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};
26 use crate::consts::{constant, Constant};
27 use crate::utils::eager_or_lazy::is_lazyness_candidate;
28 use crate::utils::usage::mutated_variables;
30 contains_return, contains_ty, get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, higher,
31 implements_trait, in_macro, is_copy, is_expn_of, is_type_diagnostic_item, iter_input_pats, last_path_segment,
32 match_def_path, match_qpath, match_trait_method, match_type, match_var, meets_msrv, method_calls,
33 method_chain_args, paths, remove_blocks, return_ty, single_segment_path, snippet, snippet_with_applicability,
34 snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, sugg,
35 walk_ptrs_ty_depth, SpanlessEq,
38 declare_clippy_lint! {
39 /// **What it does:** Checks for `.unwrap()` calls on `Option`s and on `Result`s.
41 /// **Why is this bad?** It is better to handle the `None` or `Err` case,
42 /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
43 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
44 /// `Allow` by default.
46 /// `result.unwrap()` will let the thread panic on `Err` values.
47 /// Normally, you want to implement more sophisticated error handling,
48 /// and propagate errors upwards with `?` operator.
50 /// Even if you want to panic on errors, not all `Error`s implement good
51 /// messages on display. Therefore, it may be beneficial to look at the places
52 /// where they may get displayed. Activate this lint to do just that.
54 /// **Known problems:** None.
58 /// # let opt = Some(1);
64 /// opt.expect("more helpful message");
70 /// # let res: Result<usize, ()> = Ok(1);
76 /// res.expect("more helpful message");
80 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
83 declare_clippy_lint! {
84 /// **What it does:** Checks for `.expect()` calls on `Option`s and `Result`s.
86 /// **Why is this bad?** Usually it is better to handle the `None` or `Err` case.
87 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
88 /// this lint is `Allow` by default.
90 /// `result.expect()` will let the thread panic on `Err`
91 /// values. Normally, you want to implement more sophisticated error handling,
92 /// and propagate errors upwards with `?` operator.
94 /// **Known problems:** None.
98 /// # let opt = Some(1);
101 /// opt.expect("one");
104 /// let opt = Some(1);
111 /// # let res: Result<usize, ()> = Ok(1);
114 /// res.expect("one");
118 /// # Ok::<(), ()>(())
122 "using `.expect()` on `Result` or `Option`, which might be better handled"
125 declare_clippy_lint! {
126 /// **What it does:** Checks for methods that should live in a trait
127 /// implementation of a `std` trait (see [llogiq's blog
128 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
129 /// information) instead of an inherent implementation.
131 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
132 /// the code, often with very little cost. Also people seeing a `mul(...)`
134 /// may expect `*` to work equally, so you should have good reason to disappoint
137 /// **Known problems:** None.
143 /// fn add(&self, other: &X) -> X {
149 pub SHOULD_IMPLEMENT_TRAIT,
151 "defining a method that should be implementing a std trait"
154 declare_clippy_lint! {
155 /// **What it does:** Checks for methods with certain name prefixes and which
156 /// doesn't match how self is taken. The actual rules are:
158 /// |Prefix |`self` taken |
159 /// |-------|----------------------|
160 /// |`as_` |`&self` or `&mut self`|
162 /// |`into_`|`self` |
163 /// |`is_` |`&self` or none |
164 /// |`to_` |`&self` |
166 /// **Why is this bad?** Consistency breeds readability. If you follow the
167 /// conventions, your users won't be surprised that they, e.g., need to supply a
168 /// mutable reference to a `as_..` function.
170 /// **Known problems:** None.
176 /// fn as_str(self) -> &'static str {
182 pub WRONG_SELF_CONVENTION,
184 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
187 declare_clippy_lint! {
188 /// **What it does:** This is the same as
189 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
191 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
193 /// **Known problems:** Actually *renaming* the function may break clients if
194 /// the function is part of the public interface. In that case, be mindful of
195 /// the stability guarantees you've given your users.
201 /// pub fn as_str(self) -> &'a str {
206 pub WRONG_PUB_SELF_CONVENTION,
208 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
211 declare_clippy_lint! {
212 /// **What it does:** Checks for usage of `ok().expect(..)`.
214 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
215 /// directly to get a better error message.
217 /// **Known problems:** The error type needs to implement `Debug`
221 /// # let x = Ok::<_, ()>(());
224 /// x.ok().expect("why did I do this again?");
227 /// x.expect("why did I do this again?");
231 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
234 declare_clippy_lint! {
235 /// **What it does:** Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
236 /// `result.map(_).unwrap_or_else(_)`.
238 /// **Why is this bad?** Readability, these can be written more concisely (resp.) as
239 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
241 /// **Known problems:** The order of the arguments is not in execution order
245 /// # let x = Some(1);
248 /// x.map(|a| a + 1).unwrap_or(0);
251 /// x.map_or(0, |a| a + 1);
257 /// # let x: Result<usize, ()> = Ok(1);
258 /// # fn some_function(foo: ()) -> usize { 1 }
261 /// x.map(|a| a + 1).unwrap_or_else(some_function);
264 /// x.map_or_else(some_function, |a| a + 1);
268 "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)`"
271 declare_clippy_lint! {
272 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
274 /// **Why is this bad?** Readability, this can be written more concisely as
277 /// **Known problems:** The order of the arguments is not in execution order.
281 /// # let opt = Some(1);
284 /// opt.map_or(None, |a| Some(a + 1));
287 /// opt.and_then(|a| Some(a + 1));
289 pub OPTION_MAP_OR_NONE,
291 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
294 declare_clippy_lint! {
295 /// **What it does:** Checks for usage of `_.map_or(None, Some)`.
297 /// **Why is this bad?** Readability, this can be written more concisely as
300 /// **Known problems:** None.
306 /// # let r: Result<u32, &str> = Ok(1);
307 /// assert_eq!(Some(1), r.map_or(None, Some));
312 /// # let r: Result<u32, &str> = Ok(1);
313 /// assert_eq!(Some(1), r.ok());
315 pub RESULT_MAP_OR_INTO_OPTION,
317 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
320 declare_clippy_lint! {
321 /// **What it does:** Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
322 /// `_.or_else(|x| Err(y))`.
324 /// **Why is this bad?** Readability, this can be written more concisely as
325 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
327 /// **Known problems:** None
332 /// # fn opt() -> Option<&'static str> { Some("42") }
333 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
334 /// let _ = opt().and_then(|s| Some(s.len()));
335 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
336 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
339 /// The correct use would be:
342 /// # fn opt() -> Option<&'static str> { Some("42") }
343 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
344 /// let _ = opt().map(|s| s.len());
345 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
346 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
348 pub BIND_INSTEAD_OF_MAP,
350 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
353 declare_clippy_lint! {
354 /// **What it does:** Checks for usage of `_.filter(_).next()`.
356 /// **Why is this bad?** Readability, this can be written more concisely as
359 /// **Known problems:** None.
363 /// # let vec = vec![1];
364 /// vec.iter().filter(|x| **x == 0).next();
366 /// Could be written as
368 /// # let vec = vec![1];
369 /// vec.iter().find(|x| **x == 0);
373 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
376 declare_clippy_lint! {
377 /// **What it does:** Checks for usage of `_.skip_while(condition).next()`.
379 /// **Why is this bad?** Readability, this can be written more concisely as
380 /// `_.find(!condition)`.
382 /// **Known problems:** None.
386 /// # let vec = vec![1];
387 /// vec.iter().skip_while(|x| **x == 0).next();
389 /// Could be written as
391 /// # let vec = vec![1];
392 /// vec.iter().find(|x| **x != 0);
396 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
399 declare_clippy_lint! {
400 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
402 /// **Why is this bad?** Readability, this can be written more concisely as
405 /// **Known problems:**
409 /// let vec = vec![vec![1]];
412 /// vec.iter().map(|x| x.iter()).flatten();
415 /// vec.iter().flat_map(|x| x.iter());
419 "using combinations of `flatten` and `map` which can usually be written as a single method call"
422 declare_clippy_lint! {
423 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
424 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
426 /// **Why is this bad?** Readability, this can be written more concisely as
427 /// `_.filter_map(_)`.
429 /// **Known problems:** Often requires a condition + Option/Iterator creation
430 /// inside the closure.
434 /// let vec = vec![1];
437 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
440 /// vec.iter().filter_map(|x| if *x == 0 {
448 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
451 declare_clippy_lint! {
452 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
454 /// **Why is this bad?** Readability, this can be written more concisely as
457 /// **Known problems:** None
461 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
463 /// Can be written as
466 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
470 "using combination of `filter_map` and `next` which can usually be written as a single method call"
473 declare_clippy_lint! {
474 /// **What it does:** Checks for usage of `flat_map(|x| x)`.
476 /// **Why is this bad?** Readability, this can be written more concisely by using `flatten`.
478 /// **Known problems:** None
482 /// # let iter = vec![vec![0]].into_iter();
483 /// iter.flat_map(|x| x);
485 /// Can be written as
487 /// # let iter = vec![vec![0]].into_iter();
490 pub FLAT_MAP_IDENTITY,
492 "call to `flat_map` where `flatten` is sufficient"
495 declare_clippy_lint! {
496 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
498 /// **Why is this bad?** Readability, this can be written more concisely as
501 /// **Known problems:** Often requires a condition + Option/Iterator creation
502 /// inside the closure.
506 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
508 /// Can be written as
510 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
514 "using a combination of `find` and `map` can usually be written as a single method call"
517 declare_clippy_lint! {
518 /// **What it does:** Checks for an iterator or string search (such as `find()`,
519 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
521 /// **Why is this bad?** Readability, this can be written more concisely as
522 /// `_.any(_)` or `_.contains(_)`.
524 /// **Known problems:** None.
528 /// # let vec = vec![1];
529 /// vec.iter().find(|x| **x == 0).is_some();
531 /// Could be written as
533 /// # let vec = vec![1];
534 /// vec.iter().any(|x| *x == 0);
538 "using an iterator or string search followed by `is_some()`, which is more succinctly expressed as a call to `any()` or `contains()`"
541 declare_clippy_lint! {
542 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
543 /// if it starts with a given char.
545 /// **Why is this bad?** Readability, this can be written more concisely as
546 /// `_.starts_with(_)`.
548 /// **Known problems:** None.
552 /// let name = "foo";
553 /// if name.chars().next() == Some('_') {};
555 /// Could be written as
557 /// let name = "foo";
558 /// if name.starts_with('_') {};
562 "using `.chars().next()` to check if a string starts with a char"
565 declare_clippy_lint! {
566 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
567 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
568 /// `unwrap_or_default` instead.
570 /// **Why is this bad?** The function will always be called and potentially
571 /// allocate an object acting as the default.
573 /// **Known problems:** If the function has side-effects, not calling it will
574 /// change the semantic of the program, but you shouldn't rely on that anyway.
578 /// # let foo = Some(String::new());
579 /// foo.unwrap_or(String::new());
581 /// this can instead be written:
583 /// # let foo = Some(String::new());
584 /// foo.unwrap_or_else(String::new);
588 /// # let foo = Some(String::new());
589 /// foo.unwrap_or_default();
593 "using any `*or` method with a function call, which suggests `*or_else`"
596 declare_clippy_lint! {
597 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
598 /// etc., and suggests to use `unwrap_or_else` instead
600 /// **Why is this bad?** The function will always be called.
602 /// **Known problems:** If the function has side-effects, not calling it will
603 /// change the semantics of the program, but you shouldn't rely on that anyway.
