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::Span;
19 use syntax::symbol::LocalInternedString;
21 use crate::utils::sugg;
22 use crate::utils::usage::mutated_variables;
24 get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy,
25 is_ctor_function, is_expn_of, iter_input_pats, last_path_segment, match_def_path, match_qpath, match_trait_method,
26 match_type, match_var, method_calls, method_chain_args, remove_blocks, return_ty, same_tys, single_segment_path,
27 snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_sugg,
28 span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
30 use crate::utils::{paths, span_help_and_lint};
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 `_.and_then(|x| Some(y))`.
270 /// **Why is this bad?** Readability, this can be written more concisely as
273 /// **Known problems:** None
278 /// let x = Some("foo");
279 /// let _ = x.and_then(|s| Some(s.len()));
282 /// The correct use would be:
285 /// let x = Some("foo");
286 /// let _ = x.map(|s| s.len());
288 pub OPTION_AND_THEN_SOME,
290 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
293 declare_clippy_lint! {
294 /// **What it does:** Checks for usage of `_.filter(_).next()`.
296 /// **Why is this bad?** Readability, this can be written more concisely as
299 /// **Known problems:** None.
303 /// # let vec = vec![1];
304 /// vec.iter().filter(|x| **x == 0).next();
308 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
311 declare_clippy_lint! {
312 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
314 /// **Why is this bad?** Readability, this can be written more concisely as a
315 /// single method call.
317 /// **Known problems:**
321 /// let vec = vec![vec![1]];
322 /// vec.iter().map(|x| x.iter()).flatten();
326 "using combinations of `flatten` and `map` which can usually be written as a single method call"
329 declare_clippy_lint! {
330 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
331 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
333 /// **Why is this bad?** Readability, this can be written more concisely as a
334 /// single method call.
336 /// **Known problems:** Often requires a condition + Option/Iterator creation
337 /// inside the closure.
341 /// let vec = vec![1];
342 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
346 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
349 declare_clippy_lint! {
350 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
352 /// **Why is this bad?** Readability, this can be written more concisely as a
353 /// single method call.
355 /// **Known problems:** None
359 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
361 /// Can be written as
364 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
368 "using combination of `filter_map` and `next` which can usually be written as a single method call"
371 declare_clippy_lint! {
372 /// **What it does:** Checks for usage of `flat_map(|x| x)`.
374 /// **Why is this bad?** Readability, this can be written more concisely by using `flatten`.
376 /// **Known problems:** None
380 /// # let iter = vec![vec![0]].into_iter();
381 /// iter.flat_map(|x| x);
383 /// Can be written as
385 /// # let iter = vec![vec![0]].into_iter();
388 pub FLAT_MAP_IDENTITY,
390 "call to `flat_map` where `flatten` is sufficient"
393 declare_clippy_lint! {
394 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
396 /// **Why is this bad?** Readability, this can be written more concisely as a
397 /// single method call.
399 /// **Known problems:** Often requires a condition + Option/Iterator creation
400 /// inside the closure.
404 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
406 /// Can be written as
408 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
412 "using a combination of `find` and `map` can usually be written as a single method call"
415 declare_clippy_lint! {
416 /// **What it does:** Checks for an iterator search (such as `find()`,
417 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
419 /// **Why is this bad?** Readability, this can be written more concisely as
422 /// **Known problems:** None.
426 /// # let vec = vec![1];
427 /// vec.iter().find(|x| **x == 0).is_some();
431 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
434 declare_clippy_lint! {
435 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
436 /// if it starts with a given char.
438 /// **Why is this bad?** Readability, this can be written more concisely as
439 /// `_.starts_with(_)`.
441 /// **Known problems:** None.
445 /// let name = "foo";
446 /// name.chars().next() == Some('_');
450 "using `.chars().next()` to check if a string starts with a char"
453 declare_clippy_lint! {
454 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
455 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
456 /// `unwrap_or_default` instead.
458 /// **Why is this bad?** The function will always be called and potentially
459 /// allocate an object acting as the default.
461 /// **Known problems:** If the function has side-effects, not calling it will
462 /// change the semantic of the program, but you shouldn't rely on that anyway.
466 /// # let foo = Some(String::new());
467 /// foo.unwrap_or(String::new());
469 /// this can instead be written:
471 /// # let foo = Some(String::new());
472 /// foo.unwrap_or_else(String::new);
476 /// # let foo = Some(String::new());
477 /// foo.unwrap_or_default();
481 "using any `*or` method with a function call, which suggests `*or_else`"
484 declare_clippy_lint! {
485 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
486 /// etc., and suggests to use `unwrap_or_else` instead
488 /// **Why is this bad?** The function will always be called.
490 /// **Known problems:** If the function has side-effects, not calling it will
491 /// change the semantics of the program, but you shouldn't rely on that anyway.
495 /// # let foo = Some(String::new());
496 /// # let err_code = "418";
497 /// # let err_msg = "I'm a teapot";
498 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
502 /// # let foo = Some(String::new());
503 /// # let err_code = "418";
504 /// # let err_msg = "I'm a teapot";
505 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
507 /// this can instead be written:
509 /// # let foo = Some(String::new());
510 /// # let err_code = "418";
511 /// # let err_msg = "I'm a teapot";
512 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
516 "using any `expect` method with a function call"
519 declare_clippy_lint! {
520 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
522 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
523 /// generics, not for using the `clone` method on a concrete type.
525 /// **Known problems:** None.
533 "using `clone` on a `Copy` type"
536 declare_clippy_lint! {
537 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
538 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
539 /// function syntax instead (e.g., `Rc::clone(foo)`).
541 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
542 /// can obscure the fact that only the pointer is being cloned, not the underlying
547 /// # use std::rc::Rc;
548 /// let x = Rc::new(1);
551 pub CLONE_ON_REF_PTR,
553 "using 'clone' on a ref-counted pointer"
556 declare_clippy_lint! {
557 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
559 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
560 /// cloning the underlying `T`.
562 /// **Known problems:** None.
569 /// let z = y.clone();
570 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
573 pub CLONE_DOUBLE_REF,
575 "using `clone` on `&&T`"
578 declare_clippy_lint! {
579 /// **What it does:** Checks for `new` not returning `Self`.
581 /// **Why is this bad?** As a convention, `new` methods are used to make a new
582 /// instance of a type.
