3 use rustc::middle::const_val::ConstVal;
4 use rustc::ty::{self, Ty};
5 use rustc::hir::def::Def;
6 use rustc::ty::subst::Substs;
7 use rustc_const_eval::ConstContext;
12 use syntax::codemap::{Span, BytePos};
13 use utils::{get_arg_name, get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, is_self, is_self_ty,
14 iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method,
15 match_type, method_chain_args, match_var, return_ty, remove_blocks, same_tys, single_segment_path, snippet,
16 span_lint, span_lint_and_sugg, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
19 use utils::const_to_u64;
24 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
26 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
27 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
28 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
29 /// `Allow` by default.
31 /// **Known problems:** None.
38 pub OPTION_UNWRAP_USED,
40 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
43 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
45 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
46 /// values. Normally, you want to implement more sophisticated error handling,
47 /// and propagate errors upwards with `try!`.
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.
60 pub RESULT_UNWRAP_USED,
62 "using `Result.unwrap()`, which might be better handled"
65 /// **What it does:** Checks for methods that should live in a trait
66 /// implementation of a `std` trait (see [llogiq's blog
67 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
68 /// information) instead of an inherent implementation.
70 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
71 /// the code, often with very little cost. Also people seeing a `mul(...)`
73 /// may expect `*` to work equally, so you should have good reason to disappoint
76 /// **Known problems:** None.
82 /// fn add(&self, other: &X) -> X { .. }
86 pub SHOULD_IMPLEMENT_TRAIT,
88 "defining a method that should be implementing a std trait"
91 /// **What it does:** Checks for methods with certain name prefixes and which
92 /// doesn't match how self is taken. The actual rules are:
94 /// |Prefix |`self` taken |
95 /// |-------|----------------------|
96 /// |`as_` |`&self` or `&mut self`|
99 /// |`is_` |`&self` or none |
100 /// |`to_` |`&self` |
102 /// **Why is this bad?** Consistency breeds readability. If you follow the
103 /// conventions, your users won't be surprised that they, e.g., need to supply a
104 /// mutable reference to a `as_..` function.
106 /// **Known problems:** None.
111 /// fn as_str(self) -> &str { .. }
115 pub WRONG_SELF_CONVENTION,
117 "defining a method named with an established prefix (like \"into_\") that takes \
118 `self` with the wrong convention"
121 /// **What it does:** This is the same as
122 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
124 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
126 /// **Known problems:** Actually *renaming* the function may break clients if
127 /// the function is part of the public interface. In that case, be mindful of
128 /// the stability guarantees you've given your users.
133 /// pub fn as_str(self) -> &str { .. }
137 pub WRONG_PUB_SELF_CONVENTION,
139 "defining a public method named with an established prefix (like \"into_\") that takes \
140 `self` with the wrong convention"
143 /// **What it does:** Checks for usage of `ok().expect(..)`.
145 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
146 /// directly to get a better error message.
148 /// **Known problems:** None.
152 /// x.ok().expect("why did I do this again?")
157 "using `ok().expect()`, which gives worse error messages than \
158 calling `expect` directly on the Result"
161 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
163 /// **Why is this bad?** Readability, this can be written more concisely as
164 /// `_.map_or(_, _)`.
166 /// **Known problems:** None.
170 /// x.map(|a| a + 1).unwrap_or(0)
173 pub OPTION_MAP_UNWRAP_OR,
175 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
179 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
181 /// **Why is this bad?** Readability, this can be written more concisely as
182 /// `_.map_or_else(_, _)`.
184 /// **Known problems:** None.
188 /// x.map(|a| a + 1).unwrap_or_else(some_function)
191 pub OPTION_MAP_UNWRAP_OR_ELSE,
193 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
197 /// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
199 /// **Why is this bad?** Readability, this can be written more concisely as
200 /// `result.ok().map_or_else(_, _)`.
202 /// **Known problems:** None.
206 /// x.map(|a| a + 1).unwrap_or_else(some_function)
209 pub RESULT_MAP_UNWRAP_OR_ELSE,
211 "using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
212 `.ok().map_or_else(g, f)`"
215 /// **What it does:** Checks for usage of `_.map_or(None, _)`.
217 /// **Why is this bad?** Readability, this can be written more concisely as
220 /// **Known problems:** None.
224 /// opt.map_or(None, |a| a + 1)
227 pub OPTION_MAP_OR_NONE,
229 "using `Option.map_or(None, f)`, which is more succinctly expressed as \
233 /// **What it does:** Checks for usage of `_.filter(_).next()`.
235 /// **Why is this bad?** Readability, this can be written more concisely as
238 /// **Known problems:** None.
242 /// iter.filter(|x| x == 0).next()
247 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
250 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
251 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
253 /// **Why is this bad?** Readability, this can be written more concisely as a
254 /// single method call.
256 /// **Known problems:** Often requires a condition + Option/Iterator creation
257 /// inside the closure.
261 /// iter.filter(|x| x == 0).map(|x| x * 2)
266 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can \
267 usually be written as a single method call"
270 /// **What it does:** Checks for an iterator search (such as `find()`,
271 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
273 /// **Why is this bad?** Readability, this can be written more concisely as
276 /// **Known problems:** None.
280 /// iter.find(|x| x == 0).is_some()
285 "using an iterator search followed by `is_some()`, which is more succinctly \
286 expressed as a call to `any()`"
289 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
290 /// if it starts with a given char.
292 /// **Why is this bad?** Readability, this can be written more concisely as
293 /// `_.starts_with(_)`.
295 /// **Known problems:** None.
299 /// name.chars().next() == Some('_')
304 "using `.chars().next()` to check if a string starts with a char"
307 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
308 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
309 /// `unwrap_or_default` instead.
311 /// **Why is this bad?** The function will always be called and potentially
312 /// allocate an object acting as the default.
314 /// **Known problems:** If the function has side-effects, not calling it will
315 /// change the semantic of the program, but you shouldn't rely on that anyway.
319 /// foo.unwrap_or(String::new())
321 /// this can instead be written:
323 /// foo.unwrap_or_else(String::new)
327 /// foo.unwrap_or_default()
332 "using any `*or` method with a function call, which suggests `*or_else`"
335 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
337 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
338 /// generics, not for using the `clone` method on a concrete type.
