1 use crate::utils::paths;
2 use crate::utils::sugg;
4 get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy, is_expn_of, is_self,
5 is_self_ty, iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method,
6 match_type, match_var, method_calls, method_chain_args, remove_blocks, return_ty, same_tys, single_segment_path,
7 snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_sugg,
8 span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
10 use if_chain::if_chain;
13 use rustc::hir::def::Def;
14 use rustc::lint::{in_external_macro, LateContext, LateLintPass, Lint, LintArray, LintContext, LintPass};
15 use rustc::ty::{self, Predicate, Ty};
16 use rustc::{declare_tool_lint, lint_array};
17 use rustc_errors::Applicability;
22 use syntax::source_map::{BytePos, Span};
23 use syntax::symbol::LocalInternedString;
25 mod unnecessary_filter_map;
30 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
32 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
33 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
34 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
35 /// `Allow` by default.
37 /// **Known problems:** None.
43 declare_clippy_lint! {
44 pub OPTION_UNWRAP_USED,
46 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
49 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
51 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
52 /// values. Normally, you want to implement more sophisticated error handling,
53 /// and propagate errors upwards with `try!`.
55 /// Even if you want to panic on errors, not all `Error`s implement good
56 /// messages on display. Therefore it may be beneficial to look at the places
57 /// where they may get displayed. Activate this lint to do just that.
59 /// **Known problems:** None.
65 declare_clippy_lint! {
66 pub RESULT_UNWRAP_USED,
68 "using `Result.unwrap()`, which might be better handled"
71 /// **What it does:** Checks for methods that should live in a trait
72 /// implementation of a `std` trait (see [llogiq's blog
73 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
74 /// information) instead of an inherent implementation.
76 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
77 /// the code, often with very little cost. Also people seeing a `mul(...)`
79 /// may expect `*` to work equally, so you should have good reason to disappoint
82 /// **Known problems:** None.
88 /// fn add(&self, other: &X) -> X {
93 declare_clippy_lint! {
94 pub SHOULD_IMPLEMENT_TRAIT,
96 "defining a method that should be implementing a std trait"
99 /// **What it does:** Checks for methods with certain name prefixes and which
100 /// doesn't match how self is taken. The actual rules are:
102 /// |Prefix |`self` taken |
103 /// |-------|----------------------|
104 /// |`as_` |`&self` or `&mut self`|
106 /// |`into_`|`self` |
107 /// |`is_` |`&self` or none |
108 /// |`to_` |`&self` |
110 /// **Why is this bad?** Consistency breeds readability. If you follow the
111 /// conventions, your users won't be surprised that they, e.g., need to supply a
112 /// mutable reference to a `as_..` function.
114 /// **Known problems:** None.
119 /// fn as_str(self) -> &str {
124 declare_clippy_lint! {
125 pub WRONG_SELF_CONVENTION,
127 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
130 /// **What it does:** This is the same as
131 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
133 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
135 /// **Known problems:** Actually *renaming* the function may break clients if
136 /// the function is part of the public interface. In that case, be mindful of
137 /// the stability guarantees you've given your users.
142 /// pub fn as_str(self) -> &str {
147 declare_clippy_lint! {
148 pub WRONG_PUB_SELF_CONVENTION,
150 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
153 /// **What it does:** Checks for usage of `ok().expect(..)`.
155 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
156 /// directly to get a better error message.
158 /// **Known problems:** The error type needs to implement `Debug`
162 /// x.ok().expect("why did I do this again?")
164 declare_clippy_lint! {
167 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
170 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
172 /// **Why is this bad?** Readability, this can be written more concisely as
173 /// `_.map_or(_, _)`.
175 /// **Known problems:** The order of the arguments is not in execution order
179 /// x.map(|a| a + 1).unwrap_or(0)
181 declare_clippy_lint! {
182 pub OPTION_MAP_UNWRAP_OR,
184 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
188 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
190 /// **Why is this bad?** Readability, this can be written more concisely as
191 /// `_.map_or_else(_, _)`.
193 /// **Known problems:** The order of the arguments is not in execution order.
197 /// x.map(|a| a + 1).unwrap_or_else(some_function)
199 declare_clippy_lint! {
200 pub OPTION_MAP_UNWRAP_OR_ELSE,
202 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`"
205 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
207 /// **Why is this bad?** Readability, this can be written more concisely as
208 /// `result.ok().map_or_else(_, _)`.
210 /// **Known problems:** None.
214 /// x.map(|a| a + 1).unwrap_or_else(some_function)
216 declare_clippy_lint! {
217 pub RESULT_MAP_UNWRAP_OR_ELSE,
219 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `.ok().map_or_else(g, f)`"
222 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
224 /// **Why is this bad?** Readability, this can be written more concisely as
227 /// **Known problems:** The order of the arguments is not in execution order.
231 /// opt.map_or(None, |a| a + 1)
233 declare_clippy_lint! {
234 pub OPTION_MAP_OR_NONE,
236 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
239 /// **What it does:** Checks for usage of `_.filter(_).next()`.
241 /// **Why is this bad?** Readability, this can be written more concisely as
244 /// **Known problems:** None.
248 /// iter.filter(|x| x == 0).next()
250 declare_clippy_lint! {
253 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
256 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
258 /// **Why is this bad?** Readability, this can be written more concisely as a
259 /// single method call.
261 /// **Known problems:**
265 /// iter.map(|x| x.iter()).flatten()
267 declare_clippy_lint! {
270 "using combinations of `flatten` and `map` which can usually be written as a single method call"
273 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
274 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
276 /// **Why is this bad?** Readability, this can be written more concisely as a
277 /// single method call.
279 /// **Known problems:** Often requires a condition + Option/Iterator creation
280 /// inside the closure.
284 /// iter.filter(|x| x == 0).map(|x| x * 2)
286 declare_clippy_lint! {
289 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
292 /// **What it does:** Checks for an iterator search (such as `find()`,
293 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
295 /// **Why is this bad?** Readability, this can be written more concisely as
298 /// **Known problems:** None.
302 /// iter.find(|x| x == 0).is_some()
304 declare_clippy_lint! {
307 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
310 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
311 /// if it starts with a given char.
313 /// **Why is this bad?** Readability, this can be written more concisely as
314 /// `_.starts_with(_)`.
316 /// **Known problems:** None.
