1 mod option_map_unwrap_or;
2 mod unnecessary_filter_map;
8 use if_chain::if_chain;
11 use rustc::hir::def::{DefKind, Res};
12 use rustc::hir::intravisit::{self, Visitor};
13 use rustc::lint::{in_external_macro, LateContext, LateLintPass, Lint, LintArray, LintContext, LintPass};
14 use rustc::ty::{self, Predicate, Ty};
15 use rustc::{declare_lint_pass, declare_tool_lint};
16 use rustc_errors::Applicability;
18 use syntax::source_map::{BytePos, Span};
19 use syntax::symbol::LocalInternedString;
21 use crate::utils::paths;
22 use crate::utils::sugg;
23 use crate::utils::usage::mutated_variables;
25 get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy,
26 is_ctor_function, is_expn_of, iter_input_pats, last_path_segment, match_def_path, match_qpath, match_trait_method,
27 match_type, match_var, method_calls, method_chain_args, remove_blocks, return_ty, same_tys, single_segment_path,
28 snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_sugg,
29 span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
32 declare_clippy_lint! {
33 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
35 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
36 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
37 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
38 /// `Allow` by default.
40 /// **Known problems:** None.
44 /// Using unwrap on an `Option`:
47 /// let opt = Some(1);
54 /// let opt = Some(1);
55 /// opt.expect("more helpful message");
57 pub OPTION_UNWRAP_USED,
59 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
62 declare_clippy_lint! {
63 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
65 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
66 /// values. Normally, you want to implement more sophisticated error handling,
67 /// and propagate errors upwards with `try!`.
69 /// Even if you want to panic on errors, not all `Error`s implement good
70 /// messages on display. Therefore, it may be beneficial to look at the places
71 /// where they may get displayed. Activate this lint to do just that.
73 /// **Known problems:** None.
76 /// Using unwrap on an `Option`:
79 /// let res: Result<usize, ()> = Ok(1);
86 /// let res: Result<usize, ()> = Ok(1);
87 /// res.expect("more helpful message");
89 pub RESULT_UNWRAP_USED,
91 "using `Result.unwrap()`, which might be better handled"
94 declare_clippy_lint! {
95 /// **What it does:** Checks for methods that should live in a trait
96 /// implementation of a `std` trait (see [llogiq's blog
97 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
98 /// information) instead of an inherent implementation.
100 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
101 /// the code, often with very little cost. Also people seeing a `mul(...)`
103 /// may expect `*` to work equally, so you should have good reason to disappoint
106 /// **Known problems:** None.
112 /// fn add(&self, other: &X) -> X {
117 pub SHOULD_IMPLEMENT_TRAIT,
119 "defining a method that should be implementing a std trait"
122 declare_clippy_lint! {
123 /// **What it does:** Checks for methods with certain name prefixes and which
124 /// doesn't match how self is taken. The actual rules are:
126 /// |Prefix |`self` taken |
127 /// |-------|----------------------|
128 /// |`as_` |`&self` or `&mut self`|
130 /// |`into_`|`self` |
131 /// |`is_` |`&self` or none |
132 /// |`to_` |`&self` |
134 /// **Why is this bad?** Consistency breeds readability. If you follow the
135 /// conventions, your users won't be surprised that they, e.g., need to supply a
136 /// mutable reference to a `as_..` function.
138 /// **Known problems:** None.
143 /// fn as_str(self) -> &str {
148 pub WRONG_SELF_CONVENTION,
150 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
153 declare_clippy_lint! {
154 /// **What it does:** This is the same as
155 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
157 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
159 /// **Known problems:** Actually *renaming* the function may break clients if
160 /// the function is part of the public interface. In that case, be mindful of
161 /// the stability guarantees you've given your users.
167 /// pub fn as_str(self) -> &'a str {
172 pub WRONG_PUB_SELF_CONVENTION,
174 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
177 declare_clippy_lint! {
178 /// **What it does:** Checks for usage of `ok().expect(..)`.
180 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
181 /// directly to get a better error message.
183 /// **Known problems:** The error type needs to implement `Debug`
187 /// x.ok().expect("why did I do this again?")
191 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
194 declare_clippy_lint! {
195 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
197 /// **Why is this bad?** Readability, this can be written more concisely as
198 /// `_.map_or(_, _)`.
200 /// **Known problems:** The order of the arguments is not in execution order
204 /// # let x = Some(1);
205 /// x.map(|a| a + 1).unwrap_or(0);
207 pub OPTION_MAP_UNWRAP_OR,
209 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`"
212 declare_clippy_lint! {
213 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
215 /// **Why is this bad?** Readability, this can be written more concisely as
216 /// `_.map_or_else(_, _)`.
218 /// **Known problems:** The order of the arguments is not in execution order.
222 /// # let x = Some(1);
223 /// # fn some_function() -> usize { 1 }
224 /// x.map(|a| a + 1).unwrap_or_else(some_function);
226 pub OPTION_MAP_UNWRAP_OR_ELSE,
228 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`"
231 declare_clippy_lint! {
232 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
234 /// **Why is this bad?** Readability, this can be written more concisely as
235 /// `result.ok().map_or_else(_, _)`.
237 /// **Known problems:** None.
241 /// # let x: Result<usize, ()> = Ok(1);
242 /// # fn some_function(foo: ()) -> usize { 1 }
243 /// x.map(|a| a + 1).unwrap_or_else(some_function);
245 pub RESULT_MAP_UNWRAP_OR_ELSE,
247 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `.ok().map_or_else(g, f)`"
250 declare_clippy_lint! {
251 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
253 /// **Why is this bad?** Readability, this can be written more concisely as
256 /// **Known problems:** The order of the arguments is not in execution order.
260 /// opt.map_or(None, |a| a + 1)
262 pub OPTION_MAP_OR_NONE,
264 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
267 declare_clippy_lint! {
268 /// **What it does:** Checks for usage of `_.filter(_).next()`.
270 /// **Why is this bad?** Readability, this can be written more concisely as
273 /// **Known problems:** None.
