3 use rustc::middle::const_val::ConstVal;
4 use rustc::middle::const_qualif::ConstQualif;
6 use rustc_const_eval::EvalHint::ExprTypeChecked;
7 use rustc_const_eval::eval_const_expr_partial;
10 use syntax::codemap::Span;
12 use utils::{get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, match_path,
13 match_trait_method, match_type, method_chain_args, return_ty, same_tys, snippet,
14 span_lint, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
15 use utils::MethodArgs;
22 /// **What it does:** Checks for `.unwrap()` calls on `Option`s.
24 /// **Why is this bad?** Usually it is better to handle the `None` case, or to
25 /// at least call `.expect(_)` with a more helpful message. Still, for a lot of
26 /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
27 /// `Allow` by default.
29 /// **Known problems:** None.
36 pub OPTION_UNWRAP_USED,
38 "using `Option.unwrap()`, which should at least get a better message using `expect()`"
41 /// **What it does:** Checks for `.unwrap()` calls on `Result`s.
43 /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err`
44 /// values. Normally, you want to implement more sophisticated error handling,
45 /// and propagate errors upwards with `try!`.
47 /// Even if you want to panic on errors, not all `Error`s implement good
48 /// messages on display. Therefore it may be beneficial to look at the places
49 /// where they may get displayed. Activate this lint to do just that.
51 /// **Known problems:** None.
58 pub RESULT_UNWRAP_USED,
60 "using `Result.unwrap()`, which might be better handled"
63 /// **What it does:** Checks for methods that should live in a trait
64 /// implementation of a `std` trait (see [llogiq's blog
65 /// post](http://llogiq.github.io/2015/07/30/traits.html) for further
66 /// information) instead of an inherent implementation.
68 /// **Why is this bad?** Implementing the traits improve ergonomics for users of
69 /// the code, often with very little cost. Also people seeing a `mul(...)` method
70 /// may expect `*` to work equally, so you should have good reason to disappoint
73 /// **Known problems:** None.
79 /// fn add(&self, other: &X) -> X { .. }
83 pub SHOULD_IMPLEMENT_TRAIT,
85 "defining a method that should be implementing a std trait"
88 /// **What it does:** Checks for methods with certain name prefixes and which
89 /// doesn't match how self is taken. The actual rules are:
91 /// |Prefix |`self` taken |
92 /// |-------|----------------------|
93 /// |`as_` |`&self` or `&mut self`|
96 /// |`is_` |`&self` or none |
99 /// **Why is this bad?** Consistency breeds readability. If you follow the
100 /// conventions, your users won't be surprised that they, e.g., need to supply a
101 /// mutable reference to a `as_..` function.
103 /// **Known problems:** None.
108 /// fn as_str(self) -> &str { .. }
112 pub WRONG_SELF_CONVENTION,
114 "defining a method named with an established prefix (like \"into_\") that takes \
115 `self` with the wrong convention"
118 /// **What it does:** This is the same as
119 /// [`wrong_self_convention`](#wrong_self_convention), but for public items.
121 /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
123 /// **Known problems:** Actually *renaming* the function may break clients if
124 /// the function is part of the public interface. In that case, be mindful of
125 /// the stability guarantees you've given your users.
130 /// pub fn as_str(self) -> &str { .. }
134 pub WRONG_PUB_SELF_CONVENTION,
136 "defining a public method named with an established prefix (like \"into_\") that takes \
137 `self` with the wrong convention"
140 /// **What it does:** Checks for usage of `ok().expect(..)`.
142 /// **Why is this bad?** Because you usually call `expect()` on the `Result`
143 /// directly to get a better error message.
145 /// **Known problems:** None.
149 /// x.ok().expect("why did I do this again?")
154 "using `ok().expect()`, which gives worse error messages than \
155 calling `expect` directly on the Result"
158 /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`.
160 /// **Why is this bad?** Readability, this can be written more concisely as
161 /// `_.map_or(_, _)`.
163 /// **Known problems:** None.
167 /// x.map(|a| a + 1).unwrap_or(0)
170 pub OPTION_MAP_UNWRAP_OR,
172 "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
176 /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
178 /// **Why is this bad?** Readability, this can be written more concisely as
179 /// `_.map_or_else(_, _)`.
181 /// **Known problems:** None.
185 /// x.map(|a| a + 1).unwrap_or_else(some_function)
188 pub OPTION_MAP_UNWRAP_OR_ELSE,
190 "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
194 /// **What it does:** Checks for usage of `_.filter(_).next()`.
196 /// **Why is this bad?** Readability, this can be written more concisely as
199 /// **Known problems:** None.
203 /// iter.filter(|x| x == 0).next()
208 "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
211 /// **What it does:** Checks for usage of `_.filter(_).map(_)`,
212 /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
214 /// **Why is this bad?** Readability, this can be written more concisely as a
215 /// single method call.
217 /// **Known problems:** Often requires a condition + Option/Iterator creation
218 /// inside the closure.
