1 use crate::consts::{constant, miri_to_const, Constant};
2 use crate::utils::sugg::Sugg;
3 use crate::utils::usage::is_unused;
5 expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable,
6 is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, meets_msrv, multispan_sugg, remove_blocks,
7 snippet, snippet_block, snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
10 use crate::utils::{paths, search_same, SpanlessEq, SpanlessHash};
11 use if_chain::if_chain;
12 use rustc_ast::ast::LitKind;
13 use rustc_data_structures::fx::FxHashMap;
14 use rustc_errors::Applicability;
15 use rustc_hir::def::CtorKind;
17 Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, Local, MatchSource, Mutability, Node, Pat,
18 PatKind, QPath, RangeEnd,
20 use rustc_lint::{LateContext, LateLintPass, LintContext};
21 use rustc_middle::lint::in_external_macro;
22 use rustc_middle::ty::{self, Ty, TyS};
23 use rustc_semver::RustcVersion;
24 use rustc_session::{declare_tool_lint, impl_lint_pass};
25 use rustc_span::source_map::{Span, Spanned};
26 use rustc_span::{sym, Symbol};
27 use std::cmp::Ordering;
28 use std::collections::hash_map::Entry;
29 use std::collections::Bound;
31 declare_clippy_lint! {
32 /// **What it does:** Checks for matches with a single arm where an `if let`
33 /// will usually suffice.
35 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
37 /// **Known problems:** None.
41 /// # fn bar(stool: &str) {}
42 /// # let x = Some("abc");
45 /// Some(ref foo) => bar(foo),
50 /// if let Some(ref foo) = x {
56 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
59 declare_clippy_lint! {
60 /// **What it does:** Checks for matches with two arms where an `if let else` will
63 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
65 /// **Known problems:** Personal style preferences may differ.
72 /// # fn bar(foo: &usize) {}
73 /// # let other_ref: usize = 1;
74 /// # let x: Option<&usize> = Some(&1);
76 /// Some(ref foo) => bar(foo),
77 /// _ => bar(&other_ref),
81 /// Using `if let` with `else`:
84 /// # fn bar(foo: &usize) {}
85 /// # let other_ref: usize = 1;
86 /// # let x: Option<&usize> = Some(&1);
87 /// if let Some(ref foo) = x {
93 pub SINGLE_MATCH_ELSE,
95 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
98 declare_clippy_lint! {
99 /// **What it does:** Checks for matches where all arms match a reference,
100 /// suggesting to remove the reference and deref the matched expression
101 /// instead. It also checks for `if let &foo = bar` blocks.
103 /// **Why is this bad?** It just makes the code less readable. That reference
104 /// destructuring adds nothing to the code.
106 /// **Known problems:** None.
112 /// &A(ref y) => foo(y),
119 /// A(ref y) => foo(y),
126 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
129 declare_clippy_lint! {
130 /// **What it does:** Checks for matches where match expression is a `bool`. It
131 /// suggests to replace the expression with an `if...else` block.
133 /// **Why is this bad?** It makes the code less readable.
135 /// **Known problems:** None.
141 /// let condition: bool = true;
142 /// match condition {
147 /// Use if/else instead:
151 /// let condition: bool = true;
160 "a `match` on a boolean expression instead of an `if..else` block"
163 declare_clippy_lint! {
164 /// **What it does:** Checks for overlapping match arms.
166 /// **Why is this bad?** It is likely to be an error and if not, makes the code
169 /// **Known problems:** None.
175 /// 1...10 => println!("1 ... 10"),
176 /// 5...15 => println!("5 ... 15"),
180 pub MATCH_OVERLAPPING_ARM,
182 "a `match` with overlapping arms"
185 declare_clippy_lint! {
186 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
187 /// and take drastic actions like `panic!`.
189 /// **Why is this bad?** It is generally a bad practice, similar to
190 /// catching all exceptions in java with `catch(Exception)`
192 /// **Known problems:** None.
196 /// let x: Result<i32, &str> = Ok(3);
198 /// Ok(_) => println!("ok"),
199 /// Err(_) => panic!("err"),
202 pub MATCH_WILD_ERR_ARM,
204 "a `match` with `Err(_)` arm and take drastic actions"
207 declare_clippy_lint! {
208 /// **What it does:** Checks for match which is used to add a reference to an
211 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
213 /// **Known problems:** None.
