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, is_self, is_self_ty, iter_input_pats, last_path_segment, match_def_path, match_path,
27 match_qpath, match_trait_method, match_type, match_var, method_calls, method_chain_args, remove_blocks, return_ty,
28 same_tys, single_segment_path, snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint,
29 span_lint_and_sugg, 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 /// iter.flat_map(|x| x)
356 /// Can be written as
360 pub FLAT_MAP_IDENTITY,
362 "call to `flat_map` where `flatten` is sufficient"
365 declare_clippy_lint! {
366 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
368 /// **Why is this bad?** Readability, this can be written more concisely as a
369 /// single method call.
371 /// **Known problems:** Often requires a condition + Option/Iterator creation
372 /// inside the closure.
376 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
378 /// Can be written as
380 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
384 "using a combination of `find` and `map` can usually be written as a single method call"
387 declare_clippy_lint! {
388 /// **What it does:** Checks for an iterator search (such as `find()`,
389 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
391 /// **Why is this bad?** Readability, this can be written more concisely as
394 /// **Known problems:** None.
398 /// # let vec = vec![1];
399 /// vec.iter().find(|x| **x == 0).is_some();
403 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
406 declare_clippy_lint! {
407 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
408 /// if it starts with a given char.
410 /// **Why is this bad?** Readability, this can be written more concisely as
411 /// `_.starts_with(_)`.
413 /// **Known problems:** None.
417 /// let name = "foo";
418 /// name.chars().next() == Some('_');
422 "using `.chars().next()` to check if a string starts with a char"
425 declare_clippy_lint! {
426 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
427 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
428 /// `unwrap_or_default` instead.
430 /// **Why is this bad?** The function will always be called and potentially
431 /// allocate an object acting as the default.
433 /// **Known problems:** If the function has side-effects, not calling it will
434 /// change the semantic of the program, but you shouldn't rely on that anyway.
438 /// # let foo = Some(String::new());
439 /// foo.unwrap_or(String::new());
441 /// this can instead be written:
443 /// # let foo = Some(String::new());
444 /// foo.unwrap_or_else(String::new);
448 /// # let foo = Some(String::new());
449 /// foo.unwrap_or_default();
453 "using any `*or` method with a function call, which suggests `*or_else`"
456 declare_clippy_lint! {
457 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
458 /// etc., and suggests to use `unwrap_or_else` instead
460 /// **Why is this bad?** The function will always be called.
462 /// **Known problems:** If the function has side-effects, not calling it will
463 /// change the semantics of the program, but you shouldn't rely on that anyway.
467 /// # let foo = Some(String::new());
468 /// # let err_code = "418";
469 /// # let err_msg = "I'm a teapot";
470 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
474 /// # let foo = Some(String::new());
475 /// # let err_code = "418";
476 /// # let err_msg = "I'm a teapot";
477 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
479 /// this can instead be written:
481 /// # let foo = Some(String::new());
482 /// # let err_code = "418";
483 /// # let err_msg = "I'm a teapot";
484 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
488 "using any `expect` method with a function call"
491 declare_clippy_lint! {
492 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
494 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
495 /// generics, not for using the `clone` method on a concrete type.
497 /// **Known problems:** None.
505 "using `clone` on a `Copy` type"
508 declare_clippy_lint! {
509 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
510 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
511 /// function syntax instead (e.g., `Rc::clone(foo)`).
513 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
514 /// can obscure the fact that only the pointer is being cloned, not the underlying
519 /// # use std::rc::Rc;
520 /// let x = Rc::new(1);
523 pub CLONE_ON_REF_PTR,
525 "using 'clone' on a ref-counted pointer"
528 declare_clippy_lint! {
529 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
531 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
532 /// cloning the underlying `T`.
534 /// **Known problems:** None.
541 /// let z = y.clone();
542 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
545 pub CLONE_DOUBLE_REF,
547 "using `clone` on `&&T`"
550 declare_clippy_lint! {
551 /// **What it does:** Checks for `new` not returning `Self`.
553 /// **Why is this bad?** As a convention, `new` methods are used to make a new
554 /// instance of a type.
556 /// **Known problems:** None.
561 /// fn new(..) -> NotAFoo {
567 "not returning `Self` in a `new` method"
570 declare_clippy_lint! {
571 /// **What it does:** Checks for string methods that receive a single-character
572 /// `str` as an argument, e.g., `_.split("x")`.
574 /// **Why is this bad?** Performing these methods using a `char` is faster than
577 /// **Known problems:** Does not catch multi-byte unicode characters.
580 /// `_.split("x")` could be `_.split('x')`
581 pub SINGLE_CHAR_PATTERN,
583 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
586 declare_clippy_lint! {
587 /// **What it does:** Checks for getting the inner pointer of a temporary
590 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
591 /// as the `CString` is alive.
593 /// **Known problems:** None.
597 /// let c_str = CString::new("foo").unwrap().as_ptr();
599 /// call_some_ffi_func(c_str);
602 /// Here `c_str` point to a freed address. The correct use would be:
604 /// let c_str = CString::new("foo").unwrap();
606 /// call_some_ffi_func(c_str.as_ptr());
609 pub TEMPORARY_CSTRING_AS_PTR,
611 "getting the inner pointer of a temporary `CString`"
614 declare_clippy_lint! {
615 /// **What it does:** Checks for use of `.iter().nth()` (and the related
616 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
618 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
621 /// **Known problems:** None.
625 /// let some_vec = vec![0, 1, 2, 3];
626 /// let bad_vec = some_vec.iter().nth(3);
627 /// let bad_slice = &some_vec[..].iter().nth(3);
629 /// The correct use would be:
631 /// let some_vec = vec![0, 1, 2, 3];
632 /// let bad_vec = some_vec.get(3);
633 /// let bad_slice = &some_vec[..].get(3);
637 "using `.iter().nth()` on a standard library type with O(1) element access"
640 declare_clippy_lint! {
641 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
643 /// **Why is this bad?** `.nth(x)` is cleaner
645 /// **Known problems:** None.