277 /// # let vec = vec![1];
278 /// vec.iter().filter(|x| **x == 0).next();
282 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
285 declare_clippy_lint! {
286 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
288 /// **Why is this bad?** Readability, this can be written more concisely as a
289 /// single method call.
291 /// **Known problems:**
295 /// let vec = vec![vec![1]];
296 /// vec.iter().map(|x| x.iter()).flatten();
300 "using combinations of `flatten` and `map` which can usually be written as a single method call"
303 declare_clippy_lint! {
304 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
305 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
307 /// **Why is this bad?** Readability, this can be written more concisely as a
308 /// single method call.
310 /// **Known problems:** Often requires a condition + Option/Iterator creation
311 /// inside the closure.
315 /// let vec = vec![1];
316 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
320 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
323 declare_clippy_lint! {
324 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
326 /// **Why is this bad?** Readability, this can be written more concisely as a
327 /// single method call.
329 /// **Known problems:** None
333 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
335 /// Can be written as
338 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
342 "using combination of `filter_map` and `next` which can usually be written as a single method call"
345 declare_clippy_lint! {
346 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
348 /// **Why is this bad?** Readability, this can be written more concisely as a
349 /// single method call.
351 /// **Known problems:** Often requires a condition + Option/Iterator creation
352 /// inside the closure.
356 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
358 /// Can be written as
360 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
364 "using a combination of `find` and `map` can usually be written as a single method call"
367 declare_clippy_lint! {
368 /// **What it does:** Checks for an iterator search (such as `find()`,
369 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
371 /// **Why is this bad?** Readability, this can be written more concisely as
374 /// **Known problems:** None.
378 /// # let vec = vec![1];
379 /// vec.iter().find(|x| **x == 0).is_some();
383 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
386 declare_clippy_lint! {
387 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
388 /// if it starts with a given char.
390 /// **Why is this bad?** Readability, this can be written more concisely as
391 /// `_.starts_with(_)`.
393 /// **Known problems:** None.
397 /// let name = "foo";
398 /// name.chars().next() == Some('_');
402 "using `.chars().next()` to check if a string starts with a char"
405 declare_clippy_lint! {
406 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
407 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
408 /// `unwrap_or_default` instead.
410 /// **Why is this bad?** The function will always be called and potentially
411 /// allocate an object acting as the default.
413 /// **Known problems:** If the function has side-effects, not calling it will
414 /// change the semantic of the program, but you shouldn't rely on that anyway.
418 /// # let foo = Some(String::new());
419 /// foo.unwrap_or(String::new());
421 /// this can instead be written:
423 /// # let foo = Some(String::new());
424 /// foo.unwrap_or_else(String::new);
428 /// # let foo = Some(String::new());
429 /// foo.unwrap_or_default();
433 "using any `*or` method with a function call, which suggests `*or_else`"
436 declare_clippy_lint! {
437 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
438 /// etc., and suggests to use `unwrap_or_else` instead
440 /// **Why is this bad?** The function will always be called.
442 /// **Known problems:** If the function has side-effects, not calling it will
443 /// change the semantics of the program, but you shouldn't rely on that anyway.
447 /// # let foo = Some(String::new());
448 /// # let err_code = "418";
449 /// # let err_msg = "I'm a teapot";
450 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
454 /// # let foo = Some(String::new());
455 /// # let err_code = "418";
456 /// # let err_msg = "I'm a teapot";
457 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
459 /// this can instead be written:
461 /// # let foo = Some(String::new());
462 /// # let err_code = "418";
463 /// # let err_msg = "I'm a teapot";
464 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
468 "using any `expect` method with a function call"
471 declare_clippy_lint! {
472 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
474 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
475 /// generics, not for using the `clone` method on a concrete type.
477 /// **Known problems:** None.
485 "using `clone` on a `Copy` type"
488 declare_clippy_lint! {
489 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
490 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
491 /// function syntax instead (e.g., `Rc::clone(foo)`).
493 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
494 /// can obscure the fact that only the pointer is being cloned, not the underlying
499 /// # use std::rc::Rc;
500 /// let x = Rc::new(1);
503 pub CLONE_ON_REF_PTR,
505 "using 'clone' on a ref-counted pointer"
508 declare_clippy_lint! {
509 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
511 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
512 /// cloning the underlying `T`.
514 /// **Known problems:** None.
521 /// let z = y.clone();
522 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
525 pub CLONE_DOUBLE_REF,
527 "using `clone` on `&&T`"
530 declare_clippy_lint! {
531 /// **What it does:** Checks for `new` not returning `Self`.
533 /// **Why is this bad?** As a convention, `new` methods are used to make a new
534 /// instance of a type.
536 /// **Known problems:** None.
541 /// fn new(..) -> NotAFoo {
547 "not returning `Self` in a `new` method"
550 declare_clippy_lint! {
551 /// **What it does:** Checks for string methods that receive a single-character
552 /// `str` as an argument, e.g., `_.split("x")`.
554 /// **Why is this bad?** Performing these methods using a `char` is faster than
557 /// **Known problems:** Does not catch multi-byte unicode characters.
560 /// `_.split("x")` could be `_.split('x')`
561 pub SINGLE_CHAR_PATTERN,
563 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
566 declare_clippy_lint! {
567 /// **What it does:** Checks for getting the inner pointer of a temporary
570 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
571 /// as the `CString` is alive.
573 /// **Known problems:** None.
577 /// let c_str = CString::new("foo").unwrap().as_ptr();
579 /// call_some_ffi_func(c_str);
582 /// Here `c_str` point to a freed address. The correct use would be:
584 /// let c_str = CString::new("foo").unwrap();
586 /// call_some_ffi_func(c_str.as_ptr());
589 pub TEMPORARY_CSTRING_AS_PTR,
591 "getting the inner pointer of a temporary `CString`"
594 declare_clippy_lint! {
595 /// **What it does:** Checks for use of `.iter().nth()` (and the related
596 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
598 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
601 /// **Known problems:** None.