584 /// **Known problems:** None.
589 /// fn new(..) -> NotAFoo {
595 "not returning `Self` in a `new` method"
598 declare_clippy_lint! {
599 /// **What it does:** Checks for string methods that receive a single-character
600 /// `str` as an argument, e.g., `_.split("x")`.
602 /// **Why is this bad?** Performing these methods using a `char` is faster than
605 /// **Known problems:** Does not catch multi-byte unicode characters.
608 /// `_.split("x")` could be `_.split('x')`
609 pub SINGLE_CHAR_PATTERN,
611 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
614 declare_clippy_lint! {
615 /// **What it does:** Checks for getting the inner pointer of a temporary
618 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
619 /// as the `CString` is alive.
621 /// **Known problems:** None.
625 /// let c_str = CString::new("foo").unwrap().as_ptr();
627 /// call_some_ffi_func(c_str);
630 /// Here `c_str` point to a freed address. The correct use would be:
632 /// let c_str = CString::new("foo").unwrap();
634 /// call_some_ffi_func(c_str.as_ptr());
637 pub TEMPORARY_CSTRING_AS_PTR,
639 "getting the inner pointer of a temporary `CString`"
642 declare_clippy_lint! {
643 /// **What it does:** Checks for use of `.iter().nth()` (and the related
644 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
646 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
649 /// **Known problems:** None.
653 /// let some_vec = vec![0, 1, 2, 3];
654 /// let bad_vec = some_vec.iter().nth(3);
655 /// let bad_slice = &some_vec[..].iter().nth(3);
657 /// The correct use would be:
659 /// let some_vec = vec![0, 1, 2, 3];
660 /// let bad_vec = some_vec.get(3);
661 /// let bad_slice = &some_vec[..].get(3);
665 "using `.iter().nth()` on a standard library type with O(1) element access"
668 declare_clippy_lint! {
669 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
671 /// **Why is this bad?** `.nth(x)` is cleaner
673 /// **Known problems:** None.
677 /// let some_vec = vec![0, 1, 2, 3];
678 /// let bad_vec = some_vec.iter().skip(3).next();
679 /// let bad_slice = &some_vec[..].iter().skip(3).next();
681 /// The correct use would be:
683 /// let some_vec = vec![0, 1, 2, 3];
684 /// let bad_vec = some_vec.iter().nth(3);
685 /// let bad_slice = &some_vec[..].iter().nth(3);
689 "using `.skip(x).next()` on an iterator"
692 declare_clippy_lint! {
693 /// **What it does:** Checks for use of `.get().unwrap()` (or
694 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
696 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
699 /// **Known problems:** Not a replacement for error handling: Using either
700 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
701 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
702 /// temporary placeholder for dealing with the `Option` type, then this does
703 /// not mitigate the need for error handling. If there is a chance that `.get()`
704 /// will be `None` in your program, then it is advisable that the `None` case
705 /// is handled in a future refactor instead of using `.unwrap()` or the Index
710 /// let mut some_vec = vec![0, 1, 2, 3];
711 /// let last = some_vec.get(3).unwrap();
712 /// *some_vec.get_mut(0).unwrap() = 1;
714 /// The correct use would be:
716 /// let mut some_vec = vec![0, 1, 2, 3];
717 /// let last = some_vec[3];
722 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
725 declare_clippy_lint! {
726 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
727 /// `&str` or `String`.
729 /// **Why is this bad?** `.push_str(s)` is clearer
731 /// **Known problems:** None.
736 /// let def = String::from("def");
737 /// let mut s = String::new();
738 /// s.extend(abc.chars());
739 /// s.extend(def.chars());
741 /// The correct use would be:
744 /// let def = String::from("def");
745 /// let mut s = String::new();
747 /// s.push_str(&def);
749 pub STRING_EXTEND_CHARS,
751 "using `x.extend(s.chars())` where s is a `&str` or `String`"
754 declare_clippy_lint! {
755 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
758 /// **Why is this bad?** `.to_vec()` is clearer
760 /// **Known problems:** None.
764 /// let s = [1, 2, 3, 4, 5];
765 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
767 /// The better use would be:
769 /// let s = [1, 2, 3, 4, 5];
770 /// let s2: Vec<isize> = s.to_vec();
772 pub ITER_CLONED_COLLECT,
774 "using `.cloned().collect()` on slice to create a `Vec`"
777 declare_clippy_lint! {
778 /// **What it does:** Checks for usage of `.chars().last()` or
779 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
781 /// **Why is this bad?** Readability, this can be written more concisely as
782 /// `_.ends_with(_)`.
784 /// **Known problems:** None.
788 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
792 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
795 declare_clippy_lint! {
796 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
797 /// types before and after the call are the same.
799 /// **Why is this bad?** The call is unnecessary.
801 /// **Known problems:** None.
805 /// # fn do_stuff(x: &[i32]) {}
806 /// let x: &[i32] = &[1, 2, 3, 4, 5];
807 /// do_stuff(x.as_ref());
809 /// The correct use would be:
811 /// # fn do_stuff(x: &[i32]) {}
812 /// let x: &[i32] = &[1, 2, 3, 4, 5];
817 "using `as_ref` where the types before and after the call are the same"
820 declare_clippy_lint! {
821 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
822 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
823 /// `sum` or `product`.
825 /// **Why is this bad?** Readability.
827 /// **Known problems:** False positive in pattern guards. Will be resolved once
828 /// non-lexical lifetimes are stable.
832 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
834 /// This could be written as:
836 /// let _ = (0..3).any(|x| x > 2);
838 pub UNNECESSARY_FOLD,
840 "using `fold` when a more succinct alternative exists"
843 declare_clippy_lint! {
844 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
845 /// More specifically it checks if the closure provided is only performing one of the
846 /// filter or map operations and suggests the appropriate option.
848 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
849 /// operation is being performed.
851 /// **Known problems:** None
855 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
857 /// As there is no transformation of the argument this could be written as:
859 /// let _ = (0..3).filter(|&x| x > 2);
863 /// let _ = (0..4).filter_map(i32::checked_abs);
865 /// As there is no conditional check on the argument this could be written as:
867 /// let _ = (0..4).map(i32::checked_abs);
869 pub UNNECESSARY_FILTER_MAP,
871 "using `filter_map` when a more succinct alternative exists"
874 declare_clippy_lint! {
875 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
878 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
879 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
880 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
881 /// like calling `iter` would. Furthermore, when the standard library actually
882 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
883 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
884 /// and the code will be broken.