222 /// iter.filter(|x| x == 0).map(|x| x * 2)
227 "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can \
228 usually be written as a single method call"
231 /// **What it does:** Checks for an iterator search (such as `find()`,
232 /// `position()`, or `rposition()`) followed by a call to `is_some()`.
234 /// **Why is this bad?** Readability, this can be written more concisely as
237 /// **Known problems:** None.
241 /// iter.find(|x| x == 0).is_some()
246 "using an iterator search followed by `is_some()`, which is more succinctly \
247 expressed as a call to `any()`"
250 /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check
251 /// if it starts with a given char.
253 /// **Why is this bad?** Readability, this can be written more concisely as
254 /// `_.starts_with(_)`.
256 /// **Known problems:** None.
260 /// name.chars().next() == Some('_')
265 "using `.chars().next()` to check if a string starts with a char"
268 /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
269 /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
270 /// `unwrap_or_default` instead.
272 /// **Why is this bad?** The function will always be called and potentially
273 /// allocate an object acting as the default.
275 /// **Known problems:** If the function has side-effects, not calling it will
276 /// change the semantic of the program, but you shouldn't rely on that anyway.
280 /// foo.unwrap_or(String::new())
282 /// this can instead be written:
284 /// foo.unwrap_or_else(String::new)
288 /// foo.unwrap_or_default()
293 "using any `*or` method with a function call, which suggests `*or_else`"
296 /// **What it does:** Checks for usage of `.extend(s)` on a `Vec` to extend the
297 /// vector by a slice.
299 /// **Why is this bad?** Since Rust 1.6, the `extend_from_slice(_)` method is
300 /// stable and at least for now faster.
302 /// **Known problems:** None.
306 /// my_vec.extend(&xs)
309 pub EXTEND_FROM_SLICE,
311 "`.extend_from_slice(_)` is a faster way to extend a Vec by a slice"
314 /// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
316 /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
317 /// generics, not for using the `clone` method on a concrete type.
319 /// **Known problems:** None.
328 "using `clone` on a `Copy` type"
331 /// **What it does:** Checks for usage of `.clone()` on an `&&T`.
333 /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of
334 /// cloning the underlying `T`.
336 /// **Known problems:** None.
343 /// let z = y.clone();
344 /// println!("{:p} {:p}",*y, z); // prints out the same pointer
348 pub CLONE_DOUBLE_REF,
350 "using `clone` on `&&T`"
353 /// **What it does:** Checks for `new` not returning `Self`.
355 /// **Why is this bad?** As a convention, `new` methods are used to make a new
356 /// instance of a type.
358 /// **Known problems:** None.
363 /// fn new(..) -> NotAFoo {
370 "not returning `Self` in a `new` method"
373 /// **What it does:** Checks for string methods that receive a single-character
374 /// `str` as an argument, e.g. `_.split("x")`.
376 /// **Why is this bad?** Performing these methods using a `char` is faster than
379 /// **Known problems:** Does not catch multi-byte unicode characters.
382 /// `_.split("x")` could be `_.split('x')
384 pub SINGLE_CHAR_PATTERN,
386 "using a single-character str where a char could be used, e.g. \
390 /// **What it does:** Checks for getting the inner pointer of a temporary `CString`.
392 /// **Why is this bad?** The inner pointer of a `CString` is only valid as long
393 /// as the `CString` is alive.
395 /// **Known problems:** None.
399 /// let c_str = CString::new("foo").unwrap().as_ptr();
401 /// call_some_ffi_func(c_str);
404 /// Here `c_str` point to a freed address. The correct use would be:
406 /// let c_str = CString::new("foo").unwrap();
408 /// call_some_ffi_func(c_str.as_ptr());
412 pub TEMPORARY_CSTRING_AS_PTR,
414 "getting the inner pointer of a temporary `CString`"
417 /// **What it does:** Checks for use of `.iter().nth()` (and the related
418 /// `.iter_mut().nth()`) on standard library types with O(1) element access.
420 /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more
423 /// **Known problems:** None.
427 /// let some_vec = vec![0, 1, 2, 3];
428 /// let bad_vec = some_vec.iter().nth(3);
429 /// let bad_slice = &some_vec[..].iter().nth(3);
431 /// The correct use would be:
433 /// let some_vec = vec![0, 1, 2, 3];
434 /// let bad_vec = some_vec.get(3);
435 /// let bad_slice = &some_vec[..].get(3);
440 "using `.iter().nth()` on a standard library type with O(1) element access"
443 /// **What it does:** Checks for use of `.skip(x).next()` on iterators.
445 /// **Why is this bad?** `.nth(x)` is cleaner
447 /// **Known problems:** None.
451 /// let some_vec = vec![0, 1, 2, 3];
452 /// let bad_vec = some_vec.iter().skip(3).next();
453 /// let bad_slice = &some_vec[..].iter().skip(3).next();
455 /// The correct use would be:
457 /// let some_vec = vec![0, 1, 2, 3];
458 /// let bad_vec = some_vec.iter().nth(3);
459 /// let bad_slice = &some_vec[..].iter().nth(3);
464 "using `.skip(x).next()` on an iterator"
467 /// **What it does:** Checks for use of `.get().unwrap()` (or
468 /// `.get_mut().unwrap`) on a standard library type which implements `Index`
470 /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more
473 /// **Known problems:** None.