607 /// # let foo = Some(String::new());
608 /// # let err_code = "418";
609 /// # let err_msg = "I'm a teapot";
610 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
614 /// # let foo = Some(String::new());
615 /// # let err_code = "418";
616 /// # let err_msg = "I'm a teapot";
617 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
619 /// this can instead be written:
621 /// # let foo = Some(String::new());
622 /// # let err_code = "418";
623 /// # let err_msg = "I'm a teapot";
624 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
628 "using any `expect` method with a function call"
631 declare_clippy_lint! {
632 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
634 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
635 /// generics, not for using the `clone` method on a concrete type.
637 /// **Known problems:** None.
645 "using `clone` on a `Copy` type"
648 declare_clippy_lint! {
649 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
650 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
651 /// function syntax instead (e.g., `Rc::clone(foo)`).
653 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
654 /// can obscure the fact that only the pointer is being cloned, not the underlying
659 /// # use std::rc::Rc;
660 /// let x = Rc::new(1);
668 pub CLONE_ON_REF_PTR,
670 "using 'clone' on a ref-counted pointer"
673 declare_clippy_lint! {
674 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
676 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
677 /// cloning the underlying `T`.
679 /// **Known problems:** None.
686 /// let z = y.clone();
687 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
690 pub CLONE_DOUBLE_REF,
692 "using `clone` on `&&T`"
695 declare_clippy_lint! {
696 /// **What it does:** Checks for usage of `.to_string()` on an `&&T` where
697 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
699 /// **Why is this bad?** This bypasses the specialized implementation of
700 /// `ToString` and instead goes through the more expensive string formatting
703 /// **Known problems:** None.
707 /// // Generic implementation for `T: Display` is used (slow)
708 /// ["foo", "bar"].iter().map(|s| s.to_string());
710 /// // OK, the specialized impl is used
711 /// ["foo", "bar"].iter().map(|&s| s.to_string());
713 pub INEFFICIENT_TO_STRING,
715 "using `to_string` on `&&T` where `T: ToString`"
718 declare_clippy_lint! {
719 /// **What it does:** Checks for `new` not returning a type that contains `Self`.
721 /// **Why is this bad?** As a convention, `new` methods are used to make a new
722 /// instance of a type.
724 /// **Known problems:** None.
727 /// In an impl block:
730 /// # struct NotAFoo;
732 /// fn new() -> NotAFoo {
742 /// // Bad. The type name must contain `Self`
743 /// fn new() -> Bar {
751 /// # struct FooError;
753 /// // Good. Return type contains `Self`
754 /// fn new() -> Result<Foo, FooError> {
760 /// Or in a trait definition:
762 /// pub trait Trait {
763 /// // Bad. The type name must contain `Self`
769 /// pub trait Trait {
770 /// // Good. Return type contains `Self`
771 /// fn new() -> Self;
776 "not returning type containing `Self` in a `new` method"
779 declare_clippy_lint! {
780 /// **What it does:** Checks for string methods that receive a single-character
781 /// `str` as an argument, e.g., `_.split("x")`.
783 /// **Why is this bad?** Performing these methods using a `char` is faster than
786 /// **Known problems:** Does not catch multi-byte unicode characters.
795 pub SINGLE_CHAR_PATTERN,
797 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
800 declare_clippy_lint! {
801 /// **What it does:** Checks for calling `.step_by(0)` on iterators which panics.
803 /// **Why is this bad?** This very much looks like an oversight. Use `panic!()` instead if you
804 /// actually intend to panic.
806 /// **Known problems:** None.
809 /// ```rust,should_panic
810 /// for x in (0..100).step_by(0) {
814 pub ITERATOR_STEP_BY_ZERO,
816 "using `Iterator::step_by(0)`, which will panic at runtime"
819 declare_clippy_lint! {
820 /// **What it does:** Checks for the use of `iter.nth(0)`.
822 /// **Why is this bad?** `iter.next()` is equivalent to
823 /// `iter.nth(0)`, as they both consume the next element,
824 /// but is more readable.
826 /// **Known problems:** None.
831 /// # use std::collections::HashSet;
833 /// # let mut s = HashSet::new();
835 /// let x = s.iter().nth(0);
838 /// # let mut s = HashSet::new();
840 /// let x = s.iter().next();
844 "replace `iter.nth(0)` with `iter.next()`"
847 declare_clippy_lint! {
848 /// **What it does:** Checks for use of `.iter().nth()` (and the related
849 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
851 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
854 /// **Known problems:** None.
858 /// let some_vec = vec![0, 1, 2, 3];
859 /// let bad_vec = some_vec.iter().nth(3);
860 /// let bad_slice = &some_vec[..].iter().nth(3);
862 /// The correct use would be:
864 /// let some_vec = vec![0, 1, 2, 3];
865 /// let bad_vec = some_vec.get(3);
866 /// let bad_slice = &some_vec[..].get(3);
870 "using `.iter().nth()` on a standard library type with O(1) element access"
873 declare_clippy_lint! {
874 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
876 /// **Why is this bad?** `.nth(x)` is cleaner
878 /// **Known problems:** None.
882 /// let some_vec = vec![0, 1, 2, 3];
883 /// let bad_vec = some_vec.iter().skip(3).next();
884 /// let bad_slice = &some_vec[..].iter().skip(3).next();
886 /// The correct use would be:
888 /// let some_vec = vec![0, 1, 2, 3];
889 /// let bad_vec = some_vec.iter().nth(3);
890 /// let bad_slice = &some_vec[..].iter().nth(3);
894 "using `.skip(x).next()` on an iterator"
897 declare_clippy_lint! {
898 /// **What it does:** Checks for use of `.get().unwrap()` (or
899 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
901 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
904 /// **Known problems:** Not a replacement for error handling: Using either
905 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
906 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
907 /// temporary placeholder for dealing with the `Option` type, then this does
908 /// not mitigate the need for error handling. If there is a chance that `.get()`
909 /// will be `None` in your program, then it is advisable that the `None` case
910 /// is handled in a future refactor instead of using `.unwrap()` or the Index
915 /// let mut some_vec = vec![0, 1, 2, 3];
916 /// let last = some_vec.get(3).unwrap();
917 /// *some_vec.get_mut(0).unwrap() = 1;
919 /// The correct use would be:
921 /// let mut some_vec = vec![0, 1, 2, 3];
922 /// let last = some_vec[3];
927 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
930 declare_clippy_lint! {
931 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
932 /// `&str` or `String`.
934 /// **Why is this bad?** `.push_str(s)` is clearer
936 /// **Known problems:** None.
941 /// let def = String::from("def");
942 /// let mut s = String::new();
943 /// s.extend(abc.chars());
944 /// s.extend(def.chars());
946 /// The correct use would be:
949 /// let def = String::from("def");
950 /// let mut s = String::new();
952 /// s.push_str(&def);
954 pub STRING_EXTEND_CHARS,
956 "using `x.extend(s.chars())` where s is a `&str` or `String`"
959 declare_clippy_lint! {
960 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
963 /// **Why is this bad?** `.to_vec()` is clearer
965 /// **Known problems:** None.
969 /// let s = [1, 2, 3, 4, 5];
970 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
972 /// The better use would be:
974 /// let s = [1, 2, 3, 4, 5];
975 /// let s2: Vec<isize> = s.to_vec();
977 pub ITER_CLONED_COLLECT,
979 "using `.cloned().collect()` on slice to create a `Vec`"
982 declare_clippy_lint! {
983 /// **What it does:** Checks for usage of `_.chars().last()` or
984 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
986 /// **Why is this bad?** Readability, this can be written more concisely as
987 /// `_.ends_with(_)`.
989 /// **Known problems:** None.
993 /// # let name = "_";
996 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
999 /// name.ends_with('_') || name.ends_with('-');
1003 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1006 declare_clippy_lint! {
1007 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
1008 /// types before and after the call are the same.
1010 /// **Why is this bad?** The call is unnecessary.
1012 /// **Known problems:** None.
1016 /// # fn do_stuff(x: &[i32]) {}
1017 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1018 /// do_stuff(x.as_ref());
1020 /// The correct use would be:
1022 /// # fn do_stuff(x: &[i32]) {}
1023 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1028 "using `as_ref` where the types before and after the call are the same"
1031 declare_clippy_lint! {
1032 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
1033 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1034 /// `sum` or `product`.
1036 /// **Why is this bad?** Readability.
1038 /// **Known problems:** None.
1042 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1044 /// This could be written as:
1046 /// let _ = (0..3).any(|x| x > 2);
1048 pub UNNECESSARY_FOLD,
1050 "using `fold` when a more succinct alternative exists"
1053 declare_clippy_lint! {
1054 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1055 /// More specifically it checks if the closure provided is only performing one of the
1056 /// filter or map operations and suggests the appropriate option.
1058 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
1059 /// operation is being performed.
1061 /// **Known problems:** None
1065 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1067 /// // As there is no transformation of the argument this could be written as:
1068 /// let _ = (0..3).filter(|&x| x > 2);
1072 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1074 /// // As there is no conditional check on the argument this could be written as:
1075 /// let _ = (0..4).map(|x| x + 1);
1077 pub UNNECESSARY_FILTER_MAP,
1079 "using `filter_map` when a more succinct alternative exists"
1082 declare_clippy_lint! {
1083 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
1086 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
1087 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1088 /// `iter_mut` directly.
1090 /// **Known problems:** None
1096 /// let _ = (&vec![3, 4, 5]).into_iter();
1099 /// let _ = (&vec![3, 4, 5]).iter();
1101 pub INTO_ITER_ON_REF,
1103 "using `.into_iter()` on a reference"
1106 declare_clippy_lint! {
1107 /// **What it does:** Checks for calls to `map` followed by a `count`.
1109 /// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
1110 /// If the `map` call is intentional, this should be rewritten. Or, if you intend to
1111 /// drive the iterator to completion, you can just use `for_each` instead.
1113 /// **Known problems:** None
1118 /// let _ = (0..3).map(|x| x + 2).count();
1122 "suspicious usage of map"
1125 declare_clippy_lint! {
1126 /// **What it does:** Checks for `MaybeUninit::uninit().assume_init()`.
1128 /// **Why is this bad?** For most types, this is undefined behavior.
1130 /// **Known problems:** For now, we accept empty tuples and tuples / arrays
1131 /// of `MaybeUninit`. There may be other types that allow uninitialized
1132 /// data, but those are not yet rigorously defined.
1137 /// // Beware the UB
1138 /// use std::mem::MaybeUninit;
1140 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1143 /// Note that the following is OK:
1146 /// use std::mem::MaybeUninit;
1148 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1149 /// MaybeUninit::uninit().assume_init()
1152 pub UNINIT_ASSUMED_INIT,
1154 "`MaybeUninit::uninit().assume_init()`"
1157 declare_clippy_lint! {
1158 /// **What it does:** Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1160 /// **Why is this bad?** These can be written simply with `saturating_add/sub` methods.
1165 /// # let y: u32 = 0;
1166 /// # let x: u32 = 100;
1167 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1168 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1171 /// can be written using dedicated methods for saturating addition/subtraction as:
1174 /// # let y: u32 = 0;
1175 /// # let x: u32 = 100;
1176 /// let add = x.saturating_add(y);
1177 /// let sub = x.saturating_sub(y);
1179 pub MANUAL_SATURATING_ARITHMETIC,
1181 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1184 declare_clippy_lint! {
1185 /// **What it does:** Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1186 /// zero-sized types
1188 /// **Why is this bad?** This is a no-op, and likely unintended
1190 /// **Known problems:** None
1194 /// unsafe { (&() as *const ()).offset(1) };
1198 "Check for offset calculations on raw pointers to zero-sized types"
1201 declare_clippy_lint! {
1202 /// **What it does:** Checks for `FileType::is_file()`.