320 /// name.chars().next() == Some('_')
322 declare_clippy_lint! {
325 "using `.chars().next()` to check if a string starts with a char"
328 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
329 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
330 /// `unwrap_or_default` instead.
332 /// **Why is this bad?** The function will always be called and potentially
333 /// allocate an object acting as the default.
335 /// **Known problems:** If the function has side-effects, not calling it will
336 /// change the semantic of the program, but you shouldn't rely on that anyway.
340 /// foo.unwrap_or(String::new())
342 /// this can instead be written:
344 /// foo.unwrap_or_else(String::new)
348 /// foo.unwrap_or_default()
350 declare_clippy_lint! {
353 "using any `*or` method with a function call, which suggests `*or_else`"
356 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
357 /// etc., and suggests to use `unwrap_or_else` instead
359 /// **Why is this bad?** The function will always be called.
361 /// **Known problems:** If the function has side-effects, not calling it will
362 /// change the semantic of the program, but you shouldn't rely on that anyway.
366 /// foo.expect(&format!("Err {}: {}", err_code, err_msg))
370 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str())
372 /// this can instead be written:
374 /// foo.unwrap_or_else(|_| panic!("Err {}: {}", err_code, err_msg))
376 declare_clippy_lint! {
379 "using any `expect` method with a function call"
382 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
384 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
385 /// generics, not for using the `clone` method on a concrete type.
387 /// **Known problems:** None.
393 declare_clippy_lint! {
396 "using `clone` on a `Copy` type"
399 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
400 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
401 /// function syntax instead (e.g. `Rc::clone(foo)`).
403 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
404 /// can obscure the fact that only the pointer is being cloned, not the underlying
411 declare_clippy_lint! {
412 pub CLONE_ON_REF_PTR,
414 "using 'clone' on a ref-counted pointer"
417 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
419 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
420 /// cloning the underlying `T`.
422 /// **Known problems:** None.
429 /// let z = y.clone();
430 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
433 declare_clippy_lint! {
434 pub CLONE_DOUBLE_REF,
436 "using `clone` on `&&T`"
439 /// **What it does:** Checks for `new` not returning `Self`.
441 /// **Why is this bad?** As a convention, `new` methods are used to make a new
442 /// instance of a type.
444 /// **Known problems:** None.
449 /// fn new(..) -> NotAFoo {
453 declare_clippy_lint! {
456 "not returning `Self` in a `new` method"
459 /// **What it does:** Checks for string methods that receive a single-character
460 /// `str` as an argument, e.g. `_.split("x")`.
462 /// **Why is this bad?** Performing these methods using a `char` is faster than
465 /// **Known problems:** Does not catch multi-byte unicode characters.
468 /// `_.split("x")` could be `_.split('x')`
469 declare_clippy_lint! {
470 pub SINGLE_CHAR_PATTERN,
472 "using a single-character str where a char could be used, e.g. `_.split(\"x\")`"
475 /// **What it does:** Checks for getting the inner pointer of a temporary
478 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
479 /// as the `CString` is alive.
481 /// **Known problems:** None.
485 /// let c_str = CString::new("foo").unwrap().as_ptr();
487 /// call_some_ffi_func(c_str);
490 /// Here `c_str` point to a freed address. The correct use would be:
492 /// let c_str = CString::new("foo").unwrap();
494 /// call_some_ffi_func(c_str.as_ptr());
497 declare_clippy_lint! {
498 pub TEMPORARY_CSTRING_AS_PTR,
500 "getting the inner pointer of a temporary `CString`"
503 /// **What it does:** Checks for use of `.iter().nth()` (and the related
504 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
506 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
509 /// **Known problems:** None.
513 /// let some_vec = vec![0, 1, 2, 3];
514 /// let bad_vec = some_vec.iter().nth(3);
515 /// let bad_slice = &some_vec[..].iter().nth(3);
517 /// The correct use would be:
519 /// let some_vec = vec![0, 1, 2, 3];
520 /// let bad_vec = some_vec.get(3);
521 /// let bad_slice = &some_vec[..].get(3);
523 declare_clippy_lint! {
526 "using `.iter().nth()` on a standard library type with O(1) element access"
529 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
531 /// **Why is this bad?** `.nth(x)` is cleaner
533 /// **Known problems:** None.
537 /// let some_vec = vec![0, 1, 2, 3];
538 /// let bad_vec = some_vec.iter().skip(3).next();
539 /// let bad_slice = &some_vec[..].iter().skip(3).next();
541 /// The correct use would be:
543 /// let some_vec = vec![0, 1, 2, 3];
544 /// let bad_vec = some_vec.iter().nth(3);
545 /// let bad_slice = &some_vec[..].iter().nth(3);
547 declare_clippy_lint! {
550 "using `.skip(x).next()` on an iterator"
553 /// **What it does:** Checks for use of `.get().unwrap()` (or
554 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
556 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
559 /// **Known problems:** Not a replacement for error handling: Using either
560 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
561 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
562 /// temporary placeholder for dealing with the `Option` type, then this does
563 /// not mitigate the need for error handling. If there is a chance that `.get()`
564 /// will be `None` in your program, then it is advisable that the `None` case
565 /// is handled in a future refactor instead of using `.unwrap()` or the Index
570 /// let some_vec = vec![0, 1, 2, 3];
571 /// let last = some_vec.get(3).unwrap();
572 /// *some_vec.get_mut(0).unwrap() = 1;
574 /// The correct use would be:
576 /// let some_vec = vec![0, 1, 2, 3];
577 /// let last = some_vec[3];
580 declare_clippy_lint! {
583 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
586 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
587 /// `&str` or `String`.
589 /// **Why is this bad?** `.push_str(s)` is clearer
591 /// **Known problems:** None.
596 /// let def = String::from("def");
597 /// let mut s = String::new();
598 /// s.extend(abc.chars());
599 /// s.extend(def.chars());
601 /// The correct use would be:
604 /// let def = String::from("def");
605 /// let mut s = String::new();
607 /// s.push_str(&def));
609 declare_clippy_lint! {
610 pub STRING_EXTEND_CHARS,
612 "using `x.extend(s.chars())` where s is a `&str` or `String`"
615 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
618 /// **Why is this bad?** `.to_vec()` is clearer
620 /// **Known problems:** None.
