1 use clippy_utils::consts::{constant, constant_full_int, miri_to_const, FullInt};
2 use clippy_utils::diagnostics::{
3 multispan_sugg, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
5 use clippy_utils::macros::{is_panic, root_macro_call};
6 use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
7 use clippy_utils::sugg::Sugg;
8 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, peel_mid_ty_refs};
9 use clippy_utils::visitors::is_local_used;
11 get_parent_expr, is_lang_ctor, is_lint_allowed, is_refutable, is_unit_expr, is_wild, meets_msrv, msrvs,
12 path_to_local, path_to_local_id, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns,
15 use clippy_utils::{higher, peel_blocks_with_stmt};
16 use clippy_utils::{paths, search_same, SpanlessEq, SpanlessHash};
17 use core::iter::{once, ExactSizeIterator};
18 use if_chain::if_chain;
19 use rustc_ast::ast::{Attribute, LitKind};
20 use rustc_errors::Applicability;
21 use rustc_hir::def::{CtorKind, DefKind, Res};
22 use rustc_hir::LangItem::{OptionNone, OptionSome};
24 self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, HirId, Local, MatchSource,
25 Mutability, Node, Pat, PatKind, PathSegment, QPath, RangeEnd, TyKind,
27 use rustc_hir::{HirIdMap, HirIdSet};
28 use rustc_lint::{LateContext, LateLintPass};
29 use rustc_middle::ty::{self, Ty, TyS, VariantDef};
30 use rustc_semver::RustcVersion;
31 use rustc_session::{declare_tool_lint, impl_lint_pass};
32 use rustc_span::source_map::{Span, Spanned};
33 use rustc_span::{sym, symbol::kw};
34 use std::cmp::{max, Ordering};
35 use std::collections::hash_map::Entry;
37 declare_clippy_lint! {
39 /// Checks for matches with a single arm where an `if let`
40 /// will usually suffice.
42 /// ### Why is this bad?
43 /// Just readability – `if let` nests less than a `match`.
47 /// # fn bar(stool: &str) {}
48 /// # let x = Some("abc");
51 /// Some(ref foo) => bar(foo),
56 /// if let Some(ref foo) = x {
60 #[clippy::version = "pre 1.29.0"]
63 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
66 declare_clippy_lint! {
68 /// Checks for matches with two arms where an `if let else` will
71 /// ### Why is this bad?
72 /// Just readability – `if let` nests less than a `match`.
74 /// ### Known problems
75 /// Personal style preferences may differ.
81 /// # fn bar(foo: &usize) {}
82 /// # let other_ref: usize = 1;
83 /// # let x: Option<&usize> = Some(&1);
85 /// Some(ref foo) => bar(foo),
86 /// _ => bar(&other_ref),
90 /// Using `if let` with `else`:
93 /// # fn bar(foo: &usize) {}
94 /// # let other_ref: usize = 1;
95 /// # let x: Option<&usize> = Some(&1);
96 /// if let Some(ref foo) = x {
102 #[clippy::version = "pre 1.29.0"]
103 pub SINGLE_MATCH_ELSE,
105 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
108 declare_clippy_lint! {
110 /// Checks for matches where all arms match a reference,
111 /// suggesting to remove the reference and deref the matched expression
112 /// instead. It also checks for `if let &foo = bar` blocks.
114 /// ### Why is this bad?
115 /// It just makes the code less readable. That reference
116 /// destructuring adds nothing to the code.
122 /// &A(ref y) => foo(y),
129 /// A(ref y) => foo(y),
134 #[clippy::version = "pre 1.29.0"]
137 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
140 declare_clippy_lint! {
142 /// Checks for matches where match expression is a `bool`. It
143 /// suggests to replace the expression with an `if...else` block.
145 /// ### Why is this bad?
146 /// It makes the code less readable.
152 /// let condition: bool = true;
153 /// match condition {
158 /// Use if/else instead:
162 /// let condition: bool = true;
169 #[clippy::version = "pre 1.29.0"]
172 "a `match` on a boolean expression instead of an `if..else` block"
175 declare_clippy_lint! {
177 /// Checks for overlapping match arms.
179 /// ### Why is this bad?
180 /// It is likely to be an error and if not, makes the code
187 /// 1..=10 => println!("1 ... 10"),
188 /// 5..=15 => println!("5 ... 15"),
192 #[clippy::version = "pre 1.29.0"]
193 pub MATCH_OVERLAPPING_ARM,
195 "a `match` with overlapping arms"
198 declare_clippy_lint! {
200 /// Checks for arm which matches all errors with `Err(_)`
201 /// and take drastic actions like `panic!`.
203 /// ### Why is this bad?
204 /// It is generally a bad practice, similar to
205 /// catching all exceptions in java with `catch(Exception)`
209 /// let x: Result<i32, &str> = Ok(3);
211 /// Ok(_) => println!("ok"),
212 /// Err(_) => panic!("err"),
215 #[clippy::version = "pre 1.29.0"]
216 pub MATCH_WILD_ERR_ARM,
218 "a `match` with `Err(_)` arm and take drastic actions"
221 declare_clippy_lint! {
223 /// Checks for match which is used to add a reference to an
226 /// ### Why is this bad?
227 /// Using `as_ref()` or `as_mut()` instead is shorter.
231 /// let x: Option<()> = None;
234 /// let r: Option<&()> = match x {
236 /// Some(ref v) => Some(v),
240 /// let r: Option<&()> = x.as_ref();
242 #[clippy::version = "pre 1.29.0"]
245 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
248 declare_clippy_lint! {
250 /// Checks for wildcard enum matches using `_`.
252 /// ### Why is this bad?
253 /// New enum variants added by library updates can be missed.
255 /// ### Known problems
256 /// Suggested replacements may be incorrect if guards exhaustively cover some
257 /// variants, and also may not use correct path to enum if it's not present in the current scope.
261 /// # enum Foo { A(usize), B(usize) }
262 /// # let x = Foo::B(1);
275 #[clippy::version = "1.34.0"]
276 pub WILDCARD_ENUM_MATCH_ARM,
278 "a wildcard enum match arm using `_`"
281 declare_clippy_lint! {
283 /// Checks for wildcard enum matches for a single variant.
285 /// ### Why is this bad?
286 /// New enum variants added by library updates can be missed.
288 /// ### Known problems
289 /// Suggested replacements may not use correct path to enum
290 /// if it's not present in the current scope.