649 /// let some_vec = vec![0, 1, 2, 3];
650 /// let bad_vec = some_vec.iter().skip(3).next();
651 /// let bad_slice = &some_vec[..].iter().skip(3).next();
653 /// The correct use would be:
655 /// let some_vec = vec![0, 1, 2, 3];
656 /// let bad_vec = some_vec.iter().nth(3);
657 /// let bad_slice = &some_vec[..].iter().nth(3);
661 "using `.skip(x).next()` on an iterator"
664 declare_clippy_lint! {
665 /// **What it does:** Checks for use of `.get().unwrap()` (or
666 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
668 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
671 /// **Known problems:** Not a replacement for error handling: Using either
672 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
673 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
674 /// temporary placeholder for dealing with the `Option` type, then this does
675 /// not mitigate the need for error handling. If there is a chance that `.get()`
676 /// will be `None` in your program, then it is advisable that the `None` case
677 /// is handled in a future refactor instead of using `.unwrap()` or the Index
682 /// let mut some_vec = vec![0, 1, 2, 3];
683 /// let last = some_vec.get(3).unwrap();
684 /// *some_vec.get_mut(0).unwrap() = 1;
686 /// The correct use would be:
688 /// let mut some_vec = vec![0, 1, 2, 3];
689 /// let last = some_vec[3];
694 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
697 declare_clippy_lint! {
698 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
699 /// `&str` or `String`.
701 /// **Why is this bad?** `.push_str(s)` is clearer
703 /// **Known problems:** None.
708 /// let def = String::from("def");
709 /// let mut s = String::new();
710 /// s.extend(abc.chars());
711 /// s.extend(def.chars());
713 /// The correct use would be:
716 /// let def = String::from("def");
717 /// let mut s = String::new();
719 /// s.push_str(&def);
721 pub STRING_EXTEND_CHARS,
723 "using `x.extend(s.chars())` where s is a `&str` or `String`"
726 declare_clippy_lint! {
727 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
730 /// **Why is this bad?** `.to_vec()` is clearer
732 /// **Known problems:** None.
736 /// let s = [1, 2, 3, 4, 5];
737 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
739 /// The better use would be:
741 /// let s = [1, 2, 3, 4, 5];
742 /// let s2: Vec<isize> = s.to_vec();
744 pub ITER_CLONED_COLLECT,
746 "using `.cloned().collect()` on slice to create a `Vec`"
749 declare_clippy_lint! {
750 /// **What it does:** Checks for usage of `.chars().last()` or
751 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
753 /// **Why is this bad?** Readability, this can be written more concisely as
754 /// `_.ends_with(_)`.
756 /// **Known problems:** None.
760 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
764 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
767 declare_clippy_lint! {
768 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
769 /// types before and after the call are the same.
771 /// **Why is this bad?** The call is unnecessary.
773 /// **Known problems:** None.
777 /// # fn do_stuff(x: &[i32]) {}
778 /// let x: &[i32] = &[1, 2, 3, 4, 5];
779 /// do_stuff(x.as_ref());
781 /// The correct use would be:
783 /// # fn do_stuff(x: &[i32]) {}
784 /// let x: &[i32] = &[1, 2, 3, 4, 5];
789 "using `as_ref` where the types before and after the call are the same"
792 declare_clippy_lint! {
793 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
794 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
795 /// `sum` or `product`.
797 /// **Why is this bad?** Readability.
799 /// **Known problems:** False positive in pattern guards. Will be resolved once
800 /// non-lexical lifetimes are stable.
804 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
806 /// This could be written as:
808 /// let _ = (0..3).any(|x| x > 2);
810 pub UNNECESSARY_FOLD,
812 "using `fold` when a more succinct alternative exists"
815 declare_clippy_lint! {
816 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
817 /// More specifically it checks if the closure provided is only performing one of the
818 /// filter or map operations and suggests the appropriate option.
820 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
821 /// operation is being performed.
823 /// **Known problems:** None
827 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
829 /// As there is no transformation of the argument this could be written as:
831 /// let _ = (0..3).filter(|&x| x > 2);
835 /// let _ = (0..4).filter_map(i32::checked_abs);
837 /// As there is no conditional check on the argument this could be written as:
839 /// let _ = (0..4).map(i32::checked_abs);
841 pub UNNECESSARY_FILTER_MAP,
843 "using `filter_map` when a more succinct alternative exists"
846 declare_clippy_lint! {
847 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
850 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
851 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
852 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
853 /// like calling `iter` would. Furthermore, when the standard library actually
854 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
855 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
856 /// and the code will be broken.
858 /// **Known problems:** None
863 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
865 pub INTO_ITER_ON_ARRAY,
867 "using `.into_iter()` on an array"
870 declare_clippy_lint! {
871 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
874 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
875 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
876 /// `iter_mut` directly.
