1 mod bind_instead_of_map;
2 mod inefficient_to_string;
3 mod manual_saturating_arithmetic;
4 mod option_map_unwrap_or;
5 mod unnecessary_filter_map;
11 use bind_instead_of_map::BindInsteadOfMap;
12 use if_chain::if_chain;
14 use rustc_errors::Applicability;
16 use rustc_hir::intravisit::{self, Visitor};
17 use rustc_lint::{LateContext, LateLintPass, Lint, LintContext};
18 use rustc_middle::hir::map::Map;
19 use rustc_middle::lint::in_external_macro;
20 use rustc_middle::ty::subst::GenericArgKind;
21 use rustc_middle::ty::{self, Ty, TyS};
22 use rustc_session::{declare_lint_pass, declare_tool_lint};
23 use rustc_span::source_map::Span;
24 use rustc_span::symbol::{sym, SymbolStr};
26 use crate::consts::{constant, Constant};
27 use crate::utils::usage::mutated_variables;
29 get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait, in_macro, is_copy,
30 is_ctor_or_promotable_const_function, is_expn_of, is_type_diagnostic_item, iter_input_pats, last_path_segment,
31 match_def_path, match_qpath, match_trait_method, match_type, match_var, method_calls, method_chain_args, paths,
32 remove_blocks, return_ty, single_segment_path, snippet, snippet_with_applicability, snippet_with_macro_callsite,
33 span_lint, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, sugg, walk_ptrs_ty,
34 walk_ptrs_ty_depth, SpanlessEq,
37 declare_clippy_lint! {
38 /// **What it does:** Checks for `.unwrap()` calls on `Option`s and on `Result`s.
40 /// **Why is this bad?** It is better to handle the `None` or `Err` case,
41 /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
42 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
43 /// `Allow` by default.
45 /// `result.unwrap()` will let the thread panic on `Err` values.
46 /// Normally, you want to implement more sophisticated error handling,
47 /// and propagate errors upwards with `?` operator.
49 /// Even if you want to panic on errors, not all `Error`s implement good
50 /// messages on display. Therefore, it may be beneficial to look at the places
51 /// where they may get displayed. Activate this lint to do just that.
53 /// **Known problems:** None.
57 /// # let opt = Some(1);
63 /// opt.expect("more helpful message");
69 /// # let res: Result<usize, ()> = Ok(1);
75 /// res.expect("more helpful message");
79 "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
82 declare_clippy_lint! {
83 /// **What it does:** Checks for `.expect()` calls on `Option`s and `Result`s.
85 /// **Why is this bad?** Usually it is better to handle the `None` or `Err` case.
86 /// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
87 /// this lint is `Allow` by default.
89 /// `result.expect()` will let the thread panic on `Err`
90 /// values. Normally, you want to implement more sophisticated error handling,
91 /// and propagate errors upwards with `?` operator.
93 /// **Known problems:** None.
97 /// # let opt = Some(1);
100 /// opt.expect("one");
103 /// let opt = Some(1);
110 /// # let res: Result<usize, ()> = Ok(1);
113 /// res.expect("one");
117 /// # Ok::<(), ()>(())
121 "using `.expect()` on `Result` or `Option`, which might be better handled"
124 declare_clippy_lint! {
125 /// **What it does:** Checks for methods that should live in a trait
126 /// implementation of a `std` trait (see [llogiq's blog
127 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
128 /// information) instead of an inherent implementation.
130 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
131 /// the code, often with very little cost. Also people seeing a `mul(...)`
133 /// may expect `*` to work equally, so you should have good reason to disappoint
136 /// **Known problems:** None.
142 /// fn add(&self, other: &X) -> X {
148 pub SHOULD_IMPLEMENT_TRAIT,
150 "defining a method that should be implementing a std trait"
153 declare_clippy_lint! {
154 /// **What it does:** Checks for methods with certain name prefixes and which
155 /// doesn't match how self is taken. The actual rules are:
157 /// |Prefix |`self` taken |
158 /// |-------|----------------------|
159 /// |`as_` |`&self` or `&mut self`|
161 /// |`into_`|`self` |
162 /// |`is_` |`&self` or none |
163 /// |`to_` |`&self` |
165 /// **Why is this bad?** Consistency breeds readability. If you follow the
166 /// conventions, your users won't be surprised that they, e.g., need to supply a
167 /// mutable reference to a `as_..` function.
169 /// **Known problems:** None.
175 /// fn as_str(self) -> &'static str {
181 pub WRONG_SELF_CONVENTION,
183 "defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
186 declare_clippy_lint! {
187 /// **What it does:** This is the same as
188 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
190 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
192 /// **Known problems:** Actually *renaming* the function may break clients if
193 /// the function is part of the public interface. In that case, be mindful of
194 /// the stability guarantees you've given your users.
200 /// pub fn as_str(self) -> &'a str {
205 pub WRONG_PUB_SELF_CONVENTION,
207 "defining a public method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
210 declare_clippy_lint! {
211 /// **What it does:** Checks for usage of `ok().expect(..)`.
213 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
214 /// directly to get a better error message.
216 /// **Known problems:** The error type needs to implement `Debug`
220 /// # let x = Ok::<_, ()>(());
223 /// x.ok().expect("why did I do this again?");
226 /// x.expect("why did I do this again?");
230 "using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
233 declare_clippy_lint! {
234 /// **What it does:** Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
235 /// `result.map(_).unwrap_or_else(_)`.
237 /// **Why is this bad?** Readability, these can be written more concisely (resp.) as
238 /// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
240 /// **Known problems:** The order of the arguments is not in execution order
244 /// # let x = Some(1);
247 /// x.map(|a| a + 1).unwrap_or(0);
250 /// x.map_or(0, |a| a + 1);
256 /// # let x: Result<usize, ()> = Ok(1);
257 /// # fn some_function(foo: ()) -> usize { 1 }
260 /// x.map(|a| a + 1).unwrap_or_else(some_function);
263 /// x.map_or_else(some_function, |a| a + 1);
267 "using `.map(f).unwrap_or(a)` or `.map(f).unwrap_or_else(func)`, which are more succinctly expressed as `map_or(a, f)` or `map_or_else(a, f)`"
270 declare_clippy_lint! {
271 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
273 /// **Why is this bad?** Readability, this can be written more concisely as
276 /// **Known problems:** The order of the arguments is not in execution order.
280 /// # let opt = Some(1);
283 /// opt.map_or(None, |a| Some(a + 1));
286 /// opt.and_then(|a| Some(a + 1));
288 pub OPTION_MAP_OR_NONE,
290 "using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
293 declare_clippy_lint! {
294 /// **What it does:** Checks for usage of `_.map_or(None, Some)`.
296 /// **Why is this bad?** Readability, this can be written more concisely as
299 /// **Known problems:** None.
305 /// # let r: Result<u32, &str> = Ok(1);
306 /// assert_eq!(Some(1), r.map_or(None, Some));
311 /// # let r: Result<u32, &str> = Ok(1);
312 /// assert_eq!(Some(1), r.ok());
314 pub RESULT_MAP_OR_INTO_OPTION,
316 "using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
319 declare_clippy_lint! {
320 /// **What it does:** Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
321 /// `_.or_else(|x| Err(y))`.
323 /// **Why is this bad?** Readability, this can be written more concisely as
324 /// `_.map(|x| y)` or `_.map_err(|x| y)`.
326 /// **Known problems:** None
331 /// # fn opt() -> Option<&'static str> { Some("42") }
332 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
333 /// let _ = opt().and_then(|s| Some(s.len()));
334 /// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
335 /// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
338 /// The correct use would be:
341 /// # fn opt() -> Option<&'static str> { Some("42") }
342 /// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
343 /// let _ = opt().map(|s| s.len());
344 /// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
345 /// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
347 pub BIND_INSTEAD_OF_MAP,
349 "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
352 declare_clippy_lint! {
353 /// **What it does:** Checks for usage of `_.filter(_).next()`.
355 /// **Why is this bad?** Readability, this can be written more concisely as
358 /// **Known problems:** None.
362 /// # let vec = vec![1];
363 /// vec.iter().filter(|x| **x == 0).next();
365 /// Could be written as
367 /// # let vec = vec![1];
368 /// vec.iter().find(|x| **x == 0);
372 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
375 declare_clippy_lint! {
376 /// **What it does:** Checks for usage of `_.skip_while(condition).next()`.
378 /// **Why is this bad?** Readability, this can be written more concisely as
379 /// `_.find(!condition)`.
381 /// **Known problems:** None.
385 /// # let vec = vec![1];
386 /// vec.iter().skip_while(|x| **x == 0).next();
388 /// Could be written as
390 /// # let vec = vec![1];
391 /// vec.iter().find(|x| **x != 0);
395 "using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
398 declare_clippy_lint! {
399 /// **What it does:** Checks for usage of `_.map(_).flatten(_)`,
401 /// **Why is this bad?** Readability, this can be written more concisely as a
402 /// single method call using `_.flat_map(_)`
404 /// **Known problems:**
408 /// let vec = vec![vec![1]];
411 /// vec.iter().map(|x| x.iter()).flatten();
414 /// vec.iter().flat_map(|x| x.iter());
418 "using combinations of `flatten` and `map` which can usually be written as a single method call"
421 declare_clippy_lint! {
422 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
423 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
425 /// **Why is this bad?** Readability, this can be written more concisely as a
426 /// single method call.
428 /// **Known problems:** Often requires a condition + Option/Iterator creation
429 /// inside the closure.
433 /// let vec = vec![1];
436 /// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
439 /// vec.iter().filter_map(|x| if *x == 0 {
447 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can usually be written as a single method call"
450 declare_clippy_lint! {
451 /// **What it does:** Checks for usage of `_.filter_map(_).next()`.
453 /// **Why is this bad?** Readability, this can be written more concisely as a
454 /// single method call.
456 /// **Known problems:** None
460 /// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
462 /// Can be written as
465 /// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
469 "using combination of `filter_map` and `next` which can usually be written as a single method call"
472 declare_clippy_lint! {
473 /// **What it does:** Checks for usage of `flat_map(|x| x)`.
475 /// **Why is this bad?** Readability, this can be written more concisely by using `flatten`.
477 /// **Known problems:** None
481 /// # let iter = vec![vec![0]].into_iter();
482 /// iter.flat_map(|x| x);
484 /// Can be written as
486 /// # let iter = vec![vec![0]].into_iter();
489 pub FLAT_MAP_IDENTITY,
491 "call to `flat_map` where `flatten` is sufficient"
494 declare_clippy_lint! {
495 /// **What it does:** Checks for usage of `_.find(_).map(_)`.
497 /// **Why is this bad?** Readability, this can be written more concisely as a
498 /// single method call.
500 /// **Known problems:** Often requires a condition + Option/Iterator creation
501 /// inside the closure.