624 /// let s = [1, 2, 3, 4, 5];
625 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
627 /// The better use would be:
629 /// let s = [1, 2, 3, 4, 5];
630 /// let s2: Vec<isize> = s.to_vec();
632 declare_clippy_lint! {
633 pub ITER_CLONED_COLLECT,
635 "using `.cloned().collect()` on slice to create a `Vec`"
638 /// **What it does:** Checks for usage of `.chars().last()` or
639 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
641 /// **Why is this bad?** Readability, this can be written more concisely as
642 /// `_.ends_with(_)`.
644 /// **Known problems:** None.
648 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
650 declare_clippy_lint! {
653 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
656 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
657 /// types before and after the call are the same.
659 /// **Why is this bad?** The call is unnecessary.
661 /// **Known problems:** None.
665 /// let x: &[i32] = &[1, 2, 3, 4, 5];
666 /// do_stuff(x.as_ref());
668 /// The correct use would be:
670 /// let x: &[i32] = &[1, 2, 3, 4, 5];
673 declare_clippy_lint! {
676 "using `as_ref` where the types before and after the call are the same"
679 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
680 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
681 /// `sum` or `product`.
683 /// **Why is this bad?** Readability.
685 /// **Known problems:** False positive in pattern guards. Will be resolved once
686 /// non-lexical lifetimes are stable.
690 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
692 /// This could be written as:
694 /// let _ = (0..3).any(|x| x > 2);
696 declare_clippy_lint! {
697 pub UNNECESSARY_FOLD,
699 "using `fold` when a more succinct alternative exists"
702 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
703 /// More specifically it checks if the closure provided is only performing one of the
704 /// filter or map operations and suggests the appropriate option.
706 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
707 /// operation is being performed.
709 /// **Known problems:** None
713 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
715 /// As there is no transformation of the argument this could be written as:
717 /// let _ = (0..3).filter(|&x| x > 2);
721 /// let _ = (0..4).filter_map(i32::checked_abs);
723 /// As there is no conditional check on the argument this could be written as:
725 /// let _ = (0..4).map(i32::checked_abs);
727 declare_clippy_lint! {
728 pub UNNECESSARY_FILTER_MAP,
730 "using `filter_map` when a more succinct alternative exists"
733 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
736 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
737 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
738 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
739 /// like calling `iter` would. Furthermore, when the standard library actually
740 /// [implements the `into_iter` method][25725] which moves the content out of the array, the
741 /// original use of `into_iter` got inferred with the wrong type and the code will be broken.
743 /// **Known problems:** None
748 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
751 /// [25725]: https://github.com/rust-lang/rust/issues/25725
752 declare_clippy_lint! {
753 pub INTO_ITER_ON_ARRAY,
755 "using `.into_iter()` on an array"
758 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
761 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
762 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
763 /// `iter_mut` directly.
765 /// **Known problems:** None
770 /// let _ = (&vec![3, 4, 5]).into_iter();
772 declare_clippy_lint! {
773 pub INTO_ITER_ON_REF,
775 "using `.into_iter()` on a reference"
778 impl LintPass for Pass {
779 fn get_lints(&self) -> LintArray {
783 SHOULD_IMPLEMENT_TRAIT,
784 WRONG_SELF_CONVENTION,
785 WRONG_PUB_SELF_CONVENTION,
787 OPTION_MAP_UNWRAP_OR,
788 OPTION_MAP_UNWRAP_OR_ELSE,
789 RESULT_MAP_UNWRAP_OR_ELSE,
801 TEMPORARY_CSTRING_AS_PTR,
812 UNNECESSARY_FILTER_MAP,
818 fn name(&self) -> &'static str {
823 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
824 #[allow(clippy::cyclomatic_complexity)]
825 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
826 if in_macro(expr.span) {
830 let (method_names, arg_lists) = method_calls(expr, 2);
831 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
832 let method_names: Vec<&str> = method_names.iter().map(std::convert::AsRef::as_ref).collect();
834 match method_names.as_slice() {
835 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
836 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
837 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
838 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
839 ["unwrap_or", "map"] => lint_map_unwrap_or(cx, expr, arg_lists[1], arg_lists[0]),
840 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
841 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
842 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
843 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
844 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
845 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
846 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
847 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
848 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
849 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
850 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
851 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
852 ["as_ptr", "unwrap"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
853 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
854 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
855 ["next", "skip"] => lint_iter_skip_next(cx, expr),
856 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
857 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
858 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
859 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
860 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
865 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
866 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
867 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
869 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
870 if args.len() == 1 && method_call.ident.name == "clone" {
871 lint_clone_on_copy(cx, expr, &args[0], self_ty);
872 lint_clone_on_ref_ptr(cx, expr, &args[0]);
876 ty::Ref(_, ty, _) if ty.sty == ty::Str => {
877 for &(method, pos) in &PATTERN_METHODS {
878 if method_call.ident.name == method && args.len() > pos {
879 lint_single_char_pattern(cx, expr, &args[pos]);
883 ty::Ref(..) if method_call.ident.name == "into_iter" => {
884 lint_into_iter(cx, expr, self_ty, *method_span);
889 hir::ExprKind::Binary(op, ref lhs, ref rhs)
890 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
892 let mut info = BinaryExprInfo {
896 eq: op.node == hir::BinOpKind::Eq,
898 lint_binary_expr_with_method_call(cx, &mut info);
904 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
905 if in_external_macro(cx.sess(), implitem.span) {
908 let name = implitem.ident.name;
909 let parent = cx.tcx.hir().get_parent(implitem.id);
910 let item = cx.tcx.hir().expect_item(parent);
911 let def_id = cx.tcx.hir().local_def_id(item.id);
912 let ty = cx.tcx.type_of(def_id);
914 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
915 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
916 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
917 if let hir::ItemKind::Impl(_, _, _, _, None, ref self_ty, _) = item.node;
919 if cx.access_levels.is_exported(implitem.id) {
920 // check missing trait implementations
921 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
922 if name == method_name &&
923 sig.decl.inputs.len() == n_args &&
924 out_type.matches(cx, &sig.decl.output) &&
925 self_kind.matches(cx, first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
926 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
927 "defining a method called `{}` on this type; consider implementing \
928 the `{}` trait or choosing a less ambiguous name", name, trait_name));
933 // check conventions w.r.t. conversion method names and predicates
934 let is_copy = is_copy(cx, ty);
935 for &(ref conv, self_kinds) in &CONVENTIONS {
936 if conv.check(&name.as_str()) {
939 .any(|k| k.matches(cx, first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics)) {
940 let lint = if item.vis.node.is_pub() {
941 WRONG_PUB_SELF_CONVENTION
943 WRONG_SELF_CONVENTION
948 &format!("methods called `{}` usually take {}; consider choosing a less \
952 .map(|k| k.description())
957 // Only check the first convention to match (CONVENTIONS should be listed from most to least
965 if let hir::ImplItemKind::Method(_, _) = implitem.node {
966 let ret_ty = return_ty(cx, implitem.id);
968 // walk the return type and check for Self (this does not check associated types)
969 for inner_type in ret_ty.walk() {
970 if same_tys(cx, ty, inner_type) {
975 // if return type is impl trait, check the associated types
976 if let ty::Opaque(def_id, _) = ret_ty.sty {
977 // one of the associated types must be Self
978 for predicate in &cx.tcx.predicates_of(def_id).predicates {
980 (Predicate::Projection(poly_projection_predicate), _) => {
981 let binder = poly_projection_predicate.ty();
982 let associated_type = binder.skip_binder();
983 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
985 // if the associated type is self, early return and do not trigger lint
986 if associated_type_is_self_type {
995 if name == "new" && !same_tys(cx, ret_ty, ty) {
1000 "methods called `new` usually return `Self`",
1007 /// Checks for the `OR_FUN_CALL` lint.
