1 mod bind_instead_of_map;
4 mod chars_cmp_with_unwrap;
6 mod chars_last_cmp_with_unwrap;
8 mod chars_next_cmp_with_unwrap;
11 mod cloned_instead_of_copied;
15 mod extend_with_drain;
18 mod filter_map_identity;
21 mod flat_map_identity;
23 mod from_iter_instead_of_collect;
24 mod get_last_with_len;
27 mod inefficient_to_string;
30 mod is_digit_ascii_radix;
31 mod iter_cloned_collect;
36 mod iter_overeager_cloned;
39 mod iterator_step_by_zero;
40 mod manual_saturating_arithmetic;
41 mod manual_str_repeat;
42 mod map_collect_result_unit;
46 mod needless_option_as_deref;
47 mod needless_option_take;
48 mod no_effect_replace;
49 mod obfuscated_if_else;
51 mod option_as_ref_deref;
52 mod option_map_or_none;
53 mod option_map_unwrap_or;
57 mod single_char_add_str;
58 mod single_char_insert_string;
59 mod single_char_pattern;
60 mod single_char_push_string;
63 mod string_extend_chars;
65 mod suspicious_splitn;
66 mod uninit_assumed_init;
67 mod unnecessary_filter_map;
69 mod unnecessary_iter_cloned;
71 mod unnecessary_lazy_eval;
72 mod unnecessary_to_owned;
73 mod unwrap_or_else_default;
77 mod wrong_self_convention;
80 use bind_instead_of_map::BindInsteadOfMap;
81 use clippy_utils::consts::{constant, Constant};
82 use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
83 use clippy_utils::ty::{contains_adt_constructor, contains_ty, implements_trait, is_copy, is_type_diagnostic_item};
84 use clippy_utils::{contains_return, get_trait_def_id, iter_input_pats, meets_msrv, msrvs, paths, return_ty};
85 use if_chain::if_chain;
87 use rustc_hir::def::Res;
88 use rustc_hir::{Expr, ExprKind, PrimTy, QPath, TraitItem, TraitItemKind};
89 use rustc_lint::{LateContext, LateLintPass, LintContext};
90 use rustc_middle::lint::in_external_macro;
91 use rustc_middle::ty::{self, TraitRef, Ty};
92 use rustc_semver::RustcVersion;
93 use rustc_session::{declare_tool_lint, impl_lint_pass};
94 use rustc_span::{sym, Span};
95 use rustc_typeck::hir_ty_to_ty;
97 declare_clippy_lint! {
99 /// Checks for usages of `cloned()` on an `Iterator` or `Option` where
100 /// `copied()` could be used instead.
102 /// ### Why is this bad?
103 /// `copied()` is better because it guarantees that the type being cloned
104 /// implements `Copy`.
108 /// [1, 2, 3].iter().cloned();
112 /// [1, 2, 3].iter().copied();
114 #[clippy::version = "1.53.0"]
115 pub CLONED_INSTEAD_OF_COPIED,
117 "used `cloned` where `copied` could be used instead"
120 declare_clippy_lint! {
122 /// Checks for usage of `_.cloned().<func>()` where call to `.cloned()` can be postponed.
124 /// ### Why is this bad?
125 /// It's often inefficient to clone all elements of an iterator, when eventually, only some
126 /// of them will be consumed.
128 /// ### Known Problems
129 /// This `lint` removes the side of effect of cloning items in the iterator.
130 /// A code that relies on that side-effect could fail.
134 /// # let vec = vec!["string".to_string()];
135 /// vec.iter().cloned().take(10);
136 /// vec.iter().cloned().last();
141 /// # let vec = vec!["string".to_string()];
142 /// vec.iter().take(10).cloned();
143 /// vec.iter().last().cloned();
145 #[clippy::version = "1.60.0"]
146 pub ITER_OVEREAGER_CLONED,
148 "using `cloned()` early with `Iterator::iter()` can lead to some performance inefficiencies"
151 declare_clippy_lint! {
153 /// Checks for usages of `Iterator::flat_map()` where `filter_map()` could be
156 /// ### Why is this bad?
157 /// When applicable, `filter_map()` is more clear since it shows that
158 /// `Option` is used to produce 0 or 1 items.
162 /// let nums: Vec<i32> = ["1", "2", "whee!"].iter().flat_map(|x| x.parse().ok()).collect();
166 /// let nums: Vec<i32> = ["1", "2", "whee!"].iter().filter_map(|x| x.parse().ok()).collect();
168 #[clippy::version = "1.53.0"]
171 "used `flat_map` where `filter_map` could be used instead"
174 declare_clippy_lint! {
176 /// Checks for `.unwrap()` calls on `Option`s and on `Result`s.
178 /// ### Why is this bad?
179 /// It is better to handle the `None` or `Err` case,
180 /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
181 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
182 /// `Allow` by default.
184 /// `result.unwrap()` will let the thread panic on `Err` values.
185 /// Normally, you want to implement more sophisticated error handling,
186 /// and propagate errors upwards with `?` operator.
188 /// Even if you want to panic on errors, not all `Error`s implement good
189 /// messages on display. Therefore, it may be beneficial to look at the places
190 /// where they may get displayed. Activate this lint to do just that.
194 /// # let option = Some(1);
195 /// # let result: Result<usize, ()> = Ok(1);
200 /// If [expect_used](#expect_used) is allowed, instead:
202 /// # let option = Some(1);
203 /// # let result: Result<usize, ()> = Ok(1);
204 /// option.expect("more helpful message");
205 /// result.expect("more helpful message");
208 /// Otherwise try using
216 #[clippy::version = "1.45.0"]
219 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
222 declare_clippy_lint! {
224 /// Checks for `.expect()` calls on `Option`s and `Result`s.
226 /// ### Why is this bad?
227 /// Usually it is better to handle the `None` or `Err` case.
228 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
229 /// this lint is `Allow` by default.
231 /// `result.expect()` will let the thread panic on `Err`
232 /// values. Normally, you want to implement more sophisticated error handling,
233 /// and propagate errors upwards with `?` operator.
237 /// # let option = Some(1);
238 /// # let result: Result<usize, ()> = Ok(1);
239 /// option.expect("one");
240 /// result.expect("one");
245 /// # let option = Some(1);
246 /// # let result: Result<usize, ()> = Ok(1);
253 #[clippy::version = "1.45.0"]
256 "using `.expect()` on `Result` or `Option`, which might be better handled"
259 declare_clippy_lint! {
261 /// Checks for methods that should live in a trait
262 /// implementation of a `std` trait (see [llogiq's blog
263 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
264 /// information) instead of an inherent implementation.
266 /// ### Why is this bad?
267 /// Implementing the traits improve ergonomics for users of
268 /// the code, often with very little cost. Also people seeing a `mul(...)`
270 /// may expect `*` to work equally, so you should have good reason to disappoint
277 /// fn add(&self, other: &X) -> X {
283 #[clippy::version = "pre 1.29.0"]
284 pub SHOULD_IMPLEMENT_TRAIT,
286 "defining a method that should be implementing a std trait"
289 declare_clippy_lint! {
291 /// Checks for methods with certain name prefixes and which
292 /// doesn't match how self is taken. The actual rules are:
294 /// |Prefix |Postfix |`self` taken | `self` type |
295 /// |-------|------------|-------------------------------|--------------|
296 /// |`as_` | none |`&self` or `&mut self` | any |
297 /// |`from_`| none | none | any |
298 /// |`into_`| none |`self` | any |
299 /// |`is_` | none |`&mut self` or `&self` or none | any |
300 /// |`to_` | `_mut` |`&mut self` | any |
301 /// |`to_` | not `_mut` |`self` | `Copy` |
302 /// |`to_` | not `_mut` |`&self` | not `Copy` |
304 /// Note: Clippy doesn't trigger methods with `to_` prefix in:
305 /// - Traits definition.
306 /// Clippy can not tell if a type that implements a trait is `Copy` or not.
307 /// - Traits implementation, when `&self` is taken.
308 /// The method signature is controlled by the trait and often `&self` is required for all types that implement the trait
309 /// (see e.g. the `std::string::ToString` trait).
311 /// Clippy allows `Pin<&Self>` and `Pin<&mut Self>` if `&self` and `&mut self` is required.
313 /// Please find more info here:
314 /// https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv
316 /// ### Why is this bad?
317 /// Consistency breeds readability. If you follow the
318 /// conventions, your users won't be surprised that they, e.g., need to supply a
319 /// mutable reference to a `as_..` function.
325 /// fn as_str(self) -> &'static str {
331 #[clippy::version = "pre 1.29.0"]
332 pub WRONG_SELF_CONVENTION,
334 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
337 declare_clippy_lint! {
339 /// Checks for usage of `ok().expect(..)`.
341 /// ### Why is this bad?
342 /// Because you usually call `expect()` on the `Result`
343 /// directly to get a better error message.
345 /// ### Known problems
346 /// The error type needs to implement `Debug`
350 /// # let x = Ok::<_, ()>(());
351 /// x.ok().expect("why did I do this again?");
356 /// # let x = Ok::<_, ()>(());
357 /// x.expect("why did I do this again?");
359 #[clippy::version = "pre 1.29.0"]
362 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
365 declare_clippy_lint! {
367 /// Checks for `.err().expect()` calls on the `Result` type.
369 /// ### Why is this bad?
370 /// `.expect_err()` can be called directly to avoid the extra type conversion from `err()`.