505 /// (0..3).find(|x| *x == 2).map(|x| x * 2);
507 /// Can be written as
509 /// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
513 "using a combination of `find` and `map` can usually be written as a single method call"
516 declare_clippy_lint! {
517 /// **What it does:** Checks for an iterator search (such as `find()`,
518 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
520 /// **Why is this bad?** Readability, this can be written more concisely as
523 /// **Known problems:** None.
527 /// # let vec = vec![1];
528 /// vec.iter().find(|x| **x == 0).is_some();
530 /// Could be written as
532 /// # let vec = vec![1];
533 /// vec.iter().any(|x| *x == 0);
537 "using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
540 declare_clippy_lint! {
541 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
542 /// if it starts with a given char.
544 /// **Why is this bad?** Readability, this can be written more concisely as
545 /// `_.starts_with(_)`.
547 /// **Known problems:** None.
551 /// let name = "foo";
552 /// if name.chars().next() == Some('_') {};
554 /// Could be written as
556 /// let name = "foo";
557 /// if name.starts_with('_') {};
561 "using `.chars().next()` to check if a string starts with a char"
564 declare_clippy_lint! {
565 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
566 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
567 /// `unwrap_or_default` instead.
569 /// **Why is this bad?** The function will always be called and potentially
570 /// allocate an object acting as the default.
572 /// **Known problems:** If the function has side-effects, not calling it will
573 /// change the semantic of the program, but you shouldn't rely on that anyway.
577 /// # let foo = Some(String::new());
578 /// foo.unwrap_or(String::new());
580 /// this can instead be written:
582 /// # let foo = Some(String::new());
583 /// foo.unwrap_or_else(String::new);
587 /// # let foo = Some(String::new());
588 /// foo.unwrap_or_default();
592 "using any `*or` method with a function call, which suggests `*or_else`"
595 declare_clippy_lint! {
596 /// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
597 /// etc., and suggests to use `unwrap_or_else` instead
599 /// **Why is this bad?** The function will always be called.
601 /// **Known problems:** If the function has side-effects, not calling it will
602 /// change the semantics of the program, but you shouldn't rely on that anyway.
606 /// # let foo = Some(String::new());
607 /// # let err_code = "418";
608 /// # let err_msg = "I'm a teapot";
609 /// foo.expect(&format!("Err {}: {}", err_code, err_msg));
613 /// # let foo = Some(String::new());
614 /// # let err_code = "418";
615 /// # let err_msg = "I'm a teapot";
616 /// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
618 /// this can instead be written:
620 /// # let foo = Some(String::new());
621 /// # let err_code = "418";
622 /// # let err_msg = "I'm a teapot";
623 /// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
627 "using any `expect` method with a function call"
630 declare_clippy_lint! {
631 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
633 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
634 /// generics, not for using the `clone` method on a concrete type.
636 /// **Known problems:** None.
644 "using `clone` on a `Copy` type"
647 declare_clippy_lint! {
648 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
649 /// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
650 /// function syntax instead (e.g., `Rc::clone(foo)`).
652 /// **Why is this bad?** Calling '.clone()' on an Rc, Arc, or Weak
653 /// can obscure the fact that only the pointer is being cloned, not the underlying
658 /// # use std::rc::Rc;
659 /// let x = Rc::new(1);
667 pub CLONE_ON_REF_PTR,
669 "using 'clone' on a ref-counted pointer"
672 declare_clippy_lint! {
673 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
675 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
676 /// cloning the underlying `T`.
678 /// **Known problems:** None.
685 /// let z = y.clone();
686 /// println!("{:p} {:p}", *y, z); // prints out the same pointer
689 pub CLONE_DOUBLE_REF,
691 "using `clone` on `&&T`"
694 declare_clippy_lint! {
695 /// **What it does:** Checks for usage of `.to_string()` on an `&&T` where
696 /// `T` implements `ToString` directly (like `&&str` or `&&String`).
698 /// **Why is this bad?** This bypasses the specialized implementation of
699 /// `ToString` and instead goes through the more expensive string formatting
702 /// **Known problems:** None.
706 /// // Generic implementation for `T: Display` is used (slow)
707 /// ["foo", "bar"].iter().map(|s| s.to_string());
709 /// // OK, the specialized impl is used
710 /// ["foo", "bar"].iter().map(|&s| s.to_string());
712 pub INEFFICIENT_TO_STRING,
714 "using `to_string` on `&&T` where `T: ToString`"
717 declare_clippy_lint! {
718 /// **What it does:** Checks for `new` not returning a type that contains `Self`.
720 /// **Why is this bad?** As a convention, `new` methods are used to make a new
721 /// instance of a type.
723 /// **Known problems:** None.
728 /// # struct NotAFoo;
730 /// fn new() -> NotAFoo {
738 /// # struct FooError;
740 /// // Good. Return type contains `Self`
741 /// fn new() -> Result<Foo, FooError> {
751 /// // Bad. The type name must contain `Self`.
752 /// fn new() -> Bar {
759 "not returning type containing `Self` in a `new` method"
762 declare_clippy_lint! {
763 /// **What it does:** Checks for string methods that receive a single-character
764 /// `str` as an argument, e.g., `_.split("x")`.
766 /// **Why is this bad?** Performing these methods using a `char` is faster than
769 /// **Known problems:** Does not catch multi-byte unicode characters.
778 pub SINGLE_CHAR_PATTERN,
780 "using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
783 declare_clippy_lint! {
784 /// **What it does:** Checks for getting the inner pointer of a temporary
787 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
788 /// as the `CString` is alive.
790 /// **Known problems:** None.
794 /// # use std::ffi::CString;
795 /// # fn call_some_ffi_func(_: *const i8) {}
797 /// let c_str = CString::new("foo").unwrap().as_ptr();
799 /// call_some_ffi_func(c_str);
802 /// Here `c_str` point to a freed address. The correct use would be:
804 /// # use std::ffi::CString;
805 /// # fn call_some_ffi_func(_: *const i8) {}
807 /// let c_str = CString::new("foo").unwrap();
809 /// call_some_ffi_func(c_str.as_ptr());
812 pub TEMPORARY_CSTRING_AS_PTR,
814 "getting the inner pointer of a temporary `CString`"
817 declare_clippy_lint! {
818 /// **What it does:** Checks for calling `.step_by(0)` on iterators which panics.
820 /// **Why is this bad?** This very much looks like an oversight. Use `panic!()` instead if you
821 /// actually intend to panic.
823 /// **Known problems:** None.
826 /// ```rust,should_panic
827 /// for x in (0..100).step_by(0) {
831 pub ITERATOR_STEP_BY_ZERO,
833 "using `Iterator::step_by(0)`, which will panic at runtime"
836 declare_clippy_lint! {
837 /// **What it does:** Checks for the use of `iter.nth(0)`.
839 /// **Why is this bad?** `iter.next()` is equivalent to
840 /// `iter.nth(0)`, as they both consume the next element,
841 /// but is more readable.
843 /// **Known problems:** None.
848 /// # use std::collections::HashSet;
850 /// # let mut s = HashSet::new();
852 /// let x = s.iter().nth(0);
855 /// # let mut s = HashSet::new();
857 /// let x = s.iter().next();
861 "replace `iter.nth(0)` with `iter.next()`"
864 declare_clippy_lint! {
865 /// **What it does:** Checks for use of `.iter().nth()` (and the related
866 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
868 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
871 /// **Known problems:** None.
875 /// let some_vec = vec![0, 1, 2, 3];
876 /// let bad_vec = some_vec.iter().nth(3);
877 /// let bad_slice = &some_vec[..].iter().nth(3);
879 /// The correct use would be:
881 /// let some_vec = vec![0, 1, 2, 3];
882 /// let bad_vec = some_vec.get(3);
883 /// let bad_slice = &some_vec[..].get(3);
887 "using `.iter().nth()` on a standard library type with O(1) element access"
890 declare_clippy_lint! {
891 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
893 /// **Why is this bad?** `.nth(x)` is cleaner
895 /// **Known problems:** None.
899 /// let some_vec = vec![0, 1, 2, 3];
900 /// let bad_vec = some_vec.iter().skip(3).next();
901 /// let bad_slice = &some_vec[..].iter().skip(3).next();
903 /// The correct use would be:
905 /// let some_vec = vec![0, 1, 2, 3];
906 /// let bad_vec = some_vec.iter().nth(3);
907 /// let bad_slice = &some_vec[..].iter().nth(3);
911 "using `.skip(x).next()` on an iterator"
914 declare_clippy_lint! {
915 /// **What it does:** Checks for use of `.get().unwrap()` (or
916 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
918 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
921 /// **Known problems:** Not a replacement for error handling: Using either
922 /// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
923 /// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
924 /// temporary placeholder for dealing with the `Option` type, then this does
925 /// not mitigate the need for error handling. If there is a chance that `.get()`
926 /// will be `None` in your program, then it is advisable that the `None` case
927 /// is handled in a future refactor instead of using `.unwrap()` or the Index
932 /// let mut some_vec = vec![0, 1, 2, 3];
933 /// let last = some_vec.get(3).unwrap();
934 /// *some_vec.get_mut(0).unwrap() = 1;
936 /// The correct use would be:
938 /// let mut some_vec = vec![0, 1, 2, 3];
939 /// let last = some_vec[3];
944 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
947 declare_clippy_lint! {
948 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
949 /// `&str` or `String`.
951 /// **Why is this bad?** `.push_str(s)` is clearer
953 /// **Known problems:** None.
958 /// let def = String::from("def");
959 /// let mut s = String::new();
960 /// s.extend(abc.chars());
961 /// s.extend(def.chars());
963 /// The correct use would be:
966 /// let def = String::from("def");
967 /// let mut s = String::new();
969 /// s.push_str(&def);
971 pub STRING_EXTEND_CHARS,
973 "using `x.extend(s.chars())` where s is a `&str` or `String`"
976 declare_clippy_lint! {
977 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
980 /// **Why is this bad?** `.to_vec()` is clearer
982 /// **Known problems:** None.
986 /// let s = [1, 2, 3, 4, 5];
987 /// let s2: Vec<isize> = s[..].iter().cloned().collect();
989 /// The better use would be:
991 /// let s = [1, 2, 3, 4, 5];
992 /// let s2: Vec<isize> = s.to_vec();
994 pub ITER_CLONED_COLLECT,
996 "using `.cloned().collect()` on slice to create a `Vec`"
999 declare_clippy_lint! {
1000 /// **What it does:** Checks for usage of `_.chars().last()` or
1001 /// `_.chars().next_back()` on a `str` to check if it ends with a given char.
1003 /// **Why is this bad?** Readability, this can be written more concisely as
1004 /// `_.ends_with(_)`.
1006 /// **Known problems:** None.
1010 /// # let name = "_";
1013 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
1016 /// name.ends_with('_') || name.ends_with('-');
1020 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
1023 declare_clippy_lint! {
1024 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
1025 /// types before and after the call are the same.
1027 /// **Why is this bad?** The call is unnecessary.
1029 /// **Known problems:** None.
