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 [![Clippy Linting Result](http://clippy.bashy.io/github/Manishearth/rust-clippy/master/badge.svg)](http://clippy.bashy.io/github/Manishearth/rust-clippy/master/log)
   5 [![Current Version](http://meritbadge.herokuapp.com/clippy)](https://crates.io/crates/clippy)
   6 [![License: MPL-2.0](https://img.shields.io/crates/l/clippy.svg)](#License)
   7
   8 A collection of lints to catch common mistakes and improve your Rust code.
   9
  10 Table of contents:
  11
  12 *   [Lint list](#lints)
  13 *   [Usage instructions](#usage)
  14 *   [Configuration](#configuration)
  15 *   [*clippy-service*](#link-with-clippy-service)
  16 *   [License](#license)
  17
  18 ## Lints
  19
  20 There are 158 lints included in this crate:
  21
  22 name                                                                                                                 | default | meaning
  23 ---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  24 [absurd_extreme_comparisons](https://github.com/Manishearth/rust-clippy/wiki#absurd_extreme_comparisons)             | warn    | a comparison involving a maximum or minimum value involves a case that is always true or always false
  25 [almost_swapped](https://github.com/Manishearth/rust-clippy/wiki#almost_swapped)                                     | warn    | `foo = bar; bar = foo` sequence
  26 [approx_constant](https://github.com/Manishearth/rust-clippy/wiki#approx_constant)                                   | warn    | the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found; suggests to use the constant
  27 [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
  28 [assign_ops](https://github.com/Manishearth/rust-clippy/wiki#assign_ops)                                             | allow   | any assignment operation
  29 [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` (because in the example `select` containing bits that `mask` doesn't have)
  30 [blacklisted_name](https://github.com/Manishearth/rust-clippy/wiki#blacklisted_name)                                 | warn    | usage of a blacklisted/placeholder name
  31 [block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr)             | warn    | braces can be eliminated in conditions that are expressions, e.g `if { true } ...`
  32 [block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt)             | warn    | avoid complex blocks in conditions, instead move the block higher and bind it with 'let'; e.g: `if { let x = true; x } ...`
  33 [bool_comparison](https://github.com/Manishearth/rust-clippy/wiki#bool_comparison)                                   | warn    | comparing a variable to a boolean, e.g. `if x == true`
  34 [box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec)                                                   | warn    | usage of `Box<Vec<T>>`, vector elements are already on the heap
  35 [boxed_local](https://github.com/Manishearth/rust-clippy/wiki#boxed_local)                                           | warn    | using `Box<T>` where unnecessary
  36 [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`
  37 [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`
  38 [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`
  39 [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`
  40 [char_lit_as_u8](https://github.com/Manishearth/rust-clippy/wiki#char_lit_as_u8)                                     | warn    | Casting a character literal to u8
  41 [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
  42 [clone_double_ref](https://github.com/Manishearth/rust-clippy/wiki#clone_double_ref)                                 | warn    | using `clone` on `&&T`
  43 [clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#clone_on_copy)                                       | warn    | using `clone` on a `Copy` type
  44 [cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan)                                                   | deny    | comparisons to NAN (which will always return false, which is probably not intended)
  45 [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()`
  46 [collapsible_if](https://github.com/Manishearth/rust-clippy/wiki#collapsible_if)                                     | warn    | two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }` and an `else { if .. } expression can be collapsed to `else if`
  47 [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
  48 [cyclomatic_complexity](https://github.com/Manishearth/rust-clippy/wiki#cyclomatic_complexity)                       | warn    | finds functions that should be split up into multiple functions
  49 [deprecated_semver](https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver)                               | warn    | `Warn` on `#[deprecated(since = "x")]` where x is not semver
  50 [derive_hash_xor_eq](https://github.com/Manishearth/rust-clippy/wiki#derive_hash_xor_eq)                             | warn    | deriving `Hash` but implementing `PartialEq` explicitly
  51 [doc_markdown](https://github.com/Manishearth/rust-clippy/wiki#doc_markdown)                                         | warn    | checks for the presence of `_`, `::` or camel-case outside ticks in documentation
  52 [double_neg](https://github.com/Manishearth/rust-clippy/wiki#double_neg)                                             | warn    | `--x` is a double negation of `x` and not a pre-decrement as in C or C++
  53 [drop_ref](https://github.com/Manishearth/rust-clippy/wiki#drop_ref)                                                 | warn    | call to `std::mem::drop` with a reference instead of an owned value, which will not call the `Drop::drop` method on the underlying value
  54 [duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument)       | warn    | Function arguments having names which only differ by an underscore
  55 [empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop)                                             | warn    | empty `loop {}` detected
  56 [enum_clike_unportable_variant](https://github.com/Manishearth/rust-clippy/wiki#enum_clike_unportable_variant)       | warn    | finds C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`