886 /// **Known problems:** None
891 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
893 pub INTO_ITER_ON_ARRAY,
895 "using `.into_iter()` on an array"
898 declare_clippy_lint! {
899 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
902 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
903 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
904 /// `iter_mut` directly.
906 /// **Known problems:** None
911 /// let _ = (&vec![3, 4, 5]).into_iter();
913 pub INTO_ITER_ON_REF,
915 "using `.into_iter()` on a reference"
918 declare_clippy_lint! {
919 /// **What it does:** Checks for calls to `map` followed by a `count`.
921 /// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
922 /// If the `map` call is intentional, this should be rewritten.
924 /// **Known problems:** None
929 /// let _ = (0..3).map(|x| x + 2).count();
933 "suspicious usage of map"
936 declare_lint_pass!(Methods => [
939 SHOULD_IMPLEMENT_TRAIT,
940 WRONG_SELF_CONVENTION,
941 WRONG_PUB_SELF_CONVENTION,
943 OPTION_MAP_UNWRAP_OR,
944 OPTION_MAP_UNWRAP_OR_ELSE,
945 RESULT_MAP_UNWRAP_OR_ELSE,
947 OPTION_AND_THEN_SOME,
958 TEMPORARY_CSTRING_AS_PTR,
972 UNNECESSARY_FILTER_MAP,
978 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
979 #[allow(clippy::cognitive_complexity)]
980 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
981 if in_macro(expr.span) {
985 let (method_names, arg_lists) = method_calls(expr, 2);
986 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
987 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
989 match method_names.as_slice() {
990 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
991 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
992 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
993 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
994 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
995 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
996 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
997 ["and_then", ..] => lint_option_and_then_some(cx, expr, arg_lists[0]),
998 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
999 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
1000 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
1001 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
1002 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
1003 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1004 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1005 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0]),
1006 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
1007 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
1008 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
1009 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
1010 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
1011 ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
1012 lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
1014 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
1015 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
1016 ["next", "skip"] => lint_iter_skip_next(cx, expr),
1017 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
1018 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
1019 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
1020 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
1021 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
1022 ["count", "map"] => lint_suspicious_map(cx, expr),
1027 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
1028 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1029 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1031 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
1032 if args.len() == 1 && method_call.ident.name == sym!(clone) {
1033 lint_clone_on_copy(cx, expr, &args[0], self_ty);
1034 lint_clone_on_ref_ptr(cx, expr, &args[0]);
1038 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
1039 for &(method, pos) in &PATTERN_METHODS {
1040 if method_call.ident.name.as_str() == method && args.len() > pos {
1041 lint_single_char_pattern(cx, expr, &args[pos]);
1045 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
1046 lint_into_iter(cx, expr, self_ty, *method_span);
1051 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1052 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1054 let mut info = BinaryExprInfo {
1058 eq: op.node == hir::BinOpKind::Eq,
1060 lint_binary_expr_with_method_call(cx, &mut info);
1066 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, impl_item: &'tcx hir::ImplItem) {
1067 if in_external_macro(cx.sess(), impl_item.span) {
1070 let name = impl_item.ident.name.as_str();
1071 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1072 let item = cx.tcx.hir().expect_item(parent);
1073 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1074 let ty = cx.tcx.type_of(def_id);
1076 if let hir::ImplItemKind::Method(ref sig, id) = impl_item.node;
1077 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1078 if let hir::ItemKind::Impl(_, _, _, _, None, _, _) = item.node;
1080 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1081 let method_sig = cx.tcx.fn_sig(method_def_id);
1082 let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
1084 let first_arg_ty = &method_sig.inputs().iter().next();
1086 // check conventions w.r.t. conversion method names and predicates
1087 if let Some(first_arg_ty) = first_arg_ty {
1089 if cx.access_levels.is_exported(impl_item.hir_id) {
1090 // check missing trait implementations
1091 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
1092 if name == method_name &&
1093 sig.decl.inputs.len() == n_args &&
1094 out_type.matches(cx, &sig.decl.output) &&
1095 self_kind.matches(cx, ty, first_arg_ty) {
1096 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, impl_item.span, &format!(
1097 "defining a method called `{}` on this type; consider implementing \
1098 the `{}` trait or choosing a less ambiguous name", name, trait_name));
1103 for &(ref conv, self_kinds) in &CONVENTIONS {
1104 if conv.check(&name) {
1107 .any(|k| k.matches(cx, ty, first_arg_ty)) {
1108 let lint = if item.vis.node.is_pub() {
1109 WRONG_PUB_SELF_CONVENTION
1111 WRONG_SELF_CONVENTION
1116 &format!("methods called `{}` usually take {}; consider choosing a less \
1120 .map(|k| k.description())
1121 .collect::<Vec<_>>()
1125 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1134 if let hir::ImplItemKind::Method(_, _) = impl_item.node {
1135 let ret_ty = return_ty(cx, impl_item.hir_id);
1137 // walk the return type and check for Self (this does not check associated types)
1138 for inner_type in ret_ty.walk() {
1139 if same_tys(cx, ty, inner_type) {
1144 // if return type is impl trait, check the associated types
1145 if let ty::Opaque(def_id, _) = ret_ty.sty {
1146 // one of the associated types must be Self
1147 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1149 (Predicate::Projection(poly_projection_predicate), _) => {
1150 let binder = poly_projection_predicate.ty();
1151 let associated_type = binder.skip_binder();
1153 // walk the associated type and check for Self
1154 for inner_type in associated_type.walk() {
1155 if same_tys(cx, ty, inner_type) {
1165 if name == "new" && !same_tys(cx, ret_ty, ty) {
1170 "methods called `new` usually return `Self`",
1177 /// Checks for the `OR_FUN_CALL` lint.