1204 /// **Why is this bad?** When people testing a file type with `FileType::is_file`
1205 /// they are testing whether a path is something they can get bytes from. But
1206 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1207 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1213 /// let metadata = std::fs::metadata("foo.txt")?;
1214 /// let filetype = metadata.file_type();
1216 /// if filetype.is_file() {
1219 /// # Ok::<_, std::io::Error>(())
1223 /// should be written as:
1227 /// let metadata = std::fs::metadata("foo.txt")?;
1228 /// let filetype = metadata.file_type();
1230 /// if !filetype.is_dir() {
1233 /// # Ok::<_, std::io::Error>(())
1236 pub FILETYPE_IS_FILE,
1238 "`FileType::is_file` is not recommended to test for readable file type"
1241 declare_clippy_lint! {
1242 /// **What it does:** Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1244 /// **Why is this bad?** Readability, this can be written more concisely as
1247 /// **Known problems:** None.
1251 /// # let opt = Some("".to_string());
1252 /// opt.as_ref().map(String::as_str)
1255 /// Can be written as
1257 /// # let opt = Some("".to_string());
1261 pub OPTION_AS_REF_DEREF,
1263 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1266 declare_clippy_lint! {
1267 /// **What it does:** Checks for usage of `iter().next()` on a Slice or an Array
1269 /// **Why is this bad?** These can be shortened into `.get()`
1271 /// **Known problems:** None.
1275 /// # let a = [1, 2, 3];
1276 /// # let b = vec![1, 2, 3];
1277 /// a[2..].iter().next();
1278 /// b.iter().next();
1280 /// should be written as:
1282 /// # let a = [1, 2, 3];
1283 /// # let b = vec![1, 2, 3];
1287 pub ITER_NEXT_SLICE,
1289 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1292 declare_clippy_lint! {
1293 /// **What it does:** Warns when using `push_str`/`insert_str` with a single-character string literal
1294 /// where `push`/`insert` with a `char` would work fine.
1296 /// **Why is this bad?** It's less clear that we are pushing a single character.
1298 /// **Known problems:** None
1302 /// let mut string = String::new();
1303 /// string.insert_str(0, "R");
1304 /// string.push_str("R");
1306 /// Could be written as
1308 /// let mut string = String::new();
1309 /// string.insert(0, 'R');
1310 /// string.push('R');
1312 pub SINGLE_CHAR_ADD_STR,
1314 "`push_str()` or `insert_str()` used with a single-character string literal as parameter"
1317 declare_clippy_lint! {
1318 /// **What it does:** As the counterpart to `or_fun_call`, this lint looks for unnecessary
1319 /// lazily evaluated closures on `Option` and `Result`.
1321 /// This lint suggests changing the following functions, when eager evaluation results in
1323 /// - `unwrap_or_else` to `unwrap_or`
1324 /// - `and_then` to `and`
1325 /// - `or_else` to `or`
1326 /// - `get_or_insert_with` to `get_or_insert`
1327 /// - `ok_or_else` to `ok_or`
1329 /// **Why is this bad?** Using eager evaluation is shorter and simpler in some cases.
1331 /// **Known problems:** It is possible, but not recommended for `Deref` and `Index` to have
1332 /// side effects. Eagerly evaluating them can change the semantics of the program.
1337 /// // example code where clippy issues a warning
1338 /// let opt: Option<u32> = None;
1340 /// opt.unwrap_or_else(|| 42);
1344 /// let opt: Option<u32> = None;
1346 /// opt.unwrap_or(42);
1348 pub UNNECESSARY_LAZY_EVALUATIONS,
1350 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1353 declare_clippy_lint! {
1354 /// **What it does:** Checks for usage of `_.map(_).collect::<Result<(), _>()`.
1356 /// **Why is this bad?** Using `try_for_each` instead is more readable and idiomatic.
1358 /// **Known problems:** None
1363 /// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
1367 /// (0..3).try_for_each(|t| Err(t));
1369 pub MAP_COLLECT_RESULT_UNIT,
1371 "using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
1374 declare_clippy_lint! {
1375 /// **What it does:** Checks for `from_iter()` function calls on types that implement the `FromIterator`
1378 /// **Why is this bad?** It is recommended style to use collect. See
1379 /// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
1381 /// **Known problems:** None.
1386 /// use std::iter::FromIterator;
1388 /// let five_fives = std::iter::repeat(5).take(5);
1390 /// let v = Vec::from_iter(five_fives);
1392 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1396 /// let five_fives = std::iter::repeat(5).take(5);
1398 /// let v: Vec<i32> = five_fives.collect();
1400 /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
1402 pub FROM_ITER_INSTEAD_OF_COLLECT,
1404 "use `.collect()` instead of `::from_iter()`"
1407 pub struct Methods {
1408 msrv: Option<RustcVersion>,
1413 pub fn new(msrv: Option<RustcVersion>) -> Self {
1418 impl_lint_pass!(Methods => [
1421 SHOULD_IMPLEMENT_TRAIT,
1422 WRONG_SELF_CONVENTION,
1423 WRONG_PUB_SELF_CONVENTION,
1426 RESULT_MAP_OR_INTO_OPTION,
1428 BIND_INSTEAD_OF_MAP,
1436 INEFFICIENT_TO_STRING,
1438 SINGLE_CHAR_PATTERN,
1439 SINGLE_CHAR_ADD_STR,
1448 ITERATOR_STEP_BY_ZERO,
1454 STRING_EXTEND_CHARS,
1455 ITER_CLONED_COLLECT,
1458 UNNECESSARY_FILTER_MAP,
1461 UNINIT_ASSUMED_INIT,
1462 MANUAL_SATURATING_ARITHMETIC,
1465 OPTION_AS_REF_DEREF,
1466 UNNECESSARY_LAZY_EVALUATIONS,
1467 MAP_COLLECT_RESULT_UNIT,
1468 FROM_ITER_INSTEAD_OF_COLLECT,
1471 impl<'tcx> LateLintPass<'tcx> for Methods {
1472 #[allow(clippy::too_many_lines)]
1473 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
1474 if in_macro(expr.span) {
1478 let (method_names, arg_lists, method_spans) = method_calls(expr, 2);
1479 let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
1480 let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
1482 match method_names.as_slice() {
1483 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
1484 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
1485 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
1486 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
1487 ["expect", ..] => lint_expect(cx, expr, arg_lists[0]),
1488 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
1489 ["unwrap_or_else", "map"] => {
1490 if !lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0], self.msrv.as_ref()) {
1491 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or");
1494 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
1495 ["and_then", ..] => {
1496 let biom_option_linted = bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
1497 let biom_result_linted = bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
1498 if !biom_option_linted && !biom_result_linted {
1499 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "and");
1502 ["or_else", ..] => {
1503 if !bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]) {
1504 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "or");
1507 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
1508 ["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
1509 ["next", "iter"] => lint_iter_next(cx, expr, arg_lists[1]),
1510 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
1511 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
1512 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1], self.msrv.as_ref()),
1513 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
1514 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1515 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1516 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0], method_spans[0]),
1517 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
1518 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
1519 ["is_some", "position"] => {
1520 lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
1522 ["is_some", "rposition"] => {
1523 lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
1525 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
1526 ["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
1527 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
1528 ["nth", ..] => lint_iter_nth_zero(cx, expr, arg_lists[0]),
1529 ["step_by", ..] => lint_step_by(cx, expr, arg_lists[0]),
1530 ["next", "skip"] => lint_iter_skip_next(cx, expr, arg_lists[1]),
1531 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
1532 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
1533 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
1534 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0], method_spans[0]),
1535 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
1536 ["count", "map"] => lint_suspicious_map(cx, expr),
1537 ["assume_init"] => lint_maybe_uninit(cx, &arg_lists[0][0], expr),
1538 ["unwrap_or", arith @ ("checked_add" | "checked_sub" | "checked_mul")] => {
1539 manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
1541 ["add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub"] => {
1542 check_pointer_offset(cx, expr, arg_lists[0])
1544 ["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
1545 ["map", "as_ref"] => {
1546 lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false, self.msrv.as_ref())
1548 ["map", "as_mut"] => {
1549 lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true, self.msrv.as_ref())
1551 ["unwrap_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or"),
1552 ["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "get_or_insert"),
1553 ["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "ok_or"),
1554 ["collect", "map"] => lint_map_collect(cx, expr, arg_lists[1], arg_lists[0]),
1559 hir::ExprKind::Call(ref func, ref args) => {
1560 if let hir::ExprKind::Path(path) = &func.kind {
1561 if match_qpath(path, &["from_iter"]) {
1562 lint_from_iter(cx, expr, args);
1566 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args, _) => {
1567 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1568 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1570 let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0]);
1571 if args.len() == 1 && method_call.ident.name == sym!(clone) {
1572 lint_clone_on_copy(cx, expr, &args[0], self_ty);
1573 lint_clone_on_ref_ptr(cx, expr, &args[0]);
1575 if args.len() == 1 && method_call.ident.name == sym!(to_string) {
1576 inefficient_to_string::lint(cx, expr, &args[0], self_ty);
1579 if let Some(fn_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
1580 if match_def_path(cx, fn_def_id, &paths::PUSH_STR) {
1581 lint_single_char_push_string(cx, expr, args);
1582 } else if match_def_path(cx, fn_def_id, &paths::INSERT_STR) {
1583 lint_single_char_insert_string(cx, expr, args);
1587 match self_ty.kind() {
1588 ty::Ref(_, ty, _) if *ty.kind() == ty::Str => {
1589 for &(method, pos) in &PATTERN_METHODS {
1590 if method_call.ident.name.as_str() == method && args.len() > pos {
1591 lint_single_char_pattern(cx, expr, &args[pos]);
1595 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
1596 lint_into_iter(cx, expr, self_ty, *method_span);
1601 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1602 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1604 let mut info = BinaryExprInfo {
1608 eq: op.node == hir::BinOpKind::Eq,
1610 lint_binary_expr_with_method_call(cx, &mut info);
1616 #[allow(clippy::too_many_lines)]
1617 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
1618 if in_external_macro(cx.sess(), impl_item.span) {
1621 let name = impl_item.ident.name.as_str();
1622 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1623 let item = cx.tcx.hir().expect_item(parent);
1624 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1625 let self_ty = cx.tcx.type_of(def_id);
1627 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
1628 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1629 if let hir::ItemKind::Impl{ of_trait: None, .. } = item.kind;
1631 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1632 let method_sig = cx.tcx.fn_sig(method_def_id);
1633 let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
1635 let first_arg_ty = &method_sig.inputs().iter().next();
1637 // check conventions w.r.t. conversion method names and predicates
1638 if let Some(first_arg_ty) = first_arg_ty;
1641 if cx.access_levels.is_exported(impl_item.hir_id) {
1642 // check missing trait implementations
1643 for method_config in &TRAIT_METHODS {
1644 if name == method_config.method_name &&
1645 sig.decl.inputs.len() == method_config.param_count &&
1646 method_config.output_type.matches(cx, &sig.decl.output) &&
1647 method_config.self_kind.matches(cx, self_ty, first_arg_ty) &&
1648 fn_header_equals(method_config.fn_header, sig.header) &&
1649 method_config.lifetime_param_cond(&impl_item)
1653 SHOULD_IMPLEMENT_TRAIT,
1656 "method `{}` can be confused for the standard trait method `{}::{}`",
1657 method_config.method_name,
1658 method_config.trait_name,
1659 method_config.method_name
1663 "consider implementing the trait `{}` or choosing a less ambiguous method name",
1664 method_config.trait_name
1671 if let Some((ref conv, self_kinds)) = &CONVENTIONS
1673 .find(|(ref conv, _)| conv.check(&name))
1675 if !self_kinds.iter().any(|k| k.matches(cx, self_ty, first_arg_ty)) {
1676 let lint = if item.vis.node.is_pub() {
1677 WRONG_PUB_SELF_CONVENTION
1679 WRONG_SELF_CONVENTION
1686 &format!("methods called `{}` usually take {}; consider choosing a less ambiguous name",
1690 .map(|k| k.description())
1691 .collect::<Vec<_>>()
1700 // if this impl block implements a trait, lint in trait definition instead
1701 if let hir::ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
1705 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
1706 let ret_ty = return_ty(cx, impl_item.hir_id);
1708 // walk the return type and check for Self (this does not check associated types)
1709 if contains_ty(ret_ty, self_ty) {
1713 // if return type is impl trait, check the associated types
1714 if let ty::Opaque(def_id, _) = *ret_ty.kind() {
1715 // one of the associated types must be Self
1716 for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
1717 if let ty::PredicateAtom::Projection(projection_predicate) = predicate.skip_binders() {
1718 // walk the associated type and check for Self
1719 if contains_ty(projection_predicate.ty, self_ty) {
1726 if name == "new" && !TyS::same_type(ret_ty, self_ty) {
1731 "methods called `new` usually return `Self`",
1737 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
1739 if !in_external_macro(cx.tcx.sess, item.span);
1740 if item.ident.name == sym::new;
1741 if let TraitItemKind::Fn(_, _) = item.kind;
1742 let ret_ty = return_ty(cx, item.hir_id);
1743 let self_ty = TraitRef::identity(cx.tcx, item.hir_id.owner.to_def_id()).self_ty();
1744 if !contains_ty(ret_ty, self_ty);
1751 "methods called `new` usually return `Self`",
1757 extract_msrv_attr!(LateContext);
1760 /// Checks for the `OR_FUN_CALL` lint.