294 /// # enum Foo { A, B, C }
295 /// # let x = Foo::B;
310 #[clippy::version = "1.45.0"]
311 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
313 "a wildcard enum match for a single variant"
316 declare_clippy_lint! {
318 /// Checks for wildcard pattern used with others patterns in same match arm.
320 /// ### Why is this bad?
321 /// Wildcard pattern already covers any other pattern as it will match anyway.
322 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
338 #[clippy::version = "1.42.0"]
339 pub WILDCARD_IN_OR_PATTERNS,
341 "a wildcard pattern used with others patterns in same match arm"
344 declare_clippy_lint! {
346 /// Checks for matches being used to destructure a single-variant enum
347 /// or tuple struct where a `let` will suffice.
349 /// ### Why is this bad?
350 /// Just readability – `let` doesn't nest, whereas a `match` does.
358 /// let wrapper = Wrapper::Data(42);
360 /// let data = match wrapper {
361 /// Wrapper::Data(i) => i,
365 /// The correct use would be:
371 /// let wrapper = Wrapper::Data(42);
372 /// let Wrapper::Data(data) = wrapper;
374 #[clippy::version = "pre 1.29.0"]
375 pub INFALLIBLE_DESTRUCTURING_MATCH,
377 "a `match` statement with a single infallible arm instead of a `let`"
380 declare_clippy_lint! {
382 /// Checks for useless match that binds to only one value.
384 /// ### Why is this bad?
385 /// Readability and needless complexity.
387 /// ### Known problems
388 /// Suggested replacements may be incorrect when `match`
389 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
404 /// let (c, d) = (a, b);
406 #[clippy::version = "1.43.0"]
407 pub MATCH_SINGLE_BINDING,
409 "a match with a single binding instead of using `let` statement"
412 declare_clippy_lint! {
414 /// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
416 /// ### Why is this bad?
417 /// Correctness and readability. It's like having a wildcard pattern after
418 /// matching all enum variants explicitly.
422 /// # struct A { a: i32 }
423 /// let a = A { a: 5 };
427 /// A { a: 5, .. } => {},
433 /// A { a: 5 } => {},
437 #[clippy::version = "1.43.0"]
438 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
440 "a match on a struct that binds all fields but still uses the wildcard pattern"
443 declare_clippy_lint! {
445 /// Lint for redundant pattern matching over `Result`, `Option`,
446 /// `std::task::Poll` or `std::net::IpAddr`
448 /// ### Why is this bad?
449 /// It's more concise and clear to just use the proper
452 /// ### Known problems
453 /// This will change the drop order for the matched type. Both `if let` and
454 /// `while let` will drop the value at the end of the block, both `if` and `while` will drop the
455 /// value before entering the block. For most types this change will not matter, but for a few
456 /// types this will not be an acceptable change (e.g. locks). See the
457 /// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about
462 /// # use std::task::Poll;
463 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
464 /// if let Ok(_) = Ok::<i32, i32>(42) {}
465 /// if let Err(_) = Err::<i32, i32>(42) {}
466 /// if let None = None::<()> {}
467 /// if let Some(_) = Some(42) {}
468 /// if let Poll::Pending = Poll::Pending::<()> {}
469 /// if let Poll::Ready(_) = Poll::Ready(42) {}
470 /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
471 /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
472 /// match Ok::<i32, i32>(42) {
478 /// The more idiomatic use would be:
481 /// # use std::task::Poll;
482 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
483 /// if Ok::<i32, i32>(42).is_ok() {}
484 /// if Err::<i32, i32>(42).is_err() {}
485 /// if None::<()>.is_none() {}
486 /// if Some(42).is_some() {}
487 /// if Poll::Pending::<()>.is_pending() {}
488 /// if Poll::Ready(42).is_ready() {}
489 /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
490 /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
491 /// Ok::<i32, i32>(42).is_ok();
493 #[clippy::version = "1.31.0"]
494 pub REDUNDANT_PATTERN_MATCHING,
496 "use the proper utility function avoiding an `if let`"
499 declare_clippy_lint! {
501 /// Checks for `match` or `if let` expressions producing a
502 /// `bool` that could be written using `matches!`
504 /// ### Why is this bad?
505 /// Readability and needless complexity.
507 /// ### Known problems
508 /// This lint falsely triggers, if there are arms with
509 /// `cfg` attributes that remove an arm evaluating to `false`.
516 /// let a = match x {
521 /// let a = if let Some(0) = x {
528 /// let a = matches!(x, Some(0));
530 #[clippy::version = "1.47.0"]
531 pub MATCH_LIKE_MATCHES_MACRO,
533 "a match that could be written with the matches! macro"
536 declare_clippy_lint! {
538 /// Checks for `match` with identical arm bodies.
540 /// ### Why is this bad?