1008 #[allow(clippy::too_many_lines)]
1009 fn lint_or_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1010 /// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1011 fn check_unwrap_or_default(
1012 cx: &LateContext<'_, '_>,
1015 self_expr: &hir::Expr,
1024 if name == "unwrap_or" {
1025 if let hir::ExprKind::Path(ref qpath) = fun.node {
1026 let path = &*last_path_segment(qpath).ident.as_str();
1028 if ["default", "new"].contains(&path) {
1029 let arg_ty = cx.tables.expr_ty(arg);
1030 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1036 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1037 let mut applicability = Applicability::MachineApplicable;
1042 &format!("use of `{}` followed by a call to `{}`", name, path),
1045 "{}.unwrap_or_default()",
1046 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1059 /// Check for `*or(foo())`.
1060 #[allow(clippy::too_many_arguments)]
1061 fn check_general_case(
1062 cx: &LateContext<'_, '_>,
1066 self_expr: &hir::Expr,
1071 // (path, fn_has_argument, methods, suffix)
1072 let know_types: &[(&[_], _, &[_], _)] = &[
1073 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1074 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1075 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1076 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1079 // early check if the name is one we care about
1080 if know_types.iter().all(|k| !k.2.contains(&name)) {
1084 // don't lint for constant values
1085 let owner_def = cx.tcx.hir().get_parent_did(arg.id);
1086 let promotable = cx.tcx.rvalue_promotable_map(owner_def).contains(&arg.hir_id.local_id);
1091 let self_ty = cx.tables.expr_ty(self_expr);
1093 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1094 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1096 (fn_has_arguments, poss, suffix)
1101 if !poss.contains(&name) {
1105 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1106 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1107 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1108 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1110 let span_replace_word = method_span.with_hi(span.hi());
1115 &format!("use of `{}` followed by a function call", name),
1117 format!("{}_{}({})", name, suffix, sugg),
1118 Applicability::HasPlaceholders,
1122 if args.len() == 2 {
1123 match args[1].node {
1124 hir::ExprKind::Call(ref fun, ref or_args) => {
1125 let or_has_args = !or_args.is_empty();
1126 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1139 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1146 !or_args.is_empty(),
1154 /// Checks for the `EXPECT_FUN_CALL` lint.
1155 #[allow(clippy::too_many_lines)]
1156 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1157 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1159 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr) -> &'a hir::Expr {
1160 let mut arg_root = arg;
1162 arg_root = match &arg_root.node {
1163 hir::ExprKind::AddrOf(_, expr) => expr,
1164 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1165 if call_args.len() == 1
1166 && (method_name.ident.name == "as_str" || method_name.ident.name == "as_ref")
1168 let arg_type = cx.tables.expr_ty(&call_args[0]);
1169 let base_type = walk_ptrs_ty(arg_type);
1170 base_type.sty == ty::Str || match_type(cx, base_type, &paths::STRING)
1184 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1185 // converted to string.
1186 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr) -> bool {
1187 let arg_ty = cx.tables.expr_ty(arg);
1188 if match_type(cx, arg_ty, &paths::STRING) {
1191 if let ty::Ref(ty::ReStatic, ty, ..) = arg_ty.sty {
1192 if ty.sty == ty::Str {
1199 fn generate_format_arg_snippet(
1200 cx: &LateContext<'_, '_>,
1202 applicability: &mut Applicability,
1204 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1205 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1206 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1207 return format_arg_expr_tup
1209 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1218 fn is_call(node: &hir::ExprKind) -> bool {
1220 hir::ExprKind::AddrOf(_, expr) => {
1223 hir::ExprKind::Call(..)
1224 | hir::ExprKind::MethodCall(..)
1225 // These variants are debatable or require further examination
1226 | hir::ExprKind::If(..)
1227 | hir::ExprKind::Match(..)
1228 | hir::ExprKind::Block{ .. } => true,
1233 if args.len() != 2 || name != "expect" || !is_call(&args[1].node) {
1237 let receiver_type = cx.tables.expr_ty(&args[0]);
1238 let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
1240 } else if match_type(cx, receiver_type, &paths::RESULT) {
1246 let arg_root = get_arg_root(cx, &args[1]);
1248 let span_replace_word = method_span.with_hi(expr.span.hi());
1250 let mut applicability = Applicability::MachineApplicable;
1252 //Special handling for `format!` as arg_root
1253 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.node {
1254 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1255 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].node {
1256 let fmt_spec = &format_args[0];
1257 let fmt_args = &format_args[1];
1259 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1261 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1263 let sugg = args.join(", ");
1269 &format!("use of `{}` followed by a function call", name),
1271 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1280 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1281 if requires_to_string(cx, arg_root) {
1282 arg_root_snippet.to_mut().push_str(".to_string()");
1289 &format!("use of `{}` followed by a function call", name),
1291 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1296 /// Checks for the `CLONE_ON_COPY` lint.