1761 #[allow(clippy::too_many_lines)]
1762 fn lint_or_fun_call<'tcx>(
1763 cx: &LateContext<'tcx>,
1764 expr: &hir::Expr<'_>,
1767 args: &'tcx [hir::Expr<'_>],
1769 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1770 fn check_unwrap_or_default(
1771 cx: &LateContext<'_>,
1773 fun: &hir::Expr<'_>,
1774 self_expr: &hir::Expr<'_>,
1775 arg: &hir::Expr<'_>,
1781 if name == "unwrap_or";
1782 if let hir::ExprKind::Path(ref qpath) = fun.kind;
1783 let path = &*last_path_segment(qpath).ident.as_str();
1784 if ["default", "new"].contains(&path);
1785 let arg_ty = cx.typeck_results().expr_ty(arg);
1786 if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
1787 if implements_trait(cx, arg_ty, default_trait_id, &[]);
1790 let mut applicability = Applicability::MachineApplicable;
1795 &format!("use of `{}` followed by a call to `{}`", name, path),
1798 "{}.unwrap_or_default()",
1799 snippet_with_applicability(cx, self_expr.span, "..", &mut applicability)
1811 /// Checks for `*or(foo())`.
1812 #[allow(clippy::too_many_arguments)]
1813 fn check_general_case<'tcx>(
1814 cx: &LateContext<'tcx>,
1817 self_expr: &hir::Expr<'_>,
1818 arg: &'tcx hir::Expr<'_>,
1820 // None if lambda is required
1821 fun_span: Option<Span>,
1823 // (path, fn_has_argument, methods, suffix)
1824 static KNOW_TYPES: [(&[&str], bool, &[&str], &str); 4] = [
1825 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1826 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1827 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1828 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1831 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = &arg.kind {
1832 if path.ident.as_str() == "len" {
1833 let ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
1836 ty::Slice(_) | ty::Array(_, _) => return,
1840 if is_type_diagnostic_item(cx, ty, sym::vec_type) {
1847 if KNOW_TYPES.iter().any(|k| k.2.contains(&name));
1849 if is_lazyness_candidate(cx, arg);
1850 if !contains_return(&arg);
1852 let self_ty = cx.typeck_results().expr_ty(self_expr);
1854 if let Some(&(_, fn_has_arguments, poss, suffix)) =
1855 KNOW_TYPES.iter().find(|&&i| match_type(cx, self_ty, i.0));
1857 if poss.contains(&name);
1860 let sugg: Cow<'_, str> = {
1861 let (snippet_span, use_lambda) = match (fn_has_arguments, fun_span) {
1862 (false, Some(fun_span)) => (fun_span, false),
1863 _ => (arg.span, true),
1865 let snippet = snippet_with_macro_callsite(cx, snippet_span, "..");
1867 let l_arg = if fn_has_arguments { "_" } else { "" };
1868 format!("|{}| {}", l_arg, snippet).into()
1873 let span_replace_word = method_span.with_hi(span.hi());
1878 &format!("use of `{}` followed by a function call", name),
1880 format!("{}_{}({})", name, suffix, sugg),
1881 Applicability::HasPlaceholders,
1887 if args.len() == 2 {
1888 match args[1].kind {
1889 hir::ExprKind::Call(ref fun, ref or_args) => {
1890 let or_has_args = !or_args.is_empty();
1891 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1892 let fun_span = if or_has_args { None } else { Some(fun.span) };
1893 check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, fun_span);
1896 hir::ExprKind::Index(..) | hir::ExprKind::MethodCall(..) => {
1897 check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, None);
1904 /// Checks for the `EXPECT_FUN_CALL` lint.
1905 #[allow(clippy::too_many_lines)]
1906 fn lint_expect_fun_call(
1907 cx: &LateContext<'_>,
1908 expr: &hir::Expr<'_>,
1911 args: &[hir::Expr<'_>],
1913 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1915 fn get_arg_root<'a>(cx: &LateContext<'_>, arg: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
1916 let mut arg_root = arg;
1918 arg_root = match &arg_root.kind {
1919 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => expr,
1920 hir::ExprKind::MethodCall(method_name, _, call_args, _) => {
1921 if call_args.len() == 1
1922 && (method_name.ident.name == sym::as_str || method_name.ident.name == sym!(as_ref))
1924 let arg_type = cx.typeck_results().expr_ty(&call_args[0]);
1925 let base_type = arg_type.peel_refs();
1926 *base_type.kind() == ty::Str || is_type_diagnostic_item(cx, base_type, sym::string_type)
1940 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1941 // converted to string.
1942 fn requires_to_string(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1943 let arg_ty = cx.typeck_results().expr_ty(arg);
1944 if is_type_diagnostic_item(cx, arg_ty, sym::string_type) {
1947 if let ty::Ref(_, ty, ..) = arg_ty.kind() {
1948 if *ty.kind() == ty::Str && can_be_static_str(cx, arg) {
1955 // Check if an expression could have type `&'static str`, knowing that it
1956 // has type `&str` for some lifetime.
1957 fn can_be_static_str(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1959 hir::ExprKind::Lit(_) => true,
1960 hir::ExprKind::Call(fun, _) => {
1961 if let hir::ExprKind::Path(ref p) = fun.kind {
1962 match cx.qpath_res(p, fun.hir_id) {
1963 hir::def::Res::Def(hir::def::DefKind::Fn | hir::def::DefKind::AssocFn, def_id) => matches!(
1964 cx.tcx.fn_sig(def_id).output().skip_binder().kind(),
1965 ty::Ref(ty::ReStatic, ..)
1973 hir::ExprKind::MethodCall(..) => {
1975 .type_dependent_def_id(arg.hir_id)
1976 .map_or(false, |method_id| {
1978 cx.tcx.fn_sig(method_id).output().skip_binder().kind(),
1979 ty::Ref(ty::ReStatic, ..)
1983 hir::ExprKind::Path(ref p) => matches!(
1984 cx.qpath_res(p, arg.hir_id),
1985 hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static, _)
1991 fn generate_format_arg_snippet(
1992 cx: &LateContext<'_>,
1994 applicability: &mut Applicability,
1997 if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref format_arg) = a.kind;
1998 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.kind;
1999 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.kind;
2004 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
2012 fn is_call(node: &hir::ExprKind<'_>) -> bool {
2014 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => {
2017 hir::ExprKind::Call(..)
2018 | hir::ExprKind::MethodCall(..)
2019 // These variants are debatable or require further examination
2020 | hir::ExprKind::Match(..)
2021 | hir::ExprKind::Block{ .. } => true,
2026 if args.len() != 2 || name != "expect" || !is_call(&args[1].kind) {
2030 let receiver_type = cx.typeck_results().expr_ty_adjusted(&args[0]);
2031 let closure_args = if is_type_diagnostic_item(cx, receiver_type, sym::option_type) {
2033 } else if is_type_diagnostic_item(cx, receiver_type, sym::result_type) {
2039 let arg_root = get_arg_root(cx, &args[1]);
2041 let span_replace_word = method_span.with_hi(expr.span.hi());
2043 let mut applicability = Applicability::MachineApplicable;
2045 //Special handling for `format!` as arg_root
2047 if let hir::ExprKind::Block(block, None) = &arg_root.kind;
2048 if block.stmts.len() == 1;
2049 if let hir::StmtKind::Local(local) = &block.stmts[0].kind;
2050 if let Some(arg_root) = &local.init;
2051 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.kind;
2052 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1;
2053 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].kind;
2055 let fmt_spec = &format_args[0];
2056 let fmt_args = &format_args[1];
2058 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
2060 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
2062 let sugg = args.join(", ");
2068 &format!("use of `{}` followed by a function call", name),
2070 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
2078 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
2079 if requires_to_string(cx, arg_root) {
2080 arg_root_snippet.to_mut().push_str(".to_string()");
2087 &format!("use of `{}` followed by a function call", name),
2089 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
2094 /// Checks for the `CLONE_ON_COPY` lint.