878 /// **Known problems:** None
883 /// let _ = (&vec![3, 4, 5]).into_iter();
885 pub INTO_ITER_ON_REF,
887 "using `.into_iter()` on a reference"
890 declare_lint_pass!(Methods => [
893 SHOULD_IMPLEMENT_TRAIT,
894 WRONG_SELF_CONVENTION,
895 WRONG_PUB_SELF_CONVENTION,
897 OPTION_MAP_UNWRAP_OR,
898 OPTION_MAP_UNWRAP_OR_ELSE,
899 RESULT_MAP_UNWRAP_OR_ELSE,
911 TEMPORARY_CSTRING_AS_PTR,
925 UNNECESSARY_FILTER_MAP,
930 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
931 #[allow(clippy::cognitive_complexity)]
932 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
933 if in_macro(expr.span) {
937 let (method_names, arg_lists) = method_calls(expr, 2);
938 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
939 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
941 match method_names.as_slice() {
942 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
943 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
944 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
945 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
946 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
947 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
948 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
949 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
950 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
951 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
952 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
953 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
954 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
955 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
956 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0]),
957 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
958 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
959 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
960 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
961 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
962 ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
963 lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
965 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
966 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
967 ["next", "skip"] => lint_iter_skip_next(cx, expr),
968 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
969 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
970 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
971 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
972 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
977 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
978 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
979 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
981 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
982 if args.len() == 1 && method_call.ident.name == sym!(clone) {
983 lint_clone_on_copy(cx, expr, &args[0], self_ty);
984 lint_clone_on_ref_ptr(cx, expr, &args[0]);
988 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
989 for &(method, pos) in &PATTERN_METHODS {
990 if method_call.ident.name.as_str() == method && args.len() > pos {
991 lint_single_char_pattern(cx, expr, &args[pos]);
995 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
996 lint_into_iter(cx, expr, self_ty, *method_span);
1001 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1002 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1004 let mut info = BinaryExprInfo {
1008 eq: op.node == hir::BinOpKind::Eq,
1010 lint_binary_expr_with_method_call(cx, &mut info);
1016 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
1017 if in_external_macro(cx.sess(), implitem.span) {
1020 let name = implitem.ident.name.as_str();
1021 let parent = cx.tcx.hir().get_parent_item(implitem.hir_id);
1022 let item = cx.tcx.hir().expect_item(parent);
1023 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1024 let ty = cx.tcx.type_of(def_id);
1026 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
1027 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
1028 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1029 if let hir::ItemKind::Impl(_, _, _, _, None, ref self_ty, _) = item.node;
1031 if cx.access_levels.is_exported(implitem.hir_id) {
1032 // check missing trait implementations
1033 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
1034 if name == method_name &&
1035 sig.decl.inputs.len() == n_args &&
1036 out_type.matches(cx, &sig.decl.output) &&
1037 self_kind.matches(cx, first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
1038 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
1039 "defining a method called `{}` on this type; consider implementing \
1040 the `{}` trait or choosing a less ambiguous name", name, trait_name));
1045 // check conventions w.r.t. conversion method names and predicates
1046 let is_copy = is_copy(cx, ty);
1047 for &(ref conv, self_kinds) in &CONVENTIONS {
1048 if conv.check(&name) {
1051 .any(|k| k.matches(cx, first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics)) {
1052 let lint = if item.vis.node.is_pub() {
1053 WRONG_PUB_SELF_CONVENTION
1055 WRONG_SELF_CONVENTION
1060 &format!("methods called `{}` usually take {}; consider choosing a less \
1064 .map(|k| k.description())
1065 .collect::<Vec<_>>()
1069 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1077 if let hir::ImplItemKind::Method(_, _) = implitem.node {
1078 let ret_ty = return_ty(cx, implitem.hir_id);
1080 // walk the return type and check for Self (this does not check associated types)
1081 for inner_type in ret_ty.walk() {
1082 if same_tys(cx, ty, inner_type) {
1087 // if return type is impl trait, check the associated types
1088 if let ty::Opaque(def_id, _) = ret_ty.sty {
1089 // one of the associated types must be Self
1090 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1092 (Predicate::Projection(poly_projection_predicate), _) => {
1093 let binder = poly_projection_predicate.ty();
1094 let associated_type = binder.skip_binder();
1095 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
1097 // if the associated type is self, early return and do not trigger lint
1098 if associated_type_is_self_type {
1107 if name == "new" && !same_tys(cx, ret_ty, ty) {
1112 "methods called `new` usually return `Self`",
1119 /// Checks for the `OR_FUN_CALL` lint.
1120 #[allow(clippy::too_many_lines)]
1121 fn lint_or_fun_call<'a, 'tcx>(
1122 cx: &LateContext<'a, 'tcx>,
1126 args: &'tcx [hir::Expr],
1128 // Searches an expression for method calls or function calls that aren't ctors
1129 struct FunCallFinder<'a, 'tcx> {
1130 cx: &'a LateContext<'a, 'tcx>,
1134 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1135 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1136 let call_found = match &expr.node {
1137 // ignore enum and struct constructors
1138 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1139 hir::ExprKind::MethodCall(..) => true,
1144 // don't lint for constant values
1145 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1146 let promotable = self
1149 .rvalue_promotable_map(owner_def)
1150 .contains(&expr.hir_id.local_id);
1157 intravisit::walk_expr(self, expr);
1161 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1162 intravisit::NestedVisitorMap::None
1166 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1167 fn check_unwrap_or_default(
1168 cx: &LateContext<'_, '_>,
1171 self_expr: &hir::Expr,
1180 if name == "unwrap_or" {
1181 if let hir::ExprKind::Path(ref qpath) = fun.node {
1182 let path = &*last_path_segment(qpath).ident.as_str();
1184 if ["default", "new"].contains(&path) {
1185 let arg_ty = cx.tables.expr_ty(arg);
1186 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1192 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1193 let mut applicability = Applicability::MachineApplicable;
1198 &format!("use of `{}` followed by a call to `{}`", name, path),
1201 "{}.unwrap_or_default()",
1202 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1215 /// Checks for `*or(foo())`.
