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290 lines
11 KiB
Markdown
290 lines
11 KiB
Markdown
# Clippy
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[/badge.svg?branch=auto&event=push)](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test+(bors)%22+event%3Apush+branch%3Aauto)
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[](#license)
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A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
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[There are over 600 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
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Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html).
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You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category.
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| Category | Description | Default level |
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|-----------------------|-------------------------------------------------------------------------------------|---------------|
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| `clippy::all` | all lints that are on by default (correctness, suspicious, style, complexity, perf) | **warn/deny** |
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| `clippy::correctness` | code that is outright wrong or useless | **deny** |
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| `clippy::suspicious` | code that is most likely wrong or useless | **warn** |
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| `clippy::style` | code that should be written in a more idiomatic way | **warn** |
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| `clippy::complexity` | code that does something simple but in a complex way | **warn** |
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| `clippy::perf` | code that can be written to run faster | **warn** |
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| `clippy::pedantic` | lints which are rather strict or have occasional false positives | allow |
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| `clippy::restriction` | lints which prevent the use of language and library features[^restrict] | allow |
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| `clippy::nursery` | new lints that are still under development | allow |
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| `clippy::cargo` | lints for the cargo manifest | allow |
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More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
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The `restriction` category should, *emphatically*, not be enabled as a whole. The contained
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lints may lint against perfectly reasonable code, may not have an alternative suggestion,
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and may contradict any other lints (including other categories). Lints should be considered
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on a case-by-case basis before enabling.
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[^restrict]: Some use cases for `restriction` lints include:
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- Strict coding styles (e.g. [`clippy::else_if_without_else`]).
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- Additional restrictions on CI (e.g. [`clippy::todo`]).
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- Preventing panicking in certain functions (e.g. [`clippy::unwrap_used`]).
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- Running a lint only on a subset of code (e.g. `#[forbid(clippy::float_arithmetic)]` on a module).
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[`clippy::else_if_without_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#else_if_without_else
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[`clippy::todo`]: https://rust-lang.github.io/rust-clippy/master/index.html#todo
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[`clippy::unwrap_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_used
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---
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Table of contents:
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* [Usage instructions](#usage)
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* [Configuration](#configuration)
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* [Contributing](#contributing)
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* [License](#license)
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## Usage
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Below are instructions on how to use Clippy as a cargo subcommand,
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in projects that do not use cargo, or in Travis CI.
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### As a cargo subcommand (`cargo clippy`)
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One way to use Clippy is by installing Clippy through rustup as a cargo
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subcommand.
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#### Step 1: Install Rustup
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You can install [Rustup](https://rustup.rs/) on supported platforms. This will help
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us install Clippy and its dependencies.
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If you already have Rustup installed, update to ensure you have the latest
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Rustup and compiler:
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```terminal
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rustup update
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```
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#### Step 2: Install Clippy
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Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
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```terminal
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rustup component add clippy
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```
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If it says that it can't find the `clippy` component, please run `rustup self update`.
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#### Step 3: Run Clippy
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Now you can run Clippy by invoking the following command:
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```terminal
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cargo clippy
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```
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#### Automatically applying Clippy suggestions
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Clippy can automatically apply some lint suggestions, just like the compiler. Note that `--fix` implies
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`--all-targets`, so it can fix as much code as it can.
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```terminal
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cargo clippy --fix
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```
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#### Workspaces
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All the usual workspace options should work with Clippy. For example the following command
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will run Clippy on the `example` crate:
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```terminal
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cargo clippy -p example
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```
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As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies.
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If you want to run Clippy **only** on the given crate, use the `--no-deps` option like this:
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```terminal
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cargo clippy -p example -- --no-deps
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```
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### Using `clippy-driver`
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Clippy can also be used in projects that do not use cargo. To do so, run `clippy-driver`
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with the same arguments you use for `rustc`. For example:
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```terminal
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clippy-driver --edition 2018 -Cpanic=abort foo.rs
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```
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Note that `clippy-driver` is designed for running Clippy only and should not be used as a general
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replacement for `rustc`. `clippy-driver` may produce artifacts that are not optimized as expected,
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for example.
