1 mod option_map_unwrap_or;
2 mod unnecessary_filter_map;
8 use if_chain::if_chain;
11 use rustc::hir::def::{DefKind, Res};
12 use rustc::hir::intravisit::{self, Visitor};
13 use rustc::lint::{in_external_macro, LateContext, LateLintPass, Lint, LintArray, LintContext, LintPass};
14 use rustc::ty::{self, Predicate, Ty};
15 use rustc::{declare_lint_pass, declare_tool_lint};
16 use rustc_errors::Applicability;
18 use syntax::source_map::{BytePos, Span};
19 use syntax::symbol::LocalInternedString;
21 use crate::utils::paths;
22 use crate::utils::sugg;
23 use crate::utils::usage::mutated_variables;
25 get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy,
26 is_ctor_function, is_expn_of, iter_input_pats, last_path_segment, match_def_path, match_qpath, match_trait_method,
27 match_type, match_var, method_calls, method_chain_args, remove_blocks, return_ty, same_tys, single_segment_path,
28 snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_sugg,
29 span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
32 declare_clippy_lint! {
33 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
35 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
36 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
37 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
38 /// `Allow` by default.
40 /// **Known problems:** None.
44 /// Using unwrap on an `Option`:
47 /// let opt = Some(1);
54 /// let opt = Some(1);
55 /// opt.expect("more helpful message");
57 pub OPTION_UNWRAP_USED,
59 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
62 declare_clippy_lint! {
63 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
65 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
66 /// values. Normally, you want to implement more sophisticated error handling,
67 /// and propagate errors upwards with `try!`.
69 /// Even if you want to panic on errors, not all `Error`s implement good
70 /// messages on display. Therefore, it may be beneficial to look at the places
71 /// where they may get displayed. Activate this lint to do just that.
73 /// **Known problems:** None.
76 /// Using unwrap on an `Option`:
79 /// let res: Result<usize, ()> = Ok(1);
86 /// let res: Result<usize, ()> = Ok(1);
87 /// res.expect("more helpful message");
89 pub RESULT_UNWRAP_USED,
91 "using `Result.unwrap()`, which might be better handled"
94 declare_clippy_lint! {
95 /// **What it does:** Checks for methods that should live in a trait
96 /// implementation of a `std` trait (see [llogiq's blog
97 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
98 /// information) instead of an inherent implementation.
100 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
101 /// the code, often with very little cost. Also people seeing a `mul(...)`
103 /// may expect `*` to work equally, so you should have good reason to disappoint
106 /// **Known problems:** None.
112 /// fn add(&self, other: &X) -> X {
117 pub SHOULD_IMPLEMENT_TRAIT,
119 "defining a method that should be implementing a std trait"
122 declare_clippy_lint! {
123 /// **What it does:** Checks for methods with certain name prefixes and which
124 /// doesn't match how self is taken. The actual rules are:
126 /// |Prefix |`self` taken |
127 /// |-------|----------------------|
128 /// |`as_` |`&self` or `&mut self`|
130 /// |`into_`|`self` |
131 /// |`is_` |`&self` or none |
132 /// |`to_` |`&self` |
134 /// **Why is this bad?** Consistency breeds readability. If you follow the
135 /// conventions, your users won't be surprised that they, e.g., need to supply a
136 /// mutable reference to a `as_..` function.
138 /// **Known problems:** None.
143 /// fn as_str(self) -> &str {
148 pub WRONG_SELF_CONVENTION,
150 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
153 declare_clippy_lint! {
154 /// **What it does:** This is the same as
155 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
157 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
159 /// **Known problems:** Actually *renaming* the function may break clients if
160 /// the function is part of the public interface. In that case, be mindful of
161 /// the stability guarantees you've given your users.
167 /// pub fn as_str(self) -> &'a str {
172 pub WRONG_PUB_SELF_CONVENTION,
174 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
177 declare_clippy_lint! {
178 /// **What it does:** Checks for usage of `ok().expect(..)`.
180 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
181 /// directly to get a better error message.
183 /// **Known problems:** The error type needs to implement `Debug`
187 /// x.ok().expect("why did I do this again?")
191 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
194 declare_clippy_lint! {
195 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
197 /// **Why is this bad?** Readability, this can be written more concisely as
198 /// `_.map_or(_, _)`.
200 /// **Known problems:** The order of the arguments is not in execution order
204 /// # let x = Some(1);
205 /// x.map(|a| a + 1).unwrap_or(0);
207 pub OPTION_MAP_UNWRAP_OR,
209 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`"
212 declare_clippy_lint! {
213 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
215 /// **Why is this bad?** Readability, this can be written more concisely as
216 /// `_.map_or_else(_, _)`.
218 /// **Known problems:** The order of the arguments is not in execution order.
222 /// # let x = Some(1);
223 /// # fn some_function() -> usize { 1 }
224 /// x.map(|a| a + 1).unwrap_or_else(some_function);
226 pub OPTION_MAP_UNWRAP_OR_ELSE,
228 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`"
231 declare_clippy_lint! {
232 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
234 /// **Why is this bad?** Readability, this can be written more concisely as
235 /// `result.ok().map_or_else(_, _)`.
237 /// **Known problems:** None.
241 /// # let x: Result<usize, ()> = Ok(1);
242 /// # fn some_function(foo: ()) -> usize { 1 }
243 /// x.map(|a| a + 1).unwrap_or_else(some_function);
245 pub RESULT_MAP_UNWRAP_OR_ELSE,
247 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `.ok().map_or_else(g, f)`"
250 declare_clippy_lint! {
251 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
253 /// **Why is this bad?** Readability, this can be written more concisely as
256 /// **Known problems:** The order of the arguments is not in execution order.
260 /// opt.map_or(None, |a| a + 1)
262 pub OPTION_MAP_OR_NONE,
264 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
267 declare_clippy_lint! {
268 /// **What it does:** Checks for usage of `_.filter(_).next()`.
270 /// **Why is this bad?** Readability, this can be written more concisely as
273 /// **Known problems:** None.
277 /// # let vec = vec![1];
278 /// vec.iter().filter(|x| **x == 0).next();
282 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
285 declare_clippy_lint! {
286 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
288 /// **Why is this bad?** Readability, this can be written more concisely as a
289 /// single method call.