477 /// let some_vec = vec![0, 1, 2, 3];
478 /// let last = some_vec.get(3).unwrap();
479 /// *some_vec.get_mut(0).unwrap() = 1;
481 /// The correct use would be:
483 /// let some_vec = vec![0, 1, 2, 3];
484 /// let last = some_vec[3];
490 "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
493 /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a
494 /// `&str` or `String`.
496 /// **Why is this bad?** `.push_str(s)` is clearer and faster
498 /// **Known problems:** None.
503 /// let def = String::from("def");
504 /// let mut s = String::new();
505 /// s.extend(abc.chars());
506 /// s.extend(def.chars());
508 /// The correct use would be:
511 /// let def = String::from("def");
512 /// let mut s = String::new();
514 /// s.push_str(&def));
518 pub STRING_EXTEND_CHARS,
520 "using `x.extend(s.chars())` where s is a `&str` or `String`"
524 impl LintPass for Pass {
525 fn get_lints(&self) -> LintArray {
526 lint_array!(EXTEND_FROM_SLICE,
529 SHOULD_IMPLEMENT_TRAIT,
530 WRONG_SELF_CONVENTION,
531 WRONG_PUB_SELF_CONVENTION,
533 OPTION_MAP_UNWRAP_OR,
534 OPTION_MAP_UNWRAP_OR_ELSE,
542 TEMPORARY_CSTRING_AS_PTR,
552 impl LateLintPass for Pass {
553 #[allow(unused_attributes)]
554 // ^ required because `cyclomatic_complexity` attribute shows up as unused
555 #[cyclomatic_complexity = "30"]
556 fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
557 if in_macro(cx, expr.span) {
562 hir::ExprMethodCall(name, _, ref args) => {
564 // GET_UNWRAP needs to be checked before general `UNWRAP` lints
565 if let Some(arglists) = method_chain_args(expr, &["get", "unwrap"]) {
566 lint_get_unwrap(cx, expr, arglists[0], false);
567 } else if let Some(arglists) = method_chain_args(expr, &["get_mut", "unwrap"]) {
568 lint_get_unwrap(cx, expr, arglists[0], true);
569 } else if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
570 lint_unwrap(cx, expr, arglists[0]);
571 } else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
572 lint_ok_expect(cx, expr, arglists[0]);
573 } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
574 lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]);
575 } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
576 lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
577 } else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
578 lint_filter_next(cx, expr, arglists[0]);
579 } else if let Some(arglists) = method_chain_args(expr, &["filter", "map"]) {
580 lint_filter_map(cx, expr, arglists[0], arglists[1]);
581 } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "map"]) {
582 lint_filter_map_map(cx, expr, arglists[0], arglists[1]);
583 } else if let Some(arglists) = method_chain_args(expr, &["filter", "flat_map"]) {
584 lint_filter_flat_map(cx, expr, arglists[0], arglists[1]);
585 } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "flat_map"]) {
586 lint_filter_map_flat_map(cx, expr, arglists[0], arglists[1]);
587 } else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
588 lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
589 } else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
590 lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
591 } else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
592 lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
593 } else if let Some(arglists) = method_chain_args(expr, &["extend"]) {
594 lint_extend(cx, expr, arglists[0]);
595 } else if let Some(arglists) = method_chain_args(expr, &["unwrap", "as_ptr"]) {
596 lint_cstring_as_ptr(cx, expr, &arglists[0][0], &arglists[1][0]);
597 } else if let Some(arglists) = method_chain_args(expr, &["iter", "nth"]) {
598 lint_iter_nth(cx, expr, arglists[0], false);
599 } else if let Some(arglists) = method_chain_args(expr, &["iter_mut", "nth"]) {
600 lint_iter_nth(cx, expr, arglists[0], true);
601 } else if method_chain_args(expr, &["skip", "next"]).is_some() {
602 lint_iter_skip_next(cx, expr);
605 lint_or_fun_call(cx, expr, &name.node.as_str(), args);
607 let self_ty = cx.tcx.tables().expr_ty_adjusted(&args[0]);
608 if args.len() == 1 && name.node.as_str() == "clone" {
609 lint_clone_on_copy(cx, expr, &args[0], self_ty);
613 ty::TyRef(_, ty) if ty.ty.sty == ty::TyStr => {
614 for &(method, pos) in &PATTERN_METHODS {
615 if name.node.as_str() == method && args.len() > pos {
616 lint_single_char_pattern(cx, expr, &args[pos]);
623 hir::ExprBinary(op, ref lhs, ref rhs) if op.node == hir::BiEq || op.node == hir::BiNe => {
624 if !lint_chars_next(cx, expr, lhs, rhs, op.node == hir::BiEq) {
