1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 use crate::rustc::hir;
12 use crate::rustc::hir::def::Def;
13 use crate::rustc::lint::{in_external_macro, LateContext, LateLintPass, Lint, LintArray, LintContext, LintPass};
14 use crate::rustc::ty::{self, Ty, TyKind, Predicate};
15 use crate::rustc::{declare_tool_lint, lint_array};
16 use crate::rustc_errors::Applicability;
17 use crate::syntax::ast;
18 use crate::syntax::source_map::{BytePos, Span};
19 use crate::syntax::symbol::LocalInternedString;
20 use crate::utils::paths;
21 use crate::utils::sugg;
23 get_arg_name, get_trait_def_id, implements_trait, in_macro, is_copy, is_expn_of, is_self, is_self_ty,
24 iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method, match_type,
25 match_var, method_calls, method_chain_args, remove_blocks, return_ty, same_tys, single_segment_path, snippet,
26 snippet_with_macro_callsite, snippet_with_applicability, span_lint, span_lint_and_sugg, span_lint_and_then,
27 span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
29 use if_chain::if_chain;
35 mod unnecessary_filter_map;
40 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
42 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
43 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
44 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
45 /// `Allow` by default.
47 /// **Known problems:** None.
53 declare_clippy_lint! {
54 pub OPTION_UNWRAP_USED,
56 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
59 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
61 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
62 /// values. Normally, you want to implement more sophisticated error handling,
63 /// and propagate errors upwards with `try!`.
65 /// Even if you want to panic on errors, not all `Error`s implement good
66 /// messages on display. Therefore it may be beneficial to look at the places
67 /// where they may get displayed. Activate this lint to do just that.
69 /// **Known problems:** None.
75 declare_clippy_lint! {
76 pub RESULT_UNWRAP_USED,
78 "using `Result.unwrap()`, which might be better handled"
81 /// **What it does:** Checks for methods that should live in a trait
82 /// implementation of a `std` trait (see [llogiq's blog
83 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
84 /// information) instead of an inherent implementation.
86 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
87 /// the code, often with very little cost. Also people seeing a `mul(...)`
89 /// may expect `*` to work equally, so you should have good reason to disappoint
92 /// **Known problems:** None.
98 /// fn add(&self, other: &X) -> X { .. }
101 declare_clippy_lint! {
102 pub SHOULD_IMPLEMENT_TRAIT,
104 "defining a method that should be implementing a std trait"
107 /// **What it does:** Checks for methods with certain name prefixes and which
108 /// doesn't match how self is taken. The actual rules are:
110 /// |Prefix |`self` taken |
111 /// |-------|----------------------|
112 /// |`as_` |`&self` or `&mut self`|
114 /// |`into_`|`self` |
115 /// |`is_` |`&self` or none |
116 /// |`to_` |`&self` |
118 /// **Why is this bad?** Consistency breeds readability. If you follow the
119 /// conventions, your users won't be surprised that they, e.g., need to supply a
120 /// mutable reference to a `as_..` function.
122 /// **Known problems:** None.
127 /// fn as_str(self) -> &str { .. }
130 declare_clippy_lint! {
131 pub WRONG_SELF_CONVENTION,
133 "defining a method named with an established prefix (like \"into_\") that takes \
134 `self` with the wrong convention"
137 /// **What it does:** This is the same as
138 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
140 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
142 /// **Known problems:** Actually *renaming* the function may break clients if
143 /// the function is part of the public interface. In that case, be mindful of
144 /// the stability guarantees you've given your users.
149 /// pub fn as_str(self) -> &str { .. }
152 declare_clippy_lint! {
153 pub WRONG_PUB_SELF_CONVENTION,
155 "defining a public method named with an established prefix (like \"into_\") that takes \
156 `self` with the wrong convention"
159 /// **What it does:** Checks for usage of `ok().expect(..)`.
161 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
162 /// directly to get a better error message.
164 /// **Known problems:** The error type needs to implement `Debug`
168 /// x.ok().expect("why did I do this again?")
170 declare_clippy_lint! {
173 "using `ok().expect()`, which gives worse error messages than \
174 calling `expect` directly on the Result"
177 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
179 /// **Why is this bad?** Readability, this can be written more concisely as
180 /// `_.map_or(_, _)`.
182 /// **Known problems:** The order of the arguments is not in execution order
186 /// x.map(|a| a + 1).unwrap_or(0)
188 declare_clippy_lint! {
189 pub OPTION_MAP_UNWRAP_OR,
191 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
195 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
197 /// **Why is this bad?** Readability, this can be written more concisely as
198 /// `_.map_or_else(_, _)`.
200 /// **Known problems:** The order of the arguments is not in execution order.
204 /// x.map(|a| a + 1).unwrap_or_else(some_function)
206 declare_clippy_lint! {
207 pub OPTION_MAP_UNWRAP_OR_ELSE,
209 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
213 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
215 /// **Why is this bad?** Readability, this can be written more concisely as
216 /// `result.ok().map_or_else(_, _)`.
218 /// **Known problems:** None.
222 /// x.map(|a| a + 1).unwrap_or_else(some_function)
224 declare_clippy_lint! {
225 pub RESULT_MAP_UNWRAP_OR_ELSE,
227 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
228 `.ok().map_or_else(g, f)`"
231 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
233 /// **Why is this bad?** Readability, this can be written more concisely as
236 /// **Known problems:** The order of the arguments is not in execution order.
240 /// opt.map_or(None, |a| a + 1)
242 declare_clippy_lint! {
243 pub OPTION_MAP_OR_NONE,
245 "using `Option.map_or(None, f)`, which is more succinctly expressed as \
249 /// **What it does:** Checks for usage of `_.filter(_).next()`.
251 /// **Why is this bad?** Readability, this can be written more concisely as
254 /// **Known problems:** None.
258 /// iter.filter(|x| x == 0).next()
260 declare_clippy_lint! {
263 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
266 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
268 /// **Why is this bad?** Readability, this can be written more concisely as a
269 /// single method call.
271 /// **Known problems:**
275 /// iter.map(|x| x.iter()).flatten()
277 declare_clippy_lint! {
280 "using combinations of `flatten` and `map` which can usually be written as a \
284 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
285 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
287 /// **Why is this bad?** Readability, this can be written more concisely as a
288 /// single method call.
290 /// **Known problems:** Often requires a condition + Option/Iterator creation
291 /// inside the closure.
295 /// iter.filter(|x| x == 0).map(|x| x * 2)
297 declare_clippy_lint! {
300 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can \
301 usually be written as a single method call"
304 /// **What it does:** Checks for an iterator search (such as `find()`,
305 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
307 /// **Why is this bad?** Readability, this can be written more concisely as
310 /// **Known problems:** None.
314 /// iter.find(|x| x == 0).is_some()
316 declare_clippy_lint! {
319 "using an iterator search followed by `is_some()`, which is more succinctly \
320 expressed as a call to `any()`"
323 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
324 /// if it starts with a given char.