1178 #[allow(clippy::too_many_lines)]
1179 fn lint_or_fun_call<'a, 'tcx>(
1180 cx: &LateContext<'a, 'tcx>,
1184 args: &'tcx [hir::Expr],
1186 // Searches an expression for method calls or function calls that aren't ctors
1187 struct FunCallFinder<'a, 'tcx> {
1188 cx: &'a LateContext<'a, 'tcx>,
1192 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1193 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1194 let call_found = match &expr.node {
1195 // ignore enum and struct constructors
1196 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1197 hir::ExprKind::MethodCall(..) => true,
1202 // don't lint for constant values
1203 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1204 let promotable = self
1207 .rvalue_promotable_map(owner_def)
1208 .contains(&expr.hir_id.local_id);
1215 intravisit::walk_expr(self, expr);
1219 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1220 intravisit::NestedVisitorMap::None
1224 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1225 fn check_unwrap_or_default(
1226 cx: &LateContext<'_, '_>,
1229 self_expr: &hir::Expr,
1238 if name == "unwrap_or" {
1239 if let hir::ExprKind::Path(ref qpath) = fun.node {
1240 let path = &*last_path_segment(qpath).ident.as_str();
1242 if ["default", "new"].contains(&path) {
1243 let arg_ty = cx.tables.expr_ty(arg);
1244 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1250 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1251 let mut applicability = Applicability::MachineApplicable;
1256 &format!("use of `{}` followed by a call to `{}`", name, path),
1259 "{}.unwrap_or_default()",
1260 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1273 /// Checks for `*or(foo())`.
1274 #[allow(clippy::too_many_arguments)]
1275 fn check_general_case<'a, 'tcx>(
1276 cx: &LateContext<'a, 'tcx>,
1280 self_expr: &hir::Expr,
1281 arg: &'tcx hir::Expr,
1285 // (path, fn_has_argument, methods, suffix)
1286 let know_types: &[(&[_], _, &[_], _)] = &[
1287 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1288 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1289 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1290 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1293 // early check if the name is one we care about
1294 if know_types.iter().all(|k| !k.2.contains(&name)) {
1298 let mut finder = FunCallFinder { cx: &cx, found: false };
1299 finder.visit_expr(&arg);
1304 let self_ty = cx.tables.expr_ty(self_expr);
1306 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1307 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1309 (fn_has_arguments, poss, suffix)
1314 if !poss.contains(&name) {
1318 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1319 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1320 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1321 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1323 let span_replace_word = method_span.with_hi(span.hi());
1328 &format!("use of `{}` followed by a function call", name),
1330 format!("{}_{}({})", name, suffix, sugg),
1331 Applicability::HasPlaceholders,
1335 if args.len() == 2 {
1336 match args[1].node {
1337 hir::ExprKind::Call(ref fun, ref or_args) => {
1338 let or_has_args = !or_args.is_empty();
1339 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1352 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1359 !or_args.is_empty(),
1367 /// Checks for the `EXPECT_FUN_CALL` lint.
1368 #[allow(clippy::too_many_lines)]
1369 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1370 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1372 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1373 let mut arg_root = arg;
1375 arg_root = match &arg_root.node {
1376 hir::ExprKind::AddrOf(_, expr) => expr,
1377 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1378 if call_args.len() == 1
1379 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1381 let arg_type = cx.tables.expr_ty(&call_args[0]);
1382 let base_type = walk_ptrs_ty(arg_type);
1383 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1397 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1398 // converted to string.
1399 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1400 let arg_ty = cx.tables.expr_ty(arg);
1401 if match_type(cx, arg_ty, &paths::STRING) {
1404 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1405 if ty.sty == ty::Str {
1412 fn generate_format_arg_snippet(
1413 cx: &LateContext<'_, '_>,
1415 applicability: &mut Applicability,
1417 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1418 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1419 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1420 return format_arg_expr_tup
1422 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1431 fn is_call(node: &hir::ExprKind) -> bool {
1433 hir::ExprKind::AddrOf(_, expr) => {
1436 hir::ExprKind::Call(..)
1437 | hir::ExprKind::MethodCall(..)
1438 // These variants are debatable or require further examination
1439 | hir::ExprKind::Match(..)
1440 | hir::ExprKind::Block{ .. } => true,
1445 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1449 let receiver_type = cx.tables.expr_ty(&args[0]);
1450 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1452 } else if match_type(cx, receiver_type, &paths::RESULT) {
1458 let arg_root = get_arg_root(cx, &args[1]);
1460 let span_replace_word = method_span.with_hi(expr.span.hi());
1462 let mut applicability = Applicability::MachineApplicable;
1464 //Special handling for `format!` as arg_root
1465 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1466 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1467 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1468 let fmt_spec = &format_args[0];
1469 let fmt_args = &format_args[1];
1471 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1473 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1475 let sugg = args.join(", ");
1481 &format!("use of `{}` followed by a function call", name),
1483 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1492 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1493 if requires_to_string(cx, arg_root) {
1494 arg_root_snippet.to_mut().push_str(".to_string()");
1501 &format!("use of `{}` followed by a function call", name),
1503 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1508 /// Checks for the `CLONE_ON_COPY` lint.