625 lint_chars_next(cx, expr, rhs, lhs, op.node == hir::BiEq);
632 fn check_impl_item(&mut self, cx: &LateContext, implitem: &hir::ImplItem) {
633 if in_external_macro(cx, implitem.span) {
636 let name = implitem.name;
637 let parent = cx.tcx.map.get_parent(implitem.id);
638 let item = cx.tcx.map.expect_item(parent);
640 let hir::ImplItemKind::Method(ref sig, _) = implitem.node,
641 let Some(explicit_self) = sig.decl.inputs.get(0).and_then(hir::Arg::to_self),
642 let hir::ItemImpl(_, _, _, None, _, _) = item.node,
644 // check missing trait implementations
645 for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
646 if name.as_str() == method_name &&
647 sig.decl.inputs.len() == n_args &&
648 out_type.matches(&sig.decl.output) &&
649 self_kind.matches(&explicit_self, false) {
650 span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
651 "defining a method called `{}` on this type; consider implementing \
652 the `{}` trait or choosing a less ambiguous name", name, trait_name));
656 // check conventions w.r.t. conversion method names and predicates
657 let ty = cx.tcx.item_type(cx.tcx.map.local_def_id(item.id));
658 let is_copy = is_copy(cx, ty, item.id);
659 for &(ref conv, self_kinds) in &CONVENTIONS {
661 conv.check(&name.as_str()),
662 let Some(explicit_self) = sig.decl.inputs.get(0).and_then(hir::Arg::to_self),
663 !self_kinds.iter().any(|k| k.matches(&explicit_self, is_copy)),
665 let lint = if item.vis == hir::Visibility::Public {
666 WRONG_PUB_SELF_CONVENTION
668 WRONG_SELF_CONVENTION
673 &format!("methods called `{}` usually take {}; consider choosing a less \
677 .map(|k| k.description())
683 let ret_ty = return_ty(cx, implitem.id);
684 if &name.as_str() == &"new" &&
685 !ret_ty.walk().any(|t| same_tys(cx, t, ty, implitem.id)) {
689 "methods called `new` usually return `Self`");
695 /// Checks for the `OR_FUN_CALL` lint.
696 fn lint_or_fun_call(cx: &LateContext, expr: &hir::Expr, name: &str, args: &[P<hir::Expr>]) {
697 /// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
698 fn check_unwrap_or_default(cx: &LateContext, name: &str, fun: &hir::Expr, self_expr: &hir::Expr, arg: &hir::Expr,
699 or_has_args: bool, span: Span)
705 if name == "unwrap_or" {
706 if let hir::ExprPath(_, ref path) = fun.node {
707 let path: &str = &path.segments
709 .expect("A path must have at least one segment")
713 if ["default", "new"].contains(&path) {
714 let arg_ty = cx.tcx.tables().expr_ty(arg);
715 let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) {
721 if implements_trait(cx, arg_ty, default_trait_id, Vec::new()) {
722 span_lint_and_then(cx,
725 &format!("use of `{}` followed by a call to `{}`", name, path),
727 db.span_suggestion(span, "try this",
728 format!("{}.unwrap_or_default()", snippet(cx, self_expr.span, "_")));
739 /// Check for `*or(foo())`.
740 fn check_general_case(cx: &LateContext, name: &str, fun: &hir::Expr, self_expr: &hir::Expr, arg: &hir::Expr, or_has_args: bool,
742 // don't lint for constant values
743 // FIXME: can we `expect` here instead of match?
744 if let Some(qualif) = cx.tcx.const_qualif_map.borrow().get(&arg.id) {
745 if !qualif.contains(ConstQualif::NOT_CONST) {
749 // (path, fn_has_argument, methods, suffix)
750 let know_types: &[(&[_], _, &[_], _)] = &[(&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
751 (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
754 &["map_or", "ok_or", "or", "unwrap_or"],
756 (&paths::RESULT, true, &["or", "unwrap_or"], "else")];
758 let self_ty = cx.tcx.tables().expr_ty(self_expr);
760 let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) =
761 know_types.iter().find(|&&i| match_type(cx, self_ty, i.0)) {
762 (fn_has_arguments, poss, suffix)
767 if !poss.contains(&name) {
771 let sugg: Cow<_> = match (fn_has_arguments, !or_has_args) {
772 (true, _) => format!("|_| {}", snippet(cx, arg.span, "..")).into(),
773 (false, false) => format!("|| {}", snippet(cx, arg.span, "..")).into(),
774 (false, true) => snippet(cx, fun.span, ".."),
777 span_lint_and_then(cx, OR_FUN_CALL, span, &format!("use of `{}` followed by a function call", name), |db| {
778 db.span_suggestion(span,
780 format!("{}.{}_{}({})", snippet(cx, self_expr.span, "_"), name, suffix, sugg));
785 if let hir::ExprCall(ref fun, ref or_args) = args[1].node {
786 let or_has_args = !or_args.is_empty();
787 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
788 check_general_case(cx, name, fun, &args[0], &args[1], or_has_args, expr.span);
794 /// Checks for the `CLONE_ON_COPY` lint.
