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::intravisit::{self, Visitor};
18 use rustc_hir::{TraitItem, TraitItemKind};
19 use rustc_lint::{LateContext, LateLintPass, Lint, LintContext};
20 use rustc_middle::hir::map::Map;
21 use rustc_middle::lint::in_external_macro;
22 use rustc_middle::ty::{self, TraitRef, Ty, TyS};
23 use rustc_session::{declare_lint_pass, declare_tool_lint};
24 use rustc_span::source_map::Span;
25 use rustc_span::symbol::{sym, SymbolStr};
27 use crate::consts::{constant, Constant};
28 use crate::utils::usage::mutated_variables;
30 contains_ty, get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait, in_macro,
31 is_copy, is_ctor_or_promotable_const_function, is_expn_of, is_type_diagnostic_item, iter_input_pats,
32 last_path_segment, match_def_path, match_qpath, match_trait_method, match_type, match_var, 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_note, span_lint_and_sugg,
35 span_lint_and_then, sugg, walk_ptrs_ty, 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 a
403 /// single method call using `_.flat_map(_)`
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 a
427 /// single method call.
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 a
455 /// single method call.
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 a
499 /// single method call.
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 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
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 search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
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 getting the inner pointer of a temporary
804 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
805 /// as the `CString` is alive.
807 /// **Known problems:** None.
811 /// # use std::ffi::CString;
812 /// # fn call_some_ffi_func(_: *const i8) {}
814 /// let c_str = CString::new("foo").unwrap().as_ptr();
816 /// call_some_ffi_func(c_str);
819 /// Here `c_str` points to a freed address. The correct use would be:
821 /// # use std::ffi::CString;
822 /// # fn call_some_ffi_func(_: *const i8) {}
824 /// let c_str = CString::new("foo").unwrap();
826 /// call_some_ffi_func(c_str.as_ptr());
829 pub TEMPORARY_CSTRING_AS_PTR,
831 "getting the inner pointer of a temporary `CString`"
834 declare_clippy_lint! {
835 /// **What it does:** Checks for calling `.step_by(0)` on iterators which panics.
837 /// **Why is this bad?** This very much looks like an oversight. Use `panic!()` instead if you
838 /// actually intend to panic.
840 /// **Known problems:** None.
843 /// ```rust,should_panic
844 /// for x in (0..100).step_by(0) {
848 pub ITERATOR_STEP_BY_ZERO,
850 "using `Iterator::step_by(0)`, which will panic at runtime"
853 declare_clippy_lint! {
854 /// **What it does:** Checks for the use of `iter.nth(0)`.
856 /// **Why is this bad?** `iter.next()` is equivalent to
857 /// `iter.nth(0)`, as they both consume the next element,
858 /// but is more readable.
860 /// **Known problems:** None.
865 /// # use std::collections::HashSet;
867 /// # let mut s = HashSet::new();
869 /// let x = s.iter().nth(0);
872 /// # let mut s = HashSet::new();
874 /// let x = s.iter().next();
878 "replace `iter.nth(0)` with `iter.next()`"
881 declare_clippy_lint! {
882 /// **What it does:** Checks for use of `.iter().nth()` (and the related
883 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
885 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
888 /// **Known problems:** None.
892 /// let some_vec = vec![0, 1, 2, 3];
893 /// let bad_vec = some_vec.iter().nth(3);
894 /// let bad_slice = &some_vec[..].iter().nth(3);
896 /// The correct use would be:
898 /// let some_vec = vec![0, 1, 2, 3];
899 /// let bad_vec = some_vec.get(3);
900 /// let bad_slice = &some_vec[..].get(3);
904 "using `.iter().nth()` on a standard library type with O(1) element access"
907 declare_clippy_lint! {
908 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
910 /// **Why is this bad?** `.nth(x)` is cleaner
912 /// **Known problems:** None.
916 /// let some_vec = vec![0, 1, 2, 3];
917 /// let bad_vec = some_vec.iter().skip(3).next();
918 /// let bad_slice = &some_vec[..].iter().skip(3).next();
920 /// The correct use would be:
922 /// let some_vec = vec![0, 1, 2, 3];
923 /// let bad_vec = some_vec.iter().nth(3);
924 /// let bad_slice = &some_vec[..].iter().nth(3);
928 "using `.skip(x).next()` on an iterator"
931 declare_clippy_lint! {
932 /// **What it does:** Checks for use of `.get().unwrap()` (or
933 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
935 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
938 /// **Known problems:** Not a replacement for error handling: Using either
939 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
940 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
941 /// temporary placeholder for dealing with the `Option` type, then this does
942 /// not mitigate the need for error handling. If there is a chance that `.get()`
943 /// will be `None` in your program, then it is advisable that the `None` case
944 /// is handled in a future refactor instead of using `.unwrap()` or the Index
949 /// let mut some_vec = vec![0, 1, 2, 3];
950 /// let last = some_vec.get(3).unwrap();
951 /// *some_vec.get_mut(0).unwrap() = 1;
953 /// The correct use would be:
955 /// let mut some_vec = vec![0, 1, 2, 3];
956 /// let last = some_vec[3];
961 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
964 declare_clippy_lint! {
965 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
966 /// `&str` or `String`.
968 /// **Why is this bad?** `.push_str(s)` is clearer
970 /// **Known problems:** None.
975 /// let def = String::from("def");
976 /// let mut s = String::new();
977 /// s.extend(abc.chars());
978 /// s.extend(def.chars());
980 /// The correct use would be:
983 /// let def = String::from("def");
984 /// let mut s = String::new();
986 /// s.push_str(&def);
988 pub STRING_EXTEND_CHARS,
990 "using `x.extend(s.chars())` where s is a `&str` or `String`"
993 declare_clippy_lint! {
994 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
997 /// **Why is this bad?** `.to_vec()` is clearer
999 /// **Known problems:** None.
1003 /// let s = [1, 2, 3, 4, 5];
1004 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
1006 /// The better use would be:
1008 /// let s = [1, 2, 3, 4, 5];
1009 /// let s2: Vec<isize> = s.to_vec();
1011 pub ITER_CLONED_COLLECT,
1013 "using `.cloned().collect()` on slice to create a `Vec`"
1016 declare_clippy_lint! {
1017 /// **What it does:** Checks for usage of `_.chars().last()` or
1018 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1020 /// **Why is this bad?** Readability, this can be written more concisely as
1021 /// `_.ends_with(_)`.
1023 /// **Known problems:** None.
1027 /// # let name = "_";
1030 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1033 /// name.ends_with('_') || name.ends_with('-');
1037 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1040 declare_clippy_lint! {
1041 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
1042 /// types before and after the call are the same.
1044 /// **Why is this bad?** The call is unnecessary.
1046 /// **Known problems:** None.
1050 /// # fn do_stuff(x: &[i32]) {}
1051 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1052 /// do_stuff(x.as_ref());
1054 /// The correct use would be:
1056 /// # fn do_stuff(x: &[i32]) {}
1057 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1062 "using `as_ref` where the types before and after the call are the same"
1065 declare_clippy_lint! {
1066 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
1067 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1068 /// `sum` or `product`.
1070 /// **Why is this bad?** Readability.
1072 /// **Known problems:** None.
1076 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1078 /// This could be written as:
1080 /// let _ = (0..3).any(|x| x > 2);
1082 pub UNNECESSARY_FOLD,
1084 "using `fold` when a more succinct alternative exists"
1087 declare_clippy_lint! {
1088 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1089 /// More specifically it checks if the closure provided is only performing one of the
1090 /// filter or map operations and suggests the appropriate option.
1092 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
1093 /// operation is being performed.
1095 /// **Known problems:** None
1099 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1101 /// // As there is no transformation of the argument this could be written as:
1102 /// let _ = (0..3).filter(|&x| x > 2);
1106 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1108 /// // As there is no conditional check on the argument this could be written as:
1109 /// let _ = (0..4).map(|x| x + 1);
1111 pub UNNECESSARY_FILTER_MAP,
1113 "using `filter_map` when a more succinct alternative exists"
1116 declare_clippy_lint! {
1117 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
1120 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
1121 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1122 /// `iter_mut` directly.
1124 /// **Known problems:** None
1130 /// let _ = (&vec![3, 4, 5]).into_iter();
1133 /// let _ = (&vec![3, 4, 5]).iter();
1135 pub INTO_ITER_ON_REF,
1137 "using `.into_iter()` on a reference"
1140 declare_clippy_lint! {
1141 /// **What it does:** Checks for calls to `map` followed by a `count`.
1143 /// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
1144 /// If the `map` call is intentional, this should be rewritten. Or, if you intend to
1145 /// drive the iterator to completion, you can just use `for_each` instead.
1147 /// **Known problems:** None
1152 /// let _ = (0..3).map(|x| x + 2).count();
1156 "suspicious usage of map"
1159 declare_clippy_lint! {
1160 /// **What it does:** Checks for `MaybeUninit::uninit().assume_init()`.
1162 /// **Why is this bad?** For most types, this is undefined behavior.