291 /// **Known problems:**
295 /// let vec = vec![vec![1]];
296 /// vec.iter().map(|x| x.iter()).flatten();
300 "using combinations of `flatten` and `map` which can usually be written as a single method call"
303 declare_clippy_lint! {
304 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
305 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
307 /// **Why is this bad?** Readability, this can be written more concisely as a
308 /// single method call.
310 /// **Known problems:** Often requires a condition + Option/Iterator creation
311 /// inside the closure.
315 /// let vec = vec![1];
316 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
320 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
323 declare_clippy_lint! {
324 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
326 /// **Why is this bad?** Readability, this can be written more concisely as a
327 /// single method call.
329 /// **Known problems:** None
333 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
335 /// Can be written as
338 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
342 "using combination of `filter_map` and `next` which can usually be written as a single method call"
345 declare_clippy_lint! {
346 /// **What it does:** Checks for usage of `flat_map(|x| x)`.
348 /// **Why is this bad?** Readability, this can be written more concisely by using `flatten`.
350 /// **Known problems:** None
354 /// # let iter = vec![vec![0]].into_iter();
355 /// iter.flat_map(|x| x);
357 /// Can be written as
359 /// # let iter = vec![vec![0]].into_iter();
362 pub FLAT_MAP_IDENTITY,
364 "call to `flat_map` where `flatten` is sufficient"
367 declare_clippy_lint! {
368 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
370 /// **Why is this bad?** Readability, this can be written more concisely as a
371 /// single method call.
373 /// **Known problems:** Often requires a condition + Option/Iterator creation
374 /// inside the closure.
378 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
380 /// Can be written as
382 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
386 "using a combination of `find` and `map` can usually be written as a single method call"
389 declare_clippy_lint! {
390 /// **What it does:** Checks for an iterator search (such as `find()`,
391 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
393 /// **Why is this bad?** Readability, this can be written more concisely as
396 /// **Known problems:** None.
400 /// # let vec = vec![1];
401 /// vec.iter().find(|x| **x == 0).is_some();
405 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
408 declare_clippy_lint! {
409 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
410 /// if it starts with a given char.
412 /// **Why is this bad?** Readability, this can be written more concisely as
413 /// `_.starts_with(_)`.
415 /// **Known problems:** None.
419 /// let name = "foo";
420 /// name.chars().next() == Some('_');
424 "using `.chars().next()` to check if a string starts with a char"
427 declare_clippy_lint! {
428 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
429 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
430 /// `unwrap_or_default` instead.
432 /// **Why is this bad?** The function will always be called and potentially
433 /// allocate an object acting as the default.
435 /// **Known problems:** If the function has side-effects, not calling it will
436 /// change the semantic of the program, but you shouldn't rely on that anyway.
440 /// # let foo = Some(String::new());
441 /// foo.unwrap_or(String::new());
443 /// this can instead be written:
445 /// # let foo = Some(String::new());
446 /// foo.unwrap_or_else(String::new);
450 /// # let foo = Some(String::new());
451 /// foo.unwrap_or_default();
455 "using any `*or` method with a function call, which suggests `*or_else`"
458 declare_clippy_lint! {
459 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
460 /// etc., and suggests to use `unwrap_or_else` instead
462 /// **Why is this bad?** The function will always be called.
464 /// **Known problems:** If the function has side-effects, not calling it will
465 /// change the semantics of the program, but you shouldn't rely on that anyway.
469 /// # let foo = Some(String::new());
470 /// # let err_code = "418";
471 /// # let err_msg = "I'm a teapot";
472 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
476 /// # let foo = Some(String::new());
477 /// # let err_code = "418";
478 /// # let err_msg = "I'm a teapot";
479 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
481 /// this can instead be written:
483 /// # let foo = Some(String::new());
484 /// # let err_code = "418";
485 /// # let err_msg = "I'm a teapot";
486 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
490 "using any `expect` method with a function call"
493 declare_clippy_lint! {
494 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
496 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
497 /// generics, not for using the `clone` method on a concrete type.
499 /// **Known problems:** None.
507 "using `clone` on a `Copy` type"
510 declare_clippy_lint! {
511 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
512 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
513 /// function syntax instead (e.g., `Rc::clone(foo)`).
515 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
516 /// can obscure the fact that only the pointer is being cloned, not the underlying
521 /// # use std::rc::Rc;
522 /// let x = Rc::new(1);
525 pub CLONE_ON_REF_PTR,
527 "using 'clone' on a ref-counted pointer"
530 declare_clippy_lint! {
531 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
533 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
534 /// cloning the underlying `T`.
536 /// **Known problems:** None.
543 /// let z = y.clone();
544 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
547 pub CLONE_DOUBLE_REF,
549 "using `clone` on `&&T`"
552 declare_clippy_lint! {
553 /// **What it does:** Checks for `new` not returning `Self`.
555 /// **Why is this bad?** As a convention, `new` methods are used to make a new
556 /// instance of a type.
558 /// **Known problems:** None.
563 /// fn new(..) -> NotAFoo {
569 "not returning `Self` in a `new` method"
572 declare_clippy_lint! {
573 /// **What it does:** Checks for string methods that receive a single-character
574 /// `str` as an argument, e.g., `_.split("x")`.
576 /// **Why is this bad?** Performing these methods using a `char` is faster than
579 /// **Known problems:** Does not catch multi-byte unicode characters.
582 /// `_.split("x")` could be `_.split('x')`
583 pub SINGLE_CHAR_PATTERN,
585 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
588 declare_clippy_lint! {
589 /// **What it does:** Checks for getting the inner pointer of a temporary
592 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
593 /// as the `CString` is alive.
595 /// **Known problems:** None.
599 /// let c_str = CString::new("foo").unwrap().as_ptr();
601 /// call_some_ffi_func(c_str);
604 /// Here `c_str` point to a freed address. The correct use would be:
606 /// let c_str = CString::new("foo").unwrap();
608 /// call_some_ffi_func(c_str.as_ptr());
611 pub TEMPORARY_CSTRING_AS_PTR,
613 "getting the inner pointer of a temporary `CString`"
616 declare_clippy_lint! {
617 /// **What it does:** Checks for use of `.iter().nth()` (and the related
618 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
620 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
623 /// **Known problems:** None.