  57 [enum_glob_use](https://github.com/Manishearth/rust-clippy/wiki#enum_glob_use)                                       | allow   | finds use items that import all variants of an enum
  58 [enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#enum_variant_names)                             | warn    | finds enums where all variants share a prefix/postfix
  59 [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`)
  60 [expl_impl_clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#expl_impl_clone_on_copy)                   | warn    | implementing `Clone` explicitly on `Copy` types
  61 [explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop)                       | warn    | for-looping with an explicit counter when `_.enumerate()` would do
  62 [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
  63 [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
  64 [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
  65 [filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next)                                           | warn    | using `filter(p).next()`, which is more succinctly expressed as `.find(p)`
  66 [float_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#float_arithmetic)                                 | allow   | Any floating-point arithmetic statement
  67 [float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp)                                               | warn    | using `==` or `!=` on float values (as floating-point operations usually involve rounding errors, it is always better to check for approximate equality within small bounds)
  68 [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
  69 [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`
  70 [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`
  71 [identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op)                                           | warn    | using identity operations, e.g. `x + 0` or `y / 1`
  72 [if_not_else](https://github.com/Manishearth/rust-clippy/wiki#if_not_else)                                           | allow   | finds if branches that could be swapped so no negation operation is necessary on the condition
  73 [if_same_then_else](https://github.com/Manishearth/rust-clippy/wiki#if_same_then_else)                               | warn    | if with the same *then* and *else* blocks
  74 [ifs_same_cond](https://github.com/Manishearth/rust-clippy/wiki#ifs_same_cond)                                       | warn    | consecutive `ifs` with the same condition
  75 [indexing_slicing](https://github.com/Manishearth/rust-clippy/wiki#indexing_slicing)                                 | allow   | indexing/slicing usage
  76 [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`
  77 [inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always)                                       | warn    | `#[inline(always)]` is a bad idea in most cases
  78 [integer_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#integer_arithmetic)                             | allow   | Any integer arithmetic statement
  79 [invalid_regex](https://github.com/Manishearth/rust-clippy/wiki#invalid_regex)                                       | deny    | finds invalid regular expressions
  80 [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
  81 [items_after_statements](https://github.com/Manishearth/rust-clippy/wiki#items_after_statements)                     | allow   | finds blocks where an item comes after a statement
  82 [iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop)                                     | warn    | for-looping over `_.next()` which is probably not intended
  83 [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
  84 [len_without_is_empty](https://github.com/Manishearth/rust-clippy/wiki#len_without_is_empty)                         | warn    | traits and impls that have `.len()` but not `.is_empty()`
  85 [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
  86 [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
  87 [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
  88 [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
  89 [logic_bug](https://github.com/Manishearth/rust-clippy/wiki#logic_bug)                                               | warn    | checks for boolean expressions that contain terminals which can be eliminated
  90 [manual_swap](https://github.com/Manishearth/rust-clippy/wiki#manual_swap)                                           | warn    | manual swap
  91 [many_single_char_names](https://github.com/Manishearth/rust-clippy/wiki#many_single_char_names)                     | warn    | too many single character bindings
  92 [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 (recommends `.cloned()` instead)
  93 [map_entry](https://github.com/Manishearth/rust-clippy/wiki#map_entry)                                               | warn    | use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`
  94 [match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool)                                             | warn    | a match on boolean expression; recommends `if..else` block instead
  95 [match_overlapping_arm](https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm)                       | warn    | a match has overlapping arms
  96 [match_ref_pats](https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats)                                     | warn    | a match or `if let` has all arms prefixed with `&`; the match expression can be dereferenced instead
  97 [match_same_arms](https://github.com/Manishearth/rust-clippy/wiki#match_same_arms)                                   | warn    | `match` with identical arm bodies
  98 [mem_forget](https://github.com/Manishearth/rust-clippy/wiki#mem_forget)                                             | allow   | `mem::forget` usage on `Drop` types is likely to cause memory leaks
  99 [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
 100 [modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one)                                             | warn    | taking a number modulo 1, which always returns 0