1297 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1298 let ty = cx.tables.expr_ty(expr);
1299 if let ty::Ref(_, inner, _) = arg_ty.sty {
1300 if let ty::Ref(_, innermost, _) = inner.sty {
1305 "using `clone` on a double-reference; \
1306 this will copy the reference instead of cloning the inner type",
1308 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1309 let mut ty = innermost;
1311 while let ty::Ref(_, inner, _) = ty.sty {
1315 let refs: String = iter::repeat('&').take(n + 1).collect();
1316 let derefs: String = iter::repeat('*').take(n).collect();
1317 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1320 "try dereferencing it",
1321 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1322 Applicability::MaybeIncorrect,
1326 "or try being explicit about what type to clone",
1328 Applicability::MaybeIncorrect,
1333 return; // don't report clone_on_copy
1337 if is_copy(cx, ty) {
1339 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1340 // x.clone() might have dereferenced x, possibly through Deref impls
1341 if cx.tables.expr_ty(arg) == ty {
1342 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1344 let parent = cx.tcx.hir().get_parent_node(expr.id);
1345 match cx.tcx.hir().get(parent) {
1346 hir::Node::Expr(parent) => match parent.node {
1347 // &*x is a nop, &x.clone() is not
1348 hir::ExprKind::AddrOf(..) |
1349 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1350 hir::ExprKind::MethodCall(..) => return,
1353 hir::Node::Stmt(stmt) => {
1354 if let hir::StmtKind::Local(ref loc) = stmt.node {
1355 if let hir::PatKind::Ref(..) = loc.pat.node {
1356 // let ref y = *x borrows x, let ref y = x.clone() does not
1364 let deref_count = cx
1366 .expr_adjustments(arg)
1369 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
1376 let derefs: String = iter::repeat('*').take(deref_count).collect();
1377 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
1382 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1383 if let Some((text, snip)) = snip {
1384 db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
1390 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1391 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1393 if let ty::Adt(_, subst) = obj_ty.sty {
1394 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1396 } else if match_type(cx, obj_ty, &paths::ARC) {
1398 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1408 "using '.clone()' on a ref-counted pointer",
1411 "{}::<{}>::clone(&{})",
1414 snippet(cx, arg.span, "_")
1416 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1421 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1423 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1424 let target = &arglists[0][0];
1425 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1426 let ref_str = if self_ty.sty == ty::Str {
1428 } else if match_type(cx, self_ty, &paths::STRING) {
1434 let mut applicability = Applicability::MachineApplicable;
1437 STRING_EXTEND_CHARS,
1439 "calling `.extend(_.chars())`",
1442 "{}.push_str({}{})",
1443 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1445 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1452 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1453 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1454 if match_type(cx, obj_ty, &paths::STRING) {
1455 lint_string_extend(cx, expr, args);
1459 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1461 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1463 if let hir::ExprKind::Path(ref path) = fun.node;
1464 if let Def::Method(did) = cx.tables.qpath_def(path, fun.hir_id);
1465 if match_def_path(cx.tcx, did, &paths::CSTRING_NEW);
1469 TEMPORARY_CSTRING_AS_PTR,
1471 "you are getting the inner pointer of a temporary `CString`",
1473 db.note("that pointer will be invalid outside this expression");
1474 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1480 fn lint_iter_cloned_collect(cx: &LateContext<'_, '_>, expr: &hir::Expr, iter_args: &[hir::Expr]) {
1481 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC)
1482 && derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some()
1486 ITER_CLONED_COLLECT,
1488 "called `cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1494 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1495 fn check_fold_with_op(
1496 cx: &LateContext<'_, '_>,
1497 fold_args: &[hir::Expr],
1499 replacement_method_name: &str,
1500 replacement_has_args: bool,
1503 // Extract the body of the closure passed to fold
1504 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1505 let closure_body = cx.tcx.hir().body(body_id);
1506 let closure_expr = remove_blocks(&closure_body.value);
1508 // Check if the closure body is of the form `acc <op> some_expr(x)`
1509 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1510 if bin_op.node == op;
1512 // Extract the names of the two arguments to the closure
1513 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1514 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1516 if match_var(&*left_expr, first_arg_ident);
1517 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1520 // Span containing `.fold(...)`
1521 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1522 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1524 let mut applicability = Applicability::MachineApplicable;
1525 let sugg = if replacement_has_args {
1527 ".{replacement}(|{s}| {r})",
1528 replacement = replacement_method_name,
1529 s = second_arg_ident,
1530 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1535 replacement = replacement_method_name,
1543 // TODO #2371 don't suggest e.g. .any(|x| f(x)) if we can suggest .any(f)
1544 "this `.fold` can be written more succinctly using another method",
1553 // Check that this is a call to Iterator::fold rather than just some function called fold
1554 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1559 fold_args.len() == 3,
1560 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
1563 // Check if the first argument to .fold is a suitable literal
1564 match fold_args[1].node {
1565 hir::ExprKind::Lit(ref lit) => match lit.node {
1566 ast::LitKind::Bool(false) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Or, "any", true),
1567 ast::LitKind::Bool(true) => check_fold_with_op(cx, fold_args, hir::BinOpKind::And, "all", true),
1568 ast::LitKind::Int(0, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Add, "sum", false),
1569 ast::LitKind::Int(1, _) => check_fold_with_op(cx, fold_args, hir::BinOpKind::Mul, "product", false),
1576 fn lint_iter_nth(cx: &LateContext<'_, '_>, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) {
1577 let mut_str = if is_mut { "_mut" } else { "" };
1578 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1580 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1582 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1585 return; // caller is not a type that we want to lint
1593 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1594 mut_str, caller_type
1599 fn lint_get_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, get_args: &[hir::Expr], is_mut: bool) {
1600 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1601 // because they do not implement `IndexMut`
1602 let mut applicability = Applicability::MachineApplicable;
1603 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1604 let get_args_str = if get_args.len() > 1 {