1033 /// # fn do_stuff(x: &[i32]) {}
1034 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1035 /// do_stuff(x.as_ref());
1037 /// The correct use would be:
1039 /// # fn do_stuff(x: &[i32]) {}
1040 /// let x: &[i32] = &[1, 2, 3, 4, 5];
1045 "using `as_ref` where the types before and after the call are the same"
1048 declare_clippy_lint! {
1049 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
1050 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
1051 /// `sum` or `product`.
1053 /// **Why is this bad?** Readability.
1055 /// **Known problems:** False positive in pattern guards. Will be resolved once
1056 /// non-lexical lifetimes are stable.
1060 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
1062 /// This could be written as:
1064 /// let _ = (0..3).any(|x| x > 2);
1066 pub UNNECESSARY_FOLD,
1068 "using `fold` when a more succinct alternative exists"
1071 declare_clippy_lint! {
1072 /// **What it does:** Checks for `filter_map` calls which could be replaced by `filter` or `map`.
1073 /// More specifically it checks if the closure provided is only performing one of the
1074 /// filter or map operations and suggests the appropriate option.
1076 /// **Why is this bad?** Complexity. The intent is also clearer if only a single
1077 /// operation is being performed.
1079 /// **Known problems:** None
1083 /// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
1085 /// // As there is no transformation of the argument this could be written as:
1086 /// let _ = (0..3).filter(|&x| x > 2);
1090 /// let _ = (0..4).filter_map(|x| Some(x + 1));
1092 /// // As there is no conditional check on the argument this could be written as:
1093 /// let _ = (0..4).map(|x| x + 1);
1095 pub UNNECESSARY_FILTER_MAP,
1097 "using `filter_map` when a more succinct alternative exists"
1100 declare_clippy_lint! {
1101 /// **What it does:** Checks for `into_iter` calls on references which should be replaced by `iter`
1104 /// **Why is this bad?** Readability. Calling `into_iter` on a reference will not move out its
1105 /// content into the resulting iterator, which is confusing. It is better just call `iter` or
1106 /// `iter_mut` directly.
1108 /// **Known problems:** None
1114 /// let _ = (&vec![3, 4, 5]).into_iter();
1117 /// let _ = (&vec![3, 4, 5]).iter();
1119 pub INTO_ITER_ON_REF,
1121 "using `.into_iter()` on a reference"
1124 declare_clippy_lint! {
1125 /// **What it does:** Checks for calls to `map` followed by a `count`.
1127 /// **Why is this bad?** It looks suspicious. Maybe `map` was confused with `filter`.
1128 /// If the `map` call is intentional, this should be rewritten. Or, if you intend to
1129 /// drive the iterator to completion, you can just use `for_each` instead.
1131 /// **Known problems:** None
1136 /// let _ = (0..3).map(|x| x + 2).count();
1140 "suspicious usage of map"
1143 declare_clippy_lint! {
1144 /// **What it does:** Checks for `MaybeUninit::uninit().assume_init()`.
1146 /// **Why is this bad?** For most types, this is undefined behavior.
1148 /// **Known problems:** For now, we accept empty tuples and tuples / arrays
1149 /// of `MaybeUninit`. There may be other types that allow uninitialized
1150 /// data, but those are not yet rigorously defined.
1155 /// // Beware the UB
1156 /// use std::mem::MaybeUninit;
1158 /// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
1161 /// Note that the following is OK:
1164 /// use std::mem::MaybeUninit;
1166 /// let _: [MaybeUninit<bool>; 5] = unsafe {
1167 /// MaybeUninit::uninit().assume_init()
1170 pub UNINIT_ASSUMED_INIT,
1172 "`MaybeUninit::uninit().assume_init()`"
1175 declare_clippy_lint! {
1176 /// **What it does:** Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
1178 /// **Why is this bad?** These can be written simply with `saturating_add/sub` methods.
1183 /// # let y: u32 = 0;
1184 /// # let x: u32 = 100;
1185 /// let add = x.checked_add(y).unwrap_or(u32::MAX);
1186 /// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
1189 /// can be written using dedicated methods for saturating addition/subtraction as:
1192 /// # let y: u32 = 0;
1193 /// # let x: u32 = 100;
1194 /// let add = x.saturating_add(y);
1195 /// let sub = x.saturating_sub(y);
1197 pub MANUAL_SATURATING_ARITHMETIC,
1199 "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
1202 declare_clippy_lint! {
1203 /// **What it does:** Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
1204 /// zero-sized types
1206 /// **Why is this bad?** This is a no-op, and likely unintended
1208 /// **Known problems:** None
1212 /// unsafe { (&() as *const ()).offset(1) };
1216 "Check for offset calculations on raw pointers to zero-sized types"
1219 declare_clippy_lint! {
1220 /// **What it does:** Checks for `FileType::is_file()`.
1222 /// **Why is this bad?** When people testing a file type with `FileType::is_file`
1223 /// they are testing whether a path is something they can get bytes from. But
1224 /// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
1225 /// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
1231 /// let metadata = std::fs::metadata("foo.txt")?;
1232 /// let filetype = metadata.file_type();
1234 /// if filetype.is_file() {
1237 /// # Ok::<_, std::io::Error>(())
1241 /// should be written as:
1245 /// let metadata = std::fs::metadata("foo.txt")?;
1246 /// let filetype = metadata.file_type();
1248 /// if !filetype.is_dir() {
1251 /// # Ok::<_, std::io::Error>(())
1254 pub FILETYPE_IS_FILE,
1256 "`FileType::is_file` is not recommended to test for readable file type"
1259 declare_clippy_lint! {
1260 /// **What it does:** Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
1262 /// **Why is this bad?** Readability, this can be written more concisely as a
1263 /// single method call.
1265 /// **Known problems:** None.
1269 /// # let opt = Some("".to_string());
1270 /// opt.as_ref().map(String::as_str)
1273 /// Can be written as
1275 /// # let opt = Some("".to_string());
1279 pub OPTION_AS_REF_DEREF,
1281 "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
1284 declare_clippy_lint! {
1285 /// **What it does:** Checks for usage of `iter().next()` on a Slice or an Array
1287 /// **Why is this bad?** These can be shortened into `.get()`
1289 /// **Known problems:** None.
1293 /// # let a = [1, 2, 3];
1294 /// # let b = vec![1, 2, 3];
1295 /// a[2..].iter().next();
1296 /// b.iter().next();
1298 /// should be written as:
1300 /// # let a = [1, 2, 3];
1301 /// # let b = vec![1, 2, 3];
1305 pub ITER_NEXT_SLICE,
1307 "using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
1310 declare_lint_pass!(Methods => [
1313 SHOULD_IMPLEMENT_TRAIT,
1314 WRONG_SELF_CONVENTION,
1315 WRONG_PUB_SELF_CONVENTION,
1318 RESULT_MAP_OR_INTO_OPTION,
1320 BIND_INSTEAD_OF_MAP,
1328 INEFFICIENT_TO_STRING,
1330 SINGLE_CHAR_PATTERN,
1332 TEMPORARY_CSTRING_AS_PTR,
1340 ITERATOR_STEP_BY_ZERO,
1346 STRING_EXTEND_CHARS,
1347 ITER_CLONED_COLLECT,
1350 UNNECESSARY_FILTER_MAP,
1353 UNINIT_ASSUMED_INIT,
1354 MANUAL_SATURATING_ARITHMETIC,
1357 OPTION_AS_REF_DEREF,
1360 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
1361 #[allow(clippy::too_many_lines)]
1362 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
1363 if in_macro(expr.span) {
1367 let (method_names, arg_lists, method_spans) = method_calls(expr, 2);
1368 let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
1369 let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
1371 match method_names.as_slice() {
1372 ["unwrap", "get"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
1373 ["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
1374 ["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
1375 ["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
1376 ["expect", ..] => lint_expect(cx, expr, arg_lists[0]),
1377 ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
1378 ["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
1379 ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
1380 ["and_then", ..] => {
1381 bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
1382 bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
1384 ["or_else", ..] => {
1385 bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]);
1387 ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
1388 ["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
1389 ["next", "iter"] => lint_iter_next(cx, expr, arg_lists[1]),
1390 ["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
1391 ["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
1392 ["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
1393 ["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
1394 ["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1395 ["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
1396 ["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0], method_spans[0]),
1397 ["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
1398 ["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
1399 ["is_some", "position"] => {
1400 lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
1402 ["is_some", "rposition"] => {
1403 lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
1405 ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
1406 ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
1407 lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
1409 ["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
1410 ["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
1411 ["nth", ..] => lint_iter_nth_zero(cx, expr, arg_lists[0]),
1412 ["step_by", ..] => lint_step_by(cx, expr, arg_lists[0]),
1413 ["next", "skip"] => lint_iter_skip_next(cx, expr),
1414 ["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
1415 ["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
1416 ["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
1417 ["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0], method_spans[0]),
1418 ["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
1419 ["count", "map"] => lint_suspicious_map(cx, expr),
1420 ["assume_init"] => lint_maybe_uninit(cx, &arg_lists[0][0], expr),
1421 ["unwrap_or", arith @ "checked_add"]
1422 | ["unwrap_or", arith @ "checked_sub"]
1423 | ["unwrap_or", arith @ "checked_mul"] => {
1424 manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
1426 ["add"] | ["offset"] | ["sub"] | ["wrapping_offset"] | ["wrapping_add"] | ["wrapping_sub"] => {
1427 check_pointer_offset(cx, expr, arg_lists[0])
1429 ["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
1430 ["map", "as_ref"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false),
1431 ["map", "as_mut"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true),
1436 hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
1437 lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1438 lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
1440 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
1441 if args.len() == 1 && method_call.ident.name == sym!(clone) {
1442 lint_clone_on_copy(cx, expr, &args[0], self_ty);
1443 lint_clone_on_ref_ptr(cx, expr, &args[0]);
1445 if args.len() == 1 && method_call.ident.name == sym!(to_string) {
1446 inefficient_to_string::lint(cx, expr, &args[0], self_ty);
1449 match self_ty.kind {
1450 ty::Ref(_, ty, _) if ty.kind == ty::Str => {
1451 for &(method, pos) in &PATTERN_METHODS {
1452 if method_call.ident.name.as_str() == method && args.len() > pos {
1453 lint_single_char_pattern(cx, expr, &args[pos]);
1457 ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
1458 lint_into_iter(cx, expr, self_ty, *method_span);
1463 hir::ExprKind::Binary(op, ref lhs, ref rhs)
1464 if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne =>
1466 let mut info = BinaryExprInfo {
1470 eq: op.node == hir::BinOpKind::Eq,
1472 lint_binary_expr_with_method_call(cx, &mut info);
1478 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
1479 if in_external_macro(cx.sess(), impl_item.span) {
1482 let name = impl_item.ident.name.as_str();
1483 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id);
1484 let item = cx.tcx.hir().expect_item(parent);
1485 let def_id = cx.tcx.hir().local_def_id(item.hir_id);
1486 let self_ty = cx.tcx.type_of(def_id);
1488 if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
1489 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
1490 if let hir::ItemKind::Impl{ of_trait: None, .. } = item.kind;
1492 let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
1493 let method_sig = cx.tcx.fn_sig(method_def_id);
1494 let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
1496 let first_arg_ty = &method_sig.inputs().iter().next();
1498 // check conventions w.r.t. conversion method names and predicates
1499 if let Some(first_arg_ty) = first_arg_ty;
1502 if cx.access_levels.is_exported(impl_item.hir_id) {
1503 // check missing trait implementations
1504 for &(method_name, n_args, fn_header, self_kind, out_type, trait_name) in &TRAIT_METHODS {
1505 if name == method_name &&
1506 sig.decl.inputs.len() == n_args &&
1507 out_type.matches(cx, &sig.decl.output) &&
1508 self_kind.matches(cx, self_ty, first_arg_ty) &&
1509 fn_header_equals(*fn_header, sig.header) {
1510 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, impl_item.span, &format!(
1511 "defining a method called `{}` on this type; consider implementing \
1512 the `{}` trait or choosing a less ambiguous name", name, trait_name));
1517 if let Some((ref conv, self_kinds)) = &CONVENTIONS
1519 .find(|(ref conv, _)| conv.check(&name))
1521 if !self_kinds.iter().any(|k| k.matches(cx, self_ty, first_arg_ty)) {
1522 let lint = if item.vis.node.is_pub() {
1523 WRONG_PUB_SELF_CONVENTION
1525 WRONG_SELF_CONVENTION
1532 &format!("methods called `{}` usually take {}; consider choosing a less ambiguous name",
1536 .map(|k| k.description())
1537 .collect::<Vec<_>>()
1546 if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
1547 let ret_ty = return_ty(cx, impl_item.hir_id);
1549 let contains_self_ty = |ty: Ty<'tcx>| {
1550 ty.walk().any(|inner| match inner.unpack() {
1551 GenericArgKind::Type(inner_ty) => TyS::same_type(self_ty, inner_ty),
1553 GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
1557 // walk the return type and check for Self (this does not check associated types)
1558 if contains_self_ty(ret_ty) {
1562 // if return type is impl trait, check the associated types
1563 if let ty::Opaque(def_id, _) = ret_ty.kind {
1564 // one of the associated types must be Self
1565 for predicate in cx.tcx.predicates_of(def_id).predicates {
1566 if let ty::PredicateKind::Projection(poly_projection_predicate) = predicate.0.kind() {
1567 let binder = poly_projection_predicate.ty();
1568 let associated_type = binder.skip_binder();
1570 // walk the associated type and check for Self
1571 if contains_self_ty(associated_type) {
1578 if name == "new" && !TyS::same_type(ret_ty, self_ty) {
1583 "methods called `new` usually return `Self`",
1590 /// Checks for the `OR_FUN_CALL` lint.