340 /// **Known problems:** None.
349 "using `clone` on a `Copy` type"
352 /// **What it does:** Checks for usage of `.clone()` on a ref-counted pointer,
353 /// (Rc, Arc, rc::Weak, or sync::Weak), and suggests calling Clone on
354 /// the corresponding trait instead.
356 /// **Why is this bad?**: Calling '.clone()' on an Rc, Arc, or Weak
357 /// can obscure the fact that only the pointer is being cloned, not the underlying
364 declare_restriction_lint! {
365 pub CLONE_ON_REF_PTR,
366 "using 'clone' on a ref-counted pointer"
369 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
371 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
372 /// cloning the underlying `T`.
374 /// **Known problems:** None.
381 /// let z = y.clone();
382 /// println!("{:p} {:p}",*y, z); // prints out the same pointer
386 pub CLONE_DOUBLE_REF,
388 "using `clone` on `&&T`"
391 /// **What it does:** Checks for `new` not returning `Self`.
393 /// **Why is this bad?** As a convention, `new` methods are used to make a new
394 /// instance of a type.
396 /// **Known problems:** None.
401 /// fn new(..) -> NotAFoo {
408 "not returning `Self` in a `new` method"
411 /// **What it does:** Checks for string methods that receive a single-character
412 /// `str` as an argument, e.g. `_.split("x")`.
414 /// **Why is this bad?** Performing these methods using a `char` is faster than
417 /// **Known problems:** Does not catch multi-byte unicode characters.
420 /// `_.split("x")` could be `_.split('x')
422 pub SINGLE_CHAR_PATTERN,
424 "using a single-character str where a char could be used, e.g. \
428 /// **What it does:** Checks for getting the inner pointer of a temporary
431 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
432 /// as the `CString` is alive.
434 /// **Known problems:** None.
438 /// let c_str = CString::new("foo").unwrap().as_ptr();
440 /// call_some_ffi_func(c_str);
443 /// Here `c_str` point to a freed address. The correct use would be:
445 /// let c_str = CString::new("foo").unwrap();
447 /// call_some_ffi_func(c_str.as_ptr());
451 pub TEMPORARY_CSTRING_AS_PTR,
453 "getting the inner pointer of a temporary `CString`"
456 /// **What it does:** Checks for use of `.iter().nth()` (and the related
457 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
459 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
462 /// **Known problems:** None.
466 /// let some_vec = vec![0, 1, 2, 3];
467 /// let bad_vec = some_vec.iter().nth(3);
468 /// let bad_slice = &some_vec[..].iter().nth(3);
470 /// The correct use would be:
472 /// let some_vec = vec![0, 1, 2, 3];
473 /// let bad_vec = some_vec.get(3);
474 /// let bad_slice = &some_vec[..].get(3);
479 "using `.iter().nth()` on a standard library type with O(1) element access"
482 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
484 /// **Why is this bad?** `.nth(x)` is cleaner
486 /// **Known problems:** None.
490 /// let some_vec = vec![0, 1, 2, 3];
491 /// let bad_vec = some_vec.iter().skip(3).next();
492 /// let bad_slice = &some_vec[..].iter().skip(3).next();
494 /// The correct use would be:
496 /// let some_vec = vec![0, 1, 2, 3];
497 /// let bad_vec = some_vec.iter().nth(3);
498 /// let bad_slice = &some_vec[..].iter().nth(3);
503 "using `.skip(x).next()` on an iterator"
506 /// **What it does:** Checks for use of `.get().unwrap()` (or
507 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
509 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
512 /// **Known problems:** None.
516 /// let some_vec = vec![0, 1, 2, 3];
517 /// let last = some_vec.get(3).unwrap();
518 /// *some_vec.get_mut(0).unwrap() = 1;
520 /// The correct use would be:
522 /// let some_vec = vec![0, 1, 2, 3];
523 /// let last = some_vec[3];
529 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
532 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
533 /// `&str` or `String`.
535 /// **Why is this bad?** `.push_str(s)` is clearer
537 /// **Known problems:** None.
542 /// let def = String::from("def");
543 /// let mut s = String::new();
544 /// s.extend(abc.chars());
545 /// s.extend(def.chars());
547 /// The correct use would be:
550 /// let def = String::from("def");
551 /// let mut s = String::new();
553 /// s.push_str(&def));
556 pub STRING_EXTEND_CHARS,
558 "using `x.extend(s.chars())` where s is a `&str` or `String`"
561 /// **What it does:** Checks for the use of `.cloned().collect()` on slice to
564 /// **Why is this bad?** `.to_vec()` is clearer
566 /// **Known problems:** None.
570 /// let s = [1,2,3,4,5];
571 /// let s2 : Vec<isize> = s[..].iter().cloned().collect();
573 /// The better use would be:
575 /// let s = [1,2,3,4,5];
576 /// let s2 : Vec<isize> = s.to_vec();
579 pub ITER_CLONED_COLLECT,
581 "using `.cloned().collect()` on slice to create a `Vec`"
584 /// **What it does:** Checks for usage of `.chars().last()` or
585 /// `.chars().next_back()` on a `str` to check if it ends with a given char.
587 /// **Why is this bad?** Readability, this can be written more concisely as
588 /// `_.ends_with(_)`.
590 /// **Known problems:** None.
594 /// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
599 "using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
602 /// **What it does:** Checks for usage of `.as_ref()` or `.as_mut()` where the
603 /// types before and after the call are the same.
605 /// **Why is this bad?** The call is unnecessary.
607 /// **Known problems:** None.
611 /// let x: &[i32] = &[1,2,3,4,5];
612 /// do_stuff(x.as_ref());
614 /// The correct use would be:
616 /// let x: &[i32] = &[1,2,3,4,5];
622 "using `as_ref` where the types before and after the call are the same"
626 /// **What it does:** Checks for using `fold` when a more succinct alternative exists.
627 /// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
628 /// `sum` or `product`.
630 /// **Why is this bad?** Readability.
632 /// **Known problems:** None.
