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.
46 pub OPTION_UNWRAP_USED,
48 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
51 declare_clippy_lint! {
52 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
54 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
55 /// values. Normally, you want to implement more sophisticated error handling,
56 /// and propagate errors upwards with `try!`.
58 /// Even if you want to panic on errors, not all `Error`s implement good
59 /// messages on display. Therefore, it may be beneficial to look at the places
60 /// where they may get displayed. Activate this lint to do just that.
62 /// **Known problems:** None.
68 pub RESULT_UNWRAP_USED,
70 "using `Result.unwrap()`, which might be better handled"
73 declare_clippy_lint! {
74 /// **What it does:** Checks for methods that should live in a trait
75 /// implementation of a `std` trait (see [llogiq's blog
76 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
77 /// information) instead of an inherent implementation.
79 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
80 /// the code, often with very little cost. Also people seeing a `mul(...)`
82 /// may expect `*` to work equally, so you should have good reason to disappoint
85 /// **Known problems:** None.
91 /// fn add(&self, other: &X) -> X {
96 pub SHOULD_IMPLEMENT_TRAIT,
98 "defining a method that should be implementing a std trait"
101 declare_clippy_lint! {
102 /// **What it does:** Checks for methods with certain name prefixes and which
103 /// doesn't match how self is taken. The actual rules are:
105 /// |Prefix |`self` taken |
106 /// |-------|----------------------|
107 /// |`as_` |`&self` or `&mut self`|
109 /// |`into_`|`self` |
110 /// |`is_` |`&self` or none |
111 /// |`to_` |`&self` |
113 /// **Why is this bad?** Consistency breeds readability. If you follow the
114 /// conventions, your users won't be surprised that they, e.g., need to supply a
115 /// mutable reference to a `as_..` function.
117 /// **Known problems:** None.
122 /// fn as_str(self) -> &str {
127 pub WRONG_SELF_CONVENTION,
129 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
132 declare_clippy_lint! {
133 /// **What it does:** This is the same as
134 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
136 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
138 /// **Known problems:** Actually *renaming* the function may break clients if
139 /// the function is part of the public interface. In that case, be mindful of
140 /// the stability guarantees you've given your users.
145 /// pub fn as_str(self) -> &str {
150 pub WRONG_PUB_SELF_CONVENTION,
152 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
155 declare_clippy_lint! {
156 /// **What it does:** Checks for usage of `ok().expect(..)`.
158 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
159 /// directly to get a better error message.
161 /// **Known problems:** The error type needs to implement `Debug`
165 /// x.ok().expect("why did I do this again?")
169 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
172 declare_clippy_lint! {
173 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
175 /// **Why is this bad?** Readability, this can be written more concisely as
176 /// `_.map_or(_, _)`.
178 /// **Known problems:** The order of the arguments is not in execution order
182 /// x.map(|a| a + 1).unwrap_or(0)
184 pub OPTION_MAP_UNWRAP_OR,
186 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`"
189 declare_clippy_lint! {
190 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
192 /// **Why is this bad?** Readability, this can be written more concisely as
193 /// `_.map_or_else(_, _)`.
195 /// **Known problems:** The order of the arguments is not in execution order.
199 /// x.map(|a| a + 1).unwrap_or_else(some_function)
201 pub OPTION_MAP_UNWRAP_OR_ELSE,
203 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`"
206 declare_clippy_lint! {
207 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
209 /// **Why is this bad?** Readability, this can be written more concisely as
210 /// `result.ok().map_or_else(_, _)`.
212 /// **Known problems:** None.
216 /// x.map(|a| a + 1).unwrap_or_else(some_function)
218 pub RESULT_MAP_UNWRAP_OR_ELSE,
220 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `.ok().map_or_else(g, f)`"
223 declare_clippy_lint! {
224 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
226 /// **Why is this bad?** Readability, this can be written more concisely as
229 /// **Known problems:** The order of the arguments is not in execution order.
233 /// opt.map_or(None, |a| a + 1)
235 pub OPTION_MAP_OR_NONE,
237 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
240 declare_clippy_lint! {
241 /// **What it does:** Checks for usage of `_.filter(_).next()`.
243 /// **Why is this bad?** Readability, this can be written more concisely as
246 /// **Known problems:** None.
250 /// iter.filter(|x| x == 0).next()
254 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
257 declare_clippy_lint! {
258 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
260 /// **Why is this bad?** Readability, this can be written more concisely as a
261 /// single method call.
263 /// **Known problems:**
267 /// iter.map(|x| x.iter()).flatten()
271 "using combinations of `flatten` and `map` which can usually be written as a single method call"
274 declare_clippy_lint! {
275 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
276 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
278 /// **Why is this bad?** Readability, this can be written more concisely as a
279 /// single method call.
281 /// **Known problems:** Often requires a condition + Option/Iterator creation
282 /// inside the closure.
286 /// iter.filter(|x| x == 0).map(|x| x * 2)
290 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
293 declare_clippy_lint! {
294 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
296 /// **Why is this bad?** Readability, this can be written more concisely as a
297 /// single method call.
299 /// **Known problems:** None
303 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
305 /// Can be written as
308 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
312 "using combination of `filter_map` and `next` which can usually be written as a single method call"
315 declare_clippy_lint! {
316 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
318 /// **Why is this bad?** Readability, this can be written more concisely as a
319 /// single method call.
321 /// **Known problems:** Often requires a condition + Option/Iterator creation
322 /// inside the closure.
326 /// (0..3).find(|x| x == 2).map(|x| x * 2);
328 /// Can be written as
330 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
334 "using a combination of `find` and `map` can usually be written as a single method call"
337 declare_clippy_lint! {
338 /// **What it does:** Checks for an iterator search (such as `find()`,
339 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
341 /// **Why is this bad?** Readability, this can be written more concisely as
344 /// **Known problems:** None.
348 /// iter.find(|x| x == 0).is_some()
352 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
355 declare_clippy_lint! {
356 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
357 /// if it starts with a given char.
359 /// **Why is this bad?** Readability, this can be written more concisely as
360 /// `_.starts_with(_)`.