1164 /// **Known problems:** For now, we accept empty tuples and tuples / arrays
1165 /// of `MaybeUninit`. There may be other types that allow uninitialized
1166 /// data, but those are not yet rigorously defined.
1171 /// // Beware the UB
1172 /// use std::mem::MaybeUninit;
1174 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1177 /// Note that the following is OK:
1180 /// use std::mem::MaybeUninit;
1182 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1183 /// MaybeUninit::uninit().assume_init()
1186 pub UNINIT_ASSUMED_INIT,
1188 "`MaybeUninit::uninit().assume_init()`"
1191 declare_clippy_lint! {
1192 /// **What it does:** Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1194 /// **Why is this bad?** These can be written simply with `saturating_add/sub` methods.
1199 /// # let y: u32 = 0;
1200 /// # let x: u32 = 100;
1201 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1202 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1205 /// can be written using dedicated methods for saturating addition/subtraction as:
1208 /// # let y: u32 = 0;
1209 /// # let x: u32 = 100;
1210 /// let add = x.saturating_add(y);
1211 /// let sub = x.saturating_sub(y);
1213 pub MANUAL_SATURATING_ARITHMETIC,
1215 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1218 declare_clippy_lint! {
1219 /// **What it does:** Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1220 /// zero-sized types
1222 /// **Why is this bad?** This is a no-op, and likely unintended
1224 /// **Known problems:** None
1228 /// unsafe { (&() as *const ()).offset(1) };
1232 "Check for offset calculations on raw pointers to zero-sized types"
1235 declare_clippy_lint! {
1236 /// **What it does:** Checks for `FileType::is_file()`.
1238 /// **Why is this bad?** When people testing a file type with `FileType::is_file`
1239 /// they are testing whether a path is something they can get bytes from. But
1240 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1241 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1247 /// let metadata = std::fs::metadata("foo.txt")?;
1248 /// let filetype = metadata.file_type();
1250 /// if filetype.is_file() {
1253 /// # Ok::<_, std::io::Error>(())
1257 /// should be written as:
1261 /// let metadata = std::fs::metadata("foo.txt")?;
1262 /// let filetype = metadata.file_type();
1264 /// if !filetype.is_dir() {
1267 /// # Ok::<_, std::io::Error>(())
1270 pub FILETYPE_IS_FILE,
1272 "`FileType::is_file` is not recommended to test for readable file type"
1275 declare_clippy_lint! {
1276 /// **What it does:** Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1278 /// **Why is this bad?** Readability, this can be written more concisely as a
1279 /// single method call.
1281 /// **Known problems:** None.
1285 /// # let opt = Some("".to_string());
1286 /// opt.as_ref().map(String::as_str)
1289 /// Can be written as
1291 /// # let opt = Some("".to_string());
1295 pub OPTION_AS_REF_DEREF,
1297 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1300 declare_clippy_lint! {
1301 /// **What it does:** Checks for usage of `iter().next()` on a Slice or an Array
1303 /// **Why is this bad?** These can be shortened into `.get()`
1305 /// **Known problems:** None.
1309 /// # let a = [1, 2, 3];
1310 /// # let b = vec![1, 2, 3];
1311 /// a[2..].iter().next();
1312 /// b.iter().next();
1314 /// should be written as:
1316 /// # let a = [1, 2, 3];
1317 /// # let b = vec![1, 2, 3];
1321 pub ITER_NEXT_SLICE,
1323 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1326 declare_clippy_lint! {
1327 /// **What it does:** Warns when using push_str with a single-character string literal,
1328 /// and push with a char would work fine.
1330 /// **Why is this bad?** It's less clear that we are pushing a single character
1332 /// **Known problems:** None
1336 /// let mut string = String::new();
1337 /// string.push_str("R");
1339 /// Could be written as
1341 /// let mut string = String::new();
1342 /// string.push('R');
1344 pub SINGLE_CHAR_PUSH_STR,
1346 "`push_str()` used with a single-character string literal as parameter"
1349 declare_clippy_lint! {
1350 /// **What it does:** As the counterpart to `or_fun_call`, this lint looks for unnecessary
1351 /// lazily evaluated closures on `Option` and `Result`.
1353 /// This lint suggests changing the following functions, when eager evaluation results in
1355 /// - `unwrap_or_else` to `unwrap_or`
1356 /// - `and_then` to `and`
1357 /// - `or_else` to `or`
1358 /// - `get_or_insert_with` to `get_or_insert`
1359 /// - `ok_or_else` to `ok_or`
1361 /// **Why is this bad?** Using eager evaluation is shorter and simpler in some cases.
1363 /// **Known problems:** It is possible, but not recommended for `Deref` and `Index` to have
1364 /// side effects. Eagerly evaluating them can change the semantics of the program.
1369 /// // example code where clippy issues a warning
1370 /// let opt: Option<u32> = None;
1372 /// opt.unwrap_or_else(|| 42);
1376 /// let opt: Option<u32> = None;
1378 /// opt.unwrap_or(42);
1380 pub UNNECESSARY_LAZY_EVALUATIONS,
1382 "using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
1385 declare_lint_pass!(Methods => [
1388 SHOULD_IMPLEMENT_TRAIT,
1389 WRONG_SELF_CONVENTION,
1390 WRONG_PUB_SELF_CONVENTION,
1393 RESULT_MAP_OR_INTO_OPTION,
1395 BIND_INSTEAD_OF_MAP,
1403 INEFFICIENT_TO_STRING,
1405 SINGLE_CHAR_PATTERN,
1406 SINGLE_CHAR_PUSH_STR,
1408 TEMPORARY_CSTRING_AS_PTR,
1416 ITERATOR_STEP_BY_ZERO,
1422 STRING_EXTEND_CHARS,
1423 ITER_CLONED_COLLECT,
1426 UNNECESSARY_FILTER_MAP,
1429 UNINIT_ASSUMED_INIT,
1430 MANUAL_SATURATING_ARITHMETIC,
1433 OPTION_AS_REF_DEREF,
1434 UNNECESSARY_LAZY_EVALUATIONS,
1437 impl<'tcx> LateLintPass<'tcx> for Methods {
1438 #[allow(clippy::too_many_lines)]
1439 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
1440 if in_macro(expr.span) {
1444 let (method_names, arg_lists, method_spans) = method_calls(expr, 2);
1445 let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
1446 let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
1448 match method_names.as_slice() {
1449 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
1450 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
1451 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
1452 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
1453 ["expect", ..] => lint_expect(cx, expr, arg_lists[0]),
1454 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
1455 ["unwrap_or_else", "map"] => {
1456 if !lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]) {
1457 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "unwrap_or");
1460 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
1461 ["and_then", ..] => {
1462 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], false, "and");
1463 bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
1464 bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
1466 ["or_else", ..] => {
1467 unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], false, "or");
1468 bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]);
1470 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
1471 ["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
1472 ["next", "iter"] => lint_iter_next(cx, expr, arg_lists[1]),
1473 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
1474 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
1475 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
1476 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
1477 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1478 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1479 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0], method_spans[0]),
1480 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
1481 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
1482 ["is_some", "position"] => {
1483 lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
1485 ["is_some", "rposition"] => {
1486 lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
1488 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
1489 ["as_ptr", "unwrap" | "expect"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
1490 ["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
1491 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
1492 ["nth", ..] => lint_iter_nth_zero(cx, expr, arg_lists[0]),
1493 ["step_by", ..] => lint_step_by(cx, expr, arg_lists[0]),
1494 ["next", "skip"] => lint_iter_skip_next(cx, expr, arg_lists[1]),
1495 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
1496 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
1497 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
1498 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0], method_spans[0]),
1499 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
1500 ["count", "map"] => lint_suspicious_map(cx, expr),
1501 ["assume_init"] => lint_maybe_uninit(cx, &arg_lists[0][0], expr),
1502 ["unwrap_or", arith @ ("checked_add" | "checked_sub" | "checked_mul")] => {
1503 manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
1505 ["add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub"] => {
1506 check_pointer_offset(cx, expr, arg_lists[0])
1508 ["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
1509 ["map", "as_ref"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false),
1510 ["map", "as_mut"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true),
1511 ["unwrap_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "unwrap_or"),
1512 ["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "get_or_insert"),
1513 ["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "ok_or"),
1518 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args, _) => {