326 /// **Why is this bad?** Readability, this can be written more concisely as
327 /// `_.starts_with(_)`.
329 /// **Known problems:** None.
333 /// name.chars().next() == Some('_')
335 declare_clippy_lint! {
338 "using `.chars().next()` to check if a string starts with a char"
341 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
342 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
343 /// `unwrap_or_default` instead.
345 /// **Why is this bad?** The function will always be called and potentially
346 /// allocate an object acting as the default.
348 /// **Known problems:** If the function has side-effects, not calling it will
349 /// change the semantic of the program, but you shouldn't rely on that anyway.
353 /// foo.unwrap_or(String::new())
355 /// this can instead be written:
357 /// foo.unwrap_or_else(String::new)
361 /// foo.unwrap_or_default()
363 declare_clippy_lint! {
366 "using any `*or` method with a function call, which suggests `*or_else`"
369 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
370 /// etc., and suggests to use `unwrap_or_else` instead
372 /// **Why is this bad?** The function will always be called.
374 /// **Known problems:** If the function has side-effects, not calling it will
375 /// change the semantic of the program, but you shouldn't rely on that anyway.
379 /// foo.expect(&format!("Err {}: {}", err_code, err_msg))
383 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str())
385 /// this can instead be written:
387 /// foo.unwrap_or_else(|_| panic!("Err {}: {}", err_code, err_msg))
389 declare_clippy_lint! {
392 "using any `expect` method with a function call"
395 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
397 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
398 /// generics, not for using the `clone` method on a concrete type.
400 /// **Known problems:** None.
406 declare_clippy_lint! {
409 "using `clone` on a `Copy` type"
412 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
413 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
414 /// function syntax instead (e.g. `Rc::clone(foo)`).
416 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
417 /// can obscure the fact that only the pointer is being cloned, not the underlying
424 declare_clippy_lint! {
425 pub CLONE_ON_REF_PTR,
427 "using 'clone' on a ref-counted pointer"
430 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
432 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
433 /// cloning the underlying `T`.
435 /// **Known problems:** None.
442 /// let z = y.clone();
443 /// println!("{:p} {:p}",*y, z); // prints out the same pointer
446 declare_clippy_lint! {
447 pub CLONE_DOUBLE_REF,
449 "using `clone` on `&&T`"
452 /// **What it does:** Checks for `new` not returning `Self`.
454 /// **Why is this bad?** As a convention, `new` methods are used to make a new
455 /// instance of a type.
457 /// **Known problems:** None.
462 /// fn new(..) -> NotAFoo {
466 declare_clippy_lint! {
469 "not returning `Self` in a `new` method"
472 /// **What it does:** Checks for string methods that receive a single-character
473 /// `str` as an argument, e.g. `_.split("x")`.
475 /// **Why is this bad?** Performing these methods using a `char` is faster than
478 /// **Known problems:** Does not catch multi-byte unicode characters.
481 /// `_.split("x")` could be `_.split('x')`
482 declare_clippy_lint! {
483 pub SINGLE_CHAR_PATTERN,
485 "using a single-character str where a char could be used, e.g. \
489 /// **What it does:** Checks for getting the inner pointer of a temporary
492 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
493 /// as the `CString` is alive.
495 /// **Known problems:** None.
499 /// let c_str = CString::new("foo").unwrap().as_ptr();
501 /// call_some_ffi_func(c_str);
504 /// Here `c_str` point to a freed address. The correct use would be:
506 /// let c_str = CString::new("foo").unwrap();
508 /// call_some_ffi_func(c_str.as_ptr());
511 declare_clippy_lint! {
512 pub TEMPORARY_CSTRING_AS_PTR,
514 "getting the inner pointer of a temporary `CString`"
517 /// **What it does:** Checks for use of `.iter().nth()` (and the related
518 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
520 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
523 /// **Known problems:** None.
527 /// let some_vec = vec![0, 1, 2, 3];
528 /// let bad_vec = some_vec.iter().nth(3);
529 /// let bad_slice = &some_vec[..].iter().nth(3);
531 /// The correct use would be:
533 /// let some_vec = vec![0, 1, 2, 3];
534 /// let bad_vec = some_vec.get(3);
535 /// let bad_slice = &some_vec[..].get(3);
537 declare_clippy_lint! {
540 "using `.iter().nth()` on a standard library type with O(1) element access"
543 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
545 /// **Why is this bad?** `.nth(x)` is cleaner
547 /// **Known problems:** None.
551 /// let some_vec = vec![0, 1, 2, 3];
552 /// let bad_vec = some_vec.iter().skip(3).next();
553 /// let bad_slice = &some_vec[..].iter().skip(3).next();
555 /// The correct use would be:
557 /// let some_vec = vec![0, 1, 2, 3];
558 /// let bad_vec = some_vec.iter().nth(3);
559 /// let bad_slice = &some_vec[..].iter().nth(3);
561 declare_clippy_lint! {
564 "using `.skip(x).next()` on an iterator"
567 /// **What it does:** Checks for use of `.get().unwrap()` (or
568 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
570 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
573 /// **Known problems:** Not a replacement for error handling: Using either
574 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
575 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
576 /// temporary placeholder for dealing with the `Option` type, then this does
577 /// not mitigate the need for error handling. If there is a chance that `.get()`
578 /// will be `None` in your program, then it is advisable that the `None` case
579 /// is handled in a future refactor instead of using `.unwrap()` or the Index
584 /// let some_vec = vec![0, 1, 2, 3];
585 /// let last = some_vec.get(3).unwrap();
586 /// *some_vec.get_mut(0).unwrap() = 1;
588 /// The correct use would be:
590 /// let some_vec = vec![0, 1, 2, 3];
591 /// let last = some_vec[3];
594 declare_clippy_lint! {
597 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
600 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
601 /// `&str` or `String`.
603 /// **Why is this bad?** `.push_str(s)` is clearer
605 /// **Known problems:** None.
610 /// let def = String::from("def");
611 /// let mut s = String::new();
612 /// s.extend(abc.chars());
613 /// s.extend(def.chars());
615 /// The correct use would be:
618 /// let def = String::from("def");
619 /// let mut s = String::new();
621 /// s.push_str(&def));
623 declare_clippy_lint! {
624 pub STRING_EXTEND_CHARS,
626 "using `x.extend(s.chars())` where s is a `&str` or `String`"
629 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
632 /// **Why is this bad?** `.to_vec()` is clearer
634 /// **Known problems:** None.
638 /// let s = [1,2,3,4,5];
639 /// let s2 : Vec<isize> = s[..].iter().cloned().collect();
641 /// The better use would be:
643 /// let s = [1,2,3,4,5];
644 /// let s2 : Vec<isize> = s.to_vec();
646 declare_clippy_lint! {
647 pub ITER_CLONED_COLLECT,
649 "using `.cloned().collect()` on slice to create a `Vec`"
652 /// **What it does:** Checks for usage of `.chars().last()` or
653 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
655 /// **Why is this bad?** Readability, this can be written more concisely as
656 /// `_.ends_with(_)`.