2095 fn lint_clone_on_copy(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
2096 let ty = cx.typeck_results().expr_ty(expr);
2097 if let ty::Ref(_, inner, _) = arg_ty.kind() {
2098 if let ty::Ref(_, innermost, _) = inner.kind() {
2103 "using `clone` on a double-reference; \
2104 this will copy the reference instead of cloning the inner type",
2106 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
2107 let mut ty = innermost;
2109 while let ty::Ref(_, inner, _) = ty.kind() {
2113 let refs: String = iter::repeat('&').take(n + 1).collect();
2114 let derefs: String = iter::repeat('*').take(n).collect();
2115 let explicit = format!("<{}{}>::clone({})", refs, ty, snip);
2116 diag.span_suggestion(
2118 "try dereferencing it",
2119 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
2120 Applicability::MaybeIncorrect,
2122 diag.span_suggestion(
2124 "or try being explicit if you are sure, that you want to clone a reference",
2126 Applicability::MaybeIncorrect,
2131 return; // don't report clone_on_copy
2135 if is_copy(cx, ty) {
2137 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
2138 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
2139 match &cx.tcx.hir().get(parent) {
2140 hir::Node::Expr(parent) => match parent.kind {
2141 // &*x is a nop, &x.clone() is not
2142 hir::ExprKind::AddrOf(..) => return,
2143 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
2144 hir::ExprKind::MethodCall(_, _, parent_args, _) if expr.hir_id == parent_args[0].hir_id => {
2150 hir::Node::Stmt(stmt) => {
2151 if let hir::StmtKind::Local(ref loc) = stmt.kind {
2152 if let hir::PatKind::Ref(..) = loc.pat.kind {
2153 // let ref y = *x borrows x, let ref y = x.clone() does not
2161 // x.clone() might have dereferenced x, possibly through Deref impls
2162 if cx.typeck_results().expr_ty(arg) == ty {
2163 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
2165 let deref_count = cx
2167 .expr_adjustments(arg)
2169 .filter(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(_)))
2171 let derefs: String = iter::repeat('*').take(deref_count).collect();
2172 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
2177 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |diag| {
2178 if let Some((text, snip)) = snip {
2179 diag.span_suggestion(expr.span, text, snip, Applicability::MachineApplicable);
2185 fn lint_clone_on_ref_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
2186 let obj_ty = cx.typeck_results().expr_ty(arg).peel_refs();
2188 if let ty::Adt(_, subst) = obj_ty.kind() {
2189 let caller_type = if is_type_diagnostic_item(cx, obj_ty, sym::Rc) {
2191 } else if is_type_diagnostic_item(cx, obj_ty, sym::Arc) {
2193 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
2199 let snippet = snippet_with_macro_callsite(cx, arg.span, "..");
2205 "using `.clone()` on a ref-counted pointer",
2207 format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet),
2208 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
2213 fn lint_string_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2215 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
2216 let target = &arglists[0][0];
2217 let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
2218 let ref_str = if *self_ty.kind() == ty::Str {
2220 } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
2226 let mut applicability = Applicability::MachineApplicable;
2229 STRING_EXTEND_CHARS,
2231 "calling `.extend(_.chars())`",
2234 "{}.push_str({}{})",
2235 snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
2237 snippet_with_applicability(cx, target.span, "..", &mut applicability)
2244 fn lint_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2245 let obj_ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
2246 if is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
2247 lint_string_extend(cx, expr, args);
2251 fn lint_iter_cloned_collect<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2253 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::vec_type);
2254 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0]));
2255 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite());
2260 ITER_CLONED_COLLECT,
2262 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
2265 ".to_vec()".to_string(),
2266 Applicability::MachineApplicable,
2272 fn lint_unnecessary_fold(cx: &LateContext<'_>, expr: &hir::Expr<'_>, fold_args: &[hir::Expr<'_>], fold_span: Span) {
2273 fn check_fold_with_op(
2274 cx: &LateContext<'_>,
2275 expr: &hir::Expr<'_>,
2276 fold_args: &[hir::Expr<'_>],
2279 replacement_method_name: &str,
2280 replacement_has_args: bool,
2283 // Extract the body of the closure passed to fold
2284 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].kind;
2285 let closure_body = cx.tcx.hir().body(body_id);
2286 let closure_expr = remove_blocks(&closure_body.value);
2288 // Check if the closure body is of the form `acc <op> some_expr(x)`
2289 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.kind;
2290 if bin_op.node == op;
2292 // Extract the names of the two arguments to the closure
2293 if let Some(first_arg_ident) = get_arg_name(&closure_body.params[0].pat);
2294 if let Some(second_arg_ident) = get_arg_name(&closure_body.params[1].pat);
2296 if match_var(&*left_expr, first_arg_ident);
2297 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
2300 let mut applicability = Applicability::MachineApplicable;
2301 let sugg = if replacement_has_args {
2303 "{replacement}(|{s}| {r})",
2304 replacement = replacement_method_name,
2305 s = second_arg_ident,
2306 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
2311 replacement = replacement_method_name,
2318 fold_span.with_hi(expr.span.hi()),
2319 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
2320 "this `.fold` can be written more succinctly using another method",
2329 // Check that this is a call to Iterator::fold rather than just some function called fold
2330 if !match_trait_method(cx, expr, &paths::ITERATOR) {
2335 fold_args.len() == 3,
2336 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
2339 // Check if the first argument to .fold is a suitable literal
2340 if let hir::ExprKind::Lit(ref lit) = fold_args[1].kind {
2342 ast::LitKind::Bool(false) => {
2343 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Or, "any", true)
2345 ast::LitKind::Bool(true) => {
2346 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::And, "all", true)
2348 ast::LitKind::Int(0, _) => {
2349 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Add, "sum", false)
2351 ast::LitKind::Int(1, _) => {
2352 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Mul, "product", false)
2359 fn lint_step_by<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, args: &'tcx [hir::Expr<'_>]) {
2360 if match_trait_method(cx, expr, &paths::ITERATOR) {
2361 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &args[1]) {
2364 ITERATOR_STEP_BY_ZERO,
2366 "Iterator::step_by(0) will panic at runtime",
2372 fn lint_iter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2373 let caller_expr = &iter_args[0];
2375 // Skip lint if the `iter().next()` expression is a for loop argument,
2376 // since it is already covered by `&loops::ITER_NEXT_LOOP`
2377 let mut parent_expr_opt = get_parent_expr(cx, expr);
2378 while let Some(parent_expr) = parent_expr_opt {
2379 if higher::for_loop(parent_expr).is_some() {
2382 parent_expr_opt = get_parent_expr(cx, parent_expr);
2385 if derefs_to_slice(cx, caller_expr, cx.typeck_results().expr_ty(caller_expr)).is_some() {
2386 // caller is a Slice
2388 if let hir::ExprKind::Index(ref caller_var, ref index_expr) = &caller_expr.kind;
2389 if let Some(higher::Range { start: Some(start_expr), end: None, limits: ast::RangeLimits::HalfOpen })
2390 = higher::range(index_expr);
2391 if let hir::ExprKind::Lit(ref start_lit) = &start_expr.kind;
2392 if let ast::LitKind::Int(start_idx, _) = start_lit.node;
2394 let mut applicability = Applicability::MachineApplicable;
2399 "using `.iter().next()` on a Slice without end index",
2401 format!("{}.get({})", snippet_with_applicability(cx, caller_var.span, "..", &mut applicability), start_idx),
2406 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(caller_expr), sym::vec_type)
2408 &cx.typeck_results().expr_ty(caller_expr).peel_refs().kind(),
2412 // caller is a Vec or an Array
2413 let mut applicability = Applicability::MachineApplicable;
2418 "using `.iter().next()` on an array",
2422 snippet_with_applicability(cx, caller_expr.span, "..", &mut applicability)
2429 fn lint_iter_nth<'tcx>(
2430 cx: &LateContext<'tcx>,
2431 expr: &hir::Expr<'_>,
2432 nth_and_iter_args: &[&'tcx [hir::Expr<'tcx>]],
2435 let iter_args = nth_and_iter_args[1];
2436 let mut_str = if is_mut { "_mut" } else { "" };
2437 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0])).is_some() {
2439 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym::vec_type) {
2441 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym!(vecdeque_type)) {
2444 let nth_args = nth_and_iter_args[0];
2445 lint_iter_nth_zero(cx, expr, &nth_args);
2446 return; // caller is not a type that we want to lint
2453 &format!("called `.iter{0}().nth()` on a {1}", mut_str, caller_type),
2455 &format!("calling `.get{}()` is both faster and more readable", mut_str),
2459 fn lint_iter_nth_zero<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
2461 if match_trait_method(cx, expr, &paths::ITERATOR);
2462 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &nth_args[1]);
2464 let mut applicability = Applicability::MachineApplicable;
2469 "called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
2470 "try calling `.next()` instead of `.nth(0)`",
2471 format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
2478 fn lint_get_unwrap<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, get_args: &'tcx [hir::Expr<'_>], is_mut: bool) {
2479 // Note: we don't want to lint `get_mut().unwrap` for `HashMap` or `BTreeMap`,
2480 // because they do not implement `IndexMut`
2481 let mut applicability = Applicability::MachineApplicable;
2482 let expr_ty = cx.typeck_results().expr_ty(&get_args[0]);
2483 let get_args_str = if get_args.len() > 1 {
2484 snippet_with_applicability(cx, get_args[1].span, "..", &mut applicability)
2486 return; // not linting on a .get().unwrap() chain or variant
2489 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
2490 needs_ref = get_args_str.parse::<usize>().is_ok();
2492 } else if is_type_diagnostic_item(cx, expr_ty, sym::vec_type) {
2493 needs_ref = get_args_str.parse::<usize>().is_ok();
2495 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vecdeque_type)) {
2496 needs_ref = get_args_str.parse::<usize>().is_ok();
2498 } else if !is_mut && is_type_diagnostic_item(cx, expr_ty, sym!(hashmap_type)) {
2501 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
2505 return; // caller is not a type that we want to lint
2508 let mut span = expr.span;
2510 // Handle the case where the result is immediately dereferenced
2511 // by not requiring ref and pulling the dereference into the
2515 if let Some(parent) = get_parent_expr(cx, expr);
2516 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.kind;
2523 let mut_str = if is_mut { "_mut" } else { "" };
2524 let borrow_str = if !needs_ref {
2537 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
2538 mut_str, caller_type