217 /// let x: Option<()> = None;
220 /// let r: Option<&()> = match x {
222 /// Some(ref v) => Some(v),
226 /// let r: Option<&()> = x.as_ref();
230 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
233 declare_clippy_lint! {
234 /// **What it does:** Checks for wildcard enum matches using `_`.
236 /// **Why is this bad?** New enum variants added by library updates can be missed.
238 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
239 /// variants, and also may not use correct path to enum if it's not present in the current scope.
243 /// # enum Foo { A(usize), B(usize) }
244 /// # let x = Foo::B(1);
257 pub WILDCARD_ENUM_MATCH_ARM,
259 "a wildcard enum match arm using `_`"
262 declare_clippy_lint! {
263 /// **What it does:** Checks for wildcard enum matches for a single variant.
265 /// **Why is this bad?** New enum variants added by library updates can be missed.
267 /// **Known problems:** Suggested replacements may not use correct path to enum
268 /// if it's not present in the current scope.
273 /// # enum Foo { A, B, C }
274 /// # let x = Foo::B;
289 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
291 "a wildcard enum match for a single variant"
294 declare_clippy_lint! {
295 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
297 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
298 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
300 /// **Known problems:** None.
316 pub WILDCARD_IN_OR_PATTERNS,
318 "a wildcard pattern used with others patterns in same match arm"
321 declare_clippy_lint! {
322 /// **What it does:** Checks for matches being used to destructure a single-variant enum
323 /// or tuple struct where a `let` will suffice.
325 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
327 /// **Known problems:** None.
335 /// let wrapper = Wrapper::Data(42);
337 /// let data = match wrapper {
338 /// Wrapper::Data(i) => i,
342 /// The correct use would be:
348 /// let wrapper = Wrapper::Data(42);
349 /// let Wrapper::Data(data) = wrapper;
351 pub INFALLIBLE_DESTRUCTURING_MATCH,
353 "a `match` statement with a single infallible arm instead of a `let`"
356 declare_clippy_lint! {
357 /// **What it does:** Checks for useless match that binds to only one value.
359 /// **Why is this bad?** Readability and needless complexity.
361 /// **Known problems:** Suggested replacements may be incorrect when `match`
362 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
377 /// let (c, d) = (a, b);
379 pub MATCH_SINGLE_BINDING,
381 "a match with a single binding instead of using `let` statement"
384 declare_clippy_lint! {
385 /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
387 /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after
388 /// matching all enum variants explicitly.
390 /// **Known problems:** None.
394 /// # struct A { a: i32 }
395 /// let a = A { a: 5 };
399 /// A { a: 5, .. } => {},
405 /// A { a: 5 } => {},
409 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
411 "a match on a struct that binds all fields but still uses the wildcard pattern"
414 declare_clippy_lint! {
415 /// **What it does:** Lint for redundant pattern matching over `Result`, `Option`,
416 /// `std::task::Poll` or `std::net::IpAddr`
418 /// **Why is this bad?** It's more concise and clear to just use the proper
421 /// **Known problems:** None.
426 /// # use std::task::Poll;
427 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
428 /// if let Ok(_) = Ok::<i32, i32>(42) {}
429 /// if let Err(_) = Err::<i32, i32>(42) {}
430 /// if let None = None::<()> {}
431 /// if let Some(_) = Some(42) {}
432 /// if let Poll::Pending = Poll::Pending::<()> {}
433 /// if let Poll::Ready(_) = Poll::Ready(42) {}
434 /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
435 /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
436 /// match Ok::<i32, i32>(42) {
442 /// The more idiomatic use would be:
445 /// # use std::task::Poll;
446 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
447 /// if Ok::<i32, i32>(42).is_ok() {}
448 /// if Err::<i32, i32>(42).is_err() {}
449 /// if None::<()>.is_none() {}
450 /// if Some(42).is_some() {}
451 /// if Poll::Pending::<()>.is_pending() {}
452 /// if Poll::Ready(42).is_ready() {}
453 /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
454 /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
455 /// Ok::<i32, i32>(42).is_ok();
457 pub REDUNDANT_PATTERN_MATCHING,
459 "use the proper utility function avoiding an `if let`"
462 declare_clippy_lint! {
463 /// **What it does:** Checks for `match` or `if let` expressions producing a
464 /// `bool` that could be written using `matches!`
466 /// **Why is this bad?** Readability and needless complexity.
468 /// **Known problems:** This lint falsely triggers, if there are arms with
469 /// `cfg` attributes that remove an arm evaluating to `false`.
