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};
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
569 /// `_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
573 /// let vec = vec![vec![1]];
574 /// let opt = Some(5);
577 /// vec.iter().map(|x| x.iter()).flatten();
578 /// opt.map(|x| Some(x * 2)).flatten();
581 /// vec.iter().flat_map(|x| x.iter());
582 /// opt.and_then(|x| Some(x * 2));
584 #[clippy::version = "1.31.0"]
587 "using combinations of `flatten` and `map` which can usually be written as a single method call"
590 declare_clippy_lint! {
592 /// Checks for usage of `_.filter(_).map(_)` that can be written more simply
593 /// as `filter_map(_)`.
595 /// ### Why is this bad?
596 /// Redundant code in the `filter` and `map` operations is poor style and
603 /// .filter(|n| n.checked_add(1).is_some())
604 /// .map(|n| n.checked_add(1).unwrap());
609 /// (0_i32..10).filter_map(|n| n.checked_add(1));
611 #[clippy::version = "1.51.0"]
612 pub MANUAL_FILTER_MAP,
614 "using `_.filter(_).map(_)` in a way that can be written more simply as `filter_map(_)`"
617 declare_clippy_lint! {
619 /// Checks for usage of `_.find(_).map(_)` that can be written more simply
620 /// as `find_map(_)`.
622 /// ### Why is this bad?
623 /// Redundant code in the `find` and `map` operations is poor style and
630 /// .find(|n| n.checked_add(1).is_some())
631 /// .map(|n| n.checked_add(1).unwrap());
636 /// (0_i32..10).find_map(|n| n.checked_add(1));
638 #[clippy::version = "1.51.0"]
641 "using `_.find(_).map(_)` in a way that can be written more simply as `find_map(_)`"
644 declare_clippy_lint! {
646 /// Checks for usage of `_.filter_map(_).next()`.
648 /// ### Why is this bad?
649 /// Readability, this can be written more concisely as
654 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
656 /// Can be written as
659 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
661 #[clippy::version = "1.36.0"]
664 "using combination of `filter_map` and `next` which can usually be written as a single method call"
667 declare_clippy_lint! {
669 /// Checks for usage of `flat_map(|x| x)`.
671 /// ### Why is this bad?
672 /// Readability, this can be written more concisely by using `flatten`.
676 /// # let iter = vec![vec![0]].into_iter();
677 /// iter.flat_map(|x| x);
679 /// Can be written as
681 /// # let iter = vec![vec![0]].into_iter();
684 #[clippy::version = "1.39.0"]
685 pub FLAT_MAP_IDENTITY,
687 "call to `flat_map` where `flatten` is sufficient"
690 declare_clippy_lint! {
692 /// Checks for an iterator or string search (such as `find()`,
693 /// `position()`, or `rposition()`) followed by a call to `is_some()` or `is_none()`.
695 /// ### Why is this bad?
696 /// Readability, this can be written more concisely as:
697 /// * `_.any(_)`, or `_.contains(_)` for `is_some()`,
698 /// * `!_.any(_)`, or `!_.contains(_)` for `is_none()`.
702 /// let vec = vec![1];
703 /// vec.iter().find(|x| **x == 0).is_some();
705 /// let _ = "hello world".find("world").is_none();
707 /// Could be written as
709 /// let vec = vec![1];
710 /// vec.iter().any(|x| *x == 0);
712 /// let _ = !"hello world".contains("world");
714 #[clippy::version = "pre 1.29.0"]
717 "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()`)"
720 declare_clippy_lint! {
722 /// Checks for usage of `.chars().next()` on a `str` to check
723 /// if it starts with a given char.
725 /// ### Why is this bad?
726 /// Readability, this can be written more concisely as
727 /// `_.starts_with(_)`.
731 /// let name = "foo";
732 /// if name.chars().next() == Some('_') {};
734 /// Could be written as
736 /// let name = "foo";
737 /// if name.starts_with('_') {};
739 #[clippy::version = "pre 1.29.0"]
742 "using `.chars().next()` to check if a string starts with a char"
745 declare_clippy_lint! {
747 /// Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
748 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
749 /// `unwrap_or_default` instead.
751 /// ### Why is this bad?
752 /// The function will always be called and potentially
753 /// allocate an object acting as the default.
755 /// ### Known problems
756 /// If the function has side-effects, not calling it will
757 /// change the semantic of the program, but you shouldn't rely on that anyway.
761 /// # let foo = Some(String::new());
762 /// foo.unwrap_or(String::new());
764 /// this can instead be written:
766 /// # let foo = Some(String::new());
767 /// foo.unwrap_or_else(String::new);
771 /// # let foo = Some(String::new());
772 /// foo.unwrap_or_default();
774 #[clippy::version = "pre 1.29.0"]
777 "using any `*or` method with a function call, which suggests `*or_else`"
780 declare_clippy_lint! {
782 /// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
783 /// etc., and suggests to use `unwrap_or_else` instead
785 /// ### Why is this bad?
786 /// The function will always be called.
788 /// ### Known problems
789 /// If the function has side-effects, not calling it will
790 /// change the semantics of the program, but you shouldn't rely on that anyway.
794 /// # let foo = Some(String::new());
795 /// # let err_code = "418";
796 /// # let err_msg = "I'm a teapot";
797 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
801 /// # let foo = Some(String::new());
802 /// # let err_code = "418";
803 /// # let err_msg = "I'm a teapot";
804 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
806 /// this can instead be written:
808 /// # let foo = Some(String::new());
809 /// # let err_code = "418";
810 /// # let err_msg = "I'm a teapot";
811 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
813 #[clippy::version = "pre 1.29.0"]
816 "using any `expect` method with a function call"
819 declare_clippy_lint! {
821 /// Checks for usage of `.clone()` on a `Copy` type.
823 /// ### Why is this bad?
824 /// The only reason `Copy` types implement `Clone` is for
825 /// generics, not for using the `clone` method on a concrete type.
831 #[clippy::version = "pre 1.29.0"]
834 "using `clone` on a `Copy` type"
837 declare_clippy_lint! {
839 /// Checks for usage of `.clone()` on a ref-counted pointer,
840 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
841 /// function syntax instead (e.g., `Rc::clone(foo)`).
843 /// ### Why is this bad?
844 /// Calling '.clone()' on an Rc, Arc, or Weak
845 /// can obscure the fact that only the pointer is being cloned, not the underlying
850 /// # use std::rc::Rc;
851 /// let x = Rc::new(1);
859 #[clippy::version = "pre 1.29.0"]
860 pub CLONE_ON_REF_PTR,
862 "using 'clone' on a ref-counted pointer"
865 declare_clippy_lint! {
867 /// Checks for usage of `.clone()` on an `&&T`.