1216 #[allow(clippy::too_many_arguments)]
1217 fn check_general_case<'a, 'tcx>(
1218 cx: &LateContext<'a, 'tcx>,
1222 self_expr: &hir::Expr,
1223 arg: &'tcx hir::Expr,
1227 // (path, fn_has_argument, methods, suffix)
1228 let know_types: &[(&[_], _, &[_], _)] = &[
1229 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1230 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1231 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1232 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1235 // early check if the name is one we care about
1236 if know_types.iter().all(|k| !k.2.contains(&name)) {
1240 let mut finder = FunCallFinder { cx: &cx, found: false };
1241 finder.visit_expr(&arg);
1246 let self_ty = cx.tables.expr_ty(self_expr);
1248 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1249 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1251 (fn_has_arguments, poss, suffix)
1256 if !poss.contains(&name) {
1260 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1261 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1262 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1263 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1265 let span_replace_word = method_span.with_hi(span.hi());
1270 &format!("use of `{}` followed by a function call", name),
1272 format!("{}_{}({})", name, suffix, sugg),
1273 Applicability::HasPlaceholders,
1277 if args.len() == 2 {
1278 match args[1].node {
1279 hir::ExprKind::Call(ref fun, ref or_args) => {
1280 let or_has_args = !or_args.is_empty();
1281 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1294 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1301 !or_args.is_empty(),
1309 /// Checks for the `EXPECT_FUN_CALL` lint.
1310 #[allow(clippy::too_many_lines)]
1311 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1312 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1314 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1315 let mut arg_root = arg;
1317 arg_root = match &arg_root.node {
1318 hir::ExprKind::AddrOf(_, expr) => expr,
1319 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1320 if call_args.len() == 1
1321 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1323 let arg_type = cx.tables.expr_ty(&call_args[0]);
1324 let base_type = walk_ptrs_ty(arg_type);
1325 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1339 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1340 // converted to string.
1341 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1342 let arg_ty = cx.tables.expr_ty(arg);
1343 if match_type(cx, arg_ty, &paths::STRING) {
1346 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1347 if ty.sty == ty::Str {
1354 fn generate_format_arg_snippet(
1355 cx: &LateContext<'_, '_>,
1357 applicability: &mut Applicability,
1359 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1360 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1361 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1362 return format_arg_expr_tup
1364 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1373 fn is_call(node: &hir::ExprKind) -> bool {
1375 hir::ExprKind::AddrOf(_, expr) => {
1378 hir::ExprKind::Call(..)
1379 | hir::ExprKind::MethodCall(..)
1380 // These variants are debatable or require further examination
1381 | hir::ExprKind::Match(..)
1382 | hir::ExprKind::Block{ .. } => true,
1387 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1391 let receiver_type = cx.tables.expr_ty(&args[0]);
1392 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1394 } else if match_type(cx, receiver_type, &paths::RESULT) {
1400 let arg_root = get_arg_root(cx, &args[1]);
1402 let span_replace_word = method_span.with_hi(expr.span.hi());
1404 let mut applicability = Applicability::MachineApplicable;
1406 //Special handling for `format!` as arg_root
1407 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1408 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1409 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1410 let fmt_spec = &format_args[0];
1411 let fmt_args = &format_args[1];
1413 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1415 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1417 let sugg = args.join(", ");
1423 &format!("use of `{}` followed by a function call", name),
1425 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1434 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1435 if requires_to_string(cx, arg_root) {
1436 arg_root_snippet.to_mut().push_str(".to_string()");
1443 &format!("use of `{}` followed by a function call", name),
1445 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1450 /// Checks for the `CLONE_ON_COPY` lint.
1451 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1452 let ty = cx.tables.expr_ty(expr);
1453 if let ty::Ref(_, inner, _) = arg_ty.sty {
1454 if let ty::Ref(_, innermost, _) = inner.sty {
1459 "using `clone` on a double-reference; \
1460 this will copy the reference instead of cloning the inner type",
1462 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1463 let mut ty = innermost;
1465 while let ty::Ref(_, inner, _) = ty.sty {
1469 let refs: String = iter::repeat('&').take(n + 1).collect();
1470 let derefs: String = iter::repeat('*').take(n).collect();
1471 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1474 "try dereferencing it",
1475 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1476 Applicability::MaybeIncorrect,
1480 "or try being explicit about what type to clone",
1482 Applicability::MaybeIncorrect,
1487 return; // don't report clone_on_copy
1491 if is_copy(cx, ty) {
1493 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1494 // x.clone() might have dereferenced x, possibly through Deref impls
1495 if cx.tables.expr_ty(arg) == ty {
1496 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1498 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1499 match cx.tcx.hir().get(parent) {
1500 hir::Node::Expr(parent) => match parent.node {
1501 // &*x is a nop, &x.clone() is not
1502 hir::ExprKind::AddrOf(..) |
1503 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1504 hir::ExprKind::MethodCall(..) => return,
1507 hir::Node::Stmt(stmt) => {
1508 if let hir::StmtKind::Local(ref loc) = stmt.node {
1509 if let hir::PatKind::Ref(..) = loc.pat.node {
1510 // let ref y = *x borrows x, let ref y = x.clone() does not
1518 let deref_count = cx
1520 .expr_adjustments(arg)
1523 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1530 let derefs: String = iter::repeat('*').take(deref_count).collect();
1531 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1536 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1537 if let Some((text, snip)) = snip {
1538 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1544 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1545 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1547 if let ty::Adt(_, subst) = obj_ty.sty {
1548 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1550 } else if match_type(cx, obj_ty, &paths::ARC) {
1552 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1562 "using '.clone()' on a ref-counted pointer",
1565 "{}::<{}>::clone(&{})",
1568 snippet(cx, arg.span, "_")
1570 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1575 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1577 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1578 let target = &arglists[0][0];
1579 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1580 let ref_str = if self_ty.sty == ty::Str {
1582 } else if match_type(cx, self_ty, &paths::STRING) {
1588 let mut applicability = Applicability::MachineApplicable;
1591 STRING_EXTEND_CHARS,
1593 "calling `.extend(_.chars())`",
1596 "{}.push_str({}{})",
1597 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1599 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1606 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1607 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1608 if match_type(cx, obj_ty, &paths::STRING) {
1609 lint_string_extend(cx, expr, args);