1519 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1520 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1522 let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0]);
1523 if args.len() == 1 && method_call.ident.name == sym!(clone) {
1524 lint_clone_on_copy(cx, expr, &args[0], self_ty);
1525 lint_clone_on_ref_ptr(cx, expr, &args[0]);
1527 if args.len() == 1 && method_call.ident.name == sym!(to_string) {
1528 inefficient_to_string::lint(cx, expr, &args[0], self_ty);
1531 if let Some(fn_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
1532 if match_def_path(cx, fn_def_id, &paths::PUSH_STR) {
1533 lint_single_char_push_string(cx, expr, args);
1537 match self_ty.kind {
1538 ty::Ref(_, ty, _) if ty.kind == ty::Str => {
1539 for &(method, pos) in &PATTERN_METHODS {
1540 if method_call.ident.name.as_str() == method && args.len() > pos {
1541 lint_single_char_pattern(cx, expr, &args[pos]);
1545 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
1546 lint_into_iter(cx, expr, self_ty, *method_span);
1551 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1552 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1554 let mut info = BinaryExprInfo {
1558 eq: op.node == hir::BinOpKind::Eq,
1560 lint_binary_expr_with_method_call(cx, &mut info);
1566 #[allow(clippy::too_many_lines)]
1567 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
1568 if in_external_macro(cx.sess(), impl_item.span) {
1571 let name = impl_item.ident.name.as_str();
1572 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1573 let item = cx.tcx.hir().expect_item(parent);
1574 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1575 let self_ty = cx.tcx.type_of(def_id);
1577 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
1578 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1579 if let hir::ItemKind::Impl{ of_trait: None, .. } = item.kind;
1581 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1582 let method_sig = cx.tcx.fn_sig(method_def_id);
1583 let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
1585 let first_arg_ty = &method_sig.inputs().iter().next();
1587 // check conventions w.r.t. conversion method names and predicates
1588 if let Some(first_arg_ty) = first_arg_ty;
1591 if cx.access_levels.is_exported(impl_item.hir_id) {
1592 // check missing trait implementations
1593 for method_config in &TRAIT_METHODS {
1594 if name == method_config.method_name &&
1595 sig.decl.inputs.len() == method_config.param_count &&
1596 method_config.output_type.matches(cx, &sig.decl.output) &&
1597 method_config.self_kind.matches(cx, self_ty, first_arg_ty) &&
1598 fn_header_equals(method_config.fn_header, sig.header) &&
1599 method_config.lifetime_param_cond(&impl_item)
1603 SHOULD_IMPLEMENT_TRAIT,
1606 "method `{}` can be confused for the standard trait method `{}::{}`",
1607 method_config.method_name,
1608 method_config.trait_name,
1609 method_config.method_name
1613 "consider implementing the trait `{}` or choosing a less ambiguous method name",
1614 method_config.trait_name
1621 if let Some((ref conv, self_kinds)) = &CONVENTIONS
1623 .find(|(ref conv, _)| conv.check(&name))
1625 if !self_kinds.iter().any(|k| k.matches(cx, self_ty, first_arg_ty)) {
1626 let lint = if item.vis.node.is_pub() {
1627 WRONG_PUB_SELF_CONVENTION
1629 WRONG_SELF_CONVENTION
1636 &format!("methods called `{}` usually take {}; consider choosing a less ambiguous name",
1640 .map(|k| k.description())
1641 .collect::<Vec<_>>()
1650 // if this impl block implements a trait, lint in trait definition instead
1651 if let hir::ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
1655 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
1656 let ret_ty = return_ty(cx, impl_item.hir_id);
1658 // walk the return type and check for Self (this does not check associated types)
1659 if contains_ty(ret_ty, self_ty) {
1663 // if return type is impl trait, check the associated types
1664 if let ty::Opaque(def_id, _) = ret_ty.kind {
1665 // one of the associated types must be Self
1666 for &(predicate, _span) in cx.tcx.predicates_of(def_id).predicates {
1667 if let ty::PredicateAtom::Projection(projection_predicate) = predicate.skip_binders() {
1668 // walk the associated type and check for Self
1669 if contains_ty(projection_predicate.ty, self_ty) {
1676 if name == "new" && !TyS::same_type(ret_ty, self_ty) {
1681 "methods called `new` usually return `Self`",
1687 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
1689 if !in_external_macro(cx.tcx.sess, item.span);
1690 if item.ident.name == sym!(new);
1691 if let TraitItemKind::Fn(_, _) = item.kind;
1692 let ret_ty = return_ty(cx, item.hir_id);
1693 let self_ty = TraitRef::identity(cx.tcx, item.hir_id.owner.to_def_id()).self_ty();
1694 if !contains_ty(ret_ty, self_ty);
1701 "methods called `new` usually return `Self`",
1708 /// Checks for the `OR_FUN_CALL` lint.
1709 #[allow(clippy::too_many_lines)]
1710 fn lint_or_fun_call<'tcx>(
1711 cx: &LateContext<'tcx>,
1712 expr: &hir::Expr<'_>,
1715 args: &'tcx [hir::Expr<'_>],
1717 // Searches an expression for method calls or function calls that aren't ctors
1718 struct FunCallFinder<'a, 'tcx> {
1719 cx: &'a LateContext<'tcx>,
1723 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1724 type Map = Map<'tcx>;
1726 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
1727 let call_found = match &expr.kind {
1728 // ignore enum and struct constructors
1729 hir::ExprKind::Call(..) => !is_ctor_or_promotable_const_function(self.cx, expr),
1730 hir::ExprKind::MethodCall(..) => true,
1739 intravisit::walk_expr(self, expr);
1743 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1744 intravisit::NestedVisitorMap::None
1748 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1749 fn check_unwrap_or_default(
1750 cx: &LateContext<'_>,
1752 fun: &hir::Expr<'_>,
1753 self_expr: &hir::Expr<'_>,
1754 arg: &hir::Expr<'_>,
1760 if name == "unwrap_or";
1761 if let hir::ExprKind::Path(ref qpath) = fun.kind;
1762 let path = &*last_path_segment(qpath).ident.as_str();
1763 if ["default", "new"].contains(&path);
1764 let arg_ty = cx.typeck_results().expr_ty(arg);
1765 if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
1766 if implements_trait(cx, arg_ty, default_trait_id, &[]);
1769 let mut applicability = Applicability::MachineApplicable;
1774 &format!("use of `{}` followed by a call to `{}`", name, path),
1777 "{}.unwrap_or_default()",
1778 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1790 /// Checks for `*or(foo())`.
1791 #[allow(clippy::too_many_arguments)]
1792 fn check_general_case<'tcx>(
1793 cx: &LateContext<'tcx>,
1797 self_expr: &hir::Expr<'_>,
1798 arg: &'tcx hir::Expr<'_>,
1802 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = &arg.kind {
1803 if path.ident.as_str() == "len" {
1804 let ty = walk_ptrs_ty(cx.typeck_results().expr_ty(&args[0]));
1807 ty::Slice(_) | ty::Array(_, _) => return,
1811 if match_type(cx, ty, &paths::VEC) {
1817 // (path, fn_has_argument, methods, suffix)
1818 let know_types: &[(&[_], _, &[_], _)] = &[
1819 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1820 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1821 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1822 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1826 if know_types.iter().any(|k| k.2.contains(&name));
1828 let mut finder = FunCallFinder { cx: &cx, found: false };
1829 if { finder.visit_expr(&arg); finder.found };
1830 if !contains_return(&arg);
1832 let self_ty = cx.typeck_results().expr_ty(self_expr);
1834 if let Some(&(_, fn_has_arguments, poss, suffix)) =
1835 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0));
1837 if poss.contains(&name);
1840 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1841 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1842 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1843 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1845 let span_replace_word = method_span.with_hi(span.hi());
1850 &format!("use of `{}` followed by a function call", name),
1852 format!("{}_{}({})", name, suffix, sugg),
1853 Applicability::HasPlaceholders,
1859 if args.len() == 2 {
1860 match args[1].kind {
1861 hir::ExprKind::Call(ref fun, ref or_args) => {
1862 let or_has_args = !or_args.is_empty();
1863 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1876 hir::ExprKind::MethodCall(_, span, ref or_args, _) => check_general_case(
1883 !or_args.is_empty(),
1891 /// Checks for the `EXPECT_FUN_CALL` lint.
1892 #[allow(clippy::too_many_lines)]
1893 fn lint_expect_fun_call(
1894 cx: &LateContext<'_>,
1895 expr: &hir::Expr<'_>,
1898 args: &[hir::Expr<'_>],
1900 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1902 fn get_arg_root<'a>(cx: &LateContext<'_>, arg: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
1903 let mut arg_root = arg;
1905 arg_root = match &arg_root.kind {
1906 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => expr,
1907 hir::ExprKind::MethodCall(method_name, _, call_args, _) => {
1908 if call_args.len() == 1
1909 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1911 let arg_type = cx.typeck_results().expr_ty(&call_args[0]);
1912 let base_type = walk_ptrs_ty(arg_type);
1913 base_type.kind == ty::Str || is_type_diagnostic_item(cx, base_type, sym!(string_type))
1927 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1928 // converted to string.
1929 fn requires_to_string(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1930 let arg_ty = cx.typeck_results().expr_ty(arg);
1931 if is_type_diagnostic_item(cx, arg_ty, sym!(string_type)) {
1934 if let ty::Ref(_, ty, ..) = arg_ty.kind {
1935 if ty.kind == ty::Str && can_be_static_str(cx, arg) {
1942 // Check if an expression could have type `&'static str`, knowing that it
1943 // has type `&str` for some lifetime.