627 /// let some_vec = vec![0, 1, 2, 3];
628 /// let bad_vec = some_vec.iter().nth(3);
629 /// let bad_slice = &some_vec[..].iter().nth(3);
631 /// The correct use would be:
633 /// let some_vec = vec![0, 1, 2, 3];
634 /// let bad_vec = some_vec.get(3);
635 /// let bad_slice = &some_vec[..].get(3);
639 "using `.iter().nth()` on a standard library type with O(1) element access"
642 declare_clippy_lint! {
643 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
645 /// **Why is this bad?** `.nth(x)` is cleaner
647 /// **Known problems:** None.
651 /// let some_vec = vec![0, 1, 2, 3];
652 /// let bad_vec = some_vec.iter().skip(3).next();
653 /// let bad_slice = &some_vec[..].iter().skip(3).next();
655 /// The correct use would be:
657 /// let some_vec = vec![0, 1, 2, 3];
658 /// let bad_vec = some_vec.iter().nth(3);
659 /// let bad_slice = &some_vec[..].iter().nth(3);
663 "using `.skip(x).next()` on an iterator"
666 declare_clippy_lint! {
667 /// **What it does:** Checks for use of `.get().unwrap()` (or
668 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
670 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
673 /// **Known problems:** Not a replacement for error handling: Using either
674 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
675 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
676 /// temporary placeholder for dealing with the `Option` type, then this does
677 /// not mitigate the need for error handling. If there is a chance that `.get()`
678 /// will be `None` in your program, then it is advisable that the `None` case
679 /// is handled in a future refactor instead of using `.unwrap()` or the Index
684 /// let mut some_vec = vec![0, 1, 2, 3];
685 /// let last = some_vec.get(3).unwrap();
686 /// *some_vec.get_mut(0).unwrap() = 1;
688 /// The correct use would be:
690 /// let mut some_vec = vec![0, 1, 2, 3];
691 /// let last = some_vec[3];
696 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
699 declare_clippy_lint! {
700 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
701 /// `&str` or `String`.
703 /// **Why is this bad?** `.push_str(s)` is clearer
705 /// **Known problems:** None.
710 /// let def = String::from("def");
711 /// let mut s = String::new();
712 /// s.extend(abc.chars());
713 /// s.extend(def.chars());
715 /// The correct use would be:
718 /// let def = String::from("def");
719 /// let mut s = String::new();
721 /// s.push_str(&def);
723 pub STRING_EXTEND_CHARS,
725 "using `x.extend(s.chars())` where s is a `&str` or `String`"
728 declare_clippy_lint! {
729 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
732 /// **Why is this bad?** `.to_vec()` is clearer
734 /// **Known problems:** None.
738 /// let s = [1, 2, 3, 4, 5];
739 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
741 /// The better use would be:
743 /// let s = [1, 2, 3, 4, 5];
744 /// let s2: Vec<isize> = s.to_vec();
746 pub ITER_CLONED_COLLECT,
748 "using `.cloned().collect()` on slice to create a `Vec`"
751 declare_clippy_lint! {
752 /// **What it does:** Checks for usage of `.chars().last()` or
753 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
755 /// **Why is this bad?** Readability, this can be written more concisely as
756 /// `_.ends_with(_)`.
758 /// **Known problems:** None.
762 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
766 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
769 declare_clippy_lint! {
770 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
771 /// types before and after the call are the same.
773 /// **Why is this bad?** The call is unnecessary.
775 /// **Known problems:** None.
779 /// # fn do_stuff(x: &[i32]) {}
780 /// let x: &[i32] = &[1, 2, 3, 4, 5];
781 /// do_stuff(x.as_ref());
783 /// The correct use would be:
785 /// # fn do_stuff(x: &[i32]) {}
786 /// let x: &[i32] = &[1, 2, 3, 4, 5];
791 "using `as_ref` where the types before and after the call are the same"
794 declare_clippy_lint! {
795 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
796 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
797 /// `sum` or `product`.
799 /// **Why is this bad?** Readability.
801 /// **Known problems:** False positive in pattern guards. Will be resolved once
802 /// non-lexical lifetimes are stable.
806 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
808 /// This could be written as:
810 /// let _ = (0..3).any(|x| x > 2);
812 pub UNNECESSARY_FOLD,
814 "using `fold` when a more succinct alternative exists"
817 declare_clippy_lint! {
818 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
819 /// More specifically it checks if the closure provided is only performing one of the
820 /// filter or map operations and suggests the appropriate option.
822 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
823 /// operation is being performed.
825 /// **Known problems:** None
829 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
831 /// As there is no transformation of the argument this could be written as:
833 /// let _ = (0..3).filter(|&x| x > 2);
837 /// let _ = (0..4).filter_map(i32::checked_abs);
839 /// As there is no conditional check on the argument this could be written as:
841 /// let _ = (0..4).map(i32::checked_abs);
843 pub UNNECESSARY_FILTER_MAP,
845 "using `filter_map` when a more succinct alternative exists"
848 declare_clippy_lint! {
849 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
852 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
853 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
854 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
855 /// like calling `iter` would. Furthermore, when the standard library actually
856 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
857 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
858 /// and the code will be broken.
860 /// **Known problems:** None
865 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
867 pub INTO_ITER_ON_ARRAY,
869 "using `.into_iter()` on an array"
872 declare_clippy_lint! {
873 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
876 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
877 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
878 /// `iter_mut` directly.