2544 snippet_with_applicability(cx, get_args[0].span, "..", &mut applicability),
2551 fn lint_iter_skip_next(cx: &LateContext<'_>, expr: &hir::Expr<'_>, skip_args: &[hir::Expr<'_>]) {
2552 // lint if caller of skip is an Iterator
2553 if match_trait_method(cx, expr, &paths::ITERATOR) {
2554 if let [caller, n] = skip_args {
2555 let hint = format!(".nth({})", snippet(cx, n.span, ".."));
2559 expr.span.trim_start(caller.span).unwrap(),
2560 "called `skip(..).next()` on an iterator",
2561 "use `nth` instead",
2563 Applicability::MachineApplicable,
2569 fn derefs_to_slice<'tcx>(
2570 cx: &LateContext<'tcx>,
2571 expr: &'tcx hir::Expr<'tcx>,
2573 ) -> Option<&'tcx hir::Expr<'tcx>> {
2574 fn may_slice<'a>(cx: &LateContext<'a>, ty: Ty<'a>) -> bool {
2576 ty::Slice(_) => true,
2577 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
2578 ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym::vec_type),
2579 ty::Array(_, size) => size
2580 .try_eval_usize(cx.tcx, cx.param_env)
2581 .map_or(false, |size| size < 32),
2582 ty::Ref(_, inner, _) => may_slice(cx, inner),
2587 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind {
2588 if path.ident.name == sym::iter && may_slice(cx, cx.typeck_results().expr_ty(&args[0])) {
2595 ty::Slice(_) => Some(expr),
2596 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
2597 ty::Ref(_, inner, _) => {
2598 if may_slice(cx, inner) {
2609 /// lint use of `unwrap()` for `Option`s and `Result`s
2610 fn lint_unwrap(cx: &LateContext<'_>, expr: &hir::Expr<'_>, unwrap_args: &[hir::Expr<'_>]) {
2611 let obj_ty = cx.typeck_results().expr_ty(&unwrap_args[0]).peel_refs();
2613 let mess = if is_type_diagnostic_item(cx, obj_ty, sym::option_type) {
2614 Some((UNWRAP_USED, "an Option", "None"))
2615 } else if is_type_diagnostic_item(cx, obj_ty, sym::result_type) {
2616 Some((UNWRAP_USED, "a Result", "Err"))
2621 if let Some((lint, kind, none_value)) = mess {
2626 &format!("used `unwrap()` on `{}` value", kind,),
2629 "if you don't want to handle the `{}` case gracefully, consider \
2630 using `expect()` to provide a better panic message",
2637 /// lint use of `expect()` for `Option`s and `Result`s
2638 fn lint_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, expect_args: &[hir::Expr<'_>]) {
2639 let obj_ty = cx.typeck_results().expr_ty(&expect_args[0]).peel_refs();
2641 let mess = if is_type_diagnostic_item(cx, obj_ty, sym!(option_type)) {
2642 Some((EXPECT_USED, "an Option", "None"))
2643 } else if is_type_diagnostic_item(cx, obj_ty, sym!(result_type)) {
2644 Some((EXPECT_USED, "a Result", "Err"))
2649 if let Some((lint, kind, none_value)) = mess {
2654 &format!("used `expect()` on `{}` value", kind,),
2656 &format!("if this value is an `{}`, it will panic", none_value,),
2661 /// lint use of `ok().expect()` for `Result`s
2662 fn lint_ok_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
2664 // lint if the caller of `ok()` is a `Result`
2665 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&ok_args[0]), sym::result_type);
2666 let result_type = cx.typeck_results().expr_ty(&ok_args[0]);
2667 if let Some(error_type) = get_error_type(cx, result_type);
2668 if has_debug_impl(error_type, cx);
2675 "called `ok().expect()` on a `Result` value",
2677 "you can call `expect()` directly on the `Result`",
2683 /// lint use of `map().flatten()` for `Iterators` and 'Options'
2684 fn lint_map_flatten<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) {
2685 // lint if caller of `.map().flatten()` is an Iterator
2686 if match_trait_method(cx, expr, &paths::ITERATOR) {
2687 let map_closure_ty = cx.typeck_results().expr_ty(&map_args[1]);
2688 let is_map_to_option = match map_closure_ty.kind() {
2689 ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
2690 let map_closure_sig = match map_closure_ty.kind() {
2691 ty::Closure(_, substs) => substs.as_closure().sig(),
2692 _ => map_closure_ty.fn_sig(cx.tcx),
2694 let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
2695 is_type_diagnostic_item(cx, map_closure_return_ty, sym::option_type)
2700 let method_to_use = if is_map_to_option {
2701 // `(...).map(...)` has type `impl Iterator<Item=Option<...>>
2704 // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
2707 let func_snippet = snippet(cx, map_args[1].span, "..");
2708 let hint = format!(".{0}({1})", method_to_use, func_snippet);
2712 expr.span.with_lo(map_args[0].span.hi()),
2713 "called `map(..).flatten()` on an `Iterator`",
2714 &format!("try using `{}` instead", method_to_use),
2716 Applicability::MachineApplicable,
2720 // lint if caller of `.map().flatten()` is an Option
2721 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::option_type) {
2722 let func_snippet = snippet(cx, map_args[1].span, "..");
2723 let hint = format!(".and_then({})", func_snippet);
2727 expr.span.with_lo(map_args[0].span.hi()),
2728 "called `map(..).flatten()` on an `Option`",
2729 "try using `and_then` instead",
2731 Applicability::MachineApplicable,
2736 const MAP_UNWRAP_OR_MSRV: RustcVersion = RustcVersion::new(1, 41, 0);
2738 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
2739 /// Return true if lint triggered
2740 fn lint_map_unwrap_or_else<'tcx>(
2741 cx: &LateContext<'tcx>,
2742 expr: &'tcx hir::Expr<'_>,
2743 map_args: &'tcx [hir::Expr<'_>],
2744 unwrap_args: &'tcx [hir::Expr<'_>],
2745 msrv: Option<&RustcVersion>,
2747 if !meets_msrv(msrv, &MAP_UNWRAP_OR_MSRV) {
2750 // lint if the caller of `map()` is an `Option`
2751 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::option_type);
2752 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym::result_type);
2754 if is_option || is_result {
2755 // Don't make a suggestion that may fail to compile due to mutably borrowing
2756 // the same variable twice.
2757 let map_mutated_vars = mutated_variables(&map_args[0], cx);
2758 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
2759 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
2760 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
2768 let msg = if is_option {
2769 "called `map(<f>).unwrap_or_else(<g>)` on an `Option` value. This can be done more directly by calling \
2770 `map_or_else(<g>, <f>)` instead"
2772 "called `map(<f>).unwrap_or_else(<g>)` on a `Result` value. This can be done more directly by calling \
2773 `.map_or_else(<g>, <f>)` instead"
2775 // get snippets for args to map() and unwrap_or_else()
2776 let map_snippet = snippet(cx, map_args[1].span, "..");
2777 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
2778 // lint, with note if neither arg is > 1 line and both map() and
2779 // unwrap_or_else() have the same span
2780 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
2781 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
2782 if same_span && !multiline {
2783 let var_snippet = snippet(cx, map_args[0].span, "..");
2790 format!("{}.map_or_else({}, {})", var_snippet, unwrap_snippet, map_snippet),
2791 Applicability::MachineApplicable,
2794 } else if same_span && multiline {
2795 span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
2803 /// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
2804 fn lint_map_or_none<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_or_args: &'tcx [hir::Expr<'_>]) {
2805 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::option_type);
2806 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::result_type);
2808 // There are two variants of this `map_or` lint:
2809 // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
2810 // (2) using `map_or` as a combinator instead of `and_then`
2812 // (For this lint) we don't care if any other type calls `map_or`
2813 if !is_option && !is_result {
2817 let (lint_name, msg, instead, hint) = {
2818 let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
2819 match_qpath(qpath, &paths::OPTION_NONE)
2824 if !default_arg_is_none {
2829 let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
2830 match_qpath(qpath, &paths::OPTION_SOME)
2836 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2837 let func_snippet = snippet(cx, map_or_args[2].span, "..");
2838 let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
2839 `and_then(..)` instead";
2843 "try using `and_then` instead",
2844 format!("{0}.and_then({1})", self_snippet, func_snippet),
2846 } else if f_arg_is_some {
2847 let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
2849 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2851 RESULT_MAP_OR_INTO_OPTION,
2853 "try using `ok` instead",
2854 format!("{0}.ok()", self_snippet),
2869 Applicability::MachineApplicable,
2873 /// lint use of `filter().next()` for `Iterators`
2874 fn lint_filter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
2875 // lint if caller of `.filter().next()` is an Iterator
2876 if match_trait_method(cx, expr, &paths::ITERATOR) {
2877 let msg = "called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
2878 `.find(..)` instead.";
2879 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2880 if filter_snippet.lines().count() <= 1 {
2881 let iter_snippet = snippet(cx, filter_args[0].span, "..");
2882 // add note if not multi-line
2889 format!("{}.find({})", iter_snippet, filter_snippet),
2890 Applicability::MachineApplicable,
2893 span_lint(cx, FILTER_NEXT, expr.span, msg);
2898 /// lint use of `skip_while().next()` for `Iterators`
2899 fn lint_skip_while_next<'tcx>(
2900 cx: &LateContext<'tcx>,
2901 expr: &'tcx hir::Expr<'_>,
2902 _skip_while_args: &'tcx [hir::Expr<'_>],
2904 // lint if caller of `.skip_while().next()` is an Iterator
2905 if match_trait_method(cx, expr, &paths::ITERATOR) {
2910 "called `skip_while(<p>).next()` on an `Iterator`",
2912 "this is more succinctly expressed by calling `.find(!<p>)` instead",
2917 /// lint use of `filter().map()` for `Iterators`
2918 fn lint_filter_map<'tcx>(
2919 cx: &LateContext<'tcx>,
2920 expr: &'tcx hir::Expr<'_>,
2921 _filter_args: &'tcx [hir::Expr<'_>],
2922 _map_args: &'tcx [hir::Expr<'_>],
2924 // lint if caller of `.filter().map()` is an Iterator
2925 if match_trait_method(cx, expr, &paths::ITERATOR) {
2926 let msg = "called `filter(..).map(..)` on an `Iterator`";
2927 let hint = "this is more succinctly expressed by calling `.filter_map(..)` instead";
2928 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2932 const FILTER_MAP_NEXT_MSRV: RustcVersion = RustcVersion::new(1, 30, 0);
2934 /// lint use of `filter_map().next()` for `Iterators`
2935 fn lint_filter_map_next<'tcx>(
2936 cx: &LateContext<'tcx>,
2937 expr: &'tcx hir::Expr<'_>,
2938 filter_args: &'tcx [hir::Expr<'_>],
2939 msrv: Option<&RustcVersion>,
2941 if match_trait_method(cx, expr, &paths::ITERATOR) {
2942 if !meets_msrv(msrv, &FILTER_MAP_NEXT_MSRV) {
2946 let msg = "called `filter_map(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
2947 `.find_map(..)` instead.";
2948 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2949 if filter_snippet.lines().count() <= 1 {
2950 let iter_snippet = snippet(cx, filter_args[0].span, "..");
2957 format!("{}.find_map({})", iter_snippet, filter_snippet),
2958 Applicability::MachineApplicable,
2961 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2966 /// lint use of `find().map()` for `Iterators`
2967 fn lint_find_map<'tcx>(
2968 cx: &LateContext<'tcx>,
2969 expr: &'tcx hir::Expr<'_>,
2970 _find_args: &'tcx [hir::Expr<'_>],
2971 map_args: &'tcx [hir::Expr<'_>],
