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 153 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 [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
  53 [duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument)       | warn    | Function arguments having names which only differ by an underscore
  54 [empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop)                                             | warn    | empty `loop {}` detected
  55 [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`
  56 [enum_glob_use](https://github.com/Manishearth/rust-clippy/wiki#enum_glob_use)                                       | allow   | finds use items that import all variants of an enum
  57 [enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#enum_variant_names)                             | warn    | finds enums where all variants share a prefix/postfix
  58 [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`)
  59 [expl_impl_clone_on_copy](https://github.com/Manishearth/rust-clippy/wiki#expl_impl_clone_on_copy)                   | warn    | implementing `Clone` explicitly on `Copy` types
  60 [explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop)                       | warn    | for-looping with an explicit counter when `_.enumerate()` would do
  61 [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
  62 [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
  63 [filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next)                                           | warn    | using `filter(p).next()`, which is more succinctly expressed as `.find(p)`
  64 [float_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#float_arithmetic)                                 | allow   | Any floating-point arithmetic statement
  65 [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)
  66 [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
  67 [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`
  68 [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`
  69 [identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op)                                           | warn    | using identity operations, e.g. `x + 0` or `y / 1`
  70 [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
  71 [if_same_then_else](https://github.com/Manishearth/rust-clippy/wiki#if_same_then_else)                               | warn    | if with the same *then* and *else* blocks
  72 [ifs_same_cond](https://github.com/Manishearth/rust-clippy/wiki#ifs_same_cond)                                       | warn    | consecutive `ifs` with the same condition
  73 [indexing_slicing](https://github.com/Manishearth/rust-clippy/wiki#indexing_slicing)                                 | allow   | indexing/slicing usage
  74 [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`
  75 [inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always)                                       | warn    | `#[inline(always)]` is a bad idea in most cases
  76 [integer_arithmetic](https://github.com/Manishearth/rust-clippy/wiki#integer_arithmetic)                             | allow   | Any integer arithmetic statement
  77 [invalid_regex](https://github.com/Manishearth/rust-clippy/wiki#invalid_regex)                                       | deny    | finds invalid regular expressions
  78 [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
  79 [items_after_statements](https://github.com/Manishearth/rust-clippy/wiki#items_after_statements)                     | allow   | finds blocks where an item comes after a statement
  80 [iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop)                                     | warn    | for-looping over `_.next()` which is probably not intended
  81 [iter_nth](https://github.com/Manishearth/rust-clippy/wiki#iter_nth)                                                 | warn    | using `.iter().nth()` on a slice or Vec
  82 [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()`
  83 [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
  84 [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
  85 [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
  86 [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
  87 [logic_bug](https://github.com/Manishearth/rust-clippy/wiki#logic_bug)                                               | warn    | checks for boolean expressions that contain terminals which can be eliminated
  88 [manual_swap](https://github.com/Manishearth/rust-clippy/wiki#manual_swap)                                           | warn    | manual swap
  89 [many_single_char_names](https://github.com/Manishearth/rust-clippy/wiki#many_single_char_names)                     | warn    | too many single character bindings
  90 [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)
  91 [map_entry](https://github.com/Manishearth/rust-clippy/wiki#map_entry)                                               | warn    | use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`
  92 [match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool)                                             | warn    | a match on boolean expression; recommends `if..else` block instead
  93 [match_overlapping_arm](https://github.com/Manishearth/rust-clippy/wiki#match_overlapping_arm)                       | warn    | a match has overlapping arms
  94 [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
  95 [match_same_arms](https://github.com/Manishearth/rust-clippy/wiki#match_same_arms)                                   | warn    | `match` with identical arm bodies
  96 [mem_forget](https://github.com/Manishearth/rust-clippy/wiki#mem_forget)                                             | allow   | `mem::forget` usage on `Drop` types is likely to cause memory leaks
  97 [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
  98 [modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one)                                             | warn    | taking a number modulo 1, which always returns 0
  99 [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)
 100 [mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic)                                         | warn    | using a Mutex where an atomic value could be used instead
 101 [mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer)                                       | allow   | using a Mutex for an integer type
 102 [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 }`
 103 [needless_borrow](https://github.com/Manishearth/rust-clippy/wiki#needless_borrow)                                   | warn    | taking a reference that is going to be automatically dereferenced
 104 [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
 105 [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
 106 [needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return)                                   | warn    | using a return statement like `return expr;` where an expression would suffice
 107 [needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update)                                   | warn    | using `{ ..base }` when there are no missing fields
 108 [neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply)                                         | warn    | Warns on multiplying integers with -1
 109 [new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self)                                   | warn    | not returning `Self` in a `new` method
 110 [new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default)                           | warn    | `fn new() -> Self` method without `Default` implementation
 111 [new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive)             | warn    | `fn new() -> Self` without `#[derive]`able `Default` implementation
 112 [no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect)                                               | warn    | statements with no effect