374 /// let x: Result<u32, &str> = Ok(10);
375 /// x.err().expect("Testing err().expect()");
379 /// let x: Result<u32, &str> = Ok(10);
380 /// x.expect_err("Testing expect_err");
382 #[clippy::version = "1.62.0"]
385 r#"using `.err().expect("")` when `.expect_err("")` can be used"#
388 declare_clippy_lint! {
390 /// Checks for usages of `_.unwrap_or_else(Default::default)` on `Option` and
393 /// ### Why is this bad?
394 /// Readability, these can be written as `_.unwrap_or_default`, which is
395 /// simpler and more concise.
399 /// # let x = Some(1);
400 /// x.unwrap_or_else(Default::default);
401 /// x.unwrap_or_else(u32::default);
406 /// # let x = Some(1);
407 /// x.unwrap_or_default();
409 #[clippy::version = "1.56.0"]
410 pub UNWRAP_OR_ELSE_DEFAULT,
412 "using `.unwrap_or_else(Default::default)`, which is more succinctly expressed as `.unwrap_or_default()`"
415 declare_clippy_lint! {
417 /// Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
418 /// `result.map(_).unwrap_or_else(_)`.
420 /// ### Why is this bad?
421 /// Readability, these can be written more concisely (resp.) as
422 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
424 /// ### Known problems
425 /// The order of the arguments is not in execution order
429 /// # let option = Some(1);
430 /// # let result: Result<usize, ()> = Ok(1);
431 /// # fn some_function(foo: ()) -> usize { 1 }
432 /// option.map(|a| a + 1).unwrap_or(0);
433 /// result.map(|a| a + 1).unwrap_or_else(some_function);
438 /// # let option = Some(1);
439 /// # let result: Result<usize, ()> = Ok(1);
440 /// # fn some_function(foo: ()) -> usize { 1 }
441 /// option.map_or(0, |a| a + 1);
442 /// result.map_or_else(some_function, |a| a + 1);
444 #[clippy::version = "1.45.0"]
447 "using `.map(f).unwrap_or(a)` or `.map(f).unwrap_or_else(func)`, which are more succinctly expressed as `map_or(a, f)` or `map_or_else(a, f)`"
450 declare_clippy_lint! {
452 /// Checks for usage of `_.map_or(None, _)`.
454 /// ### Why is this bad?
455 /// Readability, this can be written more concisely as
458 /// ### Known problems
459 /// The order of the arguments is not in execution order.
463 /// # let opt = Some(1);
464 /// opt.map_or(None, |a| Some(a + 1));
469 /// # let opt = Some(1);
470 /// opt.and_then(|a| Some(a + 1));
472 #[clippy::version = "pre 1.29.0"]
473 pub OPTION_MAP_OR_NONE,
475 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
478 declare_clippy_lint! {
480 /// Checks for usage of `_.map_or(None, Some)`.
482 /// ### Why is this bad?
483 /// Readability, this can be written more concisely as
488 /// # let r: Result<u32, &str> = Ok(1);
489 /// assert_eq!(Some(1), r.map_or(None, Some));
494 /// # let r: Result<u32, &str> = Ok(1);
495 /// assert_eq!(Some(1), r.ok());
497 #[clippy::version = "1.44.0"]
498 pub RESULT_MAP_OR_INTO_OPTION,
500 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
503 declare_clippy_lint! {
505 /// Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
506 /// `_.or_else(|x| Err(y))`.
508 /// ### Why is this bad?
509 /// Readability, this can be written more concisely as
510 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
514 /// # fn opt() -> Option<&'static str> { Some("42") }
515 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
516 /// let _ = opt().and_then(|s| Some(s.len()));
517 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
518 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
521 /// The correct use would be:
524 /// # fn opt() -> Option<&'static str> { Some("42") }
525 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
526 /// let _ = opt().map(|s| s.len());
527 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
528 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
530 #[clippy::version = "1.45.0"]
531 pub BIND_INSTEAD_OF_MAP,
533 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
536 declare_clippy_lint! {
538 /// Checks for usage of `_.filter(_).next()`.
540 /// ### Why is this bad?
541 /// Readability, this can be written more concisely as
546 /// # let vec = vec![1];
547 /// vec.iter().filter(|x| **x == 0).next();
552 /// # let vec = vec![1];
553 /// vec.iter().find(|x| **x == 0);
555 #[clippy::version = "pre 1.29.0"]
558 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
561 declare_clippy_lint! {
563 /// Checks for usage of `_.skip_while(condition).next()`.
565 /// ### Why is this bad?
566 /// Readability, this can be written more concisely as
567 /// `_.find(!condition)`.
571 /// # let vec = vec![1];
572 /// vec.iter().skip_while(|x| **x == 0).next();
577 /// # let vec = vec![1];
578 /// vec.iter().find(|x| **x != 0);
580 #[clippy::version = "1.42.0"]
583 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
586 declare_clippy_lint! {
588 /// Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
590 /// ### Why is this bad?
591 /// Readability, this can be written more concisely as
592 /// `_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
596 /// let vec = vec![vec![1]];
597 /// let opt = Some(5);
599 /// vec.iter().map(|x| x.iter()).flatten();
600 /// opt.map(|x| Some(x * 2)).flatten();
605 /// # let vec = vec![vec![1]];
606 /// # let opt = Some(5);
607 /// vec.iter().flat_map(|x| x.iter());
608 /// opt.and_then(|x| Some(x * 2));
610 #[clippy::version = "1.31.0"]
613 "using combinations of `flatten` and `map` which can usually be written as a single method call"
616 declare_clippy_lint! {
618 /// Checks for usage of `_.filter(_).map(_)` that can be written more simply
619 /// as `filter_map(_)`.
621 /// ### Why is this bad?
622 /// Redundant code in the `filter` and `map` operations is poor style and
627 /// # #![allow(unused)]
629 /// .filter(|n| n.checked_add(1).is_some())
630 /// .map(|n| n.checked_add(1).unwrap());
635 /// # #[allow(unused)]
636 /// (0_i32..10).filter_map(|n| n.checked_add(1));
638 #[clippy::version = "1.51.0"]
639 pub MANUAL_FILTER_MAP,
641 "using `_.filter(_).map(_)` in a way that can be written more simply as `filter_map(_)`"
644 declare_clippy_lint! {
646 /// Checks for usage of `_.find(_).map(_)` that can be written more simply
647 /// as `find_map(_)`.
649 /// ### Why is this bad?
650 /// Redundant code in the `find` and `map` operations is poor style and
656 /// .find(|n| n.checked_add(1).is_some())
657 /// .map(|n| n.checked_add(1).unwrap());
662 /// (0_i32..10).find_map(|n| n.checked_add(1));
664 #[clippy::version = "1.51.0"]
667 "using `_.find(_).map(_)` in a way that can be written more simply as `find_map(_)`"
670 declare_clippy_lint! {
672 /// Checks for usage of `_.filter_map(_).next()`.
674 /// ### Why is this bad?
675 /// Readability, this can be written more concisely as
680 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
682 /// Can be written as
685 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
687 #[clippy::version = "1.36.0"]
690 "using combination of `filter_map` and `next` which can usually be written as a single method call"
693 declare_clippy_lint! {
695 /// Checks for usage of `flat_map(|x| x)`.
697 /// ### Why is this bad?
698 /// Readability, this can be written more concisely by using `flatten`.
702 /// # let iter = vec![vec![0]].into_iter();
703 /// iter.flat_map(|x| x);
705 /// Can be written as
707 /// # let iter = vec![vec![0]].into_iter();
710 #[clippy::version = "1.39.0"]
711 pub FLAT_MAP_IDENTITY,
713 "call to `flat_map` where `flatten` is sufficient"
716 declare_clippy_lint! {
718 /// Checks for an iterator or string search (such as `find()`,
719 /// `position()`, or `rposition()`) followed by a call to `is_some()` or `is_none()`.
721 /// ### Why is this bad?
722 /// Readability, this can be written more concisely as:
723 /// * `_.any(_)`, or `_.contains(_)` for `is_some()`,
724 /// * `!_.any(_)`, or `!_.contains(_)` for `is_none()`.
728 /// # #![allow(unused)]
729 /// let vec = vec![1];
730 /// vec.iter().find(|x| **x == 0).is_some();
732 /// "hello world".find("world").is_none();
737 /// let vec = vec![1];
738 /// vec.iter().any(|x| *x == 0);
740 /// # #[allow(unused)]
741 /// !"hello world".contains("world");
743 #[clippy::version = "pre 1.29.0"]
746 "using an iterator or string search followed by `is_some()` or `is_none()`, which is more succinctly expressed as a call to `any()` or `contains()` (with negation in case of `is_none()`)"
749 declare_clippy_lint! {
751 /// Checks for usage of `.chars().next()` on a `str` to check
752 /// if it starts with a given char.
754 /// ### Why is this bad?
755 /// Readability, this can be written more concisely as
756 /// `_.starts_with(_)`.
760 /// let name = "foo";
761 /// if name.chars().next() == Some('_') {};
766 /// let name = "foo";
767 /// if name.starts_with('_') {};
769 #[clippy::version = "pre 1.29.0"]
772 "using `.chars().next()` to check if a string starts with a char"
775 declare_clippy_lint! {
777 /// Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
778 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
779 /// `unwrap_or_default` instead.
781 /// ### Why is this bad?
782 /// The function will always be called and potentially
783 /// allocate an object acting as the default.
785 /// ### Known problems
786 /// If the function has side-effects, not calling it will
787 /// change the semantic of the program, but you shouldn't rely on that anyway.