869 /// ### Why is this bad?
870 /// Cloning an `&&T` copies the inner `&T`, instead of
871 /// cloning the underlying `T`.
878 /// let z = y.clone();
879 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
882 #[clippy::version = "pre 1.29.0"]
883 pub CLONE_DOUBLE_REF,
885 "using `clone` on `&&T`"
888 declare_clippy_lint! {
890 /// Checks for usage of `.to_string()` on an `&&T` where
891 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
893 /// ### Why is this bad?
894 /// This bypasses the specialized implementation of
895 /// `ToString` and instead goes through the more expensive string formatting
900 /// // Generic implementation for `T: Display` is used (slow)
901 /// ["foo", "bar"].iter().map(|s| s.to_string());
903 /// // OK, the specialized impl is used
904 /// ["foo", "bar"].iter().map(|&s| s.to_string());
906 #[clippy::version = "1.40.0"]
907 pub INEFFICIENT_TO_STRING,
909 "using `to_string` on `&&T` where `T: ToString`"
912 declare_clippy_lint! {
914 /// Checks for `new` not returning a type that contains `Self`.
916 /// ### Why is this bad?
917 /// As a convention, `new` methods are used to make a new
918 /// instance of a type.
921 /// In an impl block:
924 /// # struct NotAFoo;
926 /// fn new() -> NotAFoo {
936 /// // Bad. The type name must contain `Self`
937 /// fn new() -> Bar {
945 /// # struct FooError;
947 /// // Good. Return type contains `Self`
948 /// fn new() -> Result<Foo, FooError> {
954 /// Or in a trait definition:
956 /// pub trait Trait {
957 /// // Bad. The type name must contain `Self`
963 /// pub trait Trait {
964 /// // Good. Return type contains `Self`
965 /// fn new() -> Self;
968 #[clippy::version = "pre 1.29.0"]
971 "not returning type containing `Self` in a `new` method"
974 declare_clippy_lint! {
976 /// Checks for string methods that receive a single-character
977 /// `str` as an argument, e.g., `_.split("x")`.
979 /// ### Why is this bad?
980 /// Performing these methods using a `char` is faster than
983 /// ### Known problems
984 /// Does not catch multi-byte unicode characters.
993 #[clippy::version = "pre 1.29.0"]
994 pub SINGLE_CHAR_PATTERN,
996 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
999 declare_clippy_lint! {
1000 /// ### What it does
1001 /// Checks for calling `.step_by(0)` on iterators which panics.
1003 /// ### Why is this bad?
1004 /// This very much looks like an oversight. Use `panic!()` instead if you
1005 /// actually intend to panic.
1008 /// ```rust,should_panic
1009 /// for x in (0..100).step_by(0) {
1013 #[clippy::version = "pre 1.29.0"]
1014 pub ITERATOR_STEP_BY_ZERO,
1016 "using `Iterator::step_by(0)`, which will panic at runtime"
1019 declare_clippy_lint! {
1020 /// ### What it does
1021 /// Checks for indirect collection of populated `Option`
1023 /// ### Why is this bad?
1024 /// `Option` is like a collection of 0-1 things, so `flatten`
1025 /// automatically does this without suspicious-looking `unwrap` calls.
1029 /// let _ = std::iter::empty::<Option<i32>>().filter(Option::is_some).map(Option::unwrap);
1033 /// let _ = std::iter::empty::<Option<i32>>().flatten();
1035 #[clippy::version = "1.53.0"]
1036 pub OPTION_FILTER_MAP,
1038 "filtering `Option` for `Some` then force-unwrapping, which can be one type-safe operation"
1041 declare_clippy_lint! {
1042 /// ### What it does
1043 /// Checks for the use of `iter.nth(0)`.
1045 /// ### Why is this bad?
1046 /// `iter.next()` is equivalent to
1047 /// `iter.nth(0)`, as they both consume the next element,
1048 /// but is more readable.
1052 /// # use std::collections::HashSet;
1054 /// # let mut s = HashSet::new();
1056 /// let x = s.iter().nth(0);
1059 /// # let mut s = HashSet::new();
1061 /// let x = s.iter().next();
1063 #[clippy::version = "1.42.0"]
1066 "replace `iter.nth(0)` with `iter.next()`"
1069 declare_clippy_lint! {
1070 /// ### What it does
1071 /// Checks for use of `.iter().nth()` (and the related
1072 /// `.iter_mut().nth()`) on standard library types with *O*(1) element access.
1074 /// ### Why is this bad?
1075 /// `.get()` and `.get_mut()` are more efficient and more
1080 /// let some_vec = vec![0, 1, 2, 3];
1081 /// let bad_vec = some_vec.iter().nth(3);
1082 /// let bad_slice = &some_vec[..].iter().nth(3);
1084 /// The correct use would be:
1086 /// let some_vec = vec![0, 1, 2, 3];
1087 /// let bad_vec = some_vec.get(3);
1088 /// let bad_slice = &some_vec[..].get(3);
1090 #[clippy::version = "pre 1.29.0"]
1093 "using `.iter().nth()` on a standard library type with O(1) element access"
1096 declare_clippy_lint! {
1097 /// ### What it does
1098 /// Checks for use of `.skip(x).next()` on iterators.
1100 /// ### Why is this bad?
1101 /// `.nth(x)` is cleaner
1105 /// let some_vec = vec![0, 1, 2, 3];
1106 /// let bad_vec = some_vec.iter().skip(3).next();
1107 /// let bad_slice = &some_vec[..].iter().skip(3).next();
1109 /// The correct use would be:
1111 /// let some_vec = vec![0, 1, 2, 3];
1112 /// let bad_vec = some_vec.iter().nth(3);
1113 /// let bad_slice = &some_vec[..].iter().nth(3);
1115 #[clippy::version = "pre 1.29.0"]
1118 "using `.skip(x).next()` on an iterator"
1121 declare_clippy_lint! {
1122 /// ### What it does
1123 /// Checks for use of `.get().unwrap()` (or
1124 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
1126 /// ### Why is this bad?