636 /// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
638 /// This could be written as:
640 /// let _ = (0..3).any(|x| x > 2);
643 pub UNNECESSARY_FOLD,
645 "using `fold` when a more succinct alternative exists"
648 impl LintPass for Pass {
649 fn get_lints(&self) -> LintArray {
653 SHOULD_IMPLEMENT_TRAIT,
654 WRONG_SELF_CONVENTION,
655 WRONG_PUB_SELF_CONVENTION,
657 OPTION_MAP_UNWRAP_OR,
658 OPTION_MAP_UNWRAP_OR_ELSE,
659 RESULT_MAP_UNWRAP_OR_ELSE,
670 TEMPORARY_CSTRING_AS_PTR,
684 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
685 #[allow(unused_attributes)]
686 // ^ required because `cyclomatic_complexity` attribute shows up as unused
687 #[cyclomatic_complexity = "30"]
688 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
689 if in_macro(expr.span) {
694 hir::ExprMethodCall(ref method_call, _, ref args) => {
696 // GET_UNWRAP needs to be checked before general `UNWRAP` lints
697 if let Some(arglists) = method_chain_args(expr, &["get", "unwrap"]) {
698 lint_get_unwrap(cx, expr, arglists[0], false);
699 } else if let Some(arglists) = method_chain_args(expr, &["get_mut", "unwrap"]) {
700 lint_get_unwrap(cx, expr, arglists[0], true);
701 } else if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
702 lint_unwrap(cx, expr, arglists[0]);
703 } else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
704 lint_ok_expect(cx, expr, arglists[0]);
705 } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
706 lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]);
707 } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
708 lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
709 } else if let Some(arglists) = method_chain_args(expr, &["map_or"]) {
710 lint_map_or_none(cx, expr, arglists[0]);
711 } else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
712 lint_filter_next(cx, expr, arglists[0]);
713 } else if let Some(arglists) = method_chain_args(expr, &["filter", "map"]) {
714 lint_filter_map(cx, expr, arglists[0], arglists[1]);
715 } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "map"]) {
716 lint_filter_map_map(cx, expr, arglists[0], arglists[1]);
717 } else if let Some(arglists) = method_chain_args(expr, &["filter", "flat_map"]) {
718 lint_filter_flat_map(cx, expr, arglists[0], arglists[1]);
719 } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "flat_map"]) {
720 lint_filter_map_flat_map(cx, expr, arglists[0], arglists[1]);
721 } else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
722 lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
723 } else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
724 lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
725 } else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
726 lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
727 } else if let Some(arglists) = method_chain_args(expr, &["extend"]) {
728 lint_extend(cx, expr, arglists[0]);
729 } else if let Some(arglists) = method_chain_args(expr, &["unwrap", "as_ptr"]) {
730 lint_cstring_as_ptr(cx, expr, &arglists[0][0], &arglists[1][0]);
731 } else if let Some(arglists) = method_chain_args(expr, &["iter", "nth"]) {
732 lint_iter_nth(cx, expr, arglists[0], false);
733 } else if let Some(arglists) = method_chain_args(expr, &["iter_mut", "nth"]) {
734 lint_iter_nth(cx, expr, arglists[0], true);
735 } else if method_chain_args(expr, &["skip", "next"]).is_some() {
736 lint_iter_skip_next(cx, expr);
737 } else if let Some(arglists) = method_chain_args(expr, &["cloned", "collect"]) {
738 lint_iter_cloned_collect(cx, expr, arglists[0]);
739 } else if let Some(arglists) = method_chain_args(expr, &["as_ref"]) {
740 lint_asref(cx, expr, "as_ref", arglists[0]);
741 } else if let Some(arglists) = method_chain_args(expr, &["as_mut"]) {
742 lint_asref(cx, expr, "as_mut", arglists[0]);
743 } else if let Some(arglists) = method_chain_args(expr, &["fold"]) {
744 lint_unnecessary_fold(cx, expr, arglists[0]);
747 lint_or_fun_call(cx, expr, &method_call.name.as_str(), args);
749 let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
750 if args.len() == 1 && method_call.name == "clone" {
751 lint_clone_on_copy(cx, expr, &args[0], self_ty);
752 lint_clone_on_ref_ptr(cx, expr, &args[0]);
756 ty::TyRef(_, ty) if ty.ty.sty == ty::TyStr => for &(method, pos) in &PATTERN_METHODS {
757 if method_call.name == method && args.len() > pos {
758 lint_single_char_pattern(cx, expr, &args[pos]);
764 hir::ExprBinary(op, ref lhs, ref rhs) if op.node == hir::BiEq || op.node == hir::BiNe => {
765 let mut info = BinaryExprInfo {
769 eq: op.node == hir::BiEq,
771 lint_binary_expr_with_method_call(cx, &mut info);
777 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) {
778 if in_external_macro(cx, implitem.span) {
781 let name = implitem.name;
782 let parent = cx.tcx.hir.get_parent(implitem.id);
783 let item = cx.tcx.hir.expect_item(parent);
785 if let hir::ImplItemKind::Method(ref sig, id) = implitem.node;
786 if let Some(first_arg_ty) = sig.decl.inputs.get(0);
787 if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir.body(id)).next();
788 if let hir::ItemImpl(_, _, _, _, None, ref self_ty, _) = item.node;
790 if cx.access_levels.is_exported(implitem.id) {
791 // check missing trait implementations
792 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
793 if name == method_name &&
794 sig.decl.inputs.len() == n_args &&
795 out_type.matches(&sig.decl.output) &&
796 self_kind.matches(first_arg_ty, first_arg, self_ty, false, &implitem.generics) {
797 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
798 "defining a method called `{}` on this type; consider implementing \
799 the `{}` trait or choosing a less ambiguous name", name, trait_name));
804 // check conventions w.r.t. conversion method names and predicates
805 let def_id = cx.tcx.hir.local_def_id(item.id);
806 let ty = cx.tcx.type_of(def_id);
807 let is_copy = is_copy(cx, ty);
808 for &(ref conv, self_kinds) in &CONVENTIONS {
810 if conv.check(&name.as_str());
813 .any(|k| k.matches(first_arg_ty, first_arg, self_ty, is_copy, &implitem.generics));
815 let lint = if item.vis == hir::Visibility::Public {
816 WRONG_PUB_SELF_CONVENTION
818 WRONG_SELF_CONVENTION
823 &format!("methods called `{}` usually take {}; consider choosing a less \
827 .map(|k| k.description())
834 let ret_ty = return_ty(cx, implitem.id);
836 !ret_ty.walk().any(|t| same_tys(cx, t, ty)) {
840 "methods called `new` usually return `Self`");
847 /// Checks for the `OR_FUN_CALL` lint.