791 /// # let foo = Some(String::new());
792 /// foo.unwrap_or(String::new());
797 /// # let foo = Some(String::new());
798 /// foo.unwrap_or_else(String::new);
802 /// # let foo = Some(String::new());
803 /// foo.unwrap_or_default();
805 #[clippy::version = "pre 1.29.0"]
808 "using any `*or` method with a function call, which suggests `*or_else`"
811 declare_clippy_lint! {
813 /// Checks for `.or(…).unwrap()` calls to Options and Results.
815 /// ### Why is this bad?
816 /// You should use `.unwrap_or(…)` instead for clarity.
820 /// # let fallback = "fallback";
822 /// # type Error = &'static str;
823 /// # let result: Result<&str, Error> = Err("error");
824 /// let value = result.or::<Error>(Ok(fallback)).unwrap();
827 /// # let option: Option<&str> = None;
828 /// let value = option.or(Some(fallback)).unwrap();
832 /// # let fallback = "fallback";
834 /// # let result: Result<&str, &str> = Err("error");
835 /// let value = result.unwrap_or(fallback);
838 /// # let option: Option<&str> = None;
839 /// let value = option.unwrap_or(fallback);
841 #[clippy::version = "1.61.0"]
844 "checks for `.or(…).unwrap()` calls to Options and Results."
847 declare_clippy_lint! {
849 /// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
850 /// etc., and suggests to use `unwrap_or_else` instead
852 /// ### Why is this bad?
853 /// The function will always be called.
855 /// ### Known problems
856 /// If the function has side-effects, not calling it will
857 /// change the semantics of the program, but you shouldn't rely on that anyway.
861 /// # let foo = Some(String::new());
862 /// # let err_code = "418";
863 /// # let err_msg = "I'm a teapot";
864 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
868 /// # let foo = Some(String::new());
869 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
874 /// # let foo = Some(String::new());
875 /// # let err_code = "418";
876 /// # let err_msg = "I'm a teapot";
877 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
879 #[clippy::version = "pre 1.29.0"]
882 "using any `expect` method with a function call"
885 declare_clippy_lint! {
887 /// Checks for usage of `.clone()` on a `Copy` type.
889 /// ### Why is this bad?
890 /// The only reason `Copy` types implement `Clone` is for
891 /// generics, not for using the `clone` method on a concrete type.
897 #[clippy::version = "pre 1.29.0"]
900 "using `clone` on a `Copy` type"
903 declare_clippy_lint! {
905 /// Checks for usage of `.clone()` on a ref-counted pointer,
906 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
907 /// function syntax instead (e.g., `Rc::clone(foo)`).
909 /// ### Why is this bad?
910 /// Calling '.clone()' on an Rc, Arc, or Weak
911 /// can obscure the fact that only the pointer is being cloned, not the underlying
916 /// # use std::rc::Rc;
917 /// let x = Rc::new(1);
924 /// # use std::rc::Rc;
925 /// # let x = Rc::new(1);
928 #[clippy::version = "pre 1.29.0"]
929 pub CLONE_ON_REF_PTR,
931 "using 'clone' on a ref-counted pointer"
934 declare_clippy_lint! {
936 /// Checks for usage of `.clone()` on an `&&T`.
938 /// ### Why is this bad?
939 /// Cloning an `&&T` copies the inner `&T`, instead of
940 /// cloning the underlying `T`.
947 /// let z = y.clone();
948 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
951 #[clippy::version = "pre 1.29.0"]
952 pub CLONE_DOUBLE_REF,
954 "using `clone` on `&&T`"
957 declare_clippy_lint! {
959 /// Checks for usage of `.to_string()` on an `&&T` where
960 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
962 /// ### Why is this bad?
963 /// This bypasses the specialized implementation of
964 /// `ToString` and instead goes through the more expensive string formatting
969 /// // Generic implementation for `T: Display` is used (slow)
970 /// ["foo", "bar"].iter().map(|s| s.to_string());
972 /// // OK, the specialized impl is used
973 /// ["foo", "bar"].iter().map(|&s| s.to_string());
975 #[clippy::version = "1.40.0"]
976 pub INEFFICIENT_TO_STRING,
978 "using `to_string` on `&&T` where `T: ToString`"
981 declare_clippy_lint! {
983 /// Checks for `new` not returning a type that contains `Self`.
985 /// ### Why is this bad?
986 /// As a convention, `new` methods are used to make a new
987 /// instance of a type.
990 /// In an impl block:
993 /// # struct NotAFoo;
995 /// fn new() -> NotAFoo {
1003 /// struct Bar(Foo);
1005 /// // Bad. The type name must contain `Self`
1006 /// fn new() -> Bar {
1014 /// # struct FooError;
1016 /// // Good. Return type contains `Self`
1017 /// fn new() -> Result<Foo, FooError> {
1023 /// Or in a trait definition:
1025 /// pub trait Trait {
1026 /// // Bad. The type name must contain `Self`
1032 /// pub trait Trait {
1033 /// // Good. Return type contains `Self`
1034 /// fn new() -> Self;
1037 #[clippy::version = "pre 1.29.0"]
1038 pub NEW_RET_NO_SELF,
1040 "not returning type containing `Self` in a `new` method"
1043 declare_clippy_lint! {
1044 /// ### What it does
1045 /// Checks for string methods that receive a single-character
1046 /// `str` as an argument, e.g., `_.split("x")`.
1048 /// ### Why is this bad?
1049 /// Performing these methods using a `char` is faster than
1052 /// ### Known problems
1053 /// Does not catch multi-byte unicode characters.
1064 #[clippy::version = "pre 1.29.0"]
1065 pub SINGLE_CHAR_PATTERN,
1067 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
1070 declare_clippy_lint! {
1071 /// ### What it does
1072 /// Checks for calling `.step_by(0)` on iterators which panics.
1074 /// ### Why is this bad?
1075 /// This very much looks like an oversight. Use `panic!()` instead if you
1076 /// actually intend to panic.
1079 /// ```rust,should_panic
1080 /// for x in (0..100).step_by(0) {
1084 #[clippy::version = "pre 1.29.0"]
1085 pub ITERATOR_STEP_BY_ZERO,
1087 "using `Iterator::step_by(0)`, which will panic at runtime"
1090 declare_clippy_lint! {
1091 /// ### What it does
1092 /// Checks for indirect collection of populated `Option`
1094 /// ### Why is this bad?
1095 /// `Option` is like a collection of 0-1 things, so `flatten`
1096 /// automatically does this without suspicious-looking `unwrap` calls.
1100 /// let _ = std::iter::empty::<Option<i32>>().filter(Option::is_some).map(Option::unwrap);
1104 /// let _ = std::iter::empty::<Option<i32>>().flatten();
1106 #[clippy::version = "1.53.0"]
1107 pub OPTION_FILTER_MAP,
1109 "filtering `Option` for `Some` then force-unwrapping, which can be one type-safe operation"
1112 declare_clippy_lint! {
1113 /// ### What it does
1114 /// Checks for the use of `iter.nth(0)`.
1116 /// ### Why is this bad?
1117 /// `iter.next()` is equivalent to
1118 /// `iter.nth(0)`, as they both consume the next element,
1119 /// but is more readable.
1123 /// # use std::collections::HashSet;
1124 /// # let mut s = HashSet::new();
1126 /// let x = s.iter().nth(0);
1131 /// # use std::collections::HashSet;
1132 /// # let mut s = HashSet::new();
1134 /// let x = s.iter().next();
1136 #[clippy::version = "1.42.0"]
1139 "replace `iter.nth(0)` with `iter.next()`"
1142 declare_clippy_lint! {
1143 /// ### What it does
1144 /// Checks for use of `.iter().nth()` (and the related
1145 /// `.iter_mut().nth()`) on standard library types with *O*(1) element access.
1147 /// ### Why is this bad?
1148 /// `.get()` and `.get_mut()` are more efficient and more
1153 /// let some_vec = vec![0, 1, 2, 3];
1154 /// let bad_vec = some_vec.iter().nth(3);
1155 /// let bad_slice = &some_vec[..].iter().nth(3);
1157 /// The correct use would be:
1159 /// let some_vec = vec![0, 1, 2, 3];
1160 /// let bad_vec = some_vec.get(3);
1161 /// let bad_slice = &some_vec[..].get(3);
1163 #[clippy::version = "pre 1.29.0"]
1166 "using `.iter().nth()` on a standard library type with O(1) element access"
1169 declare_clippy_lint! {
1170 /// ### What it does
1171 /// Checks for use of `.skip(x).next()` on iterators.
1173 /// ### Why is this bad?
1174 /// `.nth(x)` is cleaner
1178 /// let some_vec = vec![0, 1, 2, 3];
1179 /// let bad_vec = some_vec.iter().skip(3).next();
1180 /// let bad_slice = &some_vec[..].iter().skip(3).next();
1182 /// The correct use would be:
1184 /// let some_vec = vec![0, 1, 2, 3];
1185 /// let bad_vec = some_vec.iter().nth(3);
1186 /// let bad_slice = &some_vec[..].iter().nth(3);
1188 #[clippy::version = "pre 1.29.0"]
1191 "using `.skip(x).next()` on an iterator"
1194 declare_clippy_lint! {
1195 /// ### What it does
1196 /// Checks for use of `.drain(..)` on `Vec` and `VecDeque` for iteration.
1198 /// ### Why is this bad?
1199 /// `.into_iter()` is simpler with better performance.
1203 /// # use std::collections::HashSet;
1204 /// let mut foo = vec![0, 1, 2, 3];
1205 /// let bar: HashSet<usize> = foo.drain(..).collect();
1209 /// # use std::collections::HashSet;
1210 /// let foo = vec![0, 1, 2, 3];
1211 /// let bar: HashSet<usize> = foo.into_iter().collect();
1213 #[clippy::version = "1.61.0"]
1214 pub ITER_WITH_DRAIN,
1216 "replace `.drain(..)` with `.into_iter()`"
1219 declare_clippy_lint! {
1220 /// ### What it does
1221 /// Checks for using `x.get(x.len() - 1)` instead of
1224 /// ### Why is this bad?
