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 /// # let vec = vec![1];
251 /// vec.iter().filter(|x| **x == 0).next();
255 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
258 declare_clippy_lint! {
259 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
261 /// **Why is this bad?** Readability, this can be written more concisely as a
262 /// single method call.
264 /// **Known problems:**
268 /// iter.map(|x| x.iter()).flatten()
272 "using combinations of `flatten` and `map` which can usually be written as a single method call"
275 declare_clippy_lint! {
276 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
277 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
279 /// **Why is this bad?** Readability, this can be written more concisely as a
280 /// single method call.
282 /// **Known problems:** Often requires a condition + Option/Iterator creation
283 /// inside the closure.
287 /// iter.filter(|x| x == 0).map(|x| x * 2)
291 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
294 declare_clippy_lint! {
295 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
297 /// **Why is this bad?** Readability, this can be written more concisely as a
298 /// single method call.
300 /// **Known problems:** None
304 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
306 /// Can be written as
309 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
313 "using combination of `filter_map` and `next` which can usually be written as a single method call"
316 declare_clippy_lint! {
317 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
319 /// **Why is this bad?** Readability, this can be written more concisely as a
320 /// single method call.
322 /// **Known problems:** Often requires a condition + Option/Iterator creation
323 /// inside the closure.
327 /// (0..3).find(|x| x == 2).map(|x| x * 2);
329 /// Can be written as
331 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
335 "using a combination of `find` and `map` can usually be written as a single method call"
338 declare_clippy_lint! {
339 /// **What it does:** Checks for an iterator search (such as `find()`,
340 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
342 /// **Why is this bad?** Readability, this can be written more concisely as
345 /// **Known problems:** None.
349 /// # let vec = vec![1];
350 /// vec.iter().find(|x| **x == 0).is_some();
354 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
357 declare_clippy_lint! {
358 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
359 /// if it starts with a given char.
361 /// **Why is this bad?** Readability, this can be written more concisely as
362 /// `_.starts_with(_)`.
364 /// **Known problems:** None.
368 /// let name = "foo";
369 /// name.chars().next() == Some('_');
373 "using `.chars().next()` to check if a string starts with a char"
376 declare_clippy_lint! {
377 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
378 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
379 /// `unwrap_or_default` instead.
381 /// **Why is this bad?** The function will always be called and potentially
382 /// allocate an object acting as the default.
384 /// **Known problems:** If the function has side-effects, not calling it will
385 /// change the semantic of the program, but you shouldn't rely on that anyway.
389 /// # let foo = Some(String::new());
390 /// foo.unwrap_or(String::new());
392 /// this can instead be written:
394 /// # let foo = Some(String::new());
395 /// foo.unwrap_or_else(String::new);
399 /// # let foo = Some(String::new());
400 /// foo.unwrap_or_default();
404 "using any `*or` method with a function call, which suggests `*or_else`"
407 declare_clippy_lint! {
408 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
409 /// etc., and suggests to use `unwrap_or_else` instead
411 /// **Why is this bad?** The function will always be called.
413 /// **Known problems:** If the function has side-effects, not calling it will
414 /// change the semantics of the program, but you shouldn't rely on that anyway.
418 /// # let foo = Some(String::new());
419 /// # let err_code = "418";
420 /// # let err_msg = "I'm a teapot";
421 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
425 /// # let foo = Some(String::new());
426 /// # let err_code = "418";
427 /// # let err_msg = "I'm a teapot";
428 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
430 /// this can instead be written:
432 /// # let foo = Some(String::new());
433 /// # let err_code = "418";
434 /// # let err_msg = "I'm a teapot";
435 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
439 "using any `expect` method with a function call"
442 declare_clippy_lint! {
443 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
445 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
446 /// generics, not for using the `clone` method on a concrete type.
448 /// **Known problems:** None.
456 "using `clone` on a `Copy` type"
459 declare_clippy_lint! {
460 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
461 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
462 /// function syntax instead (e.g., `Rc::clone(foo)`).
464 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
465 /// can obscure the fact that only the pointer is being cloned, not the underlying
472 pub CLONE_ON_REF_PTR,
474 "using 'clone' on a ref-counted pointer"
477 declare_clippy_lint! {
478 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
480 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
481 /// cloning the underlying `T`.
483 /// **Known problems:** None.
490 /// let z = y.clone();
491 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
494 pub CLONE_DOUBLE_REF,
496 "using `clone` on `&&T`"
499 declare_clippy_lint! {
500 /// **What it does:** Checks for `new` not returning `Self`.
502 /// **Why is this bad?** As a convention, `new` methods are used to make a new
503 /// instance of a type.
505 /// **Known problems:** None.
510 /// fn new(..) -> NotAFoo {
516 "not returning `Self` in a `new` method"
519 declare_clippy_lint! {
520 /// **What it does:** Checks for string methods that receive a single-character
521 /// `str` as an argument, e.g., `_.split("x")`.
523 /// **Why is this bad?** Performing these methods using a `char` is faster than
526 /// **Known problems:** Does not catch multi-byte unicode characters.
529 /// `_.split("x")` could be `_.split('x')`
530 pub SINGLE_CHAR_PATTERN,
532 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
535 declare_clippy_lint! {
536 /// **What it does:** Checks for getting the inner pointer of a temporary
539 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
540 /// as the `CString` is alive.
542 /// **Known problems:** None.
546 /// let c_str = CString::new("foo").unwrap().as_ptr();
548 /// call_some_ffi_func(c_str);
551 /// Here `c_str` point to a freed address. The correct use would be:
553 /// let c_str = CString::new("foo").unwrap();
555 /// call_some_ffi_func(c_str.as_ptr());
558 pub TEMPORARY_CSTRING_AS_PTR,
560 "getting the inner pointer of a temporary `CString`"
563 declare_clippy_lint! {
564 /// **What it does:** Checks for use of `.iter().nth()` (and the related
565 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
567 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
570 /// **Known problems:** None.