 101 [mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut)                                                   | allow   | usage of double-mut refs, e.g. `&mut &mut ...` (either copy'n'paste error, or shows a fundamental misunderstanding of references)
 102 [mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic)                                         | warn    | using a Mutex where an atomic value could be used instead
 103 [mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer)                                       | allow   | using a Mutex for an integer type
 104 [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 }`
 105 [needless_borrow](https://github.com/Manishearth/rust-clippy/wiki#needless_borrow)                                   | warn    | taking a reference that is going to be automatically dereferenced
 106 [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
 107 [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
 108 [needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return)                                   | warn    | using a return statement like `return expr;` where an expression would suffice
 109 [needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update)                                   | warn    | using `{ ..base }` when there are no missing fields
 110 [neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply)                                         | warn    | Warns on multiplying integers with -1
 111 [new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self)                                   | warn    | not returning `Self` in a `new` method
 112 [new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default)                           | warn    | `fn new() -> Self` method without `Default` implementation
 113 [new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive)             | warn    | `fn new() -> Self` without `#[derive]`able `Default` implementation
 114 [no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect)                                               | warn    | statements with no effect
 115 [non_ascii_literal](https://github.com/Manishearth/rust-clippy/wiki#non_ascii_literal)                               | allow   | using any literal non-ASCII chars in a string literal; suggests using the \\u escape instead
 116 [nonminimal_bool](https://github.com/Manishearth/rust-clippy/wiki#nonminimal_bool)                                   | allow   | checks for boolean expressions that can be written more concisely
 117 [nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options)                 | warn    | nonsensical combination of options for opening a file
 118 [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`
 119 [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
 120 [option_map_unwrap_or](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or)                         | warn    | using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`
 121 [option_map_unwrap_or_else](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or_else)               | warn    | using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`
 122 [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()`
 123 [or_fun_call](https://github.com/Manishearth/rust-clippy/wiki#or_fun_call)                                           | warn    | using any `*or` method when the `*or_else` would do
 124 [out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing)                     | deny    | out of bound constant indexing
 125 [overflow_check_conditional](https://github.com/Manishearth/rust-clippy/wiki#overflow_check_conditional)             | warn    | Using overflow checks which are likely to panic
 126 [panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params)                                         | warn    | missing parameters in `panic!`
 127 [precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence)                                             | warn    | catches operations where precedence may be unclear. See the wiki for a list of cases caught
 128 [print_stdout](https://github.com/Manishearth/rust-clippy/wiki#print_stdout)                                         | allow   | printing on stdout
 129 [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
 130 [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
 131 [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
 132 [redundant_closure](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure)                               | warn    | using redundant closures, i.e. `|a| foo(a)` (which can be written as just `foo`)
 133 [redundant_closure_call](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure_call)                     | warn    | Closures should not be called in the expression they are defined
 134 [redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern)                               | warn    | using `name @ _` in a pattern
 135 [regex_macro](https://github.com/Manishearth/rust-clippy/wiki#regex_macro)                                           | warn    | finds use of `regex!(_)`, suggests `Regex::new(_)` instead
 136 [result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used)                             | allow   | using `Result.unwrap()`, which might be better handled
 137 [reverse_range_loop](https://github.com/Manishearth/rust-clippy/wiki#reverse_range_loop)                             | warn    | Iterating over an empty range, such as `10..0` or `5..5`
 138 [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()`
 139 [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`
 140 [shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same)                                           | allow   | rebinding a name to itself, e.g. `let mut x = &mut x`
 141 [shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated)                                 | allow   | The name is re-bound without even using the original value
 142 [should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait)                     | warn    | defining a method that should be implementing a std trait