2973 // lint if caller of `.filter().map()` is an Iterator
2974 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2975 let msg = "called `find(..).map(..)` on an `Iterator`";
2976 let hint = "this is more succinctly expressed by calling `.find_map(..)` instead";
2977 span_lint_and_help(cx, FIND_MAP, expr.span, msg, None, hint);
2981 /// lint use of `filter_map().map()` for `Iterators`
2982 fn lint_filter_map_map<'tcx>(
2983 cx: &LateContext<'tcx>,
2984 expr: &'tcx hir::Expr<'_>,
2985 _filter_args: &'tcx [hir::Expr<'_>],
2986 _map_args: &'tcx [hir::Expr<'_>],
2988 // lint if caller of `.filter().map()` is an Iterator
2989 if match_trait_method(cx, expr, &paths::ITERATOR) {
2990 let msg = "called `filter_map(..).map(..)` on an `Iterator`";
2991 let hint = "this is more succinctly expressed by only calling `.filter_map(..)` instead";
2992 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2996 /// lint use of `filter().flat_map()` for `Iterators`
2997 fn lint_filter_flat_map<'tcx>(
2998 cx: &LateContext<'tcx>,
2999 expr: &'tcx hir::Expr<'_>,
3000 _filter_args: &'tcx [hir::Expr<'_>],
3001 _map_args: &'tcx [hir::Expr<'_>],
3003 // lint if caller of `.filter().flat_map()` is an Iterator
3004 if match_trait_method(cx, expr, &paths::ITERATOR) {
3005 let msg = "called `filter(..).flat_map(..)` on an `Iterator`";
3006 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
3007 and filtering by returning `iter::empty()`";
3008 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3012 /// lint use of `filter_map().flat_map()` for `Iterators`
3013 fn lint_filter_map_flat_map<'tcx>(
3014 cx: &LateContext<'tcx>,
3015 expr: &'tcx hir::Expr<'_>,
3016 _filter_args: &'tcx [hir::Expr<'_>],
3017 _map_args: &'tcx [hir::Expr<'_>],
3019 // lint if caller of `.filter_map().flat_map()` is an Iterator
3020 if match_trait_method(cx, expr, &paths::ITERATOR) {
3021 let msg = "called `filter_map(..).flat_map(..)` on an `Iterator`";
3022 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
3023 and filtering by returning `iter::empty()`";
3024 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3028 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
3029 fn lint_flat_map_identity<'tcx>(
3030 cx: &LateContext<'tcx>,
3031 expr: &'tcx hir::Expr<'_>,
3032 flat_map_args: &'tcx [hir::Expr<'_>],
3033 flat_map_span: Span,
3035 if match_trait_method(cx, expr, &paths::ITERATOR) {
3036 let arg_node = &flat_map_args[1].kind;
3038 let apply_lint = |message: &str| {
3042 flat_map_span.with_hi(expr.span.hi()),
3045 "flatten()".to_string(),
3046 Applicability::MachineApplicable,
3051 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
3052 let body = cx.tcx.hir().body(*body_id);
3054 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
3055 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
3057 if path.segments.len() == 1;
3058 if path.segments[0].ident.as_str() == binding_ident.as_str();
3061 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
3066 if let hir::ExprKind::Path(ref qpath) = arg_node;
3068 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
3071 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
3077 /// lint searching an Iterator followed by `is_some()`
3078 /// or calling `find()` on a string followed by `is_some()`
3079 fn lint_search_is_some<'tcx>(
3080 cx: &LateContext<'tcx>,
3081 expr: &'tcx hir::Expr<'_>,
3082 search_method: &str,
3083 search_args: &'tcx [hir::Expr<'_>],
3084 is_some_args: &'tcx [hir::Expr<'_>],
3087 // lint if caller of search is an Iterator
3088 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
3090 "called `is_some()` after searching an `Iterator` with `{}`",
3093 let hint = "this is more succinctly expressed by calling `any()`";
3094 let search_snippet = snippet(cx, search_args[1].span, "..");
3095 if search_snippet.lines().count() <= 1 {
3096 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
3097 // suggest `any(|..| *..)` instead of `any(|..| **..)` for `find(|..| **..).is_some()`
3098 let any_search_snippet = if_chain! {
3099 if search_method == "find";
3100 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].kind;
3101 let closure_body = cx.tcx.hir().body(body_id);
3102 if let Some(closure_arg) = closure_body.params.get(0);
3104 if let hir::PatKind::Ref(..) = closure_arg.pat.kind {
3105 Some(search_snippet.replacen('&', "", 1))
3106 } else if let Some(name) = get_arg_name(&closure_arg.pat) {
3107 Some(search_snippet.replace(&format!("*{}", name), &name.as_str()))
3115 // add note if not multi-line
3119 method_span.with_hi(expr.span.hi()),
3121 "use `any()` instead",
3124 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
3126 Applicability::MachineApplicable,
3129 span_lint_and_help(cx, SEARCH_IS_SOME, expr.span, &msg, None, hint);
3132 // lint if `find()` is called by `String` or `&str`
3133 else if search_method == "find" {
3134 let is_string_or_str_slice = |e| {
3135 let self_ty = cx.typeck_results().expr_ty(e).peel_refs();
3136 if is_type_diagnostic_item(cx, self_ty, sym!(string_type)) {
3139 *self_ty.kind() == ty::Str
3143 if is_string_or_str_slice(&search_args[0]);
3144 if is_string_or_str_slice(&search_args[1]);
3146 let msg = "called `is_some()` after calling `find()` on a string";
3147 let mut applicability = Applicability::MachineApplicable;
3148 let find_arg = snippet_with_applicability(cx, search_args[1].span, "..", &mut applicability);
3152 method_span.with_hi(expr.span.hi()),
3154 "use `contains()` instead",
3155 format!("contains({})", find_arg),
3163 /// Used for `lint_binary_expr_with_method_call`.
3164 #[derive(Copy, Clone)]
3165 struct BinaryExprInfo<'a> {
3166 expr: &'a hir::Expr<'a>,
3167 chain: &'a hir::Expr<'a>,
3168 other: &'a hir::Expr<'a>,
3172 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3173 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
3174 macro_rules! lint_with_both_lhs_and_rhs {
3175 ($func:ident, $cx:expr, $info:ident) => {
3176 if !$func($cx, $info) {
3177 ::std::mem::swap(&mut $info.chain, &mut $info.other);
3178 if $func($cx, $info) {
3185 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
3186 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
3187 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
3188 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
3191 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3193 cx: &LateContext<'_>,
3194 info: &BinaryExprInfo<'_>,
3195 chain_methods: &[&str],
3196 lint: &'static Lint,
3200 if let Some(args) = method_chain_args(info.chain, chain_methods);
3201 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
3202 if arg_char.len() == 1;
3203 if let hir::ExprKind::Path(ref qpath) = fun.kind;
3204 if let Some(segment) = single_segment_path(qpath);
3205 if segment.ident.name == sym::Some;
3207 let mut applicability = Applicability::MachineApplicable;
3208 let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0][0]).peel_refs();
3210 if *self_ty.kind() != ty::Str {
3218 &format!("you should use the `{}` method", suggest),
3220 format!("{}{}.{}({})",
3221 if info.eq { "" } else { "!" },
3222 snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
3224 snippet_with_applicability(cx, arg_char[0].span, "..", &mut applicability)),
3235 /// Checks for the `CHARS_NEXT_CMP` lint.
3236 fn lint_chars_next_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3237 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
3240 /// Checks for the `CHARS_LAST_CMP` lint.
3241 fn lint_chars_last_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3242 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
3245 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
3249 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
3250 fn lint_chars_cmp_with_unwrap<'tcx>(
3251 cx: &LateContext<'tcx>,
3252 info: &BinaryExprInfo<'_>,
3253 chain_methods: &[&str],
3254 lint: &'static Lint,
3258 if let Some(args) = method_chain_args(info.chain, chain_methods);
3259 if let hir::ExprKind::Lit(ref lit) = info.other.kind;
3260 if let ast::LitKind::Char(c) = lit.node;
3262 let mut applicability = Applicability::MachineApplicable;
3267 &format!("you should use the `{}` method", suggest),
3269 format!("{}{}.{}('{}')",
3270 if info.eq { "" } else { "!" },
3271 snippet_with_applicability(cx, args[0][0].span, "..", &mut applicability),
3284 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
3285 fn lint_chars_next_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3286 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
3289 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
3290 fn lint_chars_last_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3291 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
3294 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
3298 fn get_hint_if_single_char_arg(
3299 cx: &LateContext<'_>,
3300 arg: &hir::Expr<'_>,
3301 applicability: &mut Applicability,
3302 ) -> Option<String> {
3304 if let hir::ExprKind::Lit(lit) = &arg.kind;
3305 if let ast::LitKind::Str(r, style) = lit.node;
3306 let string = r.as_str();
3307 if string.chars().count() == 1;
3309 let snip = snippet_with_applicability(cx, arg.span, &string, applicability);
3310 let ch = if let ast::StrStyle::Raw(nhash) = style {
3311 let nhash = nhash as usize;
3312 // for raw string: r##"a"##
3313 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
3315 // for regular string: "a"
3316 &snip[1..(snip.len() - 1)]
3318 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
3326 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
3327 fn lint_single_char_pattern(cx: &LateContext<'_>, _expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
3328 let mut applicability = Applicability::MachineApplicable;
3329 if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability) {
3332 SINGLE_CHAR_PATTERN,
3334 "single-character string constant used as pattern",
3335 "try using a `char` instead",
3342 /// lint for length-1 `str`s as argument for `push_str`
3343 fn lint_single_char_push_string(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3344 let mut applicability = Applicability::MachineApplicable;
3345 if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[1], &mut applicability) {
3346 let base_string_snippet =
3347 snippet_with_applicability(cx, args[0].span.source_callsite(), "..", &mut applicability);
3348 let sugg = format!("{}.push({})", base_string_snippet, extension_string);
3351 SINGLE_CHAR_ADD_STR,
3353 "calling `push_str()` using a single-character string literal",
3354 "consider using `push` with a character literal",
3361 /// lint for length-1 `str`s as argument for `insert_str`
3362 fn lint_single_char_insert_string(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3363 let mut applicability = Applicability::MachineApplicable;
3364 if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[2], &mut applicability) {
3365 let base_string_snippet =
3366 snippet_with_applicability(cx, args[0].span.source_callsite(), "_", &mut applicability);
3367 let pos_arg = snippet_with_applicability(cx, args[1].span, "..", &mut applicability);
3368 let sugg = format!("{}.insert({}, {})", base_string_snippet, pos_arg, extension_string);
3371 SINGLE_CHAR_ADD_STR,
3373 "calling `insert_str()` using a single-character string literal",
3374 "consider using `insert` with a character literal",
3381 /// Checks for the `USELESS_ASREF` lint.