1944 fn can_be_static_str(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
1946 hir::ExprKind::Lit(_) => true,
1947 hir::ExprKind::Call(fun, _) => {
1948 if let hir::ExprKind::Path(ref p) = fun.kind {
1949 match cx.qpath_res(p, fun.hir_id) {
1950 hir::def::Res::Def(hir::def::DefKind::Fn | hir::def::DefKind::AssocFn, def_id) => matches!(
1951 cx.tcx.fn_sig(def_id).output().skip_binder().kind,
1952 ty::Ref(ty::ReStatic, ..)
1960 hir::ExprKind::MethodCall(..) => {
1962 .type_dependent_def_id(arg.hir_id)
1963 .map_or(false, |method_id| {
1965 cx.tcx.fn_sig(method_id).output().skip_binder().kind,
1966 ty::Ref(ty::ReStatic, ..)
1970 hir::ExprKind::Path(ref p) => matches!(
1971 cx.qpath_res(p, arg.hir_id),
1972 hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static, _)
1978 fn generate_format_arg_snippet(
1979 cx: &LateContext<'_>,
1981 applicability: &mut Applicability,
1984 if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref format_arg) = a.kind;
1985 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.kind;
1986 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.kind;
1991 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1999 fn is_call(node: &hir::ExprKind<'_>) -> bool {
2001 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => {
2004 hir::ExprKind::Call(..)
2005 | hir::ExprKind::MethodCall(..)
2006 // These variants are debatable or require further examination
2007 | hir::ExprKind::Match(..)
2008 | hir::ExprKind::Block{ .. } => true,
2013 if args.len() != 2 || name != "expect" || !is_call(&args[1].kind) {
2017 let receiver_type = cx.typeck_results().expr_ty_adjusted(&args[0]);
2018 let closure_args = if is_type_diagnostic_item(cx, receiver_type, sym!(option_type)) {
2020 } else if is_type_diagnostic_item(cx, receiver_type, sym!(result_type)) {
2026 let arg_root = get_arg_root(cx, &args[1]);
2028 let span_replace_word = method_span.with_hi(expr.span.hi());
2030 let mut applicability = Applicability::MachineApplicable;
2032 //Special handling for `format!` as arg_root
2034 if let hir::ExprKind::Block(block, None) = &arg_root.kind;
2035 if block.stmts.len() == 1;
2036 if let hir::StmtKind::Local(local) = &block.stmts[0].kind;
2037 if let Some(arg_root) = &local.init;
2038 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.kind;
2039 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1;
2040 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].kind;
2042 let fmt_spec = &format_args[0];
2043 let fmt_args = &format_args[1];
2045 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
2047 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
2049 let sugg = args.join(", ");
2055 &format!("use of `{}` followed by a function call", name),
2057 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
2065 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
2066 if requires_to_string(cx, arg_root) {
2067 arg_root_snippet.to_mut().push_str(".to_string()");
2074 &format!("use of `{}` followed by a function call", name),
2076 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
2081 /// Checks for the `CLONE_ON_COPY` lint.
2082 fn lint_clone_on_copy(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
2083 let ty = cx.typeck_results().expr_ty(expr);
2084 if let ty::Ref(_, inner, _) = arg_ty.kind {
2085 if let ty::Ref(_, innermost, _) = inner.kind {
2090 "using `clone` on a double-reference; \
2091 this will copy the reference instead of cloning the inner type",
2093 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
2094 let mut ty = innermost;
2096 while let ty::Ref(_, inner, _) = ty.kind {
2100 let refs: String = iter::repeat('&').take(n + 1).collect();
2101 let derefs: String = iter::repeat('*').take(n).collect();
2102 let explicit = format!("<{}{}>::clone({})", refs, ty, snip);
2103 diag.span_suggestion(
2105 "try dereferencing it",
2106 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
2107 Applicability::MaybeIncorrect,
2109 diag.span_suggestion(
2111 "or try being explicit if you are sure, that you want to clone a reference",
2113 Applicability::MaybeIncorrect,
2118 return; // don't report clone_on_copy
2122 if is_copy(cx, ty) {
2124 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
2125 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
2126 match &cx.tcx.hir().get(parent) {
2127 hir::Node::Expr(parent) => match parent.kind {
2128 // &*x is a nop, &x.clone() is not
2129 hir::ExprKind::AddrOf(..) => return,
2130 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
2131 hir::ExprKind::MethodCall(_, _, parent_args, _) if expr.hir_id == parent_args[0].hir_id => {
2137 hir::Node::Stmt(stmt) => {
2138 if let hir::StmtKind::Local(ref loc) = stmt.kind {
2139 if let hir::PatKind::Ref(..) = loc.pat.kind {
2140 // let ref y = *x borrows x, let ref y = x.clone() does not
2148 // x.clone() might have dereferenced x, possibly through Deref impls
2149 if cx.typeck_results().expr_ty(arg) == ty {
2150 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
2152 let deref_count = cx
2154 .expr_adjustments(arg)
2156 .filter(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(_)))
2158 let derefs: String = iter::repeat('*').take(deref_count).collect();
2159 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
2164 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |diag| {
2165 if let Some((text, snip)) = snip {
2166 diag.span_suggestion(expr.span, text, snip, Applicability::MachineApplicable);
2172 fn lint_clone_on_ref_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
2173 let obj_ty = walk_ptrs_ty(cx.typeck_results().expr_ty(arg));
2175 if let ty::Adt(_, subst) = obj_ty.kind {
2176 let caller_type = if is_type_diagnostic_item(cx, obj_ty, sym::Rc) {
2178 } else if is_type_diagnostic_item(cx, obj_ty, sym::Arc) {
2180 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
2186 let snippet = snippet_with_macro_callsite(cx, arg.span, "_");
2192 "using `.clone()` on a ref-counted pointer",
2194 format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet),
2195 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
2200 fn lint_string_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2202 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
2203 let target = &arglists[0][0];
2204 let self_ty = walk_ptrs_ty(cx.typeck_results().expr_ty(target));
2205 let ref_str = if self_ty.kind == ty::Str {
2207 } else if is_type_diagnostic_item(cx, self_ty, sym!(string_type)) {
2213 let mut applicability = Applicability::MachineApplicable;
2216 STRING_EXTEND_CHARS,
2218 "calling `.extend(_.chars())`",
2221 "{}.push_str({}{})",
2222 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
2224 snippet_with_applicability(cx, target.span, "_", &mut applicability)
2231 fn lint_extend(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2232 let obj_ty = walk_ptrs_ty(cx.typeck_results().expr_ty(&args[0]));
2233 if is_type_diagnostic_item(cx, obj_ty, sym!(string_type)) {
2234 lint_string_extend(cx, expr, args);
2238 fn lint_cstring_as_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, source: &hir::Expr<'_>, unwrap: &hir::Expr<'_>) {
2240 let source_type = cx.typeck_results().expr_ty(source);
2241 if let ty::Adt(def, substs) = source_type.kind;
2242 if cx.tcx.is_diagnostic_item(sym!(result_type), def.did);
2243 if match_type(cx, substs.type_at(0), &paths::CSTRING);
2247 TEMPORARY_CSTRING_AS_PTR,
2249 "you are getting the inner pointer of a temporary `CString`",
2251 diag.note("that pointer will be invalid outside this expression");
2252 diag.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
2258 fn lint_iter_cloned_collect<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2260 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym!(vec_type));
2261 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0]));
2262 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite());
2267 ITER_CLONED_COLLECT,
2269 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
2272 ".to_vec()".to_string(),
2273 Applicability::MachineApplicable,
2279 fn lint_unnecessary_fold(cx: &LateContext<'_>, expr: &hir::Expr<'_>, fold_args: &[hir::Expr<'_>], fold_span: Span) {
2280 fn check_fold_with_op(
2281 cx: &LateContext<'_>,
2282 expr: &hir::Expr<'_>,
2283 fold_args: &[hir::Expr<'_>],
2286 replacement_method_name: &str,
2287 replacement_has_args: bool,
2290 // Extract the body of the closure passed to fold
2291 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].kind;
2292 let closure_body = cx.tcx.hir().body(body_id);
2293 let closure_expr = remove_blocks(&closure_body.value);
2295 // Check if the closure body is of the form `acc <op> some_expr(x)`
2296 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.kind;
2297 if bin_op.node == op;
2299 // Extract the names of the two arguments to the closure
2300 if let Some(first_arg_ident) = get_arg_name(&closure_body.params[0].pat);
2301 if let Some(second_arg_ident) = get_arg_name(&closure_body.params[1].pat);
2303 if match_var(&*left_expr, first_arg_ident);
2304 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
2307 let mut applicability = Applicability::MachineApplicable;
2308 let sugg = if replacement_has_args {
2310 "{replacement}(|{s}| {r})",
2311 replacement = replacement_method_name,
2312 s = second_arg_ident,
2313 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
2318 replacement = replacement_method_name,
2325 fold_span.with_hi(expr.span.hi()),
2326 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
2327 "this `.fold` can be written more succinctly using another method",
2336 // Check that this is a call to Iterator::fold rather than just some function called fold
2337 if !match_trait_method(cx, expr, &paths::ITERATOR) {
2342 fold_args.len() == 3,
2343 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
2346 // Check if the first argument to .fold is a suitable literal
2347 if let hir::ExprKind::Lit(ref lit) = fold_args[1].kind {
2349 ast::LitKind::Bool(false) => {
2350 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Or, "any", true)
2352 ast::LitKind::Bool(true) => {
2353 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::And, "all", true)
2355 ast::LitKind::Int(0, _) => {
2356 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Add, "sum", false)
2358 ast::LitKind::Int(1, _) => {
2359 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Mul, "product", false)