574 /// let some_vec = vec![0, 1, 2, 3];
575 /// let bad_vec = some_vec.iter().nth(3);
576 /// let bad_slice = &some_vec[..].iter().nth(3);
578 /// The correct use would be:
580 /// let some_vec = vec![0, 1, 2, 3];
581 /// let bad_vec = some_vec.get(3);
582 /// let bad_slice = &some_vec[..].get(3);
586 "using `.iter().nth()` on a standard library type with O(1) element access"
589 declare_clippy_lint! {
590 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
592 /// **Why is this bad?** `.nth(x)` is cleaner
594 /// **Known problems:** None.
598 /// let some_vec = vec![0, 1, 2, 3];
599 /// let bad_vec = some_vec.iter().skip(3).next();
600 /// let bad_slice = &some_vec[..].iter().skip(3).next();
602 /// The correct use would be:
604 /// let some_vec = vec![0, 1, 2, 3];
605 /// let bad_vec = some_vec.iter().nth(3);
606 /// let bad_slice = &some_vec[..].iter().nth(3);
610 "using `.skip(x).next()` on an iterator"
613 declare_clippy_lint! {
614 /// **What it does:** Checks for use of `.get().unwrap()` (or
615 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
617 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
620 /// **Known problems:** Not a replacement for error handling: Using either
621 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
622 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
623 /// temporary placeholder for dealing with the `Option` type, then this does
624 /// not mitigate the need for error handling. If there is a chance that `.get()`
625 /// will be `None` in your program, then it is advisable that the `None` case
626 /// is handled in a future refactor instead of using `.unwrap()` or the Index
631 /// let mut some_vec = vec![0, 1, 2, 3];
632 /// let last = some_vec.get(3).unwrap();
633 /// *some_vec.get_mut(0).unwrap() = 1;
635 /// The correct use would be:
637 /// let mut some_vec = vec![0, 1, 2, 3];
638 /// let last = some_vec[3];
643 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
646 declare_clippy_lint! {
647 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
648 /// `&str` or `String`.
650 /// **Why is this bad?** `.push_str(s)` is clearer
652 /// **Known problems:** None.
657 /// let def = String::from("def");
658 /// let mut s = String::new();
659 /// s.extend(abc.chars());
660 /// s.extend(def.chars());
662 /// The correct use would be:
665 /// let def = String::from("def");
666 /// let mut s = String::new();
668 /// s.push_str(&def);
670 pub STRING_EXTEND_CHARS,
672 "using `x.extend(s.chars())` where s is a `&str` or `String`"
675 declare_clippy_lint! {
676 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
679 /// **Why is this bad?** `.to_vec()` is clearer
681 /// **Known problems:** None.
685 /// let s = [1, 2, 3, 4, 5];
686 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
688 /// The better use would be:
690 /// let s = [1, 2, 3, 4, 5];
691 /// let s2: Vec<isize> = s.to_vec();
693 pub ITER_CLONED_COLLECT,
695 "using `.cloned().collect()` on slice to create a `Vec`"
698 declare_clippy_lint! {
699 /// **What it does:** Checks for usage of `.chars().last()` or
700 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
702 /// **Why is this bad?** Readability, this can be written more concisely as
703 /// `_.ends_with(_)`.
705 /// **Known problems:** None.
709 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
713 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
716 declare_clippy_lint! {
717 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
718 /// types before and after the call are the same.
720 /// **Why is this bad?** The call is unnecessary.
722 /// **Known problems:** None.
726 /// # fn do_stuff(x: &[i32]) {}
727 /// let x: &[i32] = &[1, 2, 3, 4, 5];
728 /// do_stuff(x.as_ref());
730 /// The correct use would be:
732 /// # fn do_stuff(x: &[i32]) {}
733 /// let x: &[i32] = &[1, 2, 3, 4, 5];
738 "using `as_ref` where the types before and after the call are the same"
741 declare_clippy_lint! {
742 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
743 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
744 /// `sum` or `product`.
746 /// **Why is this bad?** Readability.
748 /// **Known problems:** False positive in pattern guards. Will be resolved once
749 /// non-lexical lifetimes are stable.
753 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
755 /// This could be written as:
757 /// let _ = (0..3).any(|x| x > 2);
759 pub UNNECESSARY_FOLD,
761 "using `fold` when a more succinct alternative exists"
764 declare_clippy_lint! {
765 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
766 /// More specifically it checks if the closure provided is only performing one of the
767 /// filter or map operations and suggests the appropriate option.
769 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
770 /// operation is being performed.
772 /// **Known problems:** None
776 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
778 /// As there is no transformation of the argument this could be written as:
780 /// let _ = (0..3).filter(|&x| x > 2);
784 /// let _ = (0..4).filter_map(i32::checked_abs);
786 /// As there is no conditional check on the argument this could be written as:
788 /// let _ = (0..4).map(i32::checked_abs);
790 pub UNNECESSARY_FILTER_MAP,
792 "using `filter_map` when a more succinct alternative exists"
795 declare_clippy_lint! {
796 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
799 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
800 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
801 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
802 /// like calling `iter` would. Furthermore, when the standard library actually
803 /// [implements the `into_iter` method](https://github.com/rust-lang/rust/issues/25725) which moves
804 /// the content out of the array, the original use of `into_iter` got inferred with the wrong type
805 /// and the code will be broken.
807 /// **Known problems:** None
812 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
814 pub INTO_ITER_ON_ARRAY,
816 "using `.into_iter()` on an array"
819 declare_clippy_lint! {
820 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
823 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
824 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
825 /// `iter_mut` directly.