848 fn lint_or_fun_call(cx: &LateContext, expr: &hir::Expr, name: &str, args: &[hir::Expr]) {
849 /// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
850 fn check_unwrap_or_default(
854 self_expr: &hir::Expr,
863 if name == "unwrap_or" {
864 if let hir::ExprPath(ref qpath) = fun.node {
865 let path = &*last_path_segment(qpath).name.as_str();
867 if ["default", "new"].contains(&path) {
868 let arg_ty = cx.tables.expr_ty(arg);
869 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
875 if implements_trait(cx, arg_ty, default_trait_id, &[]) {
880 &format!("use of `{}` followed by a call to `{}`", name, path),
882 format!("{}.unwrap_or_default()", snippet(cx, self_expr.span, "_")),
893 /// Check for `*or(foo())`.
894 fn check_general_case(
898 self_expr: &hir::Expr,
903 // (path, fn_has_argument, methods, suffix)
904 let know_types: &[(&[_], _, &[_], _)] = &[
905 (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
906 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
907 (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
908 (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
911 // early check if the name is one we care about
912 if know_types.iter().all(|k| !k.2.contains(&name)) {
916 let span_replace_word = self_expr.span.with_lo(span.hi());
918 // don't lint for constant values
919 let owner_def = cx.tcx.hir.get_parent_did(arg.id);
920 let promotable = cx.tcx.rvalue_promotable_map(owner_def).contains(&arg.hir_id.local_id);
925 let self_ty = cx.tables.expr_ty(self_expr);
927 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
928 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0))
930 (fn_has_arguments, poss, suffix)
935 if !poss.contains(&name) {
939 let sugg: Cow<_> = match (fn_has_arguments, !or_has_args) {
940 (true, _) => format!("|_| {}", snippet(cx, arg.span, "..")).into(),
941 (false, false) => format!("|| {}", snippet(cx, arg.span, "..")).into(),
942 (false, true) => snippet(cx, fun_span, ".."),
948 &format!("use of `{}` followed by a function call", name),
950 format!(".{}_{}({})", name, suffix, sugg),
956 hir::ExprCall(ref fun, ref or_args) => {
957 let or_has_args = !or_args.is_empty();
958 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
959 check_general_case(cx, name, fun.span, &args[0], &args[1], or_has_args, expr.span);
962 hir::ExprMethodCall(_, span, ref or_args) => {
963 check_general_case(cx, name, span, &args[0], &args[1], !or_args.is_empty(), expr.span)
970 /// Checks for the `CLONE_ON_COPY` lint.
971 fn lint_clone_on_copy(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty) {
972 let ty = cx.tables.expr_ty(expr);
973 if let ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) = arg_ty.sty {
974 if let ty::TyRef(_, ty::TypeAndMut { ty: innermost, .. }) = inner.sty {
979 "using `clone` on a double-reference; \
980 this will copy the reference instead of cloning the inner type",
981 |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
982 let mut ty = innermost;
984 while let ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) = ty.sty {
988 let refs: String = iter::repeat('&').take(n + 1).collect();
989 let derefs: String = iter::repeat('*').take(n).collect();
990 let explicit = format!("{}{}::clone({})", refs, ty, snip);
991 db.span_suggestion(expr.span, "try dereferencing it", format!("{}({}{}).clone()", refs, derefs, snip.deref()));
992 db.span_suggestion(expr.span, "or try being explicit about what type to clone", explicit);
995 return; // don't report clone_on_copy
1001 if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
1002 if let ty::TyRef(..) = cx.tables.expr_ty(arg).sty {
1003 let parent = cx.tcx.hir.get_parent_node(expr.id);
1004 match cx.tcx.hir.get(parent) {
1005 hir::map::NodeExpr(parent) => match parent.node {
1006 // &*x is a nop, &x.clone() is not
1007 hir::ExprAddrOf(..) |
1008 // (*x).func() is useless, x.clone().func() can work in case func borrows mutably
1009 hir::ExprMethodCall(..) => return,
1012 hir::map::NodeStmt(stmt) => {
1013 if let hir::StmtDecl(ref decl, _) = stmt.node {
1014 if let hir::DeclLocal(ref loc) = decl.node {
1015 if let hir::PatKind::Ref(..) = loc.pat.node {
1016 // let ref y = *x borrows x, let ref y = x.clone() does not
1024 snip = Some(("try dereferencing it", format!("{}", snippet.deref())));
1026 snip = Some(("try removing the `clone` call", format!("{}", snippet)));
1031 span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
1032 if let Some((text, snip)) = snip {
1033 db.span_suggestion(expr.span, text, snip);
1039 fn lint_clone_on_ref_ptr(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr) {
1040 let (obj_ty, _) = walk_ptrs_ty_depth(cx.tables.expr_ty(arg));
1042 if let ty::TyAdt(_, subst) = obj_ty.sty {
1043 let caller_type = if match_type(cx, obj_ty, &paths::RC) {
1045 } else if match_type(cx, obj_ty, &paths::ARC) {
1047 } else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
1057 "using '.clone()' on a ref-counted pointer",
1059 format!("{}::<{}>::clone(&{})", caller_type, subst.type_at(0), snippet(cx, arg.span, "_")),
1065 fn lint_string_extend(cx: &LateContext, expr: &hir::Expr, args: &[hir::Expr]) {
1067 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
1068 let target = &arglists[0][0];
1069 let (self_ty, _) = walk_ptrs_ty_depth(cx.tables.expr_ty(target));
1070 let ref_str = if self_ty.sty == ty::TyStr {
1072 } else if match_type(cx, self_ty, &paths::STRING) {
1080 STRING_EXTEND_CHARS,
1082 "calling `.extend(_.chars())`",
1085 "{}.push_str({}{})",
1086 snippet(cx, args[0].span, "_"),
1088 snippet(cx, target.span, "_")
1094 fn lint_extend(cx: &LateContext, expr: &hir::Expr, args: &[hir::Expr]) {
1095 let (obj_ty, _) = walk_ptrs_ty_depth(cx.tables.expr_ty(&args[0]));
1096 if match_type(cx, obj_ty, &paths::STRING) {
1097 lint_string_extend(cx, expr, args);
1101 fn lint_cstring_as_ptr(cx: &LateContext, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
1103 if let hir::ExprCall(ref fun, ref args) = new.node;
1105 if let hir::ExprPath(ref path) = fun.node;
1106 if let Def::Method(did) = cx.tables.qpath_def(path, fun.hir_id);
1107 if match_def_path(cx.tcx, did, &paths::CSTRING_NEW);
1111 TEMPORARY_CSTRING_AS_PTR,
1113 "you are getting the inner pointer of a temporary `CString`",
1115 db.note("that pointer will be invalid outside this expression");
1116 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
1122 fn lint_iter_cloned_collect(cx: &LateContext, expr: &hir::Expr, iter_args: &[hir::Expr]) {
1123 if match_type(cx, cx.tables.expr_ty(expr), &paths::VEC)
1124 && derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some()
