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;
14 mod extend_with_drain;
17 mod filter_map_identity;
20 mod flat_map_identity;
22 mod from_iter_instead_of_collect;
25 mod inefficient_to_string;
28 mod iter_cloned_collect;
33 mod iter_overeager_cloned;
35 mod iterator_step_by_zero;
36 mod manual_saturating_arithmetic;
37 mod manual_str_repeat;
38 mod map_collect_result_unit;
43 mod option_as_ref_deref;
44 mod option_map_or_none;
45 mod option_map_unwrap_or;
48 mod single_char_add_str;
49 mod single_char_insert_string;
50 mod single_char_pattern;
51 mod single_char_push_string;
54 mod string_extend_chars;
56 mod suspicious_splitn;
57 mod uninit_assumed_init;
58 mod unnecessary_filter_map;
60 mod unnecessary_iter_cloned;
61 mod unnecessary_lazy_eval;
62 mod unnecessary_to_owned;
63 mod unwrap_or_else_default;
67 mod wrong_self_convention;
70 use bind_instead_of_map::BindInsteadOfMap;
71 use clippy_utils::consts::{constant, Constant};
72 use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
73 use clippy_utils::ty::{contains_adt_constructor, contains_ty, implements_trait, is_copy, is_type_diagnostic_item};
74 use clippy_utils::{contains_return, get_trait_def_id, iter_input_pats, meets_msrv, msrvs, paths, return_ty};
75 use if_chain::if_chain;
77 use rustc_hir::def::Res;
78 use rustc_hir::{Expr, ExprKind, PrimTy, QPath, TraitItem, TraitItemKind};
79 use rustc_lint::{LateContext, LateLintPass, LintContext};
80 use rustc_middle::lint::in_external_macro;
81 use rustc_middle::ty::{self, TraitRef, Ty, TyS};
82 use rustc_semver::RustcVersion;
83 use rustc_session::{declare_tool_lint, impl_lint_pass};
84 use rustc_span::{sym, Span};
85 use rustc_typeck::hir_ty_to_ty;
87 declare_clippy_lint! {
89 /// Checks for usages of `cloned()` on an `Iterator` or `Option` where
90 /// `copied()` could be used instead.
92 /// ### Why is this bad?
93 /// `copied()` is better because it guarantees that the type being cloned
94 /// implements `Copy`.
98 /// [1, 2, 3].iter().cloned();
102 /// [1, 2, 3].iter().copied();
104 #[clippy::version = "1.53.0"]
105 pub CLONED_INSTEAD_OF_COPIED,
107 "used `cloned` where `copied` could be used instead"
110 declare_clippy_lint! {
112 /// Checks for usage of `_.cloned().<func>()` where call to `.cloned()` can be postponed.
114 /// ### Why is this bad?
115 /// It's often inefficient to clone all elements of an iterator, when eventually, only some
116 /// of them will be consumed.
120 /// # let vec = vec!["string".to_string()];
123 /// vec.iter().cloned().take(10);
126 /// vec.iter().take(10).cloned();
129 /// vec.iter().cloned().last();
132 /// vec.iter().last().cloned();
135 /// ### Known Problems
136 /// This `lint` removes the side of effect of cloning items in the iterator.
137 /// A code that relies on that side-effect could fail.
139 #[clippy::version = "1.59.0"]
140 pub ITER_OVEREAGER_CLONED,
142 "using `cloned()` early with `Iterator::iter()` can lead to some performance inefficiencies"
145 declare_clippy_lint! {
147 /// Checks for usages of `Iterator::flat_map()` where `filter_map()` could be
150 /// ### Why is this bad?
151 /// When applicable, `filter_map()` is more clear since it shows that
152 /// `Option` is used to produce 0 or 1 items.
156 /// let nums: Vec<i32> = ["1", "2", "whee!"].iter().flat_map(|x| x.parse().ok()).collect();
160 /// let nums: Vec<i32> = ["1", "2", "whee!"].iter().filter_map(|x| x.parse().ok()).collect();
162 #[clippy::version = "1.53.0"]
165 "used `flat_map` where `filter_map` could be used instead"
168 declare_clippy_lint! {
170 /// Checks for `.unwrap()` calls on `Option`s and on `Result`s.
172 /// ### Why is this bad?
173 /// It is better to handle the `None` or `Err` case,
174 /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
175 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
176 /// `Allow` by default.
178 /// `result.unwrap()` will let the thread panic on `Err` values.
179 /// Normally, you want to implement more sophisticated error handling,
180 /// and propagate errors upwards with `?` operator.
182 /// Even if you want to panic on errors, not all `Error`s implement good
183 /// messages on display. Therefore, it may be beneficial to look at the places
184 /// where they may get displayed. Activate this lint to do just that.
188 /// # let opt = Some(1);
194 /// opt.expect("more helpful message");
200 /// # let res: Result<usize, ()> = Ok(1);
206 /// res.expect("more helpful message");
208 #[clippy::version = "1.45.0"]
211 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
214 declare_clippy_lint! {
216 /// Checks for `.expect()` calls on `Option`s and `Result`s.
218 /// ### Why is this bad?
219 /// Usually it is better to handle the `None` or `Err` case.
220 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
221 /// this lint is `Allow` by default.
223 /// `result.expect()` will let the thread panic on `Err`
224 /// values. Normally, you want to implement more sophisticated error handling,
225 /// and propagate errors upwards with `?` operator.
229 /// # let opt = Some(1);
232 /// opt.expect("one");
235 /// let opt = Some(1);
242 /// # let res: Result<usize, ()> = Ok(1);
245 /// res.expect("one");
249 /// # Ok::<(), ()>(())
251 #[clippy::version = "1.45.0"]
254 "using `.expect()` on `Result` or `Option`, which might be better handled"
257 declare_clippy_lint! {
259 /// Checks for methods that should live in a trait
260 /// implementation of a `std` trait (see [llogiq's blog
261 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
262 /// information) instead of an inherent implementation.
264 /// ### Why is this bad?
265 /// Implementing the traits improve ergonomics for users of
266 /// the code, often with very little cost. Also people seeing a `mul(...)`
268 /// may expect `*` to work equally, so you should have good reason to disappoint
275 /// fn add(&self, other: &X) -> X {
281 #[clippy::version = "pre 1.29.0"]
282 pub SHOULD_IMPLEMENT_TRAIT,
284 "defining a method that should be implementing a std trait"
287 declare_clippy_lint! {
289 /// Checks for methods with certain name prefixes and which
290 /// doesn't match how self is taken. The actual rules are:
292 /// |Prefix |Postfix |`self` taken | `self` type |
293 /// |-------|------------|-----------------------|--------------|
294 /// |`as_` | none |`&self` or `&mut self` | any |
295 /// |`from_`| none | none | any |
296 /// |`into_`| none |`self` | any |
297 /// |`is_` | none |`&self` or none | any |
298 /// |`to_` | `_mut` |`&mut self` | any |
299 /// |`to_` | not `_mut` |`self` | `Copy` |
300 /// |`to_` | not `_mut` |`&self` | not `Copy` |
302 /// Note: Clippy doesn't trigger methods with `to_` prefix in:
303 /// - Traits definition.
304 /// Clippy can not tell if a type that implements a trait is `Copy` or not.
305 /// - Traits implementation, when `&self` is taken.
306 /// The method signature is controlled by the trait and often `&self` is required for all types that implement the trait
307 /// (see e.g. the `std::string::ToString` trait).
309 /// Clippy allows `Pin<&Self>` and `Pin<&mut Self>` if `&self` and `&mut self` is required.
311 /// Please find more info here:
312 /// https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv
314 /// ### Why is this bad?
315 /// Consistency breeds readability. If you follow the
316 /// conventions, your users won't be surprised that they, e.g., need to supply a
317 /// mutable reference to a `as_..` function.
323 /// fn as_str(self) -> &'static str {
329 #[clippy::version = "pre 1.29.0"]
330 pub WRONG_SELF_CONVENTION,
332 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
335 declare_clippy_lint! {
337 /// Checks for usage of `ok().expect(..)`.