541 /// This is probably a copy & paste error. If arm bodies
542 /// are the same on purpose, you can factor them
543 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
545 /// ### Known problems
546 /// False positive possible with order dependent `match`
548 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
555 /// Baz => bar(), // <= oops
559 /// This should probably be
564 /// Baz => baz(), // <= fixed
568 /// or if the original code was not a typo:
571 /// Bar | Baz => bar(), // <= shows the intent better
575 #[clippy::version = "pre 1.29.0"]
578 "`match` with identical arm bodies"
583 msrv: Option<RustcVersion>,
584 infallible_destructuring_match_linted: bool,
589 pub fn new(msrv: Option<RustcVersion>) -> Self {
597 impl_lint_pass!(Matches => [
602 MATCH_OVERLAPPING_ARM,
605 WILDCARD_ENUM_MATCH_ARM,
606 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
607 WILDCARD_IN_OR_PATTERNS,
608 MATCH_SINGLE_BINDING,
609 INFALLIBLE_DESTRUCTURING_MATCH,
610 REST_PAT_IN_FULLY_BOUND_STRUCTS,
611 REDUNDANT_PATTERN_MATCHING,
612 MATCH_LIKE_MATCHES_MACRO,
616 impl<'tcx> LateLintPass<'tcx> for Matches {
617 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
618 if expr.span.from_expansion() {
622 redundant_pattern_match::check(cx, expr);
624 if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) {
625 if !check_match_like_matches(cx, expr) {
626 lint_match_arms(cx, expr);
629 lint_match_arms(cx, expr);
632 if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
633 check_single_match(cx, ex, arms, expr);
634 check_match_bool(cx, ex, arms, expr);
635 check_overlapping_arms(cx, ex, arms);
636 check_wild_err_arm(cx, ex, arms);
637 check_wild_enum_match(cx, ex, arms);
638 check_match_as_ref(cx, ex, arms, expr);
639 check_wild_in_or_pats(cx, arms);
641 if self.infallible_destructuring_match_linted {
642 self.infallible_destructuring_match_linted = false;
644 check_match_single_binding(cx, ex, arms, expr);
647 if let ExprKind::Match(ex, arms, _) = expr.kind {
648 check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr);
652 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
654 if !local.span.from_expansion();
655 if let Some(expr) = local.init;
656 if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
657 if arms.len() == 1 && arms[0].guard.is_none();
658 if let PatKind::TupleStruct(
659 QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
661 if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
662 let body = peel_blocks(arms[0].body);
663 if path_to_local_id(body, arg);
666 let mut applicability = Applicability::MachineApplicable;
667 self.infallible_destructuring_match_linted = true;
670 INFALLIBLE_DESTRUCTURING_MATCH,
672 "you seem to be trying to use `match` to destructure a single infallible pattern. \
673 Consider using `let`",
677 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
678 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
679 snippet_with_applicability(cx, target.span, "..", &mut applicability),
687 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
689 if !pat.span.from_expansion();
690 if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
691 if let Some(def_id) = path.res.opt_def_id();
692 let ty = cx.tcx.type_of(def_id);
693 if let ty::Adt(def, _) = ty.kind();
694 if def.is_struct() || def.is_union();
695 if fields.len() == def.non_enum_variant().fields.len();
700 REST_PAT_IN_FULLY_BOUND_STRUCTS,
702 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
704 "consider removing `..` from this binding",
710 extract_msrv_attr!(LateContext);
714 fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
715 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
716 if expr.span.from_expansion() {
717 // Don't lint match expressions present in
718 // macro_rules! block
721 if let PatKind::Or(..) = arms[0].pat.kind {
722 // don't lint for or patterns for now, this makes
723 // the lint noisy in unnecessary situations
726 let els = arms[1].body;
727 let els = if is_unit_expr(peel_blocks(els)) {
729 } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
730 if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
731 // single statement/expr "else" block, don't lint
734 // block with 2+ statements or 1 expr and 1+ statement
737 // not a block, don't lint
741 let ty = cx.typeck_results().expr_ty(ex);
742 if *ty.kind() != ty::Bool || is_lint_allowed(cx, MATCH_BOOL, ex.hir_id) {
743 check_single_match_single_pattern(cx, ex, arms, expr, els);
744 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
749 fn check_single_match_single_pattern(
750 cx: &LateContext<'_>,
754 els: Option<&Expr<'_>>,
756 if is_wild(arms[1].pat) {
757 report_single_match_single_pattern(cx, ex, arms, expr, els);
761 fn report_single_match_single_pattern(
762 cx: &LateContext<'_>,
766 els: Option<&Expr<'_>>,
768 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
769 let els_str = els.map_or(String::new(), |els| {
770 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
773 let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat);
774 let (msg, sugg) = if_chain! {
775 if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind;
776 let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex));
777 if let Some(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait();
778 if let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait();
779 if ty.is_integral() || ty.is_char() || ty.is_str()
780 || (implements_trait(cx, ty, spe_trait_id, &[])
781 && implements_trait(cx, ty, pe_trait_id, &[ty.into()]));
783 // scrutinee derives PartialEq and the pattern is a constant.
784 let pat_ref_count = match pat.kind {
785 // string literals are already a reference.
786 PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1,
789 // References are only implicitly added to the pattern, so no overflow here.
790 // e.g. will work: match &Some(_) { Some(_) => () }
791 // will not: match Some(_) { &Some(_) => () }
792 let ref_count_diff = ty_ref_count - pat_ref_count;
794 // Try to remove address of expressions first.
795 let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff);
796 let ref_count_diff = ref_count_diff - removed;
798 let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`";
800 "if {} == {}{} {}{}",
801 snippet(cx, ex.span, ".."),
802 // PartialEq for different reference counts may not exist.
803 "&".repeat(ref_count_diff),
804 snippet(cx, arms[0].pat.span, ".."),
805 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
810 let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`";
812 "if let {} = {} {}{}",
813 snippet(cx, arms[0].pat.span, ".."),
814 snippet(cx, ex.span, ".."),
815 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
829 Applicability::HasPlaceholders,
833 fn check_single_match_opt_like<'a>(
834 cx: &LateContext<'a>,
839 els: Option<&Expr<'_>>,
841 // list of candidate `Enum`s we know will never get any more members
843 (&paths::COW, "Borrowed"),
844 (&paths::COW, "Cow::Borrowed"),
845 (&paths::COW, "Cow::Owned"),
846 (&paths::COW, "Owned"),
847 (&paths::OPTION, "None"),
848 (&paths::RESULT, "Err"),
849 (&paths::RESULT, "Ok"),
852 // We want to suggest to exclude an arm that contains only wildcards or forms the exhaustive
853 // match with the second branch, without enum variants in matches.
854 if !contains_only_wilds(arms[1].pat) && !form_exhaustive_matches(arms[0].pat, arms[1].pat) {
858 let mut paths_and_types = Vec::new();
859 if !collect_pat_paths(&mut paths_and_types, cx, arms[1].pat, ty) {
863 let in_candidate_enum = |path_info: &(String, &TyS<'_>)| -> bool {
864 let (path, ty) = path_info;
865 for &(ty_path, pat_path) in candidates {
866 if path == pat_path && match_type(cx, ty, ty_path) {
872 if paths_and_types.iter().all(in_candidate_enum) {
873 report_single_match_single_pattern(cx, ex, arms, expr, els);
877 /// Collects paths and their types from the given patterns. Returns true if the given pattern could
878 /// be simplified, false otherwise.
879 fn collect_pat_paths<'a>(acc: &mut Vec<(String, Ty<'a>)>, cx: &LateContext<'a>, pat: &Pat<'_>, ty: Ty<'a>) -> bool {
881 PatKind::Wild => true,
882 PatKind::Tuple(inner, _) => inner.iter().all(|p| {
883 let p_ty = cx.typeck_results().pat_ty(p);
884 collect_pat_paths(acc, cx, p, p_ty)
886 PatKind::TupleStruct(ref path, ..) => {
887 let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
888 s.print_qpath(path, false);
890 acc.push((path, ty));
893 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => {
894 acc.push((ident.to_string(), ty));
897 PatKind::Path(ref path) => {
898 let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
899 s.print_qpath(path, false);
901 acc.push((path, ty));
908 /// Returns true if the given arm of pattern matching contains wildcard patterns.