 143 [similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names)                                       | allow   | similarly named items and bindings
 144 [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")`
 145 [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 `_ => {}`) is used; recommends `if let` instead
 146 [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; recommends `if let` instead
 147 [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add)                                             | allow   | using `x + ..` where x is a `String`; suggests using `push_str()` instead
 148 [string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign)                               | allow   | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
 149 [string_lit_as_bytes](https://github.com/Manishearth/rust-clippy/wiki#string_lit_as_bytes)                           | warn    | calling `as_bytes` on a string literal; suggests using a byte string literal instead
 150 [stutter](https://github.com/Manishearth/rust-clippy/wiki#stutter)                                                   | allow   | finds type names prefixed/postfixed with their containing module's name
 151 [suspicious_assignment_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_assignment_formatting) | warn    | suspicious formatting of `*=`, `-=` or `!=`
 152 [suspicious_else_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_else_formatting)             | warn    | suspicious formatting of `else if`
 153 [temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment)                         | warn    | assignments to temporaries
 154 [temporary_cstring_as_ptr](https://github.com/Manishearth/rust-clippy/wiki#temporary_cstring_as_ptr)                 | warn    | getting the inner pointer of a temporary `CString`
 155 [too_many_arguments](https://github.com/Manishearth/rust-clippy/wiki#too_many_arguments)                             | warn    | functions with too many arguments
 156 [toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg)                                 | warn    | An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take references with `&`.
 157 [transmute_ptr_to_ref](https://github.com/Manishearth/rust-clippy/wiki#transmute_ptr_to_ref)                         | warn    | transmutes from a pointer to a reference type
 158 [trivial_regex](https://github.com/Manishearth/rust-clippy/wiki#trivial_regex)                                       | warn    | finds trivial regular expressions
 159 [type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity)                                   | warn    | usage of very complex types; recommends factoring out parts into `type` definitions
 160 [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)
 161 [unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp)                                                 | warn    | comparing unit values (which is always `true` or `false`, respectively)
 162 [unnecessary_mut_passed](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_mut_passed)                     | warn    | an argument is passed as a mutable reference although the function/method only demands an immutable reference
 163 [unnecessary_operation](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_operation)                       | warn    | outer expressions with no effect
 164 [unneeded_field_pattern](https://github.com/Manishearth/rust-clippy/wiki#unneeded_field_pattern)                     | warn    | Struct fields are bound to a wildcard instead of using `..`
 165 [unsafe_removed_from_name](https://github.com/Manishearth/rust-clippy/wiki#unsafe_removed_from_name)                 | warn    | unsafe removed from name
 166 [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
 167 [unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label)                                         | warn    | unused label
 168 [unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes)                                 | warn    | unused lifetimes in function definitions
 169 [use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug)                                               | allow   | use `Debug`-based formatting
 170 [used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding)                   | allow   | using a binding which is prefixed with an underscore
 171 [useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format)                                     | warn    | useless use of `format!`
 172 [useless_let_if_seq](https://github.com/Manishearth/rust-clippy/wiki#useless_let_if_seq)                             | warn    | Checks for unidiomatic `let mut` declaration followed by initialization in `if`
 173 [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
 174 [useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec)                                           | warn    | useless `vec!`
 175 [while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop)                                     | warn    | `loop { if let { ... } else break }` can be written as a `while let` loop
 176 [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
 177 [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
 178 [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
 179 [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
 180 [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
 181 [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
 182
 183 More to come, please [file an issue](https://github.com/Manishearth/rust-clippy/issues) if you have ideas!
 184
 185 ## Usage
 186
 187 As a general rule clippy will only work with the *latest* Rust nightly for now.
 188
 189 ### As a Compiler Plugin
 190
 191 Since stable Rust is backwards compatible, you should be able to
 192 compile your stable programs with nightly Rust with clippy plugged in to
 193 circumvent this.
 194
 195 Add in your `Cargo.toml`:
 196
 197 ```toml
 198 [dependencies]
 199 clippy = "*"
 200 ```
 201
 202 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
 203 of your crate entry point (`main.rs` or `lib.rs`).