1127 /// Using the Index trait (`[]`) is more clear and more
1130 /// ### Known problems
1131 /// Not a replacement for error handling: Using either
1132 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
1133 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
1134 /// temporary placeholder for dealing with the `Option` type, then this does
1135 /// not mitigate the need for error handling. If there is a chance that `.get()`
1136 /// will be `None` in your program, then it is advisable that the `None` case
1137 /// is handled in a future refactor instead of using `.unwrap()` or the Index
1142 /// let mut some_vec = vec![0, 1, 2, 3];
1143 /// let last = some_vec.get(3).unwrap();
1144 /// *some_vec.get_mut(0).unwrap() = 1;
1146 /// The correct use would be:
1148 /// let mut some_vec = vec![0, 1, 2, 3];
1149 /// let last = some_vec[3];
1150 /// some_vec[0] = 1;
1152 #[clippy::version = "pre 1.29.0"]
1155 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
1158 declare_clippy_lint! {
1159 /// ### What it does
1160 /// Checks for occurrences where one vector gets extended instead of append
1162 /// ### Why is this bad?
1163 /// Using `append` instead of `extend` is more concise and faster
1167 /// let mut a = vec![1, 2, 3];
1168 /// let mut b = vec![4, 5, 6];
1171 /// a.extend(b.drain(..));
1174 /// a.append(&mut b);
1176 #[clippy::version = "1.55.0"]
1177 pub EXTEND_WITH_DRAIN,
1179 "using vec.append(&mut vec) to move the full range of a vecor to another"
1182 declare_clippy_lint! {
1183 /// ### What it does
1184 /// Checks for the use of `.extend(s.chars())` where s is a
1185 /// `&str` or `String`.
1187 /// ### Why is this bad?
1188 /// `.push_str(s)` is clearer
1192 /// let abc = "abc";
1193 /// let def = String::from("def");
1194 /// let mut s = String::new();
1195 /// s.extend(abc.chars());
1196 /// s.extend(def.chars());
1198 /// The correct use would be:
1200 /// let abc = "abc";
1201 /// let def = String::from("def");
1202 /// let mut s = String::new();
1203 /// s.push_str(abc);
1204 /// s.push_str(&def);
1206 #[clippy::version = "pre 1.29.0"]
1207 pub STRING_EXTEND_CHARS,
1209 "using `x.extend(s.chars())` where s is a `&str` or `String`"
1212 declare_clippy_lint! {
1213 /// ### What it does
1214 /// Checks for the use of `.cloned().collect()` on slice to
1217 /// ### Why is this bad?
1218 /// `.to_vec()` is clearer
1222 /// let s = [1, 2, 3, 4, 5];
1223 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
1225 /// The better use would be:
1227 /// let s = [1, 2, 3, 4, 5];
1228 /// let s2: Vec<isize> = s.to_vec();
1230 #[clippy::version = "pre 1.29.0"]
1231 pub ITER_CLONED_COLLECT,
1233 "using `.cloned().collect()` on slice to create a `Vec`"
1236 declare_clippy_lint! {
1237 /// ### What it does
1238 /// Checks for usage of `_.chars().last()` or
1239 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1241 /// ### Why is this bad?
1242 /// Readability, this can be written more concisely as
1243 /// `_.ends_with(_)`.
1247 /// # let name = "_";
1250 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1253 /// name.ends_with('_') || name.ends_with('-');
1255 #[clippy::version = "pre 1.29.0"]
1258 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1261 declare_clippy_lint! {
1262 /// ### What it does
1263 /// Checks for usage of `.as_ref()` or `.as_mut()` where the
1264 /// types before and after the call are the same.
1266 /// ### Why is this bad?
1267 /// The call is unnecessary.
1271 /// # fn do_stuff(x: &[i32]) {}
1272 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1273 /// do_stuff(x.as_ref());
1275 /// The correct use would be:
1277 /// # fn do_stuff(x: &[i32]) {}
1278 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1281 #[clippy::version = "pre 1.29.0"]
1284 "using `as_ref` where the types before and after the call are the same"
1287 declare_clippy_lint! {
1288 /// ### What it does
1289 /// Checks for using `fold` when a more succinct alternative exists.
1290 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1291 /// `sum` or `product`.
1293 /// ### Why is this bad?
1298 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1300 /// This could be written as:
1302 /// let _ = (0..3).any(|x| x > 2);
1304 #[clippy::version = "pre 1.29.0"]
1305 pub UNNECESSARY_FOLD,
1307 "using `fold` when a more succinct alternative exists"
1310 declare_clippy_lint! {
1311 /// ### What it does
1312 /// Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1313 /// More specifically it checks if the closure provided is only performing one of the
1314 /// filter or map operations and suggests the appropriate option.
1316 /// ### Why is this bad?
1317 /// Complexity. The intent is also clearer if only a single
1318 /// operation is being performed.
1322 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1324 /// // As there is no transformation of the argument this could be written as:
1325 /// let _ = (0..3).filter(|&x| x > 2);
1329 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1331 /// // As there is no conditional check on the argument this could be written as:
1332 /// let _ = (0..4).map(|x| x + 1);
1334 #[clippy::version = "1.31.0"]
1335 pub UNNECESSARY_FILTER_MAP,
1337 "using `filter_map` when a more succinct alternative exists"
1340 declare_clippy_lint! {
1341 /// ### What it does
1342 /// Checks for `into_iter` calls on references which should be replaced by `iter`
1345 /// ### Why is this bad?
1346 /// Readability. Calling `into_iter` on a reference will not move out its
1347 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1348 /// `iter_mut` directly.
1353 /// let _ = (&vec![3, 4, 5]).into_iter();
1356 /// let _ = (&vec![3, 4, 5]).iter();
1358 #[clippy::version = "1.32.0"]
1359 pub INTO_ITER_ON_REF,
1361 "using `.into_iter()` on a reference"
1364 declare_clippy_lint! {
1365 /// ### What it does
1366 /// Checks for calls to `map` followed by a `count`.
1368 /// ### Why is this bad?
1369 /// It looks suspicious. Maybe `map` was confused with `filter`.
1370 /// If the `map` call is intentional, this should be rewritten
1371 /// using `inspect`. Or, if you intend to drive the iterator to
1372 /// completion, you can just use `for_each` instead.
1376 /// let _ = (0..3).map(|x| x + 2).count();
1378 #[clippy::version = "1.39.0"]
1381 "suspicious usage of map"
1384 declare_clippy_lint! {
1385 /// ### What it does
1386 /// Checks for `MaybeUninit::uninit().assume_init()`.
1388 /// ### Why is this bad?
1389 /// For most types, this is undefined behavior.
1391 /// ### Known problems
1392 /// For now, we accept empty tuples and tuples / arrays
1393 /// of `MaybeUninit`. There may be other types that allow uninitialized
1394 /// data, but those are not yet rigorously defined.