658 /// **Known problems:** None.
662 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
664 declare_clippy_lint! {
667 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
670 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
671 /// types before and after the call are the same.
673 /// **Why is this bad?** The call is unnecessary.
675 /// **Known problems:** None.
679 /// let x: &[i32] = &[1,2,3,4,5];
680 /// do_stuff(x.as_ref());
682 /// The correct use would be:
684 /// let x: &[i32] = &[1,2,3,4,5];
687 declare_clippy_lint! {
690 "using `as_ref` where the types before and after the call are the same"
694 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
695 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
696 /// `sum` or `product`.
698 /// **Why is this bad?** Readability.
700 /// **Known problems:** False positive in pattern guards. Will be resolved once
701 /// non-lexical lifetimes are stable.
705 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
707 /// This could be written as:
709 /// let _ = (0..3).any(|x| x > 2);
711 declare_clippy_lint! {
712 pub UNNECESSARY_FOLD,
714 "using `fold` when a more succinct alternative exists"
718 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
719 /// More specifically it checks if the closure provided is only performing one of the
720 /// filter or map operations and suggests the appropriate option.
722 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
723 /// operation is being performed.
725 /// **Known problems:** None
729 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
731 /// As there is no transformation of the argument this could be written as:
733 /// let _ = (0..3).filter(|&x| x > 2);
737 /// let _ = (0..4).filter_map(i32::checked_abs);
739 /// As there is no conditional check on the argument this could be written as:
741 /// let _ = (0..4).map(i32::checked_abs);
743 declare_clippy_lint! {
744 pub UNNECESSARY_FILTER_MAP,
746 "using `filter_map` when a more succinct alternative exists"
749 /// **What it does:** Checks for `into_iter` calls on types which should be replaced by `iter` or
752 /// **Why is this bad?** Arrays and `PathBuf` do not yet have an `into_iter` method which move out
753 /// their content into an iterator. Auto-referencing resolves the `into_iter` call to its reference
754 /// instead, like `<&[T; N] as IntoIterator>::into_iter`, which just iterates over item references
755 /// like calling `iter` would. Furthermore, when the standard library actually
756 /// [implements the `into_iter` method][25725] which moves the content out of the array, the
757 /// original use of `into_iter` got inferred with the wrong type and the code will be broken.
759 /// **Known problems:** None
764 /// let _ = [1, 2, 3].into_iter().map(|x| *x).collect::<Vec<u32>>();
767 /// [25725]: https://github.com/rust-lang/rust/issues/25725
768 declare_clippy_lint! {
769 pub INTO_ITER_ON_ARRAY,
771 "using `.into_iter()` on an array"
774 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
777 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
778 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
779 /// `iter_mut` directly.
781 /// **Known problems:** None
786 /// let _ = (&vec![3, 4, 5]).into_iter();
788 declare_clippy_lint! {
789 pub INTO_ITER_ON_REF,
791 "using `.into_iter()` on a reference"
794 impl LintPass for Pass {
795 fn get_lints(&self) -> LintArray {
799 SHOULD_IMPLEMENT_TRAIT,
800 WRONG_SELF_CONVENTION,
801 WRONG_PUB_SELF_CONVENTION,
803 OPTION_MAP_UNWRAP_OR,
804 OPTION_MAP_UNWRAP_OR_ELSE,
805 RESULT_MAP_UNWRAP_OR_ELSE,
817 TEMPORARY_CSTRING_AS_PTR,
828 UNNECESSARY_FILTER_MAP,
835 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
836 #[allow(clippy::cyclomatic_complexity)]
837 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
838 if in_macro(expr.span) {
842 let (method_names, arg_lists) = method_calls(expr, 2);
843 let method_names: Vec<LocalInternedString> = method_names.iter().map(|s| s.as_str()).collect();
844 let method_names: Vec<&str> = method_names.iter().map(|s| s.as_ref()).collect();
846 match method_names.as_slice() {
847 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
848 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
849 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
850 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
851 ["unwrap_or", "map"] => lint_map_unwrap_or(cx, expr, arg_lists[1], arg_lists[0]),
852 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
853 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
854 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
855 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
856 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
857 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
858 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
859 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
860 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0]),
861 ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
862 ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
863 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
864 ["as_ptr", "unwrap"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
865 ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
866 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
867 ["next", "skip"] => lint_iter_skip_next(cx, expr),
868 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
869 ["as_ref", ..] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
870 ["as_mut", ..] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
871 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0]),
872 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
877 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
879 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
880 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
882 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
883 if args.len() == 1 && method_call.ident.name == "clone" {
884 lint_clone_on_copy(cx, expr, &args[0], self_ty);
885 lint_clone_on_ref_ptr(cx, expr, &args[0]);
889 ty::Ref(_, ty, _) if ty.sty == ty::Str => for &(method, pos) in &PATTERN_METHODS {
890 if method_call.ident.name == method && args.len() > pos {
891 lint_single_char_pattern(cx, expr, &args[pos]);
894 ty::Ref(..) if method_call.ident.name == "into_iter" => {
895 lint_into_iter(cx, expr, self_ty, *method_span);
900 hir::ExprKind::Binary(op, ref lhs, ref rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
901 let mut info = BinaryExprInfo {
905 eq: op.node == hir::BinOpKind::Eq,
907 lint_binary_expr_with_method_call(cx, &mut info);
913 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
914 if in_external_macro(cx.sess(), implitem.span) {
917 let name = implitem.ident.name;
918 let parent = cx.tcx.hir.get_parent(implitem.id);
919 let item = cx.tcx.hir.expect_item(parent);
920 let def_id = cx.tcx.hir.local_def_id(item.id);
921 let ty = cx.tcx.type_of(def_id);
923 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
924 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
925 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir.body(id)).next();
926 if let hir::ItemKind::Impl(_, _, _, _, None, ref self_ty, _) = item.node;
928 if cx.access_levels.is_exported(implitem.id) {
929 // check missing trait implementations
930 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
931 if name == method_name &&
932 sig.decl.inputs.len() == n_args &&
933 out_type.matches(cx, &sig.decl.output) &&
934 self_kind.matches(cx, first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
935 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
936 "defining a method called `{}` on this type; consider implementing \
937 the `{}` trait or choosing a less ambiguous name", name, trait_name));
942 // check conventions w.r.t. conversion method names and predicates
943 let is_copy = is_copy(cx, ty);
944 for &(ref conv, self_kinds) in &CONVENTIONS {
945 if conv.check(&name.as_str()) {
948 .any(|k| k.matches(cx, first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics)) {
949 let lint = if item.vis.node.is_pub() {
950 WRONG_PUB_SELF_CONVENTION
952 WRONG_SELF_CONVENTION
957 &format!("methods called `{}` usually take {}; consider choosing a less \
961 .map(|k| k.description())
966 // Only check the first convention to match (CONVENTIONS should be listed from most to least specific)
973 if let hir::ImplItemKind::Method(_, _) = implitem.node {
974 let ret_ty = return_ty(cx, implitem.id);
976 // walk the return type and check for Self (this does not check associated types)
977 for inner_type in ret_ty.walk() {
978 if same_tys(cx, ty, inner_type) { return; }
981 // if return type is impl trait, check the associated types
982 if let TyKind::Opaque(def_id, _) = ret_ty.sty {
984 // one of the associated types must be Self
985 for predicate in &cx.tcx.predicates_of(def_id).predicates {
987 (Predicate::Projection(poly_projection_predicate), _) => {
988 let binder = poly_projection_predicate.ty();
989 let associated_type = binder.skip_binder();
990 let associated_type_is_self_type = same_tys(cx, ty, associated_type);
992 // if the associated type is self, early return and do not trigger lint
993 if associated_type_is_self_type { return; }
1000 if name == "new" && !same_tys(cx, ret_ty, ty) {
1004 "methods called `new` usually return `Self`");
1010 /// Checks for the `OR_FUN_CALL` lint.
