README.md

   1 # rust-clippy
   2
   3 [![Build Status](https://travis-ci.org/Manishearth/rust-clippy.svg?branch=master)](https://travis-ci.org/Manishearth/rust-clippy)
   4 [![Windows build status](https://ci.appveyor.com/api/projects/status/github/Manishearth/rust-clippy?svg=true)](https://ci.appveyor.com/project/Manishearth/rust-clippy)
   5 [![Clippy Linting Result](http://clippy.bashy.io/github/Manishearth/rust-clippy/master/badge.svg)](http://clippy.bashy.io/github/Manishearth/rust-clippy/master/log)
   6 [![Current Version](http://meritbadge.herokuapp.com/clippy)](https://crates.io/crates/clippy)
   7 [![License: MPL-2.0](https://img.shields.io/crates/l/clippy.svg)](#License)
   8
   9 A collection of lints to catch common mistakes and improve your Rust code.
  10
  11 Table of contents:
  12
  13 *   [Lint list](#lints)
  14 *   [Usage instructions](#usage)
  15 *   [Configuration](#configuration)
  16 *   [License](#license)
  17
  18 ## Usage
  19
  20 Since this is a tool for helping the developer of a library or application
  21 write better code, it is recommended not to include clippy as a hard dependency.
  22 Options include using it as an optional dependency, as a cargo subcommand, or
  23 as an included feature during build. All of these options are detailed below.
  24
  25 As a general rule clippy will only work with the *latest* Rust nightly for now.
  26
  27 ### Optional dependency
  28
  29 If you want to make clippy an optional dependency, you can do the following:
  30
  31 In your `Cargo.toml`:
  32
  33 ```toml
  34 [dependencies]
  35 clippy = {version = "*", optional = true}
  36
  37 [features]
  38 default = []
  39 ```
  40
  41 And, in your `main.rs` or `lib.rs`:
  42
  43 ```rust
  44 #![cfg_attr(feature="clippy", feature(plugin))]
  45
  46 #![cfg_attr(feature="clippy", plugin(clippy))]
  47 ```
  48
  49 Then build by enabling the feature: `cargo build --features "clippy"`
  50
  51 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
  52 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
  53 (the `-Z no trans`, while not neccessary, will stop the compilation process after
  54 typechecking (and lints) have completed, which can significantly reduce the runtime).
  55
  56 ### As a cargo subcommand (`cargo clippy`)
  57
  58 An alternate way to use clippy is by installing clippy through cargo as a cargo
  59 subcommand.
  60
  61 ```terminal
  62 cargo install clippy
  63 ```
  64
  65 Now you can run clippy by invoking `cargo clippy`, or
  66 `rustup run nightly cargo clippy` directly from a directory that is usually
  67 compiled with stable.
  68
  69 In case you are not using rustup, you need to set the environment flag
  70 `SYSROOT` during installation so clippy knows where to find `librustc` and
  71 similar crates.
  72
  73 ```terminal
  74 SYSROOT=/path/to/rustc/sysroot cargo install clippy
  75 ```
  76
  77 ### Running clippy from the command line without installing
  78
  79 To have cargo compile your crate with clippy without needing `#![plugin(clippy)]`
  80 in your code, you can use:
  81
  82 ```terminal
  83 cargo rustc -- -L /path/to/clippy_so -Z extra-plugins=clippy
  84 ```
  85
  86 *[Note](https://github.com/Manishearth/rust-clippy/wiki#a-word-of-warning):*
  87 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
  88
  89 ### As a Compiler Plugin
  90
  91 *Note:* This is not a recommended installation method.
  92
  93 Since stable Rust is backwards compatible, you should be able to
  94 compile your stable programs with nightly Rust with clippy plugged in to
  95 circumvent this.
  96
  97 Add in your `Cargo.toml`:
  98
  99 ```toml
 100 [dependencies]
 101 clippy = "*"
 102 ```
 103
 104 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
 105 of your crate entry point (`main.rs` or `lib.rs`).