909 fn contains_only_wilds(pat: &Pat<'_>) -> bool {
911 PatKind::Wild => true,
912 PatKind::Tuple(inner, _) | PatKind::TupleStruct(_, inner, ..) => inner.iter().all(contains_only_wilds),
917 /// Returns true if the given patterns forms only exhaustive matches that don't contain enum
918 /// patterns without a wildcard.
919 fn form_exhaustive_matches(left: &Pat<'_>, right: &Pat<'_>) -> bool {
920 match (&left.kind, &right.kind) {
921 (PatKind::Wild, _) | (_, PatKind::Wild) => true,
922 (PatKind::Tuple(left_in, left_pos), PatKind::Tuple(right_in, right_pos)) => {
923 // We don't actually know the position and the presence of the `..` (dotdot) operator
924 // in the arms, so we need to evaluate the correct offsets here in order to iterate in
925 // both arms at the same time.
928 if left_pos.is_some() { 1 } else { 0 }
931 if right_pos.is_some() { 1 } else { 0 }
934 let mut left_pos = left_pos.unwrap_or(usize::MAX);
935 let mut right_pos = right_pos.unwrap_or(usize::MAX);
936 let mut left_dot_space = 0;
937 let mut right_dot_space = 0;
939 let mut found_dotdot = false;
942 if left_dot_space < len - left_in.len() {
948 right_dot_space += 1;
949 if right_dot_space < len - right_in.len() {
957 if !contains_only_wilds(&left_in[i - left_dot_space])
958 && !contains_only_wilds(&right_in[i - right_dot_space])
969 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
970 // Type of expression is `bool`.
971 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
976 "you seem to be trying to match on a boolean expression",
980 let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
981 if let ExprKind::Lit(ref lit) = arm_bool.kind {
983 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
984 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
994 if let Some((true_expr, false_expr)) = exprs {
995 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
996 (false, false) => Some(format!(
998 snippet(cx, ex.span, "b"),
999 expr_block(cx, true_expr, None, "..", Some(expr.span)),
1000 expr_block(cx, false_expr, None, "..", Some(expr.span))
1002 (false, true) => Some(format!(
1004 snippet(cx, ex.span, "b"),
1005 expr_block(cx, true_expr, None, "..", Some(expr.span))
1008 let test = Sugg::hir(cx, ex, "..");
1012 expr_block(cx, false_expr, None, "..", Some(expr.span))
1015 (true, true) => None,
1018 if let Some(sugg) = sugg {
1019 diag.span_suggestion(
1021 "consider using an `if`/`else` expression",
1023 Applicability::HasPlaceholders,
1033 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
1034 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
1035 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
1036 if !ranges.is_empty() {
1037 if let Some((start, end)) = overlapping(&ranges) {
1040 MATCH_OVERLAPPING_ARM,
1042 "some ranges overlap",
1044 "overlaps with this",
1051 fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
1052 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
1053 if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
1055 if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
1056 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
1057 if path_str == "Err" {
1058 let mut matching_wild = inner.iter().any(is_wild);
1059 let mut ident_bind_name = kw::Underscore;
1061 // Looking for unused bindings (i.e.: `_e`)
1062 for pat in inner.iter() {
1063 if let PatKind::Binding(_, id, ident, None) = pat.kind {
1064 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
1065 ident_bind_name = ident.name;
1066 matching_wild = true;
1073 if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
1074 if is_panic(cx, macro_call.def_id);
1076 // `Err(_)` or `Err(_e)` arm with `panic!` found
1077 span_lint_and_note(cx,
1080 &format!("`Err({})` matches all errors", ident_bind_name),
1082 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
1092 enum CommonPrefixSearcher<'a> {
1094 Path(&'a [PathSegment<'a>]),
1097 impl<'a> CommonPrefixSearcher<'a> {
1098 fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
1100 [path @ .., _] => self.with_prefix(path),
1105 fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
1107 Self::None => *self = Self::Path(path),
1108 Self::Path(self_path)
1111 .map(|p| p.ident.name)
1112 .eq(self_path.iter().map(|p| p.ident.name)) => {},
1113 Self::Path(_) => *self = Self::Mixed,
1119 fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
1120 let attrs = cx.tcx.get_attrs(variant_def.def_id);
1121 clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
1124 #[allow(clippy::too_many_lines)]
1125 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
1126 let ty = cx.typeck_results().expr_ty(ex).peel_refs();
1127 let adt_def = match ty.kind() {
1129 if adt_def.is_enum()
1130 && !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
1137 // First pass - check for violation, but don't do much book-keeping because this is hopefully
1138 // the uncommon case, and the book-keeping is slightly expensive.
1139 let mut wildcard_span = None;
1140 let mut wildcard_ident = None;
1141 let mut has_non_wild = false;
1143 match peel_hir_pat_refs(arm.pat).0.kind {
1144 PatKind::Wild => wildcard_span = Some(arm.pat.span),
1145 PatKind::Binding(_, _, ident, None) => {
1146 wildcard_span = Some(arm.pat.span);
1147 wildcard_ident = Some(ident);
1149 _ => has_non_wild = true,
1152 let wildcard_span = match wildcard_span {
1153 Some(x) if has_non_wild => x,
1157 // Accumulate the variants which should be put in place of the wildcard because they're not
1159 let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
1160 let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
1162 let mut path_prefix = CommonPrefixSearcher::None;
1164 // Guards mean that this case probably isn't exhaustively covered. Technically
1165 // this is incorrect, as we should really check whether each variant is exhaustively
1166 // covered by the set of guards that cover it, but that's really hard to do.