880 /// **Known problems:** None
885 /// let _ = (&vec![3, 4, 5]).into_iter();
887 pub INTO_ITER_ON_REF,
889 "using `.into_iter()` on a reference"
892 declare_lint_pass!(Methods => [
895 SHOULD_IMPLEMENT_TRAIT,
896 WRONG_SELF_CONVENTION,
897 WRONG_PUB_SELF_CONVENTION,
899 OPTION_MAP_UNWRAP_OR,
900 OPTION_MAP_UNWRAP_OR_ELSE,
901 RESULT_MAP_UNWRAP_OR_ELSE,
913 TEMPORARY_CSTRING_AS_PTR,
927 UNNECESSARY_FILTER_MAP,
932 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
933 #[allow(clippy::cognitive_complexity)]
934 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
935 if in_macro(expr.span) {
939 let (method_names, arg_lists) = method_calls(expr, 2);
940 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
941 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
943 match method_names.as_slice() {
944 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
945 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
946 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
947 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
948 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
949 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
950 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
951 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
952 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
953 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
954 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
955 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
956 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
957 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
958 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0]),
959 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
960 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
961 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
962 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
963 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
964 ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
965 lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
967 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
968 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
969 ["next", "skip"] => lint_iter_skip_next(cx, expr),
970 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
971 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
972 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
973 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
974 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
979 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
980 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
981 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
983 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
984 if args.len() == 1 && method_call.ident.name == sym!(clone) {
985 lint_clone_on_copy(cx, expr, &args[0], self_ty);
986 lint_clone_on_ref_ptr(cx, expr, &args[0]);
990 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
991 for &(method, pos) in &PATTERN_METHODS {
992 if method_call.ident.name.as_str() == method && args.len() > pos {
993 lint_single_char_pattern(cx, expr, &args[pos]);
997 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
998 lint_into_iter(cx, expr, self_ty, *method_span);
1003 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1004 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1006 let mut info = BinaryExprInfo {
1010 eq: op.node == hir::BinOpKind::Eq,
1012 lint_binary_expr_with_method_call(cx, &mut info);
1018 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, impl_item: &'tcx hir::ImplItem) {
1019 if in_external_macro(cx.sess(), impl_item.span) {
1022 let name = impl_item.ident.name.as_str();
1023 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1024 let item = cx.tcx.hir().expect_item(parent);
1025 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1026 let ty = cx.tcx.type_of(def_id);
1028 if let hir::ImplItemKind::Method(ref sig, id) = impl_item.node;
1029 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1030 if let hir::ItemKind::Impl(_, _, _, _, None, _, _) = item.node;
1032 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1033 let method_sig = cx.tcx.fn_sig(method_def_id);
1034 let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
1036 let first_arg_ty = &method_sig.inputs().iter().next();
1038 // check conventions w.r.t. conversion method names and predicates
1039 if let Some(first_arg_ty) = first_arg_ty {
1041 if cx.access_levels.is_exported(impl_item.hir_id) {
1042 // check missing trait implementations
1043 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
1044 if name == method_name &&
1045 sig.decl.inputs.len() == n_args &&
1046 out_type.matches(cx, &sig.decl.output) &&
1047 self_kind.matches(cx, ty, first_arg_ty) {
1048 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, impl_item.span, &format!(
1049 "defining a method called `{}` on this type; consider implementing \
1050 the `{}` trait or choosing a less ambiguous name", name, trait_name));
1055 for &(ref conv, self_kinds) in &CONVENTIONS {
1056 if conv.check(&name) {
1059 .any(|k| k.matches(cx, ty, first_arg_ty)) {
1060 let lint = if item.vis.node.is_pub() {
1061 WRONG_PUB_SELF_CONVENTION
1063 WRONG_SELF_CONVENTION
1068 &format!("methods called `{}` usually take {}; consider choosing a less \
1072 .map(|k| k.description())
1073 .collect::<Vec<_>>()
1077 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1086 if let hir::ImplItemKind::Method(_, _) = impl_item.node {
1087 let ret_ty = return_ty(cx, impl_item.hir_id);
1089 // walk the return type and check for Self (this does not check associated types)
1090 for inner_type in ret_ty.walk() {
1091 if same_tys(cx, ty, inner_type) {
1096 // if return type is impl trait, check the associated types
1097 if let ty::Opaque(def_id, _) = ret_ty.sty {
1098 // one of the associated types must be Self
1099 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1101 (Predicate::Projection(poly_projection_predicate), _) => {
1102 let binder = poly_projection_predicate.ty();
1103 let associated_type = binder.skip_binder();
1105 // walk the associated type and check for Self
1106 for inner_type in associated_type.walk() {
1107 if same_tys(cx, ty, inner_type) {
1117 if name == "new" && !same_tys(cx, ret_ty, ty) {
1122 "methods called `new` usually return `Self`",
1129 /// Checks for the `OR_FUN_CALL` lint.
1130 #[allow(clippy::too_many_lines)]
1131 fn lint_or_fun_call<'a, 'tcx>(
1132 cx: &LateContext<'a, 'tcx>,
1136 args: &'tcx [hir::Expr],
1138 // Searches an expression for method calls or function calls that aren't ctors
1139 struct FunCallFinder<'a, 'tcx> {
1140 cx: &'a LateContext<'a, 'tcx>,
1144 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1145 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1146 let call_found = match &expr.node {
1147 // ignore enum and struct constructors
1148 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1149 hir::ExprKind::MethodCall(..) => true,
1154 // don't lint for constant values
1155 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1156 let promotable = self
1159 .rvalue_promotable_map(owner_def)
1160 .contains(&expr.hir_id.local_id);
1167 intravisit::walk_expr(self, expr);
1171 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1172 intravisit::NestedVisitorMap::None
1176 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1177 fn check_unwrap_or_default(
1178 cx: &LateContext<'_, '_>,
1181 self_expr: &hir::Expr,
1190 if name == "unwrap_or" {
1191 if let hir::ExprKind::Path(ref qpath) = fun.node {
1192 let path = &*last_path_segment(qpath).ident.as_str();
1194 if ["default", "new"].contains(&path) {
1195 let arg_ty = cx.tables.expr_ty(arg);
1196 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1202 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1203 let mut applicability = Applicability::MachineApplicable;
1208 &format!("use of `{}` followed by a call to `{}`", name, path),
1211 "{}.unwrap_or_default()",
1212 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1225 /// Checks for `*or(foo())`.
1226 #[allow(clippy::too_many_arguments)]
1227 fn check_general_case<'a, 'tcx>(
1228 cx: &LateContext<'a, 'tcx>,
1232 self_expr: &hir::Expr,
1233 arg: &'tcx hir::Expr,
1237 // (path, fn_has_argument, methods, suffix)
1238 let know_types: &[(&[_], _, &[_], _)] = &[
1239 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1240 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1241 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1242 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1245 // early check if the name is one we care about
1246 if know_types.iter().all(|k| !k.2.contains(&name)) {
1250 let mut finder = FunCallFinder { cx: &cx, found: false };
1251 finder.visit_expr(&arg);
1256 let self_ty = cx.tables.expr_ty(self_expr);
1258 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1259 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1261 (fn_has_arguments, poss, suffix)
1266 if !poss.contains(&name) {
1270 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1271 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1272 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1273 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1275 let span_replace_word = method_span.with_hi(span.hi());
1280 &format!("use of `{}` followed by a function call", name),
1282 format!("{}_{}({})", name, suffix, sugg),
1283 Applicability::HasPlaceholders,
1287 if args.len() == 2 {
1288 match args[1].node {
1289 hir::ExprKind::Call(ref fun, ref or_args) => {
1290 let or_has_args = !or_args.is_empty();
1291 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1304 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1311 !or_args.is_empty(),
1319 /// Checks for the `EXPECT_FUN_CALL` lint.