 106
 107 Sample `main.rs`:
 108
 109 ```rust
 110 #![feature(plugin)]
 111
 112 #![plugin(clippy)]
 113
 114
 115 fn main(){
 116     let x = Some(1u8);
 117     match x {
 118         Some(y) => println!("{:?}", y),
 119         _ => ()
 120     }
 121 }
 122 ```
 123
 124 Produces this warning:
 125
 126 ```terminal
 127 src/main.rs:8:5: 11:6 warning: you seem to be trying to use match for destructuring a single type. Consider using `if let`, #[warn(single_match)] on by default
 128 src/main.rs:8     match x {
 129 src/main.rs:9         Some(y) => println!("{:?}", y),
 130 src/main.rs:10         _ => ()
 131 src/main.rs:11     }
 132 src/main.rs:8:5: 11:6 help: Try
 133 if let Some(y) = x { println!("{:?}", y) }
 134 ```
 135
 136 ## Configuration
 137
 138 Some lints can be configured in a `clippy.toml` file. It contains basic `variable = value` mapping eg.
 139
 140 ```toml
 141 blacklisted-names = ["toto", "tata", "titi"]
 142 cyclomatic-complexity-threshold = 30
 143 ```
 144
 145 See the wiki for more information about which lints can be configured and the
 146 meaning of the variables.
 147
 148 You can also specify the path to the configuration file with:
 149
 150 ```rust
 151 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
 152 ```
 153
 154 To deactivate the “for further information visit *wiki-link*” message you can
 155 define the `CLIPPY_DISABLE_WIKI_LINKS` environment variable.
 156
 157 ### Allowing/denying lints
 158
 159 You can add options  to `allow`/`warn`/`deny`:
 160
 161 *   the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
 162
 163 *   all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
 164     `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
 165     lints prone to false positives.
 166
 167 *   only some lints (`#![deny(single_match, box_vec)]`, etc)
 168
 169 *   `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
 170
 171 Note: `deny` produces errors instead of warnings.
 172
 173 For convenience, `cargo clippy` automatically defines a `cargo-clippy`
 174 features. This lets you set lints level and compile with or without clippy
 175 transparently:
 176
 177 ```rust
 178 #[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
 179 ```
 180
 181 ## Lints
 182
 183 There are 183 lints included in this crate:
 184
 185 name                                                                                                                   | default | triggers on
 186 -----------------------------------------------------------------------------------------------------------------------|---------|----------------------------------------------------------------------------------------------------------------------------------
 187 [absurd_extreme_comparisons](https://github.com/Manishearth/rust-clippy/wiki#absurd_extreme_comparisons)               | warn    | a comparison with a maximum or minimum value that is always true or false
 188 [almost_swapped](https://github.com/Manishearth/rust-clippy/wiki#almost_swapped)                                       | warn    | `foo = bar; bar = foo` sequence
 189 [approx_constant](https://github.com/Manishearth/rust-clippy/wiki#approx_constant)                                     | warn    | the approximate of a known float constant (in `std::fXX::consts`)
 190 [assign_op_pattern](https://github.com/Manishearth/rust-clippy/wiki#assign_op_pattern)                                 | warn    | assigning the result of an operation on a variable to that same variable
 191 [assign_ops](https://github.com/Manishearth/rust-clippy/wiki#assign_ops)                                               | allow   | any compound assignment operation
 192 [bad_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#bad_bit_mask)                                           | warn    | expressions of the form `_ & mask == select` that will only ever return `true` or `false`
 193 [blacklisted_name](https://github.com/Manishearth/rust-clippy/wiki#blacklisted_name)                                   | warn    | usage of a blacklisted/placeholder name
 194 [block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr)               | warn    | braces that can be eliminated in conditions, e.g `if { true } ...`
 195 [block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt)               | warn    | complex blocks in conditions, e.g. `if { let x = true; x } ...`
 196 [bool_comparison](https://github.com/Manishearth/rust-clippy/wiki#bool_comparison)                                     | warn    | comparing a variable to a boolean, e.g. `if x == true`
 197 [box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec)                                                     | warn    | usage of `Box<Vec<T>>`, vector elements are already on the heap
 198 [boxed_local](https://github.com/Manishearth/rust-clippy/wiki#boxed_local)                                             | warn    | using `Box<T>` where unnecessary
 199 [builtin_type_shadow](https://github.com/Manishearth/rust-clippy/wiki#builtin_type_shadow)                             | warn    | shadowing a builtin type
 200 [cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation)                   | allow   | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