362 /// **Known problems:** None.
366 /// name.chars().next() == Some('_')
370 "using `.chars().next()` to check if a string starts with a char"
373 declare_clippy_lint! {
374 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
375 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
376 /// `unwrap_or_default` instead.
378 /// **Why is this bad?** The function will always be called and potentially
379 /// allocate an object acting as the default.
381 /// **Known problems:** If the function has side-effects, not calling it will
382 /// change the semantic of the program, but you shouldn't rely on that anyway.
386 /// # let foo = Some(String::new());
387 /// foo.unwrap_or(String::new());
389 /// this can instead be written:
391 /// # let foo = Some(String::new());
392 /// foo.unwrap_or_else(String::new);
396 /// # let foo = Some(String::new());
397 /// foo.unwrap_or_default();
401 "using any `*or` method with a function call, which suggests `*or_else`"
404 declare_clippy_lint! {
405 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
406 /// etc., and suggests to use `unwrap_or_else` instead
408 /// **Why is this bad?** The function will always be called.
410 /// **Known problems:** If the function has side-effects, not calling it will
411 /// change the semantics of the program, but you shouldn't rely on that anyway.
415 /// # let foo = Some(String::new());
416 /// # let err_code = "418";
417 /// # let err_msg = "I'm a teapot";
418 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
422 /// # let foo = Some(String::new());
423 /// # let err_code = "418";
424 /// # let err_msg = "I'm a teapot";
425 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
427 /// this can instead be written:
429 /// # let foo = Some(String::new());
430 /// # let err_code = "418";
431 /// # let err_msg = "I'm a teapot";
432 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
436 "using any `expect` method with a function call"
439 declare_clippy_lint! {
440 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
442 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
443 /// generics, not for using the `clone` method on a concrete type.
445 /// **Known problems:** None.
453 "using `clone` on a `Copy` type"
456 declare_clippy_lint! {
457 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
458 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
459 /// function syntax instead (e.g., `Rc::clone(foo)`).
461 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
462 /// can obscure the fact that only the pointer is being cloned, not the underlying
469 pub CLONE_ON_REF_PTR,
471 "using 'clone' on a ref-counted pointer"
474 declare_clippy_lint! {
475 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
477 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
478 /// cloning the underlying `T`.
480 /// **Known problems:** None.
487 /// let z = y.clone();
488 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
491 pub CLONE_DOUBLE_REF,
493 "using `clone` on `&&T`"
496 declare_clippy_lint! {
497 /// **What it does:** Checks for `new` not returning `Self`.
499 /// **Why is this bad?** As a convention, `new` methods are used to make a new
500 /// instance of a type.
502 /// **Known problems:** None.
507 /// fn new(..) -> NotAFoo {
513 "not returning `Self` in a `new` method"
516 declare_clippy_lint! {
517 /// **What it does:** Checks for string methods that receive a single-character
518 /// `str` as an argument, e.g., `_.split("x")`.
520 /// **Why is this bad?** Performing these methods using a `char` is faster than
523 /// **Known problems:** Does not catch multi-byte unicode characters.
526 /// `_.split("x")` could be `_.split('x')`
527 pub SINGLE_CHAR_PATTERN,
529 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
532 declare_clippy_lint! {
533 /// **What it does:** Checks for getting the inner pointer of a temporary
536 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
537 /// as the `CString` is alive.
539 /// **Known problems:** None.
543 /// let c_str = CString::new("foo").unwrap().as_ptr();
545 /// call_some_ffi_func(c_str);
548 /// Here `c_str` point to a freed address. The correct use would be:
550 /// let c_str = CString::new("foo").unwrap();
552 /// call_some_ffi_func(c_str.as_ptr());
555 pub TEMPORARY_CSTRING_AS_PTR,
557 "getting the inner pointer of a temporary `CString`"
560 declare_clippy_lint! {
561 /// **What it does:** Checks for use of `.iter().nth()` (and the related
562 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
564 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
567 /// **Known problems:** None.
571 /// let some_vec = vec![0, 1, 2, 3];
572 /// let bad_vec = some_vec.iter().nth(3);
573 /// let bad_slice = &some_vec[..].iter().nth(3);
575 /// The correct use would be:
577 /// let some_vec = vec![0, 1, 2, 3];
578 /// let bad_vec = some_vec.get(3);
579 /// let bad_slice = &some_vec[..].get(3);
583 "using `.iter().nth()` on a standard library type with O(1) element access"
586 declare_clippy_lint! {
587 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
589 /// **Why is this bad?** `.nth(x)` is cleaner
591 /// **Known problems:** None.
595 /// let some_vec = vec![0, 1, 2, 3];
596 /// let bad_vec = some_vec.iter().skip(3).next();
597 /// let bad_slice = &some_vec[..].iter().skip(3).next();
599 /// The correct use would be:
601 /// let some_vec = vec![0, 1, 2, 3];
602 /// let bad_vec = some_vec.iter().nth(3);
603 /// let bad_slice = &some_vec[..].iter().nth(3);
607 "using `.skip(x).next()` on an iterator"
610 declare_clippy_lint! {
611 /// **What it does:** Checks for use of `.get().unwrap()` (or
612 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
614 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
617 /// **Known problems:** Not a replacement for error handling: Using either
618 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
619 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
620 /// temporary placeholder for dealing with the `Option` type, then this does
621 /// not mitigate the need for error handling. If there is a chance that `.get()`
622 /// will be `None` in your program, then it is advisable that the `None` case
623 /// is handled in a future refactor instead of using `.unwrap()` or the Index
628 /// let mut some_vec = vec![0, 1, 2, 3];
629 /// let last = some_vec.get(3).unwrap();
630 /// *some_vec.get_mut(0).unwrap() = 1;
632 /// The correct use would be:
634 /// let mut some_vec = vec![0, 1, 2, 3];
635 /// let last = some_vec[3];
640 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
643 declare_clippy_lint! {
644 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
645 /// `&str` or `String`.
647 /// **Why is this bad?** `.push_str(s)` is clearer
649 /// **Known problems:** None.
