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);
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 /// If [expect_used](#expect_used) is enabled, instead:
210 /// # let option = Some(1);
211 /// # let result: Result<usize, ()> = Ok(1);
218 #[clippy::version = "1.45.0"]
221 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
224 declare_clippy_lint! {
226 /// Checks for `.expect()` calls on `Option`s and `Result`s.
228 /// ### Why is this bad?
229 /// Usually it is better to handle the `None` or `Err` case.
230 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
231 /// this lint is `Allow` by default.
233 /// `result.expect()` will let the thread panic on `Err`
234 /// values. Normally, you want to implement more sophisticated error handling,
235 /// and propagate errors upwards with `?` operator.
239 /// # let option = Some(1);
240 /// # let result: Result<usize, ()> = Ok(1);
241 /// option.expect("one");
242 /// result.expect("one");
247 /// # let option = Some(1);
248 /// # let result: Result<usize, ()> = Ok(1);
255 #[clippy::version = "1.45.0"]
258 "using `.expect()` on `Result` or `Option`, which might be better handled"
261 declare_clippy_lint! {
263 /// Checks for methods that should live in a trait
264 /// implementation of a `std` trait (see [llogiq's blog
265 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
266 /// information) instead of an inherent implementation.
268 /// ### Why is this bad?
269 /// Implementing the traits improve ergonomics for users of
270 /// the code, often with very little cost. Also people seeing a `mul(...)`
272 /// may expect `*` to work equally, so you should have good reason to disappoint
279 /// fn add(&self, other: &X) -> X {
285 #[clippy::version = "pre 1.29.0"]
286 pub SHOULD_IMPLEMENT_TRAIT,
288 "defining a method that should be implementing a std trait"
291 declare_clippy_lint! {
293 /// Checks for methods with certain name prefixes and which
294 /// doesn't match how self is taken. The actual rules are:
296 /// |Prefix |Postfix |`self` taken | `self` type |
297 /// |-------|------------|-------------------------------|--------------|
298 /// |`as_` | none |`&self` or `&mut self` | any |
299 /// |`from_`| none | none | any |
300 /// |`into_`| none |`self` | any |
301 /// |`is_` | none |`&mut self` or `&self` or none | any |
302 /// |`to_` | `_mut` |`&mut self` | any |
303 /// |`to_` | not `_mut` |`self` | `Copy` |
304 /// |`to_` | not `_mut` |`&self` | not `Copy` |
306 /// Note: Clippy doesn't trigger methods with `to_` prefix in:
307 /// - Traits definition.
308 /// Clippy can not tell if a type that implements a trait is `Copy` or not.
309 /// - Traits implementation, when `&self` is taken.
310 /// The method signature is controlled by the trait and often `&self` is required for all types that implement the trait
311 /// (see e.g. the `std::string::ToString` trait).
313 /// Clippy allows `Pin<&Self>` and `Pin<&mut Self>` if `&self` and `&mut self` is required.
315 /// Please find more info here:
316 /// https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv
318 /// ### Why is this bad?
319 /// Consistency breeds readability. If you follow the
320 /// conventions, your users won't be surprised that they, e.g., need to supply a
321 /// mutable reference to a `as_..` function.
327 /// fn as_str(self) -> &'static str {
333 #[clippy::version = "pre 1.29.0"]
334 pub WRONG_SELF_CONVENTION,
336 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
339 declare_clippy_lint! {
341 /// Checks for usage of `ok().expect(..)`.
343 /// ### Why is this bad?
344 /// Because you usually call `expect()` on the `Result`
345 /// directly to get a better error message.
347 /// ### Known problems
348 /// The error type needs to implement `Debug`
352 /// # let x = Ok::<_, ()>(());
353 /// x.ok().expect("why did I do this again?");
358 /// # let x = Ok::<_, ()>(());
359 /// x.expect("why did I do this again?");
361 #[clippy::version = "pre 1.29.0"]
364 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
367 declare_clippy_lint! {
369 /// Checks for `.err().expect()` calls on the `Result` type.
371 /// ### Why is this bad?
372 /// `.expect_err()` can be called directly to avoid the extra type conversion from `err()`.
376 /// let x: Result<u32, &str> = Ok(10);
377 /// x.err().expect("Testing err().expect()");
381 /// let x: Result<u32, &str> = Ok(10);
382 /// x.expect_err("Testing expect_err");
384 #[clippy::version = "1.62.0"]
387 r#"using `.err().expect("")` when `.expect_err("")` can be used"#
390 declare_clippy_lint! {
392 /// Checks for usages of `_.unwrap_or_else(Default::default)` on `Option` and
395 /// ### Why is this bad?
396 /// Readability, these can be written as `_.unwrap_or_default`, which is
397 /// simpler and more concise.
401 /// # let x = Some(1);
402 /// x.unwrap_or_else(Default::default);
403 /// x.unwrap_or_else(u32::default);
408 /// # let x = Some(1);
409 /// x.unwrap_or_default();
411 #[clippy::version = "1.56.0"]
412 pub UNWRAP_OR_ELSE_DEFAULT,
414 "using `.unwrap_or_else(Default::default)`, which is more succinctly expressed as `.unwrap_or_default()`"
417 declare_clippy_lint! {
419 /// Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
420 /// `result.map(_).unwrap_or_else(_)`.
422 /// ### Why is this bad?
423 /// Readability, these can be written more concisely (resp.) as
424 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
426 /// ### Known problems
427 /// The order of the arguments is not in execution order
431 /// # let option = Some(1);
432 /// # let result: Result<usize, ()> = Ok(1);
433 /// # fn some_function(foo: ()) -> usize { 1 }
434 /// option.map(|a| a + 1).unwrap_or(0);
435 /// result.map(|a| a + 1).unwrap_or_else(some_function);
440 /// # let option = Some(1);
441 /// # let result: Result<usize, ()> = Ok(1);
442 /// # fn some_function(foo: ()) -> usize { 1 }
443 /// option.map_or(0, |a| a + 1);
444 /// result.map_or_else(some_function, |a| a + 1);
446 #[clippy::version = "1.45.0"]
449 "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)`"
452 declare_clippy_lint! {
454 /// Checks for usage of `_.map_or(None, _)`.
456 /// ### Why is this bad?
457 /// Readability, this can be written more concisely as
460 /// ### Known problems
461 /// The order of the arguments is not in execution order.
465 /// # let opt = Some(1);
466 /// opt.map_or(None, |a| Some(a + 1));
471 /// # let opt = Some(1);
472 /// opt.and_then(|a| Some(a + 1));
474 #[clippy::version = "pre 1.29.0"]
475 pub OPTION_MAP_OR_NONE,
477 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
480 declare_clippy_lint! {
482 /// Checks for usage of `_.map_or(None, Some)`.
484 /// ### Why is this bad?
485 /// Readability, this can be written more concisely as
490 /// # let r: Result<u32, &str> = Ok(1);
491 /// assert_eq!(Some(1), r.map_or(None, Some));
496 /// # let r: Result<u32, &str> = Ok(1);
497 /// assert_eq!(Some(1), r.ok());
499 #[clippy::version = "1.44.0"]
500 pub RESULT_MAP_OR_INTO_OPTION,
502 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
505 declare_clippy_lint! {
507 /// Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
508 /// `_.or_else(|x| Err(y))`.
510 /// ### Why is this bad?
511 /// Readability, this can be written more concisely as
512 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
516 /// # fn opt() -> Option<&'static str> { Some("42") }
517 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
518 /// let _ = opt().and_then(|s| Some(s.len()));
519 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
520 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
523 /// The correct use would be:
526 /// # fn opt() -> Option<&'static str> { Some("42") }
527 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
528 /// let _ = opt().map(|s| s.len());
529 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
530 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
532 #[clippy::version = "1.45.0"]
533 pub BIND_INSTEAD_OF_MAP,
535 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
538 declare_clippy_lint! {
540 /// Checks for usage of `_.filter(_).next()`.
542 /// ### Why is this bad?
543 /// Readability, this can be written more concisely as
548 /// # let vec = vec![1];
549 /// vec.iter().filter(|x| **x == 0).next();
554 /// # let vec = vec![1];
555 /// vec.iter().find(|x| **x == 0);
557 #[clippy::version = "pre 1.29.0"]
560 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
563 declare_clippy_lint! {
565 /// Checks for usage of `_.skip_while(condition).next()`.
567 /// ### Why is this bad?
568 /// Readability, this can be written more concisely as
569 /// `_.find(!condition)`.
573 /// # let vec = vec![1];
574 /// vec.iter().skip_while(|x| **x == 0).next();
579 /// # let vec = vec![1];
580 /// vec.iter().find(|x| **x != 0);
582 #[clippy::version = "1.42.0"]
585 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
588 declare_clippy_lint! {
590 /// Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
592 /// ### Why is this bad?