827 /// **Known problems:** None
832 /// let _ = (&vec![3, 4, 5]).into_iter();
834 pub INTO_ITER_ON_REF,
836 "using `.into_iter()` on a reference"
839 declare_lint_pass!(Methods => [
842 SHOULD_IMPLEMENT_TRAIT,
843 WRONG_SELF_CONVENTION,
844 WRONG_PUB_SELF_CONVENTION,
846 OPTION_MAP_UNWRAP_OR,
847 OPTION_MAP_UNWRAP_OR_ELSE,
848 RESULT_MAP_UNWRAP_OR_ELSE,
860 TEMPORARY_CSTRING_AS_PTR,
873 UNNECESSARY_FILTER_MAP,
878 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
879 #[allow(clippy::cognitive_complexity)]
880 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
881 if in_macro(expr.span) {
885 let (method_names, arg_lists) = method_calls(expr, 2);
886 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
887 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
889 match method_names.as_slice() {
890 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
891 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
892 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
893 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
894 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0]),
895 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
896 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
897 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
898 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
899 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
900 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
901 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
902 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
903 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
904 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
905 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
906 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
907 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
908 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
909 ["as_ptr", "unwrap"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
910 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
911 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
912 ["next", "skip"] => lint_iter_skip_next(cx, expr),
913 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
914 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
915 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
916 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
917 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
922 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
923 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
924 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
926 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
927 if args.len() == 1 && method_call.ident.name == sym!(clone) {
928 lint_clone_on_copy(cx, expr, &args[0], self_ty);
929 lint_clone_on_ref_ptr(cx, expr, &args[0]);
933 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
934 for &(method, pos) in &PATTERN_METHODS {
935 if method_call.ident.name.as_str() == method && args.len() > pos {
936 lint_single_char_pattern(cx, expr, &args[pos]);
940 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
941 lint_into_iter(cx, expr, self_ty, *method_span);
946 hir::ExprKind::Binary(op, ref lhs, ref rhs)
947 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
949 let mut info = BinaryExprInfo {
953 eq: op.node == hir::BinOpKind::Eq,
955 lint_binary_expr_with_method_call(cx, &mut info);
961 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
962 if in_external_macro(cx.sess(), implitem.span) {
965 let name = implitem.ident.name.as_str();
966 let parent = cx.tcx.hir().get_parent_item(implitem.hir_id);
967 let item = cx.tcx.hir().expect_item(parent);
968 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
969 let ty = cx.tcx.type_of(def_id);
971 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
972 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
973 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
974 if let hir::ItemKind::Impl(_, _, _, _, None, ref self_ty, _) = item.node;
976 if cx.access_levels.is_exported(implitem.hir_id) {
977 // check missing trait implementations
978 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
979 if name == method_name &&
980 sig.decl.inputs.len() == n_args &&
981 out_type.matches(cx, &sig.decl.output) &&
982 self_kind.matches(cx, first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
983 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
984 "defining a method called `{}` on this type; consider implementing \
985 the `{}` trait or choosing a less ambiguous name", name, trait_name));
990 // check conventions w.r.t. conversion method names and predicates
991 let is_copy = is_copy(cx, ty);
992 for &(ref conv, self_kinds) in &CONVENTIONS {
993 if conv.check(&name) {
996 .any(|k| k.matches(cx, first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics)) {
997 let lint = if item.vis.node.is_pub() {
998 WRONG_PUB_SELF_CONVENTION
1000 WRONG_SELF_CONVENTION
1005 &format!("methods called `{}` usually take {}; consider choosing a less \
1009 .map(|k| k.description())
1010 .collect::<Vec<_>>()
1014 // Only check the first convention to match (CONVENTIONS should be listed from most to least
1022 if let hir::ImplItemKind::Method(_, _) = implitem.node {
1023 let ret_ty = return_ty(cx, implitem.hir_id);
1025 // walk the return type and check for Self (this does not check associated types)
1026 for inner_type in ret_ty.walk() {
1027 if same_tys(cx, ty, inner_type) {
1032 // if return type is impl trait, check the associated types
1033 if let ty::Opaque(def_id, _) = ret_ty.sty {
1034 // one of the associated types must be Self
1035 for predicate in &cx.tcx.predicates_of(def_id).predicates {
1037 (Predicate::Projection(poly_projection_predicate), _) => {
1038 let binder = poly_projection_predicate.ty();
1039 let associated_type = binder.skip_binder();
1040 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
1042 // if the associated type is self, early return and do not trigger lint
1043 if associated_type_is_self_type {
1052 if name == "new" && !same_tys(cx, ret_ty, ty) {
1057 "methods called `new` usually return `Self`",
1064 /// Checks for the `OR_FUN_CALL` lint.
1065 #[allow(clippy::too_many_lines)]
1066 fn lint_or_fun_call<'a, 'tcx>(
1067 cx: &LateContext<'a, 'tcx>,
1071 args: &'tcx [hir::Expr],
1073 // Searches an expression for method calls or function calls that aren't ctors
1074 struct FunCallFinder<'a, 'tcx> {
1075 cx: &'a LateContext<'a, 'tcx>,
1079 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1080 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
1081 let call_found = match &expr.node {
1082 // ignore enum and struct constructors
1083 hir::ExprKind::Call(..) => !is_ctor_function(self.cx, expr),
1084 hir::ExprKind::MethodCall(..) => true,
1089 // don't lint for constant values
1090 let owner_def = self.cx.tcx.hir().get_parent_did(expr.hir_id);
1091 let promotable = self
1094 .rvalue_promotable_map(owner_def)
1095 .contains(&expr.hir_id.local_id);
1102 intravisit::walk_expr(self, expr);
1106 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1107 intravisit::NestedVisitorMap::None
1111 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1112 fn check_unwrap_or_default(
1113 cx: &LateContext<'_, '_>,
1116 self_expr: &hir::Expr,
1125 if name == "unwrap_or" {
1126 if let hir::ExprKind::Path(ref qpath) = fun.node {
1127 let path = &*last_path_segment(qpath).ident.as_str();
1129 if ["default", "new"].contains(&path) {
1130 let arg_ty = cx.tables.expr_ty(arg);
1131 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1137 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1138 let mut applicability = Applicability::MachineApplicable;
1143 &format!("use of `{}` followed by a call to `{}`", name, path),
1146 "{}.unwrap_or_default()",
1147 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1160 /// Checks for `*or(foo())`.
