1 mod bind_instead_of_map;
2 mod inefficient_to_string;
3 mod manual_saturating_arithmetic;
4 mod option_map_unwrap_or;
5 mod unnecessary_filter_map;
6 mod unnecessary_lazy_eval;
12 use bind_instead_of_map::BindInsteadOfMap;
13 use if_chain::if_chain;
15 use rustc_errors::Applicability;
17 use rustc_hir::{TraitItem, TraitItemKind};
18 use rustc_lint::{LateContext, LateLintPass, Lint, LintContext};
19 use rustc_middle::lint::in_external_macro;
20 use rustc_middle::ty::{self, TraitRef, Ty, TyS};
21 use rustc_semver::RustcVersion;
22 use rustc_session::{declare_tool_lint, impl_lint_pass};
23 use rustc_span::source_map::Span;
24 use rustc_span::symbol::{sym, SymbolStr};
25 use rustc_typeck::hir_ty_to_ty;
27 use crate::consts::{constant, Constant};
28 use crate::utils::eager_or_lazy::is_lazyness_candidate;
29 use crate::utils::usage::mutated_variables;
31 contains_return, contains_ty, get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, higher,
32 implements_trait, in_macro, is_copy, is_expn_of, is_type_diagnostic_item, iter_input_pats, last_path_segment,
33 match_def_path, match_qpath, match_trait_method, match_type, match_var, meets_msrv, method_calls,
34 method_chain_args, paths, remove_blocks, return_ty, single_segment_path, snippet, snippet_with_applicability,
35 snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, sugg,
36 walk_ptrs_ty_depth, SpanlessEq,
39 declare_clippy_lint! {
40 /// **What it does:** Checks for `.unwrap()` calls on `Option`s and on `Result`s.
42 /// **Why is this bad?** It is better to handle the `None` or `Err` case,
43 /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
44 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
45 /// `Allow` by default.
47 /// `result.unwrap()` will let the thread panic on `Err` values.
48 /// Normally, you want to implement more sophisticated error handling,
49 /// and propagate errors upwards with `?` operator.
51 /// Even if you want to panic on errors, not all `Error`s implement good
52 /// messages on display. Therefore, it may be beneficial to look at the places
53 /// where they may get displayed. Activate this lint to do just that.
55 /// **Known problems:** None.
59 /// # let opt = Some(1);
65 /// opt.expect("more helpful message");
71 /// # let res: Result<usize, ()> = Ok(1);
77 /// res.expect("more helpful message");
81 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
84 declare_clippy_lint! {
85 /// **What it does:** Checks for `.expect()` calls on `Option`s and `Result`s.
87 /// **Why is this bad?** Usually it is better to handle the `None` or `Err` case.
88 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
89 /// this lint is `Allow` by default.
91 /// `result.expect()` will let the thread panic on `Err`
92 /// values. Normally, you want to implement more sophisticated error handling,
93 /// and propagate errors upwards with `?` operator.
95 /// **Known problems:** None.
99 /// # let opt = Some(1);
102 /// opt.expect("one");
105 /// let opt = Some(1);
112 /// # let res: Result<usize, ()> = Ok(1);
115 /// res.expect("one");
119 /// # Ok::<(), ()>(())
123 "using `.expect()` on `Result` or `Option`, which might be better handled"
126 declare_clippy_lint! {
127 /// **What it does:** Checks for methods that should live in a trait
128 /// implementation of a `std` trait (see [llogiq's blog
129 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
130 /// information) instead of an inherent implementation.
132 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
133 /// the code, often with very little cost. Also people seeing a `mul(...)`
135 /// may expect `*` to work equally, so you should have good reason to disappoint
138 /// **Known problems:** None.
144 /// fn add(&self, other: &X) -> X {
150 pub SHOULD_IMPLEMENT_TRAIT,
152 "defining a method that should be implementing a std trait"
155 declare_clippy_lint! {
156 /// **What it does:** Checks for methods with certain name prefixes and which
157 /// doesn't match how self is taken. The actual rules are:
159 /// |Prefix |`self` taken |
160 /// |-------|----------------------|
161 /// |`as_` |`&self` or `&mut self`|
163 /// |`into_`|`self` |
164 /// |`is_` |`&self` or none |
165 /// |`to_` |`&self` |
167 /// **Why is this bad?** Consistency breeds readability. If you follow the
168 /// conventions, your users won't be surprised that they, e.g., need to supply a
169 /// mutable reference to a `as_..` function.
171 /// **Known problems:** None.
177 /// fn as_str(self) -> &'static str {
183 pub WRONG_SELF_CONVENTION,
185 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
188 declare_clippy_lint! {
189 /// **What it does:** This is the same as
190 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
192 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
194 /// **Known problems:** Actually *renaming* the function may break clients if
195 /// the function is part of the public interface. In that case, be mindful of
196 /// the stability guarantees you've given your users.
202 /// pub fn as_str(self) -> &'a str {
207 pub WRONG_PUB_SELF_CONVENTION,
209 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
212 declare_clippy_lint! {
213 /// **What it does:** Checks for usage of `ok().expect(..)`.
215 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
216 /// directly to get a better error message.
218 /// **Known problems:** The error type needs to implement `Debug`
222 /// # let x = Ok::<_, ()>(());
225 /// x.ok().expect("why did I do this again?");
228 /// x.expect("why did I do this again?");
232 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
235 declare_clippy_lint! {
236 /// **What it does:** Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
237 /// `result.map(_).unwrap_or_else(_)`.
239 /// **Why is this bad?** Readability, these can be written more concisely (resp.) as
240 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
242 /// **Known problems:** The order of the arguments is not in execution order
246 /// # let x = Some(1);
249 /// x.map(|a| a + 1).unwrap_or(0);
252 /// x.map_or(0, |a| a + 1);
258 /// # let x: Result<usize, ()> = Ok(1);
259 /// # fn some_function(foo: ()) -> usize { 1 }
262 /// x.map(|a| a + 1).unwrap_or_else(some_function);
265 /// x.map_or_else(some_function, |a| a + 1);
269 "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)`"
272 declare_clippy_lint! {
273 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
275 /// **Why is this bad?** Readability, this can be written more concisely as
278 /// **Known problems:** The order of the arguments is not in execution order.
282 /// # let opt = Some(1);
285 /// opt.map_or(None, |a| Some(a + 1));
288 /// opt.and_then(|a| Some(a + 1));
290 pub OPTION_MAP_OR_NONE,
292 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
295 declare_clippy_lint! {
296 /// **What it does:** Checks for usage of `_.map_or(None, Some)`.
298 /// **Why is this bad?** Readability, this can be written more concisely as
301 /// **Known problems:** None.
307 /// # let r: Result<u32, &str> = Ok(1);
308 /// assert_eq!(Some(1), r.map_or(None, Some));
313 /// # let r: Result<u32, &str> = Ok(1);
314 /// assert_eq!(Some(1), r.ok());
316 pub RESULT_MAP_OR_INTO_OPTION,
318 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
321 declare_clippy_lint! {
322 /// **What it does:** Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
323 /// `_.or_else(|x| Err(y))`.
325 /// **Why is this bad?** Readability, this can be written more concisely as
326 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
328 /// **Known problems:** None
333 /// # fn opt() -> Option<&'static str> { Some("42") }
334 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
335 /// let _ = opt().and_then(|s| Some(s.len()));
336 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
337 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
340 /// The correct use would be:
343 /// # fn opt() -> Option<&'static str> { Some("42") }
344 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
345 /// let _ = opt().map(|s| s.len());
346 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
347 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
349 pub BIND_INSTEAD_OF_MAP,
351 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
354 declare_clippy_lint! {
355 /// **What it does:** Checks for usage of `_.filter(_).next()`.
357 /// **Why is this bad?** Readability, this can be written more concisely as
360 /// **Known problems:** None.
364 /// # let vec = vec![1];
365 /// vec.iter().filter(|x| **x == 0).next();
367 /// Could be written as
369 /// # let vec = vec![1];
370 /// vec.iter().find(|x| **x == 0);
374 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
377 declare_clippy_lint! {
378 /// **What it does:** Checks for usage of `_.skip_while(condition).next()`.
380 /// **Why is this bad?** Readability, this can be written more concisely as
381 /// `_.find(!condition)`.
383 /// **Known problems:** None.
387 /// # let vec = vec![1];
388 /// vec.iter().skip_while(|x| **x == 0).next();
390 /// Could be written as
392 /// # let vec = vec![1];
393 /// vec.iter().find(|x| **x != 0);
397 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
400 declare_clippy_lint! {
401 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
403 /// **Why is this bad?** Readability, this can be written more concisely as
406 /// **Known problems:**
410 /// let vec = vec![vec![1]];
413 /// vec.iter().map(|x| x.iter()).flatten();
416 /// vec.iter().flat_map(|x| x.iter());
420 "using combinations of `flatten` and `map` which can usually be written as a single method call"
423 declare_clippy_lint! {
424 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
425 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
427 /// **Why is this bad?** Readability, this can be written more concisely as
428 /// `_.filter_map(_)`.
430 /// **Known problems:** Often requires a condition + Option/Iterator creation
431 /// inside the closure.
435 /// let vec = vec![1];
438 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
441 /// vec.iter().filter_map(|x| if *x == 0 {
449 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
452 declare_clippy_lint! {
453 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
455 /// **Why is this bad?** Readability, this can be written more concisely as
458 /// **Known problems:** None
462 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
464 /// Can be written as
467 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
471 "using combination of `filter_map` and `next` which can usually be written as a single method call"
474 declare_clippy_lint! {
475 /// **What it does:** Checks for usage of `flat_map(|x| x)`.
477 /// **Why is this bad?** Readability, this can be written more concisely by using `flatten`.
479 /// **Known problems:** None
483 /// # let iter = vec![vec![0]].into_iter();
484 /// iter.flat_map(|x| x);
486 /// Can be written as
488 /// # let iter = vec![vec![0]].into_iter();
491 pub FLAT_MAP_IDENTITY,
493 "call to `flat_map` where `flatten` is sufficient"
496 declare_clippy_lint! {
497 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
499 /// **Why is this bad?** Readability, this can be written more concisely as
502 /// **Known problems:** Often requires a condition + Option/Iterator creation
503 /// inside the closure.
507 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
509 /// Can be written as
511 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
515 "using a combination of `find` and `map` can usually be written as a single method call"
518 declare_clippy_lint! {
519 /// **What it does:** Checks for an iterator or string search (such as `find()`,
520 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
522 /// **Why is this bad?** Readability, this can be written more concisely as
523 /// `_.any(_)` or `_.contains(_)`.
525 /// **Known problems:** None.
529 /// # let vec = vec![1];
530 /// vec.iter().find(|x| **x == 0).is_some();
532 /// Could be written as
534 /// # let vec = vec![1];
535 /// vec.iter().any(|x| *x == 0);
539 "using an iterator or string search followed by `is_some()`, which is more succinctly expressed as a call to `any()` or `contains()`"
542 declare_clippy_lint! {
543 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
544 /// if it starts with a given char.
546 /// **Why is this bad?** Readability, this can be written more concisely as
547 /// `_.starts_with(_)`.
549 /// **Known problems:** None.
553 /// let name = "foo";
554 /// if name.chars().next() == Some('_') {};
556 /// Could be written as
558 /// let name = "foo";
559 /// if name.starts_with('_') {};
563 "using `.chars().next()` to check if a string starts with a char"
566 declare_clippy_lint! {
567 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
568 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
569 /// `unwrap_or_default` instead.
571 /// **Why is this bad?** The function will always be called and potentially
572 /// allocate an object acting as the default.