605 /// let some_vec = vec![0, 1, 2, 3];
606 /// let bad_vec = some_vec.iter().nth(3);
607 /// let bad_slice = &some_vec[..].iter().nth(3);
609 /// The correct use would be:
611 /// let some_vec = vec![0, 1, 2, 3];
612 /// let bad_vec = some_vec.get(3);
613 /// let bad_slice = &some_vec[..].get(3);
617 "using `.iter().nth()` on a standard library type with O(1) element access"
620 declare_clippy_lint! {
621 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
623 /// **Why is this bad?** `.nth(x)` is cleaner
625 /// **Known problems:** None.
629 /// let some_vec = vec![0, 1, 2, 3];
630 /// let bad_vec = some_vec.iter().skip(3).next();
631 /// let bad_slice = &some_vec[..].iter().skip(3).next();
633 /// The correct use would be:
635 /// let some_vec = vec![0, 1, 2, 3];
636 /// let bad_vec = some_vec.iter().nth(3);
637 /// let bad_slice = &some_vec[..].iter().nth(3);
641 "using `.skip(x).next()` on an iterator"
644 declare_clippy_lint! {
645 /// **What it does:** Checks for use of `.get().unwrap()` (or
646 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
648 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
651 /// **Known problems:** Not a replacement for error handling: Using either
652 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
653 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
654 /// temporary placeholder for dealing with the `Option` type, then this does
655 /// not mitigate the need for error handling. If there is a chance that `.get()`
656 /// will be `None` in your program, then it is advisable that the `None` case
657 /// is handled in a future refactor instead of using `.unwrap()` or the Index
662 /// let mut some_vec = vec![0, 1, 2, 3];
663 /// let last = some_vec.get(3).unwrap();
664 /// *some_vec.get_mut(0).unwrap() = 1;
666 /// The correct use would be:
668 /// let mut some_vec = vec![0, 1, 2, 3];
669 /// let last = some_vec[3];
674 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
677 declare_clippy_lint! {
678 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
679 /// `&str` or `String`.
681 /// **Why is this bad?** `.push_str(s)` is clearer
683 /// **Known problems:** None.
688 /// let def = String::from("def");
689 /// let mut s = String::new();
690 /// s.extend(abc.chars());
691 /// s.extend(def.chars());
693 /// The correct use would be:
696 /// let def = String::from("def");
697 /// let mut s = String::new();
699 /// s.push_str(&def);
701 pub STRING_EXTEND_CHARS,
703 "using `x.extend(s.chars())` where s is a `&str` or `String`"
706 declare_clippy_lint! {
707 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
710 /// **Why is this bad?** `.to_vec()` is clearer
712 /// **Known problems:** None.
716 /// let s = [1, 2, 3, 4, 5];
717 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
719 /// The better use would be:
721 /// let s = [1, 2, 3, 4, 5];
722 /// let s2: Vec<isize> = s.to_vec();
724 pub ITER_CLONED_COLLECT,
726 "using `.cloned().collect()` on slice to create a `Vec`"
729 declare_clippy_lint! {
730 /// **What it does:** Checks for usage of `.chars().last()` or
731 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
733 /// **Why is this bad?** Readability, this can be written more concisely as
734 /// `_.ends_with(_)`.
736 /// **Known problems:** None.
740 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
744 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
747 declare_clippy_lint! {
748 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
749 /// types before and after the call are the same.
751 /// **Why is this bad?** The call is unnecessary.
753 /// **Known problems:** None.
757 /// # fn do_stuff(x: &[i32]) {}
758 /// let x: &[i32] = &[1, 2, 3, 4, 5];
759 /// do_stuff(x.as_ref());
761 /// The correct use would be:
763 /// # fn do_stuff(x: &[i32]) {}
764 /// let x: &[i32] = &[1, 2, 3, 4, 5];
769 "using `as_ref` where the types before and after the call are the same"
772 declare_clippy_lint! {
773 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
774 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
775 /// `sum` or `product`.
777 /// **Why is this bad?** Readability.
779 /// **Known problems:** False positive in pattern guards. Will be resolved once
780 /// non-lexical lifetimes are stable.
784 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
786 /// This could be written as:
788 /// let _ = (0..3).any(|x| x > 2);
790 pub UNNECESSARY_FOLD,
792 "using `fold` when a more succinct alternative exists"
795 declare_clippy_lint! {
796 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
797 /// More specifically it checks if the closure provided is only performing one of the
798 /// filter or map operations and suggests the appropriate option.
800 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
801 /// operation is being performed.
803 /// **Known problems:** None
807 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
809 /// As there is no transformation of the argument this could be written as:
811 /// let _ = (0..3).filter(|&x| x > 2);
815 /// let _ = (0..4).filter_map(i32::checked_abs);
817 /// As there is no conditional check on the argument this could be written as:
819 /// let _ = (0..4).map(i32::checked_abs);
821 pub UNNECESSARY_FILTER_MAP,
823 "using `filter_map` when a more succinct alternative exists"
826 declare_clippy_lint! {
827 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
830 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
831 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
832 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
833 /// like calling `iter` would. Furthermore, when the standard library actually
834 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
835 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
836 /// and the code will be broken.
838 /// **Known problems:** None
843 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
845 pub INTO_ITER_ON_ARRAY,
847 "using `.into_iter()` on an array"
850 declare_clippy_lint! {
851 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
854 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
855 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
856 /// `iter_mut` directly.