1398 /// // Beware the UB
1399 /// use std::mem::MaybeUninit;
1401 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1404 /// Note that the following is OK:
1407 /// use std::mem::MaybeUninit;
1409 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1410 /// MaybeUninit::uninit().assume_init()
1413 #[clippy::version = "1.39.0"]
1414 pub UNINIT_ASSUMED_INIT,
1416 "`MaybeUninit::uninit().assume_init()`"
1419 declare_clippy_lint! {
1420 /// ### What it does
1421 /// Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1423 /// ### Why is this bad?
1424 /// These can be written simply with `saturating_add/sub` methods.
1428 /// # let y: u32 = 0;
1429 /// # let x: u32 = 100;
1430 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1431 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1434 /// can be written using dedicated methods for saturating addition/subtraction as:
1437 /// # let y: u32 = 0;
1438 /// # let x: u32 = 100;
1439 /// let add = x.saturating_add(y);
1440 /// let sub = x.saturating_sub(y);
1442 #[clippy::version = "1.39.0"]
1443 pub MANUAL_SATURATING_ARITHMETIC,
1445 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1448 declare_clippy_lint! {
1449 /// ### What it does
1450 /// Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1451 /// zero-sized types
1453 /// ### Why is this bad?
1454 /// This is a no-op, and likely unintended
1458 /// unsafe { (&() as *const ()).offset(1) };
1460 #[clippy::version = "1.41.0"]
1463 "Check for offset calculations on raw pointers to zero-sized types"
1466 declare_clippy_lint! {
1467 /// ### What it does
1468 /// Checks for `FileType::is_file()`.
1470 /// ### Why is this bad?
1471 /// When people testing a file type with `FileType::is_file`
1472 /// they are testing whether a path is something they can get bytes from. But
1473 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1474 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1479 /// let metadata = std::fs::metadata("foo.txt")?;
1480 /// let filetype = metadata.file_type();
1482 /// if filetype.is_file() {
1485 /// # Ok::<_, std::io::Error>(())
1489 /// should be written as:
1493 /// let metadata = std::fs::metadata("foo.txt")?;
1494 /// let filetype = metadata.file_type();
1496 /// if !filetype.is_dir() {
1499 /// # Ok::<_, std::io::Error>(())
1502 #[clippy::version = "1.42.0"]
1503 pub FILETYPE_IS_FILE,
1505 "`FileType::is_file` is not recommended to test for readable file type"
1508 declare_clippy_lint! {
1509 /// ### What it does
1510 /// Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1512 /// ### Why is this bad?
1513 /// Readability, this can be written more concisely as
1518 /// # let opt = Some("".to_string());
1519 /// opt.as_ref().map(String::as_str)
1522 /// Can be written as
1524 /// # let opt = Some("".to_string());
1528 #[clippy::version = "1.42.0"]
1529 pub OPTION_AS_REF_DEREF,
1531 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1534 declare_clippy_lint! {
1535 /// ### What it does
1536 /// Checks for usage of `iter().next()` on a Slice or an Array
1538 /// ### Why is this bad?
1539 /// These can be shortened into `.get()`
1543 /// # let a = [1, 2, 3];
1544 /// # let b = vec![1, 2, 3];
1545 /// a[2..].iter().next();
1546 /// b.iter().next();
1548 /// should be written as:
1550 /// # let a = [1, 2, 3];
1551 /// # let b = vec![1, 2, 3];
1555 #[clippy::version = "1.46.0"]
1556 pub ITER_NEXT_SLICE,
1558 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1561 declare_clippy_lint! {
1562 /// ### What it does
1563 /// Warns when using `push_str`/`insert_str` with a single-character string literal
1564 /// where `push`/`insert` with a `char` would work fine.
1566 /// ### Why is this bad?
1567 /// It's less clear that we are pushing a single character.
1571 /// let mut string = String::new();
1572 /// string.insert_str(0, "R");
1573 /// string.push_str("R");
1575 /// Could be written as
1577 /// let mut string = String::new();
1578 /// string.insert(0, 'R');
1579 /// string.push('R');
1581 #[clippy::version = "1.49.0"]
1582 pub SINGLE_CHAR_ADD_STR,
1584 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1587 declare_clippy_lint! {
1588 /// ### What it does
1589 /// As the counterpart to `or_fun_call`, this lint looks for unnecessary
1590 /// lazily evaluated closures on `Option` and `Result`.
1592 /// This lint suggests changing the following functions, when eager evaluation results in
1594 /// - `unwrap_or_else` to `unwrap_or`
1595 /// - `and_then` to `and`
1596 /// - `or_else` to `or`
1597 /// - `get_or_insert_with` to `get_or_insert`
1598 /// - `ok_or_else` to `ok_or`
1600 /// ### Why is this bad?
1601 /// Using eager evaluation is shorter and simpler in some cases.
1603 /// ### Known problems
1604 /// It is possible, but not recommended for `Deref` and `Index` to have
1605 /// side effects. Eagerly evaluating them can change the semantics of the program.
1609 /// // example code where clippy issues a warning
1610 /// let opt: Option<u32> = None;
1612 /// opt.unwrap_or_else(|| 42);
1616 /// let opt: Option<u32> = None;
1618 /// opt.unwrap_or(42);
1620 #[clippy::version = "1.48.0"]
1621 pub UNNECESSARY_LAZY_EVALUATIONS,
1623 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1626 declare_clippy_lint! {
1627 /// ### What it does
1628 /// Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1630 /// ### Why is this bad?
1631 /// Using `try_for_each` instead is more readable and idiomatic.
1635 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1639 /// (0..3).try_for_each(|t| Err(t));
1641 #[clippy::version = "1.49.0"]
1642 pub MAP_COLLECT_RESULT_UNIT,
1644 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1647 declare_clippy_lint! {
1648 /// ### What it does
1649 /// Checks for `from_iter()` function calls on types that implement the `FromIterator`
1652 /// ### Why is this bad?
1653 /// It is recommended style to use collect. See
1654 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1658 /// use std::iter::FromIterator;
1660 /// let five_fives = std::iter::repeat(5).take(5);
1662 /// let v = Vec::from_iter(five_fives);
1664 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1668 /// let five_fives = std::iter::repeat(5).take(5);
1670 /// let v: Vec<i32> = five_fives.collect();
1672 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1674 #[clippy::version = "1.49.0"]
1675 pub FROM_ITER_INSTEAD_OF_COLLECT,
1677 "use `.collect()` instead of `::from_iter()`"
1680 declare_clippy_lint! {
1681 /// ### What it does
1682 /// Checks for usage of `inspect().for_each()`.