574 /// **Known problems:** If the function has side-effects, not calling it will
575 /// change the semantic of the program, but you shouldn't rely on that anyway.
579 /// # let foo = Some(String::new());
580 /// foo.unwrap_or(String::new());
582 /// this can instead be written:
584 /// # let foo = Some(String::new());
585 /// foo.unwrap_or_else(String::new);
589 /// # let foo = Some(String::new());
590 /// foo.unwrap_or_default();
594 "using any `*or` method with a function call, which suggests `*or_else`"
597 declare_clippy_lint! {
598 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
599 /// etc., and suggests to use `unwrap_or_else` instead
601 /// **Why is this bad?** The function will always be called.
603 /// **Known problems:** If the function has side-effects, not calling it will
604 /// change the semantics of the program, but you shouldn't rely on that anyway.
608 /// # let foo = Some(String::new());
609 /// # let err_code = "418";
610 /// # let err_msg = "I'm a teapot";
611 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
615 /// # let foo = Some(String::new());
616 /// # let err_code = "418";
617 /// # let err_msg = "I'm a teapot";
618 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
620 /// this can instead be written:
622 /// # let foo = Some(String::new());
623 /// # let err_code = "418";
624 /// # let err_msg = "I'm a teapot";
625 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
629 "using any `expect` method with a function call"
632 declare_clippy_lint! {
633 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
635 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
636 /// generics, not for using the `clone` method on a concrete type.
638 /// **Known problems:** None.
646 "using `clone` on a `Copy` type"
649 declare_clippy_lint! {
650 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
651 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
652 /// function syntax instead (e.g., `Rc::clone(foo)`).
654 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
655 /// can obscure the fact that only the pointer is being cloned, not the underlying
660 /// # use std::rc::Rc;
661 /// let x = Rc::new(1);
669 pub CLONE_ON_REF_PTR,
671 "using 'clone' on a ref-counted pointer"
674 declare_clippy_lint! {
675 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
677 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
678 /// cloning the underlying `T`.
680 /// **Known problems:** None.
687 /// let z = y.clone();
688 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
691 pub CLONE_DOUBLE_REF,
693 "using `clone` on `&&T`"
696 declare_clippy_lint! {
697 /// **What it does:** Checks for usage of `.to_string()` on an `&&T` where
698 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
700 /// **Why is this bad?** This bypasses the specialized implementation of
701 /// `ToString` and instead goes through the more expensive string formatting
704 /// **Known problems:** None.
708 /// // Generic implementation for `T: Display` is used (slow)
709 /// ["foo", "bar"].iter().map(|s| s.to_string());
711 /// // OK, the specialized impl is used
712 /// ["foo", "bar"].iter().map(|&s| s.to_string());
714 pub INEFFICIENT_TO_STRING,
716 "using `to_string` on `&&T` where `T: ToString`"
719 declare_clippy_lint! {
720 /// **What it does:** Checks for `new` not returning a type that contains `Self`.
722 /// **Why is this bad?** As a convention, `new` methods are used to make a new
723 /// instance of a type.
725 /// **Known problems:** None.
728 /// In an impl block:
731 /// # struct NotAFoo;
733 /// fn new() -> NotAFoo {
743 /// // Bad. The type name must contain `Self`
744 /// fn new() -> Bar {
752 /// # struct FooError;
754 /// // Good. Return type contains `Self`
755 /// fn new() -> Result<Foo, FooError> {
761 /// Or in a trait definition:
763 /// pub trait Trait {
764 /// // Bad. The type name must contain `Self`
770 /// pub trait Trait {
771 /// // Good. Return type contains `Self`
772 /// fn new() -> Self;
777 "not returning type containing `Self` in a `new` method"
780 declare_clippy_lint! {
781 /// **What it does:** Checks for string methods that receive a single-character
782 /// `str` as an argument, e.g., `_.split("x")`.
784 /// **Why is this bad?** Performing these methods using a `char` is faster than
787 /// **Known problems:** Does not catch multi-byte unicode characters.
796 pub SINGLE_CHAR_PATTERN,
798 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
801 declare_clippy_lint! {
802 /// **What it does:** Checks for calling `.step_by(0)` on iterators which panics.
804 /// **Why is this bad?** This very much looks like an oversight. Use `panic!()` instead if you
805 /// actually intend to panic.
807 /// **Known problems:** None.
810 /// ```rust,should_panic
811 /// for x in (0..100).step_by(0) {
815 pub ITERATOR_STEP_BY_ZERO,
817 "using `Iterator::step_by(0)`, which will panic at runtime"
820 declare_clippy_lint! {
821 /// **What it does:** Checks for the use of `iter.nth(0)`.
823 /// **Why is this bad?** `iter.next()` is equivalent to
824 /// `iter.nth(0)`, as they both consume the next element,
825 /// but is more readable.
827 /// **Known problems:** None.
832 /// # use std::collections::HashSet;
834 /// # let mut s = HashSet::new();
836 /// let x = s.iter().nth(0);
839 /// # let mut s = HashSet::new();
841 /// let x = s.iter().next();
845 "replace `iter.nth(0)` with `iter.next()`"
848 declare_clippy_lint! {
849 /// **What it does:** Checks for use of `.iter().nth()` (and the related
850 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
852 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
855 /// **Known problems:** None.
859 /// let some_vec = vec![0, 1, 2, 3];
860 /// let bad_vec = some_vec.iter().nth(3);
861 /// let bad_slice = &some_vec[..].iter().nth(3);
863 /// The correct use would be:
865 /// let some_vec = vec![0, 1, 2, 3];
866 /// let bad_vec = some_vec.get(3);
867 /// let bad_slice = &some_vec[..].get(3);
871 "using `.iter().nth()` on a standard library type with O(1) element access"
874 declare_clippy_lint! {
875 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
877 /// **Why is this bad?** `.nth(x)` is cleaner
879 /// **Known problems:** None.
883 /// let some_vec = vec![0, 1, 2, 3];
884 /// let bad_vec = some_vec.iter().skip(3).next();
885 /// let bad_slice = &some_vec[..].iter().skip(3).next();
887 /// The correct use would be:
889 /// let some_vec = vec![0, 1, 2, 3];
890 /// let bad_vec = some_vec.iter().nth(3);
891 /// let bad_slice = &some_vec[..].iter().nth(3);
895 "using `.skip(x).next()` on an iterator"
898 declare_clippy_lint! {
899 /// **What it does:** Checks for use of `.get().unwrap()` (or
900 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
902 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
905 /// **Known problems:** Not a replacement for error handling: Using either
906 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
907 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
908 /// temporary placeholder for dealing with the `Option` type, then this does
909 /// not mitigate the need for error handling. If there is a chance that `.get()`
910 /// will be `None` in your program, then it is advisable that the `None` case
911 /// is handled in a future refactor instead of using `.unwrap()` or the Index
916 /// let mut some_vec = vec![0, 1, 2, 3];
917 /// let last = some_vec.get(3).unwrap();
918 /// *some_vec.get_mut(0).unwrap() = 1;
920 /// The correct use would be:
922 /// let mut some_vec = vec![0, 1, 2, 3];
923 /// let last = some_vec[3];
928 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
931 declare_clippy_lint! {
932 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
933 /// `&str` or `String`.
935 /// **Why is this bad?** `.push_str(s)` is clearer
937 /// **Known problems:** None.
942 /// let def = String::from("def");
943 /// let mut s = String::new();
944 /// s.extend(abc.chars());
945 /// s.extend(def.chars());
947 /// The correct use would be:
950 /// let def = String::from("def");
951 /// let mut s = String::new();
953 /// s.push_str(&def);
955 pub STRING_EXTEND_CHARS,
957 "using `x.extend(s.chars())` where s is a `&str` or `String`"
960 declare_clippy_lint! {
961 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
964 /// **Why is this bad?** `.to_vec()` is clearer
966 /// **Known problems:** None.
970 /// let s = [1, 2, 3, 4, 5];
971 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
973 /// The better use would be:
975 /// let s = [1, 2, 3, 4, 5];
976 /// let s2: Vec<isize> = s.to_vec();
978 pub ITER_CLONED_COLLECT,
980 "using `.cloned().collect()` on slice to create a `Vec`"
983 declare_clippy_lint! {
984 /// **What it does:** Checks for usage of `_.chars().last()` or
985 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
987 /// **Why is this bad?** Readability, this can be written more concisely as
988 /// `_.ends_with(_)`.
990 /// **Known problems:** None.
994 /// # let name = "_";
997 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1000 /// name.ends_with('_') || name.ends_with('-');
1004 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1007 declare_clippy_lint! {
1008 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
1009 /// types before and after the call are the same.
1011 /// **Why is this bad?** The call is unnecessary.
1013 /// **Known problems:** None.
1017 /// # fn do_stuff(x: &[i32]) {}
1018 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1019 /// do_stuff(x.as_ref());
1021 /// The correct use would be:
1023 /// # fn do_stuff(x: &[i32]) {}
1024 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1029 "using `as_ref` where the types before and after the call are the same"
1032 declare_clippy_lint! {
1033 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
1034 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1035 /// `sum` or `product`.
1037 /// **Why is this bad?** Readability.
1039 /// **Known problems:** None.
1043 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1045 /// This could be written as:
1047 /// let _ = (0..3).any(|x| x > 2);
1049 pub UNNECESSARY_FOLD,
1051 "using `fold` when a more succinct alternative exists"
1054 declare_clippy_lint! {
1055 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1056 /// More specifically it checks if the closure provided is only performing one of the
1057 /// filter or map operations and suggests the appropriate option.
1059 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
1060 /// operation is being performed.
1062 /// **Known problems:** None
1066 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1068 /// // As there is no transformation of the argument this could be written as:
1069 /// let _ = (0..3).filter(|&x| x > 2);
1073 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1075 /// // As there is no conditional check on the argument this could be written as:
1076 /// let _ = (0..4).map(|x| x + 1);
1078 pub UNNECESSARY_FILTER_MAP,
1080 "using `filter_map` when a more succinct alternative exists"
1083 declare_clippy_lint! {
1084 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
1087 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
1088 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1089 /// `iter_mut` directly.
1091 /// **Known problems:** None
1097 /// let _ = (&vec![3, 4, 5]).into_iter();
1100 /// let _ = (&vec![3, 4, 5]).iter();
1102 pub INTO_ITER_ON_REF,
1104 "using `.into_iter()` on a reference"
1107 declare_clippy_lint! {
1108 /// **What it does:** Checks for calls to `map` followed by a `count`.
1110 /// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
1111 /// If the `map` call is intentional, this should be rewritten. Or, if you intend to
1112 /// drive the iterator to completion, you can just use `for_each` instead.
1114 /// **Known problems:** None
1119 /// let _ = (0..3).map(|x| x + 2).count();
1123 "suspicious usage of map"
1126 declare_clippy_lint! {
1127 /// **What it does:** Checks for `MaybeUninit::uninit().assume_init()`.
1129 /// **Why is this bad?** For most types, this is undefined behavior.
1131 /// **Known problems:** For now, we accept empty tuples and tuples / arrays
1132 /// of `MaybeUninit`. There may be other types that allow uninitialized
1133 /// data, but those are not yet rigorously defined.
1138 /// // Beware the UB
1139 /// use std::mem::MaybeUninit;
1141 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1144 /// Note that the following is OK:
1147 /// use std::mem::MaybeUninit;
1149 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1150 /// MaybeUninit::uninit().assume_init()
1153 pub UNINIT_ASSUMED_INIT,
1155 "`MaybeUninit::uninit().assume_init()`"
1158 declare_clippy_lint! {
1159 /// **What it does:** Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1161 /// **Why is this bad?** These can be written simply with `saturating_add/sub` methods.