 201 [cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap)                               | allow   | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
 202 [cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss)                             | allow   | casts that cause loss of precision, e.g `x as f32` where `x: u64`
 203 [cast_sign_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_sign_loss)                                       | allow   | casts from signed types to unsigned types, e.g `x as u32` where `x: i32`
 204 [char_lit_as_u8](https://github.com/Manishearth/rust-clippy/wiki#char_lit_as_u8)                                       | warn    | casting a character literal to u8
 205 [chars_next_cmp](https://github.com/Manishearth/rust-clippy/wiki#chars_next_cmp)                                       | warn    | using `.chars().next()` to check if a string starts with a char
 206 [clone_double_ref](https://github.com/Manishearth/rust-clippy/wiki#clone_double_ref)                                   | warn    | using `clone` on `&&T`
 207 [clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#clone_on_copy)                                         | warn    | using `clone` on a `Copy` type
 208 [cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan)                                                     | deny    | comparisons to NAN, which will always return false, probably not intended
 209 [cmp_null](https://github.com/Manishearth/rust-clippy/wiki#cmp_null)                                                   | warn    | comparing a pointer to a null pointer, suggesting to use `.is_null()` instead.
 210 [cmp_owned](https://github.com/Manishearth/rust-clippy/wiki#cmp_owned)                                                 | warn    | creating owned instances for comparing with others, e.g. `x == "foo".to_string()`
 211 [collapsible_if](https://github.com/Manishearth/rust-clippy/wiki#collapsible_if)                                       | warn    | `if`s that can be collapsed (e.g. `if x { if y { ... } }` and `else { if x { ... } }`)
 212 [crosspointer_transmute](https://github.com/Manishearth/rust-clippy/wiki#crosspointer_transmute)                       | warn    | transmutes that have to or from types that are a pointer to the other
 213 [cyclomatic_complexity](https://github.com/Manishearth/rust-clippy/wiki#cyclomatic_complexity)                         | warn    | functions that should be split up into multiple functions
 214 [deprecated_semver](https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver)                                 | warn    | use of `#[deprecated(since = "x")]` where x is not semver
 215 [deref_addrof](https://github.com/Manishearth/rust-clippy/wiki#deref_addrof)                                           | warn    | use of `*&` or `*&mut` in an expression
 216 [derive_hash_xor_eq](https://github.com/Manishearth/rust-clippy/wiki#derive_hash_xor_eq)                               | warn    | deriving `Hash` but implementing `PartialEq` explicitly
 217 [diverging_sub_expression](https://github.com/Manishearth/rust-clippy/wiki#diverging_sub_expression)                   | warn    | whether an expression contains a diverging sub expression
 218 [doc_markdown](https://github.com/Manishearth/rust-clippy/wiki#doc_markdown)                                           | warn    | presence of `_`, `::` or camel-case outside backticks in documentation
 219 [double_neg](https://github.com/Manishearth/rust-clippy/wiki#double_neg)                                               | warn    | `--x`, which is a double negation of `x` and not a pre-decrement as in C/C++
 220 [double_parens](https://github.com/Manishearth/rust-clippy/wiki#double_parens)                                         | warn    | Warn on unnecessary double parentheses
 221 [drop_ref](https://github.com/Manishearth/rust-clippy/wiki#drop_ref)                                                   | warn    | calls to `std::mem::drop` with a reference instead of an owned value
 222 [duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument)         | warn    | function arguments having names which only differ by an underscore
 223 [empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop)                                               | warn    | empty `loop {}`, which should block or sleep
 224 [enum_clike_unportable_variant](https://github.com/Manishearth/rust-clippy/wiki#enum_clike_unportable_variant)         | warn    | C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`
 225 [enum_glob_use](https://github.com/Manishearth/rust-clippy/wiki#enum_glob_use)                                         | allow   | use items that import all variants of an enum
 226 [enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#enum_variant_names)                               | warn    | enums where all variants share a prefix/postfix
 227 [eq_op](https://github.com/Manishearth/rust-clippy/wiki#eq_op)                                                         | warn    | equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)
 228 [eval_order_dependence](https://github.com/Manishearth/rust-clippy/wiki#eval_order_dependence)                         | warn    | whether a variable read occurs before a write depends on sub-expression evaluation order