1509 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1510 let ty = cx.tables.expr_ty(expr);
1511 if let ty::Ref(_, inner, _) = arg_ty.sty {
1512 if let ty::Ref(_, innermost, _) = inner.sty {
1517 "using `clone` on a double-reference; \
1518 this will copy the reference instead of cloning the inner type",
1520 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1521 let mut ty = innermost;
1523 while let ty::Ref(_, inner, _) = ty.sty {
1527 let refs: String = iter::repeat('&').take(n + 1).collect();
1528 let derefs: String = iter::repeat('*').take(n).collect();
1529 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1532 "try dereferencing it",
1533 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1534 Applicability::MaybeIncorrect,
1538 "or try being explicit about what type to clone",
1540 Applicability::MaybeIncorrect,
1545 return; // don't report clone_on_copy
1549 if is_copy(cx, ty) {
1551 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1552 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1553 match &cx.tcx.hir().get(parent) {
1554 hir::Node::Expr(parent) => match parent.node {
1555 // &*x is a nop, &x.clone() is not
1556 hir::ExprKind::AddrOf(..) |
1557 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1558 hir::ExprKind::MethodCall(..) => return,
1561 hir::Node::Stmt(stmt) => {
1562 if let hir::StmtKind::Local(ref loc) = stmt.node {
1563 if let hir::PatKind::Ref(..) = loc.pat.node {
1564 // let ref y = *x borrows x, let ref y = x.clone() does not
1572 // x.clone() might have dereferenced x, possibly through Deref impls
1573 if cx.tables.expr_ty(arg) == ty {
1574 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1576 let deref_count = cx
1578 .expr_adjustments(arg)
1581 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1588 let derefs: String = iter::repeat('*').take(deref_count).collect();
1589 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1594 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1595 if let Some((text, snip)) = snip {
1596 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1602 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1603 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1605 if let ty::Adt(_, subst) = obj_ty.sty {
1606 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1608 } else if match_type(cx, obj_ty, &paths::ARC) {
1610 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1620 "using '.clone()' on a ref-counted pointer",
1623 "{}::<{}>::clone(&{})",
1626 snippet(cx, arg.span, "_")
1628 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1633 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1635 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1636 let target = &arglists[0][0];
1637 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1638 let ref_str = if self_ty.sty == ty::Str {
1640 } else if match_type(cx, self_ty, &paths::STRING) {
1646 let mut applicability = Applicability::MachineApplicable;
1649 STRING_EXTEND_CHARS,
1651 "calling `.extend(_.chars())`",
1654 "{}.push_str({}{})",
1655 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1657 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1664 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1665 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1666 if match_type(cx, obj_ty, &paths::STRING) {
1667 lint_string_extend(cx, expr, args);
1671 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1673 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1675 if let hir::ExprKind::Path(ref path) = fun.node;
1676 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1677 if match_def_path(cx, did, &paths::CSTRING_NEW);
1681 TEMPORARY_CSTRING_AS_PTR,
1683 "you are getting the inner pointer of a temporary `CString`",
1685 db.note("that pointer will be invalid outside this expression");
1686 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1692 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1693 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1694 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1695 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1698 ITER_CLONED_COLLECT,
1700 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1703 ".to_vec()".to_string(),
1704 Applicability::MachineApplicable,
1711 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1712 fn check_fold_with_op(
1713 cx: &LateContext<'_, '_>,
1715 fold_args: &[hir::Expr],
1717 replacement_method_name: &str,
1718 replacement_has_args: bool,
1721 // Extract the body of the closure passed to fold
1722 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1723 let closure_body = cx.tcx.hir().body(body_id);
1724 let closure_expr = remove_blocks(&closure_body.value);
1726 // Check if the closure body is of the form `acc <op> some_expr(x)`
1727 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1728 if bin_op.node == op;
1730 // Extract the names of the two arguments to the closure
1731 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1732 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1734 if match_var(&*left_expr, first_arg_ident);
1735 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1737 if let hir::ExprKind::MethodCall(_, span, _) = &expr.node;
1740 let mut applicability = Applicability::MachineApplicable;
1741 let sugg = if replacement_has_args {
1743 "{replacement}(|{s}| {r})",
1744 replacement = replacement_method_name,
1745 s = second_arg_ident,
1746 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1751 replacement = replacement_method_name,
1758 span.with_hi(expr.span.hi()),
1759 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1760 "this `.fold` can be written more succinctly using another method",
1769 // Check that this is a call to Iterator::fold rather than just some function called fold
1770 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1775 fold_args.len() == 3,
1776 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1779 // Check if the first argument to .fold is a suitable literal
1780 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1782 ast::LitKind::Bool(false) => check_fold_with_op(cx, expr, fold_args, hir::BinOpKind::Or, "any", true),
1783 ast::LitKind::Bool(true) => check_fold_with_op(cx, expr, fold_args, hir::BinOpKind::And, "all", true),
1784 ast::LitKind::Int(0, _) => check_fold_with_op(cx, expr, fold_args, hir::BinOpKind::Add, "sum", false),
1785 ast::LitKind::Int(1, _) => check_fold_with_op(cx, expr, fold_args, hir::BinOpKind::Mul, "product", false),
1791 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1792 let mut_str = if is_mut { "_mut" } else { "" };
1793 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1795 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1797 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1800 return; // caller is not a type that we want to lint
1808 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1809 mut_str, caller_type
1814 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1815 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1816 // because they do not implement `IndexMut`
1817 let mut applicability = Applicability::MachineApplicable;
1818 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1819 let get_args_str = if get_args.len() > 1 {
1820 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1822 return; // not linting on a .get().unwrap() chain or variant
1825 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1826 needs_ref = get_args_str.parse::<usize>().is_ok();
1828 } else if match_type(cx, expr_ty, &paths::VEC) {
1829 needs_ref = get_args_str.parse::<usize>().is_ok();
1831 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1832 needs_ref = get_args_str.parse::<usize>().is_ok();
1834 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1837 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1841 return; // caller is not a type that we want to lint
1844 let mut span = expr.span;
1846 // Handle the case where the result is immediately dereferenced
1847 // by not requiring ref and pulling the dereference into the
1851 if let Some(parent) = get_parent_expr(cx, expr);
1852 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1859 let mut_str = if is_mut { "_mut" } else { "" };
1860 let borrow_str = if !needs_ref {
1873 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1874 mut_str, caller_type
1880 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1887 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1888 // lint if caller of skip is an Iterator
1889 if match_trait_method(cx, expr, &paths::ITERATOR) {
1894 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1899 fn derefs_to_slice<'a, 'tcx>(
1900 cx: &LateContext<'a, 'tcx>,
1901 expr: &'tcx hir::Expr,
1903 ) -> Option<&'tcx hir::Expr> {
1904 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1906 ty::Slice(_) => true,
1907 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1908 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1909 ty::Array(_, size) => size.eval_usize(cx.tcx, cx.param_env) < 32,
1910 ty::Ref(_, inner, _) => may_slice(cx, inner),
1915 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1916 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1923 ty::Slice(_) => Some(expr),
1924 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1925 ty::Ref(_, inner, _) => {
1926 if may_slice(cx, inner) {
1937 /// lint use of `unwrap()` for `Option`s and `Result`s
1938 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1939 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1941 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1942 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1943 } else if match_type(cx, obj_ty, &paths::RESULT) {
1944 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1949 if let Some((lint, kind, none_value)) = mess {
1955 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1956 using expect() to provide a better panic \
1964 /// lint use of `ok().expect()` for `Result`s
1965 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1966 // lint if the caller of `ok()` is a `Result`
1967 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1968 let result_type = cx.tables.expr_ty(&ok_args[0]);
1969 if let Some(error_type) = get_error_type(cx, result_type) {
1970 if has_debug_impl(error_type, cx) {
1975 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1982 /// lint use of `map().flatten()` for `Iterators`
1983 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1984 // lint if caller of `.map().flatten()` is an Iterator
1985 if match_trait_method(cx, expr, &paths::ITERATOR) {
1986 let msg = "called `map(..).flatten()` on an `Iterator`. \
1987 This is more succinctly expressed by calling `.flat_map(..)`";
1988 let self_snippet = snippet(cx, map_args[0].span, "..");
1989 let func_snippet = snippet(cx, map_args[1].span, "..");
1990 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1991 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1994 "try using flat_map instead",
1996 Applicability::MachineApplicable,
2002 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
2003 fn lint_map_unwrap_or_else<'a, 'tcx>(
2004 cx: &LateContext<'a, 'tcx>,
2005 expr: &'tcx hir::Expr,
2006 map_args: &'tcx [hir::Expr],
2007 unwrap_args: &'tcx [hir::Expr],
2009 // lint if the caller of `map()` is an `Option`
2010 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
2011 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
2013 if is_option || is_result {
2014 // Don't make a suggestion that may fail to compile due to mutably borrowing
2015 // the same variable twice.