795 fn lint_clone_on_copy(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr, arg_ty: ty::Ty) {
796 let ty = cx.tcx.tables().expr_ty(expr);
797 let parent = cx.tcx.map.get_parent(expr.id);
798 let parameter_environment = ty::ParameterEnvironment::for_item(cx.tcx, parent);
799 if let ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) = arg_ty.sty {
800 if let ty::TyRef(..) = inner.sty {
801 span_lint_and_then(cx,
804 "using `clone` on a double-reference; \
805 this will copy the reference instead of cloning the inner type",
806 |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
807 db.span_suggestion(expr.span, "try dereferencing it", format!("({}).clone()", snip.deref()));
809 return; // don't report clone_on_copy
813 if !ty.moves_by_default(cx.tcx.global_tcx(), ¶meter_environment, expr.span) {
814 span_lint_and_then(cx,
817 "using `clone` on a `Copy` type",
818 |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
819 if let ty::TyRef(..) = cx.tcx.tables().expr_ty(arg).sty {
820 db.span_suggestion(expr.span, "try dereferencing it", format!("{}", snip.deref()));
822 db.span_suggestion(expr.span, "try removing the `clone` call", format!("{}", snip));
828 fn lint_vec_extend(cx: &LateContext, expr: &hir::Expr, args: &MethodArgs) {
829 let arg_ty = cx.tcx.tables().expr_ty(&args[1]);
830 if let Some(slice) = derefs_to_slice(cx, &args[1], arg_ty) {
831 span_lint_and_then(cx, EXTEND_FROM_SLICE, expr.span, "use of `extend` to extend a Vec by a slice", |db| {
832 db.span_suggestion(expr.span,
834 format!("{}.extend_from_slice({})",
835 snippet(cx, args[0].span, "_"),
841 fn lint_string_extend(cx: &LateContext, expr: &hir::Expr, args: &MethodArgs) {
843 if let Some(arglists) = method_chain_args(arg, &["chars"]) {
844 let target = &arglists[0][0];
845 let (self_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(target));
846 let ref_str = if self_ty.sty == ty::TyStr {
848 } else if match_type(cx, self_ty, &paths::STRING) {
858 "calling `.extend(_.chars())`",
860 db.span_suggestion(expr.span, "try this",
861 format!("{}.push_str({}{})",
862 snippet(cx, args[0].span, "_"),
864 snippet(cx, target.span, "_")));
869 fn lint_extend(cx: &LateContext, expr: &hir::Expr, args: &MethodArgs) {
870 let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(&args[0]));
871 if match_type(cx, obj_ty, &paths::VEC) {
872 lint_vec_extend(cx, expr, args);
873 } else if match_type(cx, obj_ty, &paths::STRING) {
874 lint_string_extend(cx, expr, args);
878 fn lint_cstring_as_ptr(cx: &LateContext, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) {
880 let hir::ExprCall(ref fun, ref args) = new.node,
882 let hir::ExprPath(None, ref path) = fun.node,
883 match_path(path, &paths::CSTRING_NEW),
885 span_lint_and_then(cx, TEMPORARY_CSTRING_AS_PTR, expr.span,
886 "you are getting the inner pointer of a temporary `CString`",
888 db.note("that pointer will be invalid outside this expression");
889 db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
895 // Type of MethodArgs is potentially a Vec
896 fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &MethodArgs, is_mut: bool){
897 let mut_str = if is_mut { "_mut" } else {""};
898 let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tcx.tables().expr_ty(&iter_args[0])).is_some() {
901 else if match_type(cx, cx.tcx.tables().expr_ty(&iter_args[0]), &paths::VEC) {
904 else if match_type(cx, cx.tcx.tables().expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
908 return; // caller is not a type that we want to lint
915 &format!("called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
916 mut_str, caller_type)
920 fn lint_get_unwrap(cx: &LateContext, expr: &hir::Expr, get_args: &MethodArgs, is_mut: bool) {
921 // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap,
922 // because they do not implement `IndexMut`
923 let expr_ty = cx.tcx.tables().expr_ty(&get_args[0]);
924 let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
926 } else if match_type(cx, expr_ty, &paths::VEC) {
928 } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
930 } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
932 } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
935 return; // caller is not a type that we want to lint
938 let mut_str = if is_mut { "_mut" } else { "" };
939 let borrow_str = if is_mut { "&mut " } else { "&" };
944 &format!("called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
945 mut_str, caller_type),
950 format!("{}{}[{}]", borrow_str, snippet(cx, get_args[0].span, "_"),
951 snippet(cx, get_args[1].span, "_"))
957 fn lint_iter_skip_next(cx: &LateContext, expr: &hir::Expr){
958 // lint if caller of skip is an Iterator
959 if match_trait_method(cx, expr, &paths::ITERATOR) {
964 "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`"