339 /// ### Why is this bad?
340 /// Because you usually call `expect()` on the `Result`
341 /// directly to get a better error message.
343 /// ### Known problems
344 /// The error type needs to implement `Debug`
348 /// # let x = Ok::<_, ()>(());
351 /// x.ok().expect("why did I do this again?");
354 /// x.expect("why did I do this again?");
356 #[clippy::version = "pre 1.29.0"]
359 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
362 declare_clippy_lint! {
364 /// Checks for usages of `_.unwrap_or_else(Default::default)` on `Option` and
367 /// ### Why is this bad?
368 /// Readability, these can be written as `_.unwrap_or_default`, which is
369 /// simpler and more concise.
373 /// # let x = Some(1);
376 /// x.unwrap_or_else(Default::default);
377 /// x.unwrap_or_else(u32::default);
380 /// x.unwrap_or_default();
382 #[clippy::version = "1.56.0"]
383 pub UNWRAP_OR_ELSE_DEFAULT,
385 "using `.unwrap_or_else(Default::default)`, which is more succinctly expressed as `.unwrap_or_default()`"
388 declare_clippy_lint! {
390 /// Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
391 /// `result.map(_).unwrap_or_else(_)`.
393 /// ### Why is this bad?
394 /// Readability, these can be written more concisely (resp.) as
395 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
397 /// ### Known problems
398 /// The order of the arguments is not in execution order
402 /// # let x = Some(1);
405 /// x.map(|a| a + 1).unwrap_or(0);
408 /// x.map_or(0, |a| a + 1);
414 /// # let x: Result<usize, ()> = Ok(1);
415 /// # fn some_function(foo: ()) -> usize { 1 }
418 /// x.map(|a| a + 1).unwrap_or_else(some_function);
421 /// x.map_or_else(some_function, |a| a + 1);
423 #[clippy::version = "1.45.0"]
426 "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)`"
429 declare_clippy_lint! {
431 /// Checks for usage of `_.map_or(None, _)`.
433 /// ### Why is this bad?
434 /// Readability, this can be written more concisely as
437 /// ### Known problems
438 /// The order of the arguments is not in execution order.
442 /// # let opt = Some(1);
445 /// opt.map_or(None, |a| Some(a + 1));
448 /// opt.and_then(|a| Some(a + 1));
450 #[clippy::version = "pre 1.29.0"]
451 pub OPTION_MAP_OR_NONE,
453 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
456 declare_clippy_lint! {
458 /// Checks for usage of `_.map_or(None, Some)`.
460 /// ### Why is this bad?
461 /// Readability, this can be written more concisely as
467 /// # let r: Result<u32, &str> = Ok(1);
468 /// assert_eq!(Some(1), r.map_or(None, Some));
473 /// # let r: Result<u32, &str> = Ok(1);
474 /// assert_eq!(Some(1), r.ok());
476 #[clippy::version = "1.44.0"]
477 pub RESULT_MAP_OR_INTO_OPTION,
479 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
482 declare_clippy_lint! {
484 /// Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
485 /// `_.or_else(|x| Err(y))`.
487 /// ### Why is this bad?
488 /// Readability, this can be written more concisely as
489 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
493 /// # fn opt() -> Option<&'static str> { Some("42") }
494 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
495 /// let _ = opt().and_then(|s| Some(s.len()));
496 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
497 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
500 /// The correct use would be:
503 /// # fn opt() -> Option<&'static str> { Some("42") }
504 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
505 /// let _ = opt().map(|s| s.len());
506 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
507 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
509 #[clippy::version = "1.45.0"]
510 pub BIND_INSTEAD_OF_MAP,
512 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
515 declare_clippy_lint! {
517 /// Checks for usage of `_.filter(_).next()`.
519 /// ### Why is this bad?
520 /// Readability, this can be written more concisely as
525 /// # let vec = vec![1];
526 /// vec.iter().filter(|x| **x == 0).next();
528 /// Could be written as
530 /// # let vec = vec![1];
531 /// vec.iter().find(|x| **x == 0);
533 #[clippy::version = "pre 1.29.0"]
536 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
539 declare_clippy_lint! {
541 /// Checks for usage of `_.skip_while(condition).next()`.
543 /// ### Why is this bad?
544 /// Readability, this can be written more concisely as
545 /// `_.find(!condition)`.
549 /// # let vec = vec![1];
550 /// vec.iter().skip_while(|x| **x == 0).next();
552 /// Could be written as
554 /// # let vec = vec![1];
555 /// vec.iter().find(|x| **x != 0);
557 #[clippy::version = "1.42.0"]
560 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
563 declare_clippy_lint! {
565 /// Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
567 /// ### Why is this bad?
568 /// Readability, this can be written more concisely as
573 /// let vec = vec![vec![1]];
576 /// vec.iter().map(|x| x.iter()).flatten();
579 /// vec.iter().flat_map(|x| x.iter());
581 #[clippy::version = "1.31.0"]
584 "using combinations of `flatten` and `map` which can usually be written as a single method call"
587 declare_clippy_lint! {
589 /// Checks for usage of `_.filter(_).map(_)` that can be written more simply
590 /// as `filter_map(_)`.
592 /// ### Why is this bad?
593 /// Redundant code in the `filter` and `map` operations is poor style and
600 /// .filter(|n| n.checked_add(1).is_some())
601 /// .map(|n| n.checked_add(1).unwrap());
606 /// (0_i32..10).filter_map(|n| n.checked_add(1));
608 #[clippy::version = "1.51.0"]
609 pub MANUAL_FILTER_MAP,
611 "using `_.filter(_).map(_)` in a way that can be written more simply as `filter_map(_)`"
614 declare_clippy_lint! {
616 /// Checks for usage of `_.find(_).map(_)` that can be written more simply
617 /// as `find_map(_)`.
619 /// ### Why is this bad?
620 /// Redundant code in the `find` and `map` operations is poor style and
627 /// .find(|n| n.checked_add(1).is_some())
628 /// .map(|n| n.checked_add(1).unwrap());
633 /// (0_i32..10).find_map(|n| n.checked_add(1));
635 #[clippy::version = "1.51.0"]
638 "using `_.find(_).map(_)` in a way that can be written more simply as `find_map(_)`"
641 declare_clippy_lint! {
643 /// Checks for usage of `_.filter_map(_).next()`.
645 /// ### Why is this bad?
646 /// Readability, this can be written more concisely as
651 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
653 /// Can be written as
656 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
658 #[clippy::version = "1.36.0"]
661 "using combination of `filter_map` and `next` which can usually be written as a single method call"
664 declare_clippy_lint! {
666 /// Checks for usage of `flat_map(|x| x)`.
668 /// ### Why is this bad?
669 /// Readability, this can be written more concisely by using `flatten`.
673 /// # let iter = vec![vec![0]].into_iter();
674 /// iter.flat_map(|x| x);
676 /// Can be written as
678 /// # let iter = vec![vec![0]].into_iter();
681 #[clippy::version = "1.39.0"]
682 pub FLAT_MAP_IDENTITY,
684 "call to `flat_map` where `flatten` is sufficient"
687 declare_clippy_lint! {
689 /// Checks for an iterator or string search (such as `find()`,
690 /// `position()`, or `rposition()`) followed by a call to `is_some()` or `is_none()`.
692 /// ### Why is this bad?
693 /// Readability, this can be written more concisely as:
694 /// * `_.any(_)`, or `_.contains(_)` for `is_some()`,
695 /// * `!_.any(_)`, or `!_.contains(_)` for `is_none()`.
699 /// let vec = vec![1];
700 /// vec.iter().find(|x| **x == 0).is_some();
702 /// let _ = "hello world".find("world").is_none();
704 /// Could be written as
706 /// let vec = vec![1];
707 /// vec.iter().any(|x| *x == 0);
709 /// let _ = !"hello world".contains("world");
711 #[clippy::version = "pre 1.29.0"]
714 "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()`)"
717 declare_clippy_lint! {
719 /// Checks for usage of `.chars().next()` on a `str` to check
720 /// if it starts with a given char.
722 /// ### Why is this bad?