3382 fn lint_asref(cx: &LateContext<'_>, expr: &hir::Expr<'_>, call_name: &str, as_ref_args: &[hir::Expr<'_>]) {
3383 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
3384 // check if the call is to the actual `AsRef` or `AsMut` trait
3385 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
3386 // check if the type after `as_ref` or `as_mut` is the same as before
3387 let recvr = &as_ref_args[0];
3388 let rcv_ty = cx.typeck_results().expr_ty(recvr);
3389 let res_ty = cx.typeck_results().expr_ty(expr);
3390 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
3391 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
3392 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
3393 // allow the `as_ref` or `as_mut` if it is followed by another method call
3395 if let Some(parent) = get_parent_expr(cx, expr);
3396 if let hir::ExprKind::MethodCall(_, ref span, _, _) = parent.kind;
3397 if span != &expr.span;
3403 let mut applicability = Applicability::MachineApplicable;
3408 &format!("this call to `{}` does nothing", call_name),
3410 snippet_with_applicability(cx, recvr.span, "..", &mut applicability).to_string(),
3417 fn ty_has_iter_method(cx: &LateContext<'_>, self_ref_ty: Ty<'_>) -> Option<(&'static str, &'static str)> {
3418 has_iter_method(cx, self_ref_ty).map(|ty_name| {
3419 let mutbl = match self_ref_ty.kind() {
3420 ty::Ref(_, _, mutbl) => mutbl,
3421 _ => unreachable!(),
3423 let method_name = match mutbl {
3424 hir::Mutability::Not => "iter",
3425 hir::Mutability::Mut => "iter_mut",
3427 (ty_name, method_name)
3431 fn lint_into_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, self_ref_ty: Ty<'_>, method_span: Span) {
3432 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
3435 if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
3441 "this `.into_iter()` call is equivalent to `.{}()` and will not consume the `{}`",
3445 method_name.to_string(),
3446 Applicability::MachineApplicable,
3451 /// lint for `MaybeUninit::uninit().assume_init()` (we already have the latter)
3452 fn lint_maybe_uninit(cx: &LateContext<'_>, expr: &hir::Expr<'_>, outer: &hir::Expr<'_>) {
3454 if let hir::ExprKind::Call(ref callee, ref args) = expr.kind;
3456 if let hir::ExprKind::Path(ref path) = callee.kind;
3457 if match_qpath(path, &paths::MEM_MAYBEUNINIT_UNINIT);
3458 if !is_maybe_uninit_ty_valid(cx, cx.typeck_results().expr_ty_adjusted(outer));
3462 UNINIT_ASSUMED_INIT,
3464 "this call for this type may be undefined behavior"
3470 fn is_maybe_uninit_ty_valid(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
3472 ty::Array(ref component, _) => is_maybe_uninit_ty_valid(cx, component),
3473 ty::Tuple(ref types) => types.types().all(|ty| is_maybe_uninit_ty_valid(cx, ty)),
3474 ty::Adt(ref adt, _) => match_def_path(cx, adt.did, &paths::MEM_MAYBEUNINIT),
3479 fn lint_suspicious_map(cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
3484 "this call to `map()` won't have an effect on the call to `count()`",
3486 "make sure you did not confuse `map` with `filter` or `for_each`",
3490 const OPTION_AS_REF_DEREF_MSRV: RustcVersion = RustcVersion::new(1, 40, 0);
3492 /// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
3493 fn lint_option_as_ref_deref<'tcx>(
3494 cx: &LateContext<'tcx>,
3495 expr: &hir::Expr<'_>,
3496 as_ref_args: &[hir::Expr<'_>],
3497 map_args: &[hir::Expr<'_>],
3499 msrv: Option<&RustcVersion>,
3501 if !meets_msrv(msrv, &OPTION_AS_REF_DEREF_MSRV) {
3505 let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
3507 let option_ty = cx.typeck_results().expr_ty(&as_ref_args[0]);
3508 if !is_type_diagnostic_item(cx, option_ty, sym::option_type) {
3512 let deref_aliases: [&[&str]; 9] = [
3513 &paths::DEREF_TRAIT_METHOD,
3514 &paths::DEREF_MUT_TRAIT_METHOD,
3515 &paths::CSTRING_AS_C_STR,
3516 &paths::OS_STRING_AS_OS_STR,
3517 &paths::PATH_BUF_AS_PATH,
3518 &paths::STRING_AS_STR,
3519 &paths::STRING_AS_MUT_STR,
3520 &paths::VEC_AS_SLICE,
3521 &paths::VEC_AS_MUT_SLICE,
3524 let is_deref = match map_args[1].kind {
3525 hir::ExprKind::Path(ref expr_qpath) => cx
3526 .qpath_res(expr_qpath, map_args[1].hir_id)
3528 .map_or(false, |fun_def_id| {
3529 deref_aliases.iter().any(|path| match_def_path(cx, fun_def_id, path))
3531 hir::ExprKind::Closure(_, _, body_id, _, _) => {
3532 let closure_body = cx.tcx.hir().body(body_id);
3533 let closure_expr = remove_blocks(&closure_body.value);
3535 match &closure_expr.kind {
3536 hir::ExprKind::MethodCall(_, _, args, _) => {
3539 if let hir::ExprKind::Path(qpath) = &args[0].kind;
3540 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, args[0].hir_id);
3541 if closure_body.params[0].pat.hir_id == local_id;
3544 .expr_adjustments(&args[0])
3547 .collect::<Box<[_]>>();
3548 if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
3550 let method_did = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id).unwrap();
3551 deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
3557 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, ref inner) if same_mutability(m) => {
3559 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner1) = inner.kind;
3560 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner2) = inner1.kind;
3561 if let hir::ExprKind::Path(ref qpath) = inner2.kind;
3562 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, inner2.hir_id);
3564 closure_body.params[0].pat.hir_id == local_id
3577 let current_method = if is_mut {
3578 format!(".as_mut().map({})", snippet(cx, map_args[1].span, ".."))
3580 format!(".as_ref().map({})", snippet(cx, map_args[1].span, ".."))
3582 let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
3583 let hint = format!("{}.{}()", snippet(cx, as_ref_args[0].span, ".."), method_hint);
3584 let suggestion = format!("try using {} instead", method_hint);
3587 "called `{0}` on an Option value. This can be done more directly \
3588 by calling `{1}` instead",
3589 current_method, hint
3593 OPTION_AS_REF_DEREF,
3598 Applicability::MachineApplicable,
3603 fn lint_map_collect(
3604 cx: &LateContext<'_>,
3605 expr: &hir::Expr<'_>,
3606 map_args: &[hir::Expr<'_>],
3607 collect_args: &[hir::Expr<'_>],
3610 // called on Iterator
3611 if let [map_expr] = collect_args;
3612 if match_trait_method(cx, map_expr, &paths::ITERATOR);
3613 // return of collect `Result<(),_>`
3614 let collect_ret_ty = cx.typeck_results().expr_ty(expr);
3615 if is_type_diagnostic_item(cx, collect_ret_ty, sym::result_type);
3616 if let ty::Adt(_, substs) = collect_ret_ty.kind();
3617 if let Some(result_t) = substs.types().next();
3618 if result_t.is_unit();
3619 // get parts for snippet
3620 if let [iter, map_fn] = map_args;
3624 MAP_COLLECT_RESULT_UNIT,
3626 "`.map().collect()` can be replaced with `.try_for_each()`",
3629 "{}.try_for_each({})",
3630 snippet(cx, iter.span, ".."),
3631 snippet(cx, map_fn.span, "..")
3633 Applicability::MachineApplicable,
3639 /// Given a `Result<T, E>` type, return its error type (`E`).
3640 fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
3642 ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::result_type) => substs.types().nth(1),
3647 /// This checks whether a given type is known to implement Debug.
3648 fn has_debug_impl<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool {
3650 .get_diagnostic_item(sym::debug_trait)
3651 .map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
3656 StartsWith(&'static str),
3660 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
3661 (Convention::Eq("new"), &[SelfKind::No]),
3662 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
3663 (Convention::StartsWith("from_"), &[SelfKind::No]),
3664 (Convention::StartsWith("into_"), &[SelfKind::Value]),
3665 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
3666 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
3667 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
3670 const FN_HEADER: hir::FnHeader = hir::FnHeader {
3671 unsafety: hir::Unsafety::Normal,
3672 constness: hir::Constness::NotConst,
3673 asyncness: hir::IsAsync::NotAsync,
3674 abi: rustc_target::spec::abi::Abi::Rust,
3677 struct ShouldImplTraitCase {
3678 trait_name: &'static str,
3679 method_name: &'static str,
3681 fn_header: hir::FnHeader,
3682 // implicit self kind expected (none, self, &self, ...)
3683 self_kind: SelfKind,
3684 // checks against the output type
3685 output_type: OutType,
3686 // certain methods with explicit lifetimes can't implement the equivalent trait method
3687 lint_explicit_lifetime: bool,
3689 impl ShouldImplTraitCase {
3691 trait_name: &'static str,
3692 method_name: &'static str,
3694 fn_header: hir::FnHeader,
3695 self_kind: SelfKind,
3696 output_type: OutType,
3697 lint_explicit_lifetime: bool,
3698 ) -> ShouldImplTraitCase {
3699 ShouldImplTraitCase {
3706 lint_explicit_lifetime,
3710 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
3711 self.lint_explicit_lifetime
3712 || !impl_item.generics.params.iter().any(|p| {
3715 hir::GenericParamKind::Lifetime {
3716 kind: hir::LifetimeParamKind::Explicit
3724 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
3725 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3726 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3727 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3728 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3729 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3730 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3731 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3732 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3733 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3734 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3735 // FIXME: default doesn't work
3736 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
3737 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3738 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3739 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3740 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
3741 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
3742 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3743 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3744 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
3745 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3746 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3747 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3748 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3749 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3750 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
3751 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3752 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3753 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3754 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3755 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3759 const PATTERN_METHODS: [(&str, usize); 17] = [
3767 ("split_terminator", 1),
3768 ("rsplit_terminator", 1),
3773 ("match_indices", 1),
3774 ("rmatch_indices", 1),
3775 ("trim_start_matches", 1),
3776 ("trim_end_matches", 1),
3779 #[derive(Clone, Copy, PartialEq, Debug)]
3788 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3789 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
3790 if ty == parent_ty {
3792 } else if ty.is_box() {
3793 ty.boxed_ty() == parent_ty
3794 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
3795 if let ty::Adt(_, substs) = ty.kind() {
3796 substs.types().next().map_or(false, |t| t == parent_ty)
3805 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3806 if let ty::Ref(_, t, m) = *ty.kind() {
3807 return m == mutability && t == parent_ty;
3810 let trait_path = match mutability {
3811 hir::Mutability::Not => &paths::ASREF_TRAIT,
3812 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
3815 let trait_def_id = match get_trait_def_id(cx, trait_path) {
3817 None => return false,
3819 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3823 Self::Value => matches_value(cx, parent_ty, ty),
3824 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3825 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3826 Self::No => ty != parent_ty,
3831 fn description(self) -> &'static str {
3833 Self::Value => "self by value",
3834 Self::Ref => "self by reference",
3835 Self::RefMut => "self by mutable reference",
3836 Self::No => "no self",
3843 fn check(&self, other: &str) -> bool {
3845 Self::Eq(this) => this == other,
3846 Self::StartsWith(this) => other.starts_with(this) && this != other,
3851 impl fmt::Display for Convention {
3852 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
3854 Self::Eq(this) => this.fmt(f),
3855 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
3860 #[derive(Clone, Copy)]
3869 fn matches(self, cx: &LateContext<'_>, ty: &hir::FnRetTy<'_>) -> bool {
3870 let is_unit = |ty: &hir::Ty<'_>| SpanlessEq::new(cx).eq_ty_kind(&ty.kind, &hir::TyKind::Tup(&[]));
3872 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3873 (Self::Unit, &hir::FnRetTy::Return(ref ty)) if is_unit(ty) => true,
3874 (Self::Bool, &hir::FnRetTy::Return(ref ty)) if is_bool(ty) => true,
3875 (Self::Any, &hir::FnRetTy::Return(ref ty)) if !is_unit(ty) => true,
3876 (Self::Ref, &hir::FnRetTy::Return(ref ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3882 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3883 if let hir::TyKind::Path(ref p) = ty.kind {
3884 match_qpath(p, &["bool"])
3890 fn check_pointer_offset(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3893 if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.typeck_results().expr_ty(&args[0]).kind();
3894 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
3897 span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
3902 fn lint_filetype_is_file(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3903 let ty = cx.typeck_results().expr_ty(&args[0]);
3905 if !match_type(cx, ty, &paths::FILE_TYPE) {
3911 let lint_unary: &str;
3912 let help_unary: &str;
3914 if let Some(parent) = get_parent_expr(cx, expr);
3915 if let hir::ExprKind::Unary(op, _) = parent.kind;
3916 if op == hir::UnOp::UnNot;
3929 let lint_msg = format!("`{}FileType::is_file()` only {} regular files", lint_unary, verb);
3930 let help_msg = format!("use `{}FileType::is_dir()` instead", help_unary);
3931 span_lint_and_help(cx, FILETYPE_IS_FILE, span, &lint_msg, None, &help_msg);
3934 fn lint_from_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3935 let ty = cx.typeck_results().expr_ty(expr);
3936 let arg_ty = cx.typeck_results().expr_ty(&args[0]);
3939 if let Some(from_iter_id) = get_trait_def_id(cx, &paths::FROM_ITERATOR);
3940 if let Some(iter_id) = get_trait_def_id(cx, &paths::ITERATOR);
3942 if implements_trait(cx, ty, from_iter_id, &[]) && implements_trait(cx, arg_ty, iter_id, &[]);
3944 // `expr` implements `FromIterator` trait
3945 let iter_expr = snippet(cx, args[0].span, "..");
3948 FROM_ITER_INSTEAD_OF_COLLECT,
3950 "usage of `FromIterator::from_iter`",
3951 "use `.collect()` instead of `::from_iter()`",
3952 format!("{}.collect()", iter_expr),
3953 Applicability::MaybeIncorrect,
3959 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
3960 expected.constness == actual.constness
3961 && expected.unsafety == actual.unsafety
3962 && expected.asyncness == actual.asyncness