654 /// let def = String::from("def");
655 /// let mut s = String::new();
656 /// s.extend(abc.chars());
657 /// s.extend(def.chars());
659 /// The correct use would be:
662 /// let def = String::from("def");
663 /// let mut s = String::new();
665 /// s.push_str(&def);
667 pub STRING_EXTEND_CHARS,
669 "using `x.extend(s.chars())` where s is a `&str` or `String`"
672 declare_clippy_lint! {
673 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
676 /// **Why is this bad?** `.to_vec()` is clearer
678 /// **Known problems:** None.
682 /// let s = [1, 2, 3, 4, 5];
683 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
685 /// The better use would be:
687 /// let s = [1, 2, 3, 4, 5];
688 /// let s2: Vec<isize> = s.to_vec();
690 pub ITER_CLONED_COLLECT,
692 "using `.cloned().collect()` on slice to create a `Vec`"
695 declare_clippy_lint! {
696 /// **What it does:** Checks for usage of `.chars().last()` or
697 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
699 /// **Why is this bad?** Readability, this can be written more concisely as
700 /// `_.ends_with(_)`.
702 /// **Known problems:** None.
706 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
710 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
713 declare_clippy_lint! {
714 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
715 /// types before and after the call are the same.
717 /// **Why is this bad?** The call is unnecessary.
719 /// **Known problems:** None.
723 /// let x: &[i32] = &[1, 2, 3, 4, 5];
724 /// do_stuff(x.as_ref());
726 /// The correct use would be:
728 /// let x: &[i32] = &[1, 2, 3, 4, 5];
733 "using `as_ref` where the types before and after the call are the same"
736 declare_clippy_lint! {
737 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
738 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
739 /// `sum` or `product`.
741 /// **Why is this bad?** Readability.
743 /// **Known problems:** False positive in pattern guards. Will be resolved once
744 /// non-lexical lifetimes are stable.
748 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
750 /// This could be written as:
752 /// let _ = (0..3).any(|x| x > 2);
754 pub UNNECESSARY_FOLD,
756 "using `fold` when a more succinct alternative exists"
759 declare_clippy_lint! {
760 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
761 /// More specifically it checks if the closure provided is only performing one of the
762 /// filter or map operations and suggests the appropriate option.
764 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
765 /// operation is being performed.
767 /// **Known problems:** None
771 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
773 /// As there is no transformation of the argument this could be written as:
775 /// let _ = (0..3).filter(|&x| x > 2);
779 /// let _ = (0..4).filter_map(i32::checked_abs);
781 /// As there is no conditional check on the argument this could be written as:
783 /// let _ = (0..4).map(i32::checked_abs);
785 pub UNNECESSARY_FILTER_MAP,
787 "using `filter_map` when a more succinct alternative exists"
790 declare_clippy_lint! {
791 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
794 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
795 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
796 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
797 /// like calling `iter` would. Furthermore, when the standard library actually
798 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
799 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
800 /// and the code will be broken.
802 /// **Known problems:** None
807 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
809 pub INTO_ITER_ON_ARRAY,
811 "using `.into_iter()` on an array"
814 declare_clippy_lint! {
815 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
818 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
819 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
820 /// `iter_mut` directly.
822 /// **Known problems:** None
827 /// let _ = (&vec![3, 4, 5]).into_iter();
829 pub INTO_ITER_ON_REF,
831 "using `.into_iter()` on a reference"
834 declare_lint_pass!(Methods => [
837 SHOULD_IMPLEMENT_TRAIT,
838 WRONG_SELF_CONVENTION,
839 WRONG_PUB_SELF_CONVENTION,
841 OPTION_MAP_UNWRAP_OR,
842 OPTION_MAP_UNWRAP_OR_ELSE,
843 RESULT_MAP_UNWRAP_OR_ELSE,
855 TEMPORARY_CSTRING_AS_PTR,
868 UNNECESSARY_FILTER_MAP,
873 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
874 #[allow(clippy::cognitive_complexity)]
875 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
876 if in_macro(expr.span) {
880 let (method_names, arg_lists) = method_calls(expr, 2);
881 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
882 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
884 match method_names.as_slice() {
885 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
886 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
887 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
888 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
889 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
890 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
891 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
892 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
893 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
894 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
895 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
896 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
897 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
898 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
899 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
900 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
901 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
902 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
903 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
904 ["as_ptr", "unwrap"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
905 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
906 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
907 ["next", "skip"] => lint_iter_skip_next(cx, expr),
908 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
909 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
910 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
911 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
912 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
917 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
918 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
919 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
921 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
922 if args.len() == 1 && method_call.ident.name == sym!(clone) {
923 lint_clone_on_copy(cx, expr, &args[0], self_ty);
924 lint_clone_on_ref_ptr(cx, expr, &args[0]);
928 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
929 for &(method, pos) in &PATTERN_METHODS {
930 if method_call.ident.name.as_str() == method && args.len() > pos {
931 lint_single_char_pattern(cx, expr, &args[pos]);
935 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
936 lint_into_iter(cx, expr, self_ty, *method_span);
941 hir::ExprKind::Binary(op, ref lhs, ref rhs)
942 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
944 let mut info = BinaryExprInfo {
948 eq: op.node == hir::BinOpKind::Eq,
950 lint_binary_expr_with_method_call(cx, &mut info);
956 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
957 if in_external_macro(cx.sess(), implitem.span) {
960 let name = implitem.ident.name.as_str();
961 let parent = cx.tcx.hir().get_parent_item(implitem.hir_id);
962 let item = cx.tcx.hir().expect_item(parent);
963 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
964 let ty = cx.tcx.type_of(def_id);
966 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
967 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
968 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
969 if let hir::ItemKind::Impl(_, _, _, _, None, ref self_ty, _) = item.node;
971 if cx.access_levels.is_exported(implitem.hir_id) {
972 // check missing trait implementations
973 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
974 if name == method_name &&
975 sig.decl.inputs.len() == n_args &&
976 out_type.matches(cx, &sig.decl.output) &&
977 self_kind.matches(cx, first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
978 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
979 "defining a method called `{}` on this type; consider implementing \
980 the `{}` trait or choosing a less ambiguous name", name, trait_name));
985 // check conventions w.r.t. conversion method names and predicates
986 let is_copy = is_copy(cx, ty);
987 for &(ref conv, self_kinds) in &CONVENTIONS {
988 if conv.check(&name) {
991 .any(|k| k.matches(cx, first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics)) {
992 let lint = if item.vis.node.is_pub() {
993 WRONG_PUB_SELF_CONVENTION
995 WRONG_SELF_CONVENTION
1000 &format!("methods called `{}` usually take {}; consider choosing a less \
1004 .map(|k| k.description())
1005 .collect::<Vec<_>>()
1009 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1017 if let hir::ImplItemKind::Method(_, _) = implitem.node {
1018 let ret_ty = return_ty(cx, implitem.hir_id);
1020 // walk the return type and check for Self (this does not check associated types)
1021 for inner_type in ret_ty.walk() {
1022 if same_tys(cx, ty, inner_type) {
1027 // if return type is impl trait, check the associated types
1028 if let ty::Opaque(def_id, _) = ret_ty.sty {
1029 // one of the associated types must be Self
1030 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1032 (Predicate::Projection(poly_projection_predicate), _) => {
1033 let binder = poly_projection_predicate.ty();
1034 let associated_type = binder.skip_binder();
1035 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
1037 // if the associated type is self, early return and do not trigger lint
1038 if associated_type_is_self_type {
1047 if name == "new" && !same_tys(cx, ret_ty, ty) {
1052 "methods called `new` usually return `Self`",
1059 /// Checks for the `OR_FUN_CALL` lint.