 229 [expl_impl_clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#expl_impl_clone_on_copy)                     | warn    | implementing `Clone` explicitly on `Copy` types
 230 [explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop)                         | warn    | for-looping with an explicit counter when `_.enumerate()` would do
 231 [explicit_into_iter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_into_iter_loop)                     | warn    | for-looping over `_.into_iter()` when `_` would do
 232 [explicit_iter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_iter_loop)                               | warn    | for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do
 233 [extend_from_slice](https://github.com/Manishearth/rust-clippy/wiki#extend_from_slice)                                 | warn    | `.extend_from_slice(_)` is a faster way to extend a Vec by a slice
 234 [filter_map](https://github.com/Manishearth/rust-clippy/wiki#filter_map)                                               | allow   | using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call
 235 [filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next)                                             | warn    | using `filter(p).next()`, which is more succinctly expressed as `.find(p)`
 236 [float_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#float_arithmetic)                                   | allow   | any floating-point arithmetic statement
 237 [float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp)                                                 | warn    | using `==` or `!=` on float values instead of comparing difference with an epsilon
 238 [for_kv_map](https://github.com/Manishearth/rust-clippy/wiki#for_kv_map)                                               | warn    | looping on a map using `iter` when `keys` or `values` would do
 239 [for_loop_over_option](https://github.com/Manishearth/rust-clippy/wiki#for_loop_over_option)                           | warn    | for-looping over an `Option`, which is more clearly expressed as an `if let`
 240 [for_loop_over_result](https://github.com/Manishearth/rust-clippy/wiki#for_loop_over_result)                           | warn    | for-looping over a `Result`, which is more clearly expressed as an `if let`
 241 [forget_ref](https://github.com/Manishearth/rust-clippy/wiki#forget_ref)                                               | warn    | calls to `std::mem::forget` with a reference instead of an owned value
 242 [get_unwrap](https://github.com/Manishearth/rust-clippy/wiki#get_unwrap)                                               | warn    | using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead
 243 [identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op)                                             | warn    | using identity operations, e.g. `x + 0` or `y / 1`
 244 [if_let_redundant_pattern_matching](https://github.com/Manishearth/rust-clippy/wiki#if_let_redundant_pattern_matching) | warn    | use the proper utility function avoiding an `if let`
 245 [if_let_some_result](https://github.com/Manishearth/rust-clippy/wiki#if_let_some_result)                               | warn    | usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead
 246 [if_not_else](https://github.com/Manishearth/rust-clippy/wiki#if_not_else)                                             | allow   | `if` branches that could be swapped so no negation operation is necessary on the condition
 247 [if_same_then_else](https://github.com/Manishearth/rust-clippy/wiki#if_same_then_else)                                 | warn    | if with the same *then* and *else* blocks
 248 [ifs_same_cond](https://github.com/Manishearth/rust-clippy/wiki#ifs_same_cond)                                         | warn    | consecutive `ifs` with the same condition
 249 [indexing_slicing](https://github.com/Manishearth/rust-clippy/wiki#indexing_slicing)                                   | allow   | indexing/slicing usage
 250 [ineffective_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#ineffective_bit_mask)                           | warn    | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`
 251 [inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always)                                         | warn    | use of `#[inline(always)]`
 252 [integer_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#integer_arithmetic)                               | allow   | any integer arithmetic statement
 253 [invalid_regex](https://github.com/Manishearth/rust-clippy/wiki#invalid_regex)                                         | deny    | invalid regular expressions
 254 [invalid_upcast_comparisons](https://github.com/Manishearth/rust-clippy/wiki#invalid_upcast_comparisons)               | allow   | a comparison involving an upcast which is always true or false
 255 [items_after_statements](https://github.com/Manishearth/rust-clippy/wiki#items_after_statements)                       | allow   | blocks where an item comes after a statement
 256 [iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop)                                       | warn    | for-looping over `_.next()` which is probably not intended