1128 ITER_CLONED_COLLECT,
1130 "called `cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
1136 fn lint_unnecessary_fold(cx: &LateContext, expr: &hir::Expr, fold_args: &[hir::Expr]) {
1137 // Check that this is a call to Iterator::fold rather than just some function called fold
1138 if !match_trait_method(cx, expr, &paths::ITERATOR) {
1142 assert!(fold_args.len() == 3,
1143 "Expected fold_args to have three entries - the receiver, the initial value and the closure");
1145 fn check_fold_with_op(
1147 fold_args: &[hir::Expr],
1149 replacement_method_name: &str,
1150 replacement_has_args: bool) {
1153 // Extract the body of the closure passed to fold
1154 if let hir::ExprClosure(_, _, body_id, _, _) = fold_args[2].node;
1155 let closure_body = cx.tcx.hir.body(body_id);
1156 let closure_expr = remove_blocks(&closure_body.value);
1158 // Check if the closure body is of the form `acc <op> some_expr(x)`
1159 if let hir::ExprBinary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.node;
1160 if bin_op.node == op;
1162 // Extract the names of the two arguments to the closure
1163 if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
1164 if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
1166 if match_var(&*left_expr, first_arg_ident);
1167 if replacement_has_args || match_var(&*right_expr, second_arg_ident);
1170 // Span containing `.fold(...)`
1171 let next_point = cx.sess().codemap().next_point(fold_args[0].span);
1172 let fold_span = next_point.with_hi(fold_args[2].span.hi() + BytePos(1));
1174 let sugg = if replacement_has_args {
1176 ".{replacement}(|{s}| {r})",
1177 replacement = replacement_method_name,
1178 s = second_arg_ident,
1179 r = snippet(cx, right_expr.span, "EXPR"),
1184 replacement = replacement_method_name,
1192 // TODO #2371 don't suggest e.g. .any(|x| f(x)) if we can suggest .any(f)
1193 "this `.fold` can be written more succinctly using another method",
1201 // Check if the first argument to .fold is a suitable literal
1202 match fold_args[1].node {
1203 hir::ExprLit(ref lit) => {
1205 ast::LitKind::Bool(false) => check_fold_with_op(
1206 cx, fold_args, hir::BinOp_::BiOr, "any", true
1208 ast::LitKind::Bool(true) => check_fold_with_op(
1209 cx, fold_args, hir::BinOp_::BiAnd, "all", true
1211 ast::LitKind::Int(0, _) => check_fold_with_op(
1212 cx, fold_args, hir::BinOp_::BiAdd, "sum", false
1214 ast::LitKind::Int(1, _) => check_fold_with_op(
1215 cx, fold_args, hir::BinOp_::BiMul, "product", false
1224 fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) {
1225 let mut_str = if is_mut { "_mut" } else { "" };
1226 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
1228 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC) {
1230 } else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
1233 return; // caller is not a type that we want to lint
1241 "called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
1248 fn lint_get_unwrap(cx: &LateContext, expr: &hir::Expr, get_args: &[hir::Expr], is_mut: bool) {
1249 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
1250 // because they do not implement `IndexMut`
1251 let expr_ty = cx.tables.expr_ty(&get_args[0]);
1252 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
1254 } else if match_type(cx, expr_ty, &paths::VEC) {
1256 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
1258 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
1260 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
1263 return; // caller is not a type that we want to lint
1266 let mut_str = if is_mut { "_mut" } else { "" };
1267 let borrow_str = if is_mut { "&mut " } else { "&" };
1273 "called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
1281 snippet(cx, get_args[0].span, "_"),
1282 snippet(cx, get_args[1].span, "_")
1287 fn lint_iter_skip_next(cx: &LateContext, expr: &hir::Expr) {
1288 // lint if caller of skip is an Iterator
1289 if match_trait_method(cx, expr, &paths::ITERATOR) {
1294 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`",
1299 fn derefs_to_slice(cx: &LateContext, expr: &hir::Expr, ty: Ty) -> Option<sugg::Sugg<'static>> {
1300 fn may_slice(cx: &LateContext, ty: Ty) -> bool {
1302 ty::TySlice(_) => true,
1303 ty::TyAdt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
1304 ty::TyAdt(..) => match_type(cx, ty, &paths::VEC),
1305 ty::TyArray(_, size) => const_to_u64(size) < 32,
1306 ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) => may_slice(cx, inner),
1311 if let hir::ExprMethodCall(ref path, _, ref args) = expr.node {
1312 if path.name == "iter" && may_slice(cx, cx.tables.expr_ty(&args[0])) {
1313 sugg::Sugg::hir_opt(cx, &args[0]).map(|sugg| sugg.addr())
1319 ty::TySlice(_) => sugg::Sugg::hir_opt(cx, expr),
1320 ty::TyAdt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => sugg::Sugg::hir_opt(cx, expr),
1321 ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) => if may_slice(cx, inner) {
1322 sugg::Sugg::hir_opt(cx, expr)
1331 /// lint use of `unwrap()` for `Option`s and `Result`s
1332 fn lint_unwrap(cx: &LateContext, expr: &hir::Expr, unwrap_args: &[hir::Expr]) {
1333 let (obj_ty, _) = walk_ptrs_ty_depth(cx.tables.expr_ty(&unwrap_args[0]));
1335 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1336 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1337 } else if match_type(cx, obj_ty, &paths::RESULT) {
1338 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1343 if let Some((lint, kind, none_value)) = mess {
1349 "used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1350 using expect() to provide a better panic \
1359 /// lint use of `ok().expect()` for `Result`s
1360 fn lint_ok_expect(cx: &LateContext, expr: &hir::Expr, ok_args: &[hir::Expr]) {
1361 // lint if the caller of `ok()` is a `Result`
1362 if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT) {
1363 let result_type = cx.tables.expr_ty(&ok_args[0]);
1364 if let Some(error_type) = get_error_type(cx, result_type) {
1365 if has_debug_impl(error_type, cx) {
1370 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`",
1377 /// lint use of `map().unwrap_or()` for `Option`s
1378 fn lint_map_unwrap_or(cx: &LateContext, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) {
1379 // lint if the caller of `map()` is an `Option`
1380 if match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION) {
1381 // get snippets for args to map() and unwrap_or()
1382 let map_snippet = snippet(cx, map_args[1].span, "..");
1383 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1385 // comparing the snippet from source to raw text ("None") below is safe
1386 // because we already have checked the type.