476 /// let a = match x {
481 /// let a = if let Some(0) = x {
488 /// let a = matches!(x, Some(0));
490 pub MATCH_LIKE_MATCHES_MACRO,
492 "a match that could be written with the matches! macro"
495 declare_clippy_lint! {
496 /// **What it does:** Checks for `match` with identical arm bodies.
498 /// **Why is this bad?** This is probably a copy & paste error. If arm bodies
499 /// are the same on purpose, you can factor them
500 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
502 /// **Known problems:** False positive possible with order dependent `match`
504 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
511 /// Baz => bar(), // <= oops
515 /// This should probably be
520 /// Baz => baz(), // <= fixed
524 /// or if the original code was not a typo:
527 /// Bar | Baz => bar(), // <= shows the intent better
533 "`match` with identical arm bodies"
538 msrv: Option<RustcVersion>,
539 infallible_destructuring_match_linted: bool,
544 pub fn new(msrv: Option<RustcVersion>) -> Self {
552 impl_lint_pass!(Matches => [
557 MATCH_OVERLAPPING_ARM,
560 WILDCARD_ENUM_MATCH_ARM,
561 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
562 WILDCARD_IN_OR_PATTERNS,
563 MATCH_SINGLE_BINDING,
564 INFALLIBLE_DESTRUCTURING_MATCH,
565 REST_PAT_IN_FULLY_BOUND_STRUCTS,
566 REDUNDANT_PATTERN_MATCHING,
567 MATCH_LIKE_MATCHES_MACRO,
571 const MATCH_LIKE_MATCHES_MACRO_MSRV: RustcVersion = RustcVersion::new(1, 42, 0);
573 impl<'tcx> LateLintPass<'tcx> for Matches {
574 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
575 if in_external_macro(cx.sess(), expr.span) || in_macro(expr.span) {
579 redundant_pattern_match::check(cx, expr);
581 if meets_msrv(self.msrv.as_ref(), &MATCH_LIKE_MATCHES_MACRO_MSRV) {
582 if !check_match_like_matches(cx, expr) {
583 lint_match_arms(cx, expr);
586 lint_match_arms(cx, expr);
589 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
590 check_single_match(cx, ex, arms, expr);
591 check_match_bool(cx, ex, arms, expr);
592 check_overlapping_arms(cx, ex, arms);
593 check_wild_err_arm(cx, ex, arms);
594 check_wild_enum_match(cx, ex, arms);
595 check_match_as_ref(cx, ex, arms, expr);
596 check_wild_in_or_pats(cx, arms);
598 if self.infallible_destructuring_match_linted {
599 self.infallible_destructuring_match_linted = false;
601 check_match_single_binding(cx, ex, arms, expr);
604 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
605 check_match_ref_pats(cx, ex, arms, expr);
609 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
611 if !in_external_macro(cx.sess(), local.span);
612 if !in_macro(local.span);
613 if let Some(ref expr) = local.init;
614 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
615 if arms.len() == 1 && arms[0].guard.is_none();
616 if let PatKind::TupleStruct(
617 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
619 if let Some(arg) = get_arg_name(&args[0]);
620 let body = remove_blocks(&arms[0].body);
621 if match_var(body, arg);
624 let mut applicability = Applicability::MachineApplicable;
625 self.infallible_destructuring_match_linted = true;
628 INFALLIBLE_DESTRUCTURING_MATCH,
630 "you seem to be trying to use `match` to destructure a single infallible pattern. \
631 Consider using `let`",
635 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
636 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
637 snippet_with_applicability(cx, target.span, "..", &mut applicability),
645 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
647 if !in_external_macro(cx.sess(), pat.span);
648 if !in_macro(pat.span);
649 if let PatKind::Struct(QPath::Resolved(_, ref path), fields, true) = pat.kind;
650 if let Some(def_id) = path.res.opt_def_id();
651 let ty = cx.tcx.type_of(def_id);
652 if let ty::Adt(def, _) = ty.kind();
653 if def.is_struct() || def.is_union();
654 if fields.len() == def.non_enum_variant().fields.len();
659 REST_PAT_IN_FULLY_BOUND_STRUCTS,
661 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
663 "consider removing `..` from this binding",
669 extract_msrv_attr!(LateContext);
673 fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
674 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
675 if in_macro(expr.span) {
676 // Don't lint match expressions present in
677 // macro_rules! block
680 if let PatKind::Or(..) = arms[0].pat.kind {
681 // don't lint for or patterns for now, this makes
682 // the lint noisy in unnecessary situations
685 let els = arms[1].body;
686 let els = if is_unit_expr(remove_blocks(els)) {
688 } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
689 if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
690 // single statement/expr "else" block, don't lint
693 // block with 2+ statements or 1 expr and 1+ statement