1161 #[allow(clippy::too_many_arguments)]
1162 fn check_general_case<'a, 'tcx>(
1163 cx: &LateContext<'a, 'tcx>,
1167 self_expr: &hir::Expr,
1168 arg: &'tcx hir::Expr,
1172 // (path, fn_has_argument, methods, suffix)
1173 let know_types: &[(&[_], _, &[_], _)] = &[
1174 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1175 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1176 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1177 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1180 // early check if the name is one we care about
1181 if know_types.iter().all(|k| !k.2.contains(&name)) {
1185 let mut finder = FunCallFinder { cx: &cx, found: false };
1186 finder.visit_expr(&arg);
1191 let self_ty = cx.tables.expr_ty(self_expr);
1193 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1194 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1196 (fn_has_arguments, poss, suffix)
1201 if !poss.contains(&name) {
1205 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1206 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1207 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1208 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1210 let span_replace_word = method_span.with_hi(span.hi());
1215 &format!("use of `{}` followed by a function call", name),
1217 format!("{}_{}({})", name, suffix, sugg),
1218 Applicability::HasPlaceholders,
1222 if args.len() == 2 {
1223 match args[1].node {
1224 hir::ExprKind::Call(ref fun, ref or_args) => {
1225 let or_has_args = !or_args.is_empty();
1226 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1239 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1246 !or_args.is_empty(),
1254 /// Checks for the `EXPECT_FUN_CALL` lint.
1255 #[allow(clippy::too_many_lines)]
1256 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1257 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1259 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1260 let mut arg_root = arg;
1262 arg_root = match &arg_root.node {
1263 hir::ExprKind::AddrOf(_, expr) => expr,
1264 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1265 if call_args.len() == 1
1266 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1268 let arg_type = cx.tables.expr_ty(&call_args[0]);
1269 let base_type = walk_ptrs_ty(arg_type);
1270 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1284 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1285 // converted to string.
1286 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1287 let arg_ty = cx.tables.expr_ty(arg);
1288 if match_type(cx, arg_ty, &paths::STRING) {
1291 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1292 if ty.sty == ty::Str {
1299 fn generate_format_arg_snippet(
1300 cx: &LateContext<'_, '_>,
1302 applicability: &mut Applicability,
1304 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1305 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1306 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1307 return format_arg_expr_tup
1309 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1318 fn is_call(node: &hir::ExprKind) -> bool {
1320 hir::ExprKind::AddrOf(_, expr) => {
1323 hir::ExprKind::Call(..)
1324 | hir::ExprKind::MethodCall(..)
1325 // These variants are debatable or require further examination
1326 | hir::ExprKind::Match(..)
1327 | hir::ExprKind::Block{ .. } => true,
1332 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1336 let receiver_type = cx.tables.expr_ty(&args[0]);
1337 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1339 } else if match_type(cx, receiver_type, &paths::RESULT) {
1345 let arg_root = get_arg_root(cx, &args[1]);
1347 let span_replace_word = method_span.with_hi(expr.span.hi());
1349 let mut applicability = Applicability::MachineApplicable;
1351 //Special handling for `format!` as arg_root
1352 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1353 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1354 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1355 let fmt_spec = &format_args[0];
1356 let fmt_args = &format_args[1];
1358 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1360 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1362 let sugg = args.join(", ");
1368 &format!("use of `{}` followed by a function call", name),
1370 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1379 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1380 if requires_to_string(cx, arg_root) {
1381 arg_root_snippet.to_mut().push_str(".to_string()");
1388 &format!("use of `{}` followed by a function call", name),
1390 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1395 /// Checks for the `CLONE_ON_COPY` lint.