 113 [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
 114 [nonminimal_bool](https://github.com/Manishearth/rust-clippy/wiki#nonminimal_bool)                                   | allow   | checks for boolean expressions that can be written more concisely
 115 [nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options)                 | warn    | nonsensical combination of options for opening a file
 116 [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
 117 [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)`
 118 [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)`
 119 [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()`
 120 [or_fun_call](https://github.com/Manishearth/rust-clippy/wiki#or_fun_call)                                           | warn    | using any `*or` method when the `*or_else` would do
 121 [out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing)                     | deny    | out of bound constant indexing
 122 [overflow_check_conditional](https://github.com/Manishearth/rust-clippy/wiki#overflow_check_conditional)             | warn    | Using overflow checks which are likely to panic
 123 [panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params)                                         | warn    | missing parameters in `panic!`
 124 [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
 125 [print_stdout](https://github.com/Manishearth/rust-clippy/wiki#print_stdout)                                         | allow   | printing on stdout
 126 [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
 127 [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
 128 [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
 129 [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`)
 130 [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
 131 [redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern)                               | warn    | using `name @ _` in a pattern
 132 [regex_macro](https://github.com/Manishearth/rust-clippy/wiki#regex_macro)                                           | warn    | finds use of `regex!(_)`, suggests `Regex::new(_)` instead
 133 [result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used)                             | allow   | using `Result.unwrap()`, which might be better handled
 134 [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`
 135 [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()`
 136 [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`
 137 [shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same)                                           | allow   | rebinding a name to itself, e.g. `let mut x = &mut x`
 138 [shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated)                                 | allow   | The name is re-bound without even using the original value
 139 [should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait)                     | warn    | defining a method that should be implementing a std trait
 140 [similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names)                                       | allow   | similarly named items and bindings
 141 [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")`
 142 [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
 143 [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
 144 [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add)                                             | allow   | using `x + ..` where x is a `String`; suggests using `push_str()` instead
 145 [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
 146 [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
 147 [suspicious_assignment_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_assignment_formatting) | warn    | suspicious formatting of `*=`, `-=` or `!=`
 148 [suspicious_else_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_else_formatting)             | warn    | suspicious formatting of `else if`
 149 [temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment)                         | warn    | assignments to temporaries
 150 [temporary_cstring_as_ptr](https://github.com/Manishearth/rust-clippy/wiki#temporary_cstring_as_ptr)                 | warn    | getting the inner pointer of a temporary `CString`
 151 [too_many_arguments](https://github.com/Manishearth/rust-clippy/wiki#too_many_arguments)                             | warn    | functions with too many arguments
 152 [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 `&`.
 153 [transmute_ptr_to_ref](https://github.com/Manishearth/rust-clippy/wiki#transmute_ptr_to_ref)                         | warn    | transmutes from a pointer to a reference type
 154 [trivial_regex](https://github.com/Manishearth/rust-clippy/wiki#trivial_regex)                                       | warn    | finds trivial regular expressions
 155 [type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity)                                   | warn    | usage of very complex types; recommends factoring out parts into `type` definitions
 156 [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)
 157 [unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp)                                                 | warn    | comparing unit values (which is always `true` or `false`, respectively)
 158 [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
 159 [unnecessary_operation](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_operation)                       | warn    | outer expressions with no effect
 160 [unneeded_field_pattern](https://github.com/Manishearth/rust-clippy/wiki#unneeded_field_pattern)                     | warn    | Struct fields are bound to a wildcard instead of using `..`
 161 [unsafe_removed_from_name](https://github.com/Manishearth/rust-clippy/wiki#unsafe_removed_from_name)                 | warn    | unsafe removed from name
 162 [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
 163 [unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label)                                         | warn    | unused label
 164 [unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes)                                 | warn    | unused lifetimes in function definitions
 165 [use_debug](https://github.com/Manishearth/rust-clippy/wiki#use_debug)                                               | allow   | use `Debug`-based formatting
 166 [used_underscore_binding](https://github.com/Manishearth/rust-clippy/wiki#used_underscore_binding)                   | allow   | using a binding which is prefixed with an underscore
 167 [useless_format](https://github.com/Manishearth/rust-clippy/wiki#useless_format)                                     | warn    | useless use of `format!`
 168 [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`
 169 [useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute)                               | warn    | transmutes that have the same to and from types
 170 [useless_vec](https://github.com/Manishearth/rust-clippy/wiki#useless_vec)                                           | warn    | useless `vec!`
 171 [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
 172 [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
 173 [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
 174 [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
 175 [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
 176 [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
 177
 178 More to come, please [file an issue](https://github.com/Manishearth/rust-clippy/issues) if you have ideas!
 179
 180 ## Usage
 181
 182 ### As a Compiler Plugin
 183
 184 Compiler plugins are highly unstable and will only work with a *recent* nightly
 185 Rust for now.  Since stable Rust is backwards compatible, you should be able to
 186 compile your stable programs with nightly Rust with clippy plugged in to
 187 circumvent this.