1387 let arg = if unwrap_snippet == "None" {
1392 let suggest = if unwrap_snippet == "None" {
1398 "called `map(f).unwrap_or({})` on an Option value. \
1399 This can be done more directly by calling `{}` instead",
1403 // lint, with note if neither arg is > 1 line and both map() and
1404 // unwrap_or() have the same span
1405 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1406 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1407 if same_span && !multiline {
1408 let suggest = if unwrap_snippet == "None" {
1409 format!("and_then({})", map_snippet)
1411 format!("map_or({}, {})", unwrap_snippet, map_snippet)
1414 "replace `map({}).unwrap_or({})` with `{}`",
1419 span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, ¬e);
1420 } else if same_span && multiline {
1421 span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
1426 /// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
1427 fn lint_map_unwrap_or_else<'a, 'tcx>(
1428 cx: &LateContext<'a, 'tcx>,
1429 expr: &'tcx hir::Expr,
1430 map_args: &'tcx [hir::Expr],
1431 unwrap_args: &'tcx [hir::Expr],
1433 // lint if the caller of `map()` is an `Option`
1434 let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
1435 let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
1436 if is_option || is_result {
1438 let msg = if is_option {
1439 "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1440 `map_or_else(g, f)` instead"
1442 "called `map(f).unwrap_or_else(g)` on a Result value. This can be done more directly by calling \
1443 `ok().map_or_else(g, f)` instead"
1445 // get snippets for args to map() and unwrap_or_else()
1446 let map_snippet = snippet(cx, map_args[1].span, "..");
1447 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1448 // lint, with note if neither arg is > 1 line and both map() and
1449 // unwrap_or_else() have the same span
1450 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1451 let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
1452 if same_span && !multiline {
1456 OPTION_MAP_UNWRAP_OR_ELSE
1458 RESULT_MAP_UNWRAP_OR_ELSE
1464 "replace `map({0}).unwrap_or_else({1})` with `{2}map_or_else({1}, {0})`",
1467 if is_result { "ok()." } else { "" }
1470 } else if same_span && multiline {
1474 OPTION_MAP_UNWRAP_OR_ELSE
1476 RESULT_MAP_UNWRAP_OR_ELSE
1485 /// lint use of `_.map_or(None, _)` for `Option`s
1486 fn lint_map_or_none<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, map_or_args: &'tcx [hir::Expr]) {
1487 if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
1488 // check if the first non-self argument to map_or() is None
1489 let map_or_arg_is_none = if let hir::Expr_::ExprPath(ref qpath) = map_or_args[1].node {
1490 match_qpath(qpath, &paths::OPTION_NONE)
1495 if map_or_arg_is_none {
1497 let msg = "called `map_or(None, f)` on an Option value. This can be done more directly by calling \
1498 `and_then(f)` instead";
1499 let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
1500 let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
1501 let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
1502 span_lint_and_then(cx, OPTION_MAP_OR_NONE, expr.span, msg, |db| {
1503 db.span_suggestion(expr.span, "try using and_then instead", hint);
1509 /// lint use of `filter().next()` for `Iterators`
1510 fn lint_filter_next<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, filter_args: &'tcx [hir::Expr]) {
1511 // lint if caller of `.filter().next()` is an Iterator
1512 if match_trait_method(cx, expr, &paths::ITERATOR) {
1513 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
1514 `.find(p)` instead.";
1515 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1516 if filter_snippet.lines().count() <= 1 {
1517 // add note if not multi-line
1524 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
1527 span_lint(cx, FILTER_NEXT, expr.span, msg);
1532 /// lint use of `filter().map()` for `Iterators`
1533 fn lint_filter_map<'a, 'tcx>(
1534 cx: &LateContext<'a, 'tcx>,
1535 expr: &'tcx hir::Expr,
1536 _filter_args: &'tcx [hir::Expr],
1537 _map_args: &'tcx [hir::Expr],
1539 // lint if caller of `.filter().map()` is an Iterator
1540 if match_trait_method(cx, expr, &paths::ITERATOR) {
1541 let msg = "called `filter(p).map(q)` on an `Iterator`. \
1542 This is more succinctly expressed by calling `.filter_map(..)` instead.";
1543 span_lint(cx, FILTER_MAP, expr.span, msg);
1547 /// lint use of `filter().map()` for `Iterators`
1548 fn lint_filter_map_map<'a, 'tcx>(
1549 cx: &LateContext<'a, 'tcx>,
1550 expr: &'tcx hir::Expr,
1551 _filter_args: &'tcx [hir::Expr],
1552 _map_args: &'tcx [hir::Expr],
1554 // lint if caller of `.filter().map()` is an Iterator
1555 if match_trait_method(cx, expr, &paths::ITERATOR) {
1556 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
1557 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
1558 span_lint(cx, FILTER_MAP, expr.span, msg);
1562 /// lint use of `filter().flat_map()` for `Iterators`
1563 fn lint_filter_flat_map<'a, 'tcx>(
1564 cx: &LateContext<'a, 'tcx>,
1565 expr: &'tcx hir::Expr,
1566 _filter_args: &'tcx [hir::Expr],
1567 _map_args: &'tcx [hir::Expr],
1569 // lint if caller of `.filter().flat_map()` is an Iterator
1570 if match_trait_method(cx, expr, &paths::ITERATOR) {
1571 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
1572 This is more succinctly expressed by calling `.flat_map(..)` \
1573 and filtering by returning an empty Iterator.";
1574 span_lint(cx, FILTER_MAP, expr.span, msg);
1578 /// lint use of `filter_map().flat_map()` for `Iterators`
1579 fn lint_filter_map_flat_map<'a, 'tcx>(
1580 cx: &LateContext<'a, 'tcx>,
1581 expr: &'tcx hir::Expr,
1582 _filter_args: &'tcx [hir::Expr],
1583 _map_args: &'tcx [hir::Expr],
1585 // lint if caller of `.filter_map().flat_map()` is an Iterator
1586 if match_trait_method(cx, expr, &paths::ITERATOR) {