 257 [iter_nth](https://github.com/Manishearth/rust-clippy/wiki#iter_nth)                                                   | warn    | using `.iter().nth()` on a standard library type with O(1) element access
 258 [iter_skip_next](https://github.com/Manishearth/rust-clippy/wiki#iter_skip_next)                                       | warn    | using `.skip(x).next()` on an iterator
 259 [len_without_is_empty](https://github.com/Manishearth/rust-clippy/wiki#len_without_is_empty)                           | warn    | traits or impls with a public `len` method but no corresponding `is_empty` method
 260 [len_zero](https://github.com/Manishearth/rust-clippy/wiki#len_zero)                                                   | warn    | checking `.len() == 0` or `.len() > 0` (or similar) when `.is_empty()` could be used instead
 261 [let_and_return](https://github.com/Manishearth/rust-clippy/wiki#let_and_return)                                       | warn    | creating a let-binding and then immediately returning it like `let x = expr; x` at the end of a block
 262 [let_unit_value](https://github.com/Manishearth/rust-clippy/wiki#let_unit_value)                                       | warn    | creating a let binding to a value of unit type, which usually can't be used afterwards
 263 [linkedlist](https://github.com/Manishearth/rust-clippy/wiki#linkedlist)                                               | warn    | usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque
 264 [logic_bug](https://github.com/Manishearth/rust-clippy/wiki#logic_bug)                                                 | warn    | boolean expressions that contain terminals which can be eliminated
 265 [manual_swap](https://github.com/Manishearth/rust-clippy/wiki#manual_swap)                                             | warn    | manual swap of two variables
 266 [many_single_char_names](https://github.com/Manishearth/rust-clippy/wiki#many_single_char_names)                       | warn    | too many single character bindings
 267 [map_clone](https://github.com/Manishearth/rust-clippy/wiki#map_clone)                                                 | warn    | using `.map(|x| x.clone())` to clone an iterator or option's contents
 268 [map_entry](https://github.com/Manishearth/rust-clippy/wiki#map_entry)                                                 | warn    | use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`
 269 [match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool)                                               | warn    | a match on a boolean expression instead of an `if..else` block
 270 [match_overlapping_arm](https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm)                         | warn    | a match with overlapping arms
 271 [match_ref_pats](https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats)                                       | warn    | a match or `if let` with all arms prefixed with `&` instead of deref-ing the match expression
 272 [match_same_arms](https://github.com/Manishearth/rust-clippy/wiki#match_same_arms)                                     | warn    | `match` with identical arm bodies
 273 [mem_forget](https://github.com/Manishearth/rust-clippy/wiki#mem_forget)                                               | allow   | `mem::forget` usage on `Drop` types, likely to cause memory leaks
 274 [min_max](https://github.com/Manishearth/rust-clippy/wiki#min_max)                                                     | warn    | `min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant
 275 [misrefactored_assign_op](https://github.com/Manishearth/rust-clippy/wiki#misrefactored_assign_op)                     | warn    | having a variable on both sides of an assign op
 276 [missing_docs_in_private_items](https://github.com/Manishearth/rust-clippy/wiki#missing_docs_in_private_items)         | allow   | detects missing documentation for public and private members
 277 [mixed_case_hex_literals](https://github.com/Manishearth/rust-clippy/wiki#mixed_case_hex_literals)                     | warn    | hex literals whose letter digits are not consistently upper- or lowercased
 278 [module_inception](https://github.com/Manishearth/rust-clippy/wiki#module_inception)                                   | warn    | modules that have the same name as their parent module
 279 [modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one)                                               | warn    | taking a number modulo 1, which always returns 0
 280 [mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut)                                                     | allow   | usage of double-mut refs, e.g. `&mut &mut ...`
 281 [mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic)                                           | warn    | using a mutex where an atomic value could be used instead
 282 [mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer)                                         | allow   | using a mutex for an integer type
 283 [needless_bool](https://github.com/Manishearth/rust-clippy/wiki#needless_bool)                                         | warn    | if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`
 284 [needless_borrow](https://github.com/Manishearth/rust-clippy/wiki#needless_borrow)                                     | warn    | taking a reference that is going to be automatically dereferenced