1613 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1615 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1617 if let hir::ExprKind::Path(ref path) = fun.node;
1618 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1619 if match_def_path(cx, did, &paths::CSTRING_NEW);
1623 TEMPORARY_CSTRING_AS_PTR,
1625 "you are getting the inner pointer of a temporary `CString`",
1627 db.note("that pointer will be invalid outside this expression");
1628 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1634 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1635 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1636 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1637 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1640 ITER_CLONED_COLLECT,
1642 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1645 ".to_vec()".to_string(),
1646 Applicability::MachineApplicable,
1653 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1654 fn check_fold_with_op(
1655 cx: &LateContext<'_, '_>,
1656 fold_args: &[hir::Expr],
1658 replacement_method_name: &str,
1659 replacement_has_args: bool,
1662 // Extract the body of the closure passed to fold
1663 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1664 let closure_body = cx.tcx.hir().body(body_id);
1665 let closure_expr = remove_blocks(&closure_body.value);
1667 // Check if the closure body is of the form `acc <op> some_expr(x)`
1668 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1669 if bin_op.node == op;
1671 // Extract the names of the two arguments to the closure
1672 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1673 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1675 if match_var(&*left_expr, first_arg_ident);
1676 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1679 // Span containing `.fold(...)`
1680 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1681 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1683 let mut applicability = Applicability::MachineApplicable;
1684 let sugg = if replacement_has_args {
1686 ".{replacement}(|{s}| {r})",
1687 replacement = replacement_method_name,
1688 s = second_arg_ident,
1689 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1694 replacement = replacement_method_name,
1702 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1703 "this `.fold` can be written more succinctly using another method",
1712 // Check that this is a call to Iterator::fold rather than just some function called fold
1713 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1718 fold_args.len() == 3,
1719 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1722 // Check if the first argument to .fold is a suitable literal
1723 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1725 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1726 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1727 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1728 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1734 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1735 let mut_str = if is_mut { "_mut" } else { "" };
1736 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1738 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1740 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1743 return; // caller is not a type that we want to lint
1751 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1752 mut_str, caller_type
1757 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1758 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1759 // because they do not implement `IndexMut`
1760 let mut applicability = Applicability::MachineApplicable;
1761 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1762 let get_args_str = if get_args.len() > 1 {
1763 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1765 return; // not linting on a .get().unwrap() chain or variant
1768 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1769 needs_ref = get_args_str.parse::<usize>().is_ok();
1771 } else if match_type(cx, expr_ty, &paths::VEC) {
1772 needs_ref = get_args_str.parse::<usize>().is_ok();
1774 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1775 needs_ref = get_args_str.parse::<usize>().is_ok();
1777 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1780 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1784 return; // caller is not a type that we want to lint
1787 let mut span = expr.span;
1789 // Handle the case where the result is immediately dereferenced
1790 // by not requiring ref and pulling the dereference into the
1794 if let Some(parent) = get_parent_expr(cx, expr);
1795 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1802 let mut_str = if is_mut { "_mut" } else { "" };
1803 let borrow_str = if !needs_ref {
1816 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1817 mut_str, caller_type
1823 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1830 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1831 // lint if caller of skip is an Iterator
1832 if match_trait_method(cx, expr, &paths::ITERATOR) {
1837 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1842 fn derefs_to_slice<'a, 'tcx>(
1843 cx: &LateContext<'a, 'tcx>,
1844 expr: &'tcx hir::Expr,
1846 ) -> Option<&'tcx hir::Expr> {
1847 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1849 ty::Slice(_) => true,
1850 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1851 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1852 ty::Array(_, size) => size.eval_usize(cx.tcx, cx.param_env) < 32,
1853 ty::Ref(_, inner, _) => may_slice(cx, inner),
1858 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1859 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1866 ty::Slice(_) => Some(expr),
1867 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1868 ty::Ref(_, inner, _) => {
1869 if may_slice(cx, inner) {
1880 /// lint use of `unwrap()` for `Option`s and `Result`s
1881 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1882 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1884 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1885 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1886 } else if match_type(cx, obj_ty, &paths::RESULT) {
1887 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1892 if let Some((lint, kind, none_value)) = mess {
1898 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1899 using expect() to provide a better panic \
1907 /// lint use of `ok().expect()` for `Result`s
1908 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1909 // lint if the caller of `ok()` is a `Result`
1910 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1911 let result_type = cx.tables.expr_ty(&ok_args[0]);
1912 if let Some(error_type) = get_error_type(cx, result_type) {
1913 if has_debug_impl(error_type, cx) {
1918 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1925 /// lint use of `map().flatten()` for `Iterators`
1926 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1927 // lint if caller of `.map().flatten()` is an Iterator
1928 if match_trait_method(cx, expr, &paths::ITERATOR) {
1929 let msg = "called `map(..).flatten()` on an `Iterator`. \
1930 This is more succinctly expressed by calling `.flat_map(..)`";
1931 let self_snippet = snippet(cx, map_args[0].span, "..");
1932 let func_snippet = snippet(cx, map_args[1].span, "..");
1933 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1934 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1937 "try using flat_map instead",
1939 Applicability::MachineApplicable,
1945 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1946 fn lint_map_unwrap_or_else<'a, 'tcx>(
1947 cx: &LateContext<'a, 'tcx>,
1948 expr: &'tcx hir::Expr,
1949 map_args: &'tcx [hir::Expr],
1950 unwrap_args: &'tcx [hir::Expr],
1952 // lint if the caller of `map()` is an `Option`
1953 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1954 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1956 if is_option || is_result {
1957 // Don't make a suggestion that may fail to compile due to mutably borrowing
1958 // the same variable twice.