723 /// Readability, this can be written more concisely as
724 /// `_.starts_with(_)`.
728 /// let name = "foo";
729 /// if name.chars().next() == Some('_') {};
731 /// Could be written as
733 /// let name = "foo";
734 /// if name.starts_with('_') {};
736 #[clippy::version = "pre 1.29.0"]
739 "using `.chars().next()` to check if a string starts with a char"
742 declare_clippy_lint! {
744 /// Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
745 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
746 /// `unwrap_or_default` instead.
748 /// ### Why is this bad?
749 /// The function will always be called and potentially
750 /// allocate an object acting as the default.
752 /// ### Known problems
753 /// If the function has side-effects, not calling it will
754 /// change the semantic of the program, but you shouldn't rely on that anyway.
758 /// # let foo = Some(String::new());
759 /// foo.unwrap_or(String::new());
761 /// this can instead be written:
763 /// # let foo = Some(String::new());
764 /// foo.unwrap_or_else(String::new);
768 /// # let foo = Some(String::new());
769 /// foo.unwrap_or_default();
771 #[clippy::version = "pre 1.29.0"]
774 "using any `*or` method with a function call, which suggests `*or_else`"
777 declare_clippy_lint! {
779 /// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
780 /// etc., and suggests to use `unwrap_or_else` instead
782 /// ### Why is this bad?
783 /// The function will always be called.
785 /// ### Known problems
786 /// If the function has side-effects, not calling it will
787 /// change the semantics of the program, but you shouldn't rely on that anyway.
791 /// # let foo = Some(String::new());
792 /// # let err_code = "418";
793 /// # let err_msg = "I'm a teapot";
794 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
798 /// # let foo = Some(String::new());
799 /// # let err_code = "418";
800 /// # let err_msg = "I'm a teapot";
801 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
803 /// this can instead be written:
805 /// # let foo = Some(String::new());
806 /// # let err_code = "418";
807 /// # let err_msg = "I'm a teapot";
808 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
810 #[clippy::version = "pre 1.29.0"]
813 "using any `expect` method with a function call"
816 declare_clippy_lint! {
818 /// Checks for usage of `.clone()` on a `Copy` type.
820 /// ### Why is this bad?
821 /// The only reason `Copy` types implement `Clone` is for
822 /// generics, not for using the `clone` method on a concrete type.
828 #[clippy::version = "pre 1.29.0"]
831 "using `clone` on a `Copy` type"
834 declare_clippy_lint! {
836 /// Checks for usage of `.clone()` on a ref-counted pointer,
837 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
838 /// function syntax instead (e.g., `Rc::clone(foo)`).
840 /// ### Why is this bad?
841 /// Calling '.clone()' on an Rc, Arc, or Weak
842 /// can obscure the fact that only the pointer is being cloned, not the underlying
847 /// # use std::rc::Rc;
848 /// let x = Rc::new(1);
856 #[clippy::version = "pre 1.29.0"]
857 pub CLONE_ON_REF_PTR,
859 "using 'clone' on a ref-counted pointer"
862 declare_clippy_lint! {
864 /// Checks for usage of `.clone()` on an `&&T`.
866 /// ### Why is this bad?
867 /// Cloning an `&&T` copies the inner `&T`, instead of
868 /// cloning the underlying `T`.
875 /// let z = y.clone();
876 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
879 #[clippy::version = "pre 1.29.0"]
880 pub CLONE_DOUBLE_REF,
882 "using `clone` on `&&T`"
885 declare_clippy_lint! {
887 /// Checks for usage of `.to_string()` on an `&&T` where
888 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
890 /// ### Why is this bad?
891 /// This bypasses the specialized implementation of
892 /// `ToString` and instead goes through the more expensive string formatting
897 /// // Generic implementation for `T: Display` is used (slow)
898 /// ["foo", "bar"].iter().map(|s| s.to_string());
900 /// // OK, the specialized impl is used
901 /// ["foo", "bar"].iter().map(|&s| s.to_string());
903 #[clippy::version = "1.40.0"]
904 pub INEFFICIENT_TO_STRING,
906 "using `to_string` on `&&T` where `T: ToString`"
909 declare_clippy_lint! {
911 /// Checks for `new` not returning a type that contains `Self`.
913 /// ### Why is this bad?
914 /// As a convention, `new` methods are used to make a new
915 /// instance of a type.
918 /// In an impl block:
921 /// # struct NotAFoo;
923 /// fn new() -> NotAFoo {
933 /// // Bad. The type name must contain `Self`
934 /// fn new() -> Bar {
942 /// # struct FooError;
944 /// // Good. Return type contains `Self`
945 /// fn new() -> Result<Foo, FooError> {
951 /// Or in a trait definition:
953 /// pub trait Trait {
954 /// // Bad. The type name must contain `Self`
960 /// pub trait Trait {
961 /// // Good. Return type contains `Self`
962 /// fn new() -> Self;
965 #[clippy::version = "pre 1.29.0"]
968 "not returning type containing `Self` in a `new` method"
971 declare_clippy_lint! {
973 /// Checks for string methods that receive a single-character
974 /// `str` as an argument, e.g., `_.split("x")`.
976 /// ### Why is this bad?
977 /// Performing these methods using a `char` is faster than
980 /// ### Known problems
981 /// Does not catch multi-byte unicode characters.
990 #[clippy::version = "pre 1.29.0"]
991 pub SINGLE_CHAR_PATTERN,
993 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
996 declare_clippy_lint! {
998 /// Checks for calling `.step_by(0)` on iterators which panics.
1000 /// ### Why is this bad?
1001 /// This very much looks like an oversight. Use `panic!()` instead if you
1002 /// actually intend to panic.
1005 /// ```rust,should_panic
1006 /// for x in (0..100).step_by(0) {
1010 #[clippy::version = "pre 1.29.0"]
1011 pub ITERATOR_STEP_BY_ZERO,
1013 "using `Iterator::step_by(0)`, which will panic at runtime"
1016 declare_clippy_lint! {
1017 /// ### What it does
1018 /// Checks for indirect collection of populated `Option`
1020 /// ### Why is this bad?
1021 /// `Option` is like a collection of 0-1 things, so `flatten`
1022 /// automatically does this without suspicious-looking `unwrap` calls.
1026 /// let _ = std::iter::empty::<Option<i32>>().filter(Option::is_some).map(Option::unwrap);
1030 /// let _ = std::iter::empty::<Option<i32>>().flatten();
1032 #[clippy::version = "1.53.0"]
1033 pub OPTION_FILTER_MAP,
1035 "filtering `Option` for `Some` then force-unwrapping, which can be one type-safe operation"
1038 declare_clippy_lint! {
1039 /// ### What it does
1040 /// Checks for the use of `iter.nth(0)`.
1042 /// ### Why is this bad?
1043 /// `iter.next()` is equivalent to
1044 /// `iter.nth(0)`, as they both consume the next element,
1045 /// but is more readable.
1049 /// # use std::collections::HashSet;
1051 /// # let mut s = HashSet::new();
1053 /// let x = s.iter().nth(0);
1056 /// # let mut s = HashSet::new();
1058 /// let x = s.iter().next();
1060 #[clippy::version = "1.42.0"]
1063 "replace `iter.nth(0)` with `iter.next()`"
1066 declare_clippy_lint! {
1067 /// ### What it does
1068 /// Checks for use of `.iter().nth()` (and the related
1069 /// `.iter_mut().nth()`) on standard library types with *O*(1) element access.
1071 /// ### Why is this bad?
1072 /// `.get()` and `.get_mut()` are more efficient and more
1077 /// let some_vec = vec![0, 1, 2, 3];
1078 /// let bad_vec = some_vec.iter().nth(3);
1079 /// let bad_slice = &some_vec[..].iter().nth(3);
1081 /// The correct use would be:
1083 /// let some_vec = vec![0, 1, 2, 3];
1084 /// let bad_vec = some_vec.get(3);
1085 /// let bad_slice = &some_vec[..].get(3);
1087 #[clippy::version = "pre 1.29.0"]
1090 "using `.iter().nth()` on a standard library type with O(1) element access"
1093 declare_clippy_lint! {
1094 /// ### What it does
1095 /// Checks for use of `.skip(x).next()` on iterators.