2366 fn lint_step_by<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, args: &'tcx [hir::Expr<'_>]) {
2367 if match_trait_method(cx, expr, &paths::ITERATOR) {
2368 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &args[1]) {
2371 ITERATOR_STEP_BY_ZERO,
2373 "Iterator::step_by(0) will panic at runtime",
2379 fn lint_iter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2380 let caller_expr = &iter_args[0];
2382 // Skip lint if the `iter().next()` expression is a for loop argument,
2383 // since it is already covered by `&loops::ITER_NEXT_LOOP`
2384 let mut parent_expr_opt = get_parent_expr(cx, expr);
2385 while let Some(parent_expr) = parent_expr_opt {
2386 if higher::for_loop(parent_expr).is_some() {
2389 parent_expr_opt = get_parent_expr(cx, parent_expr);
2392 if derefs_to_slice(cx, caller_expr, cx.typeck_results().expr_ty(caller_expr)).is_some() {
2393 // caller is a Slice
2395 if let hir::ExprKind::Index(ref caller_var, ref index_expr) = &caller_expr.kind;
2396 if let Some(higher::Range { start: Some(start_expr), end: None, limits: ast::RangeLimits::HalfOpen })
2397 = higher::range(index_expr);
2398 if let hir::ExprKind::Lit(ref start_lit) = &start_expr.kind;
2399 if let ast::LitKind::Int(start_idx, _) = start_lit.node;
2401 let mut applicability = Applicability::MachineApplicable;
2406 "using `.iter().next()` on a Slice without end index",
2408 format!("{}.get({})", snippet_with_applicability(cx, caller_var.span, "..", &mut applicability), start_idx),
2413 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(caller_expr), sym!(vec_type))
2415 &walk_ptrs_ty(cx.typeck_results().expr_ty(caller_expr)).kind,
2419 // caller is a Vec or an Array
2420 let mut applicability = Applicability::MachineApplicable;
2425 "using `.iter().next()` on an array",
2429 snippet_with_applicability(cx, caller_expr.span, "..", &mut applicability)
2436 fn lint_iter_nth<'tcx>(
2437 cx: &LateContext<'tcx>,
2438 expr: &hir::Expr<'_>,
2439 nth_and_iter_args: &[&'tcx [hir::Expr<'tcx>]],
2442 let iter_args = nth_and_iter_args[1];
2443 let mut_str = if is_mut { "_mut" } else { "" };
2444 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0])).is_some() {
2446 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym!(vec_type)) {
2448 } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&iter_args[0]), sym!(vecdeque_type)) {
2451 let nth_args = nth_and_iter_args[0];
2452 lint_iter_nth_zero(cx, expr, &nth_args);
2453 return; // caller is not a type that we want to lint
2460 &format!("called `.iter{0}().nth()` on a {1}", mut_str, caller_type),
2462 &format!("calling `.get{}()` is both faster and more readable", mut_str),
2466 fn lint_iter_nth_zero<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
2468 if match_trait_method(cx, expr, &paths::ITERATOR);
2469 if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &nth_args[1]);
2471 let mut applicability = Applicability::MachineApplicable;
2476 "called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
2477 "try calling `.next()` instead of `.nth(0)`",
2478 format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
2485 fn lint_get_unwrap<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, get_args: &'tcx [hir::Expr<'_>], is_mut: bool) {
2486 // Note: we don't want to lint `get_mut().unwrap` for `HashMap` or `BTreeMap`,
2487 // because they do not implement `IndexMut`
2488 let mut applicability = Applicability::MachineApplicable;
2489 let expr_ty = cx.typeck_results().expr_ty(&get_args[0]);
2490 let get_args_str = if get_args.len() > 1 {
2491 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
2493 return; // not linting on a .get().unwrap() chain or variant
2496 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
2497 needs_ref = get_args_str.parse::<usize>().is_ok();
2499 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vec_type)) {
2500 needs_ref = get_args_str.parse::<usize>().is_ok();
2502 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vecdeque_type)) {
2503 needs_ref = get_args_str.parse::<usize>().is_ok();
2505 } else if !is_mut && is_type_diagnostic_item(cx, expr_ty, sym!(hashmap_type)) {
2508 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
2512 return; // caller is not a type that we want to lint
2515 let mut span = expr.span;
2517 // Handle the case where the result is immediately dereferenced
2518 // by not requiring ref and pulling the dereference into the
2522 if let Some(parent) = get_parent_expr(cx, expr);
2523 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.kind;
2530 let mut_str = if is_mut { "_mut" } else { "" };
2531 let borrow_str = if !needs_ref {
2544 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
2545 mut_str, caller_type
2551 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
2558 fn lint_iter_skip_next(cx: &LateContext<'_>, expr: &hir::Expr<'_>, skip_args: &[hir::Expr<'_>]) {
2559 // lint if caller of skip is an Iterator
2560 if match_trait_method(cx, expr, &paths::ITERATOR) {
2561 if let [caller, n] = skip_args {
2562 let hint = format!(".nth({})", snippet(cx, n.span, ".."));
2566 expr.span.trim_start(caller.span).unwrap(),
2567 "called `skip(x).next()` on an iterator",
2568 "use `nth` instead",
2570 Applicability::MachineApplicable,
2576 fn derefs_to_slice<'tcx>(
2577 cx: &LateContext<'tcx>,
2578 expr: &'tcx hir::Expr<'tcx>,
2580 ) -> Option<&'tcx hir::Expr<'tcx>> {
2581 fn may_slice<'a>(cx: &LateContext<'a>, ty: Ty<'a>) -> bool {
2583 ty::Slice(_) => true,
2584 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
2585 ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym!(vec_type)),
2586 ty::Array(_, size) => size
2587 .try_eval_usize(cx.tcx, cx.param_env)
2588 .map_or(false, |size| size < 32),
2589 ty::Ref(_, inner, _) => may_slice(cx, inner),
2594 if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind {
2595 if path.ident.name == sym!(iter) && may_slice(cx, cx.typeck_results().expr_ty(&args[0])) {
2602 ty::Slice(_) => Some(expr),
2603 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
2604 ty::Ref(_, inner, _) => {
2605 if may_slice(cx, inner) {
2616 /// lint use of `unwrap()` for `Option`s and `Result`s
2617 fn lint_unwrap(cx: &LateContext<'_>, expr: &hir::Expr<'_>, unwrap_args: &[hir::Expr<'_>]) {
2618 let obj_ty = walk_ptrs_ty(cx.typeck_results().expr_ty(&unwrap_args[0]));
2620 let mess = if is_type_diagnostic_item(cx, obj_ty, sym!(option_type)) {
2621 Some((UNWRAP_USED, "an Option", "None"))
2622 } else if is_type_diagnostic_item(cx, obj_ty, sym!(result_type)) {
2623 Some((UNWRAP_USED, "a Result", "Err"))
2628 if let Some((lint, kind, none_value)) = mess {
2633 &format!("used `unwrap()` on `{}` value", kind,),
2636 "if you don't want to handle the `{}` case gracefully, consider \
2637 using `expect()` to provide a better panic message",
2644 /// lint use of `expect()` for `Option`s and `Result`s
2645 fn lint_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, expect_args: &[hir::Expr<'_>]) {
2646 let obj_ty = walk_ptrs_ty(cx.typeck_results().expr_ty(&expect_args[0]));
2648 let mess = if is_type_diagnostic_item(cx, obj_ty, sym!(option_type)) {
2649 Some((EXPECT_USED, "an Option", "None"))
2650 } else if is_type_diagnostic_item(cx, obj_ty, sym!(result_type)) {
2651 Some((EXPECT_USED, "a Result", "Err"))
2656 if let Some((lint, kind, none_value)) = mess {
2661 &format!("used `expect()` on `{}` value", kind,),
2663 &format!("if this value is an `{}`, it will panic", none_value,),
2668 /// lint use of `ok().expect()` for `Result`s
2669 fn lint_ok_expect(cx: &LateContext<'_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
2671 // lint if the caller of `ok()` is a `Result`
2672 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&ok_args[0]), sym!(result_type));
2673 let result_type = cx.typeck_results().expr_ty(&ok_args[0]);
2674 if let Some(error_type) = get_error_type(cx, result_type);
2675 if has_debug_impl(error_type, cx);
2682 "called `ok().expect()` on a `Result` value",
2684 "you can call `expect()` directly on the `Result`",
2690 /// lint use of `map().flatten()` for `Iterators` and 'Options'
2691 fn lint_map_flatten<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) {
2692 // lint if caller of `.map().flatten()` is an Iterator
2693 if match_trait_method(cx, expr, &paths::ITERATOR) {
2694 let map_closure_ty = cx.typeck_results().expr_ty(&map_args[1]);
2695 let is_map_to_option = match map_closure_ty.kind {
2696 ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
2697 let map_closure_sig = match map_closure_ty.kind {
2698 ty::Closure(_, substs) => substs.as_closure().sig(),
2699 _ => map_closure_ty.fn_sig(cx.tcx),
2701 let map_closure_return_ty = cx.tcx.erase_late_bound_regions(&map_closure_sig.output());
2702 is_type_diagnostic_item(cx, map_closure_return_ty, sym!(option_type))
2707 let method_to_use = if is_map_to_option {
2708 // `(...).map(...)` has type `impl Iterator<Item=Option<...>>
2711 // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
2714 let func_snippet = snippet(cx, map_args[1].span, "..");
2715 let hint = format!(".{0}({1})", method_to_use, func_snippet);
2719 expr.span.with_lo(map_args[0].span.hi()),
2720 "called `map(..).flatten()` on an `Iterator`",
2721 &format!("try using `{}` instead", method_to_use),
2723 Applicability::MachineApplicable,
2727 // lint if caller of `.map().flatten()` is an Option
2728 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym!(option_type)) {
2729 let func_snippet = snippet(cx, map_args[1].span, "..");
2730 let hint = format!(".and_then({})", func_snippet);
2734 expr.span.with_lo(map_args[0].span.hi()),
2735 "called `map(..).flatten()` on an `Option`",
2736 "try using `and_then` instead",
2738 Applicability::MachineApplicable,
2743 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
2744 /// Return true if lint triggered
2745 fn lint_map_unwrap_or_else<'tcx>(
2746 cx: &LateContext<'tcx>,
2747 expr: &'tcx hir::Expr<'_>,
2748 map_args: &'tcx [hir::Expr<'_>],
2749 unwrap_args: &'tcx [hir::Expr<'_>],
2751 // lint if the caller of `map()` is an `Option`
2752 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym!(option_type));
2753 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_args[0]), sym!(result_type));
2755 if is_option || is_result {
2756 // Don't make a suggestion that may fail to compile due to mutably borrowing
2757 // the same variable twice.
