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clippy_lints | ||
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util | ||
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Cargo.toml | ||
CHANGELOG.md | ||
CONTRIBUTING.md | ||
README.md | ||
rustfmt.toml |
rust-clippy
A collection of lints to catch common mistakes and improve your Rust code.
Table of contents:
Lints
There are 152 lints included in this crate:
name | default | meaning |
---|---|---|
absurd_extreme_comparisons | warn | a comparison involving a maximum or minimum value involves a case that is always true or always false |
almost_swapped | warn | foo = bar; bar = foo sequence |
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 |
assign_op_pattern | warn | assigning the result of an operation on a variable to that same variable |
assign_ops | allow | Any assignment operation |
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) |
blacklisted_name | warn | usage of a blacklisted/placeholder name |
block_in_if_condition_expr | warn | braces can be eliminated in conditions that are expressions, e.g if { true } ... |
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 } ... |
bool_comparison | warn | comparing a variable to a boolean, e.g. if x == true |
box_vec | warn | usage of Box<Vec<T>> , vector elements are already on the heap |
boxed_local | warn | using Box<T> where unnecessary |
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 |
cast_possible_wrap | allow | casts that may cause wrapping around the value, e.g x as i32 where x: u32 and x > i32::MAX |
cast_precision_loss | allow | casts that cause loss of precision, e.g x as f32 where x: u64 |
cast_sign_loss | allow | casts from signed types to unsigned types, e.g x as u32 where x: i32 |
char_lit_as_u8 | warn | Casting a character literal to u8 |
chars_next_cmp | warn | using .chars().next() to check if a string starts with a char |
clone_double_ref | warn | using clone on &&T |
clone_on_copy | warn | using clone on a Copy type |
cmp_nan | deny | comparisons to NAN (which will always return false, which is probably not intended) |
cmp_owned | warn | creating owned instances for comparing with others, e.g. x == "foo".to_string() |
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` |
crosspointer_transmute | warn | transmutes that have to or from types that are a pointer to the other |
cyclomatic_complexity | warn | finds functions that should be split up into multiple functions |
deprecated_semver | warn | Warn on #[deprecated(since = "x")] where x is not semver |
derive_hash_xor_eq | warn | deriving Hash but implementing PartialEq explicitly |
doc_markdown | warn | checks for the presence of _ , :: or camel-case outside ticks in documentation |
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 |
duplicate_underscore_argument | warn | Function arguments having names which only differ by an underscore |
empty_loop | warn | empty loop {} detected |
enum_clike_unportable_variant | warn | finds C-like enums that are repr(isize/usize) and have values that don't fit into an i32 |
enum_glob_use | allow | finds use items that import all variants of an enum |
enum_variant_names | warn | finds enums where all variants share a prefix/postfix |
eq_op | warn | equal operands on both sides of a comparison or bitwise combination (e.g. x == x ) |
expl_impl_clone_on_copy | warn | implementing Clone explicitly on Copy types |
explicit_counter_loop | warn | for-looping with an explicit counter when _.enumerate() would do |
explicit_iter_loop | warn | for-looping over _.iter() or _.iter_mut() when &_ or &mut _ would do |
extend_from_slice | warn | .extend_from_slice(_) is a faster way to extend a Vec by a slice |
filter_next | warn | using filter(p).next() , which is more succinctly expressed as .find(p) |
float_arithmetic | allow | Any floating-point arithmetic statement |
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) |
for_kv_map | warn | looping on a map using iter when keys or values would do |
for_loop_over_option | warn | for-looping over an Option , which is more clearly expressed as an if let |
for_loop_over_result | warn | for-looping over a Result , which is more clearly expressed as an if let |
identity_op | warn | using identity operations, e.g. x + 0 or y / 1 |
if_not_else | allow | finds if branches that could be swapped so no negation operation is necessary on the condition |
if_same_then_else | warn | if with the same then and else blocks |
ifs_same_cond | warn | consecutive ifs with the same condition |