1097 /// ### Why is this bad?
1098 /// `.nth(x)` is cleaner
1102 /// let some_vec = vec![0, 1, 2, 3];
1103 /// let bad_vec = some_vec.iter().skip(3).next();
1104 /// let bad_slice = &some_vec[..].iter().skip(3).next();
1106 /// The correct use would be:
1108 /// let some_vec = vec![0, 1, 2, 3];
1109 /// let bad_vec = some_vec.iter().nth(3);
1110 /// let bad_slice = &some_vec[..].iter().nth(3);
1112 #[clippy::version = "pre 1.29.0"]
1115 "using `.skip(x).next()` on an iterator"
1118 declare_clippy_lint! {
1119 /// ### What it does
1120 /// Checks for use of `.get().unwrap()` (or
1121 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
1123 /// ### Why is this bad?
1124 /// Using the Index trait (`[]`) is more clear and more
1127 /// ### Known problems
1128 /// Not a replacement for error handling: Using either
1129 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
1130 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
1131 /// temporary placeholder for dealing with the `Option` type, then this does
1132 /// not mitigate the need for error handling. If there is a chance that `.get()`
1133 /// will be `None` in your program, then it is advisable that the `None` case
1134 /// is handled in a future refactor instead of using `.unwrap()` or the Index
1139 /// let mut some_vec = vec![0, 1, 2, 3];
1140 /// let last = some_vec.get(3).unwrap();
1141 /// *some_vec.get_mut(0).unwrap() = 1;
1143 /// The correct use would be:
1145 /// let mut some_vec = vec![0, 1, 2, 3];
1146 /// let last = some_vec[3];
1147 /// some_vec[0] = 1;
1149 #[clippy::version = "pre 1.29.0"]
1152 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
1155 declare_clippy_lint! {
1156 /// ### What it does
1157 /// Checks for occurrences where one vector gets extended instead of append
1159 /// ### Why is this bad?
1160 /// Using `append` instead of `extend` is more concise and faster
1164 /// let mut a = vec![1, 2, 3];
1165 /// let mut b = vec![4, 5, 6];
1168 /// a.extend(b.drain(..));
1171 /// a.append(&mut b);
1173 #[clippy::version = "1.55.0"]
1174 pub EXTEND_WITH_DRAIN,
1176 "using vec.append(&mut vec) to move the full range of a vecor to another"
1179 declare_clippy_lint! {
1180 /// ### What it does
1181 /// Checks for the use of `.extend(s.chars())` where s is a
1182 /// `&str` or `String`.
1184 /// ### Why is this bad?
1185 /// `.push_str(s)` is clearer
1189 /// let abc = "abc";
1190 /// let def = String::from("def");
1191 /// let mut s = String::new();
1192 /// s.extend(abc.chars());
1193 /// s.extend(def.chars());
1195 /// The correct use would be:
1197 /// let abc = "abc";
1198 /// let def = String::from("def");
1199 /// let mut s = String::new();
1200 /// s.push_str(abc);
1201 /// s.push_str(&def);
1203 #[clippy::version = "pre 1.29.0"]
1204 pub STRING_EXTEND_CHARS,
1206 "using `x.extend(s.chars())` where s is a `&str` or `String`"
1209 declare_clippy_lint! {
1210 /// ### What it does
1211 /// Checks for the use of `.cloned().collect()` on slice to
1214 /// ### Why is this bad?
1215 /// `.to_vec()` is clearer
1219 /// let s = [1, 2, 3, 4, 5];
1220 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
1222 /// The better use would be:
1224 /// let s = [1, 2, 3, 4, 5];
1225 /// let s2: Vec<isize> = s.to_vec();
1227 #[clippy::version = "pre 1.29.0"]
1228 pub ITER_CLONED_COLLECT,
1230 "using `.cloned().collect()` on slice to create a `Vec`"
1233 declare_clippy_lint! {
1234 /// ### What it does
1235 /// Checks for usage of `_.chars().last()` or
1236 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1238 /// ### Why is this bad?
1239 /// Readability, this can be written more concisely as
1240 /// `_.ends_with(_)`.
1244 /// # let name = "_";
1247 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1250 /// name.ends_with('_') || name.ends_with('-');
1252 #[clippy::version = "pre 1.29.0"]
1255 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1258 declare_clippy_lint! {
1259 /// ### What it does
1260 /// Checks for usage of `.as_ref()` or `.as_mut()` where the
1261 /// types before and after the call are the same.
1263 /// ### Why is this bad?
1264 /// The call is unnecessary.
1268 /// # fn do_stuff(x: &[i32]) {}
1269 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1270 /// do_stuff(x.as_ref());
1272 /// The correct use would be:
1274 /// # fn do_stuff(x: &[i32]) {}
1275 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1278 #[clippy::version = "pre 1.29.0"]
1281 "using `as_ref` where the types before and after the call are the same"
1284 declare_clippy_lint! {
1285 /// ### What it does
1286 /// Checks for using `fold` when a more succinct alternative exists.
1287 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1288 /// `sum` or `product`.
1290 /// ### Why is this bad?
1295 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1297 /// This could be written as:
1299 /// let _ = (0..3).any(|x| x > 2);
1301 #[clippy::version = "pre 1.29.0"]
1302 pub UNNECESSARY_FOLD,
1304 "using `fold` when a more succinct alternative exists"
1307 declare_clippy_lint! {
1308 /// ### What it does
1309 /// Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1310 /// More specifically it checks if the closure provided is only performing one of the
1311 /// filter or map operations and suggests the appropriate option.
1313 /// ### Why is this bad?
1314 /// Complexity. The intent is also clearer if only a single
1315 /// operation is being performed.
1319 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1321 /// // As there is no transformation of the argument this could be written as:
1322 /// let _ = (0..3).filter(|&x| x > 2);
1326 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1328 /// // As there is no conditional check on the argument this could be written as:
1329 /// let _ = (0..4).map(|x| x + 1);
1331 #[clippy::version = "1.31.0"]
1332 pub UNNECESSARY_FILTER_MAP,
1334 "using `filter_map` when a more succinct alternative exists"
1337 declare_clippy_lint! {
1338 /// ### What it does
1339 /// Checks for `into_iter` calls on references which should be replaced by `iter`
1342 /// ### Why is this bad?
1343 /// Readability. Calling `into_iter` on a reference will not move out its
1344 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1345 /// `iter_mut` directly.
1350 /// let _ = (&vec![3, 4, 5]).into_iter();
1353 /// let _ = (&vec![3, 4, 5]).iter();
1355 #[clippy::version = "1.32.0"]
1356 pub INTO_ITER_ON_REF,
1358 "using `.into_iter()` on a reference"
1361 declare_clippy_lint! {
1362 /// ### What it does
1363 /// Checks for calls to `map` followed by a `count`.
1365 /// ### Why is this bad?
1366 /// It looks suspicious. Maybe `map` was confused with `filter`.
1367 /// If the `map` call is intentional, this should be rewritten
1368 /// using `inspect`. Or, if you intend to drive the iterator to
1369 /// completion, you can just use `for_each` instead.
1373 /// let _ = (0..3).map(|x| x + 2).count();
1375 #[clippy::version = "1.39.0"]
1378 "suspicious usage of map"
1381 declare_clippy_lint! {
1382 /// ### What it does
1383 /// Checks for `MaybeUninit::uninit().assume_init()`.
1385 /// ### Why is this bad?
1386 /// For most types, this is undefined behavior.
1388 /// ### Known problems
1389 /// For now, we accept empty tuples and tuples / arrays
1390 /// of `MaybeUninit`. There may be other types that allow uninitialized
1391 /// data, but those are not yet rigorously defined.