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### Travis CI
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You can add Clippy to Travis CI in the same way you use it locally:
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```yaml
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language: rust
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rust:
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- stable
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- beta
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before_script:
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- rustup component add clippy
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script:
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- cargo clippy
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# if you want the build job to fail when encountering warnings, use
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- cargo clippy -- -D warnings
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# in order to also check tests and non-default crate features, use
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- cargo clippy --all-targets --all-features -- -D warnings
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- cargo test
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# etc.
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```
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Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
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That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
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an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
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line. (You can swap `clippy::all` with the specific lint category you are targeting.)
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## Configuration
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### Allowing/denying lints
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You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
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* the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`).
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Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).
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* all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
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`#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
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lints prone to false positives.
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* only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
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* `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
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Note: `allow` means to suppress the lint for your code. With `warn` the lint
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will only emit a warning, while with `deny` the lint will emit an error, when
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triggering for your code. An error causes clippy to exit with an error code, so
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is useful in scripts like CI/CD.
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If you do not want to include your lint levels in your code, you can globally
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enable/disable lints by passing extra flags to Clippy during the run:
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To allow `lint_name`, run
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```terminal
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cargo clippy -- -A clippy::lint_name
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```
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And to warn on `lint_name`, run
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```terminal
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cargo clippy -- -W clippy::lint_name
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```
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This also works with lint groups. For example, you
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can run Clippy with warnings for all lints enabled:
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```terminal
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cargo clippy -- -W clippy::pedantic
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```
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If you care only about a single lint, you can allow all others and then explicitly warn on
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the lint(s) you are interested in:
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```terminal
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cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
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```
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### Configure the behavior of some lints
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Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
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value` mapping e.g.
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```toml
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avoid-breaking-exported-api = false
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disallowed-names = ["toto", "tata", "titi"]
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```
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The [table of configurations](https://doc.rust-lang.org/nightly/clippy/lint_configuration.html)
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contains all config values, their default, and a list of lints they affect.
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Each [configurable lint](https://rust-lang.github.io/rust-clippy/master/index.html#Configuration)
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, also contains information about these values.
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For configurations that are a list type with default values such as
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[disallowed-names](https://rust-lang.github.io/rust-clippy/master/index.html#disallowed_names),
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you can use the unique value `".."` to extend the default values instead of replacing them.
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```toml
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# default of disallowed-names is ["foo", "baz", "quux"]
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disallowed-names = ["bar", ".."] # -> ["bar", "foo", "baz", "quux"]
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```
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> **Note**
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>
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> `clippy.toml` or `.clippy.toml` cannot be used to allow/deny lints.
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To deactivate the “for further information visit *lint-link*” message you can
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define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
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### Specifying the minimum supported Rust version
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Projects that intend to support old versions of Rust can disable lints pertaining to newer features by
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specifying the minimum supported Rust version (MSRV) in the clippy configuration file.
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```toml
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msrv = "1.30.0"
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```
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Alternatively, the [`rust-version` field](https://doc.rust-lang.org/cargo/reference/manifest.html#the-rust-version-field)
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in the `Cargo.toml` can be used.
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```toml
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# Cargo.toml
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rust-version = "1.30"
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```
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The MSRV can also be specified as an attribute, like below.
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```rust,ignore
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#![feature(custom_inner_attributes)]
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#![clippy::msrv = "1.30.0"]
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fn main() {
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...
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}
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```
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You can also omit the patch version when specifying the MSRV, so `msrv = 1.30`
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is equivalent to `msrv = 1.30.0`.
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Note: `custom_inner_attributes` is an unstable feature, so it has to be enabled explicitly.
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Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv)
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## Contributing
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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).
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## License
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<!-- REUSE-IgnoreStart -->
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Copyright 2014-2023 The Rust Project Developers
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Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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[https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
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<LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
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option. Files in the project may not be
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copied, modified, or distributed except according to those terms.
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<!-- REUSE-IgnoreEnd -->
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