 204
 205 Sample `main.rs`:
 206
 207 ```rust
 208 #![feature(plugin)]
 209
 210 #![plugin(clippy)]
 211
 212
 213 fn main(){
 214     let x = Some(1u8);
 215     match x {
 216         Some(y) => println!("{:?}", y),
 217         _ => ()
 218     }
 219 }
 220 ```
 221
 222 Produces this warning:
 223
 224 ```terminal
 225 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
 226 src/main.rs:8     match x {
 227 src/main.rs:9         Some(y) => println!("{:?}", y),
 228 src/main.rs:10         _ => ()
 229 src/main.rs:11     }
 230 src/main.rs:8:5: 11:6 help: Try
 231 if let Some(y) = x { println!("{:?}", y) }
 232 ```
 233
 234 ### As a cargo subcommand (`cargo clippy`)
 235
 236 An alternate way to use clippy is by installing clippy through cargo as a cargo
 237 subcommand.
 238
 239 ```terminal
 240 cargo install clippy
 241 ```
 242
 243 Now you can run clippy by invoking `cargo clippy`, or
 244 `multirust run nightly cargo clippy` directly from a directory that is usually
 245 compiled with stable.
 246
 247 In case you are not using multirust, you need to set the environment flag
 248 `SYSROOT` during installation so clippy knows where to find `librustc` and
 249 similar crates.
 250
 251 ```terminal
 252 SYSROOT=/path/to/rustc/sysroot cargo install clippy
 253 ```
 254
 255 ### Running clippy from the command line without installing
 256
 257 To have cargo compile your crate with clippy without needing `#![plugin(clippy)]`
 258 in your code, you can use:
 259
 260 ```terminal
 261 cargo rustc -- -L /path/to/clippy_so -Z extra-plugins=clippy
 262 ```
 263
 264 *[Note](https://github.com/Manishearth/rust-clippy/wiki#a-word-of-warning):*
 265 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
 266
 267 ### Optional dependency
 268
 269 If you want to make clippy an optional dependency, you can do the following:
 270
 271 In your `Cargo.toml`:
 272
 273 ```toml
 274 [dependencies]
 275 clippy = {version = "*", optional = true}
 276
 277 [features]
 278 default = []
 279 ```
 280
 281 And, in your `main.rs` or `lib.rs`:
 282
 283 ```rust
 284 #![cfg_attr(feature="clippy", feature(plugin))]
 285
 286 #![cfg_attr(feature="clippy", plugin(clippy))]
 287 ```
 288
 289 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
 290 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
 291 (the `-Z no trans`, while not neccessary, will stop the compilation process after
 292 typechecking (and lints) have completed, which can significantly reduce the runtime).
 293
 294 ## Configuration
 295
 296 Some lints can be configured in a `clippy.toml` file. It contains basic `variable = value` mapping eg.
 297
 298 ```toml
 299 blacklisted-names = ["toto", "tata", "titi"]
 300 cyclomatic-complexity-threshold = 30
 301 ```
 302
 303 See the wiki for more information about which lints can be configured and the
 304 meaning of the variables.
 305
 306 You can also specify the path to the configuration file with:
 307
 308 ```rust
 309 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
 310 ```
 311
 312 To deactivate the “for further information visit *wiki-link*” message you can
 313 define the `CLIPPY_DISABLE_WIKI_LINKS` environment variable.
 314
 315 ### Allowing/denying lints
 316
 317 You can add options  to `allow`/`warn`/`deny`:
 318
 319 *   the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
 320
 321 *   all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
 322     `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
 323     lints prone to false positives.
 324
 325 *   only some lints (`#![deny(single_match, box_vec)]`, etc)
 326
 327 *   `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
 328
 329 Note: `deny` produces errors instead of warnings.
 330
 331 ## Link with clippy service
 332
 333 `clippy-service` is a rust web initiative providing `rust-clippy` as a web service.
 334
 335 Both projects are independent and maintained by different people
 336 (even if some `clippy-service`'s contributions are authored by some `rust-clippy` members).
 337
 338 You can check out this great service at [clippy.bashy.io](https://clippy.bashy.io/).
 339
 340 ## License
 341
 342 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
 343 If you're having issues with the license, let me know and I'll try to change it to something more permissive.