1011 fn lint_or_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1012 /// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1013 fn check_unwrap_or_default(
1014 cx: &LateContext<'_, '_>,
1017 self_expr: &hir::Expr,
1026 if name == "unwrap_or" {
1027 if let hir::ExprKind::Path(ref qpath) = fun.node {
1028 let path = &*last_path_segment(qpath).ident.as_str();
1030 if ["default", "new"].contains(&path) {
1031 let arg_ty = cx.tables.expr_ty(arg);
1032 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
1038 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
1039 let mut applicability = Applicability::MachineApplicable;
1044 &format!("use of `{}` followed by a call to `{}`", name, path),
1046 format!("{}.unwrap_or_default()", snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)),
1058 /// Check for `*or(foo())`.
1059 #[allow(clippy::too_many_arguments)]
1060 fn check_general_case(
1061 cx: &LateContext<'_, '_>,
1065 self_expr: &hir::Expr,
1070 // (path, fn_has_argument, methods, suffix)
1071 let know_types: &[(&[_], _, &[_], _)] = &[
1072 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1073 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1074 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1075 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1078 // early check if the name is one we care about
1079 if know_types.iter().all(|k| !k.2.contains(&name)) {
1083 // don't lint for constant values
1084 let owner_def = cx.tcx.hir.get_parent_did(arg.id);
1085 let promotable = cx.tcx.rvalue_promotable_map(owner_def).contains(&arg.hir_id.local_id);
1090 let self_ty = cx.tables.expr_ty(self_expr);
1092 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
1093 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
1095 (fn_has_arguments, poss, suffix)
1100 if !poss.contains(&name) {
1104 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1105 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1106 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1107 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1109 let span_replace_word = method_span.with_hi(span.hi());
1114 &format!("use of `{}` followed by a function call", name),
1116 format!("{}_{}({})", name, suffix, sugg),
1117 Applicability::HasPlaceholders,
1121 if args.len() == 2 {
1122 match args[1].node {
1123 hir::ExprKind::Call(ref fun, ref or_args) => {
1124 let or_has_args = !or_args.is_empty();
1125 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1126 check_general_case(cx, name, method_span, fun.span, &args[0], &args[1], or_has_args, expr.span);
1129 hir::ExprKind::MethodCall(_, span, ref or_args) => {
1130 check_general_case(cx, name, method_span, span, &args[0], &args[1], !or_args.is_empty(), expr.span)
1137 /// Checks for the `EXPECT_FUN_CALL` lint.
1138 fn lint_expect_fun_call(cx: &LateContext<'_, '_>, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
1139 fn extract_format_args(arg: &hir::Expr) -> Option<&hir::HirVec<hir::Expr>> {
1140 let arg = match &arg.node {
1141 hir::ExprKind::AddrOf(_, expr)=> expr,
1142 hir::ExprKind::MethodCall(method_name, _, args)
1143 if method_name.ident.name == "as_str" ||
1144 method_name.ident.name == "as_ref"
1149 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg.node {
1150 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
1151 if let hir::ExprKind::Call(_, ref format_args) = inner_args[0].node {
1152 return Some(format_args);
1160 fn generate_format_arg_snippet(
1161 cx: &LateContext<'_, '_>,
1163 applicability: &mut Applicability,
1165 if let hir::ExprKind::AddrOf(_, ref format_arg) = a.node {
1166 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.node {
1167 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.node {
1168 return snippet_with_applicability(cx, format_arg_expr_tup[0].span, "..", applicability).into_owned();
1173 snippet(cx, a.span, "..").into_owned()
1176 fn check_general_case(
1177 cx: &LateContext<'_, '_>,
1180 self_expr: &hir::Expr,
1184 fn is_call(node: &hir::ExprKind) -> bool {
1186 hir::ExprKind::AddrOf(_, expr) => {
1189 hir::ExprKind::Call(..)
1190 | hir::ExprKind::MethodCall(..)
1191 // These variants are debatable or require further examination
1192 | hir::ExprKind::If(..)
1193 | hir::ExprKind::Match(..)
1194 | hir::ExprKind::Block{ .. } => true,
1199 if name != "expect" {
1203 let self_type = cx.tables.expr_ty(self_expr);
1204 let known_types = &[&paths::OPTION, &paths::RESULT];
1206 // if not a known type, return early
1207 if known_types.iter().all(|&k| !match_type(cx, self_type, k)) {
1211 if !is_call(&arg.node) {
1215 let closure = if match_type(cx, self_type, &paths::OPTION) { "||" } else { "|_|" };
1216 let span_replace_word = method_span.with_hi(span.hi());
1218 if let Some(format_args) = extract_format_args(arg) {
1219 let mut applicability = Applicability::MachineApplicable;
1220 let args_len = format_args.len();
1221 let args: Vec<String> = format_args
1224 .map(|a| generate_format_arg_snippet(cx, a, &mut applicability))
1227 let sugg = args.join(", ");
1233 &format!("use of `{}` followed by a function call", name),
1235 format!("unwrap_or_else({} panic!({}))", closure, sugg),
1242 let mut applicability = Applicability::MachineApplicable;
1243 let sugg: Cow<'_, _> = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
1249 &format!("use of `{}` followed by a function call", name),
1251 format!("unwrap_or_else({} {{ let msg = {}; panic!(msg) }}))", closure, sugg),
1256 if args.len() == 2 {
1257 match args[1].node {
1258 hir::ExprKind::Lit(_) => {},
1259 _ => check_general_case(cx, name, method_span, &args[0], &args[1], expr.span),
1264 /// Checks for the `CLONE_ON_COPY` lint.