1225 /// Using `x.last()` is easier to read and has the same
1228 /// Note that using `x[x.len() - 1]` is semantically different from
1229 /// `x.last()`. Indexing into the array will panic on out-of-bounds
1230 /// accesses, while `x.get()` and `x.last()` will return `None`.
1232 /// There is another lint (get_unwrap) that covers the case of using
1233 /// `x.get(index).unwrap()` instead of `x[index]`.
1237 /// let x = vec![2, 3, 5];
1238 /// let last_element = x.get(x.len() - 1);
1243 /// let x = vec![2, 3, 5];
1244 /// let last_element = x.last();
1246 #[clippy::version = "1.37.0"]
1247 pub GET_LAST_WITH_LEN,
1249 "Using `x.get(x.len() - 1)` when `x.last()` is correct and simpler"
1252 declare_clippy_lint! {
1253 /// ### What it does
1254 /// Checks for use of `.get().unwrap()` (or
1255 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
1257 /// ### Why is this bad?
1258 /// Using the Index trait (`[]`) is more clear and more
1261 /// ### Known problems
1262 /// Not a replacement for error handling: Using either
1263 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
1264 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
1265 /// temporary placeholder for dealing with the `Option` type, then this does
1266 /// not mitigate the need for error handling. If there is a chance that `.get()`
1267 /// will be `None` in your program, then it is advisable that the `None` case
1268 /// is handled in a future refactor instead of using `.unwrap()` or the Index
1273 /// let mut some_vec = vec![0, 1, 2, 3];
1274 /// let last = some_vec.get(3).unwrap();
1275 /// *some_vec.get_mut(0).unwrap() = 1;
1277 /// The correct use would be:
1279 /// let mut some_vec = vec![0, 1, 2, 3];
1280 /// let last = some_vec[3];
1281 /// some_vec[0] = 1;
1283 #[clippy::version = "pre 1.29.0"]
1286 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
1289 declare_clippy_lint! {
1290 /// ### What it does
1291 /// Checks for occurrences where one vector gets extended instead of append
1293 /// ### Why is this bad?
1294 /// Using `append` instead of `extend` is more concise and faster
1298 /// let mut a = vec![1, 2, 3];
1299 /// let mut b = vec![4, 5, 6];
1301 /// a.extend(b.drain(..));
1306 /// let mut a = vec![1, 2, 3];
1307 /// let mut b = vec![4, 5, 6];
1309 /// a.append(&mut b);
1311 #[clippy::version = "1.55.0"]
1312 pub EXTEND_WITH_DRAIN,
1314 "using vec.append(&mut vec) to move the full range of a vector to another"
1317 declare_clippy_lint! {
1318 /// ### What it does
1319 /// Checks for the use of `.extend(s.chars())` where s is a
1320 /// `&str` or `String`.
1322 /// ### Why is this bad?
1323 /// `.push_str(s)` is clearer
1327 /// let abc = "abc";
1328 /// let def = String::from("def");
1329 /// let mut s = String::new();
1330 /// s.extend(abc.chars());
1331 /// s.extend(def.chars());
1333 /// The correct use would be:
1335 /// let abc = "abc";
1336 /// let def = String::from("def");
1337 /// let mut s = String::new();
1338 /// s.push_str(abc);
1339 /// s.push_str(&def);
1341 #[clippy::version = "pre 1.29.0"]
1342 pub STRING_EXTEND_CHARS,
1344 "using `x.extend(s.chars())` where s is a `&str` or `String`"
1347 declare_clippy_lint! {
1348 /// ### What it does
1349 /// Checks for the use of `.cloned().collect()` on slice to
1352 /// ### Why is this bad?
1353 /// `.to_vec()` is clearer
1357 /// let s = [1, 2, 3, 4, 5];
1358 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
1360 /// The better use would be:
1362 /// let s = [1, 2, 3, 4, 5];
1363 /// let s2: Vec<isize> = s.to_vec();
1365 #[clippy::version = "pre 1.29.0"]
1366 pub ITER_CLONED_COLLECT,
1368 "using `.cloned().collect()` on slice to create a `Vec`"
1371 declare_clippy_lint! {
1372 /// ### What it does
1373 /// Checks for usage of `_.chars().last()` or
1374 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1376 /// ### Why is this bad?
1377 /// Readability, this can be written more concisely as
1378 /// `_.ends_with(_)`.
1382 /// # let name = "_";
1383 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1388 /// # let name = "_";
1389 /// name.ends_with('_') || name.ends_with('-');
1391 #[clippy::version = "pre 1.29.0"]
1394 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1397 declare_clippy_lint! {
1398 /// ### What it does
1399 /// Checks for usage of `.as_ref()` or `.as_mut()` where the
1400 /// types before and after the call are the same.
1402 /// ### Why is this bad?
1403 /// The call is unnecessary.
1407 /// # fn do_stuff(x: &[i32]) {}
1408 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1409 /// do_stuff(x.as_ref());
1411 /// The correct use would be:
1413 /// # fn do_stuff(x: &[i32]) {}
1414 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1417 #[clippy::version = "pre 1.29.0"]
1420 "using `as_ref` where the types before and after the call are the same"
1423 declare_clippy_lint! {
1424 /// ### What it does
1425 /// Checks for using `fold` when a more succinct alternative exists.
1426 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1427 /// `sum` or `product`.
1429 /// ### Why is this bad?
1434 /// # #[allow(unused)]
1435 /// (0..3).fold(false, |acc, x| acc || x > 2);
1440 /// (0..3).any(|x| x > 2);
1442 #[clippy::version = "pre 1.29.0"]
1443 pub UNNECESSARY_FOLD,
1445 "using `fold` when a more succinct alternative exists"
1448 declare_clippy_lint! {
1449 /// ### What it does
1450 /// Checks for `filter_map` calls that could be replaced by `filter` or `map`.
1451 /// More specifically it checks if the closure provided is only performing one of the
1452 /// filter or map operations and suggests the appropriate option.
1454 /// ### Why is this bad?
1455 /// Complexity. The intent is also clearer if only a single
1456 /// operation is being performed.
1460 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1462 /// // As there is no transformation of the argument this could be written as:
1463 /// let _ = (0..3).filter(|&x| x > 2);
1467 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1469 /// // As there is no conditional check on the argument this could be written as:
1470 /// let _ = (0..4).map(|x| x + 1);
1472 #[clippy::version = "1.31.0"]
1473 pub UNNECESSARY_FILTER_MAP,
1475 "using `filter_map` when a more succinct alternative exists"
1478 declare_clippy_lint! {
1479 /// ### What it does
1480 /// Checks for `find_map` calls that could be replaced by `find` or `map`. More
1481 /// specifically it checks if the closure provided is only performing one of the
1482 /// find or map operations and suggests the appropriate option.
1484 /// ### Why is this bad?
1485 /// Complexity. The intent is also clearer if only a single
1486 /// operation is being performed.
1490 /// let _ = (0..3).find_map(|x| if x > 2 { Some(x) } else { None });
1492 /// // As there is no transformation of the argument this could be written as:
1493 /// let _ = (0..3).find(|&x| x > 2);
1497 /// let _ = (0..4).find_map(|x| Some(x + 1));
1499 /// // As there is no conditional check on the argument this could be written as:
1500 /// let _ = (0..4).map(|x| x + 1).next();
1502 #[clippy::version = "1.61.0"]
1503 pub UNNECESSARY_FIND_MAP,
1505 "using `find_map` when a more succinct alternative exists"
1508 declare_clippy_lint! {
1509 /// ### What it does
1510 /// Checks for `into_iter` calls on references which should be replaced by `iter`
1513 /// ### Why is this bad?
1514 /// Readability. Calling `into_iter` on a reference will not move out its
1515 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1516 /// `iter_mut` directly.
1520 /// # let vec = vec![3, 4, 5];
1521 /// (&vec).into_iter();
1526 /// # let vec = vec![3, 4, 5];
1529 #[clippy::version = "1.32.0"]
1530 pub INTO_ITER_ON_REF,
1532 "using `.into_iter()` on a reference"
1535 declare_clippy_lint! {
1536 /// ### What it does
1537 /// Checks for calls to `map` followed by a `count`.
1539 /// ### Why is this bad?
1540 /// It looks suspicious. Maybe `map` was confused with `filter`.
1541 /// If the `map` call is intentional, this should be rewritten
1542 /// using `inspect`. Or, if you intend to drive the iterator to
1543 /// completion, you can just use `for_each` instead.
1547 /// let _ = (0..3).map(|x| x + 2).count();
1549 #[clippy::version = "1.39.0"]
1552 "suspicious usage of map"
1555 declare_clippy_lint! {
1556 /// ### What it does
1557 /// Checks for `MaybeUninit::uninit().assume_init()`.
1559 /// ### Why is this bad?
1560 /// For most types, this is undefined behavior.
1562 /// ### Known problems
1563 /// For now, we accept empty tuples and tuples / arrays
1564 /// of `MaybeUninit`. There may be other types that allow uninitialized
1565 /// data, but those are not yet rigorously defined.
1569 /// // Beware the UB
1570 /// use std::mem::MaybeUninit;
1572 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1575 /// Note that the following is OK:
1578 /// use std::mem::MaybeUninit;
1580 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1581 /// MaybeUninit::uninit().assume_init()
1584 #[clippy::version = "1.39.0"]
1585 pub UNINIT_ASSUMED_INIT,
1587 "`MaybeUninit::uninit().assume_init()`"
1590 declare_clippy_lint! {
1591 /// ### What it does
1592 /// Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1594 /// ### Why is this bad?