1167 recurse_or_patterns(arm.pat, |pat| {
1168 let path = match &peel_hir_pat_refs(pat).0.kind {
1169 PatKind::Path(path) => {
1170 #[allow(clippy::match_same_arms)]
1171 let id = match cx.qpath_res(path, pat.hir_id) {
1173 DefKind::Const | DefKind::ConstParam | DefKind::AnonConst | DefKind::InlineConst,
1176 Res::Def(_, id) => id,
1179 if arm.guard.is_none() {
1180 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1184 PatKind::TupleStruct(path, patterns, ..) => {
1185 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1186 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
1187 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1192 PatKind::Struct(path, patterns, ..) => {
1193 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1194 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
1195 missing_variants.retain(|e| e.def_id != id);
1203 QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
1204 QPath::TypeRelative(
1206 kind: TyKind::Path(QPath::Resolved(_, path)),
1210 ) => path_prefix.with_prefix(path.segments),
1216 let format_suggestion = |variant: &VariantDef| {
1219 if let Some(ident) = wildcard_ident {
1220 format!("{} @ ", ident.name)
1224 if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
1225 let mut s = String::new();
1226 for seg in path_prefix {
1227 s.push_str(seg.ident.as_str());
1232 let mut s = cx.tcx.def_path_str(adt_def.did);
1237 match variant.ctor_kind {
1238 CtorKind::Fn if variant.fields.len() == 1 => "(_)",
1239 CtorKind::Fn => "(..)",
1240 CtorKind::Const => "",
1241 CtorKind::Fictive => "{ .. }",
1246 match missing_variants.as_slice() {
1248 [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
1250 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1252 "wildcard matches only a single variant and will also match any future added variants",
1254 format_suggestion(x),
1255 Applicability::MaybeIncorrect,
1258 let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
1259 let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
1260 suggestions.push("_".into());
1261 "wildcard matches known variants and will also match future added variants"
1263 "wildcard match will also match any future added variants"
1268 WILDCARD_ENUM_MATCH_ARM,
1272 suggestions.join(" | "),
1273 Applicability::MaybeIncorrect,
1279 fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
1282 I: Clone + Iterator<Item = &'a Pat<'b>>,
1284 if !has_multiple_ref_pats(pats.clone()) {
1288 let (first_sugg, msg, title);
1289 let span = ex.span.source_callsite();
1290 if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
1291 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1293 title = "you don't need to add `&` to both the expression and the patterns";
1295 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1296 msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
1297 title = "you don't need to add `&` to all patterns";
1300 let remaining_suggs = pats.filter_map(|pat| {
1301 if let PatKind::Ref(refp, _) = pat.kind {
1302 Some((pat.span, snippet(cx, refp.span, "..").to_string()))
1308 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1309 if !expr.span.from_expansion() {
1310 multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
1315 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1316 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1317 let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
1318 is_ref_some_arm(cx, &arms[1])
1319 } else if is_none_arm(cx, &arms[1]) {
1320 is_ref_some_arm(cx, &arms[0])
1324 if let Some(rb) = arm_ref {
1325 let suggestion = if rb == BindingAnnotation::Ref {
1331 let output_ty = cx.typeck_results().expr_ty(expr);
1332 let input_ty = cx.typeck_results().expr_ty(ex);
1334 let cast = if_chain! {
1335 if let ty::Adt(_, substs) = input_ty.kind();
1336 let input_ty = substs.type_at(0);
1337 if let ty::Adt(_, substs) = output_ty.kind();
1338 let output_ty = substs.type_at(0);
1339 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1340 if input_ty != output_ty;
1348 let mut applicability = Applicability::MachineApplicable;
1353 &format!("use `{}()` instead", suggestion),
1357 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1367 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1369 if let PatKind::Or(fields) = arm.pat.kind {
1370 // look for multiple fields in this arm that contains at least one Wild pattern
1371 if fields.len() > 1 && fields.iter().any(is_wild) {
1374 WILDCARD_IN_OR_PATTERNS,
1376 "wildcard pattern covers any other pattern as it will match anyway",
1378 "consider handling `_` separately",
1385 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1386 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1387 if let Some(higher::IfLet {
1391 if_else: Some(if_else),
1392 }) = higher::IfLet::hir(cx, expr)
1394 return find_matches_sugg(
1397 IntoIterator::into_iter([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
1403 if let ExprKind::Match(scrut, arms, MatchSource::Normal) = expr.kind {
1404 return find_matches_sugg(
1407 arms.iter().map(|arm| {
1409 cx.tcx.hir().attrs(arm.hir_id),
1423 /// Lint a `match` or `if let` for replacement by `matches!`
1424 fn find_matches_sugg<'a, 'b, I>(
1425 cx: &LateContext<'_>,
1434 + DoubleEndedIterator
1439 Option<&'a Pat<'b>>,
1441 Option<&'a Guard<'b>>,
1447 if cx.typeck_results().expr_ty(expr).is_bool();
1448 if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back();
1449 let iter_without_last = iter.clone();
1450 if let Some((first_attrs, _, first_expr, first_guard)) = iter.next();
1451 if let Some(b0) = find_bool_lit(&first_expr.kind, is_if_let);
1452 if let Some(b1) = find_bool_lit(&last_expr.kind, is_if_let);
1454 if first_guard.is_none() || iter.len() == 0;
1455 if first_attrs.is_empty();
1458 find_bool_lit(&arm.2.kind, is_if_let).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty()
1461 if let Some(last_pat) = last_pat_opt {
1462 if !is_wild(last_pat) {
1467 // The suggestion may be incorrect, because some arms can have `cfg` attributes
1468 // evaluated into `false` and so such arms will be stripped before.
1469 let mut applicability = Applicability::MaybeIncorrect;
1471 use itertools::Itertools as _;
1474 let pat_span = arm.1?.span;
1475 Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability))
1479 let pat_and_guard = if let Some(Guard::If(g)) = first_guard {
1480 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1485 // strip potential borrows (#6503), but only if the type is a reference
1486 let mut ex_new = ex;
1487 if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
1488 if let ty::Ref(..) = cx.typeck_results().expr_ty(ex_inner).kind() {
1494 MATCH_LIKE_MATCHES_MACRO,
1496 &format!("{} expression looks like `matches!` macro", if is_if_let { "if let .. else" } else { "match" }),
1499 "{}matches!({}, {})",
1500 if b0 { "" } else { "!" },
1501 snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
1513 /// Extract a `bool` or `{ bool }`
1514 fn find_bool_lit(ex: &ExprKind<'_>, is_if_let: bool) -> Option<bool> {
1516 ExprKind::Lit(Spanned {
1517 node: LitKind::Bool(b), ..
1527 if let ExprKind::Lit(Spanned {
1528 node: LitKind::Bool(b), ..
1540 #[allow(clippy::too_many_lines)]
1541 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1542 if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1547 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1548 // to prevent false positives as there is currently no better way to detect if code was excluded by
1549 // a macro. See PR #6435
1551 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1552 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1553 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1554 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1555 if rest_snippet.contains("=>");
1557 // The code it self contains another thick arrow "=>"
1558 // -> Either another arm or a comment
1563 let matched_vars = ex.span;
1564 let bind_names = arms[0].pat.span;
1565 let match_body = peel_blocks(arms[0].body);
1566 let mut snippet_body = if match_body.span.from_expansion() {
1567 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1569 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1572 // Do we need to add ';' to suggestion ?