593 /// Readability, this can be written more concisely as
594 /// `_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
598 /// let vec = vec![vec![1]];
599 /// let opt = Some(5);
601 /// vec.iter().map(|x| x.iter()).flatten();
602 /// opt.map(|x| Some(x * 2)).flatten();
607 /// # let vec = vec![vec![1]];
608 /// # let opt = Some(5);
609 /// vec.iter().flat_map(|x| x.iter());
610 /// opt.and_then(|x| Some(x * 2));
612 #[clippy::version = "1.31.0"]
615 "using combinations of `flatten` and `map` which can usually be written as a single method call"
618 declare_clippy_lint! {
620 /// Checks for usage of `_.filter(_).map(_)` that can be written more simply
621 /// as `filter_map(_)`.
623 /// ### Why is this bad?
624 /// Redundant code in the `filter` and `map` operations is poor style and
629 /// # #![allow(unused)]
631 /// .filter(|n| n.checked_add(1).is_some())
632 /// .map(|n| n.checked_add(1).unwrap());
637 /// # #[allow(unused)]
638 /// (0_i32..10).filter_map(|n| n.checked_add(1));
640 #[clippy::version = "1.51.0"]
641 pub MANUAL_FILTER_MAP,
643 "using `_.filter(_).map(_)` in a way that can be written more simply as `filter_map(_)`"
646 declare_clippy_lint! {
648 /// Checks for usage of `_.find(_).map(_)` that can be written more simply
649 /// as `find_map(_)`.
651 /// ### Why is this bad?
652 /// Redundant code in the `find` and `map` operations is poor style and
658 /// .find(|n| n.checked_add(1).is_some())
659 /// .map(|n| n.checked_add(1).unwrap());
664 /// (0_i32..10).find_map(|n| n.checked_add(1));
666 #[clippy::version = "1.51.0"]
669 "using `_.find(_).map(_)` in a way that can be written more simply as `find_map(_)`"
672 declare_clippy_lint! {
674 /// Checks for usage of `_.filter_map(_).next()`.
676 /// ### Why is this bad?
677 /// Readability, this can be written more concisely as
682 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
684 /// Can be written as
687 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
689 #[clippy::version = "1.36.0"]
692 "using combination of `filter_map` and `next` which can usually be written as a single method call"
695 declare_clippy_lint! {
697 /// Checks for usage of `flat_map(|x| x)`.
699 /// ### Why is this bad?
700 /// Readability, this can be written more concisely by using `flatten`.
704 /// # let iter = vec![vec![0]].into_iter();
705 /// iter.flat_map(|x| x);
707 /// Can be written as
709 /// # let iter = vec![vec![0]].into_iter();
712 #[clippy::version = "1.39.0"]
713 pub FLAT_MAP_IDENTITY,
715 "call to `flat_map` where `flatten` is sufficient"
718 declare_clippy_lint! {
720 /// Checks for an iterator or string search (such as `find()`,
721 /// `position()`, or `rposition()`) followed by a call to `is_some()` or `is_none()`.
723 /// ### Why is this bad?
724 /// Readability, this can be written more concisely as:
725 /// * `_.any(_)`, or `_.contains(_)` for `is_some()`,
726 /// * `!_.any(_)`, or `!_.contains(_)` for `is_none()`.
730 /// # #![allow(unused)]
731 /// let vec = vec![1];
732 /// vec.iter().find(|x| **x == 0).is_some();
734 /// "hello world".find("world").is_none();
739 /// let vec = vec![1];
740 /// vec.iter().any(|x| *x == 0);
742 /// # #[allow(unused)]
743 /// !"hello world".contains("world");
745 #[clippy::version = "pre 1.29.0"]
748 "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()`)"
751 declare_clippy_lint! {
753 /// Checks for usage of `.chars().next()` on a `str` to check
754 /// if it starts with a given char.
756 /// ### Why is this bad?
757 /// Readability, this can be written more concisely as
758 /// `_.starts_with(_)`.
762 /// let name = "foo";
763 /// if name.chars().next() == Some('_') {};
768 /// let name = "foo";
769 /// if name.starts_with('_') {};
771 #[clippy::version = "pre 1.29.0"]
774 "using `.chars().next()` to check if a string starts with a char"
777 declare_clippy_lint! {
779 /// Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
780 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
781 /// `unwrap_or_default` instead.
783 /// ### Why is this bad?
784 /// The function will always be called and potentially
785 /// allocate an object acting as the default.
787 /// ### Known problems
788 /// If the function has side-effects, not calling it will
789 /// change the semantic of the program, but you shouldn't rely on that anyway.
793 /// # let foo = Some(String::new());
794 /// foo.unwrap_or(String::new());
799 /// # let foo = Some(String::new());
800 /// foo.unwrap_or_else(String::new);
804 /// # let foo = Some(String::new());
805 /// foo.unwrap_or_default();
807 #[clippy::version = "pre 1.29.0"]
810 "using any `*or` method with a function call, which suggests `*or_else`"
813 declare_clippy_lint! {
815 /// Checks for `.or(…).unwrap()` calls to Options and Results.
817 /// ### Why is this bad?
818 /// You should use `.unwrap_or(…)` instead for clarity.
822 /// # let fallback = "fallback";
824 /// # type Error = &'static str;
825 /// # let result: Result<&str, Error> = Err("error");
826 /// let value = result.or::<Error>(Ok(fallback)).unwrap();
829 /// # let option: Option<&str> = None;
830 /// let value = option.or(Some(fallback)).unwrap();
834 /// # let fallback = "fallback";
836 /// # let result: Result<&str, &str> = Err("error");
837 /// let value = result.unwrap_or(fallback);
840 /// # let option: Option<&str> = None;
841 /// let value = option.unwrap_or(fallback);
843 #[clippy::version = "1.61.0"]
846 "checks for `.or(…).unwrap()` calls to Options and Results."
849 declare_clippy_lint! {
851 /// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
852 /// etc., and suggests to use `unwrap_or_else` instead
854 /// ### Why is this bad?
855 /// The function will always be called.
857 /// ### Known problems
858 /// If the function has side-effects, not calling it will
859 /// change the semantics of the program, but you shouldn't rely on that anyway.
863 /// # let foo = Some(String::new());
864 /// # let err_code = "418";
865 /// # let err_msg = "I'm a teapot";
866 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
870 /// # let foo = Some(String::new());
871 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
876 /// # let foo = Some(String::new());
877 /// # let err_code = "418";
878 /// # let err_msg = "I'm a teapot";
879 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
881 #[clippy::version = "pre 1.29.0"]
884 "using any `expect` method with a function call"
887 declare_clippy_lint! {
889 /// Checks for usage of `.clone()` on a `Copy` type.
891 /// ### Why is this bad?
892 /// The only reason `Copy` types implement `Clone` is for
893 /// generics, not for using the `clone` method on a concrete type.
899 #[clippy::version = "pre 1.29.0"]
902 "using `clone` on a `Copy` type"
905 declare_clippy_lint! {
907 /// Checks for usage of `.clone()` on a ref-counted pointer,
908 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
909 /// function syntax instead (e.g., `Rc::clone(foo)`).
911 /// ### Why is this bad?
912 /// Calling '.clone()' on an Rc, Arc, or Weak
913 /// can obscure the fact that only the pointer is being cloned, not the underlying
918 /// # use std::rc::Rc;
919 /// let x = Rc::new(1);
926 /// # use std::rc::Rc;
927 /// # let x = Rc::new(1);
930 #[clippy::version = "pre 1.29.0"]
931 pub CLONE_ON_REF_PTR,
933 "using 'clone' on a ref-counted pointer"
936 declare_clippy_lint! {
938 /// Checks for usage of `.clone()` on an `&&T`.
940 /// ### Why is this bad?
941 /// Cloning an `&&T` copies the inner `&T`, instead of
942 /// cloning the underlying `T`.
949 /// let z = y.clone();
950 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
953 #[clippy::version = "pre 1.29.0"]
954 pub CLONE_DOUBLE_REF,
956 "using `clone` on `&&T`"
959 declare_clippy_lint! {
961 /// Checks for usage of `.to_string()` on an `&&T` where
962 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
964 /// ### Why is this bad?
965 /// This bypasses the specialized implementation of
966 /// `ToString` and instead goes through the more expensive string formatting
971 /// // Generic implementation for `T: Display` is used (slow)
972 /// ["foo", "bar"].iter().map(|s| s.to_string());
974 /// // OK, the specialized impl is used
975 /// ["foo", "bar"].iter().map(|&s| s.to_string());
977 #[clippy::version = "1.40.0"]
978 pub INEFFICIENT_TO_STRING,
980 "using `to_string` on `&&T` where `T: ToString`"
983 declare_clippy_lint! {
985 /// Checks for `new` not returning a type that contains `Self`.
987 /// ### Why is this bad?
988 /// As a convention, `new` methods are used to make a new
989 /// instance of a type.