1265 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty<'_>) {
1266 let ty = cx.tables.expr_ty(expr);
1267 if let ty::Ref(_, inner, _) = arg_ty.sty {
1268 if let ty::Ref(_, innermost, _) = inner.sty {
1273 "using `clone` on a double-reference; \
1274 this will copy the reference instead of cloning the inner type",
1275 |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1276 let mut ty = innermost;
1278 while let ty::Ref(_, inner, _) = ty.sty {
1282 let refs: String = iter::repeat('&').take(n + 1).collect();
1283 let derefs: String = iter::repeat('*').take(n).collect();
1284 let explicit = format!("{}{}::clone({})", refs, ty, snip);
1285 db.span_suggestion_with_applicability(
1287 "try dereferencing it",
1288 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1289 Applicability::MaybeIncorrect,
1291 db.span_suggestion_with_applicability(
1293 "or try being explicit about what type to clone",
1295 Applicability::MaybeIncorrect,
1299 return; // don't report clone_on_copy
1303 if is_copy(cx, ty) {
1305 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1306 if let ty::Ref(..) = cx.tables.expr_ty(arg).sty {
1307 let parent = cx.tcx.hir.get_parent_node(expr.id);
1308 match cx.tcx.hir.get(parent) {
1309 hir::Node::Expr(parent) => match parent.node {
1310 // &*x is a nop, &x.clone() is not
1311 hir::ExprKind::AddrOf(..) |
1312 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1313 hir::ExprKind::MethodCall(..) => return,
1316 hir::Node::Stmt(stmt) => {
1317 if let hir::StmtKind::Decl(ref decl, _) = stmt.node {
1318 if let hir::DeclKind::Local(ref loc) = decl.node {
1319 if let hir::PatKind::Ref(..) = loc.pat.node {
1320 // let ref y = *x borrows x, let ref y = x.clone() does not
1328 snip = Some(("try dereferencing it", format!("{}", snippet.deref())));
1330 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1335 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1336 if let Some((text, snip)) = snip {
1337 db.span_suggestion_with_applicability(
1341 Applicability::Unspecified,
1348 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, arg: &hir::Expr) {
1349 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
1351 if let ty::Adt(_, subst) = obj_ty.sty {
1352 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1354 } else if match_type(cx, obj_ty, &paths::ARC) {
1356 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1366 "using '.clone()' on a ref-counted pointer",
1368 format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet(cx, arg.span, "_")),
1369 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
1375 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1377 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1378 let target = &arglists[0][0];
1379 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
1380 let ref_str = if self_ty.sty == ty::Str {
1382 } else if match_type(cx, self_ty, &paths::STRING) {
1388 let mut applicability = Applicability::MachineApplicable;
1391 STRING_EXTEND_CHARS,
1393 "calling `.extend(_.chars())`",
1396 "{}.push_str({}{})",
1397 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
1399 snippet_with_applicability(cx, target.span, "_", &mut applicability)
1406 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
1407 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1408 if match_type(cx, obj_ty, &paths::STRING) {
1409 lint_string_extend(cx, expr, args);
1413 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1415 if let hir::ExprKind::Call(ref fun, ref args) = new.node;
1417 if let hir::ExprKind::Path(ref path) = fun.node;
1418 if let Def::Method(did) = cx.tables.qpath_def(path, fun.hir_id);
1419 if match_def_path(cx.tcx, did, &paths::CSTRING_NEW);
1423 TEMPORARY_CSTRING_AS_PTR,
1425 "you are getting the inner pointer of a temporary `CString`",
1427 db.note("that pointer will be invalid outside this expression");
1428 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1434 fn lint_iter_cloned_collect(cx: &LateContext<'_, '_>, expr: &hir::Expr, iter_args: &[hir::Expr]) {
1435 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC)
1436 && derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some()
1440 ITER_CLONED_COLLECT,
1442 "called `cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1448 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1449 fn check_fold_with_op(
1450 cx: &LateContext<'_, '_>,
1451 fold_args: &[hir::Expr],
1453 replacement_method_name: &str,
1454 replacement_has_args: bool) {
1457 // Extract the body of the closure passed to fold
1458 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].node;
1459 let closure_body = cx.tcx.hir.body(body_id);
1460 let closure_expr = remove_blocks(&closure_body.value);
1462 // Check if the closure body is of the form `acc <op> some_expr(x)`
1463 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1464 if bin_op.node == op;
1466 // Extract the names of the two arguments to the closure
1467 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1468 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1470 if match_var(&*left_expr, first_arg_ident);
1471 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1474 // Span containing `.fold(...)`
1475 let next_point = cx.sess().source_map().next_point(fold_args[0].span);
1476 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1478 let mut applicability = Applicability::MachineApplicable;
1479 let sugg = if replacement_has_args {
1481 ".{replacement}(|{s}| {r})",
1482 replacement = replacement_method_name,
1483 s = second_arg_ident,
1484 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
1489 replacement = replacement_method_name,
1497 // TODO #2371 don't suggest e.g. .any(|x| f(x)) if we can suggest .any(f)
1498 "this `.fold` can be written more succinctly using another method",
1507 // Check that this is a call to Iterator::fold rather than just some function called fold
1508 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1512 assert!(fold_args.len() == 3,
1513 "Expected fold_args to have three entries - the receiver, the initial value and the closure");
1515 // Check if the first argument to .fold is a suitable literal
1516 match fold_args[1].node {
1517 hir::ExprKind::Lit(ref lit) => {
1519 ast::LitKind::Bool(false) => check_fold_with_op(
1520 cx, fold_args, hir::BinOpKind::Or, "any", true
1522 ast::LitKind::Bool(true) => check_fold_with_op(
1523 cx, fold_args, hir::BinOpKind::And, "all", true
1525 ast::LitKind::Int(0, _) => check_fold_with_op(
1526 cx, fold_args, hir::BinOpKind::Add, "sum", false
1528 ast::LitKind::Int(1, _) => check_fold_with_op(
1529 cx, fold_args, hir::BinOpKind::Mul, "product", false
1538 fn lint_iter_nth(cx: &LateContext<'_, '_>, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) {
1539 let mut_str = if is_mut { "_mut" } else { "" };
1540 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1542 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1544 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1547 return; // caller is not a type that we want to lint
1555 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1562 fn lint_get_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, get_args: &[hir::Expr], is_mut: bool) {
1563 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1564 // because they do not implement `IndexMut`
1565 let mut applicability = Applicability::MachineApplicable;
1566 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1567 let get_args_str = if get_args.len() > 1 {
1568 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
1570 return; // not linting on a .get().unwrap() chain or variant
1573 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1574 needs_ref = get_args_str.parse::<usize>().is_ok();
1576 } else if match_type(cx, expr_ty, &paths::VEC) {
1577 needs_ref = get_args_str.parse::<usize>().is_ok();
1579 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1580 needs_ref = get_args_str.parse::<usize>().is_ok();
1582 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1585 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1589 return; // caller is not a type that we want to lint
1592 let mut_str = if is_mut { "_mut" } else { "" };
1593 let borrow_str = if !needs_ref { "" } else if is_mut { "&mut " } else { "&" };
1599 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1607 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
1614 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr) {
1615 // lint if caller of skip is an Iterator
1616 if match_trait_method(cx, expr, &paths::ITERATOR) {
1621 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1626 fn derefs_to_slice(cx: &LateContext<'_, '_>, expr: &hir::Expr, ty: Ty<'_>) -> Option<sugg::Sugg<'static>> {
1627 fn may_slice(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1629 ty::Slice(_) => true,
1630 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1631 ty::Adt(..) => match_type(cx, ty, &paths::VEC),
1632 ty::Array(_, size) => size.assert_usize(cx.tcx).expect("array length") < 32,
1633 ty::Ref(_, inner, _) => may_slice(cx, inner),
1638 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.node {
1639 if path.ident.name == "iter" && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1640 sugg::Sugg::hir_opt(cx, &args[0]).map(|sugg| sugg.addr())
1646 ty::Slice(_) => sugg::Sugg::hir_opt(cx, expr),
1647 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => sugg::Sugg::hir_opt(cx, expr),
1648 ty::Ref(_, inner, _) => if may_slice(cx, inner) {
1649 sugg::Sugg::hir_opt(cx, expr)
1658 /// lint use of `unwrap()` for `Option`s and `Result`s
1659 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1660 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
1662 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1663 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1664 } else if match_type(cx, obj_ty, &paths::RESULT) {
1665 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1670 if let Some((lint, kind, none_value)) = mess {
1676 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1677 using expect() to provide a better panic \
1686 /// lint use of `ok().expect()` for `Result`s
1687 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1688 // lint if the caller of `ok()` is a `Result`
1689 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1690 let result_type = cx.tables.expr_ty(&ok_args[0]);
1691 if let Some(error_type) = get_error_type(cx, result_type) {
1692 if has_debug_impl(error_type, cx) {
1697 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1704 /// lint use of `map().unwrap_or()` for `Option`s
1705 fn lint_map_unwrap_or(cx: &LateContext<'_, '_>, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) {
1706 // lint if the caller of `map()` is an `Option`
1707 if match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION) {
1708 // get snippets for args to map() and unwrap_or()
1709 let map_snippet = snippet(cx, map_args[1].span, "..");
1710 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1712 // comparing the snippet from source to raw text ("None") below is safe
1713 // because we already have checked the type.
