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)
8 A collection of lints to catch common mistakes and improve your Rust code.
13 * [Usage instructions](#usage)
14 * [Configuration](#configuration)
15 * [*clippy-service*](#link-with-clippy-service)
20 There are 170 lints included in this crate:
22 name | default | triggers on
23 ---------------------------------------------------------------------------------------------------------------------|---------|----------------------------------------------------------------------------------------------------------------------------------
24 [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
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::fXX::consts`)
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 compound 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`
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 that can be eliminated in conditions, e.g `if { true } ...`
32 [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 } ...`
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 [builtin_type_shadow](https://github.com/Manishearth/rust-clippy/wiki#builtin_type_shadow) | warn | shadowing a builtin type
37 [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`
38 [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`
39 [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`
40 [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`
41 [char_lit_as_u8](https://github.com/Manishearth/rust-clippy/wiki#char_lit_as_u8) | warn | casting a character literal to u8
42 [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
43 [clone_double_ref](https://github.com/Manishearth/rust-clippy/wiki#clone_double_ref) | warn | using `clone` on `&&T`
44 [clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#clone_on_copy) | warn | using `clone` on a `Copy` type
45 [cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan) | deny | comparisons to NAN, which will always return false, probably not intended
46 [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.
47 [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()`
48 [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 { ... } }`)
49 [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
50 [cyclomatic_complexity](https://github.com/Manishearth/rust-clippy/wiki#cyclomatic_complexity) | warn | functions that should be split up into multiple functions
51 [deprecated_semver](https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver) | warn | use of `#[deprecated(since = "x")]` where x is not semver
52 [derive_hash_xor_eq](https://github.com/Manishearth/rust-clippy/wiki#derive_hash_xor_eq) | warn | deriving `Hash` but implementing `PartialEq` explicitly
53 [doc_markdown](https://github.com/Manishearth/rust-clippy/wiki#doc_markdown) | warn | presence of `_`, `::` or camel-case outside backticks in documentation
54 [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++
55 [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
56 [duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument) | warn | function arguments having names which only differ by an underscore
57 [empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop) | warn | empty `loop {}`, which should block or sleep
58 [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`
59 [enum_glob_use](https://github.com/Manishearth/rust-clippy/wiki#enum_glob_use) | allow | use items that import all variants of an enum
60 [enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#enum_variant_names) | warn | enums where all variants share a prefix/postfix
61 [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`)
62 [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
63 [expl_impl_clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#expl_impl_clone_on_copy) | warn | implementing `Clone` explicitly on `Copy` types
64 [explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop) | warn | for-looping with an explicit counter when `_.enumerate()` would do
65 [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
66 [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
67 [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
68 [filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next) | warn | using `filter(p).next()`, which is more succinctly expressed as `.find(p)`
69 [float_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#float_arithmetic) | allow | any floating-point arithmetic statement
70 [float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp) | warn | using `==` or `!=` on float values instead of comparing difference with an epsilon
71 [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
72 [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`
73 [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`
74 [identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op) | warn | using identity operations, e.g. `x + 0` or `y / 1`
75 [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
76 [if_same_then_else](https://github.com/Manishearth/rust-clippy/wiki#if_same_then_else) | warn | if with the same *then* and *else* blocks
77 [ifs_same_cond](https://github.com/Manishearth/rust-clippy/wiki#ifs_same_cond) | warn | consecutive `ifs` with the same condition
78 [indexing_slicing](https://github.com/Manishearth/rust-clippy/wiki#indexing_slicing) | allow | indexing/slicing usage
79 [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`
80 [inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always) | warn | use of `#[inline(always)]`
81 [integer_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#integer_arithmetic) | allow | any integer arithmetic statement
82 [invalid_regex](https://github.com/Manishearth/rust-clippy/wiki#invalid_regex) | deny | invalid regular expressions
83 [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
84 [items_after_statements](https://github.com/Manishearth/rust-clippy/wiki#items_after_statements) | allow | blocks where an item comes after a statement
85 [iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop) | warn | for-looping over `_.next()` which is probably not intended
86 [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
87 [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()`
88 [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
89 [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
90 [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
91 [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
92 [logic_bug](https://github.com/Manishearth/rust-clippy/wiki#logic_bug) | warn | boolean expressions that contain terminals which can be eliminated
93 [manual_swap](https://github.com/Manishearth/rust-clippy/wiki#manual_swap) | warn | manual swap of two variables
94 [many_single_char_names](https://github.com/Manishearth/rust-clippy/wiki#many_single_char_names) | warn | too many single character bindings
95 [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
96 [map_entry](https://github.com/Manishearth/rust-clippy/wiki#map_entry) | warn | use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`
97 [match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool) | warn | a match on a boolean expression instead of an `if..else` block
98 [match_overlapping_arm](https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm) | warn | a match with overlapping arms
99 [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
100 [match_same_arms](https://github.com/Manishearth/rust-clippy/wiki#match_same_arms) | warn | `match` with identical arm bodies
101 [mem_forget](https://github.com/Manishearth/rust-clippy/wiki#mem_forget) | allow | `mem::forget` usage on `Drop` types, likely to cause memory leaks
102 [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
103 [misrefactored_assign_op](https://github.com/Manishearth/rust-clippy/wiki#misrefactored_assign_op) | warn | having a variable on both sides of an assign op
104 [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
105 [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
106 [module_inception](https://github.com/Manishearth/rust-clippy/wiki#module_inception) | warn | modules that have the same name as their parent module
107 [modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one) | warn | taking a number modulo 1, which always returns 0