969 fn derefs_to_slice(cx: &LateContext, expr: &hir::Expr, ty: ty::Ty) -> Option<sugg::Sugg<'static>> {
970 fn may_slice(cx: &LateContext, ty: ty::Ty) -> bool {
972 ty::TySlice(_) => true,
973 ty::TyAdt(..) => match_type(cx, ty, &paths::VEC),
974 ty::TyArray(_, size) => size < 32,
975 ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) |
976 ty::TyBox(inner) => may_slice(cx, inner),
981 if let hir::ExprMethodCall(name, _, ref args) = expr.node {
982 if &name.node.as_str() == &"iter" && may_slice(cx, cx.tcx.tables().expr_ty(&args[0])) {
983 sugg::Sugg::hir_opt(cx, &*args[0]).map(|sugg| {
991 ty::TySlice(_) => sugg::Sugg::hir_opt(cx, expr),
992 ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) |
993 ty::TyBox(inner) => {
994 if may_slice(cx, inner) {
995 sugg::Sugg::hir_opt(cx, expr)
1006 // Type of MethodArgs is potentially a Vec
1007 /// lint use of `unwrap()` for `Option`s and `Result`s
1008 fn lint_unwrap(cx: &LateContext, expr: &hir::Expr, unwrap_args: &MethodArgs) {
1009 let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(&unwrap_args[0]));
1011 let mess = if match_type(cx, obj_ty, &paths::OPTION) {
1012 Some((OPTION_UNWRAP_USED, "an Option", "None"))
1013 } else if match_type(cx, obj_ty, &paths::RESULT) {
1014 Some((RESULT_UNWRAP_USED, "a Result", "Err"))
1019 if let Some((lint, kind, none_value)) = mess {
1023 &format!("used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \
1024 using expect() to provide a better panic
1032 // Type of MethodArgs is potentially a Vec
1033 /// lint use of `ok().expect()` for `Result`s
1034 fn lint_ok_expect(cx: &LateContext, expr: &hir::Expr, ok_args: &MethodArgs) {
1035 // lint if the caller of `ok()` is a `Result`
1036 if match_type(cx, cx.tcx.tables().expr_ty(&ok_args[0]), &paths::RESULT) {
1037 let result_type = cx.tcx.tables().expr_ty(&ok_args[0]);
1038 if let Some(error_type) = get_error_type(cx, result_type) {
1039 if has_debug_impl(error_type, cx) {
1043 "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`");
1050 // Type of MethodArgs is potentially a Vec
1051 /// lint use of `map().unwrap_or()` for `Option`s
1052 fn lint_map_unwrap_or(cx: &LateContext, expr: &hir::Expr, map_args: &MethodArgs, unwrap_args: &MethodArgs) {
1053 // lint if the caller of `map()` is an `Option`
1054 if match_type(cx, cx.tcx.tables().expr_ty(&map_args[0]), &paths::OPTION) {
1056 let msg = "called `map(f).unwrap_or(a)` on an Option value. This can be done more directly by calling \
1057 `map_or(a, f)` instead";
1058 // get snippets for args to map() and unwrap_or()
1059 let map_snippet = snippet(cx, map_args[1].span, "..");
1060 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1061 // lint, with note if neither arg is > 1 line and both map() and
1062 // unwrap_or() have the same span
1063 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1064 let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id;
1065 if same_span && !multiline {
1066 span_note_and_lint(cx,
1067 OPTION_MAP_UNWRAP_OR,
1071 &format!("replace `map({0}).unwrap_or({1})` with `map_or({1}, {0})`",
1074 } else if same_span && multiline {
1075 span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
1081 // Type of MethodArgs is potentially a Vec
1082 /// lint use of `map().unwrap_or_else()` for `Option`s
1083 fn lint_map_unwrap_or_else(cx: &LateContext, expr: &hir::Expr, map_args: &MethodArgs, unwrap_args: &MethodArgs) {
1084 // lint if the caller of `map()` is an `Option`
1085 if match_type(cx, cx.tcx.tables().expr_ty(&map_args[0]), &paths::OPTION) {
1087 let msg = "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \
1088 `map_or_else(g, f)` instead";
1089 // get snippets for args to map() and unwrap_or_else()
1090 let map_snippet = snippet(cx, map_args[1].span, "..");
1091 let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
1092 // lint, with note if neither arg is > 1 line and both map() and
1093 // unwrap_or_else() have the same span
1094 let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
1095 let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id;
1096 if same_span && !multiline {
1097 span_note_and_lint(cx,
1098 OPTION_MAP_UNWRAP_OR_ELSE,
1102 &format!("replace `map({0}).unwrap_or_else({1})` with `with map_or_else({1}, {0})`",
1105 } else if same_span && multiline {
1106 span_lint(cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg);
1112 // Type of MethodArgs is potentially a Vec
1113 /// lint use of `filter().next()` for `Iterators`
1114 fn lint_filter_next(cx: &LateContext, expr: &hir::Expr, filter_args: &MethodArgs) {
1115 // lint if caller of `.filter().next()` is an Iterator
1116 if match_trait_method(cx, expr, &paths::ITERATOR) {
1117 let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling `.find(p)` \