1959 let map_mutated_vars = mutated_variables(&map_args[0], cx);
1960 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
1961 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
1962 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
1970 let msg = if is_option {
1971 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1972 `map_or_else(g, f)` instead"
1974 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1975 `ok().map_or_else(g, f)` instead"
1977 // get snippets for args to map() and unwrap_or_else()
1978 let map_snippet = snippet(cx, map_args[1].span, "..");
1979 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1980 // lint, with note if neither arg is > 1 line and both map() and
1981 // unwrap_or_else() have the same span
1982 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1983 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1984 if same_span && !multiline {
1988 OPTION_MAP_UNWRAP_OR_ELSE
1990 RESULT_MAP_UNWRAP_OR_ELSE
1996 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1999 if is_result { "ok()." } else { "" }
2002 } else if same_span && multiline {
2006 OPTION_MAP_UNWRAP_OR_ELSE
2008 RESULT_MAP_UNWRAP_OR_ELSE
2017 /// lint use of `_.map_or(None, _)` for `Option`s
2018 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
2019 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
2020 // check if the first non-self argument to map_or() is None
2021 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
2022 match_qpath(qpath, &paths::OPTION_NONE)
2027 if map_or_arg_is_none {
2029 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
2030 `and_then(f)` instead";
2031 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
2032 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
2033 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
2034 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
2037 "try using and_then instead",
2039 Applicability::MachineApplicable, // snippet
2046 /// lint use of `filter().next()` for `Iterators`
2047 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2048 // lint if caller of `.filter().next()` is an Iterator
2049 if match_trait_method(cx, expr, &paths::ITERATOR) {
2050 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2051 `.find(p)` instead.";
2052 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2053 if filter_snippet.lines().count() <= 1 {
2054 // add note if not multi-line
2061 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2064 span_lint(cx, FILTER_NEXT, expr.span, msg);
2069 /// lint use of `filter().map()` for `Iterators`
2070 fn lint_filter_map<'a, 'tcx>(
2071 cx: &LateContext<'a, 'tcx>,
2072 expr: &'tcx hir::Expr,
2073 _filter_args: &'tcx [hir::Expr],
2074 _map_args: &'tcx [hir::Expr],
2076 // lint if caller of `.filter().map()` is an Iterator
2077 if match_trait_method(cx, expr, &paths::ITERATOR) {
2078 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2079 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2080 span_lint(cx, FILTER_MAP, expr.span, msg);
2084 /// lint use of `filter_map().next()` for `Iterators`
2085 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2086 if match_trait_method(cx, expr, &paths::ITERATOR) {
2087 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2088 `.find_map(p)` instead.";
2089 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2090 if filter_snippet.lines().count() <= 1 {
2097 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2100 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2105 /// lint use of `find().map()` for `Iterators`
2106 fn lint_find_map<'a, 'tcx>(
2107 cx: &LateContext<'a, 'tcx>,
2108 expr: &'tcx hir::Expr,
2109 _find_args: &'tcx [hir::Expr],
2110 map_args: &'tcx [hir::Expr],
2112 // lint if caller of `.filter().map()` is an Iterator
2113 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2114 let msg = "called `find(p).map(q)` on an `Iterator`. \
2115 This is more succinctly expressed by calling `.find_map(..)` instead.";
2116 span_lint(cx, FIND_MAP, expr.span, msg);
2120 /// lint use of `filter().map()` for `Iterators`
2121 fn lint_filter_map_map<'a, 'tcx>(
2122 cx: &LateContext<'a, 'tcx>,
2123 expr: &'tcx hir::Expr,
2124 _filter_args: &'tcx [hir::Expr],
2125 _map_args: &'tcx [hir::Expr],
2127 // lint if caller of `.filter().map()` is an Iterator
2128 if match_trait_method(cx, expr, &paths::ITERATOR) {
2129 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2130 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2131 span_lint(cx, FILTER_MAP, expr.span, msg);
2135 /// lint use of `filter().flat_map()` for `Iterators`
2136 fn lint_filter_flat_map<'a, 'tcx>(
2137 cx: &LateContext<'a, 'tcx>,
2138 expr: &'tcx hir::Expr,
2139 _filter_args: &'tcx [hir::Expr],
2140 _map_args: &'tcx [hir::Expr],
2142 // lint if caller of `.filter().flat_map()` is an Iterator
2143 if match_trait_method(cx, expr, &paths::ITERATOR) {
2144 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2145 This is more succinctly expressed by calling `.flat_map(..)` \
2146 and filtering by returning an empty Iterator.";
2147 span_lint(cx, FILTER_MAP, expr.span, msg);
2151 /// lint use of `filter_map().flat_map()` for `Iterators`
2152 fn lint_filter_map_flat_map<'a, 'tcx>(
2153 cx: &LateContext<'a, 'tcx>,
2154 expr: &'tcx hir::Expr,
2155 _filter_args: &'tcx [hir::Expr],
2156 _map_args: &'tcx [hir::Expr],
2158 // lint if caller of `.filter_map().flat_map()` is an Iterator
2159 if match_trait_method(cx, expr, &paths::ITERATOR) {
2160 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2161 This is more succinctly expressed by calling `.flat_map(..)` \
2162 and filtering by returning an empty Iterator.";
2163 span_lint(cx, FILTER_MAP, expr.span, msg);
2167 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
2168 fn lint_flat_map_identity<'a, 'tcx>(
2169 cx: &LateContext<'a, 'tcx>,
2170 expr: &'tcx hir::Expr,
2171 flat_map_args: &'tcx [hir::Expr],
2174 if match_trait_method(cx, expr, &paths::ITERATOR);
2176 if flat_map_args.len() == 2;
2177 if let hir::ExprKind::Closure(_, _, body_id, _, _) = flat_map_args[1].node;