1166 /// # let y: u32 = 0;
1167 /// # let x: u32 = 100;
1168 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1169 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1172 /// can be written using dedicated methods for saturating addition/subtraction as:
1175 /// # let y: u32 = 0;
1176 /// # let x: u32 = 100;
1177 /// let add = x.saturating_add(y);
1178 /// let sub = x.saturating_sub(y);
1180 pub MANUAL_SATURATING_ARITHMETIC,
1182 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1185 declare_clippy_lint! {
1186 /// **What it does:** Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1187 /// zero-sized types
1189 /// **Why is this bad?** This is a no-op, and likely unintended
1191 /// **Known problems:** None
1195 /// unsafe { (&() as *const ()).offset(1) };
1199 "Check for offset calculations on raw pointers to zero-sized types"
1202 declare_clippy_lint! {
1203 /// **What it does:** Checks for `FileType::is_file()`.
1205 /// **Why is this bad?** When people testing a file type with `FileType::is_file`
1206 /// they are testing whether a path is something they can get bytes from. But
1207 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1208 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1214 /// let metadata = std::fs::metadata("foo.txt")?;
1215 /// let filetype = metadata.file_type();
1217 /// if filetype.is_file() {
1220 /// # Ok::<_, std::io::Error>(())
1224 /// should be written as:
1228 /// let metadata = std::fs::metadata("foo.txt")?;
1229 /// let filetype = metadata.file_type();
1231 /// if !filetype.is_dir() {
1234 /// # Ok::<_, std::io::Error>(())
1237 pub FILETYPE_IS_FILE,
1239 "`FileType::is_file` is not recommended to test for readable file type"
1242 declare_clippy_lint! {
1243 /// **What it does:** Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1245 /// **Why is this bad?** Readability, this can be written more concisely as
1248 /// **Known problems:** None.
1252 /// # let opt = Some("".to_string());
1253 /// opt.as_ref().map(String::as_str)
1256 /// Can be written as
1258 /// # let opt = Some("".to_string());
1262 pub OPTION_AS_REF_DEREF,
1264 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1267 declare_clippy_lint! {
1268 /// **What it does:** Checks for usage of `iter().next()` on a Slice or an Array
1270 /// **Why is this bad?** These can be shortened into `.get()`
1272 /// **Known problems:** None.
1276 /// # let a = [1, 2, 3];
1277 /// # let b = vec![1, 2, 3];
1278 /// a[2..].iter().next();
1279 /// b.iter().next();
1281 /// should be written as:
1283 /// # let a = [1, 2, 3];
1284 /// # let b = vec![1, 2, 3];
1288 pub ITER_NEXT_SLICE,
1290 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1293 declare_clippy_lint! {
1294 /// **What it does:** Warns when using `push_str`/`insert_str` with a single-character string literal
1295 /// where `push`/`insert` with a `char` would work fine.
1297 /// **Why is this bad?** It's less clear that we are pushing a single character.
1299 /// **Known problems:** None
1303 /// let mut string = String::new();
1304 /// string.insert_str(0, "R");
1305 /// string.push_str("R");
1307 /// Could be written as
1309 /// let mut string = String::new();
1310 /// string.insert(0, 'R');
1311 /// string.push('R');
1313 pub SINGLE_CHAR_ADD_STR,
1315 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1318 declare_clippy_lint! {
1319 /// **What it does:** As the counterpart to `or_fun_call`, this lint looks for unnecessary
1320 /// lazily evaluated closures on `Option` and `Result`.
1322 /// This lint suggests changing the following functions, when eager evaluation results in
1324 /// - `unwrap_or_else` to `unwrap_or`
1325 /// - `and_then` to `and`
1326 /// - `or_else` to `or`
1327 /// - `get_or_insert_with` to `get_or_insert`
1328 /// - `ok_or_else` to `ok_or`
1330 /// **Why is this bad?** Using eager evaluation is shorter and simpler in some cases.
1332 /// **Known problems:** It is possible, but not recommended for `Deref` and `Index` to have
1333 /// side effects. Eagerly evaluating them can change the semantics of the program.
1338 /// // example code where clippy issues a warning
1339 /// let opt: Option<u32> = None;
1341 /// opt.unwrap_or_else(|| 42);
1345 /// let opt: Option<u32> = None;
1347 /// opt.unwrap_or(42);
1349 pub UNNECESSARY_LAZY_EVALUATIONS,
1351 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1354 declare_clippy_lint! {
1355 /// **What it does:** Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1357 /// **Why is this bad?** Using `try_for_each` instead is more readable and idiomatic.
1359 /// **Known problems:** None
1364 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1368 /// (0..3).try_for_each(|t| Err(t));
1370 pub MAP_COLLECT_RESULT_UNIT,
1372 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1375 declare_clippy_lint! {
1376 /// **What it does:** Checks for `from_iter()` function calls on types that implement the `FromIterator`
1379 /// **Why is this bad?** It is recommended style to use collect. See
1380 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1382 /// **Known problems:** None.
1387 /// use std::iter::FromIterator;
1389 /// let five_fives = std::iter::repeat(5).take(5);
1391 /// let v = Vec::from_iter(five_fives);
1393 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1397 /// let five_fives = std::iter::repeat(5).take(5);
1399 /// let v: Vec<i32> = five_fives.collect();
1401 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1403 pub FROM_ITER_INSTEAD_OF_COLLECT,
1405 "use `.collect()` instead of `::from_iter()`"
1408 pub struct Methods {
1409 msrv: Option<RustcVersion>,
1414 pub fn new(msrv: Option<RustcVersion>) -> Self {
1419 impl_lint_pass!(Methods => [
1422 SHOULD_IMPLEMENT_TRAIT,
1423 WRONG_SELF_CONVENTION,
1424 WRONG_PUB_SELF_CONVENTION,
1427 RESULT_MAP_OR_INTO_OPTION,
1429 BIND_INSTEAD_OF_MAP,
1437 INEFFICIENT_TO_STRING,
1439 SINGLE_CHAR_PATTERN,
1440 SINGLE_CHAR_ADD_STR,
1449 ITERATOR_STEP_BY_ZERO,
1455 STRING_EXTEND_CHARS,
1456 ITER_CLONED_COLLECT,
1459 UNNECESSARY_FILTER_MAP,
1462 UNINIT_ASSUMED_INIT,
1463 MANUAL_SATURATING_ARITHMETIC,
1466 OPTION_AS_REF_DEREF,
1467 UNNECESSARY_LAZY_EVALUATIONS,
1468 MAP_COLLECT_RESULT_UNIT,
1469 FROM_ITER_INSTEAD_OF_COLLECT,
1472 impl<'tcx> LateLintPass<'tcx> for Methods {
1473 #[allow(clippy::too_many_lines)]
1474 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
1475 if in_macro(expr.span) {
1479 let (method_names, arg_lists, method_spans) = method_calls(expr, 2);
1480 let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
1481 let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
1483 match method_names.as_slice() {
1484 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
1485 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
1486 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
1487 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
1488 ["expect", ..] => lint_expect(cx, expr, arg_lists[0]),
1489 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
1490 ["unwrap_or_else", "map"] => {
1491 if !lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0], self.msrv.as_ref()) {
1492 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or");
1495 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
1496 ["and_then", ..] => {
1497 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
1498 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
1499 if !biom_option_linted && !biom_result_linted {
1500 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "and");
1503 ["or_else", ..] => {
1504 if !bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]) {
1505 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "or");
1508 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
1509 ["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
1510 ["next", "iter"] => lint_iter_next(cx, expr, arg_lists[1]),
1511 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
1512 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
1513 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1], self.msrv.as_ref()),
1514 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
1515 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1516 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1517 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0], method_spans[0]),
1518 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
1519 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
1520 ["is_some", "position"] => {
1521 lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
1523 ["is_some", "rposition"] => {
1524 lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
1526 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
1527 ["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
1528 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
1529 ["nth", ..] => lint_iter_nth_zero(cx, expr, arg_lists[0]),
1530 ["step_by", ..] => lint_step_by(cx, expr, arg_lists[0]),
1531 ["next", "skip"] => lint_iter_skip_next(cx, expr, arg_lists[1]),
1532 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
1533 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
1534 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
1535 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0], method_spans[0]),
1536 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
1537 ["count", "map"] => lint_suspicious_map(cx, expr),
1538 ["assume_init"] => lint_maybe_uninit(cx, &arg_lists[0][0], expr),
1539 ["unwrap_or", arith @ ("checked_add" | "checked_sub" | "checked_mul")] => {
1540 manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
1542 ["add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub"] => {
1543 check_pointer_offset(cx, expr, arg_lists[0])
1545 ["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
1546 ["map", "as_ref"] => {
1547 lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false, self.msrv.as_ref())
1549 ["map", "as_mut"] => {
1550 lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true, self.msrv.as_ref())
1552 ["unwrap_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or"),
1553 ["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "get_or_insert"),
1554 ["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "ok_or"),
1555 ["collect", "map"] => lint_map_collect(cx, expr, arg_lists[1], arg_lists[0]),
1560 hir::ExprKind::Call(ref func, ref args) => {
1561 if let hir::ExprKind::Path(path) = &func.kind {
1562 if match_qpath(path, &["from_iter"]) {
1563 lint_from_iter(cx, expr, args);
1567 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args, _) => {
1568 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1569 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1571 let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0]);
1572 if args.len() == 1 && method_call.ident.name == sym::clone {
1573 lint_clone_on_copy(cx, expr, &args[0], self_ty);
1574 lint_clone_on_ref_ptr(cx, expr, &args[0]);
1576 if args.len() == 1 && method_call.ident.name == sym!(to_string) {
1577 inefficient_to_string::lint(cx, expr, &args[0], self_ty);
1580 if let Some(fn_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
1581 if match_def_path(cx, fn_def_id, &paths::PUSH_STR) {
1582 lint_single_char_push_string(cx, expr, args);
1583 } else if match_def_path(cx, fn_def_id, &paths::INSERT_STR) {
1584 lint_single_char_insert_string(cx, expr, args);
1588 match self_ty.kind() {
1589 ty::Ref(_, ty, _) if *ty.kind() == ty::Str => {
1590 for &(method, pos) in &PATTERN_METHODS {
1591 if method_call.ident.name.as_str() == method && args.len() > pos {
1592 lint_single_char_pattern(cx, expr, &args[pos]);
1596 ty::Ref(..) if method_call.ident.name == sym::into_iter => {
1597 lint_into_iter(cx, expr, self_ty, *method_span);
1602 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1603 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1605 let mut info = BinaryExprInfo {
1609 eq: op.node == hir::BinOpKind::Eq,
1611 lint_binary_expr_with_method_call(cx, &mut info);
1617 #[allow(clippy::too_many_lines)]
1618 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
1619 if in_external_macro(cx.sess(), impl_item.span) {
1622 let name = impl_item.ident.name.as_str();
1623 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1624 let item = cx.tcx.hir().expect_item(parent);
1625 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1626 let self_ty = cx.tcx.type_of(def_id);
1628 // if this impl block implements a trait, lint in trait definition instead
1629 if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = item.kind {
1634 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
1635 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1637 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1638 let method_sig = cx.tcx.fn_sig(method_def_id);
1639 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
1641 let first_arg_ty = &method_sig.inputs().iter().next();
1643 // check conventions w.r.t. conversion method names and predicates
1644 if let Some(first_arg_ty) = first_arg_ty;
1647 if cx.access_levels.is_exported(impl_item.hir_id) {
1648 // check missing trait implementations
1649 for method_config in &TRAIT_METHODS {
1650 if name == method_config.method_name &&
1651 sig.decl.inputs.len() == method_config.param_count &&
1652 method_config.output_type.matches(cx, &sig.decl.output) &&
1653 method_config.self_kind.matches(cx, self_ty, first_arg_ty) &&
1654 fn_header_equals(method_config.fn_header, sig.header) &&
1655 method_config.lifetime_param_cond(&impl_item)
1659 SHOULD_IMPLEMENT_TRAIT,
1662 "method `{}` can be confused for the standard trait method `{}::{}`",
1663 method_config.method_name,
1664 method_config.trait_name,
1665 method_config.method_name
1669 "consider implementing the trait `{}` or choosing a less ambiguous method name",
1670 method_config.trait_name
1677 lint_wrong_self_convention(
1680 item.vis.node.is_pub(),
1688 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
1689 let ret_ty = return_ty(cx, impl_item.hir_id);
1691 // walk the return type and check for Self (this does not check associated types)
1692 if contains_ty(ret_ty, self_ty) {
1696 // if return type is impl trait, check the associated types
1697 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
1698 // one of the associated types must be Self
1699 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
1700 if let ty::PredicateAtom::Projection(projection_predicate) = predicate.skip_binders() {
1701 // walk the associated type and check for Self
1702 if contains_ty(projection_predicate.ty, self_ty) {
1709 if name == "new" && !TyS::same_type(ret_ty, self_ty) {
1714 "methods called `new` usually return `Self`",
1720 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
1721 if in_external_macro(cx.tcx.sess, item.span) {
1726 if let TraitItemKind::Fn(ref sig, _) = item.kind;
1727 if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
1728 let first_arg_span = first_arg_ty.span;
1729 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
1730 let self_ty = TraitRef::identity(cx.tcx, item.hir_id.owner.to_def_id()).self_ty();
1733 lint_wrong_self_convention(cx, &item.ident.name.as_str(), false, self_ty, first_arg_ty, first_arg_span);
1738 if item.ident.name == sym::new;
1739 if let TraitItemKind::Fn(_, _) = item.kind;
1740 let ret_ty = return_ty(cx, item.hir_id);
1741 let self_ty = TraitRef::identity(cx.tcx, item.hir_id.owner.to_def_id()).self_ty();
1742 if !contains_ty(ret_ty, self_ty);
1749 "methods called `new` usually return `Self`",
1755 extract_msrv_attr!(LateContext);
1758 fn lint_wrong_self_convention<'tcx>(
1759 cx: &LateContext<'tcx>,
1762 self_ty: &'tcx TyS<'tcx>,
1763 first_arg_ty: &'tcx TyS<'tcx>,
1764 first_arg_span: Span,
1766 let lint = if is_pub {
1767 WRONG_PUB_SELF_CONVENTION
1769 WRONG_SELF_CONVENTION
1771 if let Some((ref conv, self_kinds)) = &CONVENTIONS.iter().find(|(ref conv, _)| conv.check(item_name)) {
1772 if !self_kinds.iter().any(|k| k.matches(cx, self_ty, first_arg_ty)) {
1778 "methods called `{}` usually take {}; consider choosing a less ambiguous name",
1782 .map(|k| k.description())
1783 .collect::<Vec<_>>()
1791 /// Checks for the `OR_FUN_CALL` lint.