992 /// In an impl block:
995 /// # struct NotAFoo;
997 /// fn new() -> NotAFoo {
1005 /// struct Bar(Foo);
1007 /// // Bad. The type name must contain `Self`
1008 /// fn new() -> Bar {
1016 /// # struct FooError;
1018 /// // Good. Return type contains `Self`
1019 /// fn new() -> Result<Foo, FooError> {
1025 /// Or in a trait definition:
1027 /// pub trait Trait {
1028 /// // Bad. The type name must contain `Self`
1034 /// pub trait Trait {
1035 /// // Good. Return type contains `Self`
1036 /// fn new() -> Self;
1039 #[clippy::version = "pre 1.29.0"]
1040 pub NEW_RET_NO_SELF,
1042 "not returning type containing `Self` in a `new` method"
1045 declare_clippy_lint! {
1046 /// ### What it does
1047 /// Checks for string methods that receive a single-character
1048 /// `str` as an argument, e.g., `_.split("x")`.
1050 /// ### Why is this bad?
1051 /// Performing these methods using a `char` is faster than
1054 /// ### Known problems
1055 /// Does not catch multi-byte unicode characters.
1066 #[clippy::version = "pre 1.29.0"]
1067 pub SINGLE_CHAR_PATTERN,
1069 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
1072 declare_clippy_lint! {
1073 /// ### What it does
1074 /// Checks for calling `.step_by(0)` on iterators which panics.
1076 /// ### Why is this bad?
1077 /// This very much looks like an oversight. Use `panic!()` instead if you
1078 /// actually intend to panic.
1081 /// ```rust,should_panic
1082 /// for x in (0..100).step_by(0) {
1086 #[clippy::version = "pre 1.29.0"]
1087 pub ITERATOR_STEP_BY_ZERO,
1089 "using `Iterator::step_by(0)`, which will panic at runtime"
1092 declare_clippy_lint! {
1093 /// ### What it does
1094 /// Checks for indirect collection of populated `Option`
1096 /// ### Why is this bad?
1097 /// `Option` is like a collection of 0-1 things, so `flatten`
1098 /// automatically does this without suspicious-looking `unwrap` calls.
1102 /// let _ = std::iter::empty::<Option<i32>>().filter(Option::is_some).map(Option::unwrap);
1106 /// let _ = std::iter::empty::<Option<i32>>().flatten();
1108 #[clippy::version = "1.53.0"]
1109 pub OPTION_FILTER_MAP,
1111 "filtering `Option` for `Some` then force-unwrapping, which can be one type-safe operation"
1114 declare_clippy_lint! {
1115 /// ### What it does
1116 /// Checks for the use of `iter.nth(0)`.
1118 /// ### Why is this bad?
1119 /// `iter.next()` is equivalent to
1120 /// `iter.nth(0)`, as they both consume the next element,
1121 /// but is more readable.
1125 /// # use std::collections::HashSet;
1126 /// # let mut s = HashSet::new();
1128 /// let x = s.iter().nth(0);
1133 /// # use std::collections::HashSet;
1134 /// # let mut s = HashSet::new();
1136 /// let x = s.iter().next();
1138 #[clippy::version = "1.42.0"]
1141 "replace `iter.nth(0)` with `iter.next()`"
1144 declare_clippy_lint! {
1145 /// ### What it does
1146 /// Checks for use of `.iter().nth()` (and the related
1147 /// `.iter_mut().nth()`) on standard library types with *O*(1) element access.
1149 /// ### Why is this bad?
1150 /// `.get()` and `.get_mut()` are more efficient and more
1155 /// let some_vec = vec![0, 1, 2, 3];
1156 /// let bad_vec = some_vec.iter().nth(3);
1157 /// let bad_slice = &some_vec[..].iter().nth(3);
1159 /// The correct use would be:
1161 /// let some_vec = vec![0, 1, 2, 3];
1162 /// let bad_vec = some_vec.get(3);
1163 /// let bad_slice = &some_vec[..].get(3);
1165 #[clippy::version = "pre 1.29.0"]
1168 "using `.iter().nth()` on a standard library type with O(1) element access"
1171 declare_clippy_lint! {
1172 /// ### What it does
1173 /// Checks for use of `.skip(x).next()` on iterators.
1175 /// ### Why is this bad?
1176 /// `.nth(x)` is cleaner
1180 /// let some_vec = vec![0, 1, 2, 3];
1181 /// let bad_vec = some_vec.iter().skip(3).next();
1182 /// let bad_slice = &some_vec[..].iter().skip(3).next();
1184 /// The correct use would be:
1186 /// let some_vec = vec![0, 1, 2, 3];
1187 /// let bad_vec = some_vec.iter().nth(3);
1188 /// let bad_slice = &some_vec[..].iter().nth(3);
1190 #[clippy::version = "pre 1.29.0"]
1193 "using `.skip(x).next()` on an iterator"
1196 declare_clippy_lint! {
1197 /// ### What it does
1198 /// Checks for use of `.drain(..)` on `Vec` and `VecDeque` for iteration.
1200 /// ### Why is this bad?
1201 /// `.into_iter()` is simpler with better performance.
1205 /// # use std::collections::HashSet;
1206 /// let mut foo = vec![0, 1, 2, 3];
1207 /// let bar: HashSet<usize> = foo.drain(..).collect();
1211 /// # use std::collections::HashSet;
1212 /// let foo = vec![0, 1, 2, 3];
1213 /// let bar: HashSet<usize> = foo.into_iter().collect();
1215 #[clippy::version = "1.61.0"]
1216 pub ITER_WITH_DRAIN,
1218 "replace `.drain(..)` with `.into_iter()`"
1221 declare_clippy_lint! {
1222 /// ### What it does
1223 /// Checks for using `x.get(x.len() - 1)` instead of
1226 /// ### Why is this bad?
1227 /// Using `x.last()` is easier to read and has the same
1230 /// Note that using `x[x.len() - 1]` is semantically different from
1231 /// `x.last()`. Indexing into the array will panic on out-of-bounds
1232 /// accesses, while `x.get()` and `x.last()` will return `None`.
1234 /// There is another lint (get_unwrap) that covers the case of using
1235 /// `x.get(index).unwrap()` instead of `x[index]`.
1239 /// let x = vec![2, 3, 5];
1240 /// let last_element = x.get(x.len() - 1);
1245 /// let x = vec![2, 3, 5];
1246 /// let last_element = x.last();
1248 #[clippy::version = "1.37.0"]
1249 pub GET_LAST_WITH_LEN,
1251 "Using `x.get(x.len() - 1)` when `x.last()` is correct and simpler"
1254 declare_clippy_lint! {
1255 /// ### What it does
1256 /// Checks for use of `.get().unwrap()` (or
1257 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
1259 /// ### Why is this bad?
1260 /// Using the Index trait (`[]`) is more clear and more
1263 /// ### Known problems
1264 /// Not a replacement for error handling: Using either
1265 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
1266 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
1267 /// temporary placeholder for dealing with the `Option` type, then this does
1268 /// not mitigate the need for error handling. If there is a chance that `.get()`
1269 /// will be `None` in your program, then it is advisable that the `None` case
1270 /// is handled in a future refactor instead of using `.unwrap()` or the Index
1275 /// let mut some_vec = vec![0, 1, 2, 3];
1276 /// let last = some_vec.get(3).unwrap();
1277 /// *some_vec.get_mut(0).unwrap() = 1;
1279 /// The correct use would be:
1281 /// let mut some_vec = vec![0, 1, 2, 3];
1282 /// let last = some_vec[3];
1283 /// some_vec[0] = 1;
1285 #[clippy::version = "pre 1.29.0"]
1288 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
1291 declare_clippy_lint! {
1292 /// ### What it does
1293 /// Checks for occurrences where one vector gets extended instead of append
1295 /// ### Why is this bad?
1296 /// Using `append` instead of `extend` is more concise and faster
1300 /// let mut a = vec![1, 2, 3];
1301 /// let mut b = vec![4, 5, 6];
1303 /// a.extend(b.drain(..));
1308 /// let mut a = vec![1, 2, 3];
1309 /// let mut b = vec![4, 5, 6];
1311 /// a.append(&mut b);
1313 #[clippy::version = "1.55.0"]
1314 pub EXTEND_WITH_DRAIN,
1316 "using vec.append(&mut vec) to move the full range of a vector to another"
1319 declare_clippy_lint! {
1320 /// ### What it does
1321 /// Checks for the use of `.extend(s.chars())` where s is a
1322 /// `&str` or `String`.
1324 /// ### Why is this bad?
1325 /// `.push_str(s)` is clearer
1329 /// let abc = "abc";
1330 /// let def = String::from("def");
1331 /// let mut s = String::new();
1332 /// s.extend(abc.chars());
1333 /// s.extend(def.chars());
1335 /// The correct use would be:
1337 /// let abc = "abc";
1338 /// let def = String::from("def");
1339 /// let mut s = String::new();
1340 /// s.push_str(abc);
1341 /// s.push_str(&def);
1343 #[clippy::version = "pre 1.29.0"]
1344 pub STRING_EXTEND_CHARS,
1346 "using `x.extend(s.chars())` where s is a `&str` or `String`"
1349 declare_clippy_lint! {
1350 /// ### What it does
1351 /// Checks for the use of `.cloned().collect()` on slice to
1354 /// ### Why is this bad?