1595 /// These can be written simply with `saturating_add/sub` methods.
1599 /// # let y: u32 = 0;
1600 /// # let x: u32 = 100;
1601 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1602 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1605 /// can be written using dedicated methods for saturating addition/subtraction as:
1608 /// # let y: u32 = 0;
1609 /// # let x: u32 = 100;
1610 /// let add = x.saturating_add(y);
1611 /// let sub = x.saturating_sub(y);
1613 #[clippy::version = "1.39.0"]
1614 pub MANUAL_SATURATING_ARITHMETIC,
1616 "`.checked_add/sub(x).unwrap_or(MAX/MIN)`"
1619 declare_clippy_lint! {
1620 /// ### What it does
1621 /// Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1622 /// zero-sized types
1624 /// ### Why is this bad?
1625 /// This is a no-op, and likely unintended
1629 /// unsafe { (&() as *const ()).offset(1) };
1631 #[clippy::version = "1.41.0"]
1634 "Check for offset calculations on raw pointers to zero-sized types"
1637 declare_clippy_lint! {
1638 /// ### What it does
1639 /// Checks for `FileType::is_file()`.
1641 /// ### Why is this bad?
1642 /// When people testing a file type with `FileType::is_file`
1643 /// they are testing whether a path is something they can get bytes from. But
1644 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1645 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1650 /// let metadata = std::fs::metadata("foo.txt")?;
1651 /// let filetype = metadata.file_type();
1653 /// if filetype.is_file() {
1656 /// # Ok::<_, std::io::Error>(())
1660 /// should be written as:
1664 /// let metadata = std::fs::metadata("foo.txt")?;
1665 /// let filetype = metadata.file_type();
1667 /// if !filetype.is_dir() {
1670 /// # Ok::<_, std::io::Error>(())
1673 #[clippy::version = "1.42.0"]
1674 pub FILETYPE_IS_FILE,
1676 "`FileType::is_file` is not recommended to test for readable file type"
1679 declare_clippy_lint! {
1680 /// ### What it does
1681 /// Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1683 /// ### Why is this bad?
1684 /// Readability, this can be written more concisely as
1689 /// # let opt = Some("".to_string());
1690 /// opt.as_ref().map(String::as_str)
1693 /// Can be written as
1695 /// # let opt = Some("".to_string());
1699 #[clippy::version = "1.42.0"]
1700 pub OPTION_AS_REF_DEREF,
1702 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1705 declare_clippy_lint! {
1706 /// ### What it does
1707 /// Checks for usage of `iter().next()` on a Slice or an Array
1709 /// ### Why is this bad?
1710 /// These can be shortened into `.get()`
1714 /// # let a = [1, 2, 3];
1715 /// # let b = vec![1, 2, 3];
1716 /// a[2..].iter().next();
1717 /// b.iter().next();
1719 /// should be written as:
1721 /// # let a = [1, 2, 3];
1722 /// # let b = vec![1, 2, 3];
1726 #[clippy::version = "1.46.0"]
1727 pub ITER_NEXT_SLICE,
1729 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1732 declare_clippy_lint! {
1733 /// ### What it does
1734 /// Warns when using `push_str`/`insert_str` with a single-character string literal
1735 /// where `push`/`insert` with a `char` would work fine.
1737 /// ### Why is this bad?
1738 /// It's less clear that we are pushing a single character.
1742 /// # let mut string = String::new();
1743 /// string.insert_str(0, "R");
1744 /// string.push_str("R");
1749 /// # let mut string = String::new();
1750 /// string.insert(0, 'R');
1751 /// string.push('R');
1753 #[clippy::version = "1.49.0"]
1754 pub SINGLE_CHAR_ADD_STR,
1756 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1759 declare_clippy_lint! {
1760 /// ### What it does
1761 /// As the counterpart to `or_fun_call`, this lint looks for unnecessary
1762 /// lazily evaluated closures on `Option` and `Result`.
1764 /// This lint suggests changing the following functions, when eager evaluation results in
1766 /// - `unwrap_or_else` to `unwrap_or`
1767 /// - `and_then` to `and`
1768 /// - `or_else` to `or`
1769 /// - `get_or_insert_with` to `get_or_insert`
1770 /// - `ok_or_else` to `ok_or`
1772 /// ### Why is this bad?
1773 /// Using eager evaluation is shorter and simpler in some cases.
1775 /// ### Known problems
1776 /// It is possible, but not recommended for `Deref` and `Index` to have
1777 /// side effects. Eagerly evaluating them can change the semantics of the program.
1781 /// // example code where clippy issues a warning
1782 /// let opt: Option<u32> = None;
1784 /// opt.unwrap_or_else(|| 42);
1788 /// let opt: Option<u32> = None;
1790 /// opt.unwrap_or(42);
1792 #[clippy::version = "1.48.0"]
1793 pub UNNECESSARY_LAZY_EVALUATIONS,
1795 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1798 declare_clippy_lint! {
1799 /// ### What it does
1800 /// Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1802 /// ### Why is this bad?
1803 /// Using `try_for_each` instead is more readable and idiomatic.
1807 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1811 /// (0..3).try_for_each(|t| Err(t));
1813 #[clippy::version = "1.49.0"]
1814 pub MAP_COLLECT_RESULT_UNIT,
1816 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1819 declare_clippy_lint! {
1820 /// ### What it does
1821 /// Checks for `from_iter()` function calls on types that implement the `FromIterator`
1824 /// ### Why is this bad?
1825 /// It is recommended style to use collect. See
1826 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1830 /// let five_fives = std::iter::repeat(5).take(5);
1832 /// let v = Vec::from_iter(five_fives);
1834 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1838 /// let five_fives = std::iter::repeat(5).take(5);
1840 /// let v: Vec<i32> = five_fives.collect();
1842 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1844 #[clippy::version = "1.49.0"]
1845 pub FROM_ITER_INSTEAD_OF_COLLECT,
1847 "use `.collect()` instead of `::from_iter()`"
1850 declare_clippy_lint! {
1851 /// ### What it does
1852 /// Checks for usage of `inspect().for_each()`.
1854 /// ### Why is this bad?
1855 /// It is the same as performing the computation
1856 /// inside `inspect` at the beginning of the closure in `for_each`.
1860 /// [1,2,3,4,5].iter()
1861 /// .inspect(|&x| println!("inspect the number: {}", x))
1862 /// .for_each(|&x| {
1863 /// assert!(x >= 0);
1866 /// Can be written as
1868 /// [1,2,3,4,5].iter()
1869 /// .for_each(|&x| {
1870 /// println!("inspect the number: {}", x);
1871 /// assert!(x >= 0);
1874 #[clippy::version = "1.51.0"]
1875 pub INSPECT_FOR_EACH,
1877 "using `.inspect().for_each()`, which can be replaced with `.for_each()`"
1880 declare_clippy_lint! {
1881 /// ### What it does
1882 /// Checks for usage of `filter_map(|x| x)`.
1884 /// ### Why is this bad?
1885 /// Readability, this can be written more concisely by using `flatten`.
1889 /// # let iter = vec![Some(1)].into_iter();
1890 /// iter.filter_map(|x| x);
1894 /// # let iter = vec![Some(1)].into_iter();
1897 #[clippy::version = "1.52.0"]
1898 pub FILTER_MAP_IDENTITY,
1900 "call to `filter_map` where `flatten` is sufficient"
1903 declare_clippy_lint! {
1904 /// ### What it does
1905 /// Checks for instances of `map(f)` where `f` is the identity function.
1907 /// ### Why is this bad?
1908 /// It can be written more concisely without the call to `map`.
1912 /// let x = [1, 2, 3];
1913 /// let y: Vec<_> = x.iter().map(|x| x).map(|x| 2*x).collect();
1917 /// let x = [1, 2, 3];
1918 /// let y: Vec<_> = x.iter().map(|x| 2*x).collect();
1920 #[clippy::version = "1.47.0"]
1923 "using iterator.map(|x| x)"
1926 declare_clippy_lint! {
1927 /// ### What it does
1928 /// Checks for the use of `.bytes().nth()`.
1930 /// ### Why is this bad?
1931 /// `.as_bytes().get()` is more efficient and more
1936 /// # #[allow(unused)]
1937 /// "Hello".bytes().nth(3);
1942 /// # #[allow(unused)]
1943 /// "Hello".as_bytes().get(3);
1945 #[clippy::version = "1.52.0"]
1948 "replace `.bytes().nth()` with `.as_bytes().get()`"
1951 declare_clippy_lint! {
1952 /// ### What it does
1953 /// Checks for the usage of `_.to_owned()`, `vec.to_vec()`, or similar when calling `_.clone()` would be clearer.
1955 /// ### Why is this bad?
1956 /// These methods do the same thing as `_.clone()` but may be confusing as
1957 /// to why we are calling `to_vec` on something that is already a `Vec` or calling `to_owned` on something that is already owned.
1961 /// let a = vec![1, 2, 3];
1962 /// let b = a.to_vec();
1963 /// let c = a.to_owned();
1967 /// let a = vec![1, 2, 3];
1968 /// let b = a.clone();
1969 /// let c = a.clone();
1971 #[clippy::version = "1.52.0"]
1974 "implicitly cloning a value by invoking a function on its dereferenced type"
1977 declare_clippy_lint! {
1978 /// ### What it does
1979 /// Checks for the use of `.iter().count()`.
1981 /// ### Why is this bad?