 188
 189 Add in your `Cargo.toml`:
 190
 191 ```toml
 192 [dependencies]
 193 clippy = "*"
 194 ```
 195
 196 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
 197 of your crate entry point (`main.rs` or `lib.rs`).
 198
 199 Sample `main.rs`:
 200
 201 ```rust
 202 #![feature(plugin)]
 203
 204 #![plugin(clippy)]
 205
 206
 207 fn main(){
 208     let x = Some(1u8);
 209     match x {
 210         Some(y) => println!("{:?}", y),
 211         _ => ()
 212     }
 213 }
 214 ```
 215
 216 Produces this warning:
 217
 218 ```terminal
 219 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
 220 src/main.rs:8     match x {
 221 src/main.rs:9         Some(y) => println!("{:?}", y),
 222 src/main.rs:10         _ => ()
 223 src/main.rs:11     }
 224 src/main.rs:8:5: 11:6 help: Try
 225 if let Some(y) = x { println!("{:?}", y) }
 226 ```
 227
 228 ### As a cargo subcommand (`cargo clippy`)
 229
 230 An alternate way to use clippy is by installing clippy through cargo as a cargo
 231 subcommand.
 232
 233 ```terminal
 234 cargo install clippy
 235 ```
 236
 237 Now you can run clippy by invoking `cargo clippy`, or
 238 `multirust run nightly cargo clippy` directly from a directory that is usually
 239 compiled with stable.
 240
 241 In case you are not using multirust, you need to set the environment flag
 242 `SYSROOT` during installation so clippy knows where to find `librustc` and
 243 similar crates.
 244
 245 ```terminal
 246 SYSROOT=/path/to/rustc/sysroot cargo install clippy
 247 ```
 248
 249 ### Running clippy from the command line without installing
 250
 251 To have cargo compile your crate with clippy without needing `#![plugin(clippy)]`
 252 in your code, you can use:
 253
 254 ```terminal
 255 cargo rustc -- -L /path/to/clippy_so -Z extra-plugins=clippy
 256 ```
 257
 258 *[Note](https://github.com/Manishearth/rust-clippy/wiki#a-word-of-warning):*
 259 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
 260
 261 ### Optional dependency
 262
 263 If you want to make clippy an optional dependency, you can do the following:
 264
 265 In your `Cargo.toml`:
 266
 267 ```toml
 268 [dependencies]
 269 clippy = {version = "*", optional = true}
 270
 271 [features]
 272 default=[]
 273 ```
 274
 275 And, in your `main.rs` or `lib.rs`:
 276
 277 ```rust
 278 #![cfg_attr(feature="clippy", feature(plugin))]
 279
 280 #![cfg_attr(feature="clippy", plugin(clippy))]
 281 ```
 282
 283 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
 284 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
 285 (the `-Z no trans`, while not neccessary, will stop the compilation process after
 286 typechecking (and lints) have completed, which can significantly reduce the runtime).
 287
 288 ## Configuration
 289
 290 Some lints can be configured in a `clippy.toml` file. It contains basic `variable = value` mapping eg.
 291
 292 ```toml
 293 blacklisted-names = ["toto", "tata", "titi"]
 294 cyclomatic-complexity-threshold = 30
 295 ```
 296
 297 See the wiki for more information about which lints can be configured and the
 298 meaning of the variables.
 299
 300 You can also specify the path to the configuration file with:
 301
 302 ```rust
 303 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
 304 ```
 305
 306 To deactivate the “for further information visit *wiki-link*” message you can
 307 define the `CLIPPY_DISABLE_WIKI_LINKS` environment variable.
 308
 309 ### Allowing/denying lints
 310
 311 You can add options  to `allow`/`warn`/`deny`:
 312
 313 *   the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
 314
 315 *   all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
 316     `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
 317     lints prone to false positives.
 318
 319 *   only some lints (`#![deny(single_match, box_vec)]`, etc)
 320
 321 *   `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
 322
 323 Note: `deny` produces errors instead of warnings.
 324
 325 For convenience, `cargo clippy` automatically defines a `clippy` features. This
 326 lets you set lints level and compile with or without clippy transparently:
 327
 328 ```rust
 329 #[cfg_attr(feature = "clippy", allow(needless_lifetimes))]
 330 ```
 331
 332 ## Link with clippy service
 333
 334 `clippy-service` is a rust web initiative providing `rust-clippy` as a web service.
 335
 336 Both projects are independent and maintained by different people
 337 (even if some `clippy-service`'s contributions are authored by some `rust-clippy` members).
 338
 339 You can check out this great service at [clippy.bashy.io](https://clippy.bashy.io/).
 340
 341 ## License
 342
 343 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
 344 If you're having issues with the license, let me know and I'll try to change it to something more permissive.