2016 let map_mutated_vars = mutated_variables(&map_args[0], cx);
2017 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
2018 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
2019 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
2027 let msg = if is_option {
2028 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
2029 `map_or_else(g, f)` instead"
2031 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
2032 `ok().map_or_else(g, f)` instead"
2034 // get snippets for args to map() and unwrap_or_else()
2035 let map_snippet = snippet(cx, map_args[1].span, "..");
2036 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
2037 // lint, with note if neither arg is > 1 line and both map() and
2038 // unwrap_or_else() have the same span
2039 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
2040 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
2041 if same_span && !multiline {
2045 OPTION_MAP_UNWRAP_OR_ELSE
2047 RESULT_MAP_UNWRAP_OR_ELSE
2053 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
2056 if is_result { "ok()." } else { "" }
2059 } else if same_span && multiline {
2063 OPTION_MAP_UNWRAP_OR_ELSE
2065 RESULT_MAP_UNWRAP_OR_ELSE
2074 /// lint use of `_.map_or(None, _)` for `Option`s
2075 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
2076 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
2077 // check if the first non-self argument to map_or() is None
2078 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
2079 match_qpath(qpath, &paths::OPTION_NONE)
2084 if map_or_arg_is_none {
2086 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
2087 `and_then(f)` instead";
2088 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
2089 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
2090 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
2091 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
2094 "try using and_then instead",
2096 Applicability::MachineApplicable, // snippet
2103 /// Lint use of `_.and_then(|x| Some(y))` for `Option`s
2104 fn lint_option_and_then_some(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
2105 const LINT_MSG: &str = "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`";
2106 const NO_OP_MSG: &str = "using `Option.and_then(Some)`, which is a no-op";
2108 // Searches an return expressions in `y` in `_.and_then(|x| Some(y))`, which we don't lint
2109 struct RetCallFinder {
2113 impl<'tcx> intravisit::Visitor<'tcx> for RetCallFinder {
2114 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
2118 if let hir::ExprKind::Ret(..) = &expr.node {
2121 intravisit::walk_expr(self, expr);
2125 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
2126 intravisit::NestedVisitorMap::None
2130 let ty = cx.tables.expr_ty(&args[0]);
2131 if !match_type(cx, ty, &paths::OPTION) {
2135 match args[1].node {
2136 hir::ExprKind::Closure(_, _, body_id, closure_args_span, _) => {
2137 let closure_body = cx.tcx.hir().body(body_id);
2138 let closure_expr = remove_blocks(&closure_body.value);
2140 if let hir::ExprKind::Call(ref some_expr, ref some_args) = closure_expr.node;
2141 if let hir::ExprKind::Path(ref qpath) = some_expr.node;
2142 if match_qpath(qpath, &paths::OPTION_SOME);
2143 if some_args.len() == 1;
2145 let inner_expr = &some_args[0];
2147 let mut finder = RetCallFinder { found: false };
2148 finder.visit_expr(inner_expr);
2153 let some_inner_snip = if inner_expr.span.from_expansion() {
2154 snippet_with_macro_callsite(cx, inner_expr.span, "_")
2156 snippet(cx, inner_expr.span, "_")
2159 let closure_args_snip = snippet(cx, closure_args_span, "..");
2160 let option_snip = snippet(cx, args[0].span, "..");
2161 let note = format!("{}.map({} {})", option_snip, closure_args_snip, some_inner_snip);
2164 OPTION_AND_THEN_SOME,
2169 Applicability::MachineApplicable,
2174 // `_.and_then(Some)` case, which is no-op.