 285 [needless_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#needless_lifetimes)                               | warn    | using explicit lifetimes for references in function arguments when elision rules would allow omitting them
 286 [needless_range_loop](https://github.com/Manishearth/rust-clippy/wiki#needless_range_loop)                             | warn    | for-looping over a range of indices where an iterator over items would do
 287 [needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return)                                     | warn    | using a return statement like `return expr;` where an expression would suffice
 288 [needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update)                                     | warn    | using `Foo { ..base }` when there are no missing fields
 289 [neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply)                                           | warn    | multiplying integers with -1
 290 [new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self)                                     | warn    | not returning `Self` in a `new` method
 291 [new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default)                             | warn    | `fn new() -> Self` method without `Default` implementation
 292 [new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive)               | warn    | `fn new() -> Self` without `#[derive]`able `Default` implementation
 293 [no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect)                                                 | warn    | statements with no effect
 294 [non_ascii_literal](https://github.com/Manishearth/rust-clippy/wiki#non_ascii_literal)                                 | allow   | using any literal non-ASCII chars in a string literal instead of using the `\\u` escape
 295 [nonminimal_bool](https://github.com/Manishearth/rust-clippy/wiki#nonminimal_bool)                                     | allow   | boolean expressions that can be written more concisely
 296 [nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options)                   | warn    | nonsensical combination of options for opening a file
 297 [not_unsafe_ptr_arg_deref](https://github.com/Manishearth/rust-clippy/wiki#not_unsafe_ptr_arg_deref)                   | warn    | public functions dereferencing raw pointer arguments but not marked `unsafe`
 298 [ok_expect](https://github.com/Manishearth/rust-clippy/wiki#ok_expect)                                                 | warn    | using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result
 299 [option_map_unwrap_or](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or)                           | allow   | using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`
 300 [option_map_unwrap_or_else](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or_else)                 | allow   | using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`
 301 [option_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#option_unwrap_used)                               | allow   | using `Option.unwrap()`, which should at least get a better message using `expect()`
 302 [or_fun_call](https://github.com/Manishearth/rust-clippy/wiki#or_fun_call)                                             | warn    | using any `*or` method with a function call, which suggests `*or_else`
 303 [out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing)                       | deny    | out of bounds constant indexing
 304 [overflow_check_conditional](https://github.com/Manishearth/rust-clippy/wiki#overflow_check_conditional)               | warn    | overflow checks inspired by C which are likely to panic
 305 [panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params)                                           | warn    | missing parameters in `panic!` calls
 306 [partialeq_ne_impl](https://github.com/Manishearth/rust-clippy/wiki#partialeq_ne_impl)                                 | warn    | re-implementing `PartialEq::ne`
 307 [precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence)                                               | warn    | operations where precedence may be unclear
 308 [print_stdout](https://github.com/Manishearth/rust-clippy/wiki#print_stdout)                                           | allow   | printing on stdout
 309 [print_with_newline](https://github.com/Manishearth/rust-clippy/wiki#print_with_newline)                               | warn    | using `print!()` with a format string that ends in a newline
 310 [ptr_arg](https://github.com/Manishearth/rust-clippy/wiki#ptr_arg)                                                     | warn    | fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively
 311 [pub_enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#pub_enum_variant_names)                       | allow   | enums where all variants share a prefix/postfix
 312 [range_step_by_zero](https://github.com/Manishearth/rust-clippy/wiki#range_step_by_zero)                               | warn    | using `Range::step_by(0)`, which produces an infinite iterator
 313 [range_zip_with_len](https://github.com/Manishearth/rust-clippy/wiki#range_zip_with_len)                               | warn    | zipping iterator with a range when `enumerate()` would do