1573 match match_body.kind {
1574 ExprKind::Block(block, _) => {
1575 // macro + expr_ty(body) == ()
1576 if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
1577 snippet_body.push(';');
1581 // expr_ty(body) == ()
1582 if cx.typeck_results().expr_ty(match_body).is_unit() {
1583 snippet_body.push(';');
1588 let mut applicability = Applicability::MaybeIncorrect;
1589 match arms[0].pat.kind {
1590 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1591 // If this match is in a local (`let`) stmt
1592 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1594 parent_let_node.span,
1596 "let {} = {};\n{}let {} = {};",
1597 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1598 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1599 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1600 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1605 // If we are in closure, we need curly braces around suggestion
1606 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1607 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1608 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1609 if let ExprKind::Closure(..) = parent_expr.kind {
1610 cbrace_end = format!("\n{}}}", indent);
1611 // Fix body indent due to the closure
1612 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1613 cbrace_start = format!("{{\n{}", indent);
1616 // If the parent is already an arm, and the body is another match statement,
1617 // we need curly braces around suggestion
1618 let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
1619 if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
1620 if let ExprKind::Match(..) = arm.body.kind {
1621 cbrace_end = format!("\n{}}}", indent);
1622 // Fix body indent due to the match
1623 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1624 cbrace_start = format!("{{\n{}", indent);
1630 "{}let {} = {};\n{}{}{}",
1632 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1633 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1642 MATCH_SINGLE_BINDING,
1644 "this match could be written as a `let` statement",
1645 "consider using `let` statement",
1651 if ex.can_have_side_effects() {
1652 let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
1655 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1661 MATCH_SINGLE_BINDING,
1663 "this match could be replaced by its scrutinee and body",
1664 "consider using the scrutinee and body instead",
1671 MATCH_SINGLE_BINDING,
1673 "this match could be replaced by its body itself",
1674 "consider using the match body instead",
1676 Applicability::MachineApplicable,
1684 /// Returns true if the `ex` match expression is in a local (`let`) statement
1685 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1686 let map = &cx.tcx.hir();
1688 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1689 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1691 return Some(parent_let_expr);
1697 /// Gets the ranges for each range pattern arm. Applies `ty` bounds for open ranges.
1698 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
1701 if let Arm { pat, guard: None, .. } = *arm {
1702 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1703 let lhs_const = match lhs {
1704 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1705 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1707 let rhs_const = match rhs {
1708 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1709 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1712 let lhs_val = lhs_const.int_value(cx, ty)?;
1713 let rhs_val = rhs_const.int_value(cx, ty)?;
1715 let rhs_bound = match range_end {
1716 RangeEnd::Included => EndBound::Included(rhs_val),
1717 RangeEnd::Excluded => EndBound::Excluded(rhs_val),
1719 return Some(SpannedRange {
1721 node: (lhs_val, rhs_bound),
1725 if let PatKind::Lit(value) = pat.kind {
1726 let value = constant_full_int(cx, cx.typeck_results(), value)?;
1727 return Some(SpannedRange {
1729 node: (value, EndBound::Included(value)),
1738 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
1739 pub enum EndBound<T> {
1744 #[derive(Debug, Eq, PartialEq)]
1745 struct SpannedRange<T> {
1747 pub node: (T, EndBound<T>),
1750 // Checks if arm has the form `None => None`
1751 fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
1752 matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
1755 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1756 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
1758 if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
1759 if is_lang_ctor(cx, qpath, OptionSome);
1760 if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
1761 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1762 if let ExprKind::Call(e, args) = peel_blocks(arm.body).kind;
1763 if let ExprKind::Path(ref some_path) = e.kind;
1764 if is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1;
1765 if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
1766 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1774 fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
1777 I: Iterator<Item = &'a Pat<'b>>,
1779 let mut ref_count = 0;
1780 for opt in pats.map(|pat| match pat.kind {
1781 PatKind::Ref(..) => Some(true), // &-patterns
1782 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1783 _ => None, // any other pattern is not fine
1785 if let Some(inner) = opt {
1796 fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1800 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
1807 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1808 struct RangeBound<'a, T>(T, BoundKind, &'a SpannedRange<T>);
1810 impl<'a, T: Copy + Ord> PartialOrd for RangeBound<'a, T> {
1811 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1812 Some(self.cmp(other))
1816 impl<'a, T: Copy + Ord> Ord for RangeBound<'a, T> {
1817 fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
1818 let RangeBound(self_value, self_kind, _) = *self;
1819 (self_value, self_kind).cmp(&(*other_value, *other_kind))
1823 let mut values = Vec::with_capacity(2 * ranges.len());
1825 for r @ SpannedRange { node: (start, end), .. } in ranges {
1826 values.push(RangeBound(*start, BoundKind::Start, r));
1827 values.push(match end {
1828 EndBound::Excluded(val) => RangeBound(*val, BoundKind::EndExcluded, r),
1829 EndBound::Included(val) => RangeBound(*val, BoundKind::EndIncluded, r),
1835 let mut started = vec![];
1837 for RangeBound(_, kind, range) in values {
1839 BoundKind::Start => started.push(range),
1840 BoundKind::EndExcluded | BoundKind::EndIncluded => {
1841 let mut overlap = None;
1843 while let Some(last_started) = started.pop() {
1844 if last_started == range {
1847 overlap = Some(last_started);
1850 if let Some(first_overlapping) = overlap {
1851 return Some((range, first_overlapping));
1860 mod redundant_pattern_match {
1861 use super::REDUNDANT_PATTERN_MATCHING;
1862 use clippy_utils::diagnostics::span_lint_and_then;
1863 use clippy_utils::source::snippet;
1864 use clippy_utils::sugg::Sugg;
1865 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
1866 use clippy_utils::{higher, match_def_path};
1867 use clippy_utils::{is_lang_ctor, is_trait_method, paths};
1868 use if_chain::if_chain;
1869 use rustc_ast::ast::LitKind;
1870 use rustc_data_structures::fx::FxHashSet;
1871 use rustc_errors::Applicability;
1872 use rustc_hir::LangItem::{OptionNone, PollPending};
1874 intravisit::{walk_expr, Visitor},
1875 Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
1877 use rustc_lint::LateContext;
1878 use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
1879 use rustc_span::sym;
1881 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1882 if let Some(higher::IfLet {
1887 }) = higher::IfLet::hir(cx, expr)
1889 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
1891 if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
1892 find_sugg_for_match(cx, expr, op, arms);
1894 if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
1895 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
1899 /// Checks if the drop order for a type matters. Some std types implement drop solely to
1900 /// deallocate memory. For these types, and composites containing them, changing the drop order
1901 /// won't result in any observable side effects.