1395 /// // Beware the UB
1396 /// use std::mem::MaybeUninit;
1398 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1401 /// Note that the following is OK:
1404 /// use std::mem::MaybeUninit;
1406 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1407 /// MaybeUninit::uninit().assume_init()
1410 #[clippy::version = "1.39.0"]
1411 pub UNINIT_ASSUMED_INIT,
1413 "`MaybeUninit::uninit().assume_init()`"
1416 declare_clippy_lint! {
1417 /// ### What it does
1418 /// Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1420 /// ### Why is this bad?
1421 /// These can be written simply with `saturating_add/sub` methods.
1425 /// # let y: u32 = 0;
1426 /// # let x: u32 = 100;
1427 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1428 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1431 /// can be written using dedicated methods for saturating addition/subtraction as:
1434 /// # let y: u32 = 0;
1435 /// # let x: u32 = 100;
1436 /// let add = x.saturating_add(y);
1437 /// let sub = x.saturating_sub(y);
1439 #[clippy::version = "1.39.0"]
1440 pub MANUAL_SATURATING_ARITHMETIC,
1442 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1445 declare_clippy_lint! {
1446 /// ### What it does
1447 /// Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1448 /// zero-sized types
1450 /// ### Why is this bad?
1451 /// This is a no-op, and likely unintended
1455 /// unsafe { (&() as *const ()).offset(1) };
1457 #[clippy::version = "1.41.0"]
1460 "Check for offset calculations on raw pointers to zero-sized types"
1463 declare_clippy_lint! {
1464 /// ### What it does
1465 /// Checks for `FileType::is_file()`.
1467 /// ### Why is this bad?
1468 /// When people testing a file type with `FileType::is_file`
1469 /// they are testing whether a path is something they can get bytes from. But
1470 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1471 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1476 /// let metadata = std::fs::metadata("foo.txt")?;
1477 /// let filetype = metadata.file_type();
1479 /// if filetype.is_file() {
1482 /// # Ok::<_, std::io::Error>(())
1486 /// should be written as:
1490 /// let metadata = std::fs::metadata("foo.txt")?;
1491 /// let filetype = metadata.file_type();
1493 /// if !filetype.is_dir() {
1496 /// # Ok::<_, std::io::Error>(())
1499 #[clippy::version = "1.42.0"]
1500 pub FILETYPE_IS_FILE,
1502 "`FileType::is_file` is not recommended to test for readable file type"
1505 declare_clippy_lint! {
1506 /// ### What it does
1507 /// Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1509 /// ### Why is this bad?
1510 /// Readability, this can be written more concisely as
1515 /// # let opt = Some("".to_string());
1516 /// opt.as_ref().map(String::as_str)
1519 /// Can be written as
1521 /// # let opt = Some("".to_string());
1525 #[clippy::version = "1.42.0"]
1526 pub OPTION_AS_REF_DEREF,
1528 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1531 declare_clippy_lint! {
1532 /// ### What it does
1533 /// Checks for usage of `iter().next()` on a Slice or an Array
1535 /// ### Why is this bad?
1536 /// These can be shortened into `.get()`
1540 /// # let a = [1, 2, 3];
1541 /// # let b = vec![1, 2, 3];
1542 /// a[2..].iter().next();
1543 /// b.iter().next();
1545 /// should be written as:
1547 /// # let a = [1, 2, 3];
1548 /// # let b = vec![1, 2, 3];
1552 #[clippy::version = "1.46.0"]
1553 pub ITER_NEXT_SLICE,
1555 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1558 declare_clippy_lint! {
1559 /// ### What it does
1560 /// Warns when using `push_str`/`insert_str` with a single-character string literal
1561 /// where `push`/`insert` with a `char` would work fine.
1563 /// ### Why is this bad?
1564 /// It's less clear that we are pushing a single character.
1568 /// let mut string = String::new();
1569 /// string.insert_str(0, "R");
1570 /// string.push_str("R");
1572 /// Could be written as
1574 /// let mut string = String::new();
1575 /// string.insert(0, 'R');
1576 /// string.push('R');
1578 #[clippy::version = "1.49.0"]
1579 pub SINGLE_CHAR_ADD_STR,
1581 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1584 declare_clippy_lint! {
1585 /// ### What it does
1586 /// As the counterpart to `or_fun_call`, this lint looks for unnecessary
1587 /// lazily evaluated closures on `Option` and `Result`.
1589 /// This lint suggests changing the following functions, when eager evaluation results in
1591 /// - `unwrap_or_else` to `unwrap_or`
1592 /// - `and_then` to `and`
1593 /// - `or_else` to `or`
1594 /// - `get_or_insert_with` to `get_or_insert`
1595 /// - `ok_or_else` to `ok_or`
1597 /// ### Why is this bad?
1598 /// Using eager evaluation is shorter and simpler in some cases.
1600 /// ### Known problems
1601 /// It is possible, but not recommended for `Deref` and `Index` to have
1602 /// side effects. Eagerly evaluating them can change the semantics of the program.
1606 /// // example code where clippy issues a warning
1607 /// let opt: Option<u32> = None;
1609 /// opt.unwrap_or_else(|| 42);
1613 /// let opt: Option<u32> = None;
1615 /// opt.unwrap_or(42);
1617 #[clippy::version = "1.48.0"]
1618 pub UNNECESSARY_LAZY_EVALUATIONS,
1620 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1623 declare_clippy_lint! {
1624 /// ### What it does
1625 /// Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1627 /// ### Why is this bad?
1628 /// Using `try_for_each` instead is more readable and idiomatic.
1632 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1636 /// (0..3).try_for_each(|t| Err(t));
1638 #[clippy::version = "1.49.0"]
1639 pub MAP_COLLECT_RESULT_UNIT,
1641 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1644 declare_clippy_lint! {
1645 /// ### What it does
1646 /// Checks for `from_iter()` function calls on types that implement the `FromIterator`
1649 /// ### Why is this bad?
1650 /// It is recommended style to use collect. See
1651 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1655 /// use std::iter::FromIterator;
1657 /// let five_fives = std::iter::repeat(5).take(5);
1659 /// let v = Vec::from_iter(five_fives);
1661 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1665 /// let five_fives = std::iter::repeat(5).take(5);
1667 /// let v: Vec<i32> = five_fives.collect();
1669 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1671 #[clippy::version = "1.49.0"]
1672 pub FROM_ITER_INSTEAD_OF_COLLECT,
1674 "use `.collect()` instead of `::from_iter()`"
1677 declare_clippy_lint! {
1678 /// ### What it does
1679 /// Checks for usage of `inspect().for_each()`.
1681 /// ### Why is this bad?
1682 /// It is the same as performing the computation
1683 /// inside `inspect` at the beginning of the closure in `for_each`.
1687 /// [1,2,3,4,5].iter()
1688 /// .inspect(|&x| println!("inspect the number: {}", x))
1689 /// .for_each(|&x| {
1690 /// assert!(x >= 0);
1693 /// Can be written as
1695 /// [1,2,3,4,5].iter()
1696 /// .for_each(|&x| {
1697 /// println!("inspect the number: {}", x);
1698 /// assert!(x >= 0);
1701 #[clippy::version = "1.51.0"]
1702 pub INSPECT_FOR_EACH,
1704 "using `.inspect().for_each()`, which can be replaced with `.for_each()`"
1707 declare_clippy_lint! {
1708 /// ### What it does
1709 /// Checks for usage of `filter_map(|x| x)`.
1711 /// ### Why is this bad?
1712 /// Readability, this can be written more concisely by using `flatten`.
1716 /// # let iter = vec![Some(1)].into_iter();
1717 /// iter.filter_map(|x| x);
1721 /// # let iter = vec![Some(1)].into_iter();
1724 #[clippy::version = "1.52.0"]
1725 pub FILTER_MAP_IDENTITY,
1727 "call to `filter_map` where `flatten` is sufficient"
1730 declare_clippy_lint! {
1731 /// ### What it does
1732 /// Checks for instances of `map(f)` where `f` is the identity function.
1734 /// ### Why is this bad?
1735 /// It can be written more concisely without the call to `map`.