1396 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1397 let ty = cx.tables.expr_ty(expr);
1398 if let ty::Ref(_, inner, _) = arg_ty.sty {
1399 if let ty::Ref(_, innermost, _) = inner.sty {
1404 "using `clone` on a double-reference; \
1405 this will copy the reference instead of cloning the inner type",
1407 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1408 let mut ty = innermost;
1410 while let ty::Ref(_, inner, _) = ty.sty {
1414 let refs: String = iter::repeat('&').take(n + 1).collect();
1415 let derefs: String = iter::repeat('*').take(n).collect();
1416 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1419 "try dereferencing it",
1420 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1421 Applicability::MaybeIncorrect,
1425 "or try being explicit about what type to clone",
1427 Applicability::MaybeIncorrect,
1432 return; // don't report clone_on_copy
1436 if is_copy(cx, ty) {
1438 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1439 // x.clone() might have dereferenced x, possibly through Deref impls
1440 if cx.tables.expr_ty(arg) == ty {
1441 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1443 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
1444 match cx.tcx.hir().get(parent) {
1445 hir::Node::Expr(parent) => match parent.node {
1446 // &*x is a nop, &x.clone() is not
1447 hir::ExprKind::AddrOf(..) |
1448 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1449 hir::ExprKind::MethodCall(..) => return,
1452 hir::Node::Stmt(stmt) => {
1453 if let hir::StmtKind::Local(ref loc) = stmt.node {
1454 if let hir::PatKind::Ref(..) = loc.pat.node {
1455 // let ref y = *x borrows x, let ref y = x.clone() does not
1463 let deref_count = cx
1465 .expr_adjustments(arg)
1468 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1475 let derefs: String = iter::repeat('*').take(deref_count).collect();
1476 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1481 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1482 if let Some((text, snip)) = snip {
1483 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1489 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1490 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1492 if let ty::Adt(_, subst) = obj_ty.sty {
1493 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1495 } else if match_type(cx, obj_ty, &paths::ARC) {
1497 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1507 "using '.clone()' on a ref-counted pointer",
1510 "{}::<{}>::clone(&{})",
1513 snippet(cx, arg.span, "_")
1515 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1520 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1522 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1523 let target = &arglists[0][0];
1524 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1525 let ref_str = if self_ty.sty == ty::Str {
1527 } else if match_type(cx, self_ty, &paths::STRING) {
1533 let mut applicability = Applicability::MachineApplicable;
1536 STRING_EXTEND_CHARS,
1538 "calling `.extend(_.chars())`",
1541 "{}.push_str({}{})",
1542 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1544 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1551 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1552 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1553 if match_type(cx, obj_ty, &paths::STRING) {
1554 lint_string_extend(cx, expr, args);
1558 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1560 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1562 if let hir::ExprKind::Path(ref path) = fun.node;
1563 if let Res::Def(DefKind::Method, did) = cx.tables.qpath_res(path, fun.hir_id);
1564 if match_def_path(cx, did, &paths::CSTRING_NEW);
1568 TEMPORARY_CSTRING_AS_PTR,
1570 "you are getting the inner pointer of a temporary `CString`",
1572 db.note("that pointer will be invalid outside this expression");
1573 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1579 fn lint_iter_cloned_collect<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr]) {
1580 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC) {
1581 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])) {
1582 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite()) {
1585 ITER_CLONED_COLLECT,
1587 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1590 ".to_vec()".to_string(),
1591 Applicability::MachineApplicable,
1598 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1599 fn check_fold_with_op(
1600 cx: &LateContext<'_, '_>,
1601 fold_args: &[hir::Expr],
1603 replacement_method_name: &str,
1604 replacement_has_args: bool,
1607 // Extract the body of the closure passed to fold
1608 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1609 let closure_body = cx.tcx.hir().body(body_id);
1610 let closure_expr = remove_blocks(&closure_body.value);
1612 // Check if the closure body is of the form `acc <op> some_expr(x)`
1613 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1614 if bin_op.node == op;
1616 // Extract the names of the two arguments to the closure
1617 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1618 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1620 if match_var(&*left_expr, first_arg_ident);
1621 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1624 // Span containing `.fold(...)`
1625 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1626 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1628 let mut applicability = Applicability::MachineApplicable;
1629 let sugg = if replacement_has_args {
1631 ".{replacement}(|{s}| {r})",
1632 replacement = replacement_method_name,
1633 s = second_arg_ident,
1634 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1639 replacement = replacement_method_name,
1647 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
1648 "this `.fold` can be written more succinctly using another method",
1657 // Check that this is a call to Iterator::fold rather than just some function called fold
1658 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1663 fold_args.len() == 3,
1664 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1667 // Check if the first argument to .fold is a suitable literal
1668 if let hir::ExprKind::Lit(ref lit) = fold_args[1].node {
1670 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1671 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1672 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1673 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1679 fn lint_iter_nth<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, iter_args: &'tcx [hir::Expr], is_mut: bool) {
1680 let mut_str = if is_mut { "_mut" } else { "" };
1681 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1683 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1685 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1688 return; // caller is not a type that we want to lint
1696 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1697 mut_str, caller_type
1702 fn lint_get_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr, get_args: &'tcx [hir::Expr], is_mut: bool) {
1703 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1704 // because they do not implement `IndexMut`
1705 let mut applicability = Applicability::MachineApplicable;
1706 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1707 let get_args_str = if get_args.len() > 1 {
1708 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1710 return; // not linting on a .get().unwrap() chain or variant
1713 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1714 needs_ref = get_args_str.parse::<usize>().is_ok();
1716 } else if match_type(cx, expr_ty, &paths::VEC) {
1717 needs_ref = get_args_str.parse::<usize>().is_ok();
1719 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1720 needs_ref = get_args_str.parse::<usize>().is_ok();
1722 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1725 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1729 return; // caller is not a type that we want to lint
1732 let mut span = expr.span;
1734 // Handle the case where the result is immediately dereferenced
1735 // by not requiring ref and pulling the dereference into the
1739 if let Some(parent) = get_parent_expr(cx, expr);
1740 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1747 let mut_str = if is_mut { "_mut" } else { "" };
1748 let borrow_str = if !needs_ref {
1761 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1762 mut_str, caller_type
1768 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1775 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1776 // lint if caller of skip is an Iterator
1777 if match_trait_method(cx, expr, &paths::ITERATOR) {
1782 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1787 fn derefs_to_slice<'a, 'tcx>(
1788 cx: &LateContext<'a, 'tcx>,
1789 expr: &'tcx hir::Expr,
1791 ) -> Option<&'tcx hir::Expr> {
1792 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
1794 ty::Slice(_) => true,
1795 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1796 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1797 ty::Array(_, size) => size.assert_usize(cx.tcx).expect("array length") < 32,
1798 ty::Ref(_, inner, _) => may_slice(cx, inner),
1803 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1804 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1811 ty::Slice(_) => Some(expr),
1812 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
1813 ty::Ref(_, inner, _) => {
1814 if may_slice(cx, inner) {
1825 /// lint use of `unwrap()` for `Option`s and `Result`s
1826 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1827 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1829 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1830 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1831 } else if match_type(cx, obj_ty, &paths::RESULT) {
1832 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1837 if let Some((lint, kind, none_value)) = mess {
1843 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1844 using expect() to provide a better panic \
1852 /// lint use of `ok().expect()` for `Result`s
1853 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1854 // lint if the caller of `ok()` is a `Result`
1855 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1856 let result_type = cx.tables.expr_ty(&ok_args[0]);
1857 if let Some(error_type) = get_error_type(cx, result_type) {
1858 if has_debug_impl(error_type, cx) {
1863 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1870 /// lint use of `map().flatten()` for `Iterators`
1871 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1872 // lint if caller of `.map().flatten()` is an Iterator
1873 if match_trait_method(cx, expr, &paths::ITERATOR) {
1874 let msg = "called `map(..).flatten()` on an `Iterator`. \
1875 This is more succinctly expressed by calling `.flat_map(..)`";
1876 let self_snippet = snippet(cx, map_args[0].span, "..");
1877 let func_snippet = snippet(cx, map_args[1].span, "..");
1878 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1879 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1882 "try using flat_map instead",
1884 Applicability::MachineApplicable,
1890 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1891 fn lint_map_unwrap_or_else<'a, 'tcx>(
1892 cx: &LateContext<'a, 'tcx>,
1893 expr: &'tcx hir::Expr,
1894 map_args: &'tcx [hir::Expr],
1895 unwrap_args: &'tcx [hir::Expr],
1897 // lint if the caller of `map()` is an `Option`
1898 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1899 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1901 if is_option || is_result {
1902 // Don't make a suggestion that may fail to compile due to mutably borrowing
1903 // the same variable twice.