1902 fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
1903 type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
1906 fn type_needs_ordered_drop_inner<'tcx>(
1907 cx: &LateContext<'tcx>,
1909 seen: &mut FxHashSet<Ty<'tcx>>,
1911 if !seen.insert(ty) {
1914 if !ty.needs_drop(cx.tcx, cx.param_env) {
1920 .map_or(false, |id| implements_trait(cx, ty, id, &[]))
1922 // This type doesn't implement drop, so no side effects here.
1923 // Check if any component type has any.
1925 ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1926 ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
1927 ty::Adt(adt, subs) => adt
1929 .map(|f| f.ty(cx.tcx, subs))
1930 .any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1934 // Check for std types which implement drop, but only for memory allocation.
1935 else if is_type_diagnostic_item(cx, ty, sym::Vec)
1936 || is_type_lang_item(cx, ty, LangItem::OwnedBox)
1937 || is_type_diagnostic_item(cx, ty, sym::Rc)
1938 || is_type_diagnostic_item(cx, ty, sym::Arc)
1939 || is_type_diagnostic_item(cx, ty, sym::cstring_type)
1940 || is_type_diagnostic_item(cx, ty, sym::BTreeMap)
1941 || is_type_diagnostic_item(cx, ty, sym::LinkedList)
1942 || match_type(cx, ty, &paths::WEAK_RC)
1943 || match_type(cx, ty, &paths::WEAK_ARC)
1945 // Check all of the generic arguments.
1946 if let ty::Adt(_, subs) = ty.kind() {
1947 subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
1956 // Extract the generic arguments out of a type
1957 fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
1959 if let ty::Adt(_, subs) = ty.kind();
1960 if let Some(sub) = subs.get(index);
1961 if let GenericArgKind::Type(sub_ty) = sub.unpack();
1970 // Checks if there are any temporaries created in the given expression for which drop order
1972 fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1973 struct V<'a, 'tcx> {
1974 cx: &'a LateContext<'tcx>,
1977 impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
1978 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
1980 // Taking the reference of a value leaves a temporary
1981 // e.g. In `&String::new()` the string is a temporary value.
1982 // Remaining fields are temporary values
1983 // e.g. In `(String::new(), 0).1` the string is a temporary value.
1984 ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
1985 if !matches!(expr.kind, ExprKind::Path(_)) {
1986 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
1989 self.visit_expr(expr);
1993 // the base type is alway taken by reference.
1994 // e.g. In `(vec![0])[0]` the vector is a temporary value.
1995 ExprKind::Index(base, index) => {
1996 if !matches!(base.kind, ExprKind::Path(_)) {
1997 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
2000 self.visit_expr(base);
2003 self.visit_expr(index);
2005 // Method calls can take self by reference.
2006 // e.g. In `String::new().len()` the string is a temporary value.
2007 ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
2008 if !matches!(self_arg.kind, ExprKind::Path(_)) {
2009 let self_by_ref = self
2012 .type_dependent_def_id(expr.hir_id)
2013 .map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
2015 && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg))
2019 self.visit_expr(self_arg);
2022 args.iter().for_each(|arg| self.visit_expr(arg));
2024 // Either explicitly drops values, or changes control flow.
2025 ExprKind::DropTemps(_)
2027 | ExprKind::Break(..)
2028 | ExprKind::Yield(..)
2029 | ExprKind::Block(Block { expr: None, .. }, _)
2030 | ExprKind::Loop(..) => (),
2032 // Only consider the final expression.
2033 ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
2035 _ => walk_expr(self, expr),
2040 let mut v = V { cx, res: false };
2045 fn find_sugg_for_if_let<'tcx>(
2046 cx: &LateContext<'tcx>,
2047 expr: &'tcx Expr<'_>,
2049 let_expr: &'tcx Expr<'_>,
2050 keyword: &'static str,
2053 // also look inside refs
2054 // if we have &None for example, peel it so we can detect "if let None = x"
2055 let check_pat = match let_pat.kind {
2056 PatKind::Ref(inner, _mutability) => inner,
2059 let op_ty = cx.typeck_results().expr_ty(let_expr);
2060 // Determine which function should be used, and the type contained by the corresponding
2062 let (good_method, inner_ty) = match check_pat.kind {
2063 PatKind::TupleStruct(ref qpath, [sub_pat], _) => {
2064 if let PatKind::Wild = sub_pat.kind {
2065 let res = cx.typeck_results().qpath_res(qpath, check_pat.hir_id);
2066 let Some(id) = res.opt_def_id().and_then(|ctor_id| cx.tcx.parent(ctor_id)) else { return };
2067 let lang_items = cx.tcx.lang_items();
2068 if Some(id) == lang_items.result_ok_variant() {
2069 ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
2070 } else if Some(id) == lang_items.result_err_variant() {
2071 ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
2072 } else if Some(id) == lang_items.option_some_variant() {
2073 ("is_some()", op_ty)
2074 } else if Some(id) == lang_items.poll_ready_variant() {
2075 ("is_ready()", op_ty)
2076 } else if match_def_path(cx, id, &paths::IPADDR_V4) {
2077 ("is_ipv4()", op_ty)
2078 } else if match_def_path(cx, id, &paths::IPADDR_V6) {
2079 ("is_ipv6()", op_ty)
2087 PatKind::Path(ref path) => {
2088 let method = if is_lang_ctor(cx, path, OptionNone) {
2090 } else if is_lang_ctor(cx, path, PollPending) {
2095 // `None` and `Pending` don't have an inner type.
2096 (method, cx.tcx.types.unit)
2101 // If this is the last expression in a block or there is an else clause then the whole
2102 // type needs to be considered, not just the inner type of the branch being matched on.
2103 // Note the last expression in a block is dropped after all local bindings.
2104 let check_ty = if has_else
2105 || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
2112 // All temporaries created in the scrutinee expression are dropped at the same time as the
2113 // scrutinee would be, so they have to be considered as well.
2114 // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
2115 // for the duration if body.