1587 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
1588 This is more succinctly expressed by calling `.flat_map(..)` \
1589 and filtering by returning an empty Iterator.";
1590 span_lint(cx, FILTER_MAP, expr.span, msg);
1594 /// lint searching an Iterator followed by `is_some()`
1595 fn lint_search_is_some<'a, 'tcx>(
1596 cx: &LateContext<'a, 'tcx>,
1597 expr: &'tcx hir::Expr,
1598 search_method: &str,
1599 search_args: &'tcx [hir::Expr],
1600 is_some_args: &'tcx [hir::Expr],
1602 // lint if caller of search is an Iterator
1603 if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
1605 "called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
1606 expressed by calling `any()`.",
1609 let search_snippet = snippet(cx, search_args[1].span, "..");
1610 if search_snippet.lines().count() <= 1 {
1611 // add note if not multi-line
1618 &format!("replace `{0}({1}).is_some()` with `any({1})`", search_method, search_snippet),
1621 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
1626 /// Used for `lint_binary_expr_with_method_call`.
1627 #[derive(Copy, Clone)]
1628 struct BinaryExprInfo<'a> {
1629 expr: &'a hir::Expr,
1630 chain: &'a hir::Expr,
1631 other: &'a hir::Expr,
1635 /// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
1636 fn lint_binary_expr_with_method_call<'a, 'tcx: 'a>(cx: &LateContext<'a, 'tcx>, info: &mut BinaryExprInfo) {
1637 macro_rules! lint_with_both_lhs_and_rhs {
1638 ($func:ident, $cx:expr, $info:ident) => {
1639 if !$func($cx, $info) {
1640 ::std::mem::swap(&mut $info.chain, &mut $info.other);
1641 if $func($cx, $info) {
1648 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp, cx, info);
1649 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
1650 lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
1651 lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
1654 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_NEXT_CMP` lints.
1655 fn lint_chars_cmp<'a, 'tcx>(
1656 cx: &LateContext<'a, 'tcx>,
1657 info: &BinaryExprInfo,
1658 chain_methods: &[&str],
1659 lint: &'static Lint,
1663 if let Some(args) = method_chain_args(info.chain, chain_methods);
1664 if let hir::ExprCall(ref fun, ref arg_char) = info.other.node;
1665 if arg_char.len() == 1;
1666 if let hir::ExprPath(ref qpath) = fun.node;
1667 if let Some(segment) = single_segment_path(qpath);
1668 if segment.name == "Some";
1670 let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
1672 if self_ty.sty != ty::TyStr {
1676 span_lint_and_sugg(cx,
1679 &format!("you should use the `{}` method", suggest),
1681 format!("{}{}.{}({})",
1682 if info.eq { "" } else { "!" },
1683 snippet(cx, args[0][0].span, "_"),
1685 snippet(cx, arg_char[0].span, "_")));
1694 /// Checks for the `CHARS_NEXT_CMP` lint.
1695 fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo) -> bool {
1696 lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
1699 /// Checks for the `CHARS_LAST_CMP` lint.
1700 fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo) -> bool {
1701 if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_NEXT_CMP, "ends_with") {
1704 lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_NEXT_CMP, "ends_with")
1708 /// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
1709 fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
1710 cx: &LateContext<'a, 'tcx>,
1711 info: &BinaryExprInfo,
1712 chain_methods: &[&str],
1713 lint: &'static Lint,
1717 if let Some(args) = method_chain_args(info.chain, chain_methods);
1718 if let hir::ExprLit(ref lit) = info.other.node;
1719 if let ast::LitKind::Char(c) = lit.node;
1725 &format!("you should use the `{}` method", suggest),
1727 format!("{}{}.{}('{}')",
1728 if info.eq { "" } else { "!" },
1729 snippet(cx, args[0][0].span, "_"),
1741 /// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
1742 fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo) -> bool {
1743 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
1746 /// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
1747 fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo) -> bool {
1748 if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
1751 lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
1755 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
1756 fn lint_single_char_pattern<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr, arg: &'tcx hir::Expr) {
1757 let parent_item = cx.tcx.hir.get_parent(arg.id);
1758 let parent_def_id = cx.tcx.hir.local_def_id(parent_item);
1759 let substs = Substs::identity_for_item(cx.tcx, parent_def_id);
1760 if let Ok(&ty::Const {
1761 val: ConstVal::Str(r),
1763 }) = ConstContext::new(cx.tcx, cx.param_env.and(substs), cx.tables).eval(arg)
1766 let hint = snippet(cx, expr.span, "..").replace(&format!("\"{}\"", r), &format!("'{}'", r));
1769 SINGLE_CHAR_PATTERN,
1771 "single-character string constant used as pattern",
1773 db.span_suggestion(expr.span, "try using a char instead", hint);
1780 /// Checks for the `USELESS_ASREF` lint.
1781 fn lint_asref(cx: &LateContext, expr: &hir::Expr, call_name: &str, as_ref_args: &[hir::Expr]) {
1782 // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
1783 // check if the call is to the actual `AsRef` or `AsMut` trait
1784 if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
1785 // check if the type after `as_ref` or `as_mut` is the same as before
1786 let recvr = &as_ref_args[0];
1787 let rcv_ty = cx.tables.expr_ty(recvr);
1788 let res_ty = cx.tables.expr_ty(expr);
1789 let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
1790 let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
1791 if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
1796 &format!("this call to `{}` does nothing", call_name),
1798 snippet(cx, recvr.span, "_").into_owned(),
1804 /// Given a `Result<T, E>` type, return its error type (`E`).