697 // not a block, don't lint
701 let ty = cx.typeck_results().expr_ty(ex);
702 if *ty.kind() != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
703 check_single_match_single_pattern(cx, ex, arms, expr, els);
704 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
709 fn check_single_match_single_pattern(
710 cx: &LateContext<'_>,
714 els: Option<&Expr<'_>>,
716 if is_wild(&arms[1].pat) {
717 report_single_match_single_pattern(cx, ex, arms, expr, els);
721 fn report_single_match_single_pattern(
722 cx: &LateContext<'_>,
726 els: Option<&Expr<'_>>,
728 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
729 let els_str = els.map_or(String::new(), |els| {
730 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
736 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
740 "if let {} = {} {}{}",
741 snippet(cx, arms[0].pat.span, ".."),
742 snippet(cx, ex.span, ".."),
743 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
746 Applicability::HasPlaceholders,
750 fn check_single_match_opt_like(
751 cx: &LateContext<'_>,
756 els: Option<&Expr<'_>>,
758 // list of candidate `Enum`s we know will never get any more members
760 (&paths::COW, "Borrowed"),
761 (&paths::COW, "Cow::Borrowed"),
762 (&paths::COW, "Cow::Owned"),
763 (&paths::COW, "Owned"),
764 (&paths::OPTION, "None"),
765 (&paths::RESULT, "Err"),
766 (&paths::RESULT, "Ok"),
769 let path = match arms[1].pat.kind {
770 PatKind::TupleStruct(ref path, ref inner, _) => {
771 // Contains any non wildcard patterns (e.g., `Err(err)`)?
772 if !inner.iter().all(is_wild) {
775 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
777 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
778 PatKind::Path(ref path) => {
779 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
784 for &(ty_path, pat_path) in candidates {
785 if path == *pat_path && match_type(cx, ty, ty_path) {
786 report_single_match_single_pattern(cx, ex, arms, expr, els);
791 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
792 // Type of expression is `bool`.
793 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
798 "you seem to be trying to match on a boolean expression",
802 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
803 if let ExprKind::Lit(ref lit) = arm_bool.kind {
805 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
806 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
816 if let Some((true_expr, false_expr)) = exprs {
817 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
818 (false, false) => Some(format!(
820 snippet(cx, ex.span, "b"),
821 expr_block(cx, true_expr, None, "..", Some(expr.span)),
822 expr_block(cx, false_expr, None, "..", Some(expr.span))
824 (false, true) => Some(format!(
826 snippet(cx, ex.span, "b"),
827 expr_block(cx, true_expr, None, "..", Some(expr.span))
830 let test = Sugg::hir(cx, ex, "..");
834 expr_block(cx, false_expr, None, "..", Some(expr.span))
837 (true, true) => None,
840 if let Some(sugg) = sugg {
841 diag.span_suggestion(
843 "consider using an `if`/`else` expression",
845 Applicability::HasPlaceholders,
855 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
856 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
857 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
858 let type_ranges = type_ranges(&ranges);
859 if !type_ranges.is_empty() {
860 if let Some((start, end)) = overlapping(&type_ranges) {
863 MATCH_OVERLAPPING_ARM,
865 "some ranges overlap",
867 "overlaps with this",
874 fn check_wild_err_arm(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
875 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
876 if is_type_diagnostic_item(cx, ex_ty, sym::result_type) {
878 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
879 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
880 if path_str == "Err" {
881 let mut matching_wild = inner.iter().any(is_wild);
882 let mut ident_bind_name = String::from("_");
884 // Looking for unused bindings (i.e.: `_e`)
885 inner.iter().for_each(|pat| {
886 if let PatKind::Binding(.., ident, None) = &pat.kind {
887 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
888 ident_bind_name = (&ident.name.as_str()).to_string();
889 matching_wild = true;
896 if let ExprKind::Block(ref block, _) = arm.body.kind;
897 if is_panic_block(block);
899 // `Err(_)` or `Err(_e)` arm with `panic!` found
900 span_lint_and_note(cx,
903 &format!("`Err({})` matches all errors", &ident_bind_name),
905 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
915 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
916 let ty = cx.typeck_results().expr_ty(ex);
918 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
919 // don't complain about not enumerating the mall.