1119 let filter_snippet = snippet(cx, filter_args[1].span, "..");
1120 if filter_snippet.lines().count() <= 1 {
1121 // add note if not multi-line
1122 span_note_and_lint(cx,
1127 &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet));
1129 span_lint(cx, FILTER_NEXT, expr.span, msg);
1134 // Type of MethodArgs is potentially a Vec
1135 /// lint use of `filter().map()` for `Iterators`
1136 fn lint_filter_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &MethodArgs, _map_args: &MethodArgs) {
1137 // lint if caller of `.filter().map()` is an Iterator
1138 if match_trait_method(cx, expr, &paths::ITERATOR) {
1139 let msg = "called `filter(p).map(q)` on an `Iterator`. \
1140 This is more succinctly expressed by calling `.filter_map(..)` instead.";
1141 span_lint(cx, FILTER_MAP, expr.span, msg);
1145 // Type of MethodArgs is potentially a Vec
1146 /// lint use of `filter().map()` for `Iterators`
1147 fn lint_filter_map_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &MethodArgs, _map_args: &MethodArgs) {
1148 // lint if caller of `.filter().map()` is an Iterator
1149 if match_trait_method(cx, expr, &paths::ITERATOR) {
1150 let msg = "called `filter_map(p).map(q)` on an `Iterator`. \
1151 This is more succinctly expressed by only calling `.filter_map(..)` instead.";
1152 span_lint(cx, FILTER_MAP, expr.span, msg);
1156 // Type of MethodArgs is potentially a Vec
1157 /// lint use of `filter().flat_map()` for `Iterators`
1158 fn lint_filter_flat_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &MethodArgs, _map_args: &MethodArgs) {
1159 // lint if caller of `.filter().flat_map()` is an Iterator
1160 if match_trait_method(cx, expr, &paths::ITERATOR) {
1161 let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \
1162 This is more succinctly expressed by calling `.flat_map(..)` \
1163 and filtering by returning an empty Iterator.";
1164 span_lint(cx, FILTER_MAP, expr.span, msg);
1168 // Type of MethodArgs is potentially a Vec
1169 /// lint use of `filter_map().flat_map()` for `Iterators`
1170 fn lint_filter_map_flat_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &MethodArgs, _map_args: &MethodArgs) {
1171 // lint if caller of `.filter_map().flat_map()` is an Iterator
1172 if match_trait_method(cx, expr, &paths::ITERATOR) {
1173 let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \
1174 This is more succinctly expressed by calling `.flat_map(..)` \
1175 and filtering by returning an empty Iterator.";
1176 span_lint(cx, FILTER_MAP, expr.span, msg);
1181 // Type of MethodArgs is potentially a Vec
1182 /// lint searching an Iterator followed by `is_some()`
1183 fn lint_search_is_some(cx: &LateContext, expr: &hir::Expr, search_method: &str, search_args: &MethodArgs,
1184 is_some_args: &MethodArgs) {
1185 // lint if caller of search is an Iterator
1186 if match_trait_method(cx, &*is_some_args[0], &paths::ITERATOR) {
1187 let msg = format!("called `is_some()` after searching an `Iterator` with {}. This is more succinctly expressed \
1188 by calling `any()`.",
1190 let search_snippet = snippet(cx, search_args[1].span, "..");
1191 if search_snippet.lines().count() <= 1 {
1192 // add note if not multi-line
1193 span_note_and_lint(cx,
1198 &format!("replace `{0}({1}).is_some()` with `any({1})`", search_method, search_snippet));
1200 span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
1205 /// Checks for the `CHARS_NEXT_CMP` lint.
1206 fn lint_chars_next(cx: &LateContext, expr: &hir::Expr, chain: &hir::Expr, other: &hir::Expr, eq: bool) -> bool {
1208 let Some(args) = method_chain_args(chain, &["chars", "next"]),
1209 let hir::ExprCall(ref fun, ref arg_char) = other.node,
1210 arg_char.len() == 1,
1211 let hir::ExprPath(None, ref path) = fun.node,
1212 path.segments.len() == 1 && path.segments[0].name.as_str() == "Some"
1214 let self_ty = walk_ptrs_ty(cx.tcx.tables().expr_ty_adjusted(&args[0][0]));
1216 if self_ty.sty != ty::TyStr {
1220 span_lint_and_then(cx,
1223 "you should use the `starts_with` method",
1225 let sugg = format!("{}{}.starts_with({})",
1226 if eq { "" } else { "!" },
1227 snippet(cx, args[0][0].span, "_"),
1228 snippet(cx, arg_char[0].span, "_")
1231 db.span_suggestion(expr.span, "like this", sugg);
1240 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
1241 fn lint_single_char_pattern(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr) {
1242 if let Ok(ConstVal::Str(r)) = eval_const_expr_partial(cx.tcx, arg, ExprTypeChecked, None) {
1244 let hint = snippet(cx, expr.span, "..").replace(&format!("\"{}\"", r), &format!("'{}'", r));
1245 span_lint_and_then(cx,
1246 SINGLE_CHAR_PATTERN,
1248 "single-character string constant used as pattern",
1250 db.span_suggestion(expr.span, "try using a char instead:", hint);
1256 /// Given a `Result<T, E>` type, return its error type (`E`).