1792 #[allow(clippy::too_many_lines)]
1793 fn lint_or_fun_call<'tcx>(
1794 cx: &LateContext<'tcx>,
1795 expr: &hir::Expr<'_>,
1798 args: &'tcx [hir::Expr<'_>],
1800 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1801 fn check_unwrap_or_default(
1802 cx: &LateContext<'_>,
1804 fun: &hir::Expr<'_>,
1805 self_expr: &hir::Expr<'_>,
1806 arg: &hir::Expr<'_>,
1812 if name == "unwrap_or";
1813 if let hir::ExprKind::Path(ref qpath) = fun.kind;
1814 let path = &*last_path_segment(qpath).ident.as_str();
1815 if ["default", "new"].contains(&path);
1816 let arg_ty = cx.typeck_results().expr_ty(arg);
1817 if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
1818 if implements_trait(cx, arg_ty, default_trait_id, &[]);
1821 let mut applicability = Applicability::MachineApplicable;
1826 &format!("use of `{}` followed by a call to `{}`", name, path),
1829 "{}.unwrap_or_default()",
1830 snippet_with_applicability(cx, self_expr.span, "..", &mut applicability)
1842 /// Checks for `*or(foo())`.
1843 #[allow(clippy::too_many_arguments)]
1844 fn check_general_case<'tcx>(
1845 cx: &LateContext<'tcx>,
1848 self_expr: &hir::Expr<'_>,
1849 arg: &'tcx hir::Expr<'_>,
1851 // None if lambda is required
1852 fun_span: Option<Span>,
1854 // (path, fn_has_argument, methods, suffix)
1855 static KNOW_TYPES: [(&[&str], bool, &[&str], &str); 4] = [
1856 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1857 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1858 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1859 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1862 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = &arg.kind {
1863 if path.ident.as_str() == "len" {
1864 let ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
1867 ty::Slice(_) | ty::Array(_, _) => return,
1871 if is_type_diagnostic_item(cx, ty, sym::vec_type) {
1878 if KNOW_TYPES.iter().any(|k| k.2.contains(&name));
1880 if is_lazyness_candidate(cx, arg);
1881 if !contains_return(&arg);
1883 let self_ty = cx.typeck_results().expr_ty(self_expr);
1885 if let Some(&(_, fn_has_arguments, poss, suffix)) =
1886 KNOW_TYPES.iter().find(|&&i| match_type(cx, self_ty, i.0));
1888 if poss.contains(&name);
1891 let sugg: Cow<'_, str> = {
1892 let (snippet_span, use_lambda) = match (fn_has_arguments, fun_span) {
1893 (false, Some(fun_span)) => (fun_span, false),
1894 _ => (arg.span, true),
1896 let snippet = snippet_with_macro_callsite(cx, snippet_span, "..");
1898 let l_arg = if fn_has_arguments { "_" } else { "" };
1899 format!("|{}| {}", l_arg, snippet).into()
1904 let span_replace_word = method_span.with_hi(span.hi());
1909 &format!("use of `{}` followed by a function call", name),
1911 format!("{}_{}({})", name, suffix, sugg),
1912 Applicability::HasPlaceholders,
1918 if args.len() == 2 {
1919 match args[1].kind {
1920 hir::ExprKind::Call(ref fun, ref or_args) => {
1921 let or_has_args = !or_args.is_empty();
1922 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1923 let fun_span = if or_has_args { None } else { Some(fun.span) };
1924 check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, fun_span);
1927 hir::ExprKind::Index(..) | hir::ExprKind::MethodCall(..) => {
1928 check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, None);
1935 /// Checks for the `EXPECT_FUN_CALL` lint.
1936 #[allow(clippy::too_many_lines)]
1937 fn lint_expect_fun_call(
1938 cx: &LateContext<'_>,
1939 expr: &hir::Expr<'_>,
1942 args: &[hir::Expr<'_>],
1944 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1946 fn get_arg_root<'a>(cx: &LateContext<'_>, arg: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
1947 let mut arg_root = arg;
1949 arg_root = match &arg_root.kind {
1950 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => expr,
1951 hir::ExprKind::MethodCall(method_name, _, call_args, _) => {
1952 if call_args.len() == 1
1953 && (method_name.ident.name == sym::as_str || method_name.ident.name == sym!(as_ref))
1955 let arg_type = cx.typeck_results().expr_ty(&call_args[0]);
1956 let base_type = arg_type.peel_refs();
1957 *base_type.kind() == ty::Str || is_type_diagnostic_item(cx, base_type, sym::string_type)
1971 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1972 // converted to string.
1973 fn requires_to_string(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1974 let arg_ty = cx.typeck_results().expr_ty(arg);
1975 if is_type_diagnostic_item(cx, arg_ty, sym::string_type) {
1978 if let ty::Ref(_, ty, ..) = arg_ty.kind() {
1979 if *ty.kind() == ty::Str && can_be_static_str(cx, arg) {
1986 // Check if an expression could have type `&'static str`, knowing that it
1987 // has type `&str` for some lifetime.
1988 fn can_be_static_str(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1990 hir::ExprKind::Lit(_) => true,
1991 hir::ExprKind::Call(fun, _) => {
1992 if let hir::ExprKind::Path(ref p) = fun.kind {
1993 match cx.qpath_res(p, fun.hir_id) {
1994 hir::def::Res::Def(hir::def::DefKind::Fn | hir::def::DefKind::AssocFn, def_id) => matches!(
1995 cx.tcx.fn_sig(def_id).output().skip_binder().kind(),
1996 ty::Ref(ty::ReStatic, ..)
2004 hir::ExprKind::MethodCall(..) => {
2006 .type_dependent_def_id(arg.hir_id)
2007 .map_or(false, |method_id| {
2009 cx.tcx.fn_sig(method_id).output().skip_binder().kind(),
2010 ty::Ref(ty::ReStatic, ..)
2014 hir::ExprKind::Path(ref p) => matches!(
2015 cx.qpath_res(p, arg.hir_id),
2016 hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static, _)
2022 fn generate_format_arg_snippet(
2023 cx: &LateContext<'_>,
2025 applicability: &mut Applicability,
2028 if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref format_arg) = a.kind;
2029 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.kind;
2030 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.kind;
2035 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
2043 fn is_call(node: &hir::ExprKind<'_>) -> bool {
2045 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => {
2048 hir::ExprKind::Call(..)
2049 | hir::ExprKind::MethodCall(..)
2050 // These variants are debatable or require further examination
2051 | hir::ExprKind::If(..)
2052 | hir::ExprKind::Match(..)
2053 | hir::ExprKind::Block{ .. } => true,
2058 if args.len() != 2 || name != "expect" || !is_call(&args[1].kind) {
2062 let receiver_type = cx.typeck_results().expr_ty_adjusted(&args[0]);
2063 let closure_args = if is_type_diagnostic_item(cx, receiver_type, sym::option_type) {
2065 } else if is_type_diagnostic_item(cx, receiver_type, sym::result_type) {
2071 let arg_root = get_arg_root(cx, &args[1]);
2073 let span_replace_word = method_span.with_hi(expr.span.hi());
2075 let mut applicability = Applicability::MachineApplicable;
2077 //Special handling for `format!` as arg_root
2079 if let hir::ExprKind::Block(block, None) = &arg_root.kind;
2080 if block.stmts.len() == 1;
2081 if let hir::StmtKind::Local(local) = &block.stmts[0].kind;
2082 if let Some(arg_root) = &local.init;
2083 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.kind;
2084 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1;
2085 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].kind;
2087 let fmt_spec = &format_args[0];
2088 let fmt_args = &format_args[1];
2090 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
2092 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
2094 let sugg = args.join(", ");
2100 &format!("use of `{}` followed by a function call", name),
2102 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
2110 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
2111 if requires_to_string(cx, arg_root) {
2112 arg_root_snippet.to_mut().push_str(".to_string()");
2119 &format!("use of `{}` followed by a function call", name),
2121 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
2126 /// Checks for the `CLONE_ON_COPY` lint.