1320 #[allow(clippy::too_many_lines)]
1321 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1322 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1324 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1325 let mut arg_root = arg;
1327 arg_root = match &arg_root.node {
1328 hir::ExprKind::AddrOf(_, expr) => expr,
1329 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1330 if call_args.len() == 1
1331 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1333 let arg_type = cx.tables.expr_ty(&call_args[0]);
1334 let base_type = walk_ptrs_ty(arg_type);
1335 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1349 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1350 // converted to string.
1351 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1352 let arg_ty = cx.tables.expr_ty(arg);
1353 if match_type(cx, arg_ty, &paths::STRING) {
1356 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1357 if ty.sty == ty::Str {
1364 fn generate_format_arg_snippet(
1365 cx: &LateContext<'_, '_>,
1367 applicability: &mut Applicability,
1369 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1370 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1371 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1372 return format_arg_expr_tup
1374 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1383 fn is_call(node: &hir::ExprKind) -> bool {
1385 hir::ExprKind::AddrOf(_, expr) => {
1388 hir::ExprKind::Call(..)
1389 | hir::ExprKind::MethodCall(..)
1390 // These variants are debatable or require further examination
1391 | hir::ExprKind::Match(..)
1392 | hir::ExprKind::Block{ .. } => true,
1397 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1401 let receiver_type = cx.tables.expr_ty(&args[0]);
1402 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1404 } else if match_type(cx, receiver_type, &paths::RESULT) {
1410 let arg_root = get_arg_root(cx, &args[1]);
1412 let span_replace_word = method_span.with_hi(expr.span.hi());
1414 let mut applicability = Applicability::MachineApplicable;
1416 //Special handling for `format!` as arg_root
1417 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1418 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1419 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1420 let fmt_spec = &format_args[0];
1421 let fmt_args = &format_args[1];
1423 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1425 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1427 let sugg = args.join(", ");
1433 &format!("use of `{}` followed by a function call", name),
1435 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1444 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1445 if requires_to_string(cx, arg_root) {
1446 arg_root_snippet.to_mut().push_str(".to_string()");
1453 &format!("use of `{}` followed by a function call", name),
1455 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1460 /// Checks for the `CLONE_ON_COPY` lint.
1461 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1462 let ty = cx.tables.expr_ty(expr);
1463 if let ty::Ref(_, inner, _) = arg_ty.sty {
1464 if let ty::Ref(_, innermost, _) = inner.sty {
1469 "using `clone` on a double-reference; \
1470 this will copy the reference instead of cloning the inner type",
1472 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1473 let mut ty = innermost;
1475 while let ty::Ref(_, inner, _) = ty.sty {
1479 let refs: String = iter::repeat('&').take(n + 1).collect();
1480 let derefs: String = iter::repeat('*').take(n).collect();
1481 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1484 "try dereferencing it",
1485 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1486 Applicability::MaybeIncorrect,
1490 "or try being explicit about what type to clone",
1492 Applicability::MaybeIncorrect,
1497 return; // don't report clone_on_copy
1501 if is_copy(cx, ty) {
1503 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1504 // x.clone() might have dereferenced x, possibly through Deref impls
1505 if cx.tables.expr_ty(arg) == ty {
1506 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1508 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1509 match cx.tcx.hir().get(parent) {
1510 hir::Node::Expr(parent) => match parent.node {
1511 // &*x is a nop, &x.clone() is not
1512 hir::ExprKind::AddrOf(..) |
1513 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1514 hir::ExprKind::MethodCall(..) => return,
1517 hir::Node::Stmt(stmt) => {
1518 if let hir::StmtKind::Local(ref loc) = stmt.node {
1519 if let hir::PatKind::Ref(..) = loc.pat.node {
1520 // let ref y = *x borrows x, let ref y = x.clone() does not
1528 let deref_count = cx
1530 .expr_adjustments(arg)
1533 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1540 let derefs: String = iter::repeat('*').take(deref_count).collect();
1541 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1546 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1547 if let Some((text, snip)) = snip {
1548 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1554 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1555 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1557 if let ty::Adt(_, subst) = obj_ty.sty {
1558 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1560 } else if match_type(cx, obj_ty, &paths::ARC) {
1562 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1572 "using '.clone()' on a ref-counted pointer",
1575 "{}::<{}>::clone(&{})",
1578 snippet(cx, arg.span, "_")
1580 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1585 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1587 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1588 let target = &arglists[0][0];
1589 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1590 let ref_str = if self_ty.sty == ty::Str {
1592 } else if match_type(cx, self_ty, &paths::STRING) {
1598 let mut applicability = Applicability::MachineApplicable;
1601 STRING_EXTEND_CHARS,
1603 "calling `.extend(_.chars())`",
1606 "{}.push_str({}{})",
1607 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1609 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1616 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1617 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1618 if match_type(cx, obj_ty, &paths::STRING) {
1619 lint_string_extend(cx, expr, args);
1623 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1625 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1627 if let hir::ExprKind::Path(ref path) = fun.node;
1628 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1629 if match_def_path(cx, did, &paths::CSTRING_NEW);
1633 TEMPORARY_CSTRING_AS_PTR,
1635 "you are getting the inner pointer of a temporary `CString`",
1637 db.note("that pointer will be invalid outside this expression");
1638 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1644 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1645 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1646 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1647 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1650 ITER_CLONED_COLLECT,
1652 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1655 ".to_vec()".to_string(),
1656 Applicability::MachineApplicable,
1663 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1664 fn check_fold_with_op(
1665 cx: &LateContext<'_, '_>,
1666 fold_args: &[hir::Expr],
1668 replacement_method_name: &str,
1669 replacement_has_args: bool,
1672 // Extract the body of the closure passed to fold
1673 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1674 let closure_body = cx.tcx.hir().body(body_id);
1675 let closure_expr = remove_blocks(&closure_body.value);
1677 // Check if the closure body is of the form `acc <op> some_expr(x)`
1678 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1679 if bin_op.node == op;
1681 // Extract the names of the two arguments to the closure
1682 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1683 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1685 if match_var(&*left_expr, first_arg_ident);