923 // First pass - check for violation, but don't do much book-keeping because this is hopefully
924 // the uncommon case, and the book-keeping is slightly expensive.
925 let mut wildcard_span = None;
926 let mut wildcard_ident = None;
928 if let PatKind::Wild = arm.pat.kind {
929 wildcard_span = Some(arm.pat.span);
930 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
931 wildcard_span = Some(arm.pat.span);
932 wildcard_ident = Some(ident);
936 if let Some(wildcard_span) = wildcard_span {
937 // Accumulate the variants which should be put in place of the wildcard because they're not
940 let mut missing_variants = vec![];
941 if let ty::Adt(def, _) = ty.kind() {
942 for variant in &def.variants {
943 missing_variants.push(variant);
948 if arm.guard.is_some() {
949 // Guards mean that this case probably isn't exhaustively covered. Technically
950 // this is incorrect, as we should really check whether each variant is exhaustively
951 // covered by the set of guards that cover it, but that's really hard to do.
954 if let PatKind::Path(ref path) = arm.pat.kind {
955 if let QPath::Resolved(_, p) = path {
956 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
958 } else if let PatKind::TupleStruct(QPath::Resolved(_, p), ref patterns, ..) = arm.pat.kind {
959 // Some simple checks for exhaustive patterns.
960 // There is a room for improvements to detect more cases,
961 // but it can be more expensive to do so.
962 let is_pattern_exhaustive =
963 |pat: &&Pat<'_>| matches!(pat.kind, PatKind::Wild | PatKind::Binding(.., None));
964 if patterns.iter().all(is_pattern_exhaustive) {
965 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
970 let mut suggestion: Vec<String> = missing_variants
973 let suffix = match v.ctor_kind {
974 CtorKind::Fn => "(..)",
975 CtorKind::Const | CtorKind::Fictive => "",
977 let ident_str = if let Some(ident) = wildcard_ident {
978 format!("{} @ ", ident.name)
982 // This path assumes that the enum type is imported into scope.
983 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
987 if suggestion.is_empty() {
991 let mut message = "wildcard match will miss any future added variants";
993 if let ty::Adt(def, _) = ty.kind() {
994 if def.is_variant_list_non_exhaustive() {
995 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
996 suggestion.push(String::from("_"));
1000 if suggestion.len() == 1 {
1001 // No need to check for non-exhaustive enum as in that case len would be greater than 1
1004 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1008 suggestion[0].clone(),
1009 Applicability::MaybeIncorrect,
1015 WILDCARD_ENUM_MATCH_ARM,
1019 suggestion.join(" | "),
1020 Applicability::MaybeIncorrect,
1025 // If the block contains only a `panic!` macro (as expression or statement)
1026 fn is_panic_block(block: &Block<'_>) -> bool {
1027 match (&block.expr, block.stmts.len(), block.stmts.first()) {
1028 (&Some(ref exp), 0, _) => {
1029 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
1031 (&None, 1, Some(stmt)) => {
1032 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
1038 fn check_match_ref_pats(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1039 if has_only_ref_pats(arms) {
1040 let mut suggs = Vec::with_capacity(arms.len() + 1);
1041 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
1042 let span = ex.span.source_callsite();
1043 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1045 "you don't need to add `&` to both the expression and the patterns",
1049 let span = ex.span.source_callsite();
1050 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1052 "you don't need to add `&` to all patterns",
1053 "instead of prefixing all patterns with `&`, you can dereference the expression",
1057 suggs.extend(arms.iter().filter_map(|a| {
1058 if let PatKind::Ref(ref refp, _) = a.pat.kind {
1059 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
1065 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1066 if !expr.span.from_expansion() {
1067 multispan_sugg(diag, msg, suggs);
1073 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1074 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1075 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
1076 is_ref_some_arm(&arms[1])
1077 } else if is_none_arm(&arms[1]) {
1078 is_ref_some_arm(&arms[0])
1082 if let Some(rb) = arm_ref {
1083 let suggestion = if rb == BindingAnnotation::Ref {
1089 let output_ty = cx.typeck_results().expr_ty(expr);
1090 let input_ty = cx.typeck_results().expr_ty(ex);
1092 let cast = if_chain! {
1093 if let ty::Adt(_, substs) = input_ty.kind();
1094 let input_ty = substs.type_at(0);
1095 if let ty::Adt(_, substs) = output_ty.kind();
1096 let output_ty = substs.type_at(0);
1097 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1098 if input_ty != output_ty;
1106 let mut applicability = Applicability::MachineApplicable;
1111 &format!("use `{}()` instead", suggestion),
1115 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1125 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1127 if let PatKind::Or(ref fields) = arm.pat.kind {