2127 fn lint_clone_on_copy(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
2128 let ty = cx.typeck_results().expr_ty(expr);
2129 if let ty::Ref(_, inner, _) = arg_ty.kind() {
2130 if let ty::Ref(_, innermost, _) = inner.kind() {
2136 "using `clone` on a double-reference; \
2137 this will copy the reference of type `{}` instead of cloning the inner type",
2141 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
2142 let mut ty = innermost;
2144 while let ty::Ref(_, inner, _) = ty.kind() {
2148 let refs: String = iter::repeat('&').take(n + 1).collect();
2149 let derefs: String = iter::repeat('*').take(n).collect();
2150 let explicit = format!("<{}{}>::clone({})", refs, ty, snip);
2151 diag.span_suggestion(
2153 "try dereferencing it",
2154 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
2155 Applicability::MaybeIncorrect,
2157 diag.span_suggestion(
2159 "or try being explicit if you are sure, that you want to clone a reference",
2161 Applicability::MaybeIncorrect,
2166 return; // don't report clone_on_copy
2170 if is_copy(cx, ty) {
2172 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
2173 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
2174 match &cx.tcx.hir().get(parent) {
2175 hir::Node::Expr(parent) => match parent.kind {
2176 // &*x is a nop, &x.clone() is not
2177 hir::ExprKind::AddrOf(..) => return,
2178 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
2179 hir::ExprKind::MethodCall(_, _, parent_args, _) if expr.hir_id == parent_args[0].hir_id => {
2185 hir::Node::Stmt(stmt) => {
2186 if let hir::StmtKind::Local(ref loc) = stmt.kind {
2187 if let hir::PatKind::Ref(..) = loc.pat.kind {
2188 // let ref y = *x borrows x, let ref y = x.clone() does not
2196 // x.clone() might have dereferenced x, possibly through Deref impls
2197 if cx.typeck_results().expr_ty(arg) == ty {
2198 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
2200 let deref_count = cx
2202 .expr_adjustments(arg)
2204 .filter(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(_)))
2206 let derefs: String = iter::repeat('*').take(deref_count).collect();
2207 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
2216 &format!("using `clone` on type `{}` which implements the `Copy` trait", ty),
2218 if let Some((text, snip)) = snip {
2219 diag.span_suggestion(expr.span, text, snip, Applicability::MachineApplicable);
2226 fn lint_clone_on_ref_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
2227 let obj_ty = cx.typeck_results().expr_ty(arg).peel_refs();
2229 if let ty::Adt(_, subst) = obj_ty.kind() {
2230 let caller_type = if is_type_diagnostic_item(cx, obj_ty, sym::Rc) {
2232 } else if is_type_diagnostic_item(cx, obj_ty, sym::Arc) {
2234 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
2240 let snippet = snippet_with_macro_callsite(cx, arg.span, "..");
2246 "using `.clone()` on a ref-counted pointer",
2248 format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet),
2249 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
2254 fn lint_string_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2256 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
2257 let target = &arglists[0][0];
2258 let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
2259 let ref_str = if *self_ty.kind() == ty::Str {
2261 } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
2267 let mut applicability = Applicability::MachineApplicable;
2270 STRING_EXTEND_CHARS,
2272 "calling `.extend(_.chars())`",
2275 "{}.push_str({}{})",
2276 snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
2278 snippet_with_applicability(cx, target.span, "..", &mut applicability)
2285 fn lint_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2286 let obj_ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
2287 if is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
2288 lint_string_extend(cx, expr, args);
2292 fn lint_iter_cloned_collect<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2294 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::vec_type);
2295 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0]));
2296 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite());
2301 ITER_CLONED_COLLECT,
2303 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
2306 ".to_vec()".to_string(),
2307 Applicability::MachineApplicable,
2313 fn lint_unnecessary_fold(cx: &LateContext<'_>, expr: &hir::Expr<'_>, fold_args: &[hir::Expr<'_>], fold_span: Span) {
2314 fn check_fold_with_op(
2315 cx: &LateContext<'_>,
2316 expr: &hir::Expr<'_>,
2317 fold_args: &[hir::Expr<'_>],
2320 replacement_method_name: &str,
2321 replacement_has_args: bool,
2324 // Extract the body of the closure passed to fold
2325 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].kind;
2326 let closure_body = cx.tcx.hir().body(body_id);
2327 let closure_expr = remove_blocks(&closure_body.value);
2329 // Check if the closure body is of the form `acc <op> some_expr(x)`
2330 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.kind;
2331 if bin_op.node == op;
2333 // Extract the names of the two arguments to the closure
2334 if let Some(first_arg_ident) = get_arg_name(&closure_body.params[0].pat);
2335 if let Some(second_arg_ident) = get_arg_name(&closure_body.params[1].pat);
2337 if match_var(&*left_expr, first_arg_ident);
2338 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
2341 let mut applicability = Applicability::MachineApplicable;
2342 let sugg = if replacement_has_args {
2344 "{replacement}(|{s}| {r})",
2345 replacement = replacement_method_name,
2346 s = second_arg_ident,
2347 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
2352 replacement = replacement_method_name,
2359 fold_span.with_hi(expr.span.hi()),
2360 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
2361 "this `.fold` can be written more succinctly using another method",
2370 // Check that this is a call to Iterator::fold rather than just some function called fold
2371 if !match_trait_method(cx, expr, &paths::ITERATOR) {
2376 fold_args.len() == 3,
2377 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
2380 // Check if the first argument to .fold is a suitable literal
2381 if let hir::ExprKind::Lit(ref lit) = fold_args[1].kind {
2383 ast::LitKind::Bool(false) => {
2384 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Or, "any", true)
2386 ast::LitKind::Bool(true) => {
2387 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::And, "all", true)
2389 ast::LitKind::Int(0, _) => {
2390 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Add, "sum", false)
2392 ast::LitKind::Int(1, _) => {
2393 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Mul, "product", false)
2400 fn lint_step_by<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, args: &'tcx [hir::Expr<'_>]) {
2401 if match_trait_method(cx, expr, &paths::ITERATOR) {
2402 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &args[1]) {
2405 ITERATOR_STEP_BY_ZERO,
2407 "Iterator::step_by(0) will panic at runtime",
2413 fn lint_iter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2414 let caller_expr = &iter_args[0];
2416 // Skip lint if the `iter().next()` expression is a for loop argument,
2417 // since it is already covered by `&loops::ITER_NEXT_LOOP`
2418 let mut parent_expr_opt = get_parent_expr(cx, expr);
2419 while let Some(parent_expr) = parent_expr_opt {
2420 if higher::for_loop(parent_expr).is_some() {
2423 parent_expr_opt = get_parent_expr(cx, parent_expr);
2426 if derefs_to_slice(cx, caller_expr, cx.typeck_results().expr_ty(caller_expr)).is_some() {
2427 // caller is a Slice
2429 if let hir::ExprKind::Index(ref caller_var, ref index_expr) = &caller_expr.kind;
2430 if let Some(higher::Range { start: Some(start_expr), end: None, limits: ast::RangeLimits::HalfOpen })
2431 = higher::range(index_expr);
2432 if let hir::ExprKind::Lit(ref start_lit) = &start_expr.kind;
2433 if let ast::LitKind::Int(start_idx, _) = start_lit.node;
2435 let mut applicability = Applicability::MachineApplicable;
2440 "using `.iter().next()` on a Slice without end index",
2442 format!("{}.get({})", snippet_with_applicability(cx, caller_var.span, "..", &mut applicability), start_idx),
2447 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(caller_expr), sym::vec_type)
2449 &cx.typeck_results().expr_ty(caller_expr).peel_refs().kind(),
2453 // caller is a Vec or an Array
2454 let mut applicability = Applicability::MachineApplicable;
2459 "using `.iter().next()` on an array",
2463 snippet_with_applicability(cx, caller_expr.span, "..", &mut applicability)
2470 fn lint_iter_nth<'tcx>(
2471 cx: &LateContext<'tcx>,
2472 expr: &hir::Expr<'_>,
2473 nth_and_iter_args: &[&'tcx [hir::Expr<'tcx>]],
2476 let iter_args = nth_and_iter_args[1];
2477 let mut_str = if is_mut { "_mut" } else { "" };
2478 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0])).is_some() {
2480 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym::vec_type) {
2482 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym!(vecdeque_type)) {
2485 let nth_args = nth_and_iter_args[0];
2486 lint_iter_nth_zero(cx, expr, &nth_args);
2487 return; // caller is not a type that we want to lint
2494 &format!("called `.iter{0}().nth()` on a {1}", mut_str, caller_type),
2496 &format!("calling `.get{}()` is both faster and more readable", mut_str),
2500 fn lint_iter_nth_zero<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
2502 if match_trait_method(cx, expr, &paths::ITERATOR);
2503 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &nth_args[1]);
2505 let mut applicability = Applicability::MachineApplicable;
2510 "called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
2511 "try calling `.next()` instead of `.nth(0)`",
2512 format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
2519 fn lint_get_unwrap<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, get_args: &'tcx [hir::Expr<'_>], is_mut: bool) {
2520 // Note: we don't want to lint `get_mut().unwrap` for `HashMap` or `BTreeMap`,
2521 // because they do not implement `IndexMut`
2522 let mut applicability = Applicability::MachineApplicable;
2523 let expr_ty = cx.typeck_results().expr_ty(&get_args[0]);
2524 let get_args_str = if get_args.len() > 1 {
2525 snippet_with_applicability(cx, get_args[1].span, "..", &mut applicability)
2527 return; // not linting on a .get().unwrap() chain or variant
2530 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
2531 needs_ref = get_args_str.parse::<usize>().is_ok();
2533 } else if is_type_diagnostic_item(cx, expr_ty, sym::vec_type) {
2534 needs_ref = get_args_str.parse::<usize>().is_ok();
2536 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vecdeque_type)) {
2537 needs_ref = get_args_str.parse::<usize>().is_ok();
2539 } else if !is_mut && is_type_diagnostic_item(cx, expr_ty, sym!(hashmap_type)) {
2542 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
2546 return; // caller is not a type that we want to lint
2549 let mut span = expr.span;
2551 // Handle the case where the result is immediately dereferenced
2552 // by not requiring ref and pulling the dereference into the
2556 if let Some(parent) = get_parent_expr(cx, expr);
2557 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.kind;
2564 let mut_str = if is_mut { "_mut" } else { "" };
2565 let borrow_str = if !needs_ref {
2578 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
2579 mut_str, caller_type