1684 /// ### Why is this bad?
1685 /// It is the same as performing the computation
1686 /// inside `inspect` at the beginning of the closure in `for_each`.
1690 /// [1,2,3,4,5].iter()
1691 /// .inspect(|&x| println!("inspect the number: {}", x))
1692 /// .for_each(|&x| {
1693 /// assert!(x >= 0);
1696 /// Can be written as
1698 /// [1,2,3,4,5].iter()
1699 /// .for_each(|&x| {
1700 /// println!("inspect the number: {}", x);
1701 /// assert!(x >= 0);
1704 #[clippy::version = "1.51.0"]
1705 pub INSPECT_FOR_EACH,
1707 "using `.inspect().for_each()`, which can be replaced with `.for_each()`"
1710 declare_clippy_lint! {
1711 /// ### What it does
1712 /// Checks for usage of `filter_map(|x| x)`.
1714 /// ### Why is this bad?
1715 /// Readability, this can be written more concisely by using `flatten`.
1719 /// # let iter = vec![Some(1)].into_iter();
1720 /// iter.filter_map(|x| x);
1724 /// # let iter = vec![Some(1)].into_iter();
1727 #[clippy::version = "1.52.0"]
1728 pub FILTER_MAP_IDENTITY,
1730 "call to `filter_map` where `flatten` is sufficient"
1733 declare_clippy_lint! {
1734 /// ### What it does
1735 /// Checks for instances of `map(f)` where `f` is the identity function.
1737 /// ### Why is this bad?
1738 /// It can be written more concisely without the call to `map`.
1742 /// let x = [1, 2, 3];
1743 /// let y: Vec<_> = x.iter().map(|x| x).map(|x| 2*x).collect();
1747 /// let x = [1, 2, 3];
1748 /// let y: Vec<_> = x.iter().map(|x| 2*x).collect();
1750 #[clippy::version = "1.52.0"]
1753 "using iterator.map(|x| x)"
1756 declare_clippy_lint! {
1757 /// ### What it does
1758 /// Checks for the use of `.bytes().nth()`.
1760 /// ### Why is this bad?
1761 /// `.as_bytes().get()` is more efficient and more
1767 /// let _ = "Hello".bytes().nth(3);
1770 /// let _ = "Hello".as_bytes().get(3);
1772 #[clippy::version = "1.52.0"]
1775 "replace `.bytes().nth()` with `.as_bytes().get()`"
1778 declare_clippy_lint! {
1779 /// ### What it does
1780 /// Checks for the usage of `_.to_owned()`, `vec.to_vec()`, or similar when calling `_.clone()` would be clearer.
1782 /// ### Why is this bad?
1783 /// These methods do the same thing as `_.clone()` but may be confusing as
1784 /// to why we are calling `to_vec` on something that is already a `Vec` or calling `to_owned` on something that is already owned.
1788 /// let a = vec![1, 2, 3];
1789 /// let b = a.to_vec();
1790 /// let c = a.to_owned();
1794 /// let a = vec![1, 2, 3];
1795 /// let b = a.clone();
1796 /// let c = a.clone();
1798 #[clippy::version = "1.52.0"]
1801 "implicitly cloning a value by invoking a function on its dereferenced type"
1804 declare_clippy_lint! {
1805 /// ### What it does
1806 /// Checks for the use of `.iter().count()`.
1808 /// ### Why is this bad?
1809 /// `.len()` is more efficient and more
1815 /// let some_vec = vec![0, 1, 2, 3];
1816 /// let _ = some_vec.iter().count();
1817 /// let _ = &some_vec[..].iter().count();
1820 /// let some_vec = vec![0, 1, 2, 3];
1821 /// let _ = some_vec.len();
1822 /// let _ = &some_vec[..].len();
1824 #[clippy::version = "1.52.0"]
1827 "replace `.iter().count()` with `.len()`"
1830 declare_clippy_lint! {
1831 /// ### What it does
1832 /// Checks for calls to [`splitn`]
1833 /// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
1834 /// related functions with either zero or one splits.
1836 /// ### Why is this bad?
1837 /// These calls don't actually split the value and are
1838 /// likely to be intended as a different number.
1844 /// for x in s.splitn(1, ":") {
1850 /// for x in s.splitn(2, ":") {
1854 #[clippy::version = "1.54.0"]
1855 pub SUSPICIOUS_SPLITN,
1857 "checks for `.splitn(0, ..)` and `.splitn(1, ..)`"
1860 declare_clippy_lint! {
1861 /// ### What it does
1862 /// Checks for manual implementations of `str::repeat`
1864 /// ### Why is this bad?
1865 /// These are both harder to read, as well as less performant.
1870 /// let x: String = std::iter::repeat('x').take(10).collect();
1873 /// let x: String = "x".repeat(10);
1875 #[clippy::version = "1.54.0"]
1876 pub MANUAL_STR_REPEAT,
1878 "manual implementation of `str::repeat`"
1881 declare_clippy_lint! {
1882 /// ### What it does
1883 /// Checks for usages of `str::splitn(2, _)`
1885 /// ### Why is this bad?
1886 /// `split_once` is both clearer in intent and slightly more efficient.
1891 /// let (key, value) = _.splitn(2, '=').next_tuple()?;
1892 /// let value = _.splitn(2, '=').nth(1)?;
1895 /// let (key, value) = _.split_once('=')?;
1896 /// let value = _.split_once('=')?.1;
1898 #[clippy::version = "1.57.0"]
1899 pub MANUAL_SPLIT_ONCE,
1901 "replace `.splitn(2, pat)` with `.split_once(pat)`"
1904 declare_clippy_lint! {
1905 /// ### What it does
1906 /// Checks for usages of `str::splitn` (or `str::rsplitn`) where using `str::split` would be the same.
1907 /// ### Why is this bad?
1908 /// The function `split` is simpler and there is no performance difference in these cases, considering
1909 /// that both functions return a lazy iterator.
1913 /// let str = "key=value=add";
1914 /// let _ = str.splitn(3, '=').next().unwrap();
1919 /// let str = "key=value=add";
1920 /// let _ = str.split('=').next().unwrap();
1922 #[clippy::version = "1.58.0"]
1923 pub NEEDLESS_SPLITN,
1925 "usages of `str::splitn` that can be replaced with `str::split`"
1928 declare_clippy_lint! {
1929 /// ### What it does
1930 /// Checks for unnecessary calls to [`ToOwned::to_owned`](https://doc.rust-lang.org/std/borrow/trait.ToOwned.html#tymethod.to_owned)
1931 /// and other `to_owned`-like functions.