1355 /// `.to_vec()` is clearer
1359 /// let s = [1, 2, 3, 4, 5];
1360 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
1362 /// The better use would be:
1364 /// let s = [1, 2, 3, 4, 5];
1365 /// let s2: Vec<isize> = s.to_vec();
1367 #[clippy::version = "pre 1.29.0"]
1368 pub ITER_CLONED_COLLECT,
1370 "using `.cloned().collect()` on slice to create a `Vec`"
1373 declare_clippy_lint! {
1374 /// ### What it does
1375 /// Checks for usage of `_.chars().last()` or
1376 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1378 /// ### Why is this bad?
1379 /// Readability, this can be written more concisely as
1380 /// `_.ends_with(_)`.
1384 /// # let name = "_";
1385 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1390 /// # let name = "_";
1391 /// name.ends_with('_') || name.ends_with('-');
1393 #[clippy::version = "pre 1.29.0"]
1396 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1399 declare_clippy_lint! {
1400 /// ### What it does
1401 /// Checks for usage of `.as_ref()` or `.as_mut()` where the
1402 /// types before and after the call are the same.
1404 /// ### Why is this bad?
1405 /// The call is unnecessary.
1409 /// # fn do_stuff(x: &[i32]) {}
1410 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1411 /// do_stuff(x.as_ref());
1413 /// The correct use would be:
1415 /// # fn do_stuff(x: &[i32]) {}
1416 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1419 #[clippy::version = "pre 1.29.0"]
1422 "using `as_ref` where the types before and after the call are the same"
1425 declare_clippy_lint! {
1426 /// ### What it does
1427 /// Checks for using `fold` when a more succinct alternative exists.
1428 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1429 /// `sum` or `product`.
1431 /// ### Why is this bad?
1436 /// # #[allow(unused)]
1437 /// (0..3).fold(false, |acc, x| acc || x > 2);
1442 /// (0..3).any(|x| x > 2);
1444 #[clippy::version = "pre 1.29.0"]
1445 pub UNNECESSARY_FOLD,
1447 "using `fold` when a more succinct alternative exists"
1450 declare_clippy_lint! {
1451 /// ### What it does
1452 /// Checks for `filter_map` calls that could be replaced by `filter` or `map`.
1453 /// More specifically it checks if the closure provided is only performing one of the
1454 /// filter or map operations and suggests the appropriate option.
1456 /// ### Why is this bad?
1457 /// Complexity. The intent is also clearer if only a single
1458 /// operation is being performed.
1462 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1464 /// // As there is no transformation of the argument this could be written as:
1465 /// let _ = (0..3).filter(|&x| x > 2);
1469 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1471 /// // As there is no conditional check on the argument this could be written as:
1472 /// let _ = (0..4).map(|x| x + 1);
1474 #[clippy::version = "1.31.0"]
1475 pub UNNECESSARY_FILTER_MAP,
1477 "using `filter_map` when a more succinct alternative exists"
1480 declare_clippy_lint! {
1481 /// ### What it does
1482 /// Checks for `find_map` calls that could be replaced by `find` or `map`. More
1483 /// specifically it checks if the closure provided is only performing one of the
1484 /// find or map operations and suggests the appropriate option.
1486 /// ### Why is this bad?
1487 /// Complexity. The intent is also clearer if only a single
1488 /// operation is being performed.
1492 /// let _ = (0..3).find_map(|x| if x > 2 { Some(x) } else { None });
1494 /// // As there is no transformation of the argument this could be written as:
1495 /// let _ = (0..3).find(|&x| x > 2);
1499 /// let _ = (0..4).find_map(|x| Some(x + 1));
1501 /// // As there is no conditional check on the argument this could be written as:
1502 /// let _ = (0..4).map(|x| x + 1).next();
1504 #[clippy::version = "1.61.0"]
1505 pub UNNECESSARY_FIND_MAP,
1507 "using `find_map` when a more succinct alternative exists"
1510 declare_clippy_lint! {
1511 /// ### What it does
1512 /// Checks for `into_iter` calls on references which should be replaced by `iter`
1515 /// ### Why is this bad?
1516 /// Readability. Calling `into_iter` on a reference will not move out its
1517 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1518 /// `iter_mut` directly.
1522 /// # let vec = vec![3, 4, 5];
1523 /// (&vec).into_iter();
1528 /// # let vec = vec![3, 4, 5];
1531 #[clippy::version = "1.32.0"]
1532 pub INTO_ITER_ON_REF,
1534 "using `.into_iter()` on a reference"
1537 declare_clippy_lint! {
1538 /// ### What it does
1539 /// Checks for calls to `map` followed by a `count`.
1541 /// ### Why is this bad?
1542 /// It looks suspicious. Maybe `map` was confused with `filter`.
1543 /// If the `map` call is intentional, this should be rewritten
1544 /// using `inspect`. Or, if you intend to drive the iterator to
1545 /// completion, you can just use `for_each` instead.
1549 /// let _ = (0..3).map(|x| x + 2).count();
1551 #[clippy::version = "1.39.0"]
1554 "suspicious usage of map"
1557 declare_clippy_lint! {
1558 /// ### What it does
1559 /// Checks for `MaybeUninit::uninit().assume_init()`.
1561 /// ### Why is this bad?
1562 /// For most types, this is undefined behavior.
1564 /// ### Known problems
1565 /// For now, we accept empty tuples and tuples / arrays
1566 /// of `MaybeUninit`. There may be other types that allow uninitialized
1567 /// data, but those are not yet rigorously defined.
1571 /// // Beware the UB
1572 /// use std::mem::MaybeUninit;
1574 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1577 /// Note that the following is OK:
1580 /// use std::mem::MaybeUninit;
1582 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1583 /// MaybeUninit::uninit().assume_init()
1586 #[clippy::version = "1.39.0"]
1587 pub UNINIT_ASSUMED_INIT,
1589 "`MaybeUninit::uninit().assume_init()`"
1592 declare_clippy_lint! {
1593 /// ### What it does
1594 /// Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1596 /// ### Why is this bad?
1597 /// These can be written simply with `saturating_add/sub` methods.
1601 /// # let y: u32 = 0;
1602 /// # let x: u32 = 100;
1603 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1604 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1607 /// can be written using dedicated methods for saturating addition/subtraction as:
1610 /// # let y: u32 = 0;
1611 /// # let x: u32 = 100;
1612 /// let add = x.saturating_add(y);
1613 /// let sub = x.saturating_sub(y);
1615 #[clippy::version = "1.39.0"]
1616 pub MANUAL_SATURATING_ARITHMETIC,
1618 "`.checked_add/sub(x).unwrap_or(MAX/MIN)`"
1621 declare_clippy_lint! {
1622 /// ### What it does
1623 /// Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1624 /// zero-sized types
1626 /// ### Why is this bad?
1627 /// This is a no-op, and likely unintended
1631 /// unsafe { (&() as *const ()).offset(1) };
1633 #[clippy::version = "1.41.0"]
1636 "Check for offset calculations on raw pointers to zero-sized types"
1639 declare_clippy_lint! {
1640 /// ### What it does
1641 /// Checks for `FileType::is_file()`.
1643 /// ### Why is this bad?
1644 /// When people testing a file type with `FileType::is_file`
1645 /// they are testing whether a path is something they can get bytes from. But
1646 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1647 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1652 /// let metadata = std::fs::metadata("foo.txt")?;
1653 /// let filetype = metadata.file_type();
1655 /// if filetype.is_file() {
1658 /// # Ok::<_, std::io::Error>(())
1662 /// should be written as:
1666 /// let metadata = std::fs::metadata("foo.txt")?;
1667 /// let filetype = metadata.file_type();
1669 /// if !filetype.is_dir() {
1672 /// # Ok::<_, std::io::Error>(())
1675 #[clippy::version = "1.42.0"]
1676 pub FILETYPE_IS_FILE,
1678 "`FileType::is_file` is not recommended to test for readable file type"
1681 declare_clippy_lint! {
1682 /// ### What it does
1683 /// Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1685 /// ### Why is this bad?
1686 /// Readability, this can be written more concisely as
1691 /// # let opt = Some("".to_string());
1692 /// opt.as_ref().map(String::as_str)
1695 /// Can be written as
1697 /// # let opt = Some("".to_string());
1701 #[clippy::version = "1.42.0"]
1702 pub OPTION_AS_REF_DEREF,
1704 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1707 declare_clippy_lint! {
1708 /// ### What it does
1709 /// Checks for usage of `iter().next()` on a Slice or an Array
1711 /// ### Why is this bad?