1060 #[allow(clippy::too_many_lines)]
1061 fn lint_or_fun_call<'a, 'tcx>(
1062 cx: &LateContext<'a, 'tcx>,
1066 args: &'tcx [hir::Expr],
1068 // Searches an expression for method calls or function calls that aren't ctors
1069 struct FunCallFinder<'a, 'tcx> {
1070 cx: &'a LateContext<'a, 'tcx>,
1074 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1075 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1076 let call_found = match &expr.node {
1077 // ignore enum and struct constructors
1078 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1079 hir::ExprKind::MethodCall(..) => true,
1084 // don't lint for constant values
1085 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1086 let promotable = self
1089 .rvalue_promotable_map(owner_def)
1090 .contains(&expr.hir_id.local_id);
1097 intravisit::walk_expr(self, expr);
1101 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1102 intravisit::NestedVisitorMap::None
1106 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1107 fn check_unwrap_or_default(
1108 cx: &LateContext<'_, '_>,
1111 self_expr: &hir::Expr,
1120 if name == "unwrap_or" {
1121 if let hir::ExprKind::Path(ref qpath) = fun.node {
1122 let path = &*last_path_segment(qpath).ident.as_str();
1124 if ["default", "new"].contains(&path) {
1125 let arg_ty = cx.tables.expr_ty(arg);
1126 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1132 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1133 let mut applicability = Applicability::MachineApplicable;
1138 &format!("use of `{}` followed by a call to `{}`", name, path),
1141 "{}.unwrap_or_default()",
1142 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1155 /// Checks for `*or(foo())`.
1156 #[allow(clippy::too_many_arguments)]
1157 fn check_general_case<'a, 'tcx>(
1158 cx: &LateContext<'a, 'tcx>,
1162 self_expr: &hir::Expr,
1163 arg: &'tcx hir::Expr,
1167 // (path, fn_has_argument, methods, suffix)
1168 let know_types: &[(&[_], _, &[_], _)] = &[
1169 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1170 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1171 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1172 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1175 // early check if the name is one we care about
1176 if know_types.iter().all(|k| !k.2.contains(&name)) {
1180 let mut finder = FunCallFinder { cx: &cx, found: false };
1181 finder.visit_expr(&arg);
1186 let self_ty = cx.tables.expr_ty(self_expr);
1188 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1189 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1191 (fn_has_arguments, poss, suffix)
1196 if !poss.contains(&name) {
1200 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1201 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1202 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1203 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1205 let span_replace_word = method_span.with_hi(span.hi());
1210 &format!("use of `{}` followed by a function call", name),
1212 format!("{}_{}({})", name, suffix, sugg),
1213 Applicability::HasPlaceholders,
1217 if args.len() == 2 {
1218 match args[1].node {
1219 hir::ExprKind::Call(ref fun, ref or_args) => {
1220 let or_has_args = !or_args.is_empty();
1221 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1234 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1241 !or_args.is_empty(),
1249 /// Checks for the `EXPECT_FUN_CALL` lint.
1250 #[allow(clippy::too_many_lines)]
1251 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1252 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1254 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1255 let mut arg_root = arg;
1257 arg_root = match &arg_root.node {
1258 hir::ExprKind::AddrOf(_, expr) => expr,
1259 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1260 if call_args.len() == 1
1261 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1263 let arg_type = cx.tables.expr_ty(&call_args[0]);
1264 let base_type = walk_ptrs_ty(arg_type);
1265 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1279 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1280 // converted to string.
1281 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1282 let arg_ty = cx.tables.expr_ty(arg);
1283 if match_type(cx, arg_ty, &paths::STRING) {
1286 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1287 if ty.sty == ty::Str {
1294 fn generate_format_arg_snippet(
1295 cx: &LateContext<'_, '_>,
1297 applicability: &mut Applicability,
1299 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1300 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1301 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1302 return format_arg_expr_tup
1304 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1313 fn is_call(node: &hir::ExprKind) -> bool {
1315 hir::ExprKind::AddrOf(_, expr) => {
1318 hir::ExprKind::Call(..)
1319 | hir::ExprKind::MethodCall(..)
1320 // These variants are debatable or require further examination
1321 | hir::ExprKind::Match(..)