1982 /// `.len()` is more efficient and more
1987 /// # #![allow(unused)]
1988 /// let some_vec = vec![0, 1, 2, 3];
1990 /// some_vec.iter().count();
1991 /// &some_vec[..].iter().count();
1996 /// let some_vec = vec![0, 1, 2, 3];
1999 /// &some_vec[..].len();
2001 #[clippy::version = "1.52.0"]
2004 "replace `.iter().count()` with `.len()`"
2007 declare_clippy_lint! {
2008 /// ### What it does
2009 /// Checks for calls to [`splitn`]
2010 /// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
2011 /// related functions with either zero or one splits.
2013 /// ### Why is this bad?
2014 /// These calls don't actually split the value and are
2015 /// likely to be intended as a different number.
2020 /// for x in s.splitn(1, ":") {
2028 /// for x in s.splitn(2, ":") {
2032 #[clippy::version = "1.54.0"]
2033 pub SUSPICIOUS_SPLITN,
2035 "checks for `.splitn(0, ..)` and `.splitn(1, ..)`"
2038 declare_clippy_lint! {
2039 /// ### What it does
2040 /// Checks for manual implementations of `str::repeat`
2042 /// ### Why is this bad?
2043 /// These are both harder to read, as well as less performant.
2047 /// let x: String = std::iter::repeat('x').take(10).collect();
2052 /// let x: String = "x".repeat(10);
2054 #[clippy::version = "1.54.0"]
2055 pub MANUAL_STR_REPEAT,
2057 "manual implementation of `str::repeat`"
2060 declare_clippy_lint! {
2061 /// ### What it does
2062 /// Checks for usages of `str::splitn(2, _)`
2064 /// ### Why is this bad?
2065 /// `split_once` is both clearer in intent and slightly more efficient.
2069 /// let s = "key=value=add";
2070 /// let (key, value) = s.splitn(2, '=').next_tuple()?;
2071 /// let value = s.splitn(2, '=').nth(1)?;
2073 /// let mut parts = s.splitn(2, '=');
2074 /// let key = parts.next()?;
2075 /// let value = parts.next()?;
2080 /// let s = "key=value=add";
2081 /// let (key, value) = s.split_once('=')?;
2082 /// let value = s.split_once('=')?.1;
2084 /// let (key, value) = s.split_once('=')?;
2088 /// The multiple statement variant currently only detects `iter.next()?`/`iter.next().unwrap()`
2089 /// in two separate `let` statements that immediately follow the `splitn()`
2090 #[clippy::version = "1.57.0"]
2091 pub MANUAL_SPLIT_ONCE,
2093 "replace `.splitn(2, pat)` with `.split_once(pat)`"
2096 declare_clippy_lint! {
2097 /// ### What it does
2098 /// Checks for usages of `str::splitn` (or `str::rsplitn`) where using `str::split` would be the same.
2099 /// ### Why is this bad?
2100 /// The function `split` is simpler and there is no performance difference in these cases, considering
2101 /// that both functions return a lazy iterator.
2104 /// let str = "key=value=add";
2105 /// let _ = str.splitn(3, '=').next().unwrap();
2110 /// let str = "key=value=add";
2111 /// let _ = str.split('=').next().unwrap();
2113 #[clippy::version = "1.59.0"]
2114 pub NEEDLESS_SPLITN,
2116 "usages of `str::splitn` that can be replaced with `str::split`"
2119 declare_clippy_lint! {
2120 /// ### What it does
2121 /// Checks for unnecessary calls to [`ToOwned::to_owned`](https://doc.rust-lang.org/std/borrow/trait.ToOwned.html#tymethod.to_owned)
2122 /// and other `to_owned`-like functions.
2124 /// ### Why is this bad?
2125 /// The unnecessary calls result in useless allocations.
2127 /// ### Known problems
2128 /// `unnecessary_to_owned` can falsely trigger if `IntoIterator::into_iter` is applied to an
2129 /// owned copy of a resource and the resource is later used mutably. See
2130 /// [#8148](https://github.com/rust-lang/rust-clippy/issues/8148).
2134 /// let path = std::path::Path::new("x");
2135 /// foo(&path.to_string_lossy().to_string());
2136 /// fn foo(s: &str) {}
2140 /// let path = std::path::Path::new("x");
2141 /// foo(&path.to_string_lossy());
2142 /// fn foo(s: &str) {}
2144 #[clippy::version = "1.59.0"]
2145 pub UNNECESSARY_TO_OWNED,
2147 "unnecessary calls to `to_owned`-like functions"
2150 declare_clippy_lint! {
2151 /// ### What it does
2152 /// Checks for use of `.collect::<Vec<String>>().join("")` on iterators.
2154 /// ### Why is this bad?
2155 /// `.collect::<String>()` is more concise and might be more performant
2159 /// let vector = vec!["hello", "world"];
2160 /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<Vec<String>>().join("");
2161 /// println!("{}", output);
2163 /// The correct use would be:
2165 /// let vector = vec!["hello", "world"];
2166 /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
2167 /// println!("{}", output);
2169 /// ### Known problems
2170 /// While `.collect::<String>()` is sometimes more performant, there are cases where
2171 /// using `.collect::<String>()` over `.collect::<Vec<String>>().join("")`
2172 /// will prevent loop unrolling and will result in a negative performance impact.
2174 /// Additionally, differences have been observed between aarch64 and x86_64 assembly output,
2175 /// with aarch64 tending to producing faster assembly in more cases when using `.collect::<String>()`
2176 #[clippy::version = "1.61.0"]
2177 pub UNNECESSARY_JOIN,
2179 "using `.collect::<Vec<String>>().join(\"\")` on an iterator"
2182 declare_clippy_lint! {
2183 /// ### What it does
2184 /// Checks for no-op uses of `Option::{as_deref, as_deref_mut}`,
2185 /// for example, `Option<&T>::as_deref()` returns the same type.
2187 /// ### Why is this bad?
2188 /// Redundant code and improving readability.
2192 /// let a = Some(&1);
2193 /// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
2198 /// let a = Some(&1);
2201 #[clippy::version = "1.57.0"]
2202 pub NEEDLESS_OPTION_AS_DEREF,
2204 "no-op use of `deref` or `deref_mut` method to `Option`."
2207 declare_clippy_lint! {
2208 /// ### What it does
2209 /// Finds usages of [`char::is_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_digit) that
2210 /// can be replaced with [`is_ascii_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_digit) or
2211 /// [`is_ascii_hexdigit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_hexdigit).
2213 /// ### Why is this bad?
2214 /// `is_digit(..)` is slower and requires specifying the radix.
2218 /// let c: char = '6';
2224 /// let c: char = '6';
2225 /// c.is_ascii_digit();
2226 /// c.is_ascii_hexdigit();
2228 #[clippy::version = "1.62.0"]
2229 pub IS_DIGIT_ASCII_RADIX,
2231 "use of `char::is_digit(..)` with literal radix of 10 or 16"
2234 declare_clippy_lint! {
2235 /// ### What it does
2236 /// Checks for calling `take` function after `as_ref`.
2238 /// ### Why is this bad?
2239 /// Redundant code. `take` writes `None` to its argument.
2240 /// In this case the modification is useless as it's a temporary that cannot be read from afterwards.
2244 /// let x = Some(3);
2245 /// x.as_ref().take();
2249 /// let x = Some(3);
2252 #[clippy::version = "1.62.0"]
2253 pub NEEDLESS_OPTION_TAKE,
2255 "using `.as_ref().take()` on a temporary value"
2258 declare_clippy_lint! {
2259 /// ### What it does
2260 /// Checks for `replace` statements which have no effect.
2262 /// ### Why is this bad?
2263 /// It's either a mistake or confusing.
2267 /// "1234".replace("12", "12");
2268 /// "1234".replacen("12", "12", 1);
2270 #[clippy::version = "1.62.0"]
2271 pub NO_EFFECT_REPLACE,
2273 "replace with no effect"
2276 declare_clippy_lint! {
2277 /// ### What it does
2278 /// Checks for usages of `.then_some(..).unwrap_or(..)`
2280 /// ### Why is this bad?
2281 /// This can be written more clearly with `if .. else ..`
2284 /// This lint currently only looks for usages of
2285 /// `.then_some(..).unwrap_or(..)`, but will be expanded
2286 /// to account for similar patterns.
2291 /// x.then_some("a").unwrap_or("b");
2296 /// if x { "a" } else { "b" };
2298 #[clippy::version = "1.64.0"]
2299 pub OBFUSCATED_IF_ELSE,
2301 "use of `.then_some(..).unwrap_or(..)` can be written \
2302 more clearly with `if .. else ..`"
2305 pub struct Methods {
2306 avoid_breaking_exported_api: bool,
2307 msrv: Option<RustcVersion>,
2308 allow_expect_in_tests: bool,
2309 allow_unwrap_in_tests: bool,
2315 avoid_breaking_exported_api: bool,
2316 msrv: Option<RustcVersion>,
2317 allow_expect_in_tests: bool,
2318 allow_unwrap_in_tests: bool,
2321 avoid_breaking_exported_api,
2323 allow_expect_in_tests,
2324 allow_unwrap_in_tests,
2329 impl_lint_pass!(Methods => [
2332 SHOULD_IMPLEMENT_TRAIT,
2333 WRONG_SELF_CONVENTION,
2335 UNWRAP_OR_ELSE_DEFAULT,
2337 RESULT_MAP_OR_INTO_OPTION,
2339 BIND_INSTEAD_OF_MAP,
2348 ITER_OVEREAGER_CLONED,
2349 CLONED_INSTEAD_OF_COPIED,
2351 INEFFICIENT_TO_STRING,
2353 SINGLE_CHAR_PATTERN,
2354 SINGLE_CHAR_ADD_STR,
2358 FILTER_MAP_IDENTITY,
2366 ITERATOR_STEP_BY_ZERO,
2375 STRING_EXTEND_CHARS,
2376 ITER_CLONED_COLLECT,
2380 UNNECESSARY_FILTER_MAP,
2381 UNNECESSARY_FIND_MAP,
2384 UNINIT_ASSUMED_INIT,
2385 MANUAL_SATURATING_ARITHMETIC,
2388 OPTION_AS_REF_DEREF,
2389 UNNECESSARY_LAZY_EVALUATIONS,
2390 MAP_COLLECT_RESULT_UNIT,
2391 FROM_ITER_INSTEAD_OF_COLLECT,
2399 UNNECESSARY_TO_OWNED,
2402 NEEDLESS_OPTION_AS_DEREF,
2403 IS_DIGIT_ASCII_RADIX,
2404 NEEDLESS_OPTION_TAKE,
2409 /// Extracts a method call name, args, and `Span` of the method name.