1128 // look for multiple fields in this arm that contains at least one Wild pattern
1129 if fields.len() > 1 && fields.iter().any(is_wild) {
1132 WILDCARD_IN_OR_PATTERNS,
1134 "wildcard pattern covers any other pattern as it will match anyway.",
1136 "Consider handling `_` separately.",
1143 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1144 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1145 if let ExprKind::Match(ex, arms, ref match_source) = &expr.kind {
1146 match match_source {
1147 MatchSource::Normal => find_matches_sugg(cx, ex, arms, expr, false),
1148 MatchSource::IfLetDesugar { .. } => find_matches_sugg(cx, ex, arms, expr, true),
1156 /// Lint a `match` or desugared `if let` for replacement by `matches!`
1157 fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, desugared: bool) -> bool {
1160 if cx.typeck_results().expr_ty(expr).is_bool();
1161 if let Some((b1_arm, b0_arms)) = arms.split_last();
1162 if let Some(b0) = find_bool_lit(&b0_arms[0].body.kind, desugared);
1163 if let Some(b1) = find_bool_lit(&b1_arm.body.kind, desugared);
1164 if is_wild(&b1_arm.pat);
1166 let if_guard = &b0_arms[0].guard;
1167 if if_guard.is_none() || b0_arms.len() == 1;
1168 if b0_arms[0].attrs.is_empty();
1169 if b0_arms[1..].iter()
1171 find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) &&
1172 arm.guard.is_none() && arm.attrs.is_empty()
1175 // The suggestion may be incorrect, because some arms can have `cfg` attributes
1176 // evaluated into `false` and so such arms will be stripped before.
1177 let mut applicability = Applicability::MaybeIncorrect;
1179 use itertools::Itertools as _;
1181 .map(|arm| snippet_with_applicability(cx, arm.pat.span, "..", &mut applicability))
1184 let pat_and_guard = if let Some(Guard::If(g)) = if_guard {
1185 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1191 MATCH_LIKE_MATCHES_MACRO,
1193 &format!("{} expression looks like `matches!` macro", if desugared { "if let .. else" } else { "match" }),
1196 "{}matches!({}, {})",
1197 if b0 { "" } else { "!" },
1198 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1210 /// Extract a `bool` or `{ bool }`
1211 fn find_bool_lit(ex: &ExprKind<'_>, desugared: bool) -> Option<bool> {
1213 ExprKind::Lit(Spanned {
1214 node: LitKind::Bool(b), ..
1224 if let ExprKind::Lit(Spanned {
1225 node: LitKind::Bool(b), ..
1237 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1238 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1241 let matched_vars = ex.span;
1242 let bind_names = arms[0].pat.span;
1243 let match_body = remove_blocks(&arms[0].body);
1244 let mut snippet_body = if match_body.span.from_expansion() {
1245 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1247 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1250 // Do we need to add ';' to suggestion ?
1251 match match_body.kind {
1252 ExprKind::Block(block, _) => {
1253 // macro + expr_ty(body) == ()
1254 if block.span.from_expansion() && cx.typeck_results().expr_ty(&match_body).is_unit() {
1255 snippet_body.push(';');
1259 // expr_ty(body) == ()
1260 if cx.typeck_results().expr_ty(&match_body).is_unit() {
1261 snippet_body.push(';');
1266 let mut applicability = Applicability::MaybeIncorrect;
1267 match arms[0].pat.kind {
1268 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1269 // If this match is in a local (`let`) stmt
1270 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1272 parent_let_node.span,
1274 "let {} = {};\n{}let {} = {};",
1275 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1276 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1277 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1278 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1283 // If we are in closure, we need curly braces around suggestion
1284 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1285 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1286 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1287 if let ExprKind::Closure(..) = parent_expr.kind {
1288 cbrace_end = format!("\n{}}}", indent);
1289 // Fix body indent due to the closure
1290 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1291 cbrace_start = format!("{{\n{}", indent);
1297 "{}let {} = {};\n{}{}{}",
1299 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1300 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1309 MATCH_SINGLE_BINDING,
1311 "this match could be written as a `let` statement",
1312 "consider using `let` statement",
1320 MATCH_SINGLE_BINDING,
1322 "this match could be replaced by its body itself",
1323 "consider using the match body instead",
1325 Applicability::MachineApplicable,
1332 /// Returns true if the `ex` match expression is in a local (`let`) statement
1333 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1335 let map = &cx.tcx.hir();
1336 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1337 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1339 return Some(parent_let_expr);
1345 /// Gets all arms that are unbounded `PatRange`s.