1322 | hir::ExprKind::Block{ .. } => true,
1327 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1331 let receiver_type = cx.tables.expr_ty(&args[0]);
1332 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1334 } else if match_type(cx, receiver_type, &paths::RESULT) {
1340 let arg_root = get_arg_root(cx, &args[1]);
1342 let span_replace_word = method_span.with_hi(expr.span.hi());
1344 let mut applicability = Applicability::MachineApplicable;
1346 //Special handling for `format!` as arg_root
1347 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1348 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1349 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1350 let fmt_spec = &format_args[0];
1351 let fmt_args = &format_args[1];
1353 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1355 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1357 let sugg = args.join(", ");
1363 &format!("use of `{}` followed by a function call", name),
1365 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1374 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1375 if requires_to_string(cx, arg_root) {
1376 arg_root_snippet.to_mut().push_str(".to_string()");
1383 &format!("use of `{}` followed by a function call", name),
1385 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1390 /// Checks for the `CLONE_ON_COPY` lint.
1391 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1392 let ty = cx.tables.expr_ty(expr);
1393 if let ty::Ref(_, inner, _) = arg_ty.sty {
1394 if let ty::Ref(_, innermost, _) = inner.sty {
1399 "using `clone` on a double-reference; \
1400 this will copy the reference instead of cloning the inner type",
1402 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1403 let mut ty = innermost;
1405 while let ty::Ref(_, inner, _) = ty.sty {
1409 let refs: String = iter::repeat('&').take(n + 1).collect();
1410 let derefs: String = iter::repeat('*').take(n).collect();
1411 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1414 "try dereferencing it",
1415 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1416 Applicability::MaybeIncorrect,
1420 "or try being explicit about what type to clone",
1422 Applicability::MaybeIncorrect,
1427 return; // don't report clone_on_copy
1431 if is_copy(cx, ty) {
1433 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1434 // x.clone() might have dereferenced x, possibly through Deref impls
1435 if cx.tables.expr_ty(arg) == ty {
1436 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1438 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1439 match cx.tcx.hir().get(parent) {
1440 hir::Node::Expr(parent) => match parent.node {
1441 // &*x is a nop, &x.clone() is not
1442 hir::ExprKind::AddrOf(..) |
1443 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1444 hir::ExprKind::MethodCall(..) => return,
1447 hir::Node::Stmt(stmt) => {
1448 if let hir::StmtKind::Local(ref loc) = stmt.node {
1449 if let hir::PatKind::Ref(..) = loc.pat.node {
1450 // let ref y = *x borrows x, let ref y = x.clone() does not
1458 let deref_count = cx
1460 .expr_adjustments(arg)
1463 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1470 let derefs: String = iter::repeat('*').take(deref_count).collect();
1471 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1476 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1477 if let Some((text, snip)) = snip {
1478 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1484 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1485 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1487 if let ty::Adt(_, subst) = obj_ty.sty {
1488 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1490 } else if match_type(cx, obj_ty, &paths::ARC) {
1492 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1502 "using '.clone()' on a ref-counted pointer",
1505 "{}::<{}>::clone(&{})",
1508 snippet(cx, arg.span, "_")
1510 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1515 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1517 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1518 let target = &arglists[0][0];
1519 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1520 let ref_str = if self_ty.sty == ty::Str {
1522 } else if match_type(cx, self_ty, &paths::STRING) {
1528 let mut applicability = Applicability::MachineApplicable;
1531 STRING_EXTEND_CHARS,
1533 "calling `.extend(_.chars())`",
1536 "{}.push_str({}{})",
1537 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1539 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1546 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1547 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1548 if match_type(cx, obj_ty, &paths::STRING) {
1549 lint_string_extend(cx, expr, args);
1553 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1555 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1557 if let hir::ExprKind::Path(ref path) = fun.node;
1558 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1559 if match_def_path(cx, did, &paths::CSTRING_NEW);
1563 TEMPORARY_CSTRING_AS_PTR,
1565 "you are getting the inner pointer of a temporary `CString`",
1567 db.note("that pointer will be invalid outside this expression");
1568 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1574 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1575 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1576 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1577 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1580 ITER_CLONED_COLLECT,
1582 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1585 ".to_vec()".to_string(),
1586 Applicability::MachineApplicable,
1593 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1594 fn check_fold_with_op(
1595 cx: &LateContext<'_, '_>,
1596 fold_args: &[hir::Expr],
1598 replacement_method_name: &str,
1599 replacement_has_args: bool,
1602 // Extract the body of the closure passed to fold
1603 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1604 let closure_body = cx.tcx.hir().body(body_id);
1605 let closure_expr = remove_blocks(&closure_body.value);
1607 // Check if the closure body is of the form `acc <op> some_expr(x)`
1608 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1609 if bin_op.node == op;
1611 // Extract the names of the two arguments to the closure
1612 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1613 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1615 if match_var(&*left_expr, first_arg_ident);
1616 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1619 // Span containing `.fold(...)`
1620 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1621 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1623 let mut applicability = Applicability::MachineApplicable;
1624 let sugg = if replacement_has_args {
1626 ".{replacement}(|{s}| {r})",
1627 replacement = replacement_method_name,
1628 s = second_arg_ident,
1629 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1634 replacement = replacement_method_name,
1642 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1643 "this `.fold` can be written more succinctly using another method",
1652 // Check that this is a call to Iterator::fold rather than just some function called fold
1653 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1658 fold_args.len() == 3,
1659 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1662 // Check if the first argument to .fold is a suitable literal
1663 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1665 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1666 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1667 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1668 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1674 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1675 let mut_str = if is_mut { "_mut" } else { "" };