2410 fn method_call<'tcx>(recv: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx str, &'tcx [hir::Expr<'tcx>], Span)> {
2411 if let ExprKind::MethodCall(path, args, _) = recv.kind {
2412 if !args.iter().any(|e| e.span.from_expansion()) {
2413 let name = path.ident.name.as_str();
2414 return Some((name, args, path.ident.span));
2420 impl<'tcx> LateLintPass<'tcx> for Methods {
2421 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
2422 if expr.span.from_expansion() {
2426 self.check_methods(cx, expr);
2429 hir::ExprKind::Call(func, args) => {
2430 from_iter_instead_of_collect::check(cx, expr, args, func);
2432 hir::ExprKind::MethodCall(method_call, args, _) => {
2433 let method_span = method_call.ident.span;
2434 or_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2435 expect_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2436 clone_on_copy::check(cx, expr, method_call.ident.name, args);
2437 clone_on_ref_ptr::check(cx, expr, method_call.ident.name, args);
2438 inefficient_to_string::check(cx, expr, method_call.ident.name, args);
2439 single_char_add_str::check(cx, expr, args);
2440 into_iter_on_ref::check(cx, expr, method_span, method_call.ident.name, args);
2441 single_char_pattern::check(cx, expr, method_call.ident.name, args);
2442 unnecessary_to_owned::check(cx, expr, method_call.ident.name, args, self.msrv);
2444 hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
2445 let mut info = BinaryExprInfo {
2449 eq: op.node == hir::BinOpKind::Eq,
2451 lint_binary_expr_with_method_call(cx, &mut info);
2457 #[allow(clippy::too_many_lines)]
2458 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
2459 if in_external_macro(cx.sess(), impl_item.span) {
2462 let name = impl_item.ident.name.as_str();
2463 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
2464 let item = cx.tcx.hir().expect_item(parent);
2465 let self_ty = cx.tcx.type_of(item.def_id);
2467 let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
2469 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
2470 if let Some(first_arg) = iter_input_pats(sig.decl, cx.tcx.hir().body(id)).next();
2472 let method_sig = cx.tcx.fn_sig(impl_item.def_id);
2473 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
2475 let first_arg_ty = method_sig.inputs().iter().next();
2477 // check conventions w.r.t. conversion method names and predicates
2478 if let Some(first_arg_ty) = first_arg_ty;
2481 // if this impl block implements a trait, lint in trait definition instead
2482 if !implements_trait && cx.access_levels.is_exported(impl_item.def_id) {
2483 // check missing trait implementations
2484 for method_config in &TRAIT_METHODS {
2485 if name == method_config.method_name &&
2486 sig.decl.inputs.len() == method_config.param_count &&
2487 method_config.output_type.matches(&sig.decl.output) &&
2488 method_config.self_kind.matches(cx, self_ty, *first_arg_ty) &&
2489 fn_header_equals(method_config.fn_header, sig.header) &&
2490 method_config.lifetime_param_cond(impl_item)
2494 SHOULD_IMPLEMENT_TRAIT,
2497 "method `{}` can be confused for the standard trait method `{}::{}`",
2498 method_config.method_name,
2499 method_config.trait_name,
2500 method_config.method_name
2504 "consider implementing the trait `{}` or choosing a less ambiguous method name",
2505 method_config.trait_name
2512 if sig.decl.implicit_self.has_implicit_self()
2513 && !(self.avoid_breaking_exported_api
2514 && cx.access_levels.is_exported(impl_item.def_id))
2516 wrong_self_convention::check(
2529 // if this impl block implements a trait, lint in trait definition instead
2530 if implements_trait {
2534 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
2535 let ret_ty = return_ty(cx, impl_item.hir_id());
2537 // walk the return type and check for Self (this does not check associated types)
2538 if let Some(self_adt) = self_ty.ty_adt_def() {
2539 if contains_adt_constructor(ret_ty, self_adt) {
2542 } else if contains_ty(ret_ty, self_ty) {
2546 // if return type is impl trait, check the associated types
2547 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
2548 // one of the associated types must be Self
2549 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
2550 if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
2551 let assoc_ty = match projection_predicate.term {
2552 ty::Term::Ty(ty) => ty,
2553 ty::Term::Const(_c) => continue,
2555 // walk the associated type and check for Self
2556 if let Some(self_adt) = self_ty.ty_adt_def() {
2557 if contains_adt_constructor(assoc_ty, self_adt) {
2560 } else if contains_ty(assoc_ty, self_ty) {
2567 if name == "new" && ret_ty != self_ty {
2572 "methods called `new` usually return `Self`",
2578 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
2579 if in_external_macro(cx.tcx.sess, item.span) {
2584 if let TraitItemKind::Fn(ref sig, _) = item.kind;
2585 if sig.decl.implicit_self.has_implicit_self();
2586 if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
2589 let first_arg_span = first_arg_ty.span;
2590 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
2591 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2592 wrong_self_convention::check(
2594 item.ident.name.as_str(),
2605 if item.ident.name == sym::new;
2606 if let TraitItemKind::Fn(_, _) = item.kind;
2607 let ret_ty = return_ty(cx, item.hir_id());
2608 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2609 if !contains_ty(ret_ty, self_ty);
2616 "methods called `new` usually return `Self`",
2622 extract_msrv_attr!(LateContext);
2626 #[allow(clippy::too_many_lines)]
2627 fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
2628 if let Some((name, [recv, args @ ..], span)) = method_call(expr) {
2629 match (name, args) {
2630 ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
2631 zst_offset::check(cx, expr, recv);
2633 ("and_then", [arg]) => {
2634 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, recv, arg);
2635 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, recv, arg);
2636 if !biom_option_linted && !biom_result_linted {
2637 unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
2640 ("as_deref" | "as_deref_mut", []) => {
2641 needless_option_as_deref::check(cx, expr, recv, name);
2643 ("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
2644 ("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
2645 ("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
2646 ("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span, self.msrv),
2647 ("collect", []) => match method_call(recv) {
2648 Some((name @ ("cloned" | "copied"), [recv2], _)) => {
2649 iter_cloned_collect::check(cx, name, expr, recv2);
2651 Some(("map", [m_recv, m_arg], _)) => {
2652 map_collect_result_unit::check(cx, expr, m_recv, m_arg, recv);
2654 Some(("take", [take_self_arg, take_arg], _)) => {
2655 if meets_msrv(self.msrv, msrvs::STR_REPEAT) {
2656 manual_str_repeat::check(cx, expr, recv, take_self_arg, take_arg);
2661 ("count", []) => match method_call(recv) {
2662 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, true, false),
2663 Some((name2 @ ("into_iter" | "iter" | "iter_mut"), [recv2], _)) => {
2664 iter_count::check(cx, expr, recv2, name2);
2666 Some(("map", [_, arg], _)) => suspicious_map::check(cx, expr, recv, arg),
2669 ("drain", [arg]) => {
2670 iter_with_drain::check(cx, expr, recv, span, arg);
2672 ("expect", [_]) => match method_call(recv) {
2673 Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
2674 Some(("err", [recv], err_span)) => err_expect::check(cx, expr, recv, self.msrv, span, err_span),
2675 _ => expect_used::check(cx, expr, recv, self.allow_expect_in_tests),
2677 ("extend", [arg]) => {
2678 string_extend_chars::check(cx, expr, recv, arg);
2679 extend_with_drain::check(cx, expr, recv, arg);
2681 ("filter_map", [arg]) => {
2682 unnecessary_filter_map::check(cx, expr, arg, name);
2683 filter_map_identity::check(cx, expr, arg, span);
2685 ("find_map", [arg]) => {
2686 unnecessary_filter_map::check(cx, expr, arg, name);
2688 ("flat_map", [arg]) => {
2689 flat_map_identity::check(cx, expr, arg, span);
2690 flat_map_option::check(cx, expr, arg, span);
2692 ("flatten", []) => match method_call(recv) {
2693 Some(("map", [recv, map_arg], map_span)) => map_flatten::check(cx, expr, recv, map_arg, map_span),
2694 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, true),
2697 ("fold", [init, acc]) => unnecessary_fold::check(cx, expr, init, acc, span),
2698 ("for_each", [_]) => {
2699 if let Some(("inspect", [_, _], span2)) = method_call(recv) {
2700 inspect_for_each::check(cx, expr, span2);
2703 ("get", [arg]) => get_last_with_len::check(cx, expr, recv, arg),
2704 ("get_or_insert_with", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "get_or_insert"),
2705 ("is_file", []) => filetype_is_file::check(cx, expr, recv),
2706 ("is_digit", [radix]) => is_digit_ascii_radix::check(cx, expr, recv, radix, self.msrv),
2707 ("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
2708 ("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
2709 ("join", [join_arg]) => {
2710 if let Some(("collect", _, span)) = method_call(recv) {
2711 unnecessary_join::check(cx, expr, recv, join_arg, span);
2714 ("last", []) | ("skip", [_]) => {
2715 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2716 if let ("cloned", []) = (name2, args2) {
2717 iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
2721 (name @ ("map" | "map_err"), [m_arg]) => {
2722 if let Some((name, [recv2, args @ ..], span2)) = method_call(recv) {
2723 match (name, args) {
2724 ("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, self.msrv),
2725 ("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, self.msrv),
2726 ("filter", [f_arg]) => {
2727 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
2729 ("find", [f_arg]) => {
2730 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, true);
2735 map_identity::check(cx, expr, recv, m_arg, name, span);
2737 ("map_or", [def, map]) => option_map_or_none::check(cx, expr, recv, def, map),