2175 hir::ExprKind::Path(ref qpath) => {
2176 if match_qpath(qpath, &paths::OPTION_SOME) {
2177 let option_snip = snippet(cx, args[0].span, "..");
2178 let note = format!("{}", option_snip);
2181 OPTION_AND_THEN_SOME,
2184 "use the expression directly",
2186 Applicability::MachineApplicable,
2194 /// lint use of `filter().next()` for `Iterators`
2195 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2196 // lint if caller of `.filter().next()` is an Iterator
2197 if match_trait_method(cx, expr, &paths::ITERATOR) {
2198 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2199 `.find(p)` instead.";
2200 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2201 if filter_snippet.lines().count() <= 1 {
2202 // add note if not multi-line
2209 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2212 span_lint(cx, FILTER_NEXT, expr.span, msg);
2217 /// lint use of `filter().map()` for `Iterators`
2218 fn lint_filter_map<'a, 'tcx>(
2219 cx: &LateContext<'a, 'tcx>,
2220 expr: &'tcx hir::Expr,
2221 _filter_args: &'tcx [hir::Expr],
2222 _map_args: &'tcx [hir::Expr],
2224 // lint if caller of `.filter().map()` is an Iterator
2225 if match_trait_method(cx, expr, &paths::ITERATOR) {
2226 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2227 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2228 span_lint(cx, FILTER_MAP, expr.span, msg);
2232 /// lint use of `filter_map().next()` for `Iterators`
2233 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2234 if match_trait_method(cx, expr, &paths::ITERATOR) {
2235 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2236 `.find_map(p)` instead.";
2237 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2238 if filter_snippet.lines().count() <= 1 {
2245 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2248 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2253 /// lint use of `find().map()` for `Iterators`
2254 fn lint_find_map<'a, 'tcx>(
2255 cx: &LateContext<'a, 'tcx>,
2256 expr: &'tcx hir::Expr,
2257 _find_args: &'tcx [hir::Expr],
2258 map_args: &'tcx [hir::Expr],
2260 // lint if caller of `.filter().map()` is an Iterator
2261 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2262 let msg = "called `find(p).map(q)` on an `Iterator`. \
2263 This is more succinctly expressed by calling `.find_map(..)` instead.";
2264 span_lint(cx, FIND_MAP, expr.span, msg);
2268 /// lint use of `filter().map()` for `Iterators`
2269 fn lint_filter_map_map<'a, 'tcx>(
2270 cx: &LateContext<'a, 'tcx>,
2271 expr: &'tcx hir::Expr,
2272 _filter_args: &'tcx [hir::Expr],
2273 _map_args: &'tcx [hir::Expr],
2275 // lint if caller of `.filter().map()` is an Iterator
2276 if match_trait_method(cx, expr, &paths::ITERATOR) {
2277 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2278 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2279 span_lint(cx, FILTER_MAP, expr.span, msg);
2283 /// lint use of `filter().flat_map()` for `Iterators`
2284 fn lint_filter_flat_map<'a, 'tcx>(
2285 cx: &LateContext<'a, 'tcx>,
2286 expr: &'tcx hir::Expr,
2287 _filter_args: &'tcx [hir::Expr],
2288 _map_args: &'tcx [hir::Expr],
2290 // lint if caller of `.filter().flat_map()` is an Iterator
2291 if match_trait_method(cx, expr, &paths::ITERATOR) {
2292 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2293 This is more succinctly expressed by calling `.flat_map(..)` \
2294 and filtering by returning an empty Iterator.";
2295 span_lint(cx, FILTER_MAP, expr.span, msg);
2299 /// lint use of `filter_map().flat_map()` for `Iterators`
2300 fn lint_filter_map_flat_map<'a, 'tcx>(
2301 cx: &LateContext<'a, 'tcx>,
2302 expr: &'tcx hir::Expr,
2303 _filter_args: &'tcx [hir::Expr],
2304 _map_args: &'tcx [hir::Expr],
2306 // lint if caller of `.filter_map().flat_map()` is an Iterator
2307 if match_trait_method(cx, expr, &paths::ITERATOR) {
2308 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2309 This is more succinctly expressed by calling `.flat_map(..)` \
2310 and filtering by returning an empty Iterator.";
2311 span_lint(cx, FILTER_MAP, expr.span, msg);
2315 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
2316 fn lint_flat_map_identity<'a, 'tcx>(
2317 cx: &LateContext<'a, 'tcx>,
2318 expr: &'tcx hir::Expr,
2319 flat_map_args: &'tcx [hir::Expr],
2321 if match_trait_method(cx, expr, &paths::ITERATOR) {
2322 let arg_node = &flat_map_args[1].node;
2324 let apply_lint = |message: &str| {
2325 if let hir::ExprKind::MethodCall(_, span, _) = &expr.node {
2329 span.with_hi(expr.span.hi()),
2332 "flatten()".to_string(),
2333 Applicability::MachineApplicable,
2339 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
2340 let body = cx.tcx.hir().body(*body_id);
2342 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.arguments[0].pat.node;
2343 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.node;
2345 if path.segments.len() == 1;
2346 if path.segments[0].ident.as_str() == binding_ident.as_str();
2349 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
2354 if let hir::ExprKind::Path(ref qpath) = arg_node;
2356 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
2359 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
2365 /// lint searching an Iterator followed by `is_some()`
2366 fn lint_search_is_some<'a, 'tcx>(
2367 cx: &LateContext<'a, 'tcx>,
2368 expr: &'tcx hir::Expr,
2369 search_method: &str,
2370 search_args: &'tcx [hir::Expr],
2371 is_some_args: &'tcx [hir::Expr],
2373 // lint if caller of search is an Iterator
2374 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2376 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2377 expressed by calling `any()`.",
2380 let search_snippet = snippet(cx, search_args[1].span, "..");
2381 if search_snippet.lines().count() <= 1 {
2382 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2383 let any_search_snippet = if_chain! {
2384 if search_method == "find";
2385 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2386 let closure_body = cx.tcx.hir().body(body_id);
2387 if let Some(closure_arg) = closure_body.arguments.get(0);
2388 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2390 Some(search_snippet.replacen('&', "", 1))
2395 // add note if not multi-line
2403 "replace `{0}({1}).is_some()` with `any({2})`",
2406 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2410 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2415 /// Used for `lint_binary_expr_with_method_call`.
2416 #[derive(Copy, Clone)]
2417 struct BinaryExprInfo<'a> {
2418 expr: &'a hir::Expr,
2419 chain: &'a hir::Expr,
2420 other: &'a hir::Expr,
2424 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2425 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2426 macro_rules! lint_with_both_lhs_and_rhs {
2427 ($func:ident, $cx:expr, $info:ident) => {
2428 if !$func($cx, $info) {
2429 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2430 if $func($cx, $info) {
2437 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2438 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2439 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2440 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2443 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2445 cx: &LateContext<'_, '_>,
2446 info: &BinaryExprInfo<'_>,
2447 chain_methods: &[&str],
2448 lint: &'static Lint,
2452 if let Some(args) = method_chain_args(info.chain, chain_methods);
2453 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2454 if arg_char.len() == 1;
2455 if let hir::ExprKind::Path(ref qpath) = fun.node;
2456 if let Some(segment) = single_segment_path(qpath);
2457 if segment.ident.name == sym!(Some);
2459 let mut applicability = Applicability::MachineApplicable;
2460 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2462 if self_ty.sty != ty::Str {
2470 &format!("you should use the `{}` method", suggest),
2472 format!("{}{}.{}({})",
2473 if info.eq { "" } else { "!" },
2474 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2476 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2487 /// Checks for the `CHARS_NEXT_CMP` lint.
2488 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2489 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2492 /// Checks for the `CHARS_LAST_CMP` lint.