1712 /// These can be shortened into `.get()`
1716 /// # let a = [1, 2, 3];
1717 /// # let b = vec![1, 2, 3];
1718 /// a[2..].iter().next();
1719 /// b.iter().next();
1721 /// should be written as:
1723 /// # let a = [1, 2, 3];
1724 /// # let b = vec![1, 2, 3];
1728 #[clippy::version = "1.46.0"]
1729 pub ITER_NEXT_SLICE,
1731 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1734 declare_clippy_lint! {
1735 /// ### What it does
1736 /// Warns when using `push_str`/`insert_str` with a single-character string literal
1737 /// where `push`/`insert` with a `char` would work fine.
1739 /// ### Why is this bad?
1740 /// It's less clear that we are pushing a single character.
1744 /// # let mut string = String::new();
1745 /// string.insert_str(0, "R");
1746 /// string.push_str("R");
1751 /// # let mut string = String::new();
1752 /// string.insert(0, 'R');
1753 /// string.push('R');
1755 #[clippy::version = "1.49.0"]
1756 pub SINGLE_CHAR_ADD_STR,
1758 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1761 declare_clippy_lint! {
1762 /// ### What it does
1763 /// As the counterpart to `or_fun_call`, this lint looks for unnecessary
1764 /// lazily evaluated closures on `Option` and `Result`.
1766 /// This lint suggests changing the following functions, when eager evaluation results in
1768 /// - `unwrap_or_else` to `unwrap_or`
1769 /// - `and_then` to `and`
1770 /// - `or_else` to `or`
1771 /// - `get_or_insert_with` to `get_or_insert`
1772 /// - `ok_or_else` to `ok_or`
1774 /// ### Why is this bad?
1775 /// Using eager evaluation is shorter and simpler in some cases.
1777 /// ### Known problems
1778 /// It is possible, but not recommended for `Deref` and `Index` to have
1779 /// side effects. Eagerly evaluating them can change the semantics of the program.
1783 /// // example code where clippy issues a warning
1784 /// let opt: Option<u32> = None;
1786 /// opt.unwrap_or_else(|| 42);
1790 /// let opt: Option<u32> = None;
1792 /// opt.unwrap_or(42);
1794 #[clippy::version = "1.48.0"]
1795 pub UNNECESSARY_LAZY_EVALUATIONS,
1797 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1800 declare_clippy_lint! {
1801 /// ### What it does
1802 /// Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1804 /// ### Why is this bad?
1805 /// Using `try_for_each` instead is more readable and idiomatic.
1809 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1813 /// (0..3).try_for_each(|t| Err(t));
1815 #[clippy::version = "1.49.0"]
1816 pub MAP_COLLECT_RESULT_UNIT,
1818 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1821 declare_clippy_lint! {
1822 /// ### What it does
1823 /// Checks for `from_iter()` function calls on types that implement the `FromIterator`
1826 /// ### Why is this bad?
1827 /// It is recommended style to use collect. See
1828 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1832 /// let five_fives = std::iter::repeat(5).take(5);
1834 /// let v = Vec::from_iter(five_fives);
1836 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1840 /// let five_fives = std::iter::repeat(5).take(5);
1842 /// let v: Vec<i32> = five_fives.collect();
1844 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1846 #[clippy::version = "1.49.0"]
1847 pub FROM_ITER_INSTEAD_OF_COLLECT,
1849 "use `.collect()` instead of `::from_iter()`"
1852 declare_clippy_lint! {
1853 /// ### What it does
1854 /// Checks for usage of `inspect().for_each()`.
1856 /// ### Why is this bad?
1857 /// It is the same as performing the computation
1858 /// inside `inspect` at the beginning of the closure in `for_each`.
1862 /// [1,2,3,4,5].iter()
1863 /// .inspect(|&x| println!("inspect the number: {}", x))
1864 /// .for_each(|&x| {
1865 /// assert!(x >= 0);
1868 /// Can be written as
1870 /// [1,2,3,4,5].iter()
1871 /// .for_each(|&x| {
1872 /// println!("inspect the number: {}", x);
1873 /// assert!(x >= 0);
1876 #[clippy::version = "1.51.0"]
1877 pub INSPECT_FOR_EACH,
1879 "using `.inspect().for_each()`, which can be replaced with `.for_each()`"
1882 declare_clippy_lint! {
1883 /// ### What it does
1884 /// Checks for usage of `filter_map(|x| x)`.
1886 /// ### Why is this bad?
1887 /// Readability, this can be written more concisely by using `flatten`.
1891 /// # let iter = vec![Some(1)].into_iter();
1892 /// iter.filter_map(|x| x);
1896 /// # let iter = vec![Some(1)].into_iter();
1899 #[clippy::version = "1.52.0"]
1900 pub FILTER_MAP_IDENTITY,
1902 "call to `filter_map` where `flatten` is sufficient"
1905 declare_clippy_lint! {
1906 /// ### What it does
1907 /// Checks for instances of `map(f)` where `f` is the identity function.
1909 /// ### Why is this bad?
1910 /// It can be written more concisely without the call to `map`.
1914 /// let x = [1, 2, 3];
1915 /// let y: Vec<_> = x.iter().map(|x| x).map(|x| 2*x).collect();
1919 /// let x = [1, 2, 3];
1920 /// let y: Vec<_> = x.iter().map(|x| 2*x).collect();
1922 #[clippy::version = "1.47.0"]
1925 "using iterator.map(|x| x)"
1928 declare_clippy_lint! {
1929 /// ### What it does
1930 /// Checks for the use of `.bytes().nth()`.
1932 /// ### Why is this bad?
1933 /// `.as_bytes().get()` is more efficient and more
1938 /// # #[allow(unused)]
1939 /// "Hello".bytes().nth(3);
1944 /// # #[allow(unused)]
1945 /// "Hello".as_bytes().get(3);
1947 #[clippy::version = "1.52.0"]
1950 "replace `.bytes().nth()` with `.as_bytes().get()`"
1953 declare_clippy_lint! {
1954 /// ### What it does
1955 /// Checks for the usage of `_.to_owned()`, `vec.to_vec()`, or similar when calling `_.clone()` would be clearer.
1957 /// ### Why is this bad?
1958 /// These methods do the same thing as `_.clone()` but may be confusing as
1959 /// to why we are calling `to_vec` on something that is already a `Vec` or calling `to_owned` on something that is already owned.
1963 /// let a = vec![1, 2, 3];
1964 /// let b = a.to_vec();
1965 /// let c = a.to_owned();
1969 /// let a = vec![1, 2, 3];
1970 /// let b = a.clone();
1971 /// let c = a.clone();
1973 #[clippy::version = "1.52.0"]
1976 "implicitly cloning a value by invoking a function on its dereferenced type"
1979 declare_clippy_lint! {
1980 /// ### What it does
1981 /// Checks for the use of `.iter().count()`.
1983 /// ### Why is this bad?
1984 /// `.len()` is more efficient and more
1989 /// # #![allow(unused)]
1990 /// let some_vec = vec![0, 1, 2, 3];
1992 /// some_vec.iter().count();
1993 /// &some_vec[..].iter().count();
1998 /// let some_vec = vec![0, 1, 2, 3];
2001 /// &some_vec[..].len();
2003 #[clippy::version = "1.52.0"]
2006 "replace `.iter().count()` with `.len()`"
2009 declare_clippy_lint! {
2010 /// ### What it does
2011 /// Checks for calls to [`splitn`]
2012 /// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
2013 /// related functions with either zero or one splits.
2015 /// ### Why is this bad?
2016 /// These calls don't actually split the value and are
2017 /// likely to be intended as a different number.
2022 /// for x in s.splitn(1, ":") {
2030 /// for x in s.splitn(2, ":") {
2034 #[clippy::version = "1.54.0"]
2035 pub SUSPICIOUS_SPLITN,
2037 "checks for `.splitn(0, ..)` and `.splitn(1, ..)`"
2040 declare_clippy_lint! {
2041 /// ### What it does
2042 /// Checks for manual implementations of `str::repeat`
2044 /// ### Why is this bad?
2045 /// These are both harder to read, as well as less performant.
2049 /// let x: String = std::iter::repeat('x').take(10).collect();
2054 /// let x: String = "x".repeat(10);
2056 #[clippy::version = "1.54.0"]
2057 pub MANUAL_STR_REPEAT,
2059 "manual implementation of `str::repeat`"
2062 declare_clippy_lint! {
2063 /// ### What it does
2064 /// Checks for usages of `str::splitn(2, _)`
2066 /// ### Why is this bad?
2067 /// `split_once` is both clearer in intent and slightly more efficient.