2116 let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
2118 // check that `while_let_on_iterator` lint does not trigger
2120 if keyword == "while";
2121 if let ExprKind::MethodCall(method_path, _, _) = let_expr.kind;
2122 if method_path.ident.name == sym::next;
2123 if is_trait_method(cx, let_expr, sym::Iterator);
2129 let result_expr = match &let_expr.kind {
2130 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2131 ExprKind::Unary(UnOp::Deref, deref) => deref,
2137 REDUNDANT_PATTERN_MATCHING,
2139 &format!("redundant pattern matching, consider using `{}`", good_method),
2141 // if/while let ... = ... { ... }
2142 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2143 let expr_span = expr.span;
2145 // if/while let ... = ... { ... }
2147 let op_span = result_expr.span.source_callsite();
2149 // if/while let ... = ... { ... }
2150 // ^^^^^^^^^^^^^^^^^^^
2151 let span = expr_span.until(op_span.shrink_to_hi());
2153 let app = if needs_drop {
2154 Applicability::MaybeIncorrect
2156 Applicability::MachineApplicable
2159 let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
2163 diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
2166 diag.note("this will change drop order of the result, as well as all temporaries");
2167 diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
2173 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
2174 if arms.len() == 2 {
2175 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
2177 let found_good_method = match node_pair {
2179 PatKind::TupleStruct(ref path_left, patterns_left, _),
2180 PatKind::TupleStruct(ref path_right, patterns_right, _),
2181 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
2182 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
2183 find_good_method_for_match(
2194 find_good_method_for_match(
2209 (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
2210 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
2211 if patterns.len() == 1 =>
2213 if let PatKind::Wild = patterns[0].kind {
2214 find_good_method_for_match(
2219 &paths::OPTION_SOME,
2220 &paths::OPTION_NONE,
2225 find_good_method_for_match(
2231 &paths::POLL_PENDING,
2243 if let Some(good_method) = found_good_method {
2244 let span = expr.span.to(op.span);
2245 let result_expr = match &op.kind {
2246 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2251 REDUNDANT_PATTERN_MATCHING,
2253 &format!("redundant pattern matching, consider using `{}`", good_method),
2255 diag.span_suggestion(
2258 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
2259 Applicability::MaybeIncorrect, // snippet
2267 #[allow(clippy::too_many_arguments)]
2268 fn find_good_method_for_match<'a>(
2269 cx: &LateContext<'_>,
2271 path_left: &QPath<'_>,
2272 path_right: &QPath<'_>,
2273 expected_left: &[&str],
2274 expected_right: &[&str],
2275 should_be_left: &'a str,
2276 should_be_right: &'a str,
2277 ) -> Option<&'a str> {
2280 .qpath_res(path_left, arms[0].pat.hir_id)
2284 .qpath_res(path_right, arms[1].pat.hir_id)
2286 let body_node_pair =
2287 if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) {
2288 (&(*arms[0].body).kind, &(*arms[1].body).kind)
2289 } else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) {
2290 (&(*arms[1].body).kind, &(*arms[0].body).kind)
2295 match body_node_pair {
2296 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
2297 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
2298 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
2307 fn test_overlapping() {
2308 use rustc_span::source_map::DUMMY_SP;
2310 let sp = |s, e| SpannedRange {
2315 assert_eq!(None, overlapping::<u8>(&[]));
2316 assert_eq!(None, overlapping(&[sp(1, EndBound::Included(4))]));
2319 overlapping(&[sp(1, EndBound::Included(4)), sp(5, EndBound::Included(6))])
2324 sp(1, EndBound::Included(4)),
2325 sp(5, EndBound::Included(6)),
2326 sp(10, EndBound::Included(11))
2330 Some((&sp(1, EndBound::Included(4)), &sp(3, EndBound::Included(6)))),
2331 overlapping(&[sp(1, EndBound::Included(4)), sp(3, EndBound::Included(6))])
2334 Some((&sp(5, EndBound::Included(6)), &sp(6, EndBound::Included(11)))),
2336 sp(1, EndBound::Included(4)),
2337 sp(5, EndBound::Included(6)),
2338 sp(6, EndBound::Included(11))
2343 /// Implementation of `MATCH_SAME_ARMS`.
2344 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
2345 if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind {
2346 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
2347 let mut h = SpanlessHash::new(cx);
2348 h.hash_expr(arm.body);
2352 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
2353 let min_index = usize::min(lindex, rindex);
2354 let max_index = usize::max(lindex, rindex);
2356 let mut local_map: HirIdMap<HirId> = HirIdMap::default();
2357 let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
2359 if let Some(a_id) = path_to_local(a);
2360 if let Some(b_id) = path_to_local(b);
2361 let entry = match local_map.entry(a_id) {
2362 Entry::Vacant(entry) => entry,
2363 // check if using the same bindings as before
2364 Entry::Occupied(entry) => return *entry.get() == b_id,
2366 // the names technically don't have to match; this makes the lint more conservative
2367 if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id);
2368 if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b));
2369 if pat_contains_local(lhs.pat, a_id);
2370 if pat_contains_local(rhs.pat, b_id);
2379 // Arms with a guard are ignored, those can’t always be merged together
2380 // This is also the case for arms in-between each there is an arm with a guard
2381 (min_index..=max_index).all(|index| arms[index].guard.is_none())
2382 && SpanlessEq::new(cx)
2383 .expr_fallback(eq_fallback)
2384 .eq_expr(lhs.body, rhs.body)
2385 // these checks could be removed to allow unused bindings
2386 && bindings_eq(lhs.pat, local_map.keys().copied().collect())
2387 && bindings_eq(rhs.pat, local_map.values().copied().collect())
2390 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
2391 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
2396 "this `match` has identical arm bodies",
2398 diag.span_note(i.body.span, "same as this");
2400 // Note: this does not use `span_suggestion` on purpose:
2401 // there is no clean way
2402 // to remove the other arm. Building a span and suggest to replace it to ""
2403 // makes an even more confusing error message. Also in order not to make up a
2404 // span for the whole pattern, the suggestion is only shown when there is only
2405 // one pattern. The user should know about `|` if they are already using it…
2407 let lhs = snippet(cx, i.pat.span, "<pat1>");
2408 let rhs = snippet(cx, j.pat.span, "<pat2>");
2410 if let PatKind::Wild = j.pat.kind {
2411 // if the last arm is _, then i could be integrated into _
2412 // note that i.pat cannot be _, because that would mean that we're
2413 // hiding all the subsequent arms, and rust won't compile
2417 "`{}` has the same arm body as the `_` wildcard, consider removing it",
2422 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
2423 .help("...or consider changing the match arm bodies");
2431 fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool {
2432 let mut result = false;
2433 pat.walk_short(|p| {
2434 result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id);
2440 /// Returns true if all the bindings in the `Pat` are in `ids` and vice versa
2441 fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool {
2442 let mut result = true;
2443 pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
2444 result && ids.is_empty()