2758 let map_mutated_vars = mutated_variables(&map_args[0], cx);
2759 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
2760 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
2761 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
2769 let msg = if is_option {
2770 "called `map(f).unwrap_or_else(g)` on an `Option` value. This can be done more directly by calling \
2771 `map_or_else(g, f)` instead"
2773 "called `map(f).unwrap_or_else(g)` on a `Result` value. This can be done more directly by calling \
2774 `.map_or_else(g, f)` instead"
2776 // get snippets for args to map() and unwrap_or_else()
2777 let map_snippet = snippet(cx, map_args[1].span, "..");
2778 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
2779 // lint, with note if neither arg is > 1 line and both map() and
2780 // unwrap_or_else() have the same span
2781 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
2782 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
2783 if same_span && !multiline {
2791 "replace `map({0}).unwrap_or_else({1})` with `map_or_else({1}, {0})`",
2792 map_snippet, unwrap_snippet,
2796 } else if same_span && multiline {
2797 span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
2805 /// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
2806 fn lint_map_or_none<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_or_args: &'tcx [hir::Expr<'_>]) {
2807 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym!(option_type));
2808 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym!(result_type));
2810 // There are two variants of this `map_or` lint:
2811 // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
2812 // (2) using `map_or` as a combinator instead of `and_then`
2814 // (For this lint) we don't care if any other type calls `map_or`
2815 if !is_option && !is_result {
2819 let (lint_name, msg, instead, hint) = {
2820 let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
2821 match_qpath(qpath, &paths::OPTION_NONE)
2826 if !default_arg_is_none {
2831 let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
2832 match_qpath(qpath, &paths::OPTION_SOME)
2838 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2839 let func_snippet = snippet(cx, map_or_args[2].span, "..");
2840 let msg = "called `map_or(None, f)` on an `Option` value. This can be done more directly by calling \
2841 `and_then(f)` instead";
2845 "try using `and_then` instead",
2846 format!("{0}.and_then({1})", self_snippet, func_snippet),
2848 } else if f_arg_is_some {
2849 let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
2851 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2853 RESULT_MAP_OR_INTO_OPTION,
2855 "try using `ok` instead",
2856 format!("{0}.ok()", self_snippet),
2871 Applicability::MachineApplicable,
2875 /// lint use of `filter().next()` for `Iterators`
2876 fn lint_filter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
2877 // lint if caller of `.filter().next()` is an Iterator
2878 if match_trait_method(cx, expr, &paths::ITERATOR) {
2879 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2880 `.find(p)` instead.";
2881 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2882 if filter_snippet.lines().count() <= 1 {
2883 // add note if not multi-line
2890 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
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(p).map(q)` 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 /// lint use of `filter_map().next()` for `Iterators`
2933 fn lint_filter_map_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
2934 if match_trait_method(cx, expr, &paths::ITERATOR) {
2935 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2936 `.find_map(p)` instead.";
2937 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2938 if filter_snippet.lines().count() <= 1 {
2945 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2948 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2953 /// lint use of `find().map()` for `Iterators`
2954 fn lint_find_map<'tcx>(
2955 cx: &LateContext<'tcx>,
2956 expr: &'tcx hir::Expr<'_>,
2957 _find_args: &'tcx [hir::Expr<'_>],
2958 map_args: &'tcx [hir::Expr<'_>],
2960 // lint if caller of `.filter().map()` is an Iterator
2961 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2962 let msg = "called `find(p).map(q)` on an `Iterator`";
2963 let hint = "this is more succinctly expressed by calling `.find_map(..)` instead";
2964 span_lint_and_help(cx, FIND_MAP, expr.span, msg, None, hint);
2968 /// lint use of `filter_map().map()` for `Iterators`
2969 fn lint_filter_map_map<'tcx>(
2970 cx: &LateContext<'tcx>,
2971 expr: &'tcx hir::Expr<'_>,
2972 _filter_args: &'tcx [hir::Expr<'_>],
2973 _map_args: &'tcx [hir::Expr<'_>],
2975 // lint if caller of `.filter().map()` is an Iterator
2976 if match_trait_method(cx, expr, &paths::ITERATOR) {
2977 let msg = "called `filter_map(p).map(q)` on an `Iterator`";
2978 let hint = "this is more succinctly expressed by only calling `.filter_map(..)` instead";
2979 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2983 /// lint use of `filter().flat_map()` for `Iterators`
2984 fn lint_filter_flat_map<'tcx>(
2985 cx: &LateContext<'tcx>,
2986 expr: &'tcx hir::Expr<'_>,
2987 _filter_args: &'tcx [hir::Expr<'_>],
2988 _map_args: &'tcx [hir::Expr<'_>],
2990 // lint if caller of `.filter().flat_map()` is an Iterator
2991 if match_trait_method(cx, expr, &paths::ITERATOR) {
2992 let msg = "called `filter(p).flat_map(q)` on an `Iterator`";
2993 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
2994 and filtering by returning `iter::empty()`";
2995 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2999 /// lint use of `filter_map().flat_map()` for `Iterators`
3000 fn lint_filter_map_flat_map<'tcx>(
3001 cx: &LateContext<'tcx>,
3002 expr: &'tcx hir::Expr<'_>,
3003 _filter_args: &'tcx [hir::Expr<'_>],
3004 _map_args: &'tcx [hir::Expr<'_>],
3006 // lint if caller of `.filter_map().flat_map()` is an Iterator
3007 if match_trait_method(cx, expr, &paths::ITERATOR) {
3008 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`";
3009 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
3010 and filtering by returning `iter::empty()`";
3011 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
3015 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
3016 fn lint_flat_map_identity<'tcx>(
3017 cx: &LateContext<'tcx>,
3018 expr: &'tcx hir::Expr<'_>,
3019 flat_map_args: &'tcx [hir::Expr<'_>],
3020 flat_map_span: Span,
3022 if match_trait_method(cx, expr, &paths::ITERATOR) {
3023 let arg_node = &flat_map_args[1].kind;
3025 let apply_lint = |message: &str| {
3029 flat_map_span.with_hi(expr.span.hi()),
3032 "flatten()".to_string(),
3033 Applicability::MachineApplicable,
3038 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
3039 let body = cx.tcx.hir().body(*body_id);
3041 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
3042 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
3044 if path.segments.len() == 1;
3045 if path.segments[0].ident.as_str() == binding_ident.as_str();
3048 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
3053 if let hir::ExprKind::Path(ref qpath) = arg_node;
3055 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
3058 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
3064 /// lint searching an Iterator followed by `is_some()`
3065 fn lint_search_is_some<'tcx>(
3066 cx: &LateContext<'tcx>,
3067 expr: &'tcx hir::Expr<'_>,
3068 search_method: &str,
3069 search_args: &'tcx [hir::Expr<'_>],
3070 is_some_args: &'tcx [hir::Expr<'_>],
3073 // lint if caller of search is an Iterator
3074 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
3076 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
3077 expressed by calling `any()`.",
3080 let search_snippet = snippet(cx, search_args[1].span, "..");
3081 if search_snippet.lines().count() <= 1 {
3082 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
3083 // suggest `any(|..| *..)` instead of `any(|..| **..)` for `find(|..| **..).is_some()`
3084 let any_search_snippet = if_chain! {
3085 if search_method == "find";
3086 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].kind;
3087 let closure_body = cx.tcx.hir().body(body_id);
3088 if let Some(closure_arg) = closure_body.params.get(0);
3090 if let hir::PatKind::Ref(..) = closure_arg.pat.kind {
3091 Some(search_snippet.replacen('&', "", 1))
3092 } else if let Some(name) = get_arg_name(&closure_arg.pat) {
3093 Some(search_snippet.replace(&format!("*{}", name), &name.as_str()))
3101 // add note if not multi-line
3105 method_span.with_hi(expr.span.hi()),
3110 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
3112 Applicability::MachineApplicable,
3115 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
3120 /// Used for `lint_binary_expr_with_method_call`.