1605 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1607 return; // not linting on a .get().unwrap() chain or variant
1610 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1611 needs_ref = get_args_str.parse::<usize>().is_ok();
1613 } else if match_type(cx, expr_ty, &paths::VEC) {
1614 needs_ref = get_args_str.parse::<usize>().is_ok();
1616 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1617 needs_ref = get_args_str.parse::<usize>().is_ok();
1619 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1622 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1626 return; // caller is not a type that we want to lint
1629 let mut span = expr.span;
1631 // Handle the case where the result is immedately dereferenced
1632 // by not requiring ref and pulling the dereference into the
1636 if let Some(parent) = get_parent_expr(cx, expr);
1637 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.node;
1644 let mut_str = if is_mut { "_mut" } else { "" };
1645 let borrow_str = if !needs_ref {
1658 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1659 mut_str, caller_type
1665 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1672 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1673 // lint if caller of skip is an Iterator
1674 if match_trait_method(cx, expr, &paths::ITERATOR) {
1679 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1684 fn derefs_to_slice(cx: &LateContext<'_, '_>, expr: &hir::Expr, ty: Ty<'_>) -> Option<sugg::Sugg<'static>> {
1685 fn may_slice(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1687 ty::Slice(_) => true,
1688 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1689 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1690 ty::Array(_, size) => size.assert_usize(cx.tcx).expect("array length") < 32,
1691 ty::Ref(_, inner, _) => may_slice(cx, inner),
1696 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1697 if path.ident.name == "iter" && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1698 sugg::Sugg::hir_opt(cx, &args[0]).map(sugg::Sugg::addr)
1704 ty::Slice(_) => sugg::Sugg::hir_opt(cx, expr),
1705 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => sugg::Sugg::hir_opt(cx, expr),
1706 ty::Ref(_, inner, _) => {
1707 if may_slice(cx, inner) {
1708 sugg::Sugg::hir_opt(cx, expr)
1718 /// lint use of `unwrap()` for `Option`s and `Result`s
1719 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1720 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1722 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1723 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1724 } else if match_type(cx, obj_ty, &paths::RESULT) {
1725 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1730 if let Some((lint, kind, none_value)) = mess {
1736 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1737 using expect() to provide a better panic \
1745 /// lint use of `ok().expect()` for `Result`s
1746 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1747 // lint if the caller of `ok()` is a `Result`
1748 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1749 let result_type = cx.tables.expr_ty(&ok_args[0]);
1750 if let Some(error_type) = get_error_type(cx, result_type) {
1751 if has_debug_impl(error_type, cx) {
1756 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1763 /// lint use of `map().unwrap_or()` for `Option`s
1764 fn lint_map_unwrap_or(cx: &LateContext<'_, '_>, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) {
1765 // lint if the caller of `map()` is an `Option`
1766 if match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION) {
1767 // get snippets for args to map() and unwrap_or()
1768 let map_snippet = snippet(cx, map_args[1].span, "..");
1769 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1771 // comparing the snippet from source to raw text ("None") below is safe
1772 // because we already have checked the type.
1773 let arg = if unwrap_snippet == "None" { "None" } else { "a" };
1774 let suggest = if unwrap_snippet == "None" {
1780 "called `map(f).unwrap_or({})` on an Option value. \
1781 This can be done more directly by calling `{}` instead",
1784 // lint, with note if neither arg is > 1 line and both map() and
1785 // unwrap_or() have the same span
1786 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1787 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1788 if same_span && !multiline {
1789 let suggest = if unwrap_snippet == "None" {
1790 format!("and_then({})", map_snippet)
1792 format!("map_or({}, {})", unwrap_snippet, map_snippet)
1795 "replace `map({}).unwrap_or({})` with `{}`",
1796 map_snippet, unwrap_snippet, suggest
1798 span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, ¬e);
1799 } else if same_span && multiline {
1800 span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
1805 /// lint use of `map().flatten()` for `Iterators`
1806 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_args: &'tcx [hir::Expr]) {
1807 // lint if caller of `.map().flatten()` is an Iterator
1808 if match_trait_method(cx, expr, &paths::ITERATOR) {
1809 let msg = "called `map(..).flatten()` on an `Iterator`. \
1810 This is more succinctly expressed by calling `.flat_map(..)`";
1811 let self_snippet = snippet(cx, map_args[0].span, "..");
1812 let func_snippet = snippet(cx, map_args[1].span, "..");
1813 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1814 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1817 "try using flat_map instead",
1819 Applicability::MachineApplicable,
1825 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1826 fn lint_map_unwrap_or_else<'a, 'tcx>(
1827 cx: &LateContext<'a, 'tcx>,
1828 expr: &'tcx hir::Expr,
1829 map_args: &'tcx [hir::Expr],
1830 unwrap_args: &'tcx [hir::Expr],
1832 // lint if the caller of `map()` is an `Option`
1833 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1834 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1835 if is_option || is_result {
1837 let msg = if is_option {
1838 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1839 `map_or_else(g, f)` instead"
1841 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1842 `ok().map_or_else(g, f)` instead"
1844 // get snippets for args to map() and unwrap_or_else()
1845 let map_snippet = snippet(cx, map_args[1].span, "..");
1846 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1847 // lint, with note if neither arg is > 1 line and both map() and
1848 // unwrap_or_else() have the same span
1849 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1850 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1851 if same_span && !multiline {
1855 OPTION_MAP_UNWRAP_OR_ELSE
1857 RESULT_MAP_UNWRAP_OR_ELSE
1863 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1866 if is_result { "ok()." } else { "" }
1869 } else if same_span && multiline {
1873 OPTION_MAP_UNWRAP_OR_ELSE
1875 RESULT_MAP_UNWRAP_OR_ELSE
1884 /// lint use of `_.map_or(None, _)` for `Option`s
1885 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
1886 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
1887 // check if the first non-self argument to map_or() is None
1888 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
1889 match_qpath(qpath, &paths::OPTION_NONE)
1894 if map_or_arg_is_none {
1896 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
1897 `and_then(f)` instead";
1898 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
1899 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