1346 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<Constant>> {
1350 ref pat, guard: None, ..
1353 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1354 let lhs = match lhs {
1355 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1356 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1358 let rhs = match rhs {
1359 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1360 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1362 let rhs = match range_end {
1363 RangeEnd::Included => Bound::Included(rhs),
1364 RangeEnd::Excluded => Bound::Excluded(rhs),
1366 return Some(SpannedRange {
1372 if let PatKind::Lit(ref value) = pat.kind {
1373 let value = constant(cx, cx.typeck_results(), value)?.0;
1374 return Some(SpannedRange {
1376 node: (value.clone(), Bound::Included(value)),
1385 #[derive(Debug, Eq, PartialEq)]
1386 pub struct SpannedRange<T> {
1388 pub node: (T, Bound<T>),
1391 type TypedRanges = Vec<SpannedRange<u128>>;
1393 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1394 /// and other types than
1395 /// `Uint` and `Int` probably don't make sense.
1396 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1399 .filter_map(|range| match range.node {
1400 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1402 node: (start, Bound::Included(end)),
1404 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1406 node: (start, Bound::Excluded(end)),
1408 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1410 node: (start, Bound::Unbounded),
1417 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1419 ExprKind::Tup(ref v) if v.is_empty() => true,
1420 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1425 // Checks if arm has the form `None => None`
1426 fn is_none_arm(arm: &Arm<'_>) -> bool {
1427 matches!(arm.pat.kind, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE))
1430 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1431 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1433 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1434 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1435 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1436 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1437 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1438 if let ExprKind::Path(ref some_path) = e.kind;
1439 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1440 if let ExprKind::Path(QPath::Resolved(_, ref path2)) = args[0].kind;
1441 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1449 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1454 PatKind::Ref(..) => Some(true), // &-patterns
1455 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1456 _ => None, // any other pattern is not fine
1459 .collect::<Option<Vec<bool>>>();
1460 // look for Some(v) where there's at least one true element
1461 mapped.map_or(false, |v| v.iter().any(|el| *el))
1464 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1468 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1470 Start(T, &'a SpannedRange<T>),
1471 End(Bound<T>, &'a SpannedRange<T>),
1474 impl<'a, T: Copy> Kind<'a, T> {
1475 fn range(&self) -> &'a SpannedRange<T> {
1477 Kind::Start(_, r) | Kind::End(_, r) => r,
1481 fn value(self) -> Bound<T> {
1483 Kind::Start(t, _) => Bound::Included(t),
1484 Kind::End(t, _) => t,
1489 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1490 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1491 Some(self.cmp(other))
1495 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1496 fn cmp(&self, other: &Self) -> Ordering {
1497 match (self.value(), other.value()) {
1498 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1499 // Range patterns cannot be unbounded (yet)
1500 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1501 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1502 Ordering::Equal => Ordering::Greater,
1505 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1506 Ordering::Equal => Ordering::Less,
1513 let mut values = Vec::with_capacity(2 * ranges.len());
1516 values.push(Kind::Start(r.node.0, r));
1517 values.push(Kind::End(r.node.1, r));
1522 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1524 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1525 if ra.node != rb.node {
1526 return Some((ra, rb));
1529 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1530 _ => return Some((a.range(), b.range())),
1537 mod redundant_pattern_match {
1538 use super::REDUNDANT_PATTERN_MATCHING;
1539 use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
1540 use if_chain::if_chain;
1541 use rustc_ast::ast::LitKind;
1542 use rustc_errors::Applicability;
1543 use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath};
1544 use rustc_lint::LateContext;
1545 use rustc_span::sym;
1547 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1548 if let ExprKind::Match(op, arms, ref match_source) = &expr.kind {