858 /// **Known problems:** None
863 /// let _ = (&vec![3, 4, 5]).into_iter();
865 pub INTO_ITER_ON_REF,
867 "using `.into_iter()` on a reference"
870 declare_lint_pass!(Methods => [
873 SHOULD_IMPLEMENT_TRAIT,
874 WRONG_SELF_CONVENTION,
875 WRONG_PUB_SELF_CONVENTION,
877 OPTION_MAP_UNWRAP_OR,
878 OPTION_MAP_UNWRAP_OR_ELSE,
879 RESULT_MAP_UNWRAP_OR_ELSE,
891 TEMPORARY_CSTRING_AS_PTR,
904 UNNECESSARY_FILTER_MAP,
909 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
910 #[allow(clippy::cognitive_complexity)]
911 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
912 if in_macro(expr.span) {
916 let (method_names, arg_lists) = method_calls(expr, 2);
917 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
918 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
920 match method_names.as_slice() {
921 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
922 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
923 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
924 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
925 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
926 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
927 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
928 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
929 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
930 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
931 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
932 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
933 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
934 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
935 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
936 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
937 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
938 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
939 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
940 ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
941 lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
943 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
944 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
945 ["next", "skip"] => lint_iter_skip_next(cx, expr),
946 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
947 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
948 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
949 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
950 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
955 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
956 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
957 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
959 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
960 if args.len() == 1 && method_call.ident.name == sym!(clone) {
961 lint_clone_on_copy(cx, expr, &args[0], self_ty);
962 lint_clone_on_ref_ptr(cx, expr, &args[0]);
966 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
967 for &(method, pos) in &PATTERN_METHODS {
968 if method_call.ident.name.as_str() == method && args.len() > pos {
969 lint_single_char_pattern(cx, expr, &args[pos]);
973 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
974 lint_into_iter(cx, expr, self_ty, *method_span);
979 hir::ExprKind::Binary(op, ref lhs, ref rhs)
980 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
982 let mut info = BinaryExprInfo {
986 eq: op.node == hir::BinOpKind::Eq,
988 lint_binary_expr_with_method_call(cx, &mut info);
994 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, impl_item: &'tcx hir::ImplItem) {
995 if in_external_macro(cx.sess(), impl_item.span) {
998 let name = impl_item.ident.name.as_str();
999 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1000 let item = cx.tcx.hir().expect_item(parent);
1001 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1002 let ty = cx.tcx.type_of(def_id);
1004 if let hir::ImplItemKind::Method(ref sig, id) = impl_item.node;
1005 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1006 if let hir::ItemKind::Impl(_, _, _, _, None, _, _) = item.node;
1008 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1009 let method_sig = cx.tcx.fn_sig(method_def_id);
1010 let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
1012 let first_arg_ty = &method_sig.inputs().iter().next();
1014 // check conventions w.r.t. conversion method names and predicates
1015 if let Some(first_arg_ty) = first_arg_ty {
1017 if cx.access_levels.is_exported(impl_item.hir_id) {
1018 // check missing trait implementations
1019 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
1020 if name == method_name &&
1021 sig.decl.inputs.len() == n_args &&
1022 out_type.matches(cx, &sig.decl.output) &&
1023 self_kind.matches(cx, ty, first_arg_ty) {
1024 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, impl_item.span, &format!(
1025 "defining a method called `{}` on this type; consider implementing \
1026 the `{}` trait or choosing a less ambiguous name", name, trait_name));
1031 for &(ref conv, self_kinds) in &CONVENTIONS {
1032 if conv.check(&name) {
1035 .any(|k| k.matches(cx, ty, first_arg_ty)) {
1036 let lint = if item.vis.node.is_pub() {
1037 WRONG_PUB_SELF_CONVENTION
1039 WRONG_SELF_CONVENTION
1044 &format!("methods called `{}` usually take {}; consider choosing a less \
1048 .map(|k| k.description())
1049 .collect::<Vec<_>>()
1053 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1062 if let hir::ImplItemKind::Method(_, _) = impl_item.node {
1063 let ret_ty = return_ty(cx, impl_item.hir_id);
1065 // walk the return type and check for Self (this does not check associated types)
1066 for inner_type in ret_ty.walk() {
1067 if same_tys(cx, ty, inner_type) {
1072 // if return type is impl trait, check the associated types
1073 if let ty::Opaque(def_id, _) = ret_ty.sty {
1074 // one of the associated types must be Self
1075 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1077 (Predicate::Projection(poly_projection_predicate), _) => {
1078 let binder = poly_projection_predicate.ty();
1079 let associated_type = binder.skip_binder();
1080 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
1082 // if the associated type is self, early return and do not trigger lint
1083 if associated_type_is_self_type {
1092 if name == "new" && !same_tys(cx, ret_ty, ty) {
1097 "methods called `new` usually return `Self`",
1104 /// Checks for the `OR_FUN_CALL` lint.
1105 #[allow(clippy::too_many_lines)]
1106 fn lint_or_fun_call<'a, 'tcx>(
1107 cx: &LateContext<'a, 'tcx>,
1111 args: &'tcx [hir::Expr],
1113 // Searches an expression for method calls or function calls that aren't ctors
1114 struct FunCallFinder<'a, 'tcx> {
1115 cx: &'a LateContext<'a, 'tcx>,
1119 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1120 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1121 let call_found = match &expr.node {
1122 // ignore enum and struct constructors
1123 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1124 hir::ExprKind::MethodCall(..) => true,
1129 // don't lint for constant values
1130 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1131 let promotable = self
1134 .rvalue_promotable_map(owner_def)
1135 .contains(&expr.hir_id.local_id);
1142 intravisit::walk_expr(self, expr);
1146 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1147 intravisit::NestedVisitorMap::None
1151 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1152 fn check_unwrap_or_default(
1153 cx: &LateContext<'_, '_>,
1156 self_expr: &hir::Expr,
1165 if name == "unwrap_or" {
1166 if let hir::ExprKind::Path(ref qpath) = fun.node {
1167 let path = &*last_path_segment(qpath).ident.as_str();
1169 if ["default", "new"].contains(&path) {
1170 let arg_ty = cx.tables.expr_ty(arg);
1171 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1177 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1178 let mut applicability = Applicability::MachineApplicable;
1183 &format!("use of `{}` followed by a call to `{}`", name, path),
1186 "{}.unwrap_or_default()",
1187 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1200 /// Checks for `*or(foo())`.
