travis CI

 You can add Clippy to Travis CI in the same way you use it locally:

 ```yml
 language: rust
 rust:
   - stable
   - beta
 before_script:
   - rustup component add clippy
 script:
   - cargo clippy
   # if you want the build job to fail when encountering warnings, use
   - cargo clippy -- -D warnings
   # in order to also check tests and non-default crate features, use
   - cargo clippy --all-targets --all-features -- -D warnings
   - cargo test
   # etc.
 ```

 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
 line. (You can swap `clippy::all` with the specific lint category you are targeting.)

 ## Configuration

 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
 value` mapping e.g.

 ```toml
 avoid-breaking-exported-api = false
 blacklisted-names = ["toto", "tata", "titi"]
 cognitive-complexity-threshold = 30
 ```

 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
 lints can be configured and the meaning of the variables.

 Note that configuration changes will not apply for code that has already been compiled and cached under `./target/`;
 for example, adding a new string to `doc-valid-idents` may still result in Clippy flagging that string. To be sure that
 any configuration changes are applied, you may want to run `cargo clean` and re-compile your crate from scratch.

 To deactivate the “for further information visit *lint-link*” message you can
 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.

 ### Allowing/denying lints

 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:

 *   the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`).
     Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).

 *   all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
     `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
     lints prone to false positives.

 *   only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)

 *   `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.

 Note: `allow` means to suppress the lint for your code. With `warn` the lint
 will only emit a warning, while with `deny` the lint will emit an error, when
 triggering for your code. An error causes clippy to exit with an error code, so
 is useful in scripts like CI/CD.

 If you do not want to include your lint levels in your code, you can globally
 enable/disable lints by passing extra flags to Clippy during the run:

 To allow `lint_name`, run

 ```terminal
 cargo clippy -- -A clippy::lint_name
 ```

 And to warn on `lint_name`, run

 ```terminal
 cargo clippy -- -W clippy::lint_name
 ```

 This also works with lint groups. For example, you
 can run Clippy with warnings for all lints enabled:
 ```terminal
 cargo clippy -- -W clippy::pedantic
 ```

 If you care only about a single lint, you can allow all others and then explicitly warn on
 the lint(s) you are interested in:
 ```terminal
 cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
 ```

 ### Specifying the minimum supported Rust version

 Projects that intend to support old versions of Rust can disable lints pertaining to newer features by
 specifying the minimum supported Rust version (MSRV) in the clippy configuration file.

 ```toml
 msrv = "1.30.0"
 ```

 The MSRV can also be specified as an inner attribute, like below.

 ```rust
 #![feature(custom_inner_attributes)]
 #![clippy::msrv = "1.30.0"]

 fn main() {
   ...
 }
 ```

 You can also omit the patch version when specifying the MSRV, so `msrv = 1.30`
 is equivalent to `msrv = 1.30.0`.

 Note: `custom_inner_attributes` is an unstable feature, so it has to be enabled explicitly.

 Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv)

 ## Contributing

 If you want to contribute to Clippy, you can find more information in [CONTRIBUTING.md](https://github.com/rust-lang/rust-clippy/blob/master/CONTRIBUTING.md).

 ## License

 Copyright 2014-2022 The Rust Project Developers

 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
 option. Files in the project may not be
 copied, modified, or distributed except according to those terms.
	# Clippy

	[![Clippy Test](https://github.com/rust-lang/rust-clippy/workflows/Clippy%20Test/badge.svg?branch=auto&event=push)](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test%22+event%3Apush+branch%3Aauto)
	[![License: MIT OR Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)

	A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.

	[There are over 500 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)

	Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html).
	You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category.

	\| Category \| Description \| Default level \|
	\| --------------------- \| ----------------------------------------------------------------------------------- \| ------------- \|
	\| `clippy::all` \| all lints that are on by default (correctness, suspicious, style, complexity, perf) \| warn/deny \|
	\| `clippy::correctness` \| code that is outright wrong or useless \| deny \|
	\| `clippy::suspicious` \| code that is most likely wrong or useless \| warn \|
	\| `clippy::style` \| code that should be written in a more idiomatic way \| warn \|
	\| `clippy::complexity` \| code that does something simple but in a complex way \| warn \|
	\| `clippy::perf` \| code that can be written to run faster \| warn \|
	\| `clippy::pedantic` \| lints which are rather strict or have occasional false positives \| allow \|
	\| `clippy::nursery` \| new lints that are still under development \| allow \|
	\| `clippy::cargo` \| lints for the cargo manifest \| allow \|

	More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!

	The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are
	for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
	very selectively, if at all.

	Table of contents:

	* [Usage instructions](#usage)
	* [Configuration](#configuration)
	* [Contributing](#contributing)
	* [License](#license)

	## Usage

	Below are instructions on how to use Clippy as a cargo subcommand,
	in projects that do not use cargo, or in Travis CI.

	### As a cargo subcommand (`cargo clippy`)

	One way to use Clippy is by installing Clippy through rustup as a cargo
	subcommand.