1591 #[allow(clippy::too_many_lines)]
1592 fn lint_or_fun_call<'a, 'tcx>(
1593 cx: &LateContext<'a, 'tcx>,
1594 expr: &hir::Expr<'_>,
1597 args: &'tcx [hir::Expr<'_>],
1599 // Searches an expression for method calls or function calls that aren't ctors
1600 struct FunCallFinder<'a, 'tcx> {
1601 cx: &'a LateContext<'a, 'tcx>,
1605 impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
1606 type Map = Map<'tcx>;
1608 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
1609 let call_found = match &expr.kind {
1610 // ignore enum and struct constructors
1611 hir::ExprKind::Call(..) => !is_ctor_or_promotable_const_function(self.cx, expr),
1612 hir::ExprKind::MethodCall(..) => true,
1621 intravisit::walk_expr(self, expr);
1625 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1626 intravisit::NestedVisitorMap::None
1630 /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
1631 fn check_unwrap_or_default(
1632 cx: &LateContext<'_, '_>,
1634 fun: &hir::Expr<'_>,
1635 self_expr: &hir::Expr<'_>,
1636 arg: &hir::Expr<'_>,
1642 if name == "unwrap_or";
1643 if let hir::ExprKind::Path(ref qpath) = fun.kind;
1644 let path = &*last_path_segment(qpath).ident.as_str();
1645 if ["default", "new"].contains(&path);
1646 let arg_ty = cx.tables.expr_ty(arg);
1647 if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
1648 if implements_trait(cx, arg_ty, default_trait_id, &[]);
1651 let mut applicability = Applicability::MachineApplicable;
1656 &format!("use of `{}` followed by a call to `{}`", name, path),
1659 "{}.unwrap_or_default()",
1660 snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
1672 /// Checks for `*or(foo())`.
1673 #[allow(clippy::too_many_arguments)]
1674 fn check_general_case<'a, 'tcx>(
1675 cx: &LateContext<'a, 'tcx>,
1679 self_expr: &hir::Expr<'_>,
1680 arg: &'tcx hir::Expr<'_>,
1684 if let hir::ExprKind::MethodCall(ref path, _, ref args) = &arg.kind {
1685 if path.ident.as_str() == "len" {
1686 let ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
1689 ty::Slice(_) | ty::Array(_, _) => return,
1693 if match_type(cx, ty, &paths::VEC) {
1699 // (path, fn_has_argument, methods, suffix)
1700 let know_types: &[(&[_], _, &[_], _)] = &[
1701 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
1702 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
1703 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
1704 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
1708 if know_types.iter().any(|k| k.2.contains(&name));
1710 let mut finder = FunCallFinder { cx: &cx, found: false };
1711 if { finder.visit_expr(&arg); finder.found };
1712 if !contains_return(&arg);
1714 let self_ty = cx.tables.expr_ty(self_expr);
1716 if let Some(&(_, fn_has_arguments, poss, suffix)) =
1717 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0));
1719 if poss.contains(&name);
1722 let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
1723 (true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1724 (false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
1725 (false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
1727 let span_replace_word = method_span.with_hi(span.hi());
1732 &format!("use of `{}` followed by a function call", name),
1734 format!("{}_{}({})", name, suffix, sugg),
1735 Applicability::HasPlaceholders,
1741 if args.len() == 2 {
1742 match args[1].kind {
1743 hir::ExprKind::Call(ref fun, ref or_args) => {
1744 let or_has_args = !or_args.is_empty();
1745 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
1758 hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
1765 !or_args.is_empty(),
1773 /// Checks for the `EXPECT_FUN_CALL` lint.
1774 #[allow(clippy::too_many_lines)]
1775 fn lint_expect_fun_call(
1776 cx: &LateContext<'_, '_>,
1777 expr: &hir::Expr<'_>,
1780 args: &[hir::Expr<'_>],
1782 // Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
1784 fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
1785 let mut arg_root = arg;
1787 arg_root = match &arg_root.kind {
1788 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => expr,
1789 hir::ExprKind::MethodCall(method_name, _, call_args) => {
1790 if call_args.len() == 1
1791 && (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
1793 let arg_type = cx.tables.expr_ty(&call_args[0]);
1794 let base_type = walk_ptrs_ty(arg_type);
1795 base_type.kind == ty::Str || is_type_diagnostic_item(cx, base_type, sym!(string_type))
1809 // Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
1810 // converted to string.
1811 fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr<'_>) -> bool {
1812 let arg_ty = cx.tables.expr_ty(arg);
1813 if is_type_diagnostic_item(cx, arg_ty, sym!(string_type)) {
1816 if let ty::Ref(_, ty, ..) = arg_ty.kind {
1817 if ty.kind == ty::Str && can_be_static_str(cx, arg) {
1824 // Check if an expression could have type `&'static str`, knowing that it
1825 // has type `&str` for some lifetime.
1826 fn can_be_static_str(cx: &LateContext<'_, '_>, arg: &hir::Expr<'_>) -> bool {
1828 hir::ExprKind::Lit(_) => true,
1829 hir::ExprKind::Call(fun, _) => {
1830 if let hir::ExprKind::Path(ref p) = fun.kind {
1831 match cx.tables.qpath_res(p, fun.hir_id) {
1832 hir::def::Res::Def(hir::def::DefKind::Fn, def_id)
1833 | hir::def::Res::Def(hir::def::DefKind::AssocFn, def_id) => matches!(
1834 cx.tcx.fn_sig(def_id).output().skip_binder().kind,
1835 ty::Ref(ty::ReStatic, ..)
1843 hir::ExprKind::MethodCall(..) => cx.tables.type_dependent_def_id(arg.hir_id).map_or(false, |method_id| {
1845 cx.tcx.fn_sig(method_id).output().skip_binder().kind,
1846 ty::Ref(ty::ReStatic, ..)
1849 hir::ExprKind::Path(ref p) => match cx.tables.qpath_res(p, arg.hir_id) {
1850 hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static, _) => true,
1857 fn generate_format_arg_snippet(
1858 cx: &LateContext<'_, '_>,
1860 applicability: &mut Applicability,
1863 if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref format_arg) = a.kind;
1864 if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.kind;
1865 if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.kind;
1870 .map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
1878 fn is_call(node: &hir::ExprKind<'_>) -> bool {
1880 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => {
1883 hir::ExprKind::Call(..)
1884 | hir::ExprKind::MethodCall(..)
1885 // These variants are debatable or require further examination
1886 | hir::ExprKind::Match(..)
1887 | hir::ExprKind::Block{ .. } => true,
1892 if args.len() != 2 || name != "expect" || !is_call(&args[1].kind) {
1896 let receiver_type = cx.tables.expr_ty_adjusted(&args[0]);
1897 let closure_args = if is_type_diagnostic_item(cx, receiver_type, sym!(option_type)) {
1899 } else if is_type_diagnostic_item(cx, receiver_type, sym!(result_type)) {
1905 let arg_root = get_arg_root(cx, &args[1]);
1907 let span_replace_word = method_span.with_hi(expr.span.hi());
1909 let mut applicability = Applicability::MachineApplicable;
1911 //Special handling for `format!` as arg_root
1913 if let hir::ExprKind::Block(block, None) = &arg_root.kind;
1914 if block.stmts.len() == 1;
1915 if let hir::StmtKind::Local(local) = &block.stmts[0].kind;
1916 if let Some(arg_root) = &local.init;
1917 if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.kind;
1918 if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1;
1919 if let hir::ExprKind::Call(_, format_args) = &inner_args[0].kind;
1921 let fmt_spec = &format_args[0];
1922 let fmt_args = &format_args[1];
1924 let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
1926 args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
1928 let sugg = args.join(", ");
1934 &format!("use of `{}` followed by a function call", name),
1936 format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
1944 let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
1945 if requires_to_string(cx, arg_root) {
1946 arg_root_snippet.to_mut().push_str(".to_string()");
1953 &format!("use of `{}` followed by a function call", name),
1955 format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
1960 /// Checks for the `CLONE_ON_COPY` lint.