1739 /// let x = [1, 2, 3];
1740 /// let y: Vec<_> = x.iter().map(|x| x).map(|x| 2*x).collect();
1744 /// let x = [1, 2, 3];
1745 /// let y: Vec<_> = x.iter().map(|x| 2*x).collect();
1747 #[clippy::version = "1.52.0"]
1750 "using iterator.map(|x| x)"
1753 declare_clippy_lint! {
1754 /// ### What it does
1755 /// Checks for the use of `.bytes().nth()`.
1757 /// ### Why is this bad?
1758 /// `.as_bytes().get()` is more efficient and more
1764 /// let _ = "Hello".bytes().nth(3);
1767 /// let _ = "Hello".as_bytes().get(3);
1769 #[clippy::version = "1.52.0"]
1772 "replace `.bytes().nth()` with `.as_bytes().get()`"
1775 declare_clippy_lint! {
1776 /// ### What it does
1777 /// Checks for the usage of `_.to_owned()`, `vec.to_vec()`, or similar when calling `_.clone()` would be clearer.
1779 /// ### Why is this bad?
1780 /// These methods do the same thing as `_.clone()` but may be confusing as
1781 /// to why we are calling `to_vec` on something that is already a `Vec` or calling `to_owned` on something that is already owned.
1785 /// let a = vec![1, 2, 3];
1786 /// let b = a.to_vec();
1787 /// let c = a.to_owned();
1791 /// let a = vec![1, 2, 3];
1792 /// let b = a.clone();
1793 /// let c = a.clone();
1795 #[clippy::version = "1.52.0"]
1798 "implicitly cloning a value by invoking a function on its dereferenced type"
1801 declare_clippy_lint! {
1802 /// ### What it does
1803 /// Checks for the use of `.iter().count()`.
1805 /// ### Why is this bad?
1806 /// `.len()` is more efficient and more
1812 /// let some_vec = vec![0, 1, 2, 3];
1813 /// let _ = some_vec.iter().count();
1814 /// let _ = &some_vec[..].iter().count();
1817 /// let some_vec = vec![0, 1, 2, 3];
1818 /// let _ = some_vec.len();
1819 /// let _ = &some_vec[..].len();
1821 #[clippy::version = "1.52.0"]
1824 "replace `.iter().count()` with `.len()`"
1827 declare_clippy_lint! {
1828 /// ### What it does
1829 /// Checks for calls to [`splitn`]
1830 /// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
1831 /// related functions with either zero or one splits.
1833 /// ### Why is this bad?
1834 /// These calls don't actually split the value and are
1835 /// likely to be intended as a different number.
1841 /// for x in s.splitn(1, ":") {
1847 /// for x in s.splitn(2, ":") {
1851 #[clippy::version = "1.54.0"]
1852 pub SUSPICIOUS_SPLITN,
1854 "checks for `.splitn(0, ..)` and `.splitn(1, ..)`"
1857 declare_clippy_lint! {
1858 /// ### What it does
1859 /// Checks for manual implementations of `str::repeat`
1861 /// ### Why is this bad?
1862 /// These are both harder to read, as well as less performant.
1867 /// let x: String = std::iter::repeat('x').take(10).collect();
1870 /// let x: String = "x".repeat(10);
1872 #[clippy::version = "1.54.0"]
1873 pub MANUAL_STR_REPEAT,
1875 "manual implementation of `str::repeat`"
1878 declare_clippy_lint! {
1879 /// ### What it does
1880 /// Checks for usages of `str::splitn(2, _)`
1882 /// ### Why is this bad?
1883 /// `split_once` is both clearer in intent and slightly more efficient.
1888 /// let (key, value) = _.splitn(2, '=').next_tuple()?;
1889 /// let value = _.splitn(2, '=').nth(1)?;
1892 /// let (key, value) = _.split_once('=')?;
1893 /// let value = _.split_once('=')?.1;
1895 #[clippy::version = "1.57.0"]
1896 pub MANUAL_SPLIT_ONCE,
1898 "replace `.splitn(2, pat)` with `.split_once(pat)`"
1901 declare_clippy_lint! {
1902 /// ### What it does
1903 /// Checks for usages of `str::splitn` (or `str::rsplitn`) where using `str::split` would be the same.
1904 /// ### Why is this bad?
1905 /// The function `split` is simpler and there is no performance difference in these cases, considering
1906 /// that both functions return a lazy iterator.
1910 /// let str = "key=value=add";
1911 /// let _ = str.splitn(3, '=').next().unwrap();
1916 /// let str = "key=value=add";
1917 /// let _ = str.split('=').next().unwrap();
1919 #[clippy::version = "1.58.0"]
1920 pub NEEDLESS_SPLITN,
1922 "usages of `str::splitn` that can be replaced with `str::split`"
1925 declare_clippy_lint! {
1926 /// ### What it does
1927 /// Checks for unnecessary calls to [`ToOwned::to_owned`](https://doc.rust-lang.org/std/borrow/trait.ToOwned.html#tymethod.to_owned)
1928 /// and other `to_owned`-like functions.
1930 /// ### Why is this bad?
1931 /// The unnecessary calls result in useless allocations.
1933 /// ### Known problems
1934 /// `unnecessary_to_owned` can falsely trigger if `IntoIterator::into_iter` is applied to an
1935 /// owned copy of a resource and the resource is later used mutably. See
1936 /// [#8148](https://github.com/rust-lang/rust-clippy/issues/8148).
1940 /// let path = std::path::Path::new("x");
1941 /// foo(&path.to_string_lossy().to_string());
1942 /// fn foo(s: &str) {}
1946 /// let path = std::path::Path::new("x");
1947 /// foo(&path.to_string_lossy());
1948 /// fn foo(s: &str) {}
1950 #[clippy::version = "1.58.0"]
1951 pub UNNECESSARY_TO_OWNED,
1953 "unnecessary calls to `to_owned`-like functions"
1956 pub struct Methods {
1957 avoid_breaking_exported_api: bool,
1958 msrv: Option<RustcVersion>,
1963 pub fn new(avoid_breaking_exported_api: bool, msrv: Option<RustcVersion>) -> Self {
1965 avoid_breaking_exported_api,
1971 impl_lint_pass!(Methods => [
1974 SHOULD_IMPLEMENT_TRAIT,
1975 WRONG_SELF_CONVENTION,
1977 UNWRAP_OR_ELSE_DEFAULT,
1979 RESULT_MAP_OR_INTO_OPTION,
1981 BIND_INSTEAD_OF_MAP,
1989 ITER_OVEREAGER_CLONED,
1990 CLONED_INSTEAD_OF_COPIED,
1992 INEFFICIENT_TO_STRING,
1994 SINGLE_CHAR_PATTERN,
1995 SINGLE_CHAR_ADD_STR,
1999 FILTER_MAP_IDENTITY,
2007 ITERATOR_STEP_BY_ZERO,
2015 STRING_EXTEND_CHARS,
2016 ITER_CLONED_COLLECT,
2019 UNNECESSARY_FILTER_MAP,
2022 UNINIT_ASSUMED_INIT,
2023 MANUAL_SATURATING_ARITHMETIC,
2026 OPTION_AS_REF_DEREF,
2027 UNNECESSARY_LAZY_EVALUATIONS,
2028 MAP_COLLECT_RESULT_UNIT,
2029 FROM_ITER_INSTEAD_OF_COLLECT,
2037 UNNECESSARY_TO_OWNED,
2040 /// Extracts a method call name, args, and `Span` of the method name.