 314 [redundant_closure](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure)                                 | warn    | redundant closures, i.e. `|a| foo(a)` (which can be written as just `foo`)
 315 [redundant_closure_call](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure_call)                       | warn    | throwaway closures called in the expression they are defined
 316 [redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern)                                 | warn    | using `name @ _` in a pattern
 317 [regex_macro](https://github.com/Manishearth/rust-clippy/wiki#regex_macro)                                             | warn    | use of `regex!(_)` instead of `Regex::new(_)`
 318 [result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used)                               | allow   | using `Result.unwrap()`, which might be better handled
 319 [reverse_range_loop](https://github.com/Manishearth/rust-clippy/wiki#reverse_range_loop)                               | warn    | iteration over an empty range, such as `10..0` or `5..5`
 320 [search_is_some](https://github.com/Manishearth/rust-clippy/wiki#search_is_some)                                       | warn    | using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`
 321 [serde_api_misuse](https://github.com/Manishearth/rust-clippy/wiki#serde_api_misuse)                                   | warn    | various things that will negatively affect your serde experience
 322 [shadow_reuse](https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse)                                           | allow   | rebinding a name to an expression that re-uses the original value, e.g. `let x = x + 1`
 323 [shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same)                                             | allow   | rebinding a name to itself, e.g. `let mut x = &mut x`
 324 [shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated)                                   | allow   | rebinding a name without even using the original value
 325 [short_circuit_statement](https://github.com/Manishearth/rust-clippy/wiki#short_circuit_statement)                     | warn    | using a short circuit boolean condition as a statement
 326 [should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait)                       | warn    | defining a method that should be implementing a std trait
 327 [similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names)                                         | allow   | similarly named items and bindings
 328 [single_char_pattern](https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern)                             | warn    | using a single-character str where a char could be used, e.g. `_.split("x")`
 329 [single_match](https://github.com/Manishearth/rust-clippy/wiki#single_match)                                           | warn    | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) instead of `if let`
 330 [single_match_else](https://github.com/Manishearth/rust-clippy/wiki#single_match_else)                                 | allow   | a match statement with a two arms where the second arm's pattern is a wildcard instead of `if let`
 331 [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add)                                               | allow   | using `x + ..` where x is a `String` instead of `push_str()`
 332 [string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign)                                 | allow   | using `x = x + ..` where x is a `String` instead of `push_str()`
 333 [string_extend_chars](https://github.com/Manishearth/rust-clippy/wiki#string_extend_chars)                             | warn    | using `x.extend(s.chars())` where s is a `&str` or `String`
 334 [string_lit_as_bytes](https://github.com/Manishearth/rust-clippy/wiki#string_lit_as_bytes)                             | warn    | calling `as_bytes` on a string literal instead of using a byte string literal
 335 [stutter](https://github.com/Manishearth/rust-clippy/wiki#stutter)                                                     | allow   | type names prefixed/postfixed with their containing module's name
 336 [suspicious_assignment_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_assignment_formatting)   | warn    | suspicious formatting of `*=`, `-=` or `!=`
 337 [suspicious_else_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_else_formatting)               | warn    | suspicious formatting of `else if`
 338 [temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment)                           | warn    | assignments to temporaries
 339 [temporary_cstring_as_ptr](https://github.com/Manishearth/rust-clippy/wiki#temporary_cstring_as_ptr)                   | warn    | getting the inner pointer of a temporary `CString`
 340 [too_many_arguments](https://github.com/Manishearth/rust-clippy/wiki#too_many_arguments)                               | warn    | functions with too many arguments
 341 [toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg)                                   | warn    | an entire binding declared as `ref`, in a function argument or a `let` statement
 342 [transmute_ptr_to_ref](https://github.com/Manishearth/rust-clippy/wiki#transmute_ptr_to_ref)                           | warn    | transmutes from a pointer to a reference type