1201 #[allow(clippy::too_many_arguments)]
1202 fn check_general_case<'a, 'tcx>(
1203 cx: &LateContext<'a, 'tcx>,
1207 self_expr: &hir::Expr,
1208 arg: &'tcx hir::Expr,
1212 // (path, fn_has_argument, methods, suffix)
1213 let know_types: &[(&[_], _, &[_], _)] = &[
1214 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1215 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1216 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1217 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1220 // early check if the name is one we care about
1221 if know_types.iter().all(|k| !k.2.contains(&name)) {
1225 let mut finder = FunCallFinder { cx: &cx, found: false };
1226 finder.visit_expr(&arg);
1231 let self_ty = cx.tables.expr_ty(self_expr);
1233 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1234 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1236 (fn_has_arguments, poss, suffix)
1241 if !poss.contains(&name) {
1245 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1246 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1247 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1248 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1250 let span_replace_word = method_span.with_hi(span.hi());
1255 &format!("use of `{}` followed by a function call", name),
1257 format!("{}_{}({})", name, suffix, sugg),
1258 Applicability::HasPlaceholders,
1262 if args.len() == 2 {
1263 match args[1].node {
1264 hir::ExprKind::Call(ref fun, ref or_args) => {
1265 let or_has_args = !or_args.is_empty();
1266 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1279 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1286 !or_args.is_empty(),
1294 /// Checks for the `EXPECT_FUN_CALL` lint.
1295 #[allow(clippy::too_many_lines)]
1296 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1297 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1299 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1300 let mut arg_root = arg;
1302 arg_root = match &arg_root.node {
1303 hir::ExprKind::AddrOf(_, expr) => expr,
1304 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1305 if call_args.len() == 1
1306 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1308 let arg_type = cx.tables.expr_ty(&call_args[0]);
1309 let base_type = walk_ptrs_ty(arg_type);
1310 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1324 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1325 // converted to string.
1326 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1327 let arg_ty = cx.tables.expr_ty(arg);
1328 if match_type(cx, arg_ty, &paths::STRING) {
1331 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1332 if ty.sty == ty::Str {
1339 fn generate_format_arg_snippet(
1340 cx: &LateContext<'_, '_>,
1342 applicability: &mut Applicability,
1344 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1345 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1346 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1347 return format_arg_expr_tup
1349 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1358 fn is_call(node: &hir::ExprKind) -> bool {
1360 hir::ExprKind::AddrOf(_, expr) => {
1363 hir::ExprKind::Call(..)
1364 | hir::ExprKind::MethodCall(..)
1365 // These variants are debatable or require further examination
1366 | hir::ExprKind::Match(..)
1367 | hir::ExprKind::Block{ .. } => true,
1372 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1376 let receiver_type = cx.tables.expr_ty(&args[0]);
1377 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1379 } else if match_type(cx, receiver_type, &paths::RESULT) {
1385 let arg_root = get_arg_root(cx, &args[1]);
1387 let span_replace_word = method_span.with_hi(expr.span.hi());
1389 let mut applicability = Applicability::MachineApplicable;
1391 //Special handling for `format!` as arg_root
1392 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1393 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1394 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1395 let fmt_spec = &format_args[0];
1396 let fmt_args = &format_args[1];
1398 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1400 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1402 let sugg = args.join(", ");
1408 &format!("use of `{}` followed by a function call", name),
1410 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1419 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1420 if requires_to_string(cx, arg_root) {
1421 arg_root_snippet.to_mut().push_str(".to_string()");
1428 &format!("use of `{}` followed by a function call", name),
1430 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1435 /// Checks for the `CLONE_ON_COPY` lint.
1436 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1437 let ty = cx.tables.expr_ty(expr);
1438 if let ty::Ref(_, inner, _) = arg_ty.sty {
1439 if let ty::Ref(_, innermost, _) = inner.sty {
1444 "using `clone` on a double-reference; \
1445 this will copy the reference instead of cloning the inner type",
1447 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1448 let mut ty = innermost;
1450 while let ty::Ref(_, inner, _) = ty.sty {
1454 let refs: String = iter::repeat('&').take(n + 1).collect();
1455 let derefs: String = iter::repeat('*').take(n).collect();
1456 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1459 "try dereferencing it",
1460 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1461 Applicability::MaybeIncorrect,
1465 "or try being explicit about what type to clone",
1467 Applicability::MaybeIncorrect,
1472 return; // don't report clone_on_copy
1476 if is_copy(cx, ty) {
1478 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1479 // x.clone() might have dereferenced x, possibly through Deref impls
1480 if cx.tables.expr_ty(arg) == ty {
1481 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1483 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1484 match cx.tcx.hir().get(parent) {
1485 hir::Node::Expr(parent) => match parent.node {
1486 // &*x is a nop, &x.clone() is not
1487 hir::ExprKind::AddrOf(..) |
1488 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1489 hir::ExprKind::MethodCall(..) => return,
1492 hir::Node::Stmt(stmt) => {
1493 if let hir::StmtKind::Local(ref loc) = stmt.node {
1494 if let hir::PatKind::Ref(..) = loc.pat.node {
1495 // let ref y = *x borrows x, let ref y = x.clone() does not
1503 let deref_count = cx
1505 .expr_adjustments(arg)
1508 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1515 let derefs: String = iter::repeat('*').take(deref_count).collect();
1516 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1521 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1522 if let Some((text, snip)) = snip {
1523 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1529 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1530 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1532 if let ty::Adt(_, subst) = obj_ty.sty {
1533 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1535 } else if match_type(cx, obj_ty, &paths::ARC) {
1537 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1547 "using '.clone()' on a ref-counted pointer",
1550 "{}::<{}>::clone(&{})",
1553 snippet(cx, arg.span, "_")
1555 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1560 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1562 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1563 let target = &arglists[0][0];
1564 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1565 let ref_str = if self_ty.sty == ty::Str {
1567 } else if match_type(cx, self_ty, &paths::STRING) {
1573 let mut applicability = Applicability::MachineApplicable;
1576 STRING_EXTEND_CHARS,
1578 "calling `.extend(_.chars())`",
1581 "{}.push_str({}{})",
1582 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1584 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1591 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1592 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1593 if match_type(cx, obj_ty, &paths::STRING) {
1594 lint_string_extend(cx, expr, args);