3121 #[derive(Copy, Clone)]
3122 struct BinaryExprInfo<'a> {
3123 expr: &'a hir::Expr<'a>,
3124 chain: &'a hir::Expr<'a>,
3125 other: &'a hir::Expr<'a>,
3129 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3130 fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
3131 macro_rules! lint_with_both_lhs_and_rhs {
3132 ($func:ident, $cx:expr, $info:ident) => {
3133 if !$func($cx, $info) {
3134 ::std::mem::swap(&mut $info.chain, &mut $info.other);
3135 if $func($cx, $info) {
3142 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
3143 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
3144 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
3145 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
3148 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3150 cx: &LateContext<'_>,
3151 info: &BinaryExprInfo<'_>,
3152 chain_methods: &[&str],
3153 lint: &'static Lint,
3157 if let Some(args) = method_chain_args(info.chain, chain_methods);
3158 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
3159 if arg_char.len() == 1;
3160 if let hir::ExprKind::Path(ref qpath) = fun.kind;
3161 if let Some(segment) = single_segment_path(qpath);
3162 if segment.ident.name == sym!(Some);
3164 let mut applicability = Applicability::MachineApplicable;
3165 let self_ty = walk_ptrs_ty(cx.typeck_results().expr_ty_adjusted(&args[0][0]));
3167 if self_ty.kind != ty::Str {
3175 &format!("you should use the `{}` method", suggest),
3177 format!("{}{}.{}({})",
3178 if info.eq { "" } else { "!" },
3179 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
3181 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
3192 /// Checks for the `CHARS_NEXT_CMP` lint.
3193 fn lint_chars_next_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3194 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
3197 /// Checks for the `CHARS_LAST_CMP` lint.
3198 fn lint_chars_last_cmp<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3199 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
3202 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
3206 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
3207 fn lint_chars_cmp_with_unwrap<'tcx>(
3208 cx: &LateContext<'tcx>,
3209 info: &BinaryExprInfo<'_>,
3210 chain_methods: &[&str],
3211 lint: &'static Lint,
3215 if let Some(args) = method_chain_args(info.chain, chain_methods);
3216 if let hir::ExprKind::Lit(ref lit) = info.other.kind;
3217 if let ast::LitKind::Char(c) = lit.node;
3219 let mut applicability = Applicability::MachineApplicable;
3224 &format!("you should use the `{}` method", suggest),
3226 format!("{}{}.{}('{}')",
3227 if info.eq { "" } else { "!" },
3228 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
3241 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
3242 fn lint_chars_next_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3243 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
3246 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
3247 fn lint_chars_last_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3248 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
3251 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
3255 fn get_hint_if_single_char_arg(
3256 cx: &LateContext<'_>,
3257 arg: &hir::Expr<'_>,
3258 applicability: &mut Applicability,
3259 ) -> Option<String> {
3261 if let hir::ExprKind::Lit(lit) = &arg.kind;
3262 if let ast::LitKind::Str(r, style) = lit.node;
3263 let string = r.as_str();
3264 if string.len() == 1;
3266 let snip = snippet_with_applicability(cx, arg.span, &string, applicability);
3267 let ch = if let ast::StrStyle::Raw(nhash) = style {
3268 let nhash = nhash as usize;
3269 // for raw string: r##"a"##
3270 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
3272 // for regular string: "a"
3273 &snip[1..(snip.len() - 1)]
3275 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
3283 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
3284 fn lint_single_char_pattern(cx: &LateContext<'_>, _expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
3285 let mut applicability = Applicability::MachineApplicable;
3286 if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability) {
3289 SINGLE_CHAR_PATTERN,
3291 "single-character string constant used as pattern",
3292 "try using a `char` instead",
3299 /// lint for length-1 `str`s as argument for `push_str`
3300 fn lint_single_char_push_string(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3301 let mut applicability = Applicability::MachineApplicable;
3302 if let Some(extension_string) = get_hint_if_single_char_arg(cx, &args[1], &mut applicability) {
3303 let base_string_snippet = snippet_with_applicability(cx, args[0].span, "_", &mut applicability);
3304 let sugg = format!("{}.push({})", base_string_snippet, extension_string);
3307 SINGLE_CHAR_PUSH_STR,
3309 "calling `push_str()` using a single-character string literal",
3310 "consider using `push` with a character literal",
3317 /// Checks for the `USELESS_ASREF` lint.
3318 fn lint_asref(cx: &LateContext<'_>, expr: &hir::Expr<'_>, call_name: &str, as_ref_args: &[hir::Expr<'_>]) {
3319 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
3320 // check if the call is to the actual `AsRef` or `AsMut` trait
3321 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
3322 // check if the type after `as_ref` or `as_mut` is the same as before
3323 let recvr = &as_ref_args[0];
3324 let rcv_ty = cx.typeck_results().expr_ty(recvr);
3325 let res_ty = cx.typeck_results().expr_ty(expr);
3326 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
3327 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
3328 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
3329 // allow the `as_ref` or `as_mut` if it is followed by another method call
3331 if let Some(parent) = get_parent_expr(cx, expr);
3332 if let hir::ExprKind::MethodCall(_, ref span, _, _) = parent.kind;
3333 if span != &expr.span;
3339 let mut applicability = Applicability::MachineApplicable;
3344 &format!("this call to `{}` does nothing", call_name),
3346 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
3353 fn ty_has_iter_method(cx: &LateContext<'_>, self_ref_ty: Ty<'_>) -> Option<(&'static str, &'static str)> {
3354 has_iter_method(cx, self_ref_ty).map(|ty_name| {
3355 let mutbl = match self_ref_ty.kind {
3356 ty::Ref(_, _, mutbl) => mutbl,
3357 _ => unreachable!(),
3359 let method_name = match mutbl {
3360 hir::Mutability::Not => "iter",
3361 hir::Mutability::Mut => "iter_mut",
3363 (ty_name, method_name)
3367 fn lint_into_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, self_ref_ty: Ty<'_>, method_span: Span) {
3368 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
3371 if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
3377 "this `.into_iter()` call is equivalent to `.{}()` and will not move the `{}`",
3381 method_name.to_string(),
3382 Applicability::MachineApplicable,
3387 /// lint for `MaybeUninit::uninit().assume_init()` (we already have the latter)
3388 fn lint_maybe_uninit(cx: &LateContext<'_>, expr: &hir::Expr<'_>, outer: &hir::Expr<'_>) {
3390 if let hir::ExprKind::Call(ref callee, ref args) = expr.kind;
3392 if let hir::ExprKind::Path(ref path) = callee.kind;
3393 if match_qpath(path, &paths::MEM_MAYBEUNINIT_UNINIT);
3394 if !is_maybe_uninit_ty_valid(cx, cx.typeck_results().expr_ty_adjusted(outer));
3398 UNINIT_ASSUMED_INIT,
3400 "this call for this type may be undefined behavior"
3406 fn is_maybe_uninit_ty_valid(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
3408 ty::Array(ref component, _) => is_maybe_uninit_ty_valid(cx, component),
3409 ty::Tuple(ref types) => types.types().all(|ty| is_maybe_uninit_ty_valid(cx, ty)),
3410 ty::Adt(ref adt, _) => match_def_path(cx, adt.did, &paths::MEM_MAYBEUNINIT),
3415 fn lint_suspicious_map(cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
3420 "this call to `map()` won't have an effect on the call to `count()`",
3422 "make sure you did not confuse `map` with `filter` or `for_each`",
3426 /// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
3427 fn lint_option_as_ref_deref<'tcx>(
3428 cx: &LateContext<'tcx>,
3429 expr: &hir::Expr<'_>,
3430 as_ref_args: &[hir::Expr<'_>],
3431 map_args: &[hir::Expr<'_>],
3434 let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
3436 let option_ty = cx.typeck_results().expr_ty(&as_ref_args[0]);
3437 if !is_type_diagnostic_item(cx, option_ty, sym!(option_type)) {
3441 let deref_aliases: [&[&str]; 9] = [
3442 &paths::DEREF_TRAIT_METHOD,
3443 &paths::DEREF_MUT_TRAIT_METHOD,
3444 &paths::CSTRING_AS_C_STR,
3445 &paths::OS_STRING_AS_OS_STR,
3446 &paths::PATH_BUF_AS_PATH,
3447 &paths::STRING_AS_STR,
3448 &paths::STRING_AS_MUT_STR,
3449 &paths::VEC_AS_SLICE,
3450 &paths::VEC_AS_MUT_SLICE,
3453 let is_deref = match map_args[1].kind {
3454 hir::ExprKind::Path(ref expr_qpath) => cx
3455 .qpath_res(expr_qpath, map_args[1].hir_id)
3457 .map_or(false, |fun_def_id| {
3458 deref_aliases.iter().any(|path| match_def_path(cx, fun_def_id, path))
3460 hir::ExprKind::Closure(_, _, body_id, _, _) => {
3461 let closure_body = cx.tcx.hir().body(body_id);
3462 let closure_expr = remove_blocks(&closure_body.value);
3464 match &closure_expr.kind {
3465 hir::ExprKind::MethodCall(_, _, args, _) => {
3468 if let hir::ExprKind::Path(qpath) = &args[0].kind;
3469 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, args[0].hir_id);
3470 if closure_body.params[0].pat.hir_id == local_id;
3473 .expr_adjustments(&args[0])
3476 .collect::<Box<[_]>>();
3477 if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
3479 let method_did = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id).unwrap();
3480 deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
3486 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, ref inner) if same_mutability(m) => {
3488 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner1) = inner.kind;
3489 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner2) = inner1.kind;
3490 if let hir::ExprKind::Path(ref qpath) = inner2.kind;
3491 if let hir::def::Res::Local(local_id) = cx.qpath_res(qpath, inner2.hir_id);
3493 closure_body.params[0].pat.hir_id == local_id
3506 let current_method = if is_mut {
3507 format!(".as_mut().map({})", snippet(cx, map_args[1].span, ".."))