108 [mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut) | allow | usage of double-mut refs, e.g. `&mut &mut ...`
109 [mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic) | warn | using a mutex where an atomic value could be used instead
110 [mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer) | allow | using a mutex for an integer type
111 [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 }`
112 [needless_borrow](https://github.com/Manishearth/rust-clippy/wiki#needless_borrow) | warn | taking a reference that is going to be automatically dereferenced
113 [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
114 [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
115 [needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return) | warn | using a return statement like `return expr;` where an expression would suffice
116 [needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update) | warn | using `Foo { ..base }` when there are no missing fields
117 [neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply) | warn | multiplying integers with -1
118 [new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self) | warn | not returning `Self` in a `new` method
119 [new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default) | warn | `fn new() -> Self` method without `Default` implementation
120 [new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive) | warn | `fn new() -> Self` without `#[derive]`able `Default` implementation
121 [no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect) | warn | statements with no effect
122 [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
123 [nonminimal_bool](https://github.com/Manishearth/rust-clippy/wiki#nonminimal_bool) | allow | boolean expressions that can be written more concisely
124 [nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options) | warn | nonsensical combination of options for opening a file
125 [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`
126 [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
127 [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)`
128 [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)`
129 [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()`
130 [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`
131 [out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing) | deny | out of bounds constant indexing
132 [overflow_check_conditional](https://github.com/Manishearth/rust-clippy/wiki#overflow_check_conditional) | warn | overflow checks inspired by C which are likely to panic
133 [panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params) | warn | missing parameters in `panic!` calls
134 [precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence) | warn | operations where precedence may be unclear
135 [print_stdout](https://github.com/Manishearth/rust-clippy/wiki#print_stdout) | allow | printing on stdout
136 [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
137 [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
138 [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
139 [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
140 [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`)
141 [redundant_closure_call](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure_call) | warn | throwaway closures called in the expression they are defined
142 [redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern) | warn | using `name @ _` in a pattern
143 [regex_macro](https://github.com/Manishearth/rust-clippy/wiki#regex_macro) | warn | use of `regex!(_)` instead of `Regex::new(_)`
144 [result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used) | allow | using `Result.unwrap()`, which might be better handled
145 [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`
146 [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()`
147 [serde_api_misuse](https://github.com/Manishearth/rust-clippy/wiki#serde_api_misuse) | warn | various things that will negatively affect your serde experience
148 [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`
149 [shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x`
150 [shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | rebinding a name without even using the original value
151 [should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait
152 [similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names) | allow | similarly named items and bindings
153 [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")`
154 [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`
155 [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`
156 [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String` instead of `push_str()`
157 [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()`
158 [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
159 [stutter](https://github.com/Manishearth/rust-clippy/wiki#stutter) | allow | type names prefixed/postfixed with their containing module's name
160 [suspicious_assignment_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_assignment_formatting) | warn | suspicious formatting of `*=`, `-=` or `!=`
161 [suspicious_else_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_else_formatting) | warn | suspicious formatting of `else if`
162 [temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries
163 [temporary_cstring_as_ptr](https://github.com/Manishearth/rust-clippy/wiki#temporary_cstring_as_ptr) | warn | getting the inner pointer of a temporary `CString`
164 [too_many_arguments](https://github.com/Manishearth/rust-clippy/wiki#too_many_arguments) | warn | functions with too many arguments
165 [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
166 [transmute_ptr_to_ref](https://github.com/Manishearth/rust-clippy/wiki#transmute_ptr_to_ref) | warn | transmutes from a pointer to a reference type
167 [trivial_regex](https://github.com/Manishearth/rust-clippy/wiki#trivial_regex) | warn | trivial regular expressions
168 [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
169 [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)
170 [unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp) | warn | comparing unit values
171 [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
172 [unnecessary_operation](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_operation) | warn | outer expressions with no effect
173 [unneeded_field_pattern](https://github.com/Manishearth/rust-clippy/wiki#unneeded_field_pattern) | warn | struct fields bound to a wildcard instead of using `..`
174 [unsafe_removed_from_name](https://github.com/Manishearth/rust-clippy/wiki#unsafe_removed_from_name) | warn | `unsafe` removed from API names on import
175 [unseparated_literal_suffix](https://github.com/Manishearth/rust-clippy/wiki#unseparated_literal_suffix) | allow | literals whose suffix is not separated by an underscore
176 [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
177 [unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label) | warn | unused labels
178 [unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes) | warn | unused lifetimes in function definitions
179 [use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug) | allow | use of `Debug`-based formatting
180 [used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding) | allow | using a binding which is prefixed with an underscore
181 [useless_attribute](https://github.com/Manishearth/rust-clippy/wiki#useless_attribute) | warn | use of lint attributes on `extern crate` items
182 [useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format) | warn | useless use of `format!`
183 [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`
184 [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
185 [useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec) | warn | useless `vec!`
186 [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
187 [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
188 [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
189 [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
190 [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
191 [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
192 [zero_prefixed_literal](https://github.com/Manishearth/rust-clippy/wiki#zero_prefixed_literal) | warn | integer literals starting with `0`