1257 fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option<ty::Ty<'a>> {
1258 if let ty::TyAdt(_, substs) = ty.sty {
1259 if match_type(cx, ty, &paths::RESULT) {
1260 substs.types().nth(1)
1269 /// This checks whether a given type is known to implement Debug.
1270 fn has_debug_impl<'a, 'b>(ty: ty::Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
1271 match cx.tcx.lang_items.debug_trait() {
1272 Some(debug) => implements_trait(cx, ty, debug, Vec::new()),
1279 StartsWith(&'static str),
1282 #[cfg_attr(rustfmt, rustfmt_skip)]
1283 const CONVENTIONS: [(Convention, &'static [SelfKind]); 6] = [
1284 (Convention::Eq("new"), &[SelfKind::No]),
1285 (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
1286 (Convention::StartsWith("from_"), &[SelfKind::No]),
1287 (Convention::StartsWith("into_"), &[SelfKind::Value]),
1288 (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
1289 (Convention::StartsWith("to_"), &[SelfKind::Ref]),
1292 #[cfg_attr(rustfmt, rustfmt_skip)]
1293 const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30] = [
1294 ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
1295 ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
1296 ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
1297 ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
1298 ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
1299 ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
1300 ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
1301 ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
1302 ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
1303 ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
1304 ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
1305 ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
1306 ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
1307 ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
1308 ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
1309 ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
1310 ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
1311 ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
1312 ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
1313 ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
1314 ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
1315 ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
1316 ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
1317 ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
1318 ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
1319 ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
1320 ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
1321 ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
1322 ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
1323 ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
1326 #[cfg_attr(rustfmt, rustfmt_skip)]
1327 const PATTERN_METHODS: [(&'static str, usize); 17] = [
1335 ("split_terminator", 1),
1336 ("rsplit_terminator", 1),
1341 ("match_indices", 1),
1342 ("rmatch_indices", 1),
1343 ("trim_left_matches", 1),
1344 ("trim_right_matches", 1),
1348 #[derive(Clone, Copy)]
1357 fn matches(self, slf: &hir::ExplicitSelf, allow_value_for_ref: bool) -> bool {
1358 match (self, &slf.node) {
1359 (SelfKind::Value, &hir::SelfKind::Value(_)) |
1360 (SelfKind::Ref, &hir::SelfKind::Region(_, hir::Mutability::MutImmutable)) |
1361 (SelfKind::RefMut, &hir::SelfKind::Region(_, hir::Mutability::MutMutable)) => true,
1362 (SelfKind::Ref, &hir::SelfKind::Value(_)) |
1363 (SelfKind::RefMut, &hir::SelfKind::Value(_)) => allow_value_for_ref,
1364 (_, &hir::SelfKind::Explicit(ref ty, _)) => self.matches_explicit_type(ty, allow_value_for_ref),
1370 fn matches_explicit_type(self, ty: &hir::Ty, allow_value_for_ref: bool) -> bool {
1371 match (self, &ty.node) {
1372 (SelfKind::Value, &hir::TyPath(..)) |
1373 (SelfKind::Ref, &hir::TyRptr(_, hir::MutTy { mutbl: hir::Mutability::MutImmutable, .. })) |
1374 (SelfKind::RefMut, &hir::TyRptr(_, hir::MutTy { mutbl: hir::Mutability::MutMutable, .. })) => true,
1375 (SelfKind::Ref, &hir::TyPath(..)) |
1376 (SelfKind::RefMut, &hir::TyPath(..)) => allow_value_for_ref,
1381 fn description(&self) -> &'static str {
1383 SelfKind::Value => "self by value",
1384 SelfKind::Ref => "self by reference",
1385 SelfKind::RefMut => "self by mutable reference",
1386 SelfKind::No => "no self",
1392 fn check(&self, other: &str) -> bool {
1394 Convention::Eq(this) => this == other,
1395 Convention::StartsWith(this) => other.starts_with(this) && this != other,
1400 impl fmt::Display for Convention {
1401 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
1403 Convention::Eq(this) => this.fmt(f),
1404 Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
1409 #[derive(Clone, Copy)]
1418 fn matches(&self, ty: &hir::FunctionRetTy) -> bool {
1420 (&OutType::Unit, &hir::DefaultReturn(_)) => true,
1421 (&OutType::Unit, &hir::Return(ref ty)) if ty.node == hir::TyTup(vec![].into()) => true,
1422 (&OutType::Bool, &hir::Return(ref ty)) if is_bool(ty) => true,
1423 (&OutType::Any, &hir::Return(ref ty)) if ty.node != hir::TyTup(vec![].into()) => true,
1424 (&OutType::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyRptr(_, _)),
1430 fn is_bool(ty: &hir::Ty) -> bool {
1431 if let hir::TyPath(None, ref p) = ty.node {
1432 match_path(p, &["bool"])