	#### Step 1: Install Rustup

	You can install [Rustup](https://rustup.rs/) on supported platforms. This will help
	us install Clippy and its dependencies.

	If you already have Rustup installed, update to ensure you have the latest
	Rustup and compiler:

	```terminal
	rustup update
	```

	#### Step 2: Install Clippy

	Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:

	```terminal
	rustup component add clippy
	```
	If it says that it can't find the `clippy` component, please run `rustup self update`.

	#### Step 3: Run Clippy

	Now you can run Clippy by invoking the following command:

	```terminal
	cargo clippy
	```

	#### Automatically applying Clippy suggestions

	Clippy can automatically apply some lint suggestions, just like the compiler.

	```terminal
	cargo clippy --fix
	```

	#### Workspaces

	All the usual workspace options should work with Clippy. For example the following command
	will run Clippy on the `example` crate:

	```terminal
	cargo clippy -p example
	```

	As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies.
	If you want to run Clippy only on the given crate, use the `--no-deps` option like this:

	```terminal
	cargo clippy -p example -- --no-deps
	```

	### Using `clippy-driver`

	Clippy can also be used in projects that do not use cargo. To do so, run `clippy-driver`
	with the same arguments you use for `rustc`. For example:

	```terminal
	clippy-driver --edition 2018 -Cpanic=abort foo.rs
	```

	Note that `clippy-driver` is designed for running Clippy only and should not be used as a general
	replacement for `rustc`. `clippy-driver` may produce artifacts that are not optimized as expected,
	for example.

	### Travis CI

	You can add Clippy to Travis CI in the same way you use it locally:

	```yml
	language: rust
	rust:
	- stable
	- beta
	before_script:
	- rustup component add clippy
	script:
	- cargo clippy
	# if you want the build job to fail when encountering warnings, use
	- cargo clippy -- -D warnings
	# in order to also check tests and non-default crate features, use
	- cargo clippy --all-targets --all-features -- -D warnings
	- cargo test
	# etc.
	```

	Note that adding `-D warnings` will cause your build to fail if any warnings are found in your code.
	That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
	an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
	line. (You can swap `clippy::all` with the specific lint category you are targeting.)

	## Configuration

	Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
	value` mapping e.g.

	```toml
	avoid-breaking-exported-api = false
	blacklisted-names = ["toto", "tata", "titi"]
	cognitive-complexity-threshold = 30
	```

	See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
	lints can be configured and the meaning of the variables.

	Note that configuration changes will not apply for code that has already been compiled and cached under `./target/`;
	for example, adding a new string to `doc-valid-idents` may still result in Clippy flagging that string. To be sure that
	any configuration changes are applied, you may want to run `cargo clean` and re-compile your crate from scratch.

	To deactivate the “for further information visit lint-link” message you can
	define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.

	### Allowing/denying lints

	You can add options to your code to `allow`/`warn`/`deny` Clippy lints:

	* the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`).
	Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).

	* all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
	`#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
	lints prone to false positives.

	* only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)

	* `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.

	Note: `allow` means to suppress the lint for your code. With `warn` the lint
	will only emit a warning, while with `deny` the lint will emit an error, when
	triggering for your code. An error causes clippy to exit with an error code, so
	is useful in scripts like CI/CD.

	If you do not want to include your lint levels in your code, you can globally
	enable/disable lints by passing extra flags to Clippy during the run:

	To allow `lint_name`, run

	```terminal
	cargo clippy -- -A clippy::lint_name
	```

	And to warn on `lint_name`, run

	```terminal
	cargo clippy -- -W clippy::lint_name
	```

	This also works with lint groups. For example, you
	can run Clippy with warnings for all lints enabled:
	```terminal
	cargo clippy -- -W clippy::pedantic
	```

	If you care only about a single lint, you can allow all others and then explicitly warn on
	the lint(s) you are interested in:
	```terminal
	cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
	```

	### Specifying the minimum supported Rust version

	Projects that intend to support old versions of Rust can disable lints pertaining to newer features by
	specifying the minimum supported Rust version (MSRV) in the clippy configuration file.

	```toml
	msrv = "1.30.0"
	```

	The MSRV can also be specified as an inner attribute, like below.

	```rust
	#![feature(custom_inner_attributes)]
	#![clippy::msrv = "1.30.0"]

	fn main() {
	...
	}
	```

	You can also omit the patch version when specifying the MSRV, so `msrv = 1.30`
	is equivalent to `msrv = 1.30.0`.

	Note: `custom_inner_attributes` is an unstable feature, so it has to be enabled explicitly.

	Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv)

	## Contributing

	If you want to contribute to Clippy, you can find more information in [CONTRIBUTING.md](https://github.com/rust-lang/rust-clippy/blob/master/CONTRIBUTING.md).

	## License

	Copyright 2014-2022 The Rust Project Developers

	Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	[https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
	<LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
	option. Files in the project may not be
	copied, modified, or distributed except according to those terms.