indexing_slicing | allow | indexing/slicing usage |
ineffective_bit_mask | warn | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x |
inline_always | warn | #[inline(always)] is a bad idea in most cases |
integer_arithmetic | allow | Any integer arithmetic statement |
invalid_regex | deny | finds invalid regular expressions |
invalid_upcast_comparisons | allow | a comparison involving an upcast which is always true or false |
items_after_statements | allow | finds blocks where an item comes after a statement |
iter_next_loop | warn | for-looping over _.next() which is probably not intended |
len_without_is_empty | warn | traits and impls that have .len() but not .is_empty() |
len_zero | warn | checking .len() == 0 or .len() > 0 (or similar) when .is_empty() could be used instead |
let_and_return | warn | creating a let-binding and then immediately returning it like let x = expr; x at the end of a block |
let_unit_value | warn | creating a let binding to a value of unit type, which usually can't be used afterwards |
linkedlist | warn | usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque |
logic_bug | warn | checks for boolean expressions that contain terminals which can be eliminated |
manual_swap | warn | manual swap |
many_single_char_names | warn | too many single character bindings |
map_clone | warn | using `.map( |
map_entry | warn | use of contains_key followed by insert on a HashMap or BTreeMap |
match_bool | warn | a match on boolean expression; recommends if..else block instead |
match_overlapping_arm | warn | a match has overlapping arms |
match_ref_pats | warn | a match or if let has all arms prefixed with & ; the match expression can be dereferenced instead |
match_same_arms | warn | match with identical arm bodies |
mem_forget | allow | mem::forget usage on Drop types is likely to cause memory leaks |
min_max | warn | min(_, max(_, _)) (or vice versa) with bounds clamping the result to a constant |
modulo_one | warn | taking a number modulo 1, which always returns 0 |
mut_mut | allow | usage of double-mut refs, e.g. &mut &mut ... (either copy'n'paste error, or shows a fundamental misunderstanding of references) |
mutex_atomic | warn | using a Mutex where an atomic value could be used instead |
mutex_integer | allow | using a Mutex for an integer type |
needless_bool | warn | if-statements with plain booleans in the then- and else-clause, e.g. if p { true } else { false } |
needless_borrow | warn | taking a reference that is going to be automatically dereferenced |
needless_lifetimes | warn | using explicit lifetimes for references in function arguments when elision rules would allow omitting them |
needless_range_loop | warn | for-looping over a range of indices where an iterator over items would do |
needless_return | warn | using a return statement like return expr; where an expression would suffice |
needless_update | warn | using { ..base } when there are no missing fields |
neg_multiply | warn | Warns on multiplying integers with -1 |
new_ret_no_self | warn | not returning Self in a new method |
new_without_default | warn | fn new() -> Self method without Default implementation |
new_without_default_derive | warn | fn new() -> Self without #[derive] able Default implementation |
no_effect | warn | statements with no effect |
non_ascii_literal | allow | using any literal non-ASCII chars in a string literal; suggests using the \u escape instead |
nonminimal_bool | allow | checks for boolean expressions that can be written more concisely |
nonsensical_open_options | warn | nonsensical combination of options for opening a file |
ok_expect | warn | using ok().expect() , which gives worse error messages than calling expect directly on the Result |
option_map_unwrap_or | warn | using Option.map(f).unwrap_or(a) , which is more succinctly expressed as map_or(a, f) |
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) |
option_unwrap_used | allow | using Option.unwrap() , which should at least get a better message using expect() |
or_fun_call | warn | using any *or method when the *or_else would do |
out_of_bounds_indexing | deny | out of bound constant indexing |
overflow_check_conditional | warn | Using overflow checks which are likely to panic |
panic_params | warn | missing parameters in panic! |
precedence | warn | catches operations where precedence may be unclear. See the wiki for a list of cases caught |
print_stdout | allow | printing on stdout |
ptr_arg | warn | fn arguments of the type &Vec<...> or &String , suggesting to use &[...] or &str instead, respectively |