193 [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
195 More to come, please [file an issue](https://github.com/Manishearth/rust-clippy/issues) if you have ideas!
199 As a general rule clippy will only work with the *latest* Rust nightly for now.
201 ### As a Compiler Plugin
203 Since stable Rust is backwards compatible, you should be able to
204 compile your stable programs with nightly Rust with clippy plugged in to
207 Add in your `Cargo.toml`:
214 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
215 of your crate entry point (`main.rs` or `lib.rs`).
228 Some(y) => println!("{:?}", y),
234 Produces this warning:
237 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
238 src/main.rs:8 match x {
239 src/main.rs:9 Some(y) => println!("{:?}", y),
240 src/main.rs:10 _ => ()
242 src/main.rs:8:5: 11:6 help: Try
243 if let Some(y) = x { println!("{:?}", y) }
246 ### As a cargo subcommand (`cargo clippy`)
248 An alternate way to use clippy is by installing clippy through cargo as a cargo
255 Now you can run clippy by invoking `cargo clippy`, or
256 `rustup run nightly cargo clippy` directly from a directory that is usually
257 compiled with stable.
259 In case you are not using rustup, you need to set the environment flag
260 `SYSROOT` during installation so clippy knows where to find `librustc` and
264 SYSROOT=/path/to/rustc/sysroot cargo install clippy
267 ### Running clippy from the command line without installing
269 To have cargo compile your crate with clippy without needing `#![plugin(clippy)]`
270 in your code, you can use:
273 cargo rustc -- -L /path/to/clippy_so -Z extra-plugins=clippy
276 *[Note](https://github.com/Manishearth/rust-clippy/wiki#a-word-of-warning):*
277 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
279 ### Optional dependency
281 If you want to make clippy an optional dependency, you can do the following:
283 In your `Cargo.toml`:
287 clippy = {version = "*", optional = true}
293 And, in your `main.rs` or `lib.rs`:
296 #![cfg_attr(feature="clippy", feature(plugin))]
298 #![cfg_attr(feature="clippy", plugin(clippy))]
301 Then build by enabling the feature: `cargo build --features "clippy"`
303 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
304 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
305 (the `-Z no trans`, while not neccessary, will stop the compilation process after
306 typechecking (and lints) have completed, which can significantly reduce the runtime).
310 Some lints can be configured in a `clippy.toml` file. It contains basic `variable = value` mapping eg.
313 blacklisted-names = ["toto", "tata", "titi"]
314 cyclomatic-complexity-threshold = 30
317 See the wiki for more information about which lints can be configured and the
318 meaning of the variables.
320 You can also specify the path to the configuration file with:
323 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
326 To deactivate the “for further information visit *wiki-link*” message you can
327 define the `CLIPPY_DISABLE_WIKI_LINKS` environment variable.
329 ### Allowing/denying lints
331 You can add options to `allow`/`warn`/`deny`:
333 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
335 * all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
336 `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
337 lints prone to false positives.
339 * only some lints (`#![deny(single_match, box_vec)]`, etc)
341 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
343 Note: `deny` produces errors instead of warnings.
345 ## Link with clippy service
347 `clippy-service` is a rust web initiative providing `rust-clippy` as a web service.
349 Both projects are independent and maintained by different people
350 (even if some `clippy-service`'s contributions are authored by some `rust-clippy` members).
352 You can check out this great service at [clippy.bashy.io](https://clippy.bashy.io/).
356 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
357 If you're having issues with the license, let me know and I'll try to change it to something more permissive.