 343 [trivial_regex](https://github.com/Manishearth/rust-clippy/wiki#trivial_regex)                                         | warn    | trivial regular expressions
 344 [type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity)                                     | warn    | usage of very complex types that might be better factored into `type` definitions
 345 [unicode_not_nfc](https://github.com/Manishearth/rust-clippy/wiki#unicode_not_nfc)                                     | allow   | using a unicode literal not in NFC normal form (see [unicode tr15](http://www.unicode.org/reports/tr15/) for further information)
 346 [unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp)                                                   | warn    | comparing unit values
 347 [unnecessary_mut_passed](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_mut_passed)                       | warn    | an argument passed as a mutable reference although the callee only demands an immutable reference
 348 [unnecessary_operation](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_operation)                         | warn    | outer expressions with no effect
 349 [unneeded_field_pattern](https://github.com/Manishearth/rust-clippy/wiki#unneeded_field_pattern)                       | warn    | struct fields bound to a wildcard instead of using `..`
 350 [unsafe_removed_from_name](https://github.com/Manishearth/rust-clippy/wiki#unsafe_removed_from_name)                   | warn    | `unsafe` removed from API names on import
 351 [unseparated_literal_suffix](https://github.com/Manishearth/rust-clippy/wiki#unseparated_literal_suffix)               | allow   | literals whose suffix is not separated by an underscore
 352 [unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect)                                       | warn    | `collect()`ing an iterator without using the result; this is usually better written as a for loop
 353 [unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label)                                           | warn    | unused labels
 354 [unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes)                                   | warn    | unused lifetimes in function definitions
 355 [use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug)                                                 | allow   | use of `Debug`-based formatting
 356 [used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding)                     | allow   | using a binding which is prefixed with an underscore
 357 [useless_attribute](https://github.com/Manishearth/rust-clippy/wiki#useless_attribute)                                 | warn    | use of lint attributes on `extern crate` items
 358 [useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format)                                       | warn    | useless use of `format!`
 359 [useless_let_if_seq](https://github.com/Manishearth/rust-clippy/wiki#useless_let_if_seq)                               | warn    | unidiomatic `let mut` declaration followed by initialization in `if`
 360 [useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute)                                 | warn    | transmutes that have the same to and from types or could be a cast/coercion
 361 [useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec)                                             | warn    | useless `vec!`
 362 [while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop)                                       | warn    | `loop { if let { ... } else break }`, which can be written as a `while let` loop
 363 [while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator)                         | warn    | using a while-let loop instead of a for loop on an iterator
 364 [wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention)                 | allow   | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
 365 [wrong_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention)                         | warn    | defining a method named with an established prefix (like "into_") that takes `self` with the wrong convention
 366 [wrong_transmute](https://github.com/Manishearth/rust-clippy/wiki#wrong_transmute)                                     | warn    | transmutes that are confusing at best, undefined behaviour at worst and always useless
 367 [zero_divided_by_zero](https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero)                           | warn    | usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN
 368 [zero_prefixed_literal](https://github.com/Manishearth/rust-clippy/wiki#zero_prefixed_literal)                         | warn    | integer literals starting with `0`
 369 [zero_width_space](https://github.com/Manishearth/rust-clippy/wiki#zero_width_space)                                   | deny    | using a zero-width space in a string literal, which is confusing
 370
 371 More to come, please [file an issue](https://github.com/Manishearth/rust-clippy/issues) if you have ideas!
 372
 373 ## License
 374
 375 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
 376 If you're having issues with the license, let me know and I'll try to change it to something more permissive.