1598 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1600 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1602 if let hir::ExprKind::Path(ref path) = fun.node;
1603 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1604 if match_def_path(cx, did, &paths::CSTRING_NEW);
1608 TEMPORARY_CSTRING_AS_PTR,
1610 "you are getting the inner pointer of a temporary `CString`",
1612 db.note("that pointer will be invalid outside this expression");
1613 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1619 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1620 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1621 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1622 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1625 ITER_CLONED_COLLECT,
1627 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1630 ".to_vec()".to_string(),
1631 Applicability::MachineApplicable,
1638 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1639 fn check_fold_with_op(
1640 cx: &LateContext<'_, '_>,
1641 fold_args: &[hir::Expr],
1643 replacement_method_name: &str,
1644 replacement_has_args: bool,
1647 // Extract the body of the closure passed to fold
1648 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1649 let closure_body = cx.tcx.hir().body(body_id);
1650 let closure_expr = remove_blocks(&closure_body.value);
1652 // Check if the closure body is of the form `acc <op> some_expr(x)`
1653 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1654 if bin_op.node == op;
1656 // Extract the names of the two arguments to the closure
1657 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1658 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1660 if match_var(&*left_expr, first_arg_ident);
1661 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1664 // Span containing `.fold(...)`
1665 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1666 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1668 let mut applicability = Applicability::MachineApplicable;
1669 let sugg = if replacement_has_args {
1671 ".{replacement}(|{s}| {r})",
1672 replacement = replacement_method_name,
1673 s = second_arg_ident,
1674 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1679 replacement = replacement_method_name,
1687 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1688 "this `.fold` can be written more succinctly using another method",
1697 // Check that this is a call to Iterator::fold rather than just some function called fold
1698 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1703 fold_args.len() == 3,
1704 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1707 // Check if the first argument to .fold is a suitable literal
1708 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1710 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1711 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1712 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1713 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1719 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1720 let mut_str = if is_mut { "_mut" } else { "" };
1721 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1723 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1725 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1728 return; // caller is not a type that we want to lint
1736 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1737 mut_str, caller_type
1742 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1743 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1744 // because they do not implement `IndexMut`
1745 let mut applicability = Applicability::MachineApplicable;
1746 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1747 let get_args_str = if get_args.len() > 1 {
1748 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1750 return; // not linting on a .get().unwrap() chain or variant
1753 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1754 needs_ref = get_args_str.parse::<usize>().is_ok();
1756 } else if match_type(cx, expr_ty, &paths::VEC) {
1757 needs_ref = get_args_str.parse::<usize>().is_ok();
1759 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1760 needs_ref = get_args_str.parse::<usize>().is_ok();
1762 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1765 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1769 return; // caller is not a type that we want to lint
1772 let mut span = expr.span;
1774 // Handle the case where the result is immediately dereferenced
1775 // by not requiring ref and pulling the dereference into the
1779 if let Some(parent) = get_parent_expr(cx, expr);
1780 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1787 let mut_str = if is_mut { "_mut" } else { "" };
1788 let borrow_str = if !needs_ref {
1801 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1802 mut_str, caller_type
1808 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1815 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1816 // lint if caller of skip is an Iterator
1817 if match_trait_method(cx, expr, &paths::ITERATOR) {
1822 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1827 fn derefs_to_slice<'a, 'tcx>(
1828 cx: &LateContext<'a, 'tcx>,
1829 expr: &'tcx hir::Expr,
1831 ) -> Option<&'tcx hir::Expr> {
1832 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1834 ty::Slice(_) => true,
1835 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1836 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1837 ty::Array(_, size) => size.eval_usize(cx.tcx, cx.param_env) < 32,
1838 ty::Ref(_, inner, _) => may_slice(cx, inner),
1843 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1844 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1851 ty::Slice(_) => Some(expr),
1852 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1853 ty::Ref(_, inner, _) => {
1854 if may_slice(cx, inner) {
1865 /// lint use of `unwrap()` for `Option`s and `Result`s
1866 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1867 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1869 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1870 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1871 } else if match_type(cx, obj_ty, &paths::RESULT) {
1872 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1877 if let Some((lint, kind, none_value)) = mess {
1883 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1884 using expect() to provide a better panic \
1892 /// lint use of `ok().expect()` for `Result`s
1893 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1894 // lint if the caller of `ok()` is a `Result`
1895 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1896 let result_type = cx.tables.expr_ty(&ok_args[0]);
1897 if let Some(error_type) = get_error_type(cx, result_type) {
1898 if has_debug_impl(error_type, cx) {
1903 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1910 /// lint use of `map().flatten()` for `Iterators`
1911 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1912 // lint if caller of `.map().flatten()` is an Iterator
1913 if match_trait_method(cx, expr, &paths::ITERATOR) {
1914 let msg = "called `map(..).flatten()` on an `Iterator`. \
1915 This is more succinctly expressed by calling `.flat_map(..)`";
1916 let self_snippet = snippet(cx, map_args[0].span, "..");
1917 let func_snippet = snippet(cx, map_args[1].span, "..");
1918 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1919 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1922 "try using flat_map instead",
1924 Applicability::MachineApplicable,
1930 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1931 fn lint_map_unwrap_or_else<'a, 'tcx>(
1932 cx: &LateContext<'a, 'tcx>,
1933 expr: &'tcx hir::Expr,
1934 map_args: &'tcx [hir::Expr],
1935 unwrap_args: &'tcx [hir::Expr],
1937 // lint if the caller of `map()` is an `Option`
1938 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1939 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1941 if is_option || is_result {
1942 // Don't make a suggestion that may fail to compile due to mutably borrowing
1943 // the same variable twice.