2071 /// let s = "key=value=add";
2072 /// let (key, value) = s.splitn(2, '=').next_tuple()?;
2073 /// let value = s.splitn(2, '=').nth(1)?;
2075 /// let mut parts = s.splitn(2, '=');
2076 /// let key = parts.next()?;
2077 /// let value = parts.next()?;
2082 /// let s = "key=value=add";
2083 /// let (key, value) = s.split_once('=')?;
2084 /// let value = s.split_once('=')?.1;
2086 /// let (key, value) = s.split_once('=')?;
2090 /// The multiple statement variant currently only detects `iter.next()?`/`iter.next().unwrap()`
2091 /// in two separate `let` statements that immediately follow the `splitn()`
2092 #[clippy::version = "1.57.0"]
2093 pub MANUAL_SPLIT_ONCE,
2095 "replace `.splitn(2, pat)` with `.split_once(pat)`"
2098 declare_clippy_lint! {
2099 /// ### What it does
2100 /// Checks for usages of `str::splitn` (or `str::rsplitn`) where using `str::split` would be the same.
2101 /// ### Why is this bad?
2102 /// The function `split` is simpler and there is no performance difference in these cases, considering
2103 /// that both functions return a lazy iterator.
2106 /// let str = "key=value=add";
2107 /// let _ = str.splitn(3, '=').next().unwrap();
2112 /// let str = "key=value=add";
2113 /// let _ = str.split('=').next().unwrap();
2115 #[clippy::version = "1.59.0"]
2116 pub NEEDLESS_SPLITN,
2118 "usages of `str::splitn` that can be replaced with `str::split`"
2121 declare_clippy_lint! {
2122 /// ### What it does
2123 /// Checks for unnecessary calls to [`ToOwned::to_owned`](https://doc.rust-lang.org/std/borrow/trait.ToOwned.html#tymethod.to_owned)
2124 /// and other `to_owned`-like functions.
2126 /// ### Why is this bad?
2127 /// The unnecessary calls result in useless allocations.
2129 /// ### Known problems
2130 /// `unnecessary_to_owned` can falsely trigger if `IntoIterator::into_iter` is applied to an
2131 /// owned copy of a resource and the resource is later used mutably. See
2132 /// [#8148](https://github.com/rust-lang/rust-clippy/issues/8148).
2136 /// let path = std::path::Path::new("x");
2137 /// foo(&path.to_string_lossy().to_string());
2138 /// fn foo(s: &str) {}
2142 /// let path = std::path::Path::new("x");
2143 /// foo(&path.to_string_lossy());
2144 /// fn foo(s: &str) {}
2146 #[clippy::version = "1.59.0"]
2147 pub UNNECESSARY_TO_OWNED,
2149 "unnecessary calls to `to_owned`-like functions"
2152 declare_clippy_lint! {
2153 /// ### What it does
2154 /// Checks for use of `.collect::<Vec<String>>().join("")` on iterators.
2156 /// ### Why is this bad?
2157 /// `.collect::<String>()` is more concise and might be more performant
2161 /// let vector = vec!["hello", "world"];
2162 /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<Vec<String>>().join("");
2163 /// println!("{}", output);
2165 /// The correct use would be:
2167 /// let vector = vec!["hello", "world"];
2168 /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
2169 /// println!("{}", output);
2171 /// ### Known problems
2172 /// While `.collect::<String>()` is sometimes more performant, there are cases where
2173 /// using `.collect::<String>()` over `.collect::<Vec<String>>().join("")`
2174 /// will prevent loop unrolling and will result in a negative performance impact.
2176 /// Additionally, differences have been observed between aarch64 and x86_64 assembly output,
2177 /// with aarch64 tending to producing faster assembly in more cases when using `.collect::<String>()`
2178 #[clippy::version = "1.61.0"]
2179 pub UNNECESSARY_JOIN,
2181 "using `.collect::<Vec<String>>().join(\"\")` on an iterator"
2184 declare_clippy_lint! {
2185 /// ### What it does
2186 /// Checks for no-op uses of `Option::{as_deref, as_deref_mut}`,
2187 /// for example, `Option<&T>::as_deref()` returns the same type.
2189 /// ### Why is this bad?
2190 /// Redundant code and improving readability.
2194 /// let a = Some(&1);
2195 /// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
2200 /// let a = Some(&1);
2203 #[clippy::version = "1.57.0"]
2204 pub NEEDLESS_OPTION_AS_DEREF,
2206 "no-op use of `deref` or `deref_mut` method to `Option`."
2209 declare_clippy_lint! {
2210 /// ### What it does
2211 /// Finds usages of [`char::is_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_digit) that
2212 /// can be replaced with [`is_ascii_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_digit) or
2213 /// [`is_ascii_hexdigit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_hexdigit).
2215 /// ### Why is this bad?
2216 /// `is_digit(..)` is slower and requires specifying the radix.
2220 /// let c: char = '6';
2226 /// let c: char = '6';
2227 /// c.is_ascii_digit();
2228 /// c.is_ascii_hexdigit();
2230 #[clippy::version = "1.62.0"]
2231 pub IS_DIGIT_ASCII_RADIX,
2233 "use of `char::is_digit(..)` with literal radix of 10 or 16"
2236 declare_clippy_lint! {
2237 /// ### What it does
2238 /// Checks for calling `take` function after `as_ref`.
2240 /// ### Why is this bad?
2241 /// Redundant code. `take` writes `None` to its argument.
2242 /// In this case the modification is useless as it's a temporary that cannot be read from afterwards.
2246 /// let x = Some(3);
2247 /// x.as_ref().take();
2251 /// let x = Some(3);
2254 #[clippy::version = "1.62.0"]
2255 pub NEEDLESS_OPTION_TAKE,
2257 "using `.as_ref().take()` on a temporary value"
2260 declare_clippy_lint! {
2261 /// ### What it does
2262 /// Checks for `replace` statements which have no effect.
2264 /// ### Why is this bad?
2265 /// It's either a mistake or confusing.
2269 /// "1234".replace("12", "12");
2270 /// "1234".replacen("12", "12", 1);
2272 #[clippy::version = "1.62.0"]
2273 pub NO_EFFECT_REPLACE,
2275 "replace with no effect"
2278 declare_clippy_lint! {
2279 /// ### What it does
2280 /// Checks for usages of `.then_some(..).unwrap_or(..)`
2282 /// ### Why is this bad?
2283 /// This can be written more clearly with `if .. else ..`
2286 /// This lint currently only looks for usages of
2287 /// `.then_some(..).unwrap_or(..)`, but will be expanded
2288 /// to account for similar patterns.
2293 /// x.then_some("a").unwrap_or("b");
2298 /// if x { "a" } else { "b" };
2300 #[clippy::version = "1.64.0"]
2301 pub OBFUSCATED_IF_ELSE,
2303 "use of `.then_some(..).unwrap_or(..)` can be written \
2304 more clearly with `if .. else ..`"
2307 pub struct Methods {
2308 avoid_breaking_exported_api: bool,
2309 msrv: Option<RustcVersion>,
2310 allow_expect_in_tests: bool,
2311 allow_unwrap_in_tests: bool,
2317 avoid_breaking_exported_api: bool,
2318 msrv: Option<RustcVersion>,
2319 allow_expect_in_tests: bool,
2320 allow_unwrap_in_tests: bool,
2323 avoid_breaking_exported_api,
2325 allow_expect_in_tests,
2326 allow_unwrap_in_tests,
2331 impl_lint_pass!(Methods => [
2334 SHOULD_IMPLEMENT_TRAIT,
2335 WRONG_SELF_CONVENTION,
2337 UNWRAP_OR_ELSE_DEFAULT,
2339 RESULT_MAP_OR_INTO_OPTION,
2341 BIND_INSTEAD_OF_MAP,
2350 ITER_OVEREAGER_CLONED,
2351 CLONED_INSTEAD_OF_COPIED,
2353 INEFFICIENT_TO_STRING,
2355 SINGLE_CHAR_PATTERN,
2356 SINGLE_CHAR_ADD_STR,
2360 FILTER_MAP_IDENTITY,
2368 ITERATOR_STEP_BY_ZERO,
2377 STRING_EXTEND_CHARS,
2378 ITER_CLONED_COLLECT,
2382 UNNECESSARY_FILTER_MAP,
2383 UNNECESSARY_FIND_MAP,
2386 UNINIT_ASSUMED_INIT,
2387 MANUAL_SATURATING_ARITHMETIC,
2390 OPTION_AS_REF_DEREF,
2391 UNNECESSARY_LAZY_EVALUATIONS,
2392 MAP_COLLECT_RESULT_UNIT,
2393 FROM_ITER_INSTEAD_OF_COLLECT,
2401 UNNECESSARY_TO_OWNED,
2404 NEEDLESS_OPTION_AS_DEREF,
2405 IS_DIGIT_ASCII_RADIX,
2406 NEEDLESS_OPTION_TAKE,
2411 /// Extracts a method call name, args, and `Span` of the method name.