1805 fn get_error_type<'a>(cx: &LateContext, ty: Ty<'a>) -> Option<Ty<'a>> {
1806 if let ty::TyAdt(_, substs) = ty.sty {
1807 if match_type(cx, ty, &paths::RESULT) {
1808 substs.types().nth(1)
1817 /// This checks whether a given type is known to implement Debug.
1818 fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
1819 match cx.tcx.lang_items().debug_trait() {
1820 Some(debug) => implements_trait(cx, ty, debug, &[]),
1827 StartsWith(&'static str),
1830 #[cfg_attr(rustfmt, rustfmt_skip)]
1831 const CONVENTIONS: [(Convention, &[SelfKind]); 6] = [
1832 (Convention::Eq("new"), &[SelfKind::No]),
1833 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
1834 (Convention::StartsWith("from_"), &[SelfKind::No]),
1835 (Convention::StartsWith("into_"), &[SelfKind::Value]),
1836 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
1837 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
1840 #[cfg_attr(rustfmt, rustfmt_skip)]
1841 const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
1842 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
1843 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
1844 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
1845 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
1846 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
1847 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
1848 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
1849 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
1850 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
1851 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
1852 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
1853 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
1854 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
1855 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
1856 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
1857 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
1858 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
1859 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
1860 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
1861 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
1862 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
1863 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
1864 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
1865 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
1866 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
1867 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
1868 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
1869 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
1870 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
1871 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
1874 #[cfg_attr(rustfmt, rustfmt_skip)]
1875 const PATTERN_METHODS: [(&str, usize); 17] = [
1883 ("split_terminator", 1),
1884 ("rsplit_terminator", 1),
1889 ("match_indices", 1),
1890 ("rmatch_indices", 1),
1891 ("trim_left_matches", 1),
1892 ("trim_right_matches", 1),
1896 #[derive(Clone, Copy, PartialEq, Debug)]
1910 allow_value_for_ref: bool,
1911 generics: &hir::Generics,
1913 // Self types in the HIR are desugared to explicit self types. So it will
1916 // where SomeType can be `Self` or an explicit impl self type (e.g. `Foo` if
1917 // the impl is on `Foo`)
1918 // Thus, we only need to test equality against the impl self type or if it is
1920 // `Self`. Furthermore, the only possible types for `self: ` are `&Self`,
1921 // `Self`, `&mut Self`,
1922 // and `Box<Self>`, including the equivalent types with `Foo`.
1924 let is_actually_self = |ty| is_self_ty(ty) || ty == self_ty;
1927 SelfKind::Value => is_actually_self(ty),
1928 SelfKind::Ref | SelfKind::RefMut => {
1929 if allow_value_for_ref && is_actually_self(ty) {
1933 hir::TyRptr(_, ref mt_ty) => {
1934 let mutability_match = if self == SelfKind::Ref {
1935 mt_ty.mutbl == hir::MutImmutable
1937 mt_ty.mutbl == hir::MutMutable
1939 is_actually_self(&mt_ty.ty) && mutability_match
1948 SelfKind::Value => false,
1949 SelfKind::Ref => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASREF_TRAIT),
1950 SelfKind::RefMut => is_as_ref_or_mut_trait(ty, self_ty, generics, &paths::ASMUT_TRAIT),
1951 SelfKind::No => true,
1956 fn description(&self) -> &'static str {
1958 SelfKind::Value => "self by value",
1959 SelfKind::Ref => "self by reference",
1960 SelfKind::RefMut => "self by mutable reference",
1961 SelfKind::No => "no self",
1966 fn is_as_ref_or_mut_trait(ty: &hir::Ty, self_ty: &hir::Ty, generics: &hir::Generics, name: &[&str]) -> bool {
1967 single_segment_ty(ty).map_or(false, |seg| {
1968 generics.ty_params().any(|param| {
1969 param.name == seg.name && param.bounds.iter().any(|bound| {
1970 if let hir::TyParamBound::TraitTyParamBound(ref ptr, ..) = *bound {
1971 let path = &ptr.trait_ref.path;
1972 match_path(path, name) && path.segments.last().map_or(false, |s| {
1973 if let Some(ref params) = s.parameters {
1974 if params.parenthesized {
1977 params.types.len() == 1
1978 && (is_self_ty(¶ms.types[0]) || is_ty(&*params.types[0], self_ty))
1992 fn is_ty(ty: &hir::Ty, self_ty: &hir::Ty) -> bool {
1993 match (&ty.node, &self_ty.node) {
1995 &hir::TyPath(hir::QPath::Resolved(_, ref ty_path)),
1996 &hir::TyPath(hir::QPath::Resolved(_, ref self_ty_path)),
2000 .map(|seg| seg.name)
2001 .eq(self_ty_path.segments.iter().map(|seg| seg.name)),
2006 fn single_segment_ty(ty: &hir::Ty) -> Option<&hir::PathSegment> {
2007 if let hir::TyPath(ref path) = ty.node {
2008 single_segment_path(path)
2015 fn check(&self, other: &str) -> bool {
2017 Convention::Eq(this) => this == other,
2018 Convention::StartsWith(this) => other.starts_with(this) && this != other,
2023 impl fmt::Display for Convention {
2024 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
2026 Convention::Eq(this) => this.fmt(f),
2027 Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
2032 #[derive(Clone, Copy)]
2041 fn matches(&self, ty: &hir::FunctionRetTy) -> bool {
2043 (&OutType::Unit, &hir::DefaultReturn(_)) => true,
2044 (&OutType::Unit, &hir::Return(ref ty)) if ty.node == hir::TyTup(vec![].into()) => true,
2045 (&OutType::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
2046 (&OutType::Any, &hir::Return(ref ty)) if ty.node != hir::TyTup(vec![].into()) => true,
2047 (&OutType::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyRptr(_, _)),
2053 fn is_bool(ty: &hir::Ty) -> bool {
2054 if let hir::TyPath(ref p) = ty.node {
2055 match_qpath(p, &["bool"])