1944 let map_mutated_vars = mutated_variables(&map_args[0], cx);
1945 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
1946 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
1947 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
1955 let msg = if is_option {
1956 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1957 `map_or_else(g, f)` instead"
1959 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1960 `ok().map_or_else(g, f)` instead"
1962 // get snippets for args to map() and unwrap_or_else()
1963 let map_snippet = snippet(cx, map_args[1].span, "..");
1964 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1965 // lint, with note if neither arg is > 1 line and both map() and
1966 // unwrap_or_else() have the same span
1967 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1968 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1969 if same_span && !multiline {
1973 OPTION_MAP_UNWRAP_OR_ELSE
1975 RESULT_MAP_UNWRAP_OR_ELSE
1981 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1984 if is_result { "ok()." } else { "" }
1987 } else if same_span && multiline {
1991 OPTION_MAP_UNWRAP_OR_ELSE
1993 RESULT_MAP_UNWRAP_OR_ELSE
2002 /// lint use of `_.map_or(None, _)` for `Option`s
2003 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
2004 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
2005 // check if the first non-self argument to map_or() is None
2006 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
2007 match_qpath(qpath, &paths::OPTION_NONE)
2012 if map_or_arg_is_none {
2014 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
2015 `and_then(f)` instead";
2016 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
2017 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
2018 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
2019 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
2022 "try using and_then instead",
2024 Applicability::MachineApplicable, // snippet
2031 /// lint use of `filter().next()` for `Iterators`
2032 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2033 // lint if caller of `.filter().next()` is an Iterator
2034 if match_trait_method(cx, expr, &paths::ITERATOR) {
2035 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2036 `.find(p)` instead.";
2037 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2038 if filter_snippet.lines().count() <= 1 {
2039 // add note if not multi-line
2046 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2049 span_lint(cx, FILTER_NEXT, expr.span, msg);
2054 /// lint use of `filter().map()` for `Iterators`
2055 fn lint_filter_map<'a, 'tcx>(
2056 cx: &LateContext<'a, 'tcx>,
2057 expr: &'tcx hir::Expr,
2058 _filter_args: &'tcx [hir::Expr],
2059 _map_args: &'tcx [hir::Expr],
2061 // lint if caller of `.filter().map()` is an Iterator
2062 if match_trait_method(cx, expr, &paths::ITERATOR) {
2063 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2064 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2065 span_lint(cx, FILTER_MAP, expr.span, msg);
2069 /// lint use of `filter_map().next()` for `Iterators`
2070 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2071 if match_trait_method(cx, expr, &paths::ITERATOR) {
2072 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2073 `.find_map(p)` instead.";
2074 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2075 if filter_snippet.lines().count() <= 1 {
2082 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2085 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2090 /// lint use of `find().map()` for `Iterators`
2091 fn lint_find_map<'a, 'tcx>(
2092 cx: &LateContext<'a, 'tcx>,
2093 expr: &'tcx hir::Expr,
2094 _find_args: &'tcx [hir::Expr],
2095 map_args: &'tcx [hir::Expr],
2097 // lint if caller of `.filter().map()` is an Iterator
2098 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2099 let msg = "called `find(p).map(q)` on an `Iterator`. \
2100 This is more succinctly expressed by calling `.find_map(..)` instead.";
2101 span_lint(cx, FIND_MAP, expr.span, msg);
2105 /// lint use of `filter().map()` for `Iterators`
2106 fn lint_filter_map_map<'a, 'tcx>(
2107 cx: &LateContext<'a, 'tcx>,
2108 expr: &'tcx hir::Expr,
2109 _filter_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, expr, &paths::ITERATOR) {
2114 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2115 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2116 span_lint(cx, FILTER_MAP, expr.span, msg);
2120 /// lint use of `filter().flat_map()` for `Iterators`
2121 fn lint_filter_flat_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().flat_map()` is an Iterator
2128 if match_trait_method(cx, expr, &paths::ITERATOR) {
2129 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2130 This is more succinctly expressed by calling `.flat_map(..)` \
2131 and filtering by returning an empty Iterator.";
2132 span_lint(cx, FILTER_MAP, expr.span, msg);
2136 /// lint use of `filter_map().flat_map()` for `Iterators`
2137 fn lint_filter_map_flat_map<'a, 'tcx>(
2138 cx: &LateContext<'a, 'tcx>,
2139 expr: &'tcx hir::Expr,
2140 _filter_args: &'tcx [hir::Expr],
2141 _map_args: &'tcx [hir::Expr],
2143 // lint if caller of `.filter_map().flat_map()` is an Iterator
2144 if match_trait_method(cx, expr, &paths::ITERATOR) {
2145 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2146 This is more succinctly expressed by calling `.flat_map(..)` \
2147 and filtering by returning an empty Iterator.";
2148 span_lint(cx, FILTER_MAP, expr.span, msg);
2152 /// lint searching an Iterator followed by `is_some()`
2153 fn lint_search_is_some<'a, 'tcx>(
2154 cx: &LateContext<'a, 'tcx>,
2155 expr: &'tcx hir::Expr,
2156 search_method: &str,
2157 search_args: &'tcx [hir::Expr],
2158 is_some_args: &'tcx [hir::Expr],
2160 // lint if caller of search is an Iterator
2161 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2163 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2164 expressed by calling `any()`.",
2167 let search_snippet = snippet(cx, search_args[1].span, "..");
2168 if search_snippet.lines().count() <= 1 {
2169 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2170 let any_search_snippet = if_chain! {
2171 if search_method == "find";
2172 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2173 let closure_body = cx.tcx.hir().body(body_id);
2174 if let Some(closure_arg) = closure_body.arguments.get(0);
2175 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2177 Some(search_snippet.replacen('&', "", 1))
2182 // add note if not multi-line
2190 "replace `{0}({1}).is_some()` with `any({2})`",
2193 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2197 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2202 /// Used for `lint_binary_expr_with_method_call`.
2203 #[derive(Copy, Clone)]
2204 struct BinaryExprInfo<'a> {
2205 expr: &'a hir::Expr,
2206 chain: &'a hir::Expr,
2207 other: &'a hir::Expr,
2211 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2212 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2213 macro_rules! lint_with_both_lhs_and_rhs {
2214 ($func:ident, $cx:expr, $info:ident) => {
2215 if !$func($cx, $info) {
2216 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2217 if $func($cx, $info) {
2224 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2225 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2226 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2227 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2230 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2232 cx: &LateContext<'_, '_>,
2233 info: &BinaryExprInfo<'_>,
2234 chain_methods: &[&str],
2235 lint: &'static Lint,
2239 if let Some(args) = method_chain_args(info.chain, chain_methods);
2240 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2241 if arg_char.len() == 1;
2242 if let hir::ExprKind::Path(ref qpath) = fun.node;
2243 if let Some(segment) = single_segment_path(qpath);
2244 if segment.ident.name == sym!(Some);
2246 let mut applicability = Applicability::MachineApplicable;
2247 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2249 if self_ty.sty != ty::Str {
2257 &format!("you should use the `{}` method", suggest),
2259 format!("{}{}.{}({})",
2260 if info.eq { "" } else { "!" },
2261 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2263 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2274 /// Checks for the `CHARS_NEXT_CMP` lint.