1904 let map_mutated_vars = mutated_variables(&map_args[0], cx);
1905 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
1906 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
1907 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
1915 let msg = if is_option {
1916 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1917 `map_or_else(g, f)` instead"
1919 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1920 `ok().map_or_else(g, f)` instead"
1922 // get snippets for args to map() and unwrap_or_else()
1923 let map_snippet = snippet(cx, map_args[1].span, "..");
1924 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1925 // lint, with note if neither arg is > 1 line and both map() and
1926 // unwrap_or_else() have the same span
1927 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1928 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1929 if same_span && !multiline {
1933 OPTION_MAP_UNWRAP_OR_ELSE
1935 RESULT_MAP_UNWRAP_OR_ELSE
1941 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1944 if is_result { "ok()." } else { "" }
1947 } else if same_span && multiline {
1951 OPTION_MAP_UNWRAP_OR_ELSE
1953 RESULT_MAP_UNWRAP_OR_ELSE
1962 /// lint use of `_.map_or(None, _)` for `Option`s
1963 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
1964 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
1965 // check if the first non-self argument to map_or() is None
1966 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
1967 match_qpath(qpath, &paths::OPTION_NONE)
1972 if map_or_arg_is_none {
1974 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
1975 `and_then(f)` instead";
1976 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
1977 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
1978 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
1979 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
1982 "try using and_then instead",
1984 Applicability::MachineApplicable, // snippet
1991 /// lint use of `filter().next()` for `Iterators`
1992 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
1993 // lint if caller of `.filter().next()` is an Iterator
1994 if match_trait_method(cx, expr, &paths::ITERATOR) {
1995 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
1996 `.find(p)` instead.";
1997 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1998 if filter_snippet.lines().count() <= 1 {
1999 // add note if not multi-line
2006 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2009 span_lint(cx, FILTER_NEXT, expr.span, msg);
2014 /// lint use of `filter().map()` for `Iterators`
2015 fn lint_filter_map<'a, 'tcx>(
2016 cx: &LateContext<'a, 'tcx>,
2017 expr: &'tcx hir::Expr,
2018 _filter_args: &'tcx [hir::Expr],
2019 _map_args: &'tcx [hir::Expr],
2021 // lint if caller of `.filter().map()` is an Iterator
2022 if match_trait_method(cx, expr, &paths::ITERATOR) {
2023 let msg = "called `filter(p).map(q)` on an `Iterator`. \
2024 This is more succinctly expressed by calling `.filter_map(..)` instead.";
2025 span_lint(cx, FILTER_MAP, expr.span, msg);
2029 /// lint use of `filter_map().next()` for `Iterators`
2030 fn lint_filter_map_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
2031 if match_trait_method(cx, expr, &paths::ITERATOR) {
2032 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2033 `.find_map(p)` instead.";
2034 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2035 if filter_snippet.lines().count() <= 1 {
2042 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2045 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2050 /// lint use of `find().map()` for `Iterators`
2051 fn lint_find_map<'a, 'tcx>(
2052 cx: &LateContext<'a, 'tcx>,
2053 expr: &'tcx hir::Expr,
2054 _find_args: &'tcx [hir::Expr],
2055 map_args: &'tcx [hir::Expr],
2057 // lint if caller of `.filter().map()` is an Iterator
2058 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2059 let msg = "called `find(p).map(q)` on an `Iterator`. \
2060 This is more succinctly expressed by calling `.find_map(..)` instead.";
2061 span_lint(cx, FIND_MAP, expr.span, msg);
2065 /// lint use of `filter().map()` for `Iterators`
2066 fn lint_filter_map_map<'a, 'tcx>(
2067 cx: &LateContext<'a, 'tcx>,
2068 expr: &'tcx hir::Expr,
2069 _filter_args: &'tcx [hir::Expr],
2070 _map_args: &'tcx [hir::Expr],
2072 // lint if caller of `.filter().map()` is an Iterator
2073 if match_trait_method(cx, expr, &paths::ITERATOR) {
2074 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
2075 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
2076 span_lint(cx, FILTER_MAP, expr.span, msg);
2080 /// lint use of `filter().flat_map()` for `Iterators`
2081 fn lint_filter_flat_map<'a, 'tcx>(
2082 cx: &LateContext<'a, 'tcx>,
2083 expr: &'tcx hir::Expr,
2084 _filter_args: &'tcx [hir::Expr],
2085 _map_args: &'tcx [hir::Expr],
2087 // lint if caller of `.filter().flat_map()` is an Iterator
2088 if match_trait_method(cx, expr, &paths::ITERATOR) {
2089 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
2090 This is more succinctly expressed by calling `.flat_map(..)` \
2091 and filtering by returning an empty Iterator.";
2092 span_lint(cx, FILTER_MAP, expr.span, msg);
2096 /// lint use of `filter_map().flat_map()` for `Iterators`
2097 fn lint_filter_map_flat_map<'a, 'tcx>(
2098 cx: &LateContext<'a, 'tcx>,
2099 expr: &'tcx hir::Expr,