2041 fn method_call<'tcx>(recv: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx str, &'tcx [hir::Expr<'tcx>], Span)> {
2042 if let ExprKind::MethodCall(path, args, _) = recv.kind {
2043 if !args.iter().any(|e| e.span.from_expansion()) {
2044 let name = path.ident.name.as_str();
2045 return Some((name, args, path.ident.span));
2051 impl<'tcx> LateLintPass<'tcx> for Methods {
2052 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
2053 if expr.span.from_expansion() {
2057 check_methods(cx, expr, self.msrv.as_ref());
2060 hir::ExprKind::Call(func, args) => {
2061 from_iter_instead_of_collect::check(cx, expr, args, func);
2063 hir::ExprKind::MethodCall(method_call, args, _) => {
2064 let method_span = method_call.ident.span;
2065 or_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2066 expect_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2067 clone_on_copy::check(cx, expr, method_call.ident.name, args);
2068 clone_on_ref_ptr::check(cx, expr, method_call.ident.name, args);
2069 inefficient_to_string::check(cx, expr, method_call.ident.name, args);
2070 single_char_add_str::check(cx, expr, args);
2071 into_iter_on_ref::check(cx, expr, method_span, method_call.ident.name, args);
2072 single_char_pattern::check(cx, expr, method_call.ident.name, args);
2073 unnecessary_to_owned::check(cx, expr, method_call.ident.name, args);
2075 hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
2076 let mut info = BinaryExprInfo {
2080 eq: op.node == hir::BinOpKind::Eq,
2082 lint_binary_expr_with_method_call(cx, &mut info);
2088 #[allow(clippy::too_many_lines)]
2089 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
2090 if in_external_macro(cx.sess(), impl_item.span) {
2093 let name = impl_item.ident.name.as_str();
2094 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
2095 let item = cx.tcx.hir().expect_item(parent);
2096 let self_ty = cx.tcx.type_of(item.def_id);
2098 let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
2100 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
2101 if let Some(first_arg) = iter_input_pats(sig.decl, cx.tcx.hir().body(id)).next();
2103 let method_sig = cx.tcx.fn_sig(impl_item.def_id);
2104 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
2106 let first_arg_ty = &method_sig.inputs().iter().next();
2108 // check conventions w.r.t. conversion method names and predicates
2109 if let Some(first_arg_ty) = first_arg_ty;
2112 // if this impl block implements a trait, lint in trait definition instead
2113 if !implements_trait && cx.access_levels.is_exported(impl_item.def_id) {
2114 // check missing trait implementations
2115 for method_config in &TRAIT_METHODS {
2116 if name == method_config.method_name &&
2117 sig.decl.inputs.len() == method_config.param_count &&
2118 method_config.output_type.matches(&sig.decl.output) &&
2119 method_config.self_kind.matches(cx, self_ty, first_arg_ty) &&
2120 fn_header_equals(method_config.fn_header, sig.header) &&
2121 method_config.lifetime_param_cond(impl_item)
2125 SHOULD_IMPLEMENT_TRAIT,
2128 "method `{}` can be confused for the standard trait method `{}::{}`",
2129 method_config.method_name,
2130 method_config.trait_name,
2131 method_config.method_name
2135 "consider implementing the trait `{}` or choosing a less ambiguous method name",
2136 method_config.trait_name
2143 if sig.decl.implicit_self.has_implicit_self()
2144 && !(self.avoid_breaking_exported_api
2145 && cx.access_levels.is_exported(impl_item.def_id))
2147 wrong_self_convention::check(
2160 // if this impl block implements a trait, lint in trait definition instead
2161 if implements_trait {
2165 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
2166 let ret_ty = return_ty(cx, impl_item.hir_id());
2168 // walk the return type and check for Self (this does not check associated types)
2169 if let Some(self_adt) = self_ty.ty_adt_def() {
2170 if contains_adt_constructor(ret_ty, self_adt) {
2173 } else if contains_ty(ret_ty, self_ty) {
2177 // if return type is impl trait, check the associated types
2178 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
2179 // one of the associated types must be Self
2180 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
2181 if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
2182 let assoc_ty = match projection_predicate.term {
2183 ty::Term::Ty(ty) => ty,
2184 ty::Term::Const(_c) => continue,
2186 // walk the associated type and check for Self
2187 if let Some(self_adt) = self_ty.ty_adt_def() {
2188 if contains_adt_constructor(assoc_ty, self_adt) {
2191 } else if contains_ty(assoc_ty, self_ty) {
2198 if name == "new" && !TyS::same_type(ret_ty, self_ty) {
2203 "methods called `new` usually return `Self`",
2209 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
2210 if in_external_macro(cx.tcx.sess, item.span) {
2215 if let TraitItemKind::Fn(ref sig, _) = item.kind;
2216 if sig.decl.implicit_self.has_implicit_self();
2217 if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
2220 let first_arg_span = first_arg_ty.span;
2221 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
2222 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2223 wrong_self_convention::check(
2225 item.ident.name.as_str(),
2236 if item.ident.name == sym::new;
2237 if let TraitItemKind::Fn(_, _) = item.kind;
2238 let ret_ty = return_ty(cx, item.hir_id());
2239 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2240 if !contains_ty(ret_ty, self_ty);
2247 "methods called `new` usually return `Self`",
2253 extract_msrv_attr!(LateContext);
2256 #[allow(clippy::too_many_lines)]
2257 fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Option<&RustcVersion>) {
2258 if let Some((name, [recv, args @ ..], span)) = method_call(expr) {
2259 match (name, args) {
2260 ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
2261 zst_offset::check(cx, expr, recv);
2263 ("and_then", [arg]) => {
2264 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, recv, arg);
2265 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, recv, arg);
2266 if !biom_option_linted && !biom_result_linted {
2267 unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
2270 ("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
2271 ("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
2272 ("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
2273 ("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span, msrv),
2274 ("collect", []) => match method_call(recv) {
2275 Some((name @ ("cloned" | "copied"), [recv2], _)) => {
2276 iter_cloned_collect::check(cx, name, expr, recv2);
2278 Some(("map", [m_recv, m_arg], _)) => {
2279 map_collect_result_unit::check(cx, expr, m_recv, m_arg, recv);
2281 Some(("take", [take_self_arg, take_arg], _)) => {
2282 if meets_msrv(msrv, &msrvs::STR_REPEAT) {
2283 manual_str_repeat::check(cx, expr, recv, take_self_arg, take_arg);
2288 (name @ "count", args @ []) => match method_call(recv) {
2289 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2290 Some((name2 @ ("into_iter" | "iter" | "iter_mut"), [recv2], _)) => {
2291 iter_count::check(cx, expr, recv2, name2);
2293 Some(("map", [_, arg], _)) => suspicious_map::check(cx, expr, recv, arg),
2296 ("expect", [_]) => match method_call(recv) {
2297 Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
2298 _ => expect_used::check(cx, expr, recv),
2300 ("extend", [arg]) => {
2301 string_extend_chars::check(cx, expr, recv, arg);
2302 extend_with_drain::check(cx, expr, recv, arg);
2304 ("filter_map", [arg]) => {
2305 unnecessary_filter_map::check(cx, expr, arg);
2306 filter_map_identity::check(cx, expr, arg, span);
2308 ("flat_map", [arg]) => {
2309 flat_map_identity::check(cx, expr, arg, span);
2310 flat_map_option::check(cx, expr, arg, span);
2312 (name @ "flatten", args @ []) => match method_call(recv) {
2313 Some(("map", [recv, map_arg], _)) => map_flatten::check(cx, expr, recv, map_arg),
2314 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2317 ("fold", [init, acc]) => unnecessary_fold::check(cx, expr, init, acc, span),
2318 ("for_each", [_]) => {
2319 if let Some(("inspect", [_, _], span2)) = method_call(recv) {
2320 inspect_for_each::check(cx, expr, span2);
2323 ("get_or_insert_with", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "get_or_insert"),
2324 ("is_file", []) => filetype_is_file::check(cx, expr, recv),
2325 ("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
2326 ("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
2327 ("last", args @ []) | ("skip", args @ [_]) => {
2328 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2329 if let ("cloned", []) = (name2, args2) {
2330 iter_overeager_cloned::check(cx, expr, recv2, name, args);
2334 ("map", [m_arg]) => {
2335 if let Some((name, [recv2, args @ ..], span2)) = method_call(recv) {
2336 match (name, args) {
2337 ("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, msrv),
2338 ("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, msrv),
2339 ("filter", [f_arg]) => {
2340 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
2342 ("find", [f_arg]) => filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, true),
2346 map_identity::check(cx, expr, recv, m_arg, span);
2348 ("map_or", [def, map]) => option_map_or_none::check(cx, expr, recv, def, map),
2349 (name @ "next", args @ []) => {
2350 if let Some((name2, [recv2, args2 @ ..], _)) = method_call(recv) {
2351 match (name2, args2) {