1714 let arg = if unwrap_snippet == "None" {
1719 let suggest = if unwrap_snippet == "None" {
1725 "called `map(f).unwrap_or({})` on an Option value. \
1726 This can be done more directly by calling `{}` instead",
1730 // lint, with note if neither arg is > 1 line and both map() and
1731 // unwrap_or() have the same span
1732 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1733 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1734 if same_span && !multiline {
1735 let suggest = if unwrap_snippet == "None" {
1736 format!("and_then({})", map_snippet)
1738 format!("map_or({}, {})", unwrap_snippet, map_snippet)
1741 "replace `map({}).unwrap_or({})` with `{}`",
1746 span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, ¬e);
1747 } else if same_span && multiline {
1748 span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
1753 /// lint use of `map().flatten()` for `Iterators`
1754 fn lint_map_flatten<'a, 'tcx>(
1755 cx: &LateContext<'a, 'tcx>,
1756 expr: &'tcx hir::Expr,
1757 map_args: &'tcx [hir::Expr],
1759 // lint if caller of `.map().flatten()` is an Iterator
1760 if match_trait_method(cx, expr, &paths::ITERATOR) {
1761 let msg = "called `map(..).flatten()` on an `Iterator`. \
1762 This is more succinctly expressed by calling `.flat_map(..)`";
1763 let self_snippet = snippet(cx, map_args[0].span, "..");
1764 let func_snippet = snippet(cx, map_args[1].span, "..");
1765 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
1766 span_lint_and_then(cx, MAP_FLATTEN, expr.span, msg, |db| {
1767 db.span_suggestion_with_applicability(
1769 "try using flat_map instead",
1771 Applicability::MachineApplicable,
1777 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1778 fn lint_map_unwrap_or_else<'a, 'tcx>(
1779 cx: &LateContext<'a, 'tcx>,
1780 expr: &'tcx hir::Expr,
1781 map_args: &'tcx [hir::Expr],
1782 unwrap_args: &'tcx [hir::Expr],
1784 // lint if the caller of `map()` is an `Option`
1785 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1786 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1787 if is_option || is_result {
1789 let msg = if is_option {
1790 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1791 `map_or_else(g, f)` instead"
1793 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1794 `ok().map_or_else(g, f)` instead"
1796 // get snippets for args to map() and unwrap_or_else()
1797 let map_snippet = snippet(cx, map_args[1].span, "..");
1798 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1799 // lint, with note if neither arg is > 1 line and both map() and
1800 // unwrap_or_else() have the same span
1801 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1802 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1803 if same_span && !multiline {
1807 OPTION_MAP_UNWRAP_OR_ELSE
1809 RESULT_MAP_UNWRAP_OR_ELSE
1815 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1818 if is_result { "ok()." } else { "" }
1821 } else if same_span && multiline {
1825 OPTION_MAP_UNWRAP_OR_ELSE
1827 RESULT_MAP_UNWRAP_OR_ELSE
1836 /// lint use of `_.map_or(None, _)` for `Option`s
1837 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
1838 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
1839 // check if the first non-self argument to map_or() is None
1840 let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].node {
1841 match_qpath(qpath, &paths::OPTION_NONE)
1846 if map_or_arg_is_none {
1848 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
1849 `and_then(f)` instead";
1850 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
1851 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
1852 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
1853 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
1854 db.span_suggestion_with_applicability(
1856 "try using and_then instead",
1858 Applicability::MachineApplicable, // snippet
1865 /// lint use of `filter().next()` for `Iterators`
1866 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
1867 // lint if caller of `.filter().next()` is an Iterator
1868 if match_trait_method(cx, expr, &paths::ITERATOR) {
1869 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
1870 `.find(p)` instead.";
1871 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1872 if filter_snippet.lines().count() <= 1 {
1873 // add note if not multi-line
1880 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
1883 span_lint(cx, FILTER_NEXT, expr.span, msg);
1888 /// lint use of `filter().map()` for `Iterators`
1889 fn lint_filter_map<'a, 'tcx>(
1890 cx: &LateContext<'a, 'tcx>,
1891 expr: &'tcx hir::Expr,
1892 _filter_args: &'tcx [hir::Expr],
1893 _map_args: &'tcx [hir::Expr],
1895 // lint if caller of `.filter().map()` is an Iterator
1896 if match_trait_method(cx, expr, &paths::ITERATOR) {
1897 let msg = "called `filter(p).map(q)` on an `Iterator`. \
1898 This is more succinctly expressed by calling `.filter_map(..)` instead.";
1899 span_lint(cx, FILTER_MAP, expr.span, msg);
1903 /// lint use of `filter().map()` for `Iterators`
1904 fn lint_filter_map_map<'a, 'tcx>(
1905 cx: &LateContext<'a, 'tcx>,
1906 expr: &'tcx hir::Expr,
1907 _filter_args: &'tcx [hir::Expr],
1908 _map_args: &'tcx [hir::Expr],
1910 // lint if caller of `.filter().map()` is an Iterator
1911 if match_trait_method(cx, expr, &paths::ITERATOR) {
1912 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
1913 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
1914 span_lint(cx, FILTER_MAP, expr.span, msg);
1918 /// lint use of `filter().flat_map()` for `Iterators`
1919 fn lint_filter_flat_map<'a, 'tcx>(
1920 cx: &LateContext<'a, 'tcx>,
1921 expr: &'tcx hir::Expr,
1922 _filter_args: &'tcx [hir::Expr],
1923 _map_args: &'tcx [hir::Expr],
1925 // lint if caller of `.filter().flat_map()` is an Iterator
1926 if match_trait_method(cx, expr, &paths::ITERATOR) {
1927 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
1928 This is more succinctly expressed by calling `.flat_map(..)` \
1929 and filtering by returning an empty Iterator.";
1930 span_lint(cx, FILTER_MAP, expr.span, msg);
1934 /// lint use of `filter_map().flat_map()` for `Iterators`
1935 fn lint_filter_map_flat_map<'a, 'tcx>(
1936 cx: &LateContext<'a, 'tcx>,