2100 _filter_args: &'tcx [hir::Expr],
2101 _map_args: &'tcx [hir::Expr],
2103 // lint if caller of `.filter_map().flat_map()` is an Iterator
2104 if match_trait_method(cx, expr, &paths::ITERATOR) {
2105 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
2106 This is more succinctly expressed by calling `.flat_map(..)` \
2107 and filtering by returning an empty Iterator.";
2108 span_lint(cx, FILTER_MAP, expr.span, msg);
2112 /// lint searching an Iterator followed by `is_some()`
2113 fn lint_search_is_some<'a, 'tcx>(
2114 cx: &LateContext<'a, 'tcx>,
2115 expr: &'tcx hir::Expr,
2116 search_method: &str,
2117 search_args: &'tcx [hir::Expr],
2118 is_some_args: &'tcx [hir::Expr],
2120 // lint if caller of search is an Iterator
2121 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2123 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2124 expressed by calling `any()`.",
2127 let search_snippet = snippet(cx, search_args[1].span, "..");
2128 if search_snippet.lines().count() <= 1 {
2129 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2130 let any_search_snippet = if_chain! {
2131 if search_method == "find";
2132 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].node;
2133 let closure_body = cx.tcx.hir().body(body_id);
2134 if let Some(closure_arg) = closure_body.arguments.get(0);
2135 if let hir::PatKind::Ref(..) = closure_arg.pat.node;
2137 Some(search_snippet.replacen('&', "", 1))
2142 // add note if not multi-line
2150 "replace `{0}({1}).is_some()` with `any({2})`",
2153 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2157 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2162 /// Used for `lint_binary_expr_with_method_call`.
2163 #[derive(Copy, Clone)]
2164 struct BinaryExprInfo<'a> {
2165 expr: &'a hir::Expr,
2166 chain: &'a hir::Expr,
2167 other: &'a hir::Expr,
2171 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2172 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2173 macro_rules! lint_with_both_lhs_and_rhs {
2174 ($func:ident, $cx:expr, $info:ident) => {
2175 if !$func($cx, $info) {
2176 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2177 if $func($cx, $info) {
2184 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2185 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2186 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2187 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2190 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2192 cx: &LateContext<'_, '_>,
2193 info: &BinaryExprInfo<'_>,
2194 chain_methods: &[&str],
2195 lint: &'static Lint,
2199 if let Some(args) = method_chain_args(info.chain, chain_methods);
2200 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2201 if arg_char.len() == 1;
2202 if let hir::ExprKind::Path(ref qpath) = fun.node;
2203 if let Some(segment) = single_segment_path(qpath);
2204 if segment.ident.name == sym!(Some);
2206 let mut applicability = Applicability::MachineApplicable;
2207 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2209 if self_ty.sty != ty::Str {
2217 &format!("you should use the `{}` method", suggest),
2219 format!("{}{}.{}({})",
2220 if info.eq { "" } else { "!" },
2221 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2223 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2234 /// Checks for the `CHARS_NEXT_CMP` lint.
2235 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2236 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2239 /// Checks for the `CHARS_LAST_CMP` lint.
2240 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2241 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2244 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2248 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2249 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2250 cx: &LateContext<'a, 'tcx>,
2251 info: &BinaryExprInfo<'_>,
2252 chain_methods: &[&str],
2253 lint: &'static Lint,
2257 if let Some(args) = method_chain_args(info.chain, chain_methods);
2258 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2259 if let ast::LitKind::Char(c) = lit.node;
2261 let mut applicability = Applicability::MachineApplicable;
2266 &format!("you should use the `{}` method", suggest),
2268 format!("{}{}.{}('{}')",
2269 if info.eq { "" } else { "!" },
2270 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2283 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2284 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2285 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2288 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2289 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2290 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2293 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2297 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2298 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2300 if let hir::ExprKind::Lit(lit) = &arg.node;
2301 if let ast::LitKind::Str(r, _) = lit.node;
2302 if r.as_str().len() == 1;
2304 let mut applicability = Applicability::MachineApplicable;
2305 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2306 let c = &snip[1..snip.len() - 1];
2307 let hint = format!("'{}'", if c == "'" { "\\'" } else { c });
2310 SINGLE_CHAR_PATTERN,
2312 "single-character string constant used as pattern",
2313 "try using a char instead",
2321 /// Checks for the `USELESS_ASREF` lint.