1676 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1678 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1680 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1683 return; // caller is not a type that we want to lint
1691 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1692 mut_str, caller_type
1697 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1698 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1699 // because they do not implement `IndexMut`
1700 let mut applicability = Applicability::MachineApplicable;
1701 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1702 let get_args_str = if get_args.len() > 1 {
1703 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1705 return; // not linting on a .get().unwrap() chain or variant
1708 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1709 needs_ref = get_args_str.parse::<usize>().is_ok();
1711 } else if match_type(cx, expr_ty, &paths::VEC) {
1712 needs_ref = get_args_str.parse::<usize>().is_ok();
1714 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1715 needs_ref = get_args_str.parse::<usize>().is_ok();
1717 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1720 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1724 return; // caller is not a type that we want to lint
1727 let mut span = expr.span;
1729 // Handle the case where the result is immediately dereferenced
1730 // by not requiring ref and pulling the dereference into the
1734 if let Some(parent) = get_parent_expr(cx, expr);
1735 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1742 let mut_str = if is_mut { "_mut" } else { "" };
1743 let borrow_str = if !needs_ref {
1756 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1757 mut_str, caller_type
1763 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1770 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1771 // lint if caller of skip is an Iterator
1772 if match_trait_method(cx, expr, &paths::ITERATOR) {
1777 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1782 fn derefs_to_slice<'a, 'tcx>(
1783 cx: &LateContext<'a, 'tcx>,
1784 expr: &'tcx hir::Expr,
1786 ) -> Option<&'tcx hir::Expr> {
1787 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1789 ty::Slice(_) => true,
1790 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1791 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1792 ty::Array(_, size) => size.assert_usize(cx.tcx).expect("array length") < 32,
1793 ty::Ref(_, inner, _) => may_slice(cx, inner),
1798 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1799 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1806 ty::Slice(_) => Some(expr),
1807 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1808 ty::Ref(_, inner, _) => {
1809 if may_slice(cx, inner) {
1820 /// lint use of `unwrap()` for `Option`s and `Result`s
1821 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1822 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1824 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1825 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1826 } else if match_type(cx, obj_ty, &paths::RESULT) {
1827 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1832 if let Some((lint, kind, none_value)) = mess {
1838 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1839 using expect() to provide a better panic \
1847 /// lint use of `ok().expect()` for `Result`s
1848 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1849 // lint if the caller of `ok()` is a `Result`
1850 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1851 let result_type = cx.tables.expr_ty(&ok_args[0]);
1852 if let Some(error_type) = get_error_type(cx, result_type) {
1853 if has_debug_impl(error_type, cx) {
1858 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1865 /// lint use of `map().flatten()` for `Iterators`
1866 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1867 // lint if caller of `.map().flatten()` is an Iterator
1868 if match_trait_method(cx, expr, &paths::ITERATOR) {
1869 let msg = "called `map(..).flatten()` on an `Iterator`. \
1870 This is more succinctly expressed by calling `.flat_map(..)`";
1871 let self_snippet = snippet(cx, map_args[0].span, "..");
1872 let func_snippet = snippet(cx, map_args[1].span, "..");
1873 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1874 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1877 "try using flat_map instead",
1879 Applicability::MachineApplicable,
1885 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1886 fn lint_map_unwrap_or_else<'a, 'tcx>(
1887 cx: &LateContext<'a, 'tcx>,
1888 expr: &'tcx hir::Expr,
1889 map_args: &'tcx [hir::Expr],
1890 unwrap_args: &'tcx [hir::Expr],
1892 // lint if the caller of `map()` is an `Option`
1893 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1894 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1896 if is_option || is_result {
1897 // Don't make a suggestion that may fail to compile due to mutably borrowing
1898 // the same variable twice.
1899 let map_mutated_vars = mutated_variables(&map_args[0], cx);
1900 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
1901 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
1902 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
1910 let msg = if is_option {
1911 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1912 `map_or_else(g, f)` instead"
1914 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1915 `ok().map_or_else(g, f)` instead"
1917 // get snippets for args to map() and unwrap_or_else()
1918 let map_snippet = snippet(cx, map_args[1].span, "..");
1919 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1920 // lint, with note if neither arg is > 1 line and both map() and
1921 // unwrap_or_else() have the same span
1922 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1923 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1924 if same_span && !multiline {
1928 OPTION_MAP_UNWRAP_OR_ELSE
1930 RESULT_MAP_UNWRAP_OR_ELSE
1936 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1939 if is_result { "ok()." } else { "" }
1942 } else if same_span && multiline {
1946 OPTION_MAP_UNWRAP_OR_ELSE
1948 RESULT_MAP_UNWRAP_OR_ELSE
1957 /// lint use of `_.map_or(None, _)` for `Option`s
1958 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
1959 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
1960 // check if the first non-self argument to map_or() is None
1961 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
1962 match_qpath(qpath, &paths::OPTION_NONE)
1967 if map_or_arg_is_none {
1969 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
1970 `and_then(f)` instead";
1971 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
1972 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
1973 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
1974 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
1977 "try using and_then instead",
1979 Applicability::MachineApplicable, // snippet
1986 /// lint use of `filter().next()` for `Iterators`
1987 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
1988 // lint if caller of `.filter().next()` is an Iterator
1989 if match_trait_method(cx, expr, &paths::ITERATOR) {
1990 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
1991 `.find(p)` instead.";
1992 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1993 if filter_snippet.lines().count() <= 1 {
1994 // add note if not multi-line
2001 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2004 span_lint(cx, FILTER_NEXT, expr.span, msg);
2009 /// lint use of `filter().map()` for `Iterators`
2010 fn lint_filter_map<'a, 'tcx>(
2011 cx: &LateContext<'a, 'tcx>,
2012 expr: &'tcx hir::Expr,
2013 _filter_args: &'tcx [hir::Expr],
2014 _map_args: &'tcx [hir::Expr],
2016 // lint if caller of `.filter().map()` is an Iterator