2352 ("cloned", []) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2353 ("filter", [arg]) => filter_next::check(cx, expr, recv2, arg),
2354 ("filter_map", [arg]) => filter_map_next::check(cx, expr, recv2, arg, msrv),
2355 ("iter", []) => iter_next_slice::check(cx, expr, recv2),
2356 ("skip", [arg]) => iter_skip_next::check(cx, expr, recv2, arg),
2357 ("skip_while", [_]) => skip_while_next::check(cx, expr),
2362 ("nth", args @ [n_arg]) => match method_call(recv) {
2363 Some(("bytes", [recv2], _)) => bytes_nth::check(cx, expr, recv2, n_arg),
2364 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2365 Some(("iter", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, false),
2366 Some(("iter_mut", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, true),
2367 _ => iter_nth_zero::check(cx, expr, recv, n_arg),
2369 ("ok_or_else", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "ok_or"),
2370 ("or_else", [arg]) => {
2371 if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, recv, arg) {
2372 unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
2375 ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
2376 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2377 suspicious_splitn::check(cx, name, expr, recv, count);
2378 if count == 2 && meets_msrv(msrv, &msrvs::STR_SPLIT_ONCE) {
2379 str_splitn::check_manual_split_once(cx, name, expr, recv, pat_arg);
2382 str_splitn::check_needless_splitn(cx, name, expr, recv, pat_arg, count);
2386 ("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
2387 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2388 suspicious_splitn::check(cx, name, expr, recv, count);
2391 ("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
2392 ("take", args @ [_arg]) => {
2393 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2394 if let ("cloned", []) = (name2, args2) {
2395 iter_overeager_cloned::check(cx, expr, recv2, name, args);
2399 ("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
2400 implicit_clone::check(cx, name, expr, recv);
2402 ("unwrap", []) => match method_call(recv) {
2403 Some(("get", [recv, get_arg], _)) => get_unwrap::check(cx, expr, recv, get_arg, false),
2404 Some(("get_mut", [recv, get_arg], _)) => get_unwrap::check(cx, expr, recv, get_arg, true),
2405 _ => unwrap_used::check(cx, expr, recv),
2407 ("unwrap_or", [u_arg]) => match method_call(recv) {
2408 Some((arith @ ("checked_add" | "checked_sub" | "checked_mul"), [lhs, rhs], _)) => {
2409 manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, &arith["checked_".len()..]);
2411 Some(("map", [m_recv, m_arg], span)) => {
2412 option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span);
2416 ("unwrap_or_else", [u_arg]) => match method_call(recv) {
2417 Some(("map", [recv, map_arg], _)) if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, msrv) => {},
2419 unwrap_or_else_default::check(cx, expr, recv, u_arg);
2420 unnecessary_lazy_eval::check(cx, expr, recv, u_arg, "unwrap_or");
2428 fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, is_some: bool) {
2429 if let Some((name @ ("find" | "position" | "rposition"), [f_recv, arg], span)) = method_call(recv) {
2430 search_is_some::check(cx, expr, name, is_some, f_recv, arg, recv, span);
2434 /// Used for `lint_binary_expr_with_method_call`.
2435 #[derive(Copy, Clone)]
2436 struct BinaryExprInfo<'a> {
2437 expr: &'a hir::Expr<'a>,
2438 chain: &'a hir::Expr<'a>,
2439 other: &'a hir::Expr<'a>,
2443 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2444 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
2445 macro_rules! lint_with_both_lhs_and_rhs {
2446 ($func:expr, $cx:expr, $info:ident) => {
2447 if !$func($cx, $info) {
2448 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2449 if $func($cx, $info) {
2456 lint_with_both_lhs_and_rhs!(chars_next_cmp::check, cx, info);
2457 lint_with_both_lhs_and_rhs!(chars_last_cmp::check, cx, info);
2458 lint_with_both_lhs_and_rhs!(chars_next_cmp_with_unwrap::check, cx, info);
2459 lint_with_both_lhs_and_rhs!(chars_last_cmp_with_unwrap::check, cx, info);
2462 const FN_HEADER: hir::FnHeader = hir::FnHeader {
2463 unsafety: hir::Unsafety::Normal,
2464 constness: hir::Constness::NotConst,
2465 asyncness: hir::IsAsync::NotAsync,
2466 abi: rustc_target::spec::abi::Abi::Rust,
2469 struct ShouldImplTraitCase {
2470 trait_name: &'static str,
2471 method_name: &'static str,
2473 fn_header: hir::FnHeader,
2474 // implicit self kind expected (none, self, &self, ...)
2475 self_kind: SelfKind,
2476 // checks against the output type
2477 output_type: OutType,
2478 // certain methods with explicit lifetimes can't implement the equivalent trait method
2479 lint_explicit_lifetime: bool,
2481 impl ShouldImplTraitCase {
2483 trait_name: &'static str,
2484 method_name: &'static str,
2486 fn_header: hir::FnHeader,
2487 self_kind: SelfKind,
2488 output_type: OutType,
2489 lint_explicit_lifetime: bool,
2490 ) -> ShouldImplTraitCase {
2491 ShouldImplTraitCase {
2498 lint_explicit_lifetime,
2502 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
2503 self.lint_explicit_lifetime
2504 || !impl_item.generics.params.iter().any(|p| {
2507 hir::GenericParamKind::Lifetime {
2508 kind: hir::LifetimeParamKind::Explicit
2516 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
2517 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2518 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2519 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2520 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2521 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2522 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2523 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2524 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2525 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2526 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2527 // FIXME: default doesn't work
2528 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
2529 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2530 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2531 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2532 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
2533 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
2534 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2535 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2536 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
2537 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2538 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2539 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2540 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2541 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2542 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
2543 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2544 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2545 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2546 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2547 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2550 #[derive(Clone, Copy, PartialEq, Debug)]
2559 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2560 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
2561 if ty == parent_ty {
2563 } else if ty.is_box() {
2564 ty.boxed_ty() == parent_ty
2565 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
2566 if let ty::Adt(_, substs) = ty.kind() {
2567 substs.types().next().map_or(false, |t| t == parent_ty)
2576 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2577 if let ty::Ref(_, t, m) = *ty.kind() {
2578 return m == mutability && t == parent_ty;
2581 let trait_path = match mutability {
2582 hir::Mutability::Not => &paths::ASREF_TRAIT,
2583 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
2586 let trait_def_id = match get_trait_def_id(cx, trait_path) {
2588 None => return false,
2590 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
2593 fn matches_none<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2594 !matches_value(cx, parent_ty, ty)
2595 && !matches_ref(cx, hir::Mutability::Not, parent_ty, ty)
2596 && !matches_ref(cx, hir::Mutability::Mut, parent_ty, ty)
2600 Self::Value => matches_value(cx, parent_ty, ty),
2601 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
2602 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
2603 Self::No => matches_none(cx, parent_ty, ty),
2608 fn description(self) -> &'static str {
2610 Self::Value => "`self` by value",
2611 Self::Ref => "`self` by reference",
2612 Self::RefMut => "`self` by mutable reference",
2613 Self::No => "no `self`",
2618 #[derive(Clone, Copy)]
2627 fn matches(self, ty: &hir::FnRetTy<'_>) -> bool {
2628 let is_unit = |ty: &hir::Ty<'_>| matches!(ty.kind, hir::TyKind::Tup(&[]));
2630 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
2631 (Self::Unit, &hir::FnRetTy::Return(ty)) if is_unit(ty) => true,
2632 (Self::Bool, &hir::FnRetTy::Return(ty)) if is_bool(ty) => true,
2633 (Self::Any, &hir::FnRetTy::Return(ty)) if !is_unit(ty) => true,
2634 (Self::Ref, &hir::FnRetTy::Return(ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
2640 fn is_bool(ty: &hir::Ty<'_>) -> bool {
2641 if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
2642 matches!(path.res, Res::PrimTy(PrimTy::Bool))
2648 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
2649 expected.constness == actual.constness
2650 && expected.unsafety == actual.unsafety
2651 && expected.asyncness == actual.asyncness