1933 /// ### Why is this bad?
1934 /// The unnecessary calls result in useless allocations.
1936 /// ### Known problems
1937 /// `unnecessary_to_owned` can falsely trigger if `IntoIterator::into_iter` is applied to an
1938 /// owned copy of a resource and the resource is later used mutably. See
1939 /// [#8148](https://github.com/rust-lang/rust-clippy/issues/8148).
1943 /// let path = std::path::Path::new("x");
1944 /// foo(&path.to_string_lossy().to_string());
1945 /// fn foo(s: &str) {}
1949 /// let path = std::path::Path::new("x");
1950 /// foo(&path.to_string_lossy());
1951 /// fn foo(s: &str) {}
1953 #[clippy::version = "1.58.0"]
1954 pub UNNECESSARY_TO_OWNED,
1956 "unnecessary calls to `to_owned`-like functions"
1959 pub struct Methods {
1960 avoid_breaking_exported_api: bool,
1961 msrv: Option<RustcVersion>,
1966 pub fn new(avoid_breaking_exported_api: bool, msrv: Option<RustcVersion>) -> Self {
1968 avoid_breaking_exported_api,
1974 impl_lint_pass!(Methods => [
1977 SHOULD_IMPLEMENT_TRAIT,
1978 WRONG_SELF_CONVENTION,
1980 UNWRAP_OR_ELSE_DEFAULT,
1982 RESULT_MAP_OR_INTO_OPTION,
1984 BIND_INSTEAD_OF_MAP,
1992 ITER_OVEREAGER_CLONED,
1993 CLONED_INSTEAD_OF_COPIED,
1995 INEFFICIENT_TO_STRING,
1997 SINGLE_CHAR_PATTERN,
1998 SINGLE_CHAR_ADD_STR,
2002 FILTER_MAP_IDENTITY,
2010 ITERATOR_STEP_BY_ZERO,
2018 STRING_EXTEND_CHARS,
2019 ITER_CLONED_COLLECT,
2022 UNNECESSARY_FILTER_MAP,
2025 UNINIT_ASSUMED_INIT,
2026 MANUAL_SATURATING_ARITHMETIC,
2029 OPTION_AS_REF_DEREF,
2030 UNNECESSARY_LAZY_EVALUATIONS,
2031 MAP_COLLECT_RESULT_UNIT,
2032 FROM_ITER_INSTEAD_OF_COLLECT,
2040 UNNECESSARY_TO_OWNED,
2043 /// Extracts a method call name, args, and `Span` of the method name.
2044 fn method_call<'tcx>(recv: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx str, &'tcx [hir::Expr<'tcx>], Span)> {
2045 if let ExprKind::MethodCall(path, args, _) = recv.kind {
2046 if !args.iter().any(|e| e.span.from_expansion()) {
2047 let name = path.ident.name.as_str();
2048 return Some((name, args, path.ident.span));
2054 impl<'tcx> LateLintPass<'tcx> for Methods {
2055 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
2056 if expr.span.from_expansion() {
2060 check_methods(cx, expr, self.msrv.as_ref());
2063 hir::ExprKind::Call(func, args) => {
2064 from_iter_instead_of_collect::check(cx, expr, args, func);
2066 hir::ExprKind::MethodCall(method_call, args, _) => {
2067 let method_span = method_call.ident.span;
2068 or_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2069 expect_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
2070 clone_on_copy::check(cx, expr, method_call.ident.name, args);
2071 clone_on_ref_ptr::check(cx, expr, method_call.ident.name, args);
2072 inefficient_to_string::check(cx, expr, method_call.ident.name, args);
2073 single_char_add_str::check(cx, expr, args);
2074 into_iter_on_ref::check(cx, expr, method_span, method_call.ident.name, args);
2075 single_char_pattern::check(cx, expr, method_call.ident.name, args);
2076 unnecessary_to_owned::check(cx, expr, method_call.ident.name, args);
2078 hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
2079 let mut info = BinaryExprInfo {
2083 eq: op.node == hir::BinOpKind::Eq,
2085 lint_binary_expr_with_method_call(cx, &mut info);
2091 #[allow(clippy::too_many_lines)]
2092 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
2093 if in_external_macro(cx.sess(), impl_item.span) {
2096 let name = impl_item.ident.name.as_str();
2097 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
2098 let item = cx.tcx.hir().expect_item(parent);
2099 let self_ty = cx.tcx.type_of(item.def_id);
2101 let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
2103 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
2104 if let Some(first_arg) = iter_input_pats(sig.decl, cx.tcx.hir().body(id)).next();
2106 let method_sig = cx.tcx.fn_sig(impl_item.def_id);
2107 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
2109 let first_arg_ty = &method_sig.inputs().iter().next();
2111 // check conventions w.r.t. conversion method names and predicates
2112 if let Some(first_arg_ty) = first_arg_ty;
2115 // if this impl block implements a trait, lint in trait definition instead
2116 if !implements_trait && cx.access_levels.is_exported(impl_item.def_id) {
2117 // check missing trait implementations
2118 for method_config in &TRAIT_METHODS {
2119 if name == method_config.method_name &&
2120 sig.decl.inputs.len() == method_config.param_count &&
2121 method_config.output_type.matches(&sig.decl.output) &&
2122 method_config.self_kind.matches(cx, self_ty, first_arg_ty) &&
2123 fn_header_equals(method_config.fn_header, sig.header) &&
2124 method_config.lifetime_param_cond(impl_item)
2128 SHOULD_IMPLEMENT_TRAIT,
2131 "method `{}` can be confused for the standard trait method `{}::{}`",
2132 method_config.method_name,
2133 method_config.trait_name,
2134 method_config.method_name
2138 "consider implementing the trait `{}` or choosing a less ambiguous method name",
2139 method_config.trait_name
2146 if sig.decl.implicit_self.has_implicit_self()
2147 && !(self.avoid_breaking_exported_api
2148 && cx.access_levels.is_exported(impl_item.def_id))
2150 wrong_self_convention::check(
2163 // if this impl block implements a trait, lint in trait definition instead
2164 if implements_trait {
2168 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
2169 let ret_ty = return_ty(cx, impl_item.hir_id());
2171 // walk the return type and check for Self (this does not check associated types)
2172 if let Some(self_adt) = self_ty.ty_adt_def() {
2173 if contains_adt_constructor(ret_ty, self_adt) {
2176 } else if contains_ty(ret_ty, self_ty) {
2180 // if return type is impl trait, check the associated types
2181 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
2182 // one of the associated types must be Self
2183 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
2184 if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
2185 let assoc_ty = match projection_predicate.term {
2186 ty::Term::Ty(ty) => ty,
2187 ty::Term::Const(_c) => continue,
2189 // walk the associated type and check for Self
2190 if let Some(self_adt) = self_ty.ty_adt_def() {
2191 if contains_adt_constructor(assoc_ty, self_adt) {
2194 } else if contains_ty(assoc_ty, self_ty) {
2201 if name == "new" && ret_ty != self_ty {
2206 "methods called `new` usually return `Self`",
2212 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
2213 if in_external_macro(cx.tcx.sess, item.span) {
2218 if let TraitItemKind::Fn(ref sig, _) = item.kind;
2219 if sig.decl.implicit_self.has_implicit_self();
2220 if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
2223 let first_arg_span = first_arg_ty.span;
2224 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
2225 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2226 wrong_self_convention::check(
2228 item.ident.name.as_str(),
2239 if item.ident.name == sym::new;
2240 if let TraitItemKind::Fn(_, _) = item.kind;
2241 let ret_ty = return_ty(cx, item.hir_id());
2242 let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
2243 if !contains_ty(ret_ty, self_ty);
2250 "methods called `new` usually return `Self`",