2412 fn method_call<'tcx>(recv: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx str, &'tcx [hir::Expr<'tcx>], Span)> {
2413 if let ExprKind::MethodCall(path, args, _) = recv.kind {
2414 if !args.iter().any(|e| e.span.from_expansion()) {
2415 let name = path.ident.name.as_str();
2416 return Some((name, args, path.ident.span));
2422 impl<'tcx> LateLintPass<'tcx> for Methods {
2423 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
2424 if expr.span.from_expansion() {
2428 self.check_methods(cx, expr);
2431 hir::ExprKind::Call(func, args) => {
2432 from_iter_instead_of_collect::check(cx, expr, args, func);
2434 hir::ExprKind::MethodCall(method_call, args, _) => {
2435 let method_span = method_call.ident.span;
2436 or_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2437 expect_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2438 clone_on_copy::check(cx, expr, method_call.ident.name, args);
2439 clone_on_ref_ptr::check(cx, expr, method_call.ident.name, args);
2440 inefficient_to_string::check(cx, expr, method_call.ident.name, args);
2441 single_char_add_str::check(cx, expr, args);
2442 into_iter_on_ref::check(cx, expr, method_span, method_call.ident.name, args);
2443 single_char_pattern::check(cx, expr, method_call.ident.name, args);
2444 unnecessary_to_owned::check(cx, expr, method_call.ident.name, args, self.msrv);
2446 hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
2447 let mut info = BinaryExprInfo {
2451 eq: op.node == hir::BinOpKind::Eq,
2453 lint_binary_expr_with_method_call(cx, &mut info);
2459 #[allow(clippy::too_many_lines)]
2460 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
2461 if in_external_macro(cx.sess(), impl_item.span) {
2464 let name = impl_item.ident.name.as_str();
2465 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
2466 let item = cx.tcx.hir().expect_item(parent);
2467 let self_ty = cx.tcx.type_of(item.def_id);
2469 let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
2471 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
2472 if let Some(first_arg) = iter_input_pats(sig.decl, cx.tcx.hir().body(id)).next();
2474 let method_sig = cx.tcx.fn_sig(impl_item.def_id);
2475 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
2477 let first_arg_ty = method_sig.inputs().iter().next();
2479 // check conventions w.r.t. conversion method names and predicates
2480 if let Some(first_arg_ty) = first_arg_ty;
2483 // if this impl block implements a trait, lint in trait definition instead
2484 if !implements_trait && cx.access_levels.is_exported(impl_item.def_id) {
2485 // check missing trait implementations
2486 for method_config in &TRAIT_METHODS {
2487 if name == method_config.method_name &&
2488 sig.decl.inputs.len() == method_config.param_count &&
2489 method_config.output_type.matches(&sig.decl.output) &&
2490 method_config.self_kind.matches(cx, self_ty, *first_arg_ty) &&
2491 fn_header_equals(method_config.fn_header, sig.header) &&
2492 method_config.lifetime_param_cond(impl_item)
2496 SHOULD_IMPLEMENT_TRAIT,
2499 "method `{}` can be confused for the standard trait method `{}::{}`",
2500 method_config.method_name,
2501 method_config.trait_name,
2502 method_config.method_name
2506 "consider implementing the trait `{}` or choosing a less ambiguous method name",
2507 method_config.trait_name
2514 if sig.decl.implicit_self.has_implicit_self()
2515 && !(self.avoid_breaking_exported_api
2516 && cx.access_levels.is_exported(impl_item.def_id))
2518 wrong_self_convention::check(
2531 // if this impl block implements a trait, lint in trait definition instead
2532 if implements_trait {
2536 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
2537 let ret_ty = return_ty(cx, impl_item.hir_id());
2539 // walk the return type and check for Self (this does not check associated types)
2540 if let Some(self_adt) = self_ty.ty_adt_def() {
2541 if contains_adt_constructor(ret_ty, self_adt) {
2544 } else if contains_ty(ret_ty, self_ty) {
2548 // if return type is impl trait, check the associated types
2549 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
2550 // one of the associated types must be Self
2551 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
2552 if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
2553 let assoc_ty = match projection_predicate.term {
2554 ty::Term::Ty(ty) => ty,
2555 ty::Term::Const(_c) => continue,
2557 // walk the associated type and check for Self
2558 if let Some(self_adt) = self_ty.ty_adt_def() {
2559 if contains_adt_constructor(assoc_ty, self_adt) {
2562 } else if contains_ty(assoc_ty, self_ty) {
2569 if name == "new" && ret_ty != self_ty {
2574 "methods called `new` usually return `Self`",
2580 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
2581 if in_external_macro(cx.tcx.sess, item.span) {
2586 if let TraitItemKind::Fn(ref sig, _) = item.kind;
2587 if sig.decl.implicit_self.has_implicit_self();
2588 if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
2591 let first_arg_span = first_arg_ty.span;
2592 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
2593 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2594 wrong_self_convention::check(
2596 item.ident.name.as_str(),
2607 if item.ident.name == sym::new;
2608 if let TraitItemKind::Fn(_, _) = item.kind;
2609 let ret_ty = return_ty(cx, item.hir_id());
2610 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2611 if !contains_ty(ret_ty, self_ty);
2618 "methods called `new` usually return `Self`",
2624 extract_msrv_attr!(LateContext);
2628 #[allow(clippy::too_many_lines)]
2629 fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
2630 if let Some((name, [recv, args @ ..], span)) = method_call(expr) {
2631 match (name, args) {
2632 ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
2633 zst_offset::check(cx, expr, recv);
2635 ("and_then", [arg]) => {
2636 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, recv, arg);
2637 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, recv, arg);
2638 if !biom_option_linted && !biom_result_linted {
2639 unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
2642 ("as_deref" | "as_deref_mut", []) => {
2643 needless_option_as_deref::check(cx, expr, recv, name);
2645 ("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
2646 ("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
2647 ("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
2648 ("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span, self.msrv),
2649 ("collect", []) => match method_call(recv) {
2650 Some((name @ ("cloned" | "copied"), [recv2], _)) => {
2651 iter_cloned_collect::check(cx, name, expr, recv2);
2653 Some(("map", [m_recv, m_arg], _)) => {
2654 map_collect_result_unit::check(cx, expr, m_recv, m_arg, recv);
2656 Some(("take", [take_self_arg, take_arg], _)) => {
2657 if meets_msrv(self.msrv, msrvs::STR_REPEAT) {
2658 manual_str_repeat::check(cx, expr, recv, take_self_arg, take_arg);
2663 ("count", []) => match method_call(recv) {
2664 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, true, false),
2665 Some((name2 @ ("into_iter" | "iter" | "iter_mut"), [recv2], _)) => {
2666 iter_count::check(cx, expr, recv2, name2);
2668 Some(("map", [_, arg], _)) => suspicious_map::check(cx, expr, recv, arg),
2671 ("drain", [arg]) => {
2672 iter_with_drain::check(cx, expr, recv, span, arg);
2674 ("expect", [_]) => match method_call(recv) {
2675 Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
2676 Some(("err", [recv], err_span)) => err_expect::check(cx, expr, recv, self.msrv, span, err_span),
2677 _ => expect_used::check(cx, expr, recv, self.allow_expect_in_tests),
2679 ("extend", [arg]) => {
2680 string_extend_chars::check(cx, expr, recv, arg);
2681 extend_with_drain::check(cx, expr, recv, arg);
2683 ("filter_map", [arg]) => {
2684 unnecessary_filter_map::check(cx, expr, arg, name);
2685 filter_map_identity::check(cx, expr, arg, span);
2687 ("find_map", [arg]) => {
2688 unnecessary_filter_map::check(cx, expr, arg, name);
2690 ("flat_map", [arg]) => {
2691 flat_map_identity::check(cx, expr, arg, span);
2692 flat_map_option::check(cx, expr, arg, span);
2694 ("flatten", []) => match method_call(recv) {
2695 Some(("map", [recv, map_arg], map_span)) => map_flatten::check(cx, expr, recv, map_arg, map_span),
2696 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, true),
2699 ("fold", [init, acc]) => unnecessary_fold::check(cx, expr, init, acc, span),
2700 ("for_each", [_]) => {
2701 if let Some(("inspect", [_, _], span2)) = method_call(recv) {
2702 inspect_for_each::check(cx, expr, span2);
2705 ("get", [arg]) => get_last_with_len::check(cx, expr, recv, arg),
2706 ("get_or_insert_with", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "get_or_insert"),
2707 ("is_file", []) => filetype_is_file::check(cx, expr, recv),
2708 ("is_digit", [radix]) => is_digit_ascii_radix::check(cx, expr, recv, radix, self.msrv),
2709 ("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
2710 ("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
2711 ("join", [join_arg]) => {
2712 if let Some(("collect", _, span)) = method_call(recv) {
2713 unnecessary_join::check(cx, expr, recv, join_arg, span);
2716 ("last", []) | ("skip", [_]) => {
2717 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2718 if let ("cloned", []) = (name2, args2) {
2719 iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
2723 (name @ ("map" | "map_err"), [m_arg]) => {
2724 if let Some((name, [recv2, args @ ..], span2)) = method_call(recv) {
2725 match (name, args) {
2726 ("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, self.msrv),
2727 ("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, self.msrv),
2728 ("filter", [f_arg]) => {
2729 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
2731 ("find", [f_arg]) => {
2732 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, true);
2737 map_identity::check(cx, expr, recv, m_arg, name, span);
2739 ("map_or", [def, map]) => option_map_or_none::check(cx, expr, recv, def, map),