2322 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2323 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2324 // check if the call is to the actual `AsRef` or `AsMut` trait
2325 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2326 // check if the type after `as_ref` or `as_mut` is the same as before
2327 let recvr = &as_ref_args[0];
2328 let rcv_ty = cx.tables.expr_ty(recvr);
2329 let res_ty = cx.tables.expr_ty(expr);
2330 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2331 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2332 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2333 // allow the `as_ref` or `as_mut` if it is followed by another method call
2335 if let Some(parent) = get_parent_expr(cx, expr);
2336 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2337 if span != &expr.span;
2343 let mut applicability = Applicability::MachineApplicable;
2348 &format!("this call to `{}` does nothing", call_name),
2350 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2357 fn ty_has_iter_method(
2358 cx: &LateContext<'_, '_>,
2359 self_ref_ty: Ty<'_>,
2360 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2361 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2362 let lint = if ty_name == "array" || ty_name == "PathBuf" {
2367 let mutbl = match self_ref_ty.sty {
2368 ty::Ref(_, _, mutbl) => mutbl,
2369 _ => unreachable!(),
2371 let method_name = match mutbl {
2372 hir::MutImmutable => "iter",
2373 hir::MutMutable => "iter_mut",
2375 Some((lint, ty_name, method_name))
2381 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: Ty<'_>, method_span: Span) {
2382 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2385 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2391 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2395 method_name.to_string(),
2396 Applicability::MachineApplicable,
2401 /// Given a `Result<T, E>` type, return its error type (`E`).
2402 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2403 if let ty::Adt(_, substs) = ty.sty {
2404 if match_type(cx, ty, &paths::RESULT) {
2405 substs.types().nth(1)
2414 /// This checks whether a given type is known to implement Debug.
2415 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2416 match cx.tcx.lang_items().debug_trait() {
2417 Some(debug) => implements_trait(cx, ty, debug, &[]),
2424 StartsWith(&'static str),
2428 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2429 (Convention::Eq("new"), &[SelfKind::No]),
2430 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2431 (Convention::StartsWith("from_"), &[SelfKind::No]),
2432 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2433 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2434 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2435 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2439 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2440 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2441 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2442 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2443 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2444 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2445 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2446 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2447 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2448 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2449 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2450 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2451 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2452 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2453 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2454 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2455 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2456 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2457 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2458 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2459 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2460 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2461 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2462 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2463 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2464 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2465 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2466 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2467 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2468 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2469 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2473 const PATTERN_METHODS: [(&str, usize); 17] = [
2481 ("split_terminator", 1),
2482 ("rsplit_terminator", 1),
2487 ("match_indices", 1),
2488 ("rmatch_indices", 1),
2489 ("trim_start_matches", 1),
2490 ("trim_end_matches", 1),
2493 #[derive(Clone, Copy, PartialEq, Debug)]
2504 cx: &LateContext<'_, '_>,
2508 allow_value_for_ref: bool,
2509 generics: &hir::Generics,
2511 // Self types in the HIR are desugared to explicit self types. So it will
2514 // where SomeType can be `Self` or an explicit impl self type (e.g., `Foo` if
2515 // the impl is on `Foo`)
2516 // Thus, we only need to test equality against the impl self type or if it is
2518 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
2519 // `Self`, `&mut Self`,
2520 // and `Box<Self>`, including the equivalent types with `Foo`.
2522 let is_actually_self = |ty| is_self_ty(ty) || SpanlessEq::new(cx).eq_ty(ty, self_ty);
2525 Self::Value => is_actually_self(ty),
2526 Self::Ref | Self::RefMut => {
2527 if allow_value_for_ref && is_actually_self(ty) {
2531 hir::TyKind::Rptr(_, ref mt_ty) => {
2532 let mutability_match = if self == Self::Ref {
2533 mt_ty.mutbl == hir::MutImmutable
2535 mt_ty.mutbl == hir::MutMutable
2537 is_actually_self(&mt_ty.ty) && mutability_match
2546 Self::Value => false,
2547 Self::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
2548 Self::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
2554 fn description(self) -> &'static str {
2556 Self::Value => "self by value",
2557 Self::Ref => "self by reference",
2558 Self::RefMut => "self by mutable reference",
2559 Self::No => "no self",
2564 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
2565 single_segment_ty(ty).map_or(false, |seg| {
2566 generics.params.iter().any(|param| match param.kind {
2567 hir::GenericParamKind::Type { .. } => {
2568 param.name.ident().name == seg.ident.name
2569 && param.bounds.iter().any(|bound| {
2570 if let hir::GenericBound::Trait(ref ptr, ..) = *bound {
2571 let path = &ptr.trait_ref.path;
2572 match_path(path, name)
2573 && path.segments.last().map_or(false, |s| {
2574 if let Some(ref params) = s.args {
2575 if params.parenthesized {
2578 // FIXME(flip1995): messy, improve if there is a better option
2580 let types: Vec<_> = params
2583 .filter_map(|arg| match arg {
2584 hir::GenericArg::Type(ty) => Some(ty),
2588 types.len() == 1 && (is_self_ty(&types[0]) || is_ty(&*types[0], self_ty))
2604 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
2605 match (&ty.node, &self_ty.node) {
2607 &hir::TyKind::Path(hir::QPath::Resolved(_, ref ty_path)),
2608 &hir::TyKind::Path(hir::QPath::Resolved(_, ref self_ty_path)),
2612 .map(|seg| seg.ident.name)
2613 .eq(self_ty_path.segments.iter().map(|seg| seg.ident.name)),
2618 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2619 if let hir::TyKind::Path(ref path) = ty.node {
2620 single_segment_path(path)
2627 fn check(&self, other: &str) -> bool {
2629 Self::Eq(this) => this == other,
2630 Self::StartsWith(this) => other.starts_with(this) && this != other,
2635 impl fmt::Display for Convention {
2636 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2638 Self::Eq(this) => this.fmt(f),
2639 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2644 #[derive(Clone, Copy)]
2653 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2654 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2656 (Self::Unit, &hir::DefaultReturn(_)) => true,
2657 (Self::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2658 (Self::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2659 (Self::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2660 (Self::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2666 fn is_bool(ty: &hir::Ty) -> bool {
2667 if let hir::TyKind::Path(ref p) = ty.node {
2668 match_qpath(p, &["bool"])