1686 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1689 // Span containing `.fold(...)`
1690 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1691 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1693 let mut applicability = Applicability::MachineApplicable;
1694 let sugg = if replacement_has_args {
1696 ".{replacement}(|{s}| {r})",
1697 replacement = replacement_method_name,
1698 s = second_arg_ident,
1699 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1704 replacement = replacement_method_name,
1712 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1713 "this `.fold` can be written more succinctly using another method",
1722 // Check that this is a call to Iterator::fold rather than just some function called fold
1723 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1728 fold_args.len() == 3,
1729 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1732 // Check if the first argument to .fold is a suitable literal
1733 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1735 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1736 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1737 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1738 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1744 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1745 let mut_str = if is_mut { "_mut" } else { "" };
1746 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1748 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1750 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1753 return; // caller is not a type that we want to lint
1761 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1762 mut_str, caller_type
1767 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1768 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1769 // because they do not implement `IndexMut`
1770 let mut applicability = Applicability::MachineApplicable;
1771 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1772 let get_args_str = if get_args.len() > 1 {
1773 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1775 return; // not linting on a .get().unwrap() chain or variant
1778 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1779 needs_ref = get_args_str.parse::<usize>().is_ok();
1781 } else if match_type(cx, expr_ty, &paths::VEC) {
1782 needs_ref = get_args_str.parse::<usize>().is_ok();
1784 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1785 needs_ref = get_args_str.parse::<usize>().is_ok();
1787 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1790 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1794 return; // caller is not a type that we want to lint
1797 let mut span = expr.span;
1799 // Handle the case where the result is immediately dereferenced
1800 // by not requiring ref and pulling the dereference into the
1804 if let Some(parent) = get_parent_expr(cx, expr);
1805 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1812 let mut_str = if is_mut { "_mut" } else { "" };
1813 let borrow_str = if !needs_ref {
1826 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1827 mut_str, caller_type
1833 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1840 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1841 // lint if caller of skip is an Iterator
1842 if match_trait_method(cx, expr, &paths::ITERATOR) {
1847 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1852 fn derefs_to_slice<'a, 'tcx>(
1853 cx: &LateContext<'a, 'tcx>,
1854 expr: &'tcx hir::Expr,
1856 ) -> Option<&'tcx hir::Expr> {
1857 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1859 ty::Slice(_) => true,
1860 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1861 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1862 ty::Array(_, size) => size.eval_usize(cx.tcx, cx.param_env) < 32,
1863 ty::Ref(_, inner, _) => may_slice(cx, inner),
1868 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1869 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1876 ty::Slice(_) => Some(expr),
1877 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1878 ty::Ref(_, inner, _) => {
1879 if may_slice(cx, inner) {
1890 /// lint use of `unwrap()` for `Option`s and `Result`s
1891 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1892 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1894 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1895 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1896 } else if match_type(cx, obj_ty, &paths::RESULT) {
1897 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1902 if let Some((lint, kind, none_value)) = mess {
1908 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1909 using expect() to provide a better panic \
1917 /// lint use of `ok().expect()` for `Result`s
1918 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1919 // lint if the caller of `ok()` is a `Result`
1920 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1921 let result_type = cx.tables.expr_ty(&ok_args[0]);
1922 if let Some(error_type) = get_error_type(cx, result_type) {
1923 if has_debug_impl(error_type, cx) {
1928 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1935 /// lint use of `map().flatten()` for `Iterators`
1936 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1937 // lint if caller of `.map().flatten()` is an Iterator
1938 if match_trait_method(cx, expr, &paths::ITERATOR) {
1939 let msg = "called `map(..).flatten()` on an `Iterator`. \
1940 This is more succinctly expressed by calling `.flat_map(..)`";
1941 let self_snippet = snippet(cx, map_args[0].span, "..");
1942 let func_snippet = snippet(cx, map_args[1].span, "..");
1943 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1944 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1947 "try using flat_map instead",
1949 Applicability::MachineApplicable,
1955 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1956 fn lint_map_unwrap_or_else<'a, 'tcx>(
1957 cx: &LateContext<'a, 'tcx>,
1958 expr: &'tcx hir::Expr,
1959 map_args: &'tcx [hir::Expr],
1960 unwrap_args: &'tcx [hir::Expr],
1962 // lint if the caller of `map()` is an `Option`
1963 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1964 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1966 if is_option || is_result {
1967 // Don't make a suggestion that may fail to compile due to mutably borrowing
1968 // the same variable twice.
1969 let map_mutated_vars = mutated_variables(&map_args[0], cx);
1970 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
1971 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
1972 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
1980 let msg = if is_option {
1981 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1982 `map_or_else(g, f)` instead"
1984 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1985 `ok().map_or_else(g, f)` instead"
1987 // get snippets for args to map() and unwrap_or_else()
1988 let map_snippet = snippet(cx, map_args[1].span, "..");
1989 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1990 // lint, with note if neither arg is > 1 line and both map() and
1991 // unwrap_or_else() have the same span
1992 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1993 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1994 if same_span && !multiline {
1998 OPTION_MAP_UNWRAP_OR_ELSE
2000 RESULT_MAP_UNWRAP_OR_ELSE
2006 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
2009 if is_result { "ok()." } else { "" }
2012 } else if same_span && multiline {
2016 OPTION_MAP_UNWRAP_OR_ELSE
2018 RESULT_MAP_UNWRAP_OR_ELSE
2027 /// lint use of `_.map_or(None, _)` for `Option`s
2028 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
2029 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
2030 // check if the first non-self argument to map_or() is None
2031 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
2032 match_qpath(qpath, &paths::OPTION_NONE)
2037 if map_or_arg_is_none {
2039 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
2040 `and_then(f)` instead";
2041 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