2741 if let Some((name2, [recv2, args2 @ ..], _)) = method_call(recv) {
2742 match (name2, args2) {
2743 ("cloned", []) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
2744 ("filter", [arg]) => filter_next::check(cx, expr, recv2, arg),
2745 ("filter_map", [arg]) => filter_map_next::check(cx, expr, recv2, arg, self.msrv),
2746 ("iter", []) => iter_next_slice::check(cx, expr, recv2),
2747 ("skip", [arg]) => iter_skip_next::check(cx, expr, recv2, arg),
2748 ("skip_while", [_]) => skip_while_next::check(cx, expr),
2753 ("nth", [n_arg]) => match method_call(recv) {
2754 Some(("bytes", [recv2], _)) => bytes_nth::check(cx, expr, recv2, n_arg),
2755 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
2756 Some(("iter", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, false),
2757 Some(("iter_mut", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, true),
2758 _ => iter_nth_zero::check(cx, expr, recv, n_arg),
2760 ("ok_or_else", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "ok_or"),
2761 ("or_else", [arg]) => {
2762 if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, recv, arg) {
2763 unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
2766 ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
2767 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2768 suspicious_splitn::check(cx, name, expr, recv, count);
2769 str_splitn::check(cx, name, expr, recv, pat_arg, count, self.msrv);
2772 ("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
2773 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2774 suspicious_splitn::check(cx, name, expr, recv, count);
2777 ("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
2778 ("take", [_arg]) => {
2779 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2780 if let ("cloned", []) = (name2, args2) {
2781 iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
2785 ("take", []) => needless_option_take::check(cx, expr, recv),
2786 ("then", [arg]) => {
2787 if !meets_msrv(self.msrv, msrvs::BOOL_THEN_SOME) {
2790 unnecessary_lazy_eval::check(cx, expr, recv, arg, "then_some");
2792 ("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
2793 implicit_clone::check(cx, name, expr, recv);
2796 match method_call(recv) {
2797 Some(("get", [recv, get_arg], _)) => {
2798 get_unwrap::check(cx, expr, recv, get_arg, false);
2800 Some(("get_mut", [recv, get_arg], _)) => {
2801 get_unwrap::check(cx, expr, recv, get_arg, true);
2803 Some(("or", [recv, or_arg], or_span)) => {
2804 or_then_unwrap::check(cx, expr, recv, or_arg, or_span);
2808 unwrap_used::check(cx, expr, recv, self.allow_unwrap_in_tests);
2810 ("unwrap_or", [u_arg]) => match method_call(recv) {
2811 Some((arith @ ("checked_add" | "checked_sub" | "checked_mul"), [lhs, rhs], _)) => {
2812 manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, &arith["checked_".len()..]);
2814 Some(("map", [m_recv, m_arg], span)) => {
2815 option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span);
2817 Some(("then_some", [t_recv, t_arg], _)) => {
2818 obfuscated_if_else::check(cx, expr, t_recv, t_arg, u_arg);
2822 ("unwrap_or_else", [u_arg]) => match method_call(recv) {
2823 Some(("map", [recv, map_arg], _))
2824 if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, self.msrv) => {},
2826 unwrap_or_else_default::check(cx, expr, recv, u_arg);
2827 unnecessary_lazy_eval::check(cx, expr, recv, u_arg, "unwrap_or");
2830 ("replace" | "replacen", [arg1, arg2] | [arg1, arg2, _]) => {
2831 no_effect_replace::check(cx, expr, arg1, arg2);
2839 fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, is_some: bool) {
2840 if let Some((name @ ("find" | "position" | "rposition"), [f_recv, arg], span)) = method_call(recv) {
2841 search_is_some::check(cx, expr, name, is_some, f_recv, arg, recv, span);
2845 /// Used for `lint_binary_expr_with_method_call`.
2846 #[derive(Copy, Clone)]
2847 struct BinaryExprInfo<'a> {
2848 expr: &'a hir::Expr<'a>,
2849 chain: &'a hir::Expr<'a>,
2850 other: &'a hir::Expr<'a>,
2854 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2855 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
2856 macro_rules! lint_with_both_lhs_and_rhs {
2857 ($func:expr, $cx:expr, $info:ident) => {
2858 if !$func($cx, $info) {
2859 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2860 if $func($cx, $info) {
2867 lint_with_both_lhs_and_rhs!(chars_next_cmp::check, cx, info);
2868 lint_with_both_lhs_and_rhs!(chars_last_cmp::check, cx, info);
2869 lint_with_both_lhs_and_rhs!(chars_next_cmp_with_unwrap::check, cx, info);
2870 lint_with_both_lhs_and_rhs!(chars_last_cmp_with_unwrap::check, cx, info);
2873 const FN_HEADER: hir::FnHeader = hir::FnHeader {
2874 unsafety: hir::Unsafety::Normal,
2875 constness: hir::Constness::NotConst,
2876 asyncness: hir::IsAsync::NotAsync,
2877 abi: rustc_target::spec::abi::Abi::Rust,
2880 struct ShouldImplTraitCase {
2881 trait_name: &'static str,
2882 method_name: &'static str,
2884 fn_header: hir::FnHeader,
2885 // implicit self kind expected (none, self, &self, ...)
2886 self_kind: SelfKind,
2887 // checks against the output type
2888 output_type: OutType,
2889 // certain methods with explicit lifetimes can't implement the equivalent trait method
2890 lint_explicit_lifetime: bool,
2892 impl ShouldImplTraitCase {
2894 trait_name: &'static str,
2895 method_name: &'static str,
2897 fn_header: hir::FnHeader,
2898 self_kind: SelfKind,
2899 output_type: OutType,
2900 lint_explicit_lifetime: bool,
2901 ) -> ShouldImplTraitCase {
2902 ShouldImplTraitCase {
2909 lint_explicit_lifetime,
2913 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
2914 self.lint_explicit_lifetime
2915 || !impl_item.generics.params.iter().any(|p| {
2918 hir::GenericParamKind::Lifetime {
2919 kind: hir::LifetimeParamKind::Explicit
2927 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
2928 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2929 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2930 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2931 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2932 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2933 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2934 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2935 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2936 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2937 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2938 // FIXME: default doesn't work
2939 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
2940 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2941 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2942 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2943 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
2944 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
2945 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2946 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2947 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
2948 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2949 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2950 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2951 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2952 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2953 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
2954 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2955 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2956 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2957 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2958 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2961 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
2970 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2971 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2972 if ty == parent_ty {
2974 } else if ty.is_box() {
2975 ty.boxed_ty() == parent_ty
2976 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
2977 if let ty::Adt(_, substs) = ty.kind() {
2978 substs.types().next().map_or(false, |t| t == parent_ty)
2987 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2988 if let ty::Ref(_, t, m) = *ty.kind() {
2989 return m == mutability && t == parent_ty;
2992 let trait_path = match mutability {
2993 hir::Mutability::Not => &paths::ASREF_TRAIT,
2994 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
2997 let trait_def_id = match get_trait_def_id(cx, trait_path) {
2999 None => return false,
3001 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3004 fn matches_none<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3005 !matches_value(cx, parent_ty, ty)
3006 && !matches_ref(cx, hir::Mutability::Not, parent_ty, ty)
3007 && !matches_ref(cx, hir::Mutability::Mut, parent_ty, ty)
3011 Self::Value => matches_value(cx, parent_ty, ty),
3012 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3013 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3014 Self::No => matches_none(cx, parent_ty, ty),
3019 fn description(self) -> &'static str {
3021 Self::Value => "`self` by value",
3022 Self::Ref => "`self` by reference",
3023 Self::RefMut => "`self` by mutable reference",
3024 Self::No => "no `self`",
3029 #[derive(Clone, Copy)]
3038 fn matches(self, ty: &hir::FnRetTy<'_>) -> bool {
3039 let is_unit = |ty: &hir::Ty<'_>| matches!(ty.kind, hir::TyKind::Tup(&[]));
3041 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3042 (Self::Unit, &hir::FnRetTy::Return(ty)) if is_unit(ty) => true,
3043 (Self::Bool, &hir::FnRetTy::Return(ty)) if is_bool(ty) => true,
3044 (Self::Any, &hir::FnRetTy::Return(ty)) if !is_unit(ty) => true,
3045 (Self::Ref, &hir::FnRetTy::Return(ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3051 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3052 if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
3053 matches!(path.res, Res::PrimTy(PrimTy::Bool))
3059 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
3060 expected.constness == actual.constness
3061 && expected.unsafety == actual.unsafety
3062 && expected.asyncness == actual.asyncness