1900 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
1901 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
1904 "try using and_then instead",
1906 Applicability::MachineApplicable, // snippet
1913 /// lint use of `filter().next()` for `Iterators`
1914 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
1915 // lint if caller of `.filter().next()` is an Iterator
1916 if match_trait_method(cx, expr, &paths::ITERATOR) {
1917 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
1918 `.find(p)` instead.";
1919 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1920 if filter_snippet.lines().count() <= 1 {
1921 // add note if not multi-line
1928 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
1931 span_lint(cx, FILTER_NEXT, expr.span, msg);
1936 /// lint use of `filter().map()` for `Iterators`
1937 fn lint_filter_map<'a, 'tcx>(
1938 cx: &LateContext<'a, 'tcx>,
1939 expr: &'tcx hir::Expr,
1940 _filter_args: &'tcx [hir::Expr],
1941 _map_args: &'tcx [hir::Expr],
1943 // lint if caller of `.filter().map()` is an Iterator
1944 if match_trait_method(cx, expr, &paths::ITERATOR) {
1945 let msg = "called `filter(p).map(q)` on an `Iterator`. \
1946 This is more succinctly expressed by calling `.filter_map(..)` instead.";
1947 span_lint(cx, FILTER_MAP, expr.span, msg);
1951 /// lint use of `filter().map()` for `Iterators`
1952 fn lint_filter_map_map<'a, 'tcx>(
1953 cx: &LateContext<'a, 'tcx>,
1954 expr: &'tcx hir::Expr,
1955 _filter_args: &'tcx [hir::Expr],
1956 _map_args: &'tcx [hir::Expr],
1958 // lint if caller of `.filter().map()` is an Iterator
1959 if match_trait_method(cx, expr, &paths::ITERATOR) {
1960 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
1961 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
1962 span_lint(cx, FILTER_MAP, expr.span, msg);
1966 /// lint use of `filter().flat_map()` for `Iterators`
1967 fn lint_filter_flat_map<'a, 'tcx>(
1968 cx: &LateContext<'a, 'tcx>,
1969 expr: &'tcx hir::Expr,
1970 _filter_args: &'tcx [hir::Expr],
1971 _map_args: &'tcx [hir::Expr],
1973 // lint if caller of `.filter().flat_map()` is an Iterator
1974 if match_trait_method(cx, expr, &paths::ITERATOR) {
1975 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
1976 This is more succinctly expressed by calling `.flat_map(..)` \
1977 and filtering by returning an empty Iterator.";
1978 span_lint(cx, FILTER_MAP, expr.span, msg);
1982 /// lint use of `filter_map().flat_map()` for `Iterators`
1983 fn lint_filter_map_flat_map<'a, 'tcx>(
1984 cx: &LateContext<'a, 'tcx>,
1985 expr: &'tcx hir::Expr,
1986 _filter_args: &'tcx [hir::Expr],
1987 _map_args: &'tcx [hir::Expr],
1989 // lint if caller of `.filter_map().flat_map()` is an Iterator
1990 if match_trait_method(cx, expr, &paths::ITERATOR) {
1991 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
1992 This is more succinctly expressed by calling `.flat_map(..)` \
1993 and filtering by returning an empty Iterator.";
1994 span_lint(cx, FILTER_MAP, expr.span, msg);
1998 /// lint searching an Iterator followed by `is_some()`
1999 fn lint_search_is_some<'a, 'tcx>(
2000 cx: &LateContext<'a, 'tcx>,
2001 expr: &'tcx hir::Expr,
2002 search_method: &str,
2003 search_args: &'tcx [hir::Expr],
2004 is_some_args: &'tcx [hir::Expr],
2006 // lint if caller of search is an Iterator
2007 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2009 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2010 expressed by calling `any()`.",
2013 let search_snippet = snippet(cx, search_args[1].span, "..");
2014 if search_snippet.lines().count() <= 1 {
2015 // add note if not multi-line
2023 "replace `{0}({1}).is_some()` with `any({1})`",
2024 search_method, search_snippet
2028 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
2033 /// Used for `lint_binary_expr_with_method_call`.
2034 #[derive(Copy, Clone)]
2035 struct BinaryExprInfo<'a> {
2036 expr: &'a hir::Expr,
2037 chain: &'a hir::Expr,
2038 other: &'a hir::Expr,
2042 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
2043 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
2044 macro_rules! lint_with_both_lhs_and_rhs {
2045 ($func:ident, $cx:expr, $info:ident) => {
2046 if !$func($cx, $info) {
2047 ::std::mem::swap(&mut $info.chain, &mut $info.other);
2048 if $func($cx, $info) {
2055 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2056 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2057 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2058 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2061 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_NEXT_CMP` lints.
2063 cx: &LateContext<'_, '_>,
2064 info: &BinaryExprInfo<'_>,
2065 chain_methods: &[&str],
2066 lint: &'static Lint,
2070 if let Some(args) = method_chain_args(info.chain, chain_methods);
2071 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2072 if arg_char.len() == 1;
2073 if let hir::ExprKind::Path(ref qpath) = fun.node;
2074 if let Some(segment) = single_segment_path(qpath);
2075 if segment.ident.name == "Some";
2077 let mut applicability = Applicability::MachineApplicable;
2078 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2080 if self_ty.sty != ty::Str {
2088 &format!("you should use the `{}` method", suggest),
2090 format!("{}{}.{}({})",
2091 if info.eq { "" } else { "!" },
2092 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2094 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2105 /// Checks for the `CHARS_NEXT_CMP` lint.
2106 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2107 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2110 /// Checks for the `CHARS_LAST_CMP` lint.
2111 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2112 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2115 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2119 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2120 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2121 cx: &LateContext<'a, 'tcx>,
2122 info: &BinaryExprInfo<'_>,
2123 chain_methods: &[&str],
2124 lint: &'static Lint,
2128 if let Some(args) = method_chain_args(info.chain, chain_methods);
2129 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2130 if let ast::LitKind::Char(c) = lit.node;
2132 let mut applicability = Applicability::MachineApplicable;
2137 &format!("you should use the `{}` method", suggest),
2139 format!("{}{}.{}('{}')",
2140 if info.eq { "" } else { "!" },
2141 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2154 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2155 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2156 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2159 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2160 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2161 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2164 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2168 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2169 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2171 if let hir::ExprKind::Lit(lit) = &arg.node;
2172 if let ast::LitKind::Str(r, _) = lit.node;
2173 if r.as_str().len() == 1;
2175 let mut applicability = Applicability::MachineApplicable;
2176 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2177 let hint = format!("'{}'", &snip[1..snip.len() - 1]);
2180 SINGLE_CHAR_PATTERN,
2182 "single-character string constant used as pattern",
2183 "try using a char instead",
2191 /// Checks for the `USELESS_ASREF` lint.
