rust-clippy/README.md

#rust-clippy
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A collection of lints that give helpful tips to newbies and catch oversights.

##Lints
Lints included in this crate:

 - `single_match`: Warns when a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used, and recommends `if let` instead.
 - `box_vec`: Warns on usage of `Box<Vec<T>>`
 - `linkedlist`: Warns on usage of `LinkedList`
 - `str_to_string`: Warns on usage of `str::to_string()`
 - `toplevel_ref_arg`: Warns when a function argument is declared `ref` (i.e. `fn foo(ref x: u8)`, but not `fn foo((ref x, ref y): (u8, u8))`)
 - `eq_op`: Warns on equal operands on both sides of a comparison or bitwise combination
 - `bad_bit_mask`: Denies expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
 - `ineffective_bit_mask`: Warns on expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`
 - `needless_bool` : Warns on if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`
 - `ptr_arg`: Warns on fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively
 - `approx_constant`: Warns if the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found and suggests to use the constant
 - `cmp_nan`: Denies comparisons to NAN (which will always return false, which is probably not intended)
 - `float_cmp`: Warns on `==` or `!=` comparisons of floaty typed values. As floating-point operations usually involve rounding errors, it is always better to check for approximate equality within some small bounds
 - `precedence`: Warns on expressions where precedence may trip up the unwary reader of the source and suggests adding parenthesis, e.g. `x << 2 + y` will be parsed as `x << (2 + y)`
 - `redundant_closure`: Warns on usage of eta-reducible closures like `|a| foo(a)` (which can be written as just `foo`)
 - `identity_op`: Warns on identity operations like `x + 0` or `y / 1` (which can be reduced to `x` and `y`, respectively)
 - `mut_mut`: Warns on `&mut &mut` which is either a copy'n'paste error, or shows a fundamental misunderstanding of references

To use, add the following lines to your Cargo.toml:

```
[dependencies]
clippy = "*"
```

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

##Usage
Add in your `Cargo.toml`:
```
[dependencies.clippy]
git = "https://github.com/Manishearth/rust-clippy"
```

Sample `main.rs`:
```
#![feature(plugin)]

#![plugin(clippy)]
// OPTIONS GO HERE

fn main(){
    let x = Some(1u8);
    match x {
        Some(y) => println!("{:?}", y),
        _ => ()
    }
}
```

Produce this warning:
```
src/main.rs:8:5: 11:6 warning: You seem to be trying to use match for destructuring a single type. Did you mean to use `if let`?, #[warn(single_match)] on by default
src/main.rs:8     match x {
src/main.rs:9         Some(y) => println!("{:?}", y),
src/main.rs:10         _ => ()
src/main.rs:11     }
src/main.rs:8:5: 11:6 note: Try if let Some(y) = x { ... }
src/main.rs:8     match x {
src/main.rs:9         Some(y) => println!("{:?}", y),
src/main.rs:10         _ => ()
src/main.rs:11     }
```

You can add `OPTIONS` to `allow`/`warn`/`deny`:
- the whole set using the `clippy` lint group (`#[deny(clippy)]`, etc)
- only some lints (`#[deny(single_match, box_vec)]`, etc)

*`deny` produces error instead of warnings*

##License
Licensed under [MPL](https://www.mozilla.org/MPL/2.0/). If you're having issues with the license, let me know and I'll try to change it to something more permissive.