1961 fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
1962 let ty = cx.tables.expr_ty(expr);
1963 if let ty::Ref(_, inner, _) = arg_ty.kind {
1964 if let ty::Ref(_, innermost, _) = inner.kind {
1969 "using `clone` on a double-reference; \
1970 this will copy the reference instead of cloning the inner type",
1972 if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
1973 let mut ty = innermost;
1975 while let ty::Ref(_, inner, _) = ty.kind {
1979 let refs: String = iter::repeat('&').take(n + 1).collect();
1980 let derefs: String = iter::repeat('*').take(n).collect();
1981 let explicit = format!("<{}{}>::clone({})", refs, ty, snip);
1982 diag.span_suggestion(
1984 "try dereferencing it",
1985 format!("{}({}{}).clone()", refs, derefs, snip.deref()),
1986 Applicability::MaybeIncorrect,
1988 diag.span_suggestion(
1990 "or try being explicit if you are sure, that you want to clone a reference",
1992 Applicability::MaybeIncorrect,
1997 return; // don't report clone_on_copy
2001 if is_copy(cx, ty) {
2003 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
2004 let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
2005 match &cx.tcx.hir().get(parent) {
2006 hir::Node::Expr(parent) => match parent.kind {
2007 // &*x is a nop, &x.clone() is not
2008 hir::ExprKind::AddrOf(..) => return,
2009 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
2010 hir::ExprKind::MethodCall(_, _, parent_args) if expr.hir_id == parent_args[0].hir_id => return,
2014 hir::Node::Stmt(stmt) => {
2015 if let hir::StmtKind::Local(ref loc) = stmt.kind {
2016 if let hir::PatKind::Ref(..) = loc.pat.kind {
2017 // let ref y = *x borrows x, let ref y = x.clone() does not
2025 // x.clone() might have dereferenced x, possibly through Deref impls
2026 if cx.tables.expr_ty(arg) == ty {
2027 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
2029 let deref_count = cx
2031 .expr_adjustments(arg)
2034 if let ty::adjustment::Adjust::Deref(_) = adj.kind {
2041 let derefs: String = iter::repeat('*').take(deref_count).collect();
2042 snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
2047 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |diag| {
2048 if let Some((text, snip)) = snip {
2049 diag.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
2055 fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
2056 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
2058 if let ty::Adt(_, subst) = obj_ty.kind {
2059 let caller_type = if is_type_diagnostic_item(cx, obj_ty, sym::Rc) {
2061 } else if is_type_diagnostic_item(cx, obj_ty, sym::Arc) {
2063 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
2073 "using `.clone()` on a ref-counted pointer",
2076 "{}::<{}>::clone(&{})",
2079 snippet(cx, arg.span, "_")
2081 Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
2086 fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2088 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
2089 let target = &arglists[0][0];
2090 let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
2091 let ref_str = if self_ty.kind == ty::Str {
2093 } else if is_type_diagnostic_item(cx, self_ty, sym!(string_type)) {
2099 let mut applicability = Applicability::MachineApplicable;
2102 STRING_EXTEND_CHARS,
2104 "calling `.extend(_.chars())`",
2107 "{}.push_str({}{})",
2108 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
2110 snippet_with_applicability(cx, target.span, "_", &mut applicability)
2117 fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
2118 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
2119 if is_type_diagnostic_item(cx, obj_ty, sym!(string_type)) {
2120 lint_string_extend(cx, expr, args);
2124 fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, source: &hir::Expr<'_>, unwrap: &hir::Expr<'_>) {
2126 let source_type = cx.tables.expr_ty(source);
2127 if let ty::Adt(def, substs) = source_type.kind;
2128 if cx.tcx.is_diagnostic_item(sym!(result_type), def.did);
2129 if match_type(cx, substs.type_at(0), &paths::CSTRING);
2133 TEMPORARY_CSTRING_AS_PTR,
2135 "you are getting the inner pointer of a temporary `CString`",
2137 diag.note("that pointer will be invalid outside this expression");
2138 diag.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
2144 fn lint_iter_cloned_collect<'a, 'tcx>(
2145 cx: &LateContext<'a, 'tcx>,
2146 expr: &hir::Expr<'_>,
2147 iter_args: &'tcx [hir::Expr<'_>],
2150 if is_type_diagnostic_item(cx, cx.tables.expr_ty(expr), sym!(vec_type));
2151 if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0]));
2152 if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite());
2157 ITER_CLONED_COLLECT,
2159 "called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
2162 ".to_vec()".to_string(),
2163 Applicability::MachineApplicable,
2169 fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, fold_args: &[hir::Expr<'_>], fold_span: Span) {
2170 fn check_fold_with_op(
2171 cx: &LateContext<'_, '_>,
2172 expr: &hir::Expr<'_>,
2173 fold_args: &[hir::Expr<'_>],
2176 replacement_method_name: &str,
2177 replacement_has_args: bool,
2180 // Extract the body of the closure passed to fold
2181 if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].kind;
2182 let closure_body = cx.tcx.hir().body(body_id);
2183 let closure_expr = remove_blocks(&closure_body.value);
2185 // Check if the closure body is of the form `acc <op> some_expr(x)`
2186 if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.kind;
2187 if bin_op.node == op;
2189 // Extract the names of the two arguments to the closure
2190 if let Some(first_arg_ident) = get_arg_name(&closure_body.params[0].pat);
2191 if let Some(second_arg_ident) = get_arg_name(&closure_body.params[1].pat);
2193 if match_var(&*left_expr, first_arg_ident);
2194 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
2197 let mut applicability = Applicability::MachineApplicable;
2198 let sugg = if replacement_has_args {
2200 "{replacement}(|{s}| {r})",
2201 replacement = replacement_method_name,
2202 s = second_arg_ident,
2203 r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
2208 replacement = replacement_method_name,
2215 fold_span.with_hi(expr.span.hi()),
2216 // TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
2217 "this `.fold` can be written more succinctly using another method",
2226 // Check that this is a call to Iterator::fold rather than just some function called fold
2227 if !match_trait_method(cx, expr, &paths::ITERATOR) {
2232 fold_args.len() == 3,
2233 "Expected fold_args to have three entries - the receiver, the initial value and the closure"
2236 // Check if the first argument to .fold is a suitable literal
2237 if let hir::ExprKind::Lit(ref lit) = fold_args[1].kind {
2239 ast::LitKind::Bool(false) => {
2240 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Or, "any", true)
2242 ast::LitKind::Bool(true) => {
2243 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::And, "all", true)
2245 ast::LitKind::Int(0, _) => {
2246 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Add, "sum", false)
2248 ast::LitKind::Int(1, _) => {
2249 check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Mul, "product", false)
2256 fn lint_step_by<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>, args: &'tcx [hir::Expr<'_>]) {
2257 if match_trait_method(cx, expr, &paths::ITERATOR) {
2258 if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
2261 ITERATOR_STEP_BY_ZERO,
2263 "Iterator::step_by(0) will panic at runtime",
2269 fn lint_iter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>, iter_args: &'tcx [hir::Expr<'_>]) {
2270 let caller_expr = &iter_args[0];
2272 // Skip lint if the `iter().next()` expression is a for loop argument,
2273 // since it is already covered by `&loops::ITER_NEXT_LOOP`
2274 let mut parent_expr_opt = get_parent_expr(cx, expr);
2275 while let Some(parent_expr) = parent_expr_opt {
2276 if higher::for_loop(parent_expr).is_some() {
2279 parent_expr_opt = get_parent_expr(cx, parent_expr);
2282 if derefs_to_slice(cx, caller_expr, cx.tables.expr_ty(caller_expr)).is_some() {
2283 // caller is a Slice
2285 if let hir::ExprKind::Index(ref caller_var, ref index_expr) = &caller_expr.kind;
2286 if let Some(higher::Range { start: Some(start_expr), end: None, limits: ast::RangeLimits::HalfOpen })
2287 = higher::range(cx, index_expr);
2288 if let hir::ExprKind::Lit(ref start_lit) = &start_expr.kind;
2289 if let ast::LitKind::Int(start_idx, _) = start_lit.node;
2291 let mut applicability = Applicability::MachineApplicable;
2296 "Using `.iter().next()` on a Slice without end index.",
2298 format!("{}.get({})", snippet_with_applicability(cx, caller_var.span, "..", &mut applicability), start_idx),
2303 } else if is_type_diagnostic_item(cx, cx.tables.expr_ty(caller_expr), sym!(vec_type))
2304 || matches!(&walk_ptrs_ty(cx.tables.expr_ty(caller_expr)).kind, ty::Array(_, _))
2306 // caller is a Vec or an Array
2307 let mut applicability = Applicability::MachineApplicable;
2312 "Using `.iter().next()` on an array",
2316 snippet_with_applicability(cx, caller_expr.span, "..", &mut applicability)
2323 fn lint_iter_nth<'a, 'tcx>(
2324 cx: &LateContext<'a, 'tcx>,
2325 expr: &hir::Expr<'_>,
2326 nth_and_iter_args: &[&'tcx [hir::Expr<'tcx>]],
2329 let iter_args = nth_and_iter_args[1];
2330 let mut_str = if is_mut { "_mut" } else { "" };
2331 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
2333 } else if is_type_diagnostic_item(cx, cx.tables.expr_ty(&iter_args[0]), sym!(vec_type)) {
2335 } else if is_type_diagnostic_item(cx, cx.tables.expr_ty(&iter_args[0]), sym!(vecdeque_type)) {
2338 let nth_args = nth_and_iter_args[0];
2339 lint_iter_nth_zero(cx, expr, &nth_args);
2340 return; // caller is not a type that we want to lint
2347 &format!("called `.iter{0}().nth()` on a {1}", mut_str, caller_type),
2349 &format!("calling `.get{}()` is both faster and more readable", mut_str),
2353 fn lint_iter_nth_zero<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
2355 if match_trait_method(cx, expr, &paths::ITERATOR);
2356 if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &nth_args[1]);
2358 let mut applicability = Applicability::MachineApplicable;
2363 "called `.nth(0)` on a `std::iter::Iterator`",
2365 format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
2372 fn lint_get_unwrap<'a, 'tcx>(