2192 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2193 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2194 // check if the call is to the actual `AsRef` or `AsMut` trait
2195 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2196 // check if the type after `as_ref` or `as_mut` is the same as before
2197 let recvr = &as_ref_args[0];
2198 let rcv_ty = cx.tables.expr_ty(recvr);
2199 let res_ty = cx.tables.expr_ty(expr);
2200 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2201 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2202 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2203 // allow the `as_ref` or `as_mut` if it is followed by another method call
2205 if let Some(parent) = get_parent_expr(cx, expr);
2206 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.node;
2207 if span != &expr.span;
2213 let mut applicability = Applicability::MachineApplicable;
2218 &format!("this call to `{}` does nothing", call_name),
2220 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2227 fn ty_has_iter_method(
2228 cx: &LateContext<'_, '_>,
2229 self_ref_ty: ty::Ty<'_>,
2230 ) -> Option<(&'static Lint, &'static str, &'static str)> {
2231 if let Some(ty_name) = has_iter_method(cx, self_ref_ty) {
2232 let lint = match ty_name {
2233 "array" | "PathBuf" => INTO_ITER_ON_ARRAY,
2234 _ => INTO_ITER_ON_REF,
2236 let mutbl = match self_ref_ty.sty {
2237 ty::Ref(_, _, mutbl) => mutbl,
2238 _ => unreachable!(),
2240 let method_name = match mutbl {
2241 hir::MutImmutable => "iter",
2242 hir::MutMutable => "iter_mut",
2244 Some((lint, ty_name, method_name))
2250 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: ty::Ty<'_>, method_span: Span) {
2251 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2254 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2260 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2264 method_name.to_string(),
2265 Applicability::MachineApplicable,
2270 /// Given a `Result<T, E>` type, return its error type (`E`).
2271 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2272 if let ty::Adt(_, substs) = ty.sty {
2273 if match_type(cx, ty, &paths::RESULT) {
2274 substs.types().nth(1)
2283 /// This checks whether a given type is known to implement Debug.
2284 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2285 match cx.tcx.lang_items().debug_trait() {
2286 Some(debug) => implements_trait(cx, ty, debug, &[]),
2293 StartsWith(&'static str),
2297 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2298 (Convention::Eq("new"), &[SelfKind::No]),
2299 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2300 (Convention::StartsWith("from_"), &[SelfKind::No]),
2301 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2302 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2303 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2304 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2308 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2309 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2310 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2311 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2312 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2313 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2314 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2315 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2316 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2317 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2318 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2319 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2320 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2321 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2322 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2323 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2324 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2325 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2326 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2327 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2328 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2329 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2330 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2331 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2332 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2333 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2334 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2335 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2336 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2337 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2338 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2342 const PATTERN_METHODS: [(&str, usize); 17] = [
2350 ("split_terminator", 1),
2351 ("rsplit_terminator", 1),
2356 ("match_indices", 1),
2357 ("rmatch_indices", 1),
2358 ("trim_start_matches", 1),
2359 ("trim_end_matches", 1),
2362 #[derive(Clone, Copy, PartialEq, Debug)]
2373 cx: &LateContext<'_, '_>,
2377 allow_value_for_ref: bool,
2378 generics: &hir::Generics,
2380 // Self types in the HIR are desugared to explicit self types. So it will
2383 // where SomeType can be `Self` or an explicit impl self type (e.g. `Foo` if
2384 // the impl is on `Foo`)
2385 // Thus, we only need to test equality against the impl self type or if it is
2387 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
2388 // `Self`, `&mut Self`,
2389 // and `Box<Self>`, including the equivalent types with `Foo`.
2391 let is_actually_self = |ty| is_self_ty(ty) || SpanlessEq::new(cx).eq_ty(ty, self_ty);
2394 SelfKind::Value => is_actually_self(ty),
2395 SelfKind::Ref | SelfKind::RefMut => {
2396 if allow_value_for_ref && is_actually_self(ty) {
2400 hir::TyKind::Rptr(_, ref mt_ty) => {
2401 let mutability_match = if self == SelfKind::Ref {
2402 mt_ty.mutbl == hir::MutImmutable
2404 mt_ty.mutbl == hir::MutMutable
2406 is_actually_self(&mt_ty.ty) && mutability_match
2415 SelfKind::Value => false,
2416 SelfKind::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
2417 SelfKind::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
2418 SelfKind::No => true,
2423 fn description(self) -> &'static str {
2425 SelfKind::Value => "self by value",
2426 SelfKind::Ref => "self by reference",
2427 SelfKind::RefMut => "self by mutable reference",
2428 SelfKind::No => "no self",
2433 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
2434 single_segment_ty(ty).map_or(false, |seg| {
2435 generics.params.iter().any(|param| match param.kind {
2436 hir::GenericParamKind::Type { .. } => {
2437 param.name.ident().name == seg.ident.name
2438 && param.bounds.iter().any(|bound| {
2439 if let hir::GenericBound::Trait(ref ptr, ..) = *bound {
2440 let path = &ptr.trait_ref.path;
2441 match_path(path, name)
2442 && path.segments.last().map_or(false, |s| {
2443 if let Some(ref params) = s.args {
2444 if params.parenthesized {
2447 // FIXME(flip1995): messy, improve if there is a better option
2449 let types: Vec<_> = params
2452 .filter_map(|arg| match arg {
2453 hir::GenericArg::Type(ty) => Some(ty),
2457 types.len() == 1 && (is_self_ty(&types[0]) || is_ty(&*types[0], self_ty))
2473 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
2474 match (&ty.node, &self_ty.node) {
2476 &hir::TyKind::Path(hir::QPath::Resolved(_, ref ty_path)),
2477 &hir::TyKind::Path(hir::QPath::Resolved(_, ref self_ty_path)),
2481 .map(|seg| seg.ident.name)
2482 .eq(self_ty_path.segments.iter().map(|seg| seg.ident.name)),
2487 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2488 if let hir::TyKind::Path(ref path) = ty.node {
2489 single_segment_path(path)
2496 fn check(&self, other: &str) -> bool {
2498 Convention::Eq(this) => this == other,
2499 Convention::StartsWith(this) => other.starts_with(this) && this != other,
2504 impl fmt::Display for Convention {
2505 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2507 Convention::Eq(this) => this.fmt(f),
2508 Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2513 #[derive(Clone, Copy)]
2522 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2523 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2525 (OutType::Unit, &hir::DefaultReturn(_)) => true,
2526 (OutType::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2527 (OutType::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2528 (OutType::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2529 (OutType::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2535 fn is_bool(ty: &hir::Ty) -> bool {
2536 if let hir::TyKind::Path(ref p) = ty.node {
2537 match_qpath(p, &["bool"])