1937 expr: &'tcx hir::Expr,
1938 _filter_args: &'tcx [hir::Expr],
1939 _map_args: &'tcx [hir::Expr],
1941 // lint if caller of `.filter_map().flat_map()` is an Iterator
1942 if match_trait_method(cx, expr, &paths::ITERATOR) {
1943 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
1944 This is more succinctly expressed by calling `.flat_map(..)` \
1945 and filtering by returning an empty Iterator.";
1946 span_lint(cx, FILTER_MAP, expr.span, msg);
1950 /// lint searching an Iterator followed by `is_some()`
1951 fn lint_search_is_some<'a, 'tcx>(
1952 cx: &LateContext<'a, 'tcx>,
1953 expr: &'tcx hir::Expr,
1954 search_method: &str,
1955 search_args: &'tcx [hir::Expr],
1956 is_some_args: &'tcx [hir::Expr],
1958 // lint if caller of search is an Iterator
1959 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
1961 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
1962 expressed by calling `any()`.",
1965 let search_snippet = snippet(cx, search_args[1].span, "..");
1966 if search_snippet.lines().count() <= 1 {
1967 // add note if not multi-line
1974 &format!("replace `{0}({1}).is_some()` with `any({1})`", search_method, search_snippet),
1977 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
1982 /// Used for `lint_binary_expr_with_method_call`.
1983 #[derive(Copy, Clone)]
1984 struct BinaryExprInfo<'a> {
1985 expr: &'a hir::Expr,
1986 chain: &'a hir::Expr,
1987 other: &'a hir::Expr,
1991 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
1992 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
1993 macro_rules! lint_with_both_lhs_and_rhs {
1994 ($func:ident, $cx:expr, $info:ident) => {
1995 if !$func($cx, $info) {
1996 ::std::mem::swap(&mut $info.chain, &mut $info.other);
1997 if $func($cx, $info) {
2004 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
2005 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
2006 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
2007 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
2010 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_NEXT_CMP` lints.
2012 cx: &LateContext<'_, '_>,
2013 info: &BinaryExprInfo<'_>,
2014 chain_methods: &[&str],
2015 lint: &'static Lint,
2019 if let Some(args) = method_chain_args(info.chain, chain_methods);
2020 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.node;
2021 if arg_char.len() == 1;
2022 if let hir::ExprKind::Path(ref qpath) = fun.node;
2023 if let Some(segment) = single_segment_path(qpath);
2024 if segment.ident.name == "Some";
2026 let mut applicability = Applicability::MachineApplicable;
2027 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
2029 if self_ty.sty != ty::Str {
2037 &format!("you should use the `{}` method", suggest),
2039 format!("{}{}.{}({})",
2040 if info.eq { "" } else { "!" },
2041 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2043 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
2054 /// Checks for the `CHARS_NEXT_CMP` lint.
2055 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2056 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
2059 /// Checks for the `CHARS_LAST_CMP` lint.
2060 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2061 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
2064 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
2068 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
2069 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
2070 cx: &LateContext<'a, 'tcx>,
2071 info: &BinaryExprInfo<'_>,
2072 chain_methods: &[&str],
2073 lint: &'static Lint,
2077 if let Some(args) = method_chain_args(info.chain, chain_methods);
2078 if let hir::ExprKind::Lit(ref lit) = info.other.node;
2079 if let ast::LitKind::Char(c) = lit.node;
2081 let mut applicability = Applicability::MachineApplicable;
2086 &format!("you should use the `{}` method", suggest),
2088 format!("{}{}.{}('{}')",
2089 if info.eq { "" } else { "!" },
2090 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
2103 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
2104 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2105 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
2108 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
2109 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
2110 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
2113 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
2117 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
2118 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, _expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
2120 if let hir::ExprKind::Lit(lit) = &arg.node;
2121 if let ast::LitKind::Str(r, _) = lit.node;
2122 if r.as_str().len() == 1;
2124 let mut applicability = Applicability::MachineApplicable;
2125 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
2126 let hint = format!("'{}'", &snip[1..snip.len() - 1]);
2129 SINGLE_CHAR_PATTERN,
2131 "single-character string constant used as pattern",
2132 "try using a char instead",
2140 /// Checks for the `USELESS_ASREF` lint.
2141 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
2142 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
2143 // check if the call is to the actual `AsRef` or `AsMut` trait
2144 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
2145 // check if the type after `as_ref` or `as_mut` is the same as before
2146 let recvr = &as_ref_args[0];
2147 let rcv_ty = cx.tables.expr_ty(recvr);
2148 let res_ty = cx.tables.expr_ty(expr);
2149 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
2150 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
2151 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
2152 let mut applicability = Applicability::MachineApplicable;
2157 &format!("this call to `{}` does nothing", call_name),
2159 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
2166 fn ty_has_iter_method(cx: &LateContext<'_, '_>, self_ref_ty: ty::Ty<'_>) -> Option<(&'static Lint, &'static str, &'static str)> {
2167 // FIXME: instead of this hard-coded list, we should check if `<adt>::iter`
2168 // exists and has the desired signature. Unfortunately FnCtxt is not exported
2169 // so we can't use its `lookup_method` method.