2373 cx: &LateContext<'a, 'tcx>,
2374 expr: &hir::Expr<'_>,
2375 get_args: &'tcx [hir::Expr<'_>],
2378 // Note: we don't want to lint `get_mut().unwrap` for `HashMap` or `BTreeMap`,
2379 // because they do not implement `IndexMut`
2380 let mut applicability = Applicability::MachineApplicable;
2381 let expr_ty = cx.tables.expr_ty(&get_args[0]);
2382 let get_args_str = if get_args.len() > 1 {
2383 snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
2385 return; // not linting on a .get().unwrap() chain or variant
2388 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
2389 needs_ref = get_args_str.parse::<usize>().is_ok();
2391 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vec_type)) {
2392 needs_ref = get_args_str.parse::<usize>().is_ok();
2394 } else if is_type_diagnostic_item(cx, expr_ty, sym!(vecdeque_type)) {
2395 needs_ref = get_args_str.parse::<usize>().is_ok();
2397 } else if !is_mut && is_type_diagnostic_item(cx, expr_ty, sym!(hashmap_type)) {
2400 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
2404 return; // caller is not a type that we want to lint
2407 let mut span = expr.span;
2409 // Handle the case where the result is immediately dereferenced
2410 // by not requiring ref and pulling the dereference into the
2414 if let Some(parent) = get_parent_expr(cx, expr);
2415 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.kind;
2422 let mut_str = if is_mut { "_mut" } else { "" };
2423 let borrow_str = if !needs_ref {
2436 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
2437 mut_str, caller_type
2443 snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
2450 fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
2451 // lint if caller of skip is an Iterator
2452 if match_trait_method(cx, expr, &paths::ITERATOR) {
2457 "called `skip(x).next()` on an iterator",
2459 "this is more succinctly expressed by calling `nth(x)`",
2464 fn derefs_to_slice<'a, 'tcx>(
2465 cx: &LateContext<'a, 'tcx>,
2466 expr: &'tcx hir::Expr<'tcx>,
2468 ) -> Option<&'tcx hir::Expr<'tcx>> {
2469 fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
2471 ty::Slice(_) => true,
2472 ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
2473 ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym!(vec_type)),
2474 ty::Array(_, size) => {
2475 if let Some(size) = size.try_eval_usize(cx.tcx, cx.param_env) {
2481 ty::Ref(_, inner, _) => may_slice(cx, inner),
2486 if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
2487 if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
2494 ty::Slice(_) => Some(expr),
2495 ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
2496 ty::Ref(_, inner, _) => {
2497 if may_slice(cx, inner) {
2508 /// lint use of `unwrap()` for `Option`s and `Result`s
2509 fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, unwrap_args: &[hir::Expr<'_>]) {
2510 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
2512 let mess = if is_type_diagnostic_item(cx, obj_ty, sym!(option_type)) {
2513 Some((UNWRAP_USED, "an Option", "None"))
2514 } else if is_type_diagnostic_item(cx, obj_ty, sym!(result_type)) {
2515 Some((UNWRAP_USED, "a Result", "Err"))
2520 if let Some((lint, kind, none_value)) = mess {
2525 &format!("used `unwrap()` on `{}` value", kind,),
2528 "if you don't want to handle the `{}` case gracefully, consider \
2529 using `expect()` to provide a better panic message",
2536 /// lint use of `expect()` for `Option`s and `Result`s
2537 fn lint_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, expect_args: &[hir::Expr<'_>]) {
2538 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&expect_args[0]));
2540 let mess = if is_type_diagnostic_item(cx, obj_ty, sym!(option_type)) {
2541 Some((EXPECT_USED, "an Option", "None"))
2542 } else if is_type_diagnostic_item(cx, obj_ty, sym!(result_type)) {
2543 Some((EXPECT_USED, "a Result", "Err"))
2548 if let Some((lint, kind, none_value)) = mess {
2553 &format!("used `expect()` on `{}` value", kind,),
2555 &format!("if this value is an `{}`, it will panic", none_value,),
2560 /// lint use of `ok().expect()` for `Result`s
2561 fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
2563 // lint if the caller of `ok()` is a `Result`
2564 if is_type_diagnostic_item(cx, cx.tables.expr_ty(&ok_args[0]), sym!(result_type));
2565 let result_type = cx.tables.expr_ty(&ok_args[0]);
2566 if let Some(error_type) = get_error_type(cx, result_type);
2567 if has_debug_impl(error_type, cx);
2574 "called `ok().expect()` on a `Result` value",
2576 "you can call `expect()` directly on the `Result`",
2582 /// lint use of `map().flatten()` for `Iterators` and 'Options'
2583 fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) {
2584 // lint if caller of `.map().flatten()` is an Iterator
2585 if match_trait_method(cx, expr, &paths::ITERATOR) {
2586 let msg = "called `map(..).flatten()` on an `Iterator`. \
2587 This is more succinctly expressed by calling `.flat_map(..)`";
2588 let self_snippet = snippet(cx, map_args[0].span, "..");
2589 let func_snippet = snippet(cx, map_args[1].span, "..");
2590 let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
2596 "try using `flat_map` instead",
2598 Applicability::MachineApplicable,
2602 // lint if caller of `.map().flatten()` is an Option
2603 if is_type_diagnostic_item(cx, cx.tables.expr_ty(&map_args[0]), sym!(option_type)) {
2604 let msg = "called `map(..).flatten()` on an `Option`. \
2605 This is more succinctly expressed by calling `.and_then(..)`";
2606 let self_snippet = snippet(cx, map_args[0].span, "..");
2607 let func_snippet = snippet(cx, map_args[1].span, "..");
2608 let hint = format!("{0}.and_then({1})", self_snippet, func_snippet);
2614 "try using `and_then` instead",
2616 Applicability::MachineApplicable,
2621 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
2622 fn lint_map_unwrap_or_else<'a, 'tcx>(
2623 cx: &LateContext<'a, 'tcx>,
2624 expr: &'tcx hir::Expr<'_>,
2625 map_args: &'tcx [hir::Expr<'_>],
2626 unwrap_args: &'tcx [hir::Expr<'_>],
2628 // lint if the caller of `map()` is an `Option`
2629 let is_option = is_type_diagnostic_item(cx, cx.tables.expr_ty(&map_args[0]), sym!(option_type));
2630 let is_result = is_type_diagnostic_item(cx, cx.tables.expr_ty(&map_args[0]), sym!(result_type));
2632 if is_option || is_result {
2633 // Don't make a suggestion that may fail to compile due to mutably borrowing
2634 // the same variable twice.
2635 let map_mutated_vars = mutated_variables(&map_args[0], cx);
2636 let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
2637 if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
2638 if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
2646 let msg = if is_option {
2647 "called `map(f).unwrap_or_else(g)` on an `Option` value. This can be done more directly by calling \
2648 `map_or_else(g, f)` instead"
2650 "called `map(f).unwrap_or_else(g)` on a `Result` value. This can be done more directly by calling \
2651 `.map_or_else(g, f)` instead"
2653 // get snippets for args to map() and unwrap_or_else()
2654 let map_snippet = snippet(cx, map_args[1].span, "..");
2655 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
2656 // lint, with note if neither arg is > 1 line and both map() and
2657 // unwrap_or_else() have the same span
2658 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
2659 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
2660 if same_span && !multiline {
2668 "replace `map({0}).unwrap_or_else({1})` with `map_or_else({1}, {0})`",
2669 map_snippet, unwrap_snippet,
2672 } else if same_span && multiline {
2673 span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
2678 /// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
2679 fn lint_map_or_none<'a, 'tcx>(
2680 cx: &LateContext<'a, 'tcx>,
2681 expr: &'tcx hir::Expr<'_>,
2682 map_or_args: &'tcx [hir::Expr<'_>],
2684 let is_option = is_type_diagnostic_item(cx, cx.tables.expr_ty(&map_or_args[0]), sym!(option_type));
2685 let is_result = is_type_diagnostic_item(cx, cx.tables.expr_ty(&map_or_args[0]), sym!(result_type));
2687 // There are two variants of this `map_or` lint:
2688 // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
2689 // (2) using `map_or` as a combinator instead of `and_then`
2691 // (For this lint) we don't care if any other type calls `map_or`
2692 if !is_option && !is_result {
2696 let (lint_name, msg, instead, hint) = {
2697 let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
2698 match_qpath(qpath, &paths::OPTION_NONE)
2703 if !default_arg_is_none {
2708 let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
2709 match_qpath(qpath, &paths::OPTION_SOME)
2715 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2716 let func_snippet = snippet(cx, map_or_args[2].span, "..");
2717 let msg = "called `map_or(None, f)` on an `Option` value. This can be done more directly by calling \
2718 `and_then(f)` instead";
2722 "try using `and_then` instead",
2723 format!("{0}.and_then({1})", self_snippet, func_snippet),
2725 } else if f_arg_is_some {
2726 let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
2728 let self_snippet = snippet(cx, map_or_args[0].span, "..");
2730 RESULT_MAP_OR_INTO_OPTION,
2732 "try using `ok` instead",
2733 format!("{0}.ok()", self_snippet),
2748 Applicability::MachineApplicable,
2752 /// lint use of `filter().next()` for `Iterators`
2753 fn lint_filter_next<'a, 'tcx>(
2754 cx: &LateContext<'a, 'tcx>,
2755 expr: &'tcx hir::Expr<'_>,
2756 filter_args: &'tcx [hir::Expr<'_>],
2758 // lint if caller of `.filter().next()` is an Iterator
2759 if match_trait_method(cx, expr, &paths::ITERATOR) {
2760 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2761 `.find(p)` instead.";
2762 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2763 if filter_snippet.lines().count() <= 1 {
2764 // add note if not multi-line
2771 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
2774 span_lint(cx, FILTER_NEXT, expr.span, msg);
2779 /// lint use of `skip_while().next()` for `Iterators`
2780 fn lint_skip_while_next<'a, 'tcx>(
2781 cx: &LateContext<'a, 'tcx>,
2782 expr: &'tcx hir::Expr<'_>,
2783 _skip_while_args: &'tcx [hir::Expr<'_>],
2785 // lint if caller of `.skip_while().next()` is an Iterator
2786 if match_trait_method(cx, expr, &paths::ITERATOR) {
2791 "called `skip_while(p).next()` on an `Iterator`",