2585 snippet_with_applicability(cx, get_args[0].span, "..", &mut applicability),
2592 fn lint_iter_skip_next(cx: &LateContext<'_>, expr: &hir::Expr<'_>, skip_args: &[hir::Expr<'_>]) {
2593 // lint if caller of skip is an Iterator
2594 if match_trait_method(cx, expr, &paths::ITERATOR) {
2595 if let [caller, n] = skip_args {
2596 let hint = format!(".nth({})", snippet(cx, n.span, ".."));
2600 expr.span.trim_start(caller.span).unwrap(),
2601 "called `skip(..).next()` on an iterator",
2602 "use `nth` instead",
2604 Applicability::MachineApplicable,
2610 fn derefs_to_slice<'tcx>(
2611 cx: &LateContext<'tcx>,
2612 expr: &'tcx hir::Expr<'tcx>,
2614 ) -> Option<&'tcx hir::Expr<'tcx>> {
2615 fn may_slice<'a>(cx: &LateContext<'a>, ty: Ty<'a>) -> bool {
2617 ty::Slice(_) => true,
2618 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
2619 ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym::vec_type),
2620 ty::Array(_, size) => size
2621 .try_eval_usize(cx.tcx, cx.param_env)
2622 .map_or(false, |size| size < 32),
2623 ty::Ref(_, inner, _) => may_slice(cx, inner),
2628 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind {
2629 if path.ident.name == sym::iter && may_slice(cx, cx.typeck_results().expr_ty(&args[0])) {
2636 ty::Slice(_) => Some(expr),
2637 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
2638 ty::Ref(_, inner, _) => {
2639 if may_slice(cx, inner) {
2650 /// lint use of `unwrap()` for `Option`s and `Result`s
2651 fn lint_unwrap(cx: &LateContext<'_>, expr: &hir::Expr<'_>, unwrap_args: &[hir::Expr<'_>]) {
2652 let obj_ty = cx.typeck_results().expr_ty(&unwrap_args[0]).peel_refs();
2654 let mess = if is_type_diagnostic_item(cx, obj_ty, sym::option_type) {
2655 Some((UNWRAP_USED, "an Option", "None"))
2656 } else if is_type_diagnostic_item(cx, obj_ty, sym::result_type) {
2657 Some((UNWRAP_USED, "a Result", "Err"))
2662 if let Some((lint, kind, none_value)) = mess {
2667 &format!("used `unwrap()` on `{}` value", kind,),
2670 "if you don't want to handle the `{}` case gracefully, consider \
2671 using `expect()` to provide a better panic message",
2678 /// lint use of `expect()` for `Option`s and `Result`s
2679 fn lint_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, expect_args: &[hir::Expr<'_>]) {
2680 let obj_ty = cx.typeck_results().expr_ty(&expect_args[0]).peel_refs();
2682 let mess = if is_type_diagnostic_item(cx, obj_ty, sym::option_type) {
2683 Some((EXPECT_USED, "an Option", "None"))
2684 } else if is_type_diagnostic_item(cx, obj_ty, sym::result_type) {
2685 Some((EXPECT_USED, "a Result", "Err"))
2690 if let Some((lint, kind, none_value)) = mess {
2695 &format!("used `expect()` on `{}` value", kind,),
2697 &format!("if this value is an `{}`, it will panic", none_value,),
2702 /// lint use of `ok().expect()` for `Result`s
2703 fn lint_ok_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
2705 // lint if the caller of `ok()` is a `Result`
2706 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&ok_args[0]), sym::result_type);
2707 let result_type = cx.typeck_results().expr_ty(&ok_args[0]);
2708 if let Some(error_type) = get_error_type(cx, result_type);
2709 if has_debug_impl(error_type, cx);
2716 "called `ok().expect()` on a `Result` value",
2718 "you can call `expect()` directly on the `Result`",
2724 /// lint use of `map().flatten()` for `Iterators` and 'Options'
2725 fn lint_map_flatten<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) {
2726 // lint if caller of `.map().flatten()` is an Iterator
2727 if match_trait_method(cx, expr, &paths::ITERATOR) {
2728 let map_closure_ty = cx.typeck_results().expr_ty(&map_args[1]);
2729 let is_map_to_option = match map_closure_ty.kind() {
2730 ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
2731 let map_closure_sig = match map_closure_ty.kind() {
2732 ty::Closure(_, substs) => substs.as_closure().sig(),
2733 _ => map_closure_ty.fn_sig(cx.tcx),
2735 let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
2736 is_type_diagnostic_item(cx, map_closure_return_ty, sym::option_type)
2741 let method_to_use = if is_map_to_option {
2742 // `(...).map(...)` has type `impl Iterator<Item=Option<...>>
2745 // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
2748 let func_snippet = snippet(cx, map_args[1].span, "..");
2749 let hint = format!(".{0}({1})", method_to_use, func_snippet);
2753 expr.span.with_lo(map_args[0].span.hi()),
2754 "called `map(..).flatten()` on an `Iterator`",
2755 &format!("try using `{}` instead", method_to_use),
2757 Applicability::MachineApplicable,
2761 // lint if caller of `.map().flatten()` is an Option
2762 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::option_type) {
2763 let func_snippet = snippet(cx, map_args[1].span, "..");
2764 let hint = format!(".and_then({})", func_snippet);
2768 expr.span.with_lo(map_args[0].span.hi()),
2769 "called `map(..).flatten()` on an `Option`",
2770 "try using `and_then` instead",
2772 Applicability::MachineApplicable,
2777 const MAP_UNWRAP_OR_MSRV: RustcVersion = RustcVersion::new(1, 41, 0);
2779 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
2780 /// Return true if lint triggered
2781 fn lint_map_unwrap_or_else<'tcx>(
2782 cx: &LateContext<'tcx>,
2783 expr: &'tcx hir::Expr<'_>,
2784 map_args: &'tcx [hir::Expr<'_>],
2785 unwrap_args: &'tcx [hir::Expr<'_>],
2786 msrv: Option<&RustcVersion>,
2788 if !meets_msrv(msrv, &MAP_UNWRAP_OR_MSRV) {
2791 // lint if the caller of `map()` is an `Option`
2792 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::option_type);
2793 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::result_type);
2795 if is_option || is_result {
2796 // Don't make a suggestion that may fail to compile due to mutably borrowing
2797 // the same variable twice.
2798 let map_mutated_vars = mutated_variables(&map_args[0], cx);
2799 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
2800 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
2801 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
2809 let msg = if is_option {
2810 "called `map(<f>).unwrap_or_else(<g>)` on an `Option` value. This can be done more directly by calling \
2811 `map_or_else(<g>, <f>)` instead"
2813 "called `map(<f>).unwrap_or_else(<g>)` on a `Result` value. This can be done more directly by calling \
2814 `.map_or_else(<g>, <f>)` instead"
2816 // get snippets for args to map() and unwrap_or_else()
2817 let map_snippet = snippet(cx, map_args[1].span, "..");
2818 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
2819 // lint, with note if neither arg is > 1 line and both map() and
2820 // unwrap_or_else() have the same span
2821 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
2822 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
2823 if same_span && !multiline {
2824 let var_snippet = snippet(cx, map_args[0].span, "..");
2831 format!("{}.map_or_else({}, {})", var_snippet, unwrap_snippet, map_snippet),
2832 Applicability::MachineApplicable,
2835 } else if same_span && multiline {
2836 span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
2844 /// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
2845 fn lint_map_or_none<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_or_args: &'tcx [hir::Expr<'_>]) {
2846 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::option_type);
2847 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::result_type);
2849 // There are two variants of this `map_or` lint:
2850 // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
2851 // (2) using `map_or` as a combinator instead of `and_then`
2853 // (For this lint) we don't care if any other type calls `map_or`
2854 if !is_option && !is_result {
2858 let (lint_name, msg, instead, hint) = {
2859 let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
2860 match_qpath(qpath, &paths::OPTION_NONE)
2865 if !default_arg_is_none {
2870 let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
2871 match_qpath(qpath, &paths::OPTION_SOME)
2877 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2878 let func_snippet = snippet(cx, map_or_args[2].span, "..");
2879 let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
2880 `and_then(..)` instead";
2884 "try using `and_then` instead",
2885 format!("{0}.and_then({1})", self_snippet, func_snippet),
2887 } else if f_arg_is_some {
2888 let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
2890 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2892 RESULT_MAP_OR_INTO_OPTION,
2894 "try using `ok` instead",
2895 format!("{0}.ok()", self_snippet),
2910 Applicability::MachineApplicable,
2914 /// lint use of `filter().next()` for `Iterators`
2915 fn lint_filter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
2916 // lint if caller of `.filter().next()` is an Iterator
2917 if match_trait_method(cx, expr, &paths::ITERATOR) {
2918 let msg = "called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
2919 `.find(..)` instead.";
2920 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2921 if filter_snippet.lines().count() <= 1 {
2922 let iter_snippet = snippet(cx, filter_args[0].span, "..");
2923 // add note if not multi-line
2930 format!("{}.find({})", iter_snippet, filter_snippet),
2931 Applicability::MachineApplicable,
2934 span_lint(cx, FILTER_NEXT, expr.span, msg);
2939 /// lint use of `skip_while().next()` for `Iterators`
2940 fn lint_skip_while_next<'tcx>(
2941 cx: &LateContext<'tcx>,
2942 expr: &'tcx hir::Expr<'_>,
2943 _skip_while_args: &'tcx [hir::Expr<'_>],
2945 // lint if caller of `.skip_while().next()` is an Iterator
2946 if match_trait_method(cx, expr, &paths::ITERATOR) {
2951 "called `skip_while(<p>).next()` on an `Iterator`",
2953 "this is more succinctly expressed by calling `.find(!<p>)` instead",
2958 /// lint use of `filter().map()` for `Iterators`
2959 fn lint_filter_map<'tcx>(
2960 cx: &LateContext<'tcx>,
2961 expr: &'tcx hir::Expr<'_>,
2962 _filter_args: &'tcx [hir::Expr<'_>],
2963 _map_args: &'tcx [hir::Expr<'_>],
2965 // lint if caller of `.filter().map()` is an Iterator
2966 if match_trait_method(cx, expr, &paths::ITERATOR) {
2967 let msg = "called `filter(..).map(..)` on an `Iterator`";
2968 let hint = "this is more succinctly expressed by calling `.filter_map(..)` instead";
2969 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2973 const FILTER_MAP_NEXT_MSRV: RustcVersion = RustcVersion::new(1, 30, 0);
2975 /// lint use of `filter_map().next()` for `Iterators`
2976 fn lint_filter_map_next<'tcx>(
2977 cx: &LateContext<'tcx>,
2978 expr: &'tcx hir::Expr<'_>,
2979 filter_args: &'tcx [hir::Expr<'_>],
2980 msrv: Option<&RustcVersion>,
2982 if match_trait_method(cx, expr, &paths::ITERATOR) {
2983 if !meets_msrv(msrv, &FILTER_MAP_NEXT_MSRV) {
2987 let msg = "called `filter_map(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
2988 `.find_map(..)` instead.";
2989 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2990 if filter_snippet.lines().count() <= 1 {
2991 let iter_snippet = snippet(cx, filter_args[0].span, "..");
2998 format!("{}.find_map({})", iter_snippet, filter_snippet),
2999 Applicability::MachineApplicable,
3002 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
3007 /// lint use of `find().map()` for `Iterators`
3008 fn lint_find_map<'tcx>(
3009 cx: &LateContext<'tcx>,
3010 expr: &'tcx hir::Expr<'_>,
3011 _find_args: &'tcx [hir::Expr<'_>],
3012 map_args: &'tcx [hir::Expr<'_>],