2170 static INTO_ITER_COLLECTIONS: [(&Lint, &[&str]); 13] = [
2171 (INTO_ITER_ON_REF, &paths::VEC),
2172 (INTO_ITER_ON_REF, &paths::OPTION),
2173 (INTO_ITER_ON_REF, &paths::RESULT),
2174 (INTO_ITER_ON_REF, &paths::BTREESET),
2175 (INTO_ITER_ON_REF, &paths::BTREEMAP),
2176 (INTO_ITER_ON_REF, &paths::VEC_DEQUE),
2177 (INTO_ITER_ON_REF, &paths::LINKED_LIST),
2178 (INTO_ITER_ON_REF, &paths::BINARY_HEAP),
2179 (INTO_ITER_ON_REF, &paths::HASHSET),
2180 (INTO_ITER_ON_REF, &paths::HASHMAP),
2181 (INTO_ITER_ON_ARRAY, &["std", "path", "PathBuf"]),
2182 (INTO_ITER_ON_REF, &["std", "path", "Path"]),
2183 (INTO_ITER_ON_REF, &["std", "sync", "mpsc", "Receiver"]),
2186 let (self_ty, mutbl) = match self_ref_ty.sty {
2187 ty::TyKind::Ref(_, self_ty, mutbl) => (self_ty, mutbl),
2188 _ => unreachable!(),
2190 let method_name = match mutbl {
2191 hir::MutImmutable => "iter",
2192 hir::MutMutable => "iter_mut",
2195 let def_id = match self_ty.sty {
2196 ty::TyKind::Array(..) => return Some((INTO_ITER_ON_ARRAY, "array", method_name)),
2197 ty::TyKind::Slice(..) => return Some((INTO_ITER_ON_REF, "slice", method_name)),
2198 ty::Adt(adt, _) => adt.did,
2202 for (lint, path) in &INTO_ITER_COLLECTIONS {
2203 if match_def_path(cx.tcx, def_id, path) {
2204 return Some((lint, path.last().unwrap(), method_name))
2210 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr, self_ref_ty: ty::Ty<'_>, method_span: Span) {
2211 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
2214 if let Some((lint, kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
2220 "this .into_iter() call is equivalent to .{}() and will not move the {}",
2225 method_name.to_string(),
2226 Applicability::MachineApplicable,
2232 /// Given a `Result<T, E>` type, return its error type (`E`).
2233 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
2234 if let ty::Adt(_, substs) = ty.sty {
2235 if match_type(cx, ty, &paths::RESULT) {
2236 substs.types().nth(1)
2245 /// This checks whether a given type is known to implement Debug.
2246 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
2247 match cx.tcx.lang_items().debug_trait() {
2248 Some(debug) => implements_trait(cx, ty, debug, &[]),
2255 StartsWith(&'static str),
2259 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
2260 (Convention::Eq("new"), &[SelfKind::No]),
2261 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
2262 (Convention::StartsWith("from_"), &[SelfKind::No]),
2263 (Convention::StartsWith("into_"), &[SelfKind::Value]),
2264 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
2265 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
2266 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
2270 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
2271 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
2272 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
2273 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
2274 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
2275 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
2276 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
2277 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
2278 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
2279 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
2280 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
2281 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
2282 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
2283 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
2284 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
2285 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
2286 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
2287 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
2288 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
2289 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
2290 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
2291 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
2292 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
2293 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
2294 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
2295 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
2296 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
2297 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
2298 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
2299 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
2300 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
2304 const PATTERN_METHODS: [(&str, usize); 17] = [
2312 ("split_terminator", 1),
2313 ("rsplit_terminator", 1),
2318 ("match_indices", 1),
2319 ("rmatch_indices", 1),
2320 ("trim_left_matches", 1),
2321 ("trim_right_matches", 1),
2325 #[derive(Clone, Copy, PartialEq, Debug)]
2336 cx: &LateContext<'_, '_>,
2340 allow_value_for_ref: bool,
2341 generics: &hir::Generics,
2343 // Self types in the HIR are desugared to explicit self types. So it will
2346 // where SomeType can be `Self` or an explicit impl self type (e.g. `Foo` if
2347 // the impl is on `Foo`)
2348 // Thus, we only need to test equality against the impl self type or if it is
2350 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
2351 // `Self`, `&mut Self`,
2352 // and `Box<Self>`, including the equivalent types with `Foo`.
2354 let is_actually_self = |ty| is_self_ty(ty) || SpanlessEq::new(cx).eq_ty(ty, self_ty);
2357 SelfKind::Value => is_actually_self(ty),
2358 SelfKind::Ref | SelfKind::RefMut => {
2359 if allow_value_for_ref && is_actually_self(ty) {
2363 hir::TyKind::Rptr(_, ref mt_ty) => {
2364 let mutability_match = if self == SelfKind::Ref {
2365 mt_ty.mutbl == hir::MutImmutable
2367 mt_ty.mutbl == hir::MutMutable
2369 is_actually_self(&mt_ty.ty) && mutability_match
2378 SelfKind::Value => false,
2379 SelfKind::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
2380 SelfKind::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
2381 SelfKind::No => true,
2386 fn description(self) -> &'static str {
2388 SelfKind::Value => "self by value",
2389 SelfKind::Ref => "self by reference",
2390 SelfKind::RefMut => "self by mutable reference",
2391 SelfKind::No => "no self",
2396 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
2397 single_segment_ty(ty).map_or(false, |seg| {
2398 generics.params.iter().any(|param| match param.kind {
2399 hir::GenericParamKind::Type { .. } => {
2400 param.name.ident().name == seg.ident.name && param.bounds.iter().any(|bound| {
2401 if let hir::GenericBound::Trait(ref ptr, ..) = *bound {
2402 let path = &ptr.trait_ref.path;
2403 match_path(path, name) && path.segments.last().map_or(false, |s| {
2404 if let Some(ref params) = s.args {
2405 if params.parenthesized {
2408 // FIXME(flip1995): messy, improve if there is a better option
2410 let types: Vec<_> = params.args.iter().filter_map(|arg| match arg {
2411 hir::GenericArg::Type(ty) => Some(ty),
2415 && (is_self_ty(&types[0]) || is_ty(&*types[0], self_ty))
2431 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
2432 match (&ty.node, &self_ty.node) {
2434 &hir::TyKind::Path(hir::QPath::Resolved(_, ref ty_path)),
2435 &hir::TyKind::Path(hir::QPath::Resolved(_, ref self_ty_path)),
2439 .map(|seg| seg.ident.name)
2440 .eq(self_ty_path.segments.iter().map(|seg| seg.ident.name)),
2445 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2446 if let hir::TyKind::Path(ref path) = ty.node {
2447 single_segment_path(path)
2454 fn check(&self, other: &str) -> bool {
2456 Convention::Eq(this) => this == other,
2457 Convention::StartsWith(this) => other.starts_with(this) && this != other,
2462 impl fmt::Display for Convention {
2463 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
2465 Convention::Eq(this) => this.fmt(f),
2466 Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2471 #[derive(Clone, Copy)]
2480 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FunctionRetTy) -> bool {
2481 let is_unit = |ty: &hir::Ty| SpanlessEq::new(cx).eq_ty_kind(&ty.node, &hir::TyKind::Tup(vec![].into()));
2483 (OutType::Unit, &hir::DefaultReturn(_)) => true,
2484 (OutType::Unit, &hir::Return(ref ty)) if is_unit(ty) => true,
2485 (OutType::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2486 (OutType::Any, &hir::Return(ref ty)) if !is_unit(ty) => true,
2487 (OutType::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyKind::Rptr(_, _)),
2493 fn is_bool(ty: &hir::Ty) -> bool {
2494 if let hir::TyKind::Path(ref p) = ty.node {
2495 match_qpath(p, &["bool"])