2017 if match_trait_method(cx, expr, &paths::ITERATOR) {
2018 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2019 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2020 span_lint(cx, FILTER_MAP, expr.span, msg);
2024 /// lint use of `filter_map().next()` for `Iterators`
2025 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2026 if match_trait_method(cx, expr, &paths::ITERATOR) {
2027 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2028 `.find_map(p)` instead.";
2029 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2030 if filter_snippet.lines().count() <= 1 {
2037 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2040 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2045 /// lint use of `find().map()` for `Iterators`
2046 fn lint_find_map<'a, 'tcx>(
2047 cx: &LateContext<'a, 'tcx>,
2048 expr: &'tcx hir::Expr,
2049 _find_args: &'tcx [hir::Expr],
2050 map_args: &'tcx [hir::Expr],
2052 // lint if caller of `.filter().map()` is an Iterator
2053 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2054 let msg = "called `find(p).map(q)` on an `Iterator`. \
2055 This is more succinctly expressed by calling `.find_map(..)` instead.";
2056 span_lint(cx, FIND_MAP, expr.span, msg);
2060 /// lint use of `filter().map()` for `Iterators`
2061 fn lint_filter_map_map<'a, 'tcx>(
2062 cx: &LateContext<'a, 'tcx>,
2063 expr: &'tcx hir::Expr,
2064 _filter_args: &'tcx [hir::Expr],
2065 _map_args: &'tcx [hir::Expr],
2067 // lint if caller of `.filter().map()` is an Iterator
2068 if match_trait_method(cx, expr, &paths::ITERATOR) {
2069 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2070 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2071 span_lint(cx, FILTER_MAP, expr.span, msg);
2075 /// lint use of `filter().flat_map()` for `Iterators`
2076 fn lint_filter_flat_map<'a, 'tcx>(
2077 cx: &LateContext<'a, 'tcx>,
2078 expr: &'tcx hir::Expr,
2079 _filter_args: &'tcx [hir::Expr],
2080 _map_args: &'tcx [hir::Expr],
2082 // lint if caller of `.filter().flat_map()` is an Iterator
2083 if match_trait_method(cx, expr, &paths::ITERATOR) {
2084 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2085 This is more succinctly expressed by calling `.flat_map(..)` \
2086 and filtering by returning an empty Iterator.";
2087 span_lint(cx, FILTER_MAP, expr.span, msg);
2091 /// lint use of `filter_map().flat_map()` for `Iterators`
2092 fn lint_filter_map_flat_map<'a, 'tcx>(
2093 cx: &LateContext<'a, 'tcx>,
2094 expr: &'tcx hir::Expr,
2095 _filter_args: &'tcx [hir::Expr],
2096 _map_args: &'tcx [hir::Expr],
2098 // lint if caller of `.filter_map().flat_map()` is an Iterator
2099 if match_trait_method(cx, expr, &paths::ITERATOR) {
2100 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2101 This is more succinctly expressed by calling `.flat_map(..)` \
2102 and filtering by returning an empty Iterator.";
2103 span_lint(cx, FILTER_MAP, expr.span, msg);
2107 /// lint searching an Iterator followed by `is_some()`
2108 fn lint_search_is_some<'a, 'tcx>(
2109 cx: &LateContext<'a, 'tcx>,
2110 expr: &'tcx hir::Expr,
2111 search_method: &str,
2112 search_args: &'tcx [hir::Expr],
2113 is_some_args: &'tcx [hir::Expr],
2115 // lint if caller of search is an Iterator
2116 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2118 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2119 expressed by calling `any()`.",
2122 let search_snippet = snippet(cx, search_args[1].span, "..");
2123 if search_snippet.lines().count() <= 1 {
2124 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2125 let any_search_snippet = if_chain! {
2126 if search_method == "find";
2127 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2128 let closure_body = cx.tcx.hir().body(body_id);
2129 if let Some(closure_arg) = closure_body.arguments.get(0);
2130 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2132 Some(search_snippet.replacen('&', "", 1))
2137 // add note if not multi-line
2145 "replace `{0}({1}).is_some()` with `any({2})`",
2148 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2152 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2157 /// Used for `lint_binary_expr_with_method_call`.
2158 #[derive(Copy, Clone)]
2159 struct BinaryExprInfo<'a> {
2160 expr: &'a hir::Expr,
2161 chain: &'a hir::Expr,
2162 other: &'a hir::Expr,
2166 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2167 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2168 macro_rules! lint_with_both_lhs_and_rhs {
2169 ($func:ident, $cx:expr, $info:ident) => {
2170 if !$func($cx, $info) {
2171 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2172 if $func($cx, $info) {
2179 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2180 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2181 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2182 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2185 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2187 cx: &LateContext<'_, '_>,
2188 info: &BinaryExprInfo<'_>,
2189 chain_methods: &[&str],
2190 lint: &'static Lint,
2194 if let Some(args) = method_chain_args(info.chain, chain_methods);
2195 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2196 if arg_char.len() == 1;
2197 if let hir::ExprKind::Path(ref qpath) = fun.node;
2198 if let Some(segment) = single_segment_path(qpath);
2199 if segment.ident.name == sym!(Some);
2201 let mut applicability = Applicability::MachineApplicable;
2202 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2204 if self_ty.sty != ty::Str {
2212 &format!("you should use the `{}` method", suggest),
2214 format!("{}{}.{}({})",
2215 if info.eq { "" } else { "!" },
2216 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2218 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2229 /// Checks for the `CHARS_NEXT_CMP` lint.
2230 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2231 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2234 /// Checks for the `CHARS_LAST_CMP` lint.
2235 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2236 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2239 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2243 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2244 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2245 cx: &LateContext<'a, 'tcx>,
2246 info: &BinaryExprInfo<'_>,
2247 chain_methods: &[&str],
2248 lint: &'static Lint,
2252 if let Some(args) = method_chain_args(info.chain, chain_methods);
2253 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2254 if let ast::LitKind::Char(c) = lit.node;
2256 let mut applicability = Applicability::MachineApplicable;
2261 &format!("you should use the `{}` method", suggest),
2263 format!("{}{}.{}('{}')",
2264 if info.eq { "" } else { "!" },
2265 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2278 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2279 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2280 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2283 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2284 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2285 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2288 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2292 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2293 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2295 if let hir::ExprKind::Lit(lit) = &arg.node;
2296 if let ast::LitKind::Str(r, _) = lit.node;
2297 if r.as_str().len() == 1;
2299 let mut applicability = Applicability::MachineApplicable;
2300 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2301 let c = &snip[1..snip.len() - 1];
2302 let hint = format!("'{}'", if c == "'" { "\\'" } else { c });
2305 SINGLE_CHAR_PATTERN,
2307 "single-character string constant used as pattern",
2308 "try using a char instead",
2316 /// Checks for the `USELESS_ASREF` lint.