3509 format!(".as_ref().map({})", snippet(cx, map_args[1].span, ".."))
3511 let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
3512 let hint = format!("{}.{}()", snippet(cx, as_ref_args[0].span, ".."), method_hint);
3513 let suggestion = format!("try using {} instead", method_hint);
3516 "called `{0}` on an Option value. This can be done more directly \
3517 by calling `{1}` instead",
3518 current_method, hint
3522 OPTION_AS_REF_DEREF,
3527 Applicability::MachineApplicable,
3532 /// Given a `Result<T, E>` type, return its error type (`E`).
3533 fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
3535 ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym!(result_type)) => substs.types().nth(1),
3540 /// This checks whether a given type is known to implement Debug.
3541 fn has_debug_impl<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool {
3543 .get_diagnostic_item(sym::debug_trait)
3544 .map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
3549 StartsWith(&'static str),
3553 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
3554 (Convention::Eq("new"), &[SelfKind::No]),
3555 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
3556 (Convention::StartsWith("from_"), &[SelfKind::No]),
3557 (Convention::StartsWith("into_"), &[SelfKind::Value]),
3558 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
3559 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
3560 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
3563 const FN_HEADER: hir::FnHeader = hir::FnHeader {
3564 unsafety: hir::Unsafety::Normal,
3565 constness: hir::Constness::NotConst,
3566 asyncness: hir::IsAsync::NotAsync,
3567 abi: rustc_target::spec::abi::Abi::Rust,
3570 struct ShouldImplTraitCase {
3571 trait_name: &'static str,
3572 method_name: &'static str,
3574 fn_header: hir::FnHeader,
3575 // implicit self kind expected (none, self, &self, ...)
3576 self_kind: SelfKind,
3577 // checks against the output type
3578 output_type: OutType,
3579 // certain methods with explicit lifetimes can't implement the equivalent trait method
3580 lint_explicit_lifetime: bool,
3582 impl ShouldImplTraitCase {
3584 trait_name: &'static str,
3585 method_name: &'static str,
3587 fn_header: hir::FnHeader,
3588 self_kind: SelfKind,
3589 output_type: OutType,
3590 lint_explicit_lifetime: bool,
3591 ) -> ShouldImplTraitCase {
3592 ShouldImplTraitCase {
3599 lint_explicit_lifetime,
3603 fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
3604 self.lint_explicit_lifetime
3605 || !impl_item.generics.params.iter().any(|p| {
3608 hir::GenericParamKind::Lifetime {
3609 kind: hir::LifetimeParamKind::Explicit
3617 const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
3618 ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3619 ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3620 ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3621 ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3622 ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3623 ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3624 ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3625 ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3626 ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3627 ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
3628 // FIXME: default doesn't work
3629 ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
3630 ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3631 ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3632 ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3633 ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
3634 ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
3635 ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3636 ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
3637 ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
3638 ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
3639 ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
3640 ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3641 ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3642 ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3643 ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
3644 ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
3645 ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3646 ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3647 ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3648 ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
3652 const PATTERN_METHODS: [(&str, usize); 17] = [
3660 ("split_terminator", 1),
3661 ("rsplit_terminator", 1),
3666 ("match_indices", 1),
3667 ("rmatch_indices", 1),
3668 ("trim_start_matches", 1),
3669 ("trim_end_matches", 1),
3672 #[derive(Clone, Copy, PartialEq, Debug)]
3681 fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3682 fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
3683 if ty == parent_ty {
3685 } else if ty.is_box() {
3686 ty.boxed_ty() == parent_ty
3687 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
3688 if let ty::Adt(_, substs) = ty.kind {
3689 substs.types().next().map_or(false, |t| t == parent_ty)
3698 fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3699 if let ty::Ref(_, t, m) = ty.kind {
3700 return m == mutability && t == parent_ty;
3703 let trait_path = match mutability {
3704 hir::Mutability::Not => &paths::ASREF_TRAIT,
3705 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
3708 let trait_def_id = match get_trait_def_id(cx, trait_path) {
3710 None => return false,
3712 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3716 Self::Value => matches_value(cx, parent_ty, ty),
3717 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3718 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3719 Self::No => ty != parent_ty,
3724 fn description(self) -> &'static str {
3726 Self::Value => "self by value",
3727 Self::Ref => "self by reference",
3728 Self::RefMut => "self by mutable reference",
3729 Self::No => "no self",
3736 fn check(&self, other: &str) -> bool {
3738 Self::Eq(this) => this == other,
3739 Self::StartsWith(this) => other.starts_with(this) && this != other,
3744 impl fmt::Display for Convention {
3745 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
3747 Self::Eq(this) => this.fmt(f),
3748 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
3753 #[derive(Clone, Copy)]
3762 fn matches(self, cx: &LateContext<'_>, ty: &hir::FnRetTy<'_>) -> bool {
3763 let is_unit = |ty: &hir::Ty<'_>| SpanlessEq::new(cx).eq_ty_kind(&ty.kind, &hir::TyKind::Tup(&[]));
3765 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3766 (Self::Unit, &hir::FnRetTy::Return(ref ty)) if is_unit(ty) => true,
3767 (Self::Bool, &hir::FnRetTy::Return(ref ty)) if is_bool(ty) => true,
3768 (Self::Any, &hir::FnRetTy::Return(ref ty)) if !is_unit(ty) => true,
3769 (Self::Ref, &hir::FnRetTy::Return(ref ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3775 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3776 if let hir::TyKind::Path(ref p) = ty.kind {
3777 match_qpath(p, &["bool"])
3783 // Returns `true` if `expr` contains a return expression
3784 fn contains_return(expr: &hir::Expr<'_>) -> bool {
3785 struct RetCallFinder {
3789 impl<'tcx> intravisit::Visitor<'tcx> for RetCallFinder {
3790 type Map = Map<'tcx>;
3792 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
3796 if let hir::ExprKind::Ret(..) = &expr.kind {
3799 intravisit::walk_expr(self, expr);
3803 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
3804 intravisit::NestedVisitorMap::None
3808 let mut visitor = RetCallFinder { found: false };
3809 visitor.visit_expr(expr);
3813 fn check_pointer_offset(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3816 if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.typeck_results().expr_ty(&args[0]).kind;
3817 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
3820 span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
3825 fn lint_filetype_is_file(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3826 let ty = cx.typeck_results().expr_ty(&args[0]);
3828 if !match_type(cx, ty, &paths::FILE_TYPE) {
3834 let lint_unary: &str;
3835 let help_unary: &str;
3837 if let Some(parent) = get_parent_expr(cx, expr);
3838 if let hir::ExprKind::Unary(op, _) = parent.kind;
3839 if op == hir::UnOp::UnNot;
3852 let lint_msg = format!("`{}FileType::is_file()` only {} regular files", lint_unary, verb);
3853 let help_msg = format!("use `{}FileType::is_dir()` instead", help_unary);
3854 span_lint_and_help(cx, FILETYPE_IS_FILE, span, &lint_msg, None, &help_msg);
3857 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
3858 expected.constness == actual.constness
3859 && expected.unsafety == actual.unsafety
3860 && expected.asyncness == actual.asyncness