rust-clippy/README.md

#rust-clippy

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
• len_zero: Warns on _.len() == 0 and suggests using _.is_empty() (or similar comparisons with > or !=)
• len_without_is_empty: Warns on traits or impls that have a .len() but no .is_empty() method
• cmp_owned: Warns on creating owned instances for comparing with others, e.g. x == "foo".to_string()

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

[dependencies]
clippy = "*"

More to come, please file an issue 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)]


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

deny produces error instead of warnings

##License Licensed under MPL. If you're having issues with the license, let me know and I'll try to change it to something more permissive.