2256 extract_msrv_attr!(LateContext);
2259 #[allow(clippy::too_many_lines)]
2260 fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Option<&RustcVersion>) {
2261 if let Some((name, [recv, args @ ..], span)) = method_call(expr) {
2262 match (name, args) {
2263 ("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
2264 zst_offset::check(cx, expr, recv);
2266 ("and_then", [arg]) => {
2267 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, recv, arg);
2268 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, recv, arg);
2269 if !biom_option_linted && !biom_result_linted {
2270 unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
2273 ("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
2274 ("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
2275 ("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
2276 ("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span, msrv),
2277 ("collect", []) => match method_call(recv) {
2278 Some((name @ ("cloned" | "copied"), [recv2], _)) => {
2279 iter_cloned_collect::check(cx, name, expr, recv2);
2281 Some(("map", [m_recv, m_arg], _)) => {
2282 map_collect_result_unit::check(cx, expr, m_recv, m_arg, recv);
2284 Some(("take", [take_self_arg, take_arg], _)) => {
2285 if meets_msrv(msrv, &msrvs::STR_REPEAT) {
2286 manual_str_repeat::check(cx, expr, recv, take_self_arg, take_arg);
2291 (name @ "count", args @ []) => match method_call(recv) {
2292 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2293 Some((name2 @ ("into_iter" | "iter" | "iter_mut"), [recv2], _)) => {
2294 iter_count::check(cx, expr, recv2, name2);
2296 Some(("map", [_, arg], _)) => suspicious_map::check(cx, expr, recv, arg),
2299 ("expect", [_]) => match method_call(recv) {
2300 Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
2301 _ => expect_used::check(cx, expr, recv),
2303 ("extend", [arg]) => {
2304 string_extend_chars::check(cx, expr, recv, arg);
2305 extend_with_drain::check(cx, expr, recv, arg);
2307 ("filter_map", [arg]) => {
2308 unnecessary_filter_map::check(cx, expr, arg);
2309 filter_map_identity::check(cx, expr, arg, span);
2311 ("flat_map", [arg]) => {
2312 flat_map_identity::check(cx, expr, arg, span);
2313 flat_map_option::check(cx, expr, arg, span);
2315 (name @ "flatten", args @ []) => match method_call(recv) {
2316 Some(("map", [recv, map_arg], _)) => map_flatten::check(cx, expr, recv, map_arg),
2317 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2320 ("fold", [init, acc]) => unnecessary_fold::check(cx, expr, init, acc, span),
2321 ("for_each", [_]) => {
2322 if let Some(("inspect", [_, _], span2)) = method_call(recv) {
2323 inspect_for_each::check(cx, expr, span2);
2326 ("get_or_insert_with", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "get_or_insert"),
2327 ("is_file", []) => filetype_is_file::check(cx, expr, recv),
2328 ("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
2329 ("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
2330 ("last", args @ []) | ("skip", args @ [_]) => {
2331 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2332 if let ("cloned", []) = (name2, args2) {
2333 iter_overeager_cloned::check(cx, expr, recv2, name, args);
2337 ("map", [m_arg]) => {
2338 if let Some((name, [recv2, args @ ..], span2)) = method_call(recv) {
2339 match (name, args) {
2340 ("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, msrv),
2341 ("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, msrv),
2342 ("filter", [f_arg]) => {
2343 filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
2345 ("find", [f_arg]) => filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, true),
2349 map_identity::check(cx, expr, recv, m_arg, span);
2351 ("map_or", [def, map]) => option_map_or_none::check(cx, expr, recv, def, map),
2352 (name @ "next", args @ []) => {
2353 if let Some((name2, [recv2, args2 @ ..], _)) = method_call(recv) {
2354 match (name2, args2) {
2355 ("cloned", []) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2356 ("filter", [arg]) => filter_next::check(cx, expr, recv2, arg),
2357 ("filter_map", [arg]) => filter_map_next::check(cx, expr, recv2, arg, msrv),
2358 ("iter", []) => iter_next_slice::check(cx, expr, recv2),
2359 ("skip", [arg]) => iter_skip_next::check(cx, expr, recv2, arg),
2360 ("skip_while", [_]) => skip_while_next::check(cx, expr),
2365 ("nth", args @ [n_arg]) => match method_call(recv) {
2366 Some(("bytes", [recv2], _)) => bytes_nth::check(cx, expr, recv2, n_arg),
2367 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
2368 Some(("iter", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, false),
2369 Some(("iter_mut", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, true),
2370 _ => iter_nth_zero::check(cx, expr, recv, n_arg),
2372 ("ok_or_else", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "ok_or"),
2373 ("or_else", [arg]) => {
2374 if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, recv, arg) {
2375 unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
2378 ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
2379 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2380 suspicious_splitn::check(cx, name, expr, recv, count);
2381 if count == 2 && meets_msrv(msrv, &msrvs::STR_SPLIT_ONCE) {
2382 str_splitn::check_manual_split_once(cx, name, expr, recv, pat_arg);
2385 str_splitn::check_needless_splitn(cx, name, expr, recv, pat_arg, count);
2389 ("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
2390 if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
2391 suspicious_splitn::check(cx, name, expr, recv, count);
2394 ("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
2395 ("take", args @ [_arg]) => {
2396 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
2397 if let ("cloned", []) = (name2, args2) {
2398 iter_overeager_cloned::check(cx, expr, recv2, name, args);
2402 ("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
2403 implicit_clone::check(cx, name, expr, recv);
2406 match method_call(recv) {
2407 Some(("get", [recv, get_arg], _)) => {
2408 get_unwrap::check(cx, expr, recv, get_arg, false);
2410 Some(("get_mut", [recv, get_arg], _)) => {
2411 get_unwrap::check(cx, expr, recv, get_arg, true);
2415 unwrap_used::check(cx, expr, recv);
2417 ("unwrap_or", [u_arg]) => match method_call(recv) {
2418 Some((arith @ ("checked_add" | "checked_sub" | "checked_mul"), [lhs, rhs], _)) => {
2419 manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, &arith["checked_".len()..]);
2421 Some(("map", [m_recv, m_arg], span)) => {
2422 option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span);
2426 ("unwrap_or_else", [u_arg]) => match method_call(recv) {
2427 Some(("map", [recv, map_arg], _)) if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, msrv) => {},
2429 unwrap_or_else_default::check(cx, expr, recv, u_arg);
2430 unnecessary_lazy_eval::check(cx, expr, recv, u_arg, "unwrap_or");
2438 fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, is_some: bool) {
2439 if let Some((name @ ("find" | "position" | "rposition"), [f_recv, arg], span)) = method_call(recv) {
2440 search_is_some::check(cx, expr, name, is_some, f_recv, arg, recv, span);
2444 /// Used for `lint_binary_expr_with_method_call`.