range_step_by_zero | warn | using Range::step_by(0), which produces an infinite iterator |
range_zip_with_len | warn | zipping iterator with a range when enumerate() would do |
redundant_closure | warn | using redundant closures, i.e. ` |
redundant_closure_call | warn | Closures should not be called in the expression they are defined |
redundant_pattern | warn | using name @ _ in a pattern |
regex_macro | warn | finds use of regex!(_) , suggests Regex::new(_) instead |
result_unwrap_used | allow | using Result.unwrap() , which might be better handled |
reverse_range_loop | warn | Iterating over an empty range, such as 10..0 or 5..5 |
search_is_some | warn | using an iterator search followed by is_some() , which is more succinctly expressed as a call to any() |
shadow_reuse | allow | rebinding a name to an expression that re-uses the original value, e.g. let x = x + 1 |
shadow_same | allow | rebinding a name to itself, e.g. let mut x = &mut x |
shadow_unrelated | allow | The name is re-bound without even using the original value |
should_implement_trait | warn | defining a method that should be implementing a std trait |
similar_names | allow | similarly named items and bindings |
single_char_pattern | warn | using a single-character str where a char could be used, e.g. _.split("x") |
single_match | warn | a match statement with a single nontrivial arm (i.e, where the other arm is _ => {} ) is used; recommends if let instead |
single_match_else | allow | a match statement with a two arms where the second arm's pattern is a wildcard; recommends if let instead |
string_add | allow | using x + .. where x is a String ; suggests using push_str() instead |
string_add_assign | allow | using x = x + .. where x is a String ; suggests using push_str() instead |
string_lit_as_bytes | warn | calling as_bytes on a string literal; suggests using a byte string literal instead |
suspicious_assignment_formatting | warn | suspicious formatting of *= , -= or != |
suspicious_else_formatting | warn | suspicious formatting of else if |
temporary_assignment | warn | assignments to temporaries |
temporary_cstring_as_ptr | warn | getting the inner pointer of a temporary CString |
too_many_arguments | warn | functions with too many arguments |
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 & . |
transmute_ptr_to_ref | warn | transmutes from a pointer to a reference type |
trivial_regex | warn | finds trivial regular expressions |
type_complexity | warn | usage of very complex types; recommends factoring out parts into type definitions |
unicode_not_nfc | allow | using a unicode literal not in NFC normal form (see unicode tr15 for further information) |
unit_cmp | warn | comparing unit values (which is always true or false , respectively) |
unnecessary_mut_passed | warn | an argument is passed as a mutable reference although the function/method only demands an immutable reference |
unnecessary_operation | warn | outer expressions with no effect |
unneeded_field_pattern | warn | Struct fields are bound to a wildcard instead of using .. |
unsafe_removed_from_name | warn | unsafe removed from name |
unused_collect | warn | collect() ing an iterator without using the result; this is usually better written as a for loop |
unused_label | warn | unused label |
unused_lifetimes | warn | unused lifetimes in function definitions |
use_debug | allow | use Debug -based formatting |
used_underscore_binding | allow | using a binding which is prefixed with an underscore |
useless_format | warn | useless use of format! |
useless_let_if_seq | warn | Checks for unidiomatic let mut declaration followed by initialization in if |
useless_transmute | warn | transmutes that have the same to and from types |
useless_vec | warn | useless vec! |
while_let_loop | warn | loop { if let { ... } else break } can be written as a while let loop |
while_let_on_iterator | warn | using a while-let loop instead of a for loop on an iterator |
wrong_pub_self_convention | allow | defining a public method named with an established prefix (like "into_") that takes self with the wrong convention |
wrong_self_convention | warn | defining a method named with an established prefix (like "into_") that takes self with the wrong convention |
zero_divided_by_zero | warn | usage of 0.0 / 0.0 to obtain NaN instead of std::f32::NaN or std::f64::NaN |
zero_width_space | deny | using a zero-width space in a string literal, which is confusing |
More to come, please file an issue if you have ideas!