3014 // lint if caller of `.filter().map()` is an Iterator
3015 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
3016 let msg = "called `find(..).map(..)` on an `Iterator`";
3017 let hint = "this is more succinctly expressed by calling `.find_map(..)` instead";
3018 span_lint_and_help(cx, FIND_MAP, expr.span, msg, None, hint);
3022 /// lint use of `filter_map().map()` for `Iterators`
3023 fn lint_filter_map_map<'tcx>(
3024 cx: &LateContext<'tcx>,
3025 expr: &'tcx hir::Expr<'_>,
3026 _filter_args: &'tcx [hir::Expr<'_>],
3027 _map_args: &'tcx [hir::Expr<'_>],
3029 // lint if caller of `.filter().map()` is an Iterator
3030 if match_trait_method(cx, expr, &paths::ITERATOR) {
3031 let msg = "called `filter_map(..).map(..)` on an `Iterator`";
3032 let hint = "this is more succinctly expressed by only calling `.filter_map(..)` instead";
3033 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3037 /// lint use of `filter().flat_map()` for `Iterators`
3038 fn lint_filter_flat_map<'tcx>(
3039 cx: &LateContext<'tcx>,
3040 expr: &'tcx hir::Expr<'_>,
3041 _filter_args: &'tcx [hir::Expr<'_>],
3042 _map_args: &'tcx [hir::Expr<'_>],
3044 // lint if caller of `.filter().flat_map()` is an Iterator
3045 if match_trait_method(cx, expr, &paths::ITERATOR) {
3046 let msg = "called `filter(..).flat_map(..)` on an `Iterator`";
3047 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
3048 and filtering by returning `iter::empty()`";
3049 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3053 /// lint use of `filter_map().flat_map()` for `Iterators`
3054 fn lint_filter_map_flat_map<'tcx>(
3055 cx: &LateContext<'tcx>,
3056 expr: &'tcx hir::Expr<'_>,
3057 _filter_args: &'tcx [hir::Expr<'_>],
3058 _map_args: &'tcx [hir::Expr<'_>],
3060 // lint if caller of `.filter_map().flat_map()` is an Iterator
3061 if match_trait_method(cx, expr, &paths::ITERATOR) {
3062 let msg = "called `filter_map(..).flat_map(..)` on an `Iterator`";
3063 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
3064 and filtering by returning `iter::empty()`";
3065 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3069 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
3070 fn lint_flat_map_identity<'tcx>(
3071 cx: &LateContext<'tcx>,
3072 expr: &'tcx hir::Expr<'_>,
3073 flat_map_args: &'tcx [hir::Expr<'_>],
3074 flat_map_span: Span,
3076 if match_trait_method(cx, expr, &paths::ITERATOR) {
3077 let arg_node = &flat_map_args[1].kind;
3079 let apply_lint = |message: &str| {
3083 flat_map_span.with_hi(expr.span.hi()),
3086 "flatten()".to_string(),
3087 Applicability::MachineApplicable,
3092 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
3093 let body = cx.tcx.hir().body(*body_id);
3095 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
3096 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
3098 if path.segments.len() == 1;
3099 if path.segments[0].ident.as_str() == binding_ident.as_str();
3102 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
3107 if let hir::ExprKind::Path(ref qpath) = arg_node;
3109 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
3112 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
3118 /// lint searching an Iterator followed by `is_some()`
3119 /// or calling `find()` on a string followed by `is_some()`
3120 fn lint_search_is_some<'tcx>(
3121 cx: &LateContext<'tcx>,
3122 expr: &'tcx hir::Expr<'_>,
3123 search_method: &str,
3124 search_args: &'tcx [hir::Expr<'_>],
3125 is_some_args: &'tcx [hir::Expr<'_>],
3128 // lint if caller of search is an Iterator
3129 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
3131 "called `is_some()` after searching an `Iterator` with `{}`",
3134 let hint = "this is more succinctly expressed by calling `any()`";
3135 let search_snippet = snippet(cx, search_args[1].span, "..");
3136 if search_snippet.lines().count() <= 1 {
3137 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
3138 // suggest `any(|..| *..)` instead of `any(|..| **..)` for `find(|..| **..).is_some()`
3139 let any_search_snippet = if_chain! {
3140 if search_method == "find";
3141 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].kind;
3142 let closure_body = cx.tcx.hir().body(body_id);
3143 if let Some(closure_arg) = closure_body.params.get(0);
3145 if let hir::PatKind::Ref(..) = closure_arg.pat.kind {
3146 Some(search_snippet.replacen('&', "", 1))
3147 } else if let Some(name) = get_arg_name(&closure_arg.pat) {
3148 Some(search_snippet.replace(&format!("*{}", name), &name.as_str()))
3156 // add note if not multi-line
3160 method_span.with_hi(expr.span.hi()),
3162 "use `any()` instead",
3165 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
3167 Applicability::MachineApplicable,
3170 span_lint_and_help(cx, SEARCH_IS_SOME, expr.span, &msg, None, hint);
3173 // lint if `find()` is called by `String` or `&str`
3174 else if search_method == "find" {
3175 let is_string_or_str_slice = |e| {
3176 let self_ty = cx.typeck_results().expr_ty(e).peel_refs();
3177 if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
3180 *self_ty.kind() == ty::Str
3184 if is_string_or_str_slice(&search_args[0]);
3185 if is_string_or_str_slice(&search_args[1]);
3187 let msg = "called `is_some()` after calling `find()` on a string";
3188 let mut applicability = Applicability::MachineApplicable;
3189 let find_arg = snippet_with_applicability(cx, search_args[1].span, "..", &mut applicability);
3193 method_span.with_hi(expr.span.hi()),
3195 "use `contains()` instead",
3196 format!("contains({})", find_arg),
3204 /// Used for `lint_binary_expr_with_method_call`.
3205 #[derive(Copy, Clone)]
3206 struct BinaryExprInfo<'a> {
3207 expr: &'a hir::Expr<'a>,
3208 chain: &'a hir::Expr<'a>,
3209 other: &'a hir::Expr<'a>,
3213 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3214 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
3215 macro_rules! lint_with_both_lhs_and_rhs {
3216 ($func:ident, $cx:expr, $info:ident) => {
3217 if !$func($cx, $info) {
3218 ::std::mem::swap(&mut $info.chain, &mut $info.other);
3219 if $func($cx, $info) {
3226 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
3227 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
3228 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
3229 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
3232 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3234 cx: &LateContext<'_>,
3235 info: &BinaryExprInfo<'_>,
3236 chain_methods: &[&str],
3237 lint: &'static Lint,
3241 if let Some(args) = method_chain_args(info.chain, chain_methods);
3242 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
3243 if arg_char.len() == 1;
3244 if let hir::ExprKind::Path(ref qpath) = fun.kind;
3245 if let Some(segment) = single_segment_path(qpath);
3246 if segment.ident.name == sym::Some;
3248 let mut applicability = Applicability::MachineApplicable;
3249 let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0][0]).peel_refs();
3251 if *self_ty.kind() != ty::Str {
3259 &format!("you should use the `{}` method", suggest),
3261 format!("{}{}.{}({})",
3262 if info.eq { "" } else { "!" },
3263 snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
3265 snippet_with_applicability(cx, arg_char[0].span, "..", &mut applicability)),
3276 /// Checks for the `CHARS_NEXT_CMP` lint.
3277 fn lint_chars_next_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3278 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
3281 /// Checks for the `CHARS_LAST_CMP` lint.
3282 fn lint_chars_last_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3283 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
3286 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
3290 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
3291 fn lint_chars_cmp_with_unwrap<'tcx>(
3292 cx: &LateContext<'tcx>,
3293 info: &BinaryExprInfo<'_>,
3294 chain_methods: &[&str],
3295 lint: &'static Lint,
3299 if let Some(args) = method_chain_args(info.chain, chain_methods);
3300 if let hir::ExprKind::Lit(ref lit) = info.other.kind;
3301 if let ast::LitKind::Char(c) = lit.node;
3303 let mut applicability = Applicability::MachineApplicable;
3308 &format!("you should use the `{}` method", suggest),
3310 format!("{}{}.{}('{}')",
3311 if info.eq { "" } else { "!" },
3312 snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
3325 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
3326 fn lint_chars_next_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3327 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
3330 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
3331 fn lint_chars_last_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3332 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
3335 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
3339 fn get_hint_if_single_char_arg(
3340 cx: &LateContext<'_>,
3341 arg: &hir::Expr<'_>,
3342 applicability: &mut Applicability,
3343 ) -> Option<String> {
3345 if let hir::ExprKind::Lit(lit) = &arg.kind;
3346 if let ast::LitKind::Str(r, style) = lit.node;
3347 let string = r.as_str();
3348 if string.chars().count() == 1;
3350 let snip = snippet_with_applicability(cx, arg.span, &string, applicability);
3351 let ch = if let ast::StrStyle::Raw(nhash) = style {
3352 let nhash = nhash as usize;
3353 // for raw string: r##"a"##
3354 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
3356 // for regular string: "a"
3357 &snip[1..(snip.len() - 1)]
3359 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
3367 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
3368 fn lint_single_char_pattern(cx: &LateContext<'_>, _expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
3369 let mut applicability = Applicability::MachineApplicable;
3370 if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability) {
3373 SINGLE_CHAR_PATTERN,
3375 "single-character string constant used as pattern",
3376 "try using a `char` instead",
3383 /// lint for length-1 `str`s as argument for `push_str`
3384 fn lint_single_char_push_string(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3385 let mut applicability = Applicability::MachineApplicable;
3386 if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[1], &mut applicability) {
3387 let base_string_snippet =
3388 snippet_with_applicability(cx, args[0].span.source_callsite(), "..", &mut applicability);
3389 let sugg = format!("{}.push({})", base_string_snippet, extension_string);
3392 SINGLE_CHAR_ADD_STR,
3394 "calling `push_str()` using a single-character string literal",
3395 "consider using `push` with a character literal",
3402 /// lint for length-1 `str`s as argument for `insert_str`
3403 fn lint_single_char_insert_string(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3404 let mut applicability = Applicability::MachineApplicable;
3405 if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[2], &mut applicability) {
3406 let base_string_snippet =
3407 snippet_with_applicability(cx, args[0].span.source_callsite(), "_", &mut applicability);
3408 let pos_arg = snippet_with_applicability(cx, args[1].span, "..", &mut applicability);
3409 let sugg = format!("{}.insert({}, {})", base_string_snippet, pos_arg, extension_string);
3412 SINGLE_CHAR_ADD_STR,
3414 "calling `insert_str()` using a single-character string literal",
3415 "consider using `insert` with a character literal",
3422 /// Checks for the `USELESS_ASREF` lint.