2445 #[derive(Copy, Clone)]
2446 struct BinaryExprInfo<'a> {
2447 expr: &'a hir::Expr<'a>,
2448 chain: &'a hir::Expr<'a>,
2449 other: &'a hir::Expr<'a>,
2453 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2454 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
2455 macro_rules! lint_with_both_lhs_and_rhs {
2456 ($func:expr, $cx:expr, $info:ident) => {
2457 if !$func($cx, $info) {
2458 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2459 if $func($cx, $info) {
2466 lint_with_both_lhs_and_rhs!(chars_next_cmp::check, cx, info);
2467 lint_with_both_lhs_and_rhs!(chars_last_cmp::check, cx, info);
2468 lint_with_both_lhs_and_rhs!(chars_next_cmp_with_unwrap::check, cx, info);
2469 lint_with_both_lhs_and_rhs!(chars_last_cmp_with_unwrap::check, cx, info);
2472 const FN_HEADER: hir::FnHeader = hir::FnHeader {
2473 unsafety: hir::Unsafety::Normal,
2474 constness: hir::Constness::NotConst,
2475 asyncness: hir::IsAsync::NotAsync,
2476 abi: rustc_target::spec::abi::Abi::Rust,
2479 struct ShouldImplTraitCase {
2480 trait_name: &'static str,
2481 method_name: &'static str,
2483 fn_header: hir::FnHeader,
2484 // implicit self kind expected (none, self, &self, ...)
2485 self_kind: SelfKind,
2486 // checks against the output type
2487 output_type: OutType,
2488 // certain methods with explicit lifetimes can't implement the equivalent trait method
2489 lint_explicit_lifetime: bool,
2491 impl ShouldImplTraitCase {
2493 trait_name: &'static str,
2494 method_name: &'static str,
2496 fn_header: hir::FnHeader,
2497 self_kind: SelfKind,
2498 output_type: OutType,
2499 lint_explicit_lifetime: bool,
2500 ) -> ShouldImplTraitCase {
2501 ShouldImplTraitCase {
2508 lint_explicit_lifetime,
2512 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
2513 self.lint_explicit_lifetime
2514 || !impl_item.generics.params.iter().any(|p| {
2517 hir::GenericParamKind::Lifetime {
2518 kind: hir::LifetimeParamKind::Explicit
2526 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
2527 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2528 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2529 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2530 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2531 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2532 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2533 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2534 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2535 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2536 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
2537 // FIXME: default doesn't work
2538 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
2539 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2540 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2541 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2542 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
2543 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
2544 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2545 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
2546 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
2547 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
2548 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
2549 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2550 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2551 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2552 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
2553 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
2554 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2555 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2556 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2557 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
2560 #[derive(Clone, Copy, PartialEq, Debug)]
2569 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2570 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
2571 if ty == parent_ty {
2573 } else if ty.is_box() {
2574 ty.boxed_ty() == parent_ty
2575 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
2576 if let ty::Adt(_, substs) = ty.kind() {
2577 substs.types().next().map_or(false, |t| t == parent_ty)
2586 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2587 if let ty::Ref(_, t, m) = *ty.kind() {
2588 return m == mutability && t == parent_ty;
2591 let trait_path = match mutability {
2592 hir::Mutability::Not => &paths::ASREF_TRAIT,
2593 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
2596 let trait_def_id = match get_trait_def_id(cx, trait_path) {
2598 None => return false,
2600 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
2603 fn matches_none<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2604 !matches_value(cx, parent_ty, ty)
2605 && !matches_ref(cx, hir::Mutability::Not, parent_ty, ty)
2606 && !matches_ref(cx, hir::Mutability::Mut, parent_ty, ty)
2610 Self::Value => matches_value(cx, parent_ty, ty),
2611 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
2612 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
2613 Self::No => matches_none(cx, parent_ty, ty),
2618 fn description(self) -> &'static str {
2620 Self::Value => "`self` by value",
2621 Self::Ref => "`self` by reference",
2622 Self::RefMut => "`self` by mutable reference",
2623 Self::No => "no `self`",
2628 #[derive(Clone, Copy)]
2637 fn matches(self, ty: &hir::FnRetTy<'_>) -> bool {
2638 let is_unit = |ty: &hir::Ty<'_>| matches!(ty.kind, hir::TyKind::Tup(&[]));
2640 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
2641 (Self::Unit, &hir::FnRetTy::Return(ty)) if is_unit(ty) => true,
2642 (Self::Bool, &hir::FnRetTy::Return(ty)) if is_bool(ty) => true,
2643 (Self::Any, &hir::FnRetTy::Return(ty)) if !is_unit(ty) => true,
2644 (Self::Ref, &hir::FnRetTy::Return(ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
2650 fn is_bool(ty: &hir::Ty<'_>) -> bool {
2651 if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
2652 matches!(path.res, Res::PrimTy(PrimTy::Bool))
2658 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
2659 expected.constness == actual.constness
2660 && expected.unsafety == actual.unsafety
2661 && expected.asyncness == actual.asyncness