Usage
As a Compiler Plugin
Compiler plugins are highly unstable and will only work with a nightly Rust for now. Since stable Rust is backwards compatible, you should be able to compile your stable programs with nightly Rust with clippy plugged in to circumvent this.
Add in your Cargo.toml
:
[dependencies]
clippy = "*"
You then need to add #![feature(plugin)]
and #![plugin(clippy)]
to the top
of your crate entry point (main.rs
or lib.rs
).
Sample main.rs
:
#![feature(plugin)]
#![plugin(clippy)]
fn main(){
let x = Some(1u8);
match x {
Some(y) => println!("{:?}", y),
_ => ()
}
}
Produces this warning:
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
src/main.rs:8 match x {
src/main.rs:9 Some(y) => println!("{:?}", y),
src/main.rs:10 _ => ()
src/main.rs:11 }
src/main.rs:8:5: 11:6 help: Try
if let Some(y) = x { println!("{:?}", y) }
As a cargo subcommand (cargo clippy
)
An alternate way to use clippy is by installing clippy through cargo as a cargo subcommand.
cargo install clippy
Now you can run clippy by invoking cargo clippy
, or
multirust run nightly cargo clippy
directly from a directory that is usually
compiled with stable.
In case you are not using multirust, you need to set the environment flag
SYSROOT
during installation so clippy knows where to find librustc
and
similar crates.
SYSROOT=/path/to/rustc/sysroot cargo install clippy
Running clippy from the command line without installing
To have cargo compile your crate with clippy without needing #![plugin(clippy)]
in your code, you can use:
cargo rustc -- -L /path/to/clippy_so -Z extra-plugins=clippy
Note: Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
Optional dependency
If you want to make clippy an optional dependency, you can do the following:
In your Cargo.toml
:
[dependencies]
clippy = {version = "*", optional = true}
[features]
default=[]
And, in your main.rs
or lib.rs
:
#![cfg_attr(feature="clippy", feature(plugin))]
#![cfg_attr(feature="clippy", plugin(clippy))]
Instead of adding the cfg_attr
attributes you can also run clippy on demand:
cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy
(the -Z no trans
, while not neccessary, will stop the compilation process after
typechecking (and lints) have completed, which can significantly reduce the runtime).
Configuration
Some lints can be configured in a clippy.toml
file. It contains basic variable = value
mapping eg.
blacklisted-names = ["toto", "tata", "titi"]
cyclomatic-complexity-threshold = 30
See the wiki for more information about which lints can be configured and the meaning of the variables.
You can also specify the path to the configuration file with:
#![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
To deactivate the “for further information visit wiki-link” message you can
define the CLIPPY_DISABLE_WIKI_LINKS
environment variable.
Allowing/denying lints
You can add options to allow
/warn
/deny
:
-
the whole set of
Warn
lints using theclippy
lint group (#![deny(clippy)]
) -
all lints using both the
clippy
andclippy_pedantic
lint groups (#![deny(clippy)]
,#![deny(clippy_pedantic)]
). Note thatclippy_pedantic
contains some very aggressive lints prone to false positives. -
only some lints (
#![deny(single_match, box_vec)]
, etc) -
allow
/warn
/deny
can be limited to a single function or module using#[allow(...)]
, etc
Note: deny
produces errors instead of warnings.
For convenience, cargo clippy
automatically defines a clippy
features. This
lets you set lints level and compile with or without clippy transparently:
#[cfg_attr(feature = "clippy", allow(needless_lifetimes))]
Link with clippy service
clippy-service
is a rust web initiative providing rust-clippy
as a web service.
Both projects are independent and maintained by different people
(even if some clippy-service
's contributions are authored by some rust-clippy
members).
You can check out this great service at clippy.bashy.io.
License
Licensed under MPL. If you're having issues with the license, let me know and I'll try to change it to something more permissive.