3423 fn lint_asref(cx: &LateContext<'_>, expr: &hir::Expr<'_>, call_name: &str, as_ref_args: &[hir::Expr<'_>]) {
3424 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
3425 // check if the call is to the actual `AsRef` or `AsMut` trait
3426 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
3427 // check if the type after `as_ref` or `as_mut` is the same as before
3428 let recvr = &as_ref_args[0];
3429 let rcv_ty = cx.typeck_results().expr_ty(recvr);
3430 let res_ty = cx.typeck_results().expr_ty(expr);
3431 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
3432 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
3433 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
3434 // allow the `as_ref` or `as_mut` if it is followed by another method call
3436 if let Some(parent) = get_parent_expr(cx, expr);
3437 if let hir::ExprKind::MethodCall(_, ref span, _, _) = parent.kind;
3438 if span != &expr.span;
3444 let mut applicability = Applicability::MachineApplicable;
3449 &format!("this call to `{}` does nothing", call_name),
3451 snippet_with_applicability(cx, recvr.span, "..", &mut applicability).to_string(),
3458 fn ty_has_iter_method(cx: &LateContext<'_>, self_ref_ty: Ty<'_>) -> Option<(&'static str, &'static str)> {
3459 has_iter_method(cx, self_ref_ty).map(|ty_name| {
3460 let mutbl = match self_ref_ty.kind() {
3461 ty::Ref(_, _, mutbl) => mutbl,
3462 _ => unreachable!(),
3464 let method_name = match mutbl {
3465 hir::Mutability::Not => "iter",
3466 hir::Mutability::Mut => "iter_mut",
3468 (ty_name, method_name)
3472 fn lint_into_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, self_ref_ty: Ty<'_>, method_span: Span) {
3473 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
3476 if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
3482 "this `.into_iter()` call is equivalent to `.{}()` and will not consume the `{}`",
3486 method_name.to_string(),
3487 Applicability::MachineApplicable,
3492 /// lint for `MaybeUninit::uninit().assume_init()` (we already have the latter)
3493 fn lint_maybe_uninit(cx: &LateContext<'_>, expr: &hir::Expr<'_>, outer: &hir::Expr<'_>) {
3495 if let hir::ExprKind::Call(ref callee, ref args) = expr.kind;
3497 if let hir::ExprKind::Path(ref path) = callee.kind;
3498 if match_qpath(path, &paths::MEM_MAYBEUNINIT_UNINIT);
3499 if !is_maybe_uninit_ty_valid(cx, cx.typeck_results().expr_ty_adjusted(outer));
3503 UNINIT_ASSUMED_INIT,
3505 "this call for this type may be undefined behavior"
3511 fn is_maybe_uninit_ty_valid(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
3513 ty::Array(ref component, _) => is_maybe_uninit_ty_valid(cx, component),
3514 ty::Tuple(ref types) => types.types().all(|ty| is_maybe_uninit_ty_valid(cx, ty)),
3515 ty::Adt(ref adt, _) => match_def_path(cx, adt.did, &paths::MEM_MAYBEUNINIT),
3520 fn lint_suspicious_map(cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
3525 "this call to `map()` won't have an effect on the call to `count()`",
3527 "make sure you did not confuse `map` with `filter` or `for_each`",
3531 const OPTION_AS_REF_DEREF_MSRV: RustcVersion = RustcVersion::new(1, 40, 0);
3533 /// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
3534 fn lint_option_as_ref_deref<'tcx>(
3535 cx: &LateContext<'tcx>,
3536 expr: &hir::Expr<'_>,
3537 as_ref_args: &[hir::Expr<'_>],
3538 map_args: &[hir::Expr<'_>],
3540 msrv: Option<&RustcVersion>,
3542 if !meets_msrv(msrv, &OPTION_AS_REF_DEREF_MSRV) {
3546 let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
3548 let option_ty = cx.typeck_results().expr_ty(&as_ref_args[0]);
3549 if !is_type_diagnostic_item(cx, option_ty, sym::option_type) {
3553 let deref_aliases: [&[&str]; 9] = [
3554 &paths::DEREF_TRAIT_METHOD,
3555 &paths::DEREF_MUT_TRAIT_METHOD,
3556 &paths::CSTRING_AS_C_STR,
3557 &paths::OS_STRING_AS_OS_STR,
3558 &paths::PATH_BUF_AS_PATH,
3559 &paths::STRING_AS_STR,
3560 &paths::STRING_AS_MUT_STR,
3561 &paths::VEC_AS_SLICE,
3562 &paths::VEC_AS_MUT_SLICE,
3565 let is_deref = match map_args[1].kind {
3566 hir::ExprKind::Path(ref expr_qpath) => cx
3567 .qpath_res(expr_qpath, map_args[1].hir_id)
3569 .map_or(false, |fun_def_id| {
3570 deref_aliases.iter().any(|path| match_def_path(cx, fun_def_id, path))
3572 hir::ExprKind::Closure(_, _, body_id, _, _) => {
3573 let closure_body = cx.tcx.hir().body(body_id);
3574 let closure_expr = remove_blocks(&closure_body.value);
3576 match &closure_expr.kind {
3577 hir::ExprKind::MethodCall(_, _, args, _) => {
3580 if let hir::ExprKind::Path(qpath) = &args[0].kind;
3581 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, args[0].hir_id);
3582 if closure_body.params[0].pat.hir_id == local_id;
3585 .expr_adjustments(&args[0])
3588 .collect::<Box<[_]>>();
3589 if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
3591 let method_did = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id).unwrap();
3592 deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
3598 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, ref inner) if same_mutability(m) => {
3600 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner1) = inner.kind;
3601 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner2) = inner1.kind;
3602 if let hir::ExprKind::Path(ref qpath) = inner2.kind;
3603 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, inner2.hir_id);
3605 closure_body.params[0].pat.hir_id == local_id
3618 let current_method = if is_mut {
3619 format!(".as_mut().map({})", snippet(cx, map_args[1].span, ".."))
3621 format!(".as_ref().map({})", snippet(cx, map_args[1].span, ".."))
3623 let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
3624 let hint = format!("{}.{}()", snippet(cx, as_ref_args[0].span, ".."), method_hint);
3625 let suggestion = format!("try using {} instead", method_hint);
3628 "called `{0}` on an Option value. This can be done more directly \
3629 by calling `{1}` instead",
3630 current_method, hint
3634 OPTION_AS_REF_DEREF,
3639 Applicability::MachineApplicable,
3644 fn lint_map_collect(
3645 cx: &LateContext<'_>,
3646 expr: &hir::Expr<'_>,
3647 map_args: &[hir::Expr<'_>],
3648 collect_args: &[hir::Expr<'_>],
3651 // called on Iterator
3652 if let [map_expr] = collect_args;
3653 if match_trait_method(cx, map_expr, &paths::ITERATOR);
3654 // return of collect `Result<(),_>`
3655 let collect_ret_ty = cx.typeck_results().expr_ty(expr);
3656 if is_type_diagnostic_item(cx, collect_ret_ty, sym::result_type);
3657 if let ty::Adt(_, substs) = collect_ret_ty.kind();
3658 if let Some(result_t) = substs.types().next();
3659 if result_t.is_unit();
3660 // get parts for snippet
3661 if let [iter, map_fn] = map_args;
3665 MAP_COLLECT_RESULT_UNIT,
3667 "`.map().collect()` can be replaced with `.try_for_each()`",
3670 "{}.try_for_each({})",
3671 snippet(cx, iter.span, ".."),
3672 snippet(cx, map_fn.span, "..")
3674 Applicability::MachineApplicable,
3680 /// Given a `Result<T, E>` type, return its error type (`E`).
3681 fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
3683 ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::result_type) => substs.types().nth(1),
3688 /// This checks whether a given type is known to implement Debug.
3689 fn has_debug_impl<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool {
3691 .get_diagnostic_item(sym::debug_trait)
3692 .map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
3697 StartsWith(&'static str),
3701 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
3702 (Convention::Eq("new"), &[SelfKind::No]),
3703 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
3704 (Convention::StartsWith("from_"), &[SelfKind::No]),
3705 (Convention::StartsWith("into_"), &[SelfKind::Value]),
3706 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
3707 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
3708 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
3711 const FN_HEADER: hir::FnHeader = hir::FnHeader {
3712 unsafety: hir::Unsafety::Normal,
3713 constness: hir::Constness::NotConst,
3714 asyncness: hir::IsAsync::NotAsync,
3715 abi: rustc_target::spec::abi::Abi::Rust,
3718 struct ShouldImplTraitCase {
3719 trait_name: &'static str,
3720 method_name: &'static str,
3722 fn_header: hir::FnHeader,
3723 // implicit self kind expected (none, self, &self, ...)
3724 self_kind: SelfKind,
3725 // checks against the output type
3726 output_type: OutType,
3727 // certain methods with explicit lifetimes can't implement the equivalent trait method
3728 lint_explicit_lifetime: bool,
3730 impl ShouldImplTraitCase {
3732 trait_name: &'static str,
3733 method_name: &'static str,
3735 fn_header: hir::FnHeader,
3736 self_kind: SelfKind,
3737 output_type: OutType,
3738 lint_explicit_lifetime: bool,
3739 ) -> ShouldImplTraitCase {
3740 ShouldImplTraitCase {
3747 lint_explicit_lifetime,
3751 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
3752 self.lint_explicit_lifetime
3753 || !impl_item.generics.params.iter().any(|p| {
3756 hir::GenericParamKind::Lifetime {
3757 kind: hir::LifetimeParamKind::Explicit
3765 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
3766 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3767 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3768 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3769 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3770 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3771 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3772 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3773 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3774 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3775 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3776 // FIXME: default doesn't work
3777 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
3778 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3779 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3780 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3781 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
3782 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
3783 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3784 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3785 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
3786 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3787 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3788 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3789 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3790 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3791 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
3792 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3793 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3794 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3795 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3796 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3800 const PATTERN_METHODS: [(&str, usize); 17] = [
3808 ("split_terminator", 1),
3809 ("rsplit_terminator", 1),
3814 ("match_indices", 1),
3815 ("rmatch_indices", 1),
3816 ("trim_start_matches", 1),
3817 ("trim_end_matches", 1),
3820 #[derive(Clone, Copy, PartialEq, Debug)]
3829 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3830 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
3831 if ty == parent_ty {
3833 } else if ty.is_box() {
3834 ty.boxed_ty() == parent_ty
3835 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
3836 if let ty::Adt(_, substs) = ty.kind() {
3837 substs.types().next().map_or(false, |t| t == parent_ty)
3846 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3847 if let ty::Ref(_, t, m) = *ty.kind() {
3848 return m == mutability && t == parent_ty;
3851 let trait_path = match mutability {
3852 hir::Mutability::Not => &paths::ASREF_TRAIT,
3853 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
3856 let trait_def_id = match get_trait_def_id(cx, trait_path) {
3858 None => return false,
3860 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3864 Self::Value => matches_value(cx, parent_ty, ty),
3865 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3866 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3867 Self::No => ty != parent_ty,
3872 fn description(self) -> &'static str {
3874 Self::Value => "self by value",
3875 Self::Ref => "self by reference",
3876 Self::RefMut => "self by mutable reference",
3877 Self::No => "no self",
3884 fn check(&self, other: &str) -> bool {
3886 Self::Eq(this) => this == other,
3887 Self::StartsWith(this) => other.starts_with(this) && this != other,
3892 impl fmt::Display for Convention {
3893 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
3895 Self::Eq(this) => this.fmt(f),
3896 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
3901 #[derive(Clone, Copy)]
3910 fn matches(self, cx: &LateContext<'_>, ty: &hir::FnRetTy<'_>) -> bool {
3911 let is_unit = |ty: &hir::Ty<'_>| SpanlessEq::new(cx).eq_ty_kind(&ty.kind, &hir::TyKind::Tup(&[]));
3913 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3914 (Self::Unit, &hir::FnRetTy::Return(ref ty)) if is_unit(ty) => true,
3915 (Self::Bool, &hir::FnRetTy::Return(ref ty)) if is_bool(ty) => true,
3916 (Self::Any, &hir::FnRetTy::Return(ref ty)) if !is_unit(ty) => true,
3917 (Self::Ref, &hir::FnRetTy::Return(ref ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3923 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3924 if let hir::TyKind::Path(ref p) = ty.kind {
3925 match_qpath(p, &["bool"])
3931 fn check_pointer_offset(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3934 if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.typeck_results().expr_ty(&args[0]).kind();
3935 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
3938 span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
3943 fn lint_filetype_is_file(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3944 let ty = cx.typeck_results().expr_ty(&args[0]);
3946 if !match_type(cx, ty, &paths::FILE_TYPE) {
3952 let lint_unary: &str;
3953 let help_unary: &str;
3955 if let Some(parent) = get_parent_expr(cx, expr);
3956 if let hir::ExprKind::Unary(op, _) = parent.kind;
3957 if op == hir::UnOp::UnNot;
3970 let lint_msg = format!("`{}FileType::is_file()` only {} regular files", lint_unary, verb);
3971 let help_msg = format!("use `{}FileType::is_dir()` instead", help_unary);
3972 span_lint_and_help(cx, FILETYPE_IS_FILE, span, &lint_msg, None, &help_msg);
3975 fn lint_from_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3976 let ty = cx.typeck_results().expr_ty(expr);
3977 let arg_ty = cx.typeck_results().expr_ty(&args[0]);
3980 if let Some(from_iter_id) = get_trait_def_id(cx, &paths::FROM_ITERATOR);
3981 if let Some(iter_id) = get_trait_def_id(cx, &paths::ITERATOR);
3983 if implements_trait(cx, ty, from_iter_id, &[]) && implements_trait(cx, arg_ty, iter_id, &[]);
3985 // `expr` implements `FromIterator` trait
3986 let iter_expr = snippet(cx, args[0].span, "..");
3989 FROM_ITER_INSTEAD_OF_COLLECT,
3991 "usage of `FromIterator::from_iter`",
3992 "use `.collect()` instead of `::from_iter()`",
3993 format!("{}.collect()", iter_expr),
3994 Applicability::MaybeIncorrect,
4000 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
4001 expected.constness == actual.constness
4002 && expected.unsafety == actual.unsafety
4003 && expected.asyncness == actual.asyncness