2178 let body = cx.tcx.hir().body(body_id);
2180 if body.arguments.len() == 1;
2181 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.arguments[0].pat.node;
2182 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.node;
2184 if path.segments.len() == 1;
2185 if path.segments[0].ident.as_str() == binding_ident.as_str();
2188 let msg = "called `flat_map(|x| x)` on an `Iterator`. \
2189 This can be simplified by calling `flatten().`";
2190 span_lint(cx, FLAT_MAP_IDENTITY, expr.span, msg);
2195 if match_trait_method(cx, expr, &paths::ITERATOR);
2197 if flat_map_args.len() == 2;
2199 let expr = &flat_map_args[1];
2201 if let hir::ExprKind::Path(ref qpath) = expr.node;
2203 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
2206 let msg = "called `flat_map(std::convert::identity)` on an `Iterator`. \
2207 This can be simplified by calling `flatten().`";
2208 span_lint(cx, FLAT_MAP_IDENTITY, expr.span, msg);
2213 /// lint searching an Iterator followed by `is_some()`
2214 fn lint_search_is_some<'a, 'tcx>(
2215 cx: &LateContext<'a, 'tcx>,
2216 expr: &'tcx hir::Expr,
2217 search_method: &str,
2218 search_args: &'tcx [hir::Expr],
2219 is_some_args: &'tcx [hir::Expr],
2221 // lint if caller of search is an Iterator
2222 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2224 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2225 expressed by calling `any()`.",
2228 let search_snippet = snippet(cx, search_args[1].span, "..");
2229 if search_snippet.lines().count() <= 1 {
2230 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2231 let any_search_snippet = if_chain! {
2232 if search_method == "find";
2233 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2234 let closure_body = cx.tcx.hir().body(body_id);
2235 if let Some(closure_arg) = closure_body.arguments.get(0);
2236 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2238 Some(search_snippet.replacen('&', "", 1))
2243 // add note if not multi-line
2251 "replace `{0}({1}).is_some()` with `any({2})`",
2254 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2258 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2263 /// Used for `lint_binary_expr_with_method_call`.
2264 #[derive(Copy, Clone)]
2265 struct BinaryExprInfo<'a> {
2266 expr: &'a hir::Expr,
2267 chain: &'a hir::Expr,
2268 other: &'a hir::Expr,
2272 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2273 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2274 macro_rules! lint_with_both_lhs_and_rhs {
2275 ($func:ident, $cx:expr, $info:ident) => {
2276 if !$func($cx, $info) {
2277 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2278 if $func($cx, $info) {
2285 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2286 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2287 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2288 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2291 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2293 cx: &LateContext<'_, '_>,
2294 info: &BinaryExprInfo<'_>,
2295 chain_methods: &[&str],
2296 lint: &'static Lint,
2300 if let Some(args) = method_chain_args(info.chain, chain_methods);
2301 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2302 if arg_char.len() == 1;
2303 if let hir::ExprKind::Path(ref qpath) = fun.node;
2304 if let Some(segment) = single_segment_path(qpath);
2305 if segment.ident.name == sym!(Some);
2307 let mut applicability = Applicability::MachineApplicable;
2308 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2310 if self_ty.sty != ty::Str {
2318 &format!("you should use the `{}` method", suggest),
2320 format!("{}{}.{}({})",
2321 if info.eq { "" } else { "!" },
2322 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2324 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2335 /// Checks for the `CHARS_NEXT_CMP` lint.
2336 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2337 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2340 /// Checks for the `CHARS_LAST_CMP` lint.
2341 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2342 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2345 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2349 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2350 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2351 cx: &LateContext<'a, 'tcx>,
2352 info: &BinaryExprInfo<'_>,
2353 chain_methods: &[&str],
2354 lint: &'static Lint,
2358 if let Some(args) = method_chain_args(info.chain, chain_methods);
2359 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2360 if let ast::LitKind::Char(c) = lit.node;
2362 let mut applicability = Applicability::MachineApplicable;
2367 &format!("you should use the `{}` method", suggest),
2369 format!("{}{}.{}('{}')",
2370 if info.eq { "" } else { "!" },
2371 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2384 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2385 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2386 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2389 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2390 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2391 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2394 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2398 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2399 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2401 if let hir::ExprKind::Lit(lit) = &arg.node;
2402 if let ast::LitKind::Str(r, style) = lit.node;
2403 if r.as_str().len() == 1;
2405 let mut applicability = Applicability::MachineApplicable;
2406 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2407 let ch = if let ast::StrStyle::Raw(nhash) = style {
2408 let nhash = nhash as usize;
2409 // for raw string: r##"a"##
2410 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
2412 // for regular string: "a"
2413 &snip[1..(snip.len() - 1)]
2415 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
2418 SINGLE_CHAR_PATTERN,
2420 "single-character string constant used as pattern",
2421 "try using a char instead",
2429 /// Checks for the `USELESS_ASREF` lint.