2275 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2276 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2279 /// Checks for the `CHARS_LAST_CMP` lint.
2280 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2281 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2284 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2288 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2289 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2290 cx: &LateContext<'a, 'tcx>,
2291 info: &BinaryExprInfo<'_>,
2292 chain_methods: &[&str],
2293 lint: &'static Lint,
2297 if let Some(args) = method_chain_args(info.chain, chain_methods);
2298 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2299 if let ast::LitKind::Char(c) = lit.node;
2301 let mut applicability = Applicability::MachineApplicable;
2306 &format!("you should use the `{}` method", suggest),
2308 format!("{}{}.{}('{}')",
2309 if info.eq { "" } else { "!" },
2310 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2323 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2324 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2325 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2328 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2329 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2330 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2333 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2337 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2338 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2340 if let hir::ExprKind::Lit(lit) = &arg.node;
2341 if let ast::LitKind::Str(r, style) = lit.node;
2342 if r.as_str().len() == 1;
2344 let mut applicability = Applicability::MachineApplicable;
2345 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2346 let ch = if let ast::StrStyle::Raw(nhash) = style {
2347 let nhash = nhash as usize;
2348 // for raw string: r##"a"##
2349 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
2351 // for regular string: "a"
2352 &snip[1..(snip.len() - 1)]
2354 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
2357 SINGLE_CHAR_PATTERN,
2359 "single-character string constant used as pattern",
2360 "try using a char instead",
2368 /// Checks for the `USELESS_ASREF` lint.
2369 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2370 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2371 // check if the call is to the actual `AsRef` or `AsMut` trait
2372 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2373 // check if the type after `as_ref` or `as_mut` is the same as before
2374 let recvr = &as_ref_args[0];
2375 let rcv_ty = cx.tables.expr_ty(recvr);
2376 let res_ty = cx.tables.expr_ty(expr);
2377 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2378 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2379 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2380 // allow the `as_ref` or `as_mut` if it is followed by another method call
2382 if let Some(parent) = get_parent_expr(cx, expr);
2383 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2384 if span != &expr.span;
2390 let mut applicability = Applicability::MachineApplicable;
2395 &format!("this call to `{}` does nothing", call_name),
2397 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2404 fn ty_has_iter_method(
2405 cx: &LateContext<'_, '_>,
2406 self_ref_ty: Ty<'_>,
2407 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2408 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2409 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2414 let mutbl = match self_ref_ty.sty {
2415 ty::Ref(_, _, mutbl) => mutbl,
2416 _ => unreachable!(),
2418 let method_name = match mutbl {
2419 hir::MutImmutable => "iter",
2420 hir::MutMutable => "iter_mut",
2422 Some((lint, ty_name, method_name))
2428 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2429 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2432 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2438 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2442 method_name.to_string(),
2443 Applicability::MachineApplicable,
2448 /// Given a `Result<T, E>` type, return its error type (`E`).
2449 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2450 if let ty::Adt(_, substs) = ty.sty {
2451 if match_type(cx, ty, &paths::RESULT) {
2452 substs.types().nth(1)
2461 /// This checks whether a given type is known to implement Debug.
2462 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2463 match cx.tcx.lang_items().debug_trait() {
2464 Some(debug) => implements_trait(cx, ty, debug, &[]),
2471 StartsWith(&'static str),
2475 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2476 (Convention::Eq("new"), &[SelfKind::No]),
2477 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2478 (Convention::StartsWith("from_"), &[SelfKind::No]),
2479 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2480 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2481 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2482 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2486 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2487 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2488 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2489 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2490 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2491 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2492 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2493 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2494 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2495 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2496 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2497 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2498 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2499 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2500 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2501 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2502 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2503 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2504 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2505 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2506 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2507 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2508 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2509 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2510 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2511 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2512 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2513 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2514 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2515 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2516 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2520 const PATTERN_METHODS: [(&str, usize); 17] = [
2528 ("split_terminator", 1),
2529 ("rsplit_terminator", 1),
2534 ("match_indices", 1),
2535 ("rmatch_indices", 1),
2536 ("trim_start_matches", 1),
2537 ("trim_end_matches", 1),
2540 #[derive(Clone, Copy, PartialEq, Debug)]
2549 fn matches<'a>(self, cx: &LateContext<'_, 'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
2551 cx: &LateContext<'_, 'a>,
2552 mutability: hir::Mutability,
2556 if let ty::Ref(_, t, m) = ty.sty {
2557 return m == mutability && t == parent_ty;
2560 let trait_path = match mutability {
2561 hir::Mutability::MutImmutable => &paths::ASREF_TRAIT,
2562 hir::Mutability::MutMutable => &paths::ASMUT_TRAIT,
2565 let trait_def_id = get_trait_def_id(cx, trait_path).expect("trait def id not found");
2566 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
2570 Self::Value => ty == parent_ty,
2572 matches_ref(cx, hir::Mutability::MutImmutable, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty)
2574 Self::RefMut => matches_ref(cx, hir::Mutability::MutMutable, parent_ty, ty),
2575 Self::No => ty != parent_ty,
2579 fn description(self) -> &'static str {
2581 Self::Value => "self by value",
2582 Self::Ref => "self by reference",
2583 Self::RefMut => "self by mutable reference",
2584 Self::No => "no self",
2590 fn check(&self, other: &str) -> bool {
2592 Self::Eq(this) => this == other,
2593 Self::StartsWith(this) => other.starts_with(this) && this != other,
2598 impl fmt::Display for Convention {
2599 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2601 Self::Eq(this) => this.fmt(f),
2602 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2607 #[derive(Clone, Copy)]
2616 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2617 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2619 (Self::Unit, &hir::DefaultReturn(_)) => true,
2620 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2621 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2622 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2623 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2629 fn is_bool(ty: &hir::Ty) -> bool {
2630 if let hir::TyKind::Path(ref p) = ty.node {
2631 match_qpath(p, &["bool"])