2793 "this is more succinctly expressed by calling `.find(!p)` instead",
2798 /// lint use of `filter().map()` for `Iterators`
2799 fn lint_filter_map<'a, 'tcx>(
2800 cx: &LateContext<'a, 'tcx>,
2801 expr: &'tcx hir::Expr<'_>,
2802 _filter_args: &'tcx [hir::Expr<'_>],
2803 _map_args: &'tcx [hir::Expr<'_>],
2805 // lint if caller of `.filter().map()` is an Iterator
2806 if match_trait_method(cx, expr, &paths::ITERATOR) {
2807 let msg = "called `filter(p).map(q)` on an `Iterator`";
2808 let hint = "this is more succinctly expressed by calling `.filter_map(..)` instead";
2809 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2813 /// lint use of `filter_map().next()` for `Iterators`
2814 fn lint_filter_map_next<'a, 'tcx>(
2815 cx: &LateContext<'a, 'tcx>,
2816 expr: &'tcx hir::Expr<'_>,
2817 filter_args: &'tcx [hir::Expr<'_>],
2819 if match_trait_method(cx, expr, &paths::ITERATOR) {
2820 let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
2821 `.find_map(p)` instead.";
2822 let filter_snippet = snippet(cx, filter_args[1].span, "..");
2823 if filter_snippet.lines().count() <= 1 {
2830 &format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
2833 span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
2838 /// lint use of `find().map()` for `Iterators`
2839 fn lint_find_map<'a, 'tcx>(
2840 cx: &LateContext<'a, 'tcx>,
2841 expr: &'tcx hir::Expr<'_>,
2842 _find_args: &'tcx [hir::Expr<'_>],
2843 map_args: &'tcx [hir::Expr<'_>],
2845 // lint if caller of `.filter().map()` is an Iterator
2846 if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
2847 let msg = "called `find(p).map(q)` on an `Iterator`";
2848 let hint = "this is more succinctly expressed by calling `.find_map(..)` instead";
2849 span_lint_and_help(cx, FIND_MAP, expr.span, msg, None, hint);
2853 /// lint use of `filter_map().map()` for `Iterators`
2854 fn lint_filter_map_map<'a, 'tcx>(
2855 cx: &LateContext<'a, 'tcx>,
2856 expr: &'tcx hir::Expr<'_>,
2857 _filter_args: &'tcx [hir::Expr<'_>],
2858 _map_args: &'tcx [hir::Expr<'_>],
2860 // lint if caller of `.filter().map()` is an Iterator
2861 if match_trait_method(cx, expr, &paths::ITERATOR) {
2862 let msg = "called `filter_map(p).map(q)` on an `Iterator`";
2863 let hint = "this is more succinctly expressed by only calling `.filter_map(..)` instead";
2864 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2868 /// lint use of `filter().flat_map()` for `Iterators`
2869 fn lint_filter_flat_map<'a, 'tcx>(
2870 cx: &LateContext<'a, 'tcx>,
2871 expr: &'tcx hir::Expr<'_>,
2872 _filter_args: &'tcx [hir::Expr<'_>],
2873 _map_args: &'tcx [hir::Expr<'_>],
2875 // lint if caller of `.filter().flat_map()` is an Iterator
2876 if match_trait_method(cx, expr, &paths::ITERATOR) {
2877 let msg = "called `filter(p).flat_map(q)` on an `Iterator`";
2878 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
2879 and filtering by returning `iter::empty()`";
2880 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2884 /// lint use of `filter_map().flat_map()` for `Iterators`
2885 fn lint_filter_map_flat_map<'a, 'tcx>(
2886 cx: &LateContext<'a, 'tcx>,
2887 expr: &'tcx hir::Expr<'_>,
2888 _filter_args: &'tcx [hir::Expr<'_>],
2889 _map_args: &'tcx [hir::Expr<'_>],
2891 // lint if caller of `.filter_map().flat_map()` is an Iterator
2892 if match_trait_method(cx, expr, &paths::ITERATOR) {
2893 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`";
2894 let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
2895 and filtering by returning `iter::empty()`";
2896 span_lint_and_help(cx, FILTER_MAP, expr.span, msg, None, hint);
2900 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
2901 fn lint_flat_map_identity<'a, 'tcx>(
2902 cx: &LateContext<'a, 'tcx>,
2903 expr: &'tcx hir::Expr<'_>,
2904 flat_map_args: &'tcx [hir::Expr<'_>],
2905 flat_map_span: Span,
2907 if match_trait_method(cx, expr, &paths::ITERATOR) {
2908 let arg_node = &flat_map_args[1].kind;
2910 let apply_lint = |message: &str| {
2914 flat_map_span.with_hi(expr.span.hi()),
2917 "flatten()".to_string(),
2918 Applicability::MachineApplicable,
2923 if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
2924 let body = cx.tcx.hir().body(*body_id);
2926 if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
2927 if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
2929 if path.segments.len() == 1;
2930 if path.segments[0].ident.as_str() == binding_ident.as_str();
2933 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
2938 if let hir::ExprKind::Path(ref qpath) = arg_node;
2940 if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
2943 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
2949 /// lint searching an Iterator followed by `is_some()`
2950 fn lint_search_is_some<'a, 'tcx>(
2951 cx: &LateContext<'a, 'tcx>,
2952 expr: &'tcx hir::Expr<'_>,
2953 search_method: &str,
2954 search_args: &'tcx [hir::Expr<'_>],
2955 is_some_args: &'tcx [hir::Expr<'_>],
2958 // lint if caller of search is an Iterator
2959 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
2961 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
2962 expressed by calling `any()`.",
2965 let search_snippet = snippet(cx, search_args[1].span, "..");
2966 if search_snippet.lines().count() <= 1 {
2967 // suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
2968 // suggest `any(|..| *..)` instead of `any(|..| **..)` for `find(|..| **..).is_some()`
2969 let any_search_snippet = if_chain! {
2970 if search_method == "find";
2971 if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].kind;
2972 let closure_body = cx.tcx.hir().body(body_id);
2973 if let Some(closure_arg) = closure_body.params.get(0);
2975 if let hir::PatKind::Ref(..) = closure_arg.pat.kind {
2976 Some(search_snippet.replacen('&', "", 1))
2977 } else if let Some(name) = get_arg_name(&closure_arg.pat) {
2978 Some(search_snippet.replace(&format!("*{}", name), &name.as_str()))
2986 // add note if not multi-line
2990 method_span.with_hi(expr.span.hi()),
2995 any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
2997 Applicability::MachineApplicable,
3000 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
3005 /// Used for `lint_binary_expr_with_method_call`.
3006 #[derive(Copy, Clone)]
3007 struct BinaryExprInfo<'a> {
3008 expr: &'a hir::Expr<'a>,
3009 chain: &'a hir::Expr<'a>,
3010 other: &'a hir::Expr<'a>,
3014 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3015 fn lint_binary_expr_with_method_call(cx: &LateContext<'_, '_>, info: &mut BinaryExprInfo<'_>) {
3016 macro_rules! lint_with_both_lhs_and_rhs {
3017 ($func:ident, $cx:expr, $info:ident) => {
3018 if !$func($cx, $info) {
3019 ::std::mem::swap(&mut $info.chain, &mut $info.other);
3020 if $func($cx, $info) {
3027 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
3028 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
3029 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
3030 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
3033 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
3035 cx: &LateContext<'_, '_>,
3036 info: &BinaryExprInfo<'_>,
3037 chain_methods: &[&str],
3038 lint: &'static Lint,
3042 if let Some(args) = method_chain_args(info.chain, chain_methods);
3043 if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
3044 if arg_char.len() == 1;
3045 if let hir::ExprKind::Path(ref qpath) = fun.kind;
3046 if let Some(segment) = single_segment_path(qpath);
3047 if segment.ident.name == sym!(Some);
3049 let mut applicability = Applicability::MachineApplicable;
3050 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
3052 if self_ty.kind != ty::Str {
3060 &format!("you should use the `{}` method", suggest),
3062 format!("{}{}.{}({})",
3063 if info.eq { "" } else { "!" },
3064 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
3066 snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
3077 /// Checks for the `CHARS_NEXT_CMP` lint.
3078 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3079 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
3082 /// Checks for the `CHARS_LAST_CMP` lint.
3083 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3084 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
3087 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
3091 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
3092 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
3093 cx: &LateContext<'a, 'tcx>,
3094 info: &BinaryExprInfo<'_>,
3095 chain_methods: &[&str],
3096 lint: &'static Lint,
3100 if let Some(args) = method_chain_args(info.chain, chain_methods);
3101 if let hir::ExprKind::Lit(ref lit) = info.other.kind;
3102 if let ast::LitKind::Char(c) = lit.node;
3104 let mut applicability = Applicability::MachineApplicable;
3109 &format!("you should use the `{}` method", suggest),
3111 format!("{}{}.{}('{}')",
3112 if info.eq { "" } else { "!" },
3113 snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
3126 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
3127 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3128 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
3131 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
3132 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
3133 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
3136 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
3140 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
3141 fn lint_single_char_pattern<'a, 'tcx>(
3142 cx: &LateContext<'a, 'tcx>,
3143 _expr: &'tcx hir::Expr<'_>,
3144 arg: &'tcx hir::Expr<'_>,
3147 if let hir::ExprKind::Lit(lit) = &arg.kind;
3148 if let ast::LitKind::Str(r, style) = lit.node;
3149 if r.as_str().len() == 1;
3151 let mut applicability = Applicability::MachineApplicable;
3152 let snip = snippet_with_applicability(cx, arg.span, "..", &mut applicability);
3153 let ch = if let ast::StrStyle::Raw(nhash) = style {
3154 let nhash = nhash as usize;
3155 // for raw string: r##"a"##
3156 &snip[(nhash + 2)..(snip.len() - 1 - nhash)]
3158 // for regular string: "a"
3159 &snip[1..(snip.len() - 1)]
3161 let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
3164 SINGLE_CHAR_PATTERN,
3166 "single-character string constant used as pattern",
3167 "try using a `char` instead",
3175 /// Checks for the `USELESS_ASREF` lint.