2739 if let Some((name2, [recv2, args2 @ ..], _)) = method_call(recv) {
2740 match (name2, args2) {
2741 ("cloned", []) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
2742 ("filter", [arg]) => filter_next::check(cx, expr, recv2, arg),
2743 ("filter_map", [arg]) => filter_map_next::check(cx, expr, recv2, arg, self.msrv),
2744 ("iter", []) => iter_next_slice::check(cx, expr, recv2),
2745 ("skip", [arg]) => iter_skip_next::check(cx, expr, recv2, arg),
2746 ("skip_while", [_]) => skip_while_next::check(cx, expr),
2751 ("nth", [n_arg]) => match method_call(recv) {
2752 Some(("bytes", [recv2], _)) => bytes_nth::check(cx, expr, recv2, n_arg),
2753 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
2754 Some(("iter", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, false),
2755 Some(("iter_mut", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, true),
2756 _ => iter_nth_zero::check(cx, expr, recv, n_arg),
2758 ("ok_or_else", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "ok_or"),
2759 ("or_else", [arg]) => {
2760 if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, recv, arg) {
2761 unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
2764 ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
2765 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2766 suspicious_splitn::check(cx, name, expr, recv, count);
2767 str_splitn::check(cx, name, expr, recv, pat_arg, count, self.msrv);
2770 ("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
2771 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2772 suspicious_splitn::check(cx, name, expr, recv, count);
2775 ("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
2776 ("take", [_arg]) => {
2777 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2778 if let ("cloned", []) = (name2, args2) {
2779 iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
2783 ("take", []) => needless_option_take::check(cx, expr, recv),
2784 ("then", [arg]) => {
2785 if !meets_msrv(self.msrv, msrvs::BOOL_THEN_SOME) {
2788 unnecessary_lazy_eval::check(cx, expr, recv, arg, "then_some");
2790 ("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
2791 implicit_clone::check(cx, name, expr, recv);
2794 match method_call(recv) {
2795 Some(("get", [recv, get_arg], _)) => {
2796 get_unwrap::check(cx, expr, recv, get_arg, false);
2798 Some(("get_mut", [recv, get_arg], _)) => {
2799 get_unwrap::check(cx, expr, recv, get_arg, true);
2801 Some(("or", [recv, or_arg], or_span)) => {
2802 or_then_unwrap::check(cx, expr, recv, or_arg, or_span);
2806 unwrap_used::check(cx, expr, recv, self.allow_unwrap_in_tests);
2808 ("unwrap_or", [u_arg]) => match method_call(recv) {
2809 Some((arith @ ("checked_add" | "checked_sub" | "checked_mul"), [lhs, rhs], _)) => {
2810 manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, &arith["checked_".len()..]);
2812 Some(("map", [m_recv, m_arg], span)) => {
2813 option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span);
2815 Some(("then_some", [t_recv, t_arg], _)) => {
2816 obfuscated_if_else::check(cx, expr, t_recv, t_arg, u_arg);
2820 ("unwrap_or_else", [u_arg]) => match method_call(recv) {
2821 Some(("map", [recv, map_arg], _))
2822 if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, self.msrv) => {},
2824 unwrap_or_else_default::check(cx, expr, recv, u_arg);
2825 unnecessary_lazy_eval::check(cx, expr, recv, u_arg, "unwrap_or");
2828 ("replace" | "replacen", [arg1, arg2] | [arg1, arg2, _]) => {
2829 no_effect_replace::check(cx, expr, arg1, arg2);
2837 fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, is_some: bool) {
2838 if let Some((name @ ("find" | "position" | "rposition"), [f_recv, arg], span)) = method_call(recv) {
2839 search_is_some::check(cx, expr, name, is_some, f_recv, arg, recv, span);
2843 /// Used for `lint_binary_expr_with_method_call`.
2844 #[derive(Copy, Clone)]
2845 struct BinaryExprInfo<'a> {
2846 expr: &'a hir::Expr<'a>,
2847 chain: &'a hir::Expr<'a>,
2848 other: &'a hir::Expr<'a>,
2852 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2853 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
2854 macro_rules! lint_with_both_lhs_and_rhs {
2855 ($func:expr, $cx:expr, $info:ident) => {
2856 if !$func($cx, $info) {
2857 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2858 if $func($cx, $info) {
2865 lint_with_both_lhs_and_rhs!(chars_next_cmp::check, cx, info);
2866 lint_with_both_lhs_and_rhs!(chars_last_cmp::check, cx, info);
2867 lint_with_both_lhs_and_rhs!(chars_next_cmp_with_unwrap::check, cx, info);
2868 lint_with_both_lhs_and_rhs!(chars_last_cmp_with_unwrap::check, cx, info);
2871 const FN_HEADER: hir::FnHeader = hir::FnHeader {
2872 unsafety: hir::Unsafety::Normal,
2873 constness: hir::Constness::NotConst,
2874 asyncness: hir::IsAsync::NotAsync,
2875 abi: rustc_target::spec::abi::Abi::Rust,
2878 struct ShouldImplTraitCase {
2879 trait_name: &'static str,
2880 method_name: &'static str,
2882 fn_header: hir::FnHeader,
2883 // implicit self kind expected (none, self, &self, ...)
2884 self_kind: SelfKind,
2885 // checks against the output type
2886 output_type: OutType,
2887 // certain methods with explicit lifetimes can't implement the equivalent trait method
2888 lint_explicit_lifetime: bool,
2890 impl ShouldImplTraitCase {
2892 trait_name: &'static str,
2893 method_name: &'static str,
2895 fn_header: hir::FnHeader,
2896 self_kind: SelfKind,
2897 output_type: OutType,
2898 lint_explicit_lifetime: bool,
2899 ) -> ShouldImplTraitCase {
2900 ShouldImplTraitCase {
2907 lint_explicit_lifetime,
2911 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
2912 self.lint_explicit_lifetime
2913 || !impl_item.generics.params.iter().any(|p| {
2916 hir::GenericParamKind::Lifetime {
2917 kind: hir::LifetimeParamKind::Explicit
2925 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
2926 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2927 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2928 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2929 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2930 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2931 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2932 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2933 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2934 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2935 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2936 // FIXME: default doesn't work
2937 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
2938 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2939 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2940 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2941 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
2942 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
2943 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2944 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2945 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
2946 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2947 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2948 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2949 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2950 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2951 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
2952 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2953 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2954 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2955 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2956 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2959 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
2968 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2969 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2970 if ty == parent_ty {
2972 } else if ty.is_box() {
2973 ty.boxed_ty() == parent_ty
2974 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
2975 if let ty::Adt(_, substs) = ty.kind() {
2976 substs.types().next().map_or(false, |t| t == parent_ty)
2985 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2986 if let ty::Ref(_, t, m) = *ty.kind() {
2987 return m == mutability && t == parent_ty;
2990 let trait_path = match mutability {
2991 hir::Mutability::Not => &paths::ASREF_TRAIT,
2992 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
2995 let trait_def_id = match get_trait_def_id(cx, trait_path) {
2997 None => return false,
2999 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3002 fn matches_none<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3003 !matches_value(cx, parent_ty, ty)
3004 && !matches_ref(cx, hir::Mutability::Not, parent_ty, ty)
3005 && !matches_ref(cx, hir::Mutability::Mut, parent_ty, ty)
3009 Self::Value => matches_value(cx, parent_ty, ty),
3010 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3011 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3012 Self::No => matches_none(cx, parent_ty, ty),
3017 fn description(self) -> &'static str {
3019 Self::Value => "`self` by value",
3020 Self::Ref => "`self` by reference",
3021 Self::RefMut => "`self` by mutable reference",
3022 Self::No => "no `self`",
3027 #[derive(Clone, Copy)]
3036 fn matches(self, ty: &hir::FnRetTy<'_>) -> bool {
3037 let is_unit = |ty: &hir::Ty<'_>| matches!(ty.kind, hir::TyKind::Tup(&[]));
3039 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3040 (Self::Unit, &hir::FnRetTy::Return(ty)) if is_unit(ty) => true,
3041 (Self::Bool, &hir::FnRetTy::Return(ty)) if is_bool(ty) => true,
3042 (Self::Any, &hir::FnRetTy::Return(ty)) if !is_unit(ty) => true,
3043 (Self::Ref, &hir::FnRetTy::Return(ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3049 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3050 if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
3051 matches!(path.res, Res::PrimTy(PrimTy::Bool))
3057 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
3058 expected.constness == actual.constness
3059 && expected.unsafety == actual.unsafety
3060 && expected.asyncness == actual.asyncness