2042 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
2043 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
2044 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
2047 "try using and_then instead",
2049 Applicability::MachineApplicable, // snippet
2056 /// lint use of `filter().next()` for `Iterators`
2057 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2058 // lint if caller of `.filter().next()` is an Iterator
2059 if match_trait_method(cx, expr, &paths::ITERATOR) {
2060 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2061 `.find(p)` instead.";
2062 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2063 if filter_snippet.lines().count() <= 1 {
2064 // add note if not multi-line
2071 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2074 span_lint(cx, FILTER_NEXT, expr.span, msg);
2079 /// lint use of `filter().map()` for `Iterators`
2080 fn lint_filter_map<'a, 'tcx>(
2081 cx: &LateContext<'a, 'tcx>,
2082 expr: &'tcx hir::Expr,
2083 _filter_args: &'tcx [hir::Expr],
2084 _map_args: &'tcx [hir::Expr],
2086 // lint if caller of `.filter().map()` is an Iterator
2087 if match_trait_method(cx, expr, &paths::ITERATOR) {
2088 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2089 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2090 span_lint(cx, FILTER_MAP, expr.span, msg);
2094 /// lint use of `filter_map().next()` for `Iterators`
2095 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2096 if match_trait_method(cx, expr, &paths::ITERATOR) {
2097 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2098 `.find_map(p)` instead.";
2099 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2100 if filter_snippet.lines().count() <= 1 {
2107 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2110 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2115 /// lint use of `find().map()` for `Iterators`
2116 fn lint_find_map<'a, 'tcx>(
2117 cx: &LateContext<'a, 'tcx>,
2118 expr: &'tcx hir::Expr,
2119 _find_args: &'tcx [hir::Expr],
2120 map_args: &'tcx [hir::Expr],
2122 // lint if caller of `.filter().map()` is an Iterator
2123 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2124 let msg = "called `find(p).map(q)` on an `Iterator`. \
2125 This is more succinctly expressed by calling `.find_map(..)` instead.";
2126 span_lint(cx, FIND_MAP, expr.span, msg);
2130 /// lint use of `filter().map()` for `Iterators`
2131 fn lint_filter_map_map<'a, 'tcx>(
2132 cx: &LateContext<'a, 'tcx>,
2133 expr: &'tcx hir::Expr,
2134 _filter_args: &'tcx [hir::Expr],
2135 _map_args: &'tcx [hir::Expr],
2137 // lint if caller of `.filter().map()` is an Iterator
2138 if match_trait_method(cx, expr, &paths::ITERATOR) {
2139 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2140 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2141 span_lint(cx, FILTER_MAP, expr.span, msg);
2145 /// lint use of `filter().flat_map()` for `Iterators`
2146 fn lint_filter_flat_map<'a, 'tcx>(
2147 cx: &LateContext<'a, 'tcx>,
2148 expr: &'tcx hir::Expr,
2149 _filter_args: &'tcx [hir::Expr],
2150 _map_args: &'tcx [hir::Expr],
2152 // lint if caller of `.filter().flat_map()` is an Iterator
2153 if match_trait_method(cx, expr, &paths::ITERATOR) {
2154 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2155 This is more succinctly expressed by calling `.flat_map(..)` \
2156 and filtering by returning an empty Iterator.";
2157 span_lint(cx, FILTER_MAP, expr.span, msg);
2161 /// lint use of `filter_map().flat_map()` for `Iterators`
2162 fn lint_filter_map_flat_map<'a, 'tcx>(
2163 cx: &LateContext<'a, 'tcx>,
2164 expr: &'tcx hir::Expr,
2165 _filter_args: &'tcx [hir::Expr],
2166 _map_args: &'tcx [hir::Expr],
2168 // lint if caller of `.filter_map().flat_map()` is an Iterator
2169 if match_trait_method(cx, expr, &paths::ITERATOR) {
2170 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2171 This is more succinctly expressed by calling `.flat_map(..)` \
2172 and filtering by returning an empty Iterator.";
2173 span_lint(cx, FILTER_MAP, expr.span, msg);
2177 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
2178 fn lint_flat_map_identity<'a, 'tcx>(
2179 cx: &LateContext<'a, 'tcx>,
2180 expr: &'tcx hir::Expr,
2181 flat_map_args: &'tcx [hir::Expr],
2183 if match_trait_method(cx, expr, &paths::ITERATOR) {
2184 let arg_node = &flat_map_args[1].node;
2186 let apply_lint = |message: &str| {
2187 if let hir::ExprKind::MethodCall(_, span, _) = &expr.node {
2191 span.with_hi(expr.span.hi()),
2194 "flatten()".to_string(),
2195 Applicability::MachineApplicable,
2201 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
2202 let body = cx.tcx.hir().body(*body_id);
2204 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.arguments[0].pat.node;
2205 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.node;
2207 if path.segments.len() == 1;
2208 if path.segments[0].ident.as_str() == binding_ident.as_str();
2211 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
2216 if let hir::ExprKind::Path(ref qpath) = arg_node;
2218 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
2221 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
2227 /// lint searching an Iterator followed by `is_some()`
2228 fn lint_search_is_some<'a, 'tcx>(
2229 cx: &LateContext<'a, 'tcx>,
2230 expr: &'tcx hir::Expr,
2231 search_method: &str,
2232 search_args: &'tcx [hir::Expr],
2233 is_some_args: &'tcx [hir::Expr],
2235 // lint if caller of search is an Iterator
2236 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2238 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2239 expressed by calling `any()`.",
2242 let search_snippet = snippet(cx, search_args[1].span, "..");
2243 if search_snippet.lines().count() <= 1 {
2244 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2245 let any_search_snippet = if_chain! {
2246 if search_method == "find";
2247 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2248 let closure_body = cx.tcx.hir().body(body_id);
2249 if let Some(closure_arg) = closure_body.arguments.get(0);
2250 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2252 Some(search_snippet.replacen('&', "", 1))
2257 // add note if not multi-line
2265 "replace `{0}({1}).is_some()` with `any({2})`",
2268 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2272 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2277 /// Used for `lint_binary_expr_with_method_call`.
2278 #[derive(Copy, Clone)]
2279 struct BinaryExprInfo<'a> {
2280 expr: &'a hir::Expr,
2281 chain: &'a hir::Expr,
2282 other: &'a hir::Expr,
2286 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2287 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2288 macro_rules! lint_with_both_lhs_and_rhs {
2289 ($func:ident, $cx:expr, $info:ident) => {
2290 if !$func($cx, $info) {
2291 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2292 if $func($cx, $info) {
2299 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2300 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2301 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2302 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2305 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2307 cx: &LateContext<'_, '_>,
2308 info: &BinaryExprInfo<'_>,
2309 chain_methods: &[&str],
2310 lint: &'static Lint,
2314 if let Some(args) = method_chain_args(info.chain, chain_methods);
2315 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2316 if arg_char.len() == 1;
2317 if let hir::ExprKind::Path(ref qpath) = fun.node;
2318 if let Some(segment) = single_segment_path(qpath);
2319 if segment.ident.name == sym!(Some);
2321 let mut applicability = Applicability::MachineApplicable;
2322 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2324 if self_ty.sty != ty::Str {
2332 &format!("you should use the `{}` method", suggest),
2334 format!("{}{}.{}({})",
2335 if info.eq { "" } else { "!" },
2336 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2338 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2349 /// Checks for the `CHARS_NEXT_CMP` lint.