3176 fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, call_name: &str, as_ref_args: &[hir::Expr<'_>]) {
3177 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
3178 // check if the call is to the actual `AsRef` or `AsMut` trait
3179 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
3180 // check if the type after `as_ref` or `as_mut` is the same as before
3181 let recvr = &as_ref_args[0];
3182 let rcv_ty = cx.tables.expr_ty(recvr);
3183 let res_ty = cx.tables.expr_ty(expr);
3184 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
3185 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
3186 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
3187 // allow the `as_ref` or `as_mut` if it is followed by another method call
3189 if let Some(parent) = get_parent_expr(cx, expr);
3190 if let hir::ExprKind::MethodCall(_, ref span, _) = parent.kind;
3191 if span != &expr.span;
3197 let mut applicability = Applicability::MachineApplicable;
3202 &format!("this call to `{}` does nothing", call_name),
3204 snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
3211 fn ty_has_iter_method(cx: &LateContext<'_, '_>, self_ref_ty: Ty<'_>) -> Option<(&'static str, &'static str)> {
3212 has_iter_method(cx, self_ref_ty).map(|ty_name| {
3213 let mutbl = match self_ref_ty.kind {
3214 ty::Ref(_, _, mutbl) => mutbl,
3215 _ => unreachable!(),
3217 let method_name = match mutbl {
3218 hir::Mutability::Not => "iter",
3219 hir::Mutability::Mut => "iter_mut",
3221 (ty_name, method_name)
3225 fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, self_ref_ty: Ty<'_>, method_span: Span) {
3226 if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
3229 if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
3235 "this `.into_iter()` call is equivalent to `.{}()` and will not move the `{}`",
3239 method_name.to_string(),
3240 Applicability::MachineApplicable,
3245 /// lint for `MaybeUninit::uninit().assume_init()` (we already have the latter)
3246 fn lint_maybe_uninit(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, outer: &hir::Expr<'_>) {
3248 if let hir::ExprKind::Call(ref callee, ref args) = expr.kind;
3250 if let hir::ExprKind::Path(ref path) = callee.kind;
3251 if match_qpath(path, &paths::MEM_MAYBEUNINIT_UNINIT);
3252 if !is_maybe_uninit_ty_valid(cx, cx.tables.expr_ty_adjusted(outer));
3256 UNINIT_ASSUMED_INIT,
3258 "this call for this type may be undefined behavior"
3264 fn is_maybe_uninit_ty_valid(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
3266 ty::Array(ref component, _) => is_maybe_uninit_ty_valid(cx, component),
3267 ty::Tuple(ref types) => types.types().all(|ty| is_maybe_uninit_ty_valid(cx, ty)),
3268 ty::Adt(ref adt, _) => match_def_path(cx, adt.did, &paths::MEM_MAYBEUNINIT),
3273 fn lint_suspicious_map(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
3278 "this call to `map()` won't have an effect on the call to `count()`",
3280 "make sure you did not confuse `map` with `filter` or `for_each`",
3284 /// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
3285 fn lint_option_as_ref_deref<'a, 'tcx>(
3286 cx: &LateContext<'a, 'tcx>,
3287 expr: &hir::Expr<'_>,
3288 as_ref_args: &[hir::Expr<'_>],
3289 map_args: &[hir::Expr<'_>],
3292 let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
3294 let option_ty = cx.tables.expr_ty(&as_ref_args[0]);
3295 if !is_type_diagnostic_item(cx, option_ty, sym!(option_type)) {
3299 let deref_aliases: [&[&str]; 9] = [
3300 &paths::DEREF_TRAIT_METHOD,
3301 &paths::DEREF_MUT_TRAIT_METHOD,
3302 &paths::CSTRING_AS_C_STR,
3303 &paths::OS_STRING_AS_OS_STR,
3304 &paths::PATH_BUF_AS_PATH,
3305 &paths::STRING_AS_STR,
3306 &paths::STRING_AS_MUT_STR,
3307 &paths::VEC_AS_SLICE,
3308 &paths::VEC_AS_MUT_SLICE,
3311 let is_deref = match map_args[1].kind {
3312 hir::ExprKind::Path(ref expr_qpath) => deref_aliases.iter().any(|path| match_qpath(expr_qpath, path)),
3313 hir::ExprKind::Closure(_, _, body_id, _, _) => {
3314 let closure_body = cx.tcx.hir().body(body_id);
3315 let closure_expr = remove_blocks(&closure_body.value);
3317 match &closure_expr.kind {
3318 hir::ExprKind::MethodCall(_, _, args) => {
3321 if let hir::ExprKind::Path(qpath) = &args[0].kind;
3322 if let hir::def::Res::Local(local_id) = cx.tables.qpath_res(qpath, args[0].hir_id);
3323 if closure_body.params[0].pat.hir_id == local_id;
3324 let adj = cx.tables.expr_adjustments(&args[0]).iter().map(|x| &x.kind).collect::<Box<[_]>>();
3325 if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
3327 let method_did = cx.tables.type_dependent_def_id(closure_expr.hir_id).unwrap();
3328 deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
3334 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, m, ref inner) if same_mutability(m) => {
3336 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner1) = inner.kind;
3337 if let hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner2) = inner1.kind;
3338 if let hir::ExprKind::Path(ref qpath) = inner2.kind;
3339 if let hir::def::Res::Local(local_id) = cx.tables.qpath_res(qpath, inner2.hir_id);
3341 closure_body.params[0].pat.hir_id == local_id
3354 let current_method = if is_mut {
3355 format!(".as_mut().map({})", snippet(cx, map_args[1].span, ".."))
3357 format!(".as_ref().map({})", snippet(cx, map_args[1].span, ".."))
3359 let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
3360 let hint = format!("{}.{}()", snippet(cx, as_ref_args[0].span, ".."), method_hint);
3361 let suggestion = format!("try using {} instead", method_hint);
3364 "called `{0}` on an Option value. This can be done more directly \
3365 by calling `{1}` instead",
3366 current_method, hint
3370 OPTION_AS_REF_DEREF,
3375 Applicability::MachineApplicable,
3380 /// Given a `Result<T, E>` type, return its error type (`E`).
3381 fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
3383 ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym!(result_type)) => substs.types().nth(1),
3388 /// This checks whether a given type is known to implement Debug.
3389 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
3391 .get_diagnostic_item(sym::debug_trait)
3392 .map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
3397 StartsWith(&'static str),
3401 const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
3402 (Convention::Eq("new"), &[SelfKind::No]),
3403 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
3404 (Convention::StartsWith("from_"), &[SelfKind::No]),
3405 (Convention::StartsWith("into_"), &[SelfKind::Value]),
3406 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
3407 (Convention::Eq("to_mut"), &[SelfKind::RefMut]),
3408 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
3411 const FN_HEADER: hir::FnHeader = hir::FnHeader {
3412 unsafety: hir::Unsafety::Normal,
3413 constness: hir::Constness::NotConst,
3414 asyncness: hir::IsAsync::NotAsync,
3415 abi: rustc_target::spec::abi::Abi::Rust,
3419 const TRAIT_METHODS: [(&str, usize, &hir::FnHeader, SelfKind, OutType, &str); 30] = [
3420 ("add", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Add"),
3421 ("as_mut", 1, &FN_HEADER, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
3422 ("as_ref", 1, &FN_HEADER, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
3423 ("bitand", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
3424 ("bitor", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
3425 ("bitxor", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
3426 ("borrow", 1, &FN_HEADER, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
3427 ("borrow_mut", 1, &FN_HEADER, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
3428 ("clone", 1, &FN_HEADER, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
3429 ("cmp", 2, &FN_HEADER, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
3430 ("default", 0, &FN_HEADER, SelfKind::No, OutType::Any, "std::default::Default"),
3431 ("deref", 1, &FN_HEADER, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
3432 ("deref_mut", 1, &FN_HEADER, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
3433 ("div", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Div"),
3434 ("drop", 1, &FN_HEADER, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
3435 ("eq", 2, &FN_HEADER, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
3436 ("from_iter", 1, &FN_HEADER, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
3437 ("from_str", 1, &FN_HEADER, SelfKind::No, OutType::Any, "std::str::FromStr"),
3438 ("hash", 2, &FN_HEADER, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
3439 ("index", 2, &FN_HEADER, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
3440 ("index_mut", 2, &FN_HEADER, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
3441 ("into_iter", 1, &FN_HEADER, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
3442 ("mul", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Mul"),
3443 ("neg", 1, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Neg"),
3444 ("next", 1, &FN_HEADER, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
3445 ("not", 1, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Not"),
3446 ("rem", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Rem"),
3447 ("shl", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Shl"),
3448 ("shr", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Shr"),
3449 ("sub", 2, &FN_HEADER, SelfKind::Value, OutType::Any, "std::ops::Sub"),
3453 const PATTERN_METHODS: [(&str, usize); 17] = [
3461 ("split_terminator", 1),
3462 ("rsplit_terminator", 1),
3467 ("match_indices", 1),
3468 ("rmatch_indices", 1),
3469 ("trim_start_matches", 1),
3470 ("trim_end_matches", 1),
3473 #[derive(Clone, Copy, PartialEq, Debug)]
3482 fn matches<'a>(self, cx: &LateContext<'_, 'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
3483 fn matches_value<'a>(cx: &LateContext<'_, 'a>, parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
3484 if ty == parent_ty {
3486 } else if ty.is_box() {
3487 ty.boxed_ty() == parent_ty
3488 } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
3489 if let ty::Adt(_, substs) = ty.kind {
3490 substs.types().next().map_or(false, |t| t == parent_ty)
3500 cx: &LateContext<'_, 'a>,
3501 mutability: hir::Mutability,
3505 if let ty::Ref(_, t, m) = ty.kind {
3506 return m == mutability && t == parent_ty;
3509 let trait_path = match mutability {
3510 hir::Mutability::Not => &paths::ASREF_TRAIT,
3511 hir::Mutability::Mut => &paths::ASMUT_TRAIT,
3514 let trait_def_id = match get_trait_def_id(cx, trait_path) {
3516 None => return false,
3518 implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
3522 Self::Value => matches_value(cx, parent_ty, ty),
3523 Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
3524 Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
3525 Self::No => ty != parent_ty,
3530 fn description(self) -> &'static str {
3532 Self::Value => "self by value",
3533 Self::Ref => "self by reference",
3534 Self::RefMut => "self by mutable reference",
3535 Self::No => "no self",
3542 fn check(&self, other: &str) -> bool {
3544 Self::Eq(this) => this == other,
3545 Self::StartsWith(this) => other.starts_with(this) && this != other,
3550 impl fmt::Display for Convention {
3551 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
3553 Self::Eq(this) => this.fmt(f),
3554 Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
3559 #[derive(Clone, Copy)]
3568 fn matches(self, cx: &LateContext<'_, '_>, ty: &hir::FnRetTy<'_>) -> bool {
3569 let is_unit = |ty: &hir::Ty<'_>| SpanlessEq::new(cx).eq_ty_kind(&ty.kind, &hir::TyKind::Tup(&[]));
3571 (Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
3572 (Self::Unit, &hir::FnRetTy::Return(ref ty)) if is_unit(ty) => true,
3573 (Self::Bool, &hir::FnRetTy::Return(ref ty)) if is_bool(ty) => true,
3574 (Self::Any, &hir::FnRetTy::Return(ref ty)) if !is_unit(ty) => true,
3575 (Self::Ref, &hir::FnRetTy::Return(ref ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
3581 fn is_bool(ty: &hir::Ty<'_>) -> bool {
3582 if let hir::TyKind::Path(ref p) = ty.kind {
3583 match_qpath(p, &["bool"])
3589 // Returns `true` if `expr` contains a return expression
3590 fn contains_return(expr: &hir::Expr<'_>) -> bool {
3591 struct RetCallFinder {
3595 impl<'tcx> intravisit::Visitor<'tcx> for RetCallFinder {
3596 type Map = Map<'tcx>;
3598 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
3602 if let hir::ExprKind::Ret(..) = &expr.kind {
3605 intravisit::walk_expr(self, expr);
3609 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
3610 intravisit::NestedVisitorMap::None
3614 let mut visitor = RetCallFinder { found: false };
3615 visitor.visit_expr(expr);
3619 fn check_pointer_offset(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3622 if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.tables.expr_ty(&args[0]).kind;
3623 if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
3626 span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
3631 fn lint_filetype_is_file(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
3632 let ty = cx.tables.expr_ty(&args[0]);
3634 if !match_type(cx, ty, &paths::FILE_TYPE) {
3640 let lint_unary: &str;
3641 let help_unary: &str;
3643 if let Some(parent) = get_parent_expr(cx, expr);
3644 if let hir::ExprKind::Unary(op, _) = parent.kind;
3645 if op == hir::UnOp::UnNot;
3658 let lint_msg = format!("`{}FileType::is_file()` only {} regular files", lint_unary, verb);
3659 let help_msg = format!("use `{}FileType::is_dir()` instead", help_unary);
3660 span_lint_and_help(cx, FILETYPE_IS_FILE, span, &lint_msg, None, &help_msg);
3663 fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
3664 expected.constness == actual.constness
3665 && expected.unsafety == actual.unsafety
3666 && expected.asyncness == actual.asyncness