2317 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2318 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2319 // check if the call is to the actual `AsRef` or `AsMut` trait
2320 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2321 // check if the type after `as_ref` or `as_mut` is the same as before
2322 let recvr = &as_ref_args[0];
2323 let rcv_ty = cx.tables.expr_ty(recvr);
2324 let res_ty = cx.tables.expr_ty(expr);
2325 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2326 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2327 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2328 // allow the `as_ref` or `as_mut` if it is followed by another method call
2330 if let Some(parent) = get_parent_expr(cx, expr);
2331 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2332 if span != &expr.span;
2338 let mut applicability = Applicability::MachineApplicable;
2343 &format!("this call to `{}` does nothing", call_name),
2345 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2352 fn ty_has_iter_method(
2353 cx: &LateContext<'_, '_>,
2354 self_ref_ty: Ty<'_>,
2355 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2356 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2357 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2362 let mutbl = match self_ref_ty.sty {
2363 ty::Ref(_, _, mutbl) => mutbl,
2364 _ => unreachable!(),
2366 let method_name = match mutbl {
2367 hir::MutImmutable => "iter",
2368 hir::MutMutable => "iter_mut",
2370 Some((lint, ty_name, method_name))
2376 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2377 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2380 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2386 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2390 method_name.to_string(),
2391 Applicability::MachineApplicable,
2396 /// Given a `Result<T, E>` type, return its error type (`E`).
2397 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2398 if let ty::Adt(_, substs) = ty.sty {
2399 if match_type(cx, ty, &paths::RESULT) {
2400 substs.types().nth(1)
2409 /// This checks whether a given type is known to implement Debug.
2410 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2411 match cx.tcx.lang_items().debug_trait() {
2412 Some(debug) => implements_trait(cx, ty, debug, &[]),
2419 StartsWith(&'static str),
2423 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2424 (Convention::Eq("new"), &[SelfKind::No]),
2425 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2426 (Convention::StartsWith("from_"), &[SelfKind::No]),
2427 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2428 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2429 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2430 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2434 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2435 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2436 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2437 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2438 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2439 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2440 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2441 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2442 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2443 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2444 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2445 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2446 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2447 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2448 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2449 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2450 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2451 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2452 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2453 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2454 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2455 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2456 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2457 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2458 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2459 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2460 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2461 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2462 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2463 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2464 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2468 const PATTERN_METHODS: [(&str, usize); 17] = [
2476 ("split_terminator", 1),
2477 ("rsplit_terminator", 1),
2482 ("match_indices", 1),
2483 ("rmatch_indices", 1),
2484 ("trim_start_matches", 1),
2485 ("trim_end_matches", 1),
2488 #[derive(Clone, Copy, PartialEq, Debug)]
2499 cx: &LateContext<'_, '_>,
2503 allow_value_for_ref: bool,
2504 generics: &hir::Generics,
2506 // Self types in the HIR are desugared to explicit self types. So it will
2509 // where SomeType can be `Self` or an explicit impl self type (e.g., `Foo` if
2510 // the impl is on `Foo`)
2511 // Thus, we only need to test equality against the impl self type or if it is
2513 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
2514 // `Self`, `&mut Self`,
2515 // and `Box<Self>`, including the equivalent types with `Foo`.
2517 let is_actually_self = |ty| is_self_ty(ty) || SpanlessEq::new(cx).eq_ty(ty, self_ty);
2520 Self::Value => is_actually_self(ty),
2521 Self::Ref | Self::RefMut => {
2522 if allow_value_for_ref && is_actually_self(ty) {
2526 hir::TyKind::Rptr(_, ref mt_ty) => {
2527 let mutability_match = if self == Self::Ref {
2528 mt_ty.mutbl == hir::MutImmutable
2530 mt_ty.mutbl == hir::MutMutable
2532 is_actually_self(&mt_ty.ty) && mutability_match
2541 Self::Value => false,
2542 Self::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
2543 Self::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
2549 fn description(self) -> &'static str {
2551 Self::Value => "self by value",
2552 Self::Ref => "self by reference",
2553 Self::RefMut => "self by mutable reference",
2554 Self::No => "no self",
2559 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
2560 single_segment_ty(ty).map_or(false, |seg| {
2561 generics.params.iter().any(|param| match param.kind {
2562 hir::GenericParamKind::Type { .. } => {
2563 param.name.ident().name == seg.ident.name
2564 && param.bounds.iter().any(|bound| {
2565 if let hir::GenericBound::Trait(ref ptr, ..) = *bound {
2566 let path = &ptr.trait_ref.path;
2567 match_path(path, name)
2568 && path.segments.last().map_or(false, |s| {
2569 if let Some(ref params) = s.args {
2570 if params.parenthesized {
2573 // FIXME(flip1995): messy, improve if there is a better option
2575 let types: Vec<_> = params
2578 .filter_map(|arg| match arg {
2579 hir::GenericArg::Type(ty) => Some(ty),
2583 types.len() == 1 && (is_self_ty(&types[0]) || is_ty(&*types[0], self_ty))
2599 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
2600 match (&ty.node, &self_ty.node) {
2602 &hir::TyKind::Path(hir::QPath::Resolved(_, ref ty_path)),
2603 &hir::TyKind::Path(hir::QPath::Resolved(_, ref self_ty_path)),
2607 .map(|seg| seg.ident.name)
2608 .eq(self_ty_path.segments.iter().map(|seg| seg.ident.name)),
2613 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2614 if let hir::TyKind::Path(ref path) = ty.node {
2615 single_segment_path(path)
2622 fn check(&self, other: &str) -> bool {
2624 Self::Eq(this) => this == other,
2625 Self::StartsWith(this) => other.starts_with(this) && this != other,
2630 impl fmt::Display for Convention {
2631 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2633 Self::Eq(this) => this.fmt(f),
2634 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2639 #[derive(Clone, Copy)]
2648 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2649 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2651 (Self::Unit, &hir::DefaultReturn(_)) => true,
2652 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2653 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2654 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2655 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2661 fn is_bool(ty: &hir::Ty) -> bool {
2662 if let hir::TyKind::Path(ref p) = ty.node {
2663 match_qpath(p, &["bool"])