2350 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2351 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2354 /// Checks for the `CHARS_LAST_CMP` lint.
2355 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2356 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2359 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2363 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2364 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2365 cx: &LateContext<'a, 'tcx>,
2366 info: &BinaryExprInfo<'_>,
2367 chain_methods: &[&str],
2368 lint: &'static Lint,
2372 if let Some(args) = method_chain_args(info.chain, chain_methods);
2373 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2374 if let ast::LitKind::Char(c) = lit.node;
2376 let mut applicability = Applicability::MachineApplicable;
2381 &format!("you should use the `{}` method", suggest),
2383 format!("{}{}.{}('{}')",
2384 if info.eq { "" } else { "!" },
2385 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2398 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2399 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2400 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2403 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2404 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2405 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2408 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2412 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2413 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2415 if let hir::ExprKind::Lit(lit) = &arg.node;
2416 if let ast::LitKind::Str(r, style) = lit.node;
2417 if r.as_str().len() == 1;
2419 let mut applicability = Applicability::MachineApplicable;
2420 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2421 let ch = if let ast::StrStyle::Raw(nhash) = style {
2422 let nhash = nhash as usize;
2423 // for raw string: r##"a"##
2424 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
2426 // for regular string: "a"
2427 &snip[1..(snip.len() - 1)]
2429 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
2432 SINGLE_CHAR_PATTERN,
2434 "single-character string constant used as pattern",
2435 "try using a char instead",
2443 /// Checks for the `USELESS_ASREF` lint.
2444 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2445 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2446 // check if the call is to the actual `AsRef` or `AsMut` trait
2447 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2448 // check if the type after `as_ref` or `as_mut` is the same as before
2449 let recvr = &as_ref_args[0];
2450 let rcv_ty = cx.tables.expr_ty(recvr);
2451 let res_ty = cx.tables.expr_ty(expr);
2452 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2453 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2454 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2455 // allow the `as_ref` or `as_mut` if it is followed by another method call
2457 if let Some(parent) = get_parent_expr(cx, expr);
2458 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2459 if span != &expr.span;
2465 let mut applicability = Applicability::MachineApplicable;
2470 &format!("this call to `{}` does nothing", call_name),
2472 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2479 fn ty_has_iter_method(
2480 cx: &LateContext<'_, '_>,
2481 self_ref_ty: Ty<'_>,
2482 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2483 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2484 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2489 let mutbl = match self_ref_ty.sty {
2490 ty::Ref(_, _, mutbl) => mutbl,
2491 _ => unreachable!(),
2493 let method_name = match mutbl {
2494 hir::MutImmutable => "iter",
2495 hir::MutMutable => "iter_mut",
2497 Some((lint, ty_name, method_name))
2503 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2504 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2507 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2513 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2517 method_name.to_string(),
2518 Applicability::MachineApplicable,
2523 /// Given a `Result<T, E>` type, return its error type (`E`).
2524 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2525 if let ty::Adt(_, substs) = ty.sty {
2526 if match_type(cx, ty, &paths::RESULT) {
2527 substs.types().nth(1)
2536 /// This checks whether a given type is known to implement Debug.
2537 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2538 match cx.tcx.lang_items().debug_trait() {
2539 Some(debug) => implements_trait(cx, ty, debug, &[]),
2546 StartsWith(&'static str),
2550 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2551 (Convention::Eq("new"), &[SelfKind::No]),
2552 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2553 (Convention::StartsWith("from_"), &[SelfKind::No]),
2554 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2555 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2556 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2557 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2561 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2562 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2563 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2564 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2565 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2566 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2567 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2568 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2569 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2570 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2571 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2572 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2573 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2574 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2575 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2576 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2577 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2578 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2579 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2580 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2581 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2582 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2583 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2584 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2585 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2586 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2587 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2588 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2589 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2590 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2591 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2595 const PATTERN_METHODS: [(&str, usize); 17] = [
2603 ("split_terminator", 1),
2604 ("rsplit_terminator", 1),
2609 ("match_indices", 1),
2610 ("rmatch_indices", 1),
2611 ("trim_start_matches", 1),
2612 ("trim_end_matches", 1),
2615 #[derive(Clone, Copy, PartialEq, Debug)]
2624 fn matches<'a>(self, cx: &LateContext<'_, 'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2625 fn matches_value(parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
2626 if ty == parent_ty {
2628 } else if ty.is_box() {
2629 ty.boxed_ty() == parent_ty
2630 } else if ty.is_rc() || ty.is_arc() {
2631 if let ty::Adt(_, substs) = ty.sty {
2632 substs.types().next().map_or(false, |t| t == parent_ty)
2642 cx: &LateContext<'_, 'a>,
2643 mutability: hir::Mutability,
2647 if let ty::Ref(_, t, m) = ty.sty {
2648 return m == mutability && t == parent_ty;
2651 let trait_path = match mutability {
2652 hir::Mutability::MutImmutable => &paths::ASREF_TRAIT,
2653 hir::Mutability::MutMutable => &paths::ASMUT_TRAIT,
2656 let trait_def_id = get_trait_def_id(cx, trait_path).expect("trait def id not found");
2657 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
2661 Self::Value => matches_value(parent_ty, ty),
2663 matches_ref(cx, hir::Mutability::MutImmutable, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty)
2665 Self::RefMut => matches_ref(cx, hir::Mutability::MutMutable, parent_ty, ty),
2666 Self::No => ty != parent_ty,
2670 fn description(self) -> &'static str {
2672 Self::Value => "self by value",
2673 Self::Ref => "self by reference",
2674 Self::RefMut => "self by mutable reference",
2675 Self::No => "no self",
2681 fn check(&self, other: &str) -> bool {
2683 Self::Eq(this) => this == other,
2684 Self::StartsWith(this) => other.starts_with(this) && this != other,
2689 impl fmt::Display for Convention {
2690 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2692 Self::Eq(this) => this.fmt(f),
2693 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2698 #[derive(Clone, Copy)]
2707 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2708 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2710 (Self::Unit, &hir::DefaultReturn(_)) => true,
2711 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2712 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2713 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2714 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2720 fn is_bool(ty: &hir::Ty) -> bool {
2721 if let hir::TyKind::Path(ref p) = ty.node {
2722 match_qpath(p, &["bool"])