2430 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2431 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2432 // check if the call is to the actual `AsRef` or `AsMut` trait
2433 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2434 // check if the type after `as_ref` or `as_mut` is the same as before
2435 let recvr = &as_ref_args[0];
2436 let rcv_ty = cx.tables.expr_ty(recvr);
2437 let res_ty = cx.tables.expr_ty(expr);
2438 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2439 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2440 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2441 // allow the `as_ref` or `as_mut` if it is followed by another method call
2443 if let Some(parent) = get_parent_expr(cx, expr);
2444 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2445 if span != &expr.span;
2451 let mut applicability = Applicability::MachineApplicable;
2456 &format!("this call to `{}` does nothing", call_name),
2458 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2465 fn ty_has_iter_method(
2466 cx: &LateContext<'_, '_>,
2467 self_ref_ty: Ty<'_>,
2468 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2469 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2470 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2475 let mutbl = match self_ref_ty.sty {
2476 ty::Ref(_, _, mutbl) => mutbl,
2477 _ => unreachable!(),
2479 let method_name = match mutbl {
2480 hir::MutImmutable => "iter",
2481 hir::MutMutable => "iter_mut",
2483 Some((lint, ty_name, method_name))
2489 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2490 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2493 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2499 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2503 method_name.to_string(),
2504 Applicability::MachineApplicable,
2509 /// Given a `Result<T, E>` type, return its error type (`E`).
2510 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2511 if let ty::Adt(_, substs) = ty.sty {
2512 if match_type(cx, ty, &paths::RESULT) {
2513 substs.types().nth(1)
2522 /// This checks whether a given type is known to implement Debug.
2523 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2524 match cx.tcx.lang_items().debug_trait() {
2525 Some(debug) => implements_trait(cx, ty, debug, &[]),
2532 StartsWith(&'static str),
2536 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2537 (Convention::Eq("new"), &[SelfKind::No]),
2538 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2539 (Convention::StartsWith("from_"), &[SelfKind::No]),
2540 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2541 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2542 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2543 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2547 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2548 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2549 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2550 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2551 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2552 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2553 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2554 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2555 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2556 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2557 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2558 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2559 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2560 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2561 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2562 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2563 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2564 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2565 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2566 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2567 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2568 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2569 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2570 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2571 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2572 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2573 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2574 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2575 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2576 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2577 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2581 const PATTERN_METHODS: [(&str, usize); 17] = [
2589 ("split_terminator", 1),
2590 ("rsplit_terminator", 1),
2595 ("match_indices", 1),
2596 ("rmatch_indices", 1),
2597 ("trim_start_matches", 1),
2598 ("trim_end_matches", 1),
2601 #[derive(Clone, Copy, PartialEq, Debug)]
2612 cx: &LateContext<'_, '_>,
2616 allow_value_for_ref: bool,
2617 generics: &hir::Generics,
2619 // Self types in the HIR are desugared to explicit self types. So it will
2622 // where SomeType can be `Self` or an explicit impl self type (e.g., `Foo` if
2623 // the impl is on `Foo`)
2624 // Thus, we only need to test equality against the impl self type or if it is
2626 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
2627 // `Self`, `&mut Self`,
2628 // and `Box<Self>`, including the equivalent types with `Foo`.
2630 let is_actually_self = |ty| is_self_ty(ty) || SpanlessEq::new(cx).eq_ty(ty, self_ty);
2633 Self::Value => is_actually_self(ty),
2634 Self::Ref | Self::RefMut => {
2635 if allow_value_for_ref && is_actually_self(ty) {
2639 hir::TyKind::Rptr(_, ref mt_ty) => {
2640 let mutability_match = if self == Self::Ref {
2641 mt_ty.mutbl == hir::MutImmutable
2643 mt_ty.mutbl == hir::MutMutable
2645 is_actually_self(&mt_ty.ty) && mutability_match
2654 Self::Value => false,
2655 Self::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
2656 Self::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
2662 fn description(self) -> &'static str {
2664 Self::Value => "self by value",
2665 Self::Ref => "self by reference",
2666 Self::RefMut => "self by mutable reference",
2667 Self::No => "no self",
2672 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
2673 single_segment_ty(ty).map_or(false, |seg| {
2674 generics.params.iter().any(|param| match param.kind {
2675 hir::GenericParamKind::Type { .. } => {
2676 param.name.ident().name == seg.ident.name
2677 && param.bounds.iter().any(|bound| {
2678 if let hir::GenericBound::Trait(ref ptr, ..) = *bound {
2679 let path = &ptr.trait_ref.path;
2680 match_path(path, name)
2681 && path.segments.last().map_or(false, |s| {
2682 if let Some(ref params) = s.args {
2683 if params.parenthesized {
2686 // FIXME(flip1995): messy, improve if there is a better option
2688 let types: Vec<_> = params
2691 .filter_map(|arg| match arg {
2692 hir::GenericArg::Type(ty) => Some(ty),
2696 types.len() == 1 && (is_self_ty(&types[0]) || is_ty(&*types[0], self_ty))
2712 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
2713 match (&ty.node, &self_ty.node) {
2715 &hir::TyKind::Path(hir::QPath::Resolved(_, ref ty_path)),
2716 &hir::TyKind::Path(hir::QPath::Resolved(_, ref self_ty_path)),
2720 .map(|seg| seg.ident.name)
2721 .eq(self_ty_path.segments.iter().map(|seg| seg.ident.name)),
2726 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2727 if let hir::TyKind::Path(ref path) = ty.node {
2728 single_segment_path(path)
2735 fn check(&self, other: &str) -> bool {
2737 Self::Eq(this) => this == other,
2738 Self::StartsWith(this) => other.starts_with(this) && this != other,
2743 impl fmt::Display for Convention {
2744 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2746 Self::Eq(this) => this.fmt(f),
2747 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2752 #[derive(Clone, Copy)]
2761 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2762 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2764 (Self::Unit, &hir::DefaultReturn(_)) => true,
2765 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2766 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2767 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2768 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2774 fn is_bool(ty: &hir::Ty) -> bool {
2775 if let hir::TyKind::Path(ref p) = ty.node {
2776 match_qpath(p, &["bool"])