2493 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2494 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2497 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2501 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2502 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2503 cx: &LateContext<'a, 'tcx>,
2504 info: &BinaryExprInfo<'_>,
2505 chain_methods: &[&str],
2506 lint: &'static Lint,
2510 if let Some(args) = method_chain_args(info.chain, chain_methods);
2511 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2512 if let ast::LitKind::Char(c) = lit.node;
2514 let mut applicability = Applicability::MachineApplicable;
2519 &format!("you should use the `{}` method", suggest),
2521 format!("{}{}.{}('{}')",
2522 if info.eq { "" } else { "!" },
2523 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2536 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2537 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2538 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2541 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2542 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2543 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2546 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2550 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2551 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2553 if let hir::ExprKind::Lit(lit) = &arg.node;
2554 if let ast::LitKind::Str(r, style) = lit.node;
2555 if r.as_str().len() == 1;
2557 let mut applicability = Applicability::MachineApplicable;
2558 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2559 let ch = if let ast::StrStyle::Raw(nhash) = style {
2560 let nhash = nhash as usize;
2561 // for raw string: r##"a"##
2562 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
2564 // for regular string: "a"
2565 &snip[1..(snip.len() - 1)]
2567 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
2570 SINGLE_CHAR_PATTERN,
2572 "single-character string constant used as pattern",
2573 "try using a char instead",
2581 /// Checks for the `USELESS_ASREF` lint.
2582 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2583 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2584 // check if the call is to the actual `AsRef` or `AsMut` trait
2585 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2586 // check if the type after `as_ref` or `as_mut` is the same as before
2587 let recvr = &as_ref_args[0];
2588 let rcv_ty = cx.tables.expr_ty(recvr);
2589 let res_ty = cx.tables.expr_ty(expr);
2590 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2591 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2592 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2593 // allow the `as_ref` or `as_mut` if it is followed by another method call
2595 if let Some(parent) = get_parent_expr(cx, expr);
2596 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2597 if span != &expr.span;
2603 let mut applicability = Applicability::MachineApplicable;
2608 &format!("this call to `{}` does nothing", call_name),
2610 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2617 fn ty_has_iter_method(
2618 cx: &LateContext<'_, '_>,
2619 self_ref_ty: Ty<'_>,
2620 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2621 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2622 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2627 let mutbl = match self_ref_ty.sty {
2628 ty::Ref(_, _, mutbl) => mutbl,
2629 _ => unreachable!(),
2631 let method_name = match mutbl {
2632 hir::MutImmutable => "iter",
2633 hir::MutMutable => "iter_mut",
2635 Some((lint, ty_name, method_name))
2641 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2642 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2645 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2651 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2655 method_name.to_string(),
2656 Applicability::MachineApplicable,
2661 fn lint_suspicious_map(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
2666 "this call to `map()` won't have an effect on the call to `count()`",
2667 "make sure you did not confuse `map` with `filter`",
2671 /// Given a `Result<T, E>` type, return its error type (`E`).
2672 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2673 if let ty::Adt(_, substs) = ty.sty {
2674 if match_type(cx, ty, &paths::RESULT) {
2675 substs.types().nth(1)
2684 /// This checks whether a given type is known to implement Debug.
2685 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2686 match cx.tcx.lang_items().debug_trait() {
2687 Some(debug) => implements_trait(cx, ty, debug, &[]),
2694 StartsWith(&'static str),
2698 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2699 (Convention::Eq("new"), &[SelfKind::No]),
2700 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2701 (Convention::StartsWith("from_"), &[SelfKind::No]),
2702 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2703 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2704 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2705 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2709 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2710 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2711 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2712 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2713 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2714 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2715 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2716 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2717 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2718 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2719 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2720 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2721 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2722 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2723 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2724 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2725 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2726 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2727 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2728 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2729 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2730 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2731 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2732 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2733 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2734 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2735 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2736 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2737 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2738 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2739 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2743 const PATTERN_METHODS: [(&str, usize); 17] = [
2751 ("split_terminator", 1),
2752 ("rsplit_terminator", 1),
2757 ("match_indices", 1),
2758 ("rmatch_indices", 1),
2759 ("trim_start_matches", 1),
2760 ("trim_end_matches", 1),
2763 #[derive(Clone, Copy, PartialEq, Debug)]
2772 fn matches<'a>(self, cx: &LateContext<'_, 'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2773 fn matches_value(parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
2774 if ty == parent_ty {
2776 } else if ty.is_box() {
2777 ty.boxed_ty() == parent_ty
2778 } else if ty.is_rc() || ty.is_arc() {
2779 if let ty::Adt(_, substs) = ty.sty {
2780 substs.types().next().map_or(false, |t| t == parent_ty)
2790 cx: &LateContext<'_, 'a>,
2791 mutability: hir::Mutability,
2795 if let ty::Ref(_, t, m) = ty.sty {
2796 return m == mutability && t == parent_ty;
2799 let trait_path = match mutability {
2800 hir::Mutability::MutImmutable => &paths::ASREF_TRAIT,
2801 hir::Mutability::MutMutable => &paths::ASMUT_TRAIT,
2804 let trait_def_id = get_trait_def_id(cx, trait_path).expect("trait def id not found");
2805 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
2809 Self::Value => matches_value(parent_ty, ty),
2811 matches_ref(cx, hir::Mutability::MutImmutable, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty)
2813 Self::RefMut => matches_ref(cx, hir::Mutability::MutMutable, parent_ty, ty),
2814 Self::No => ty != parent_ty,
2818 fn description(self) -> &'static str {
2820 Self::Value => "self by value",
2821 Self::Ref => "self by reference",
2822 Self::RefMut => "self by mutable reference",
2823 Self::No => "no self",
2829 fn check(&self, other: &str) -> bool {
2831 Self::Eq(this) => this == other,
2832 Self::StartsWith(this) => other.starts_with(this) && this != other,
2837 impl fmt::Display for Convention {
2838 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2840 Self::Eq(this) => this.fmt(f),
2841 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2846 #[derive(Clone, Copy)]
2855 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2856 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2858 (Self::Unit, &hir::DefaultReturn(_)) => true,
2859 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2860 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2861 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2862 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2868 fn is_bool(ty: &hir::Ty) -> bool {
2869 if let hir::TyKind::Path(ref p) = ty.node {
2870 match_qpath(p, &["bool"])