1549 match match_source {
1550 MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
1551 MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms, "if"),
1552 MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, arms, "while"),
1558 fn find_sugg_for_if_let<'tcx>(
1559 cx: &LateContext<'tcx>,
1560 expr: &'tcx Expr<'_>,
1563 keyword: &'static str,
1565 let good_method = match arms[0].pat.kind {
1566 PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => {
1567 if let PatKind::Wild = patterns[0].kind {
1568 if match_qpath(path, &paths::RESULT_OK) {
1570 } else if match_qpath(path, &paths::RESULT_ERR) {
1572 } else if match_qpath(path, &paths::OPTION_SOME) {
1574 } else if match_qpath(path, &paths::POLL_READY) {
1576 } else if match_qpath(path, &paths::IPADDR_V4) {
1578 } else if match_qpath(path, &paths::IPADDR_V6) {
1587 PatKind::Path(ref path) => {
1588 if match_qpath(path, &paths::OPTION_NONE) {
1590 } else if match_qpath(path, &paths::POLL_PENDING) {
1599 // check that `while_let_on_iterator` lint does not trigger
1601 if keyword == "while";
1602 if let ExprKind::MethodCall(method_path, _, _, _) = op.kind;
1603 if method_path.ident.name == sym::next;
1604 if match_trait_method(cx, op, &paths::ITERATOR);
1610 let result_expr = match &op.kind {
1611 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1616 REDUNDANT_PATTERN_MATCHING,
1618 &format!("redundant pattern matching, consider using `{}`", good_method),
1620 // while let ... = ... { ... }
1621 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1622 let expr_span = expr.span;
1624 // while let ... = ... { ... }
1626 let op_span = result_expr.span.source_callsite();
1628 // while let ... = ... { ... }
1629 // ^^^^^^^^^^^^^^^^^^^
1630 let span = expr_span.until(op_span.shrink_to_hi());
1631 diag.span_suggestion(
1634 format!("{} {}.{}", keyword, snippet(cx, op_span, "_"), good_method),
1635 Applicability::MachineApplicable, // snippet
1641 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
1642 if arms.len() == 2 {
1643 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
1645 let found_good_method = match node_pair {
1647 PatKind::TupleStruct(ref path_left, ref patterns_left, _),
1648 PatKind::TupleStruct(ref path_right, ref patterns_right, _),
1649 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
1650 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
1651 find_good_method_for_match(
1661 find_good_method_for_match(
1675 (PatKind::TupleStruct(ref path_left, ref patterns, _), PatKind::Path(ref path_right))
1676 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, ref patterns, _))
1677 if patterns.len() == 1 =>
1679 if let PatKind::Wild = patterns[0].kind {
1680 find_good_method_for_match(
1684 &paths::OPTION_SOME,
1685 &paths::OPTION_NONE,
1690 find_good_method_for_match(
1695 &paths::POLL_PENDING,
1707 if let Some(good_method) = found_good_method {
1708 let span = expr.span.to(op.span);
1709 let result_expr = match &op.kind {
1710 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1715 REDUNDANT_PATTERN_MATCHING,
1717 &format!("redundant pattern matching, consider using `{}`", good_method),
1719 diag.span_suggestion(
1722 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
1723 Applicability::MaybeIncorrect, // snippet
1731 fn find_good_method_for_match<'a>(
1733 path_left: &QPath<'_>,
1734 path_right: &QPath<'_>,
1735 expected_left: &[&str],
1736 expected_right: &[&str],
1737 should_be_left: &'a str,
1738 should_be_right: &'a str,
1739 ) -> Option<&'a str> {
1740 let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
1741 (&(*arms[0].body).kind, &(*arms[1].body).kind)
1742 } else if match_qpath(path_right, expected_left) && match_qpath(path_left, expected_right) {
1743 (&(*arms[1].body).kind, &(*arms[0].body).kind)
1748 match body_node_pair {
1749 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
1750 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
1751 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
1760 fn test_overlapping() {
1761 use rustc_span::source_map::DUMMY_SP;
1763 let sp = |s, e| SpannedRange {
1768 assert_eq!(None, overlapping::<u8>(&[]));
1769 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1772 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1777 sp(1, Bound::Included(4)),
1778 sp(5, Bound::Included(6)),
1779 sp(10, Bound::Included(11))
1783 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1784 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1787 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1789 sp(1, Bound::Included(4)),
1790 sp(5, Bound::Included(6)),
1791 sp(6, Bound::Included(11))
1796 /// Implementation of `MATCH_SAME_ARMS`.
1797 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
1798 fn same_bindings<'tcx>(lhs: &FxHashMap<Symbol, Ty<'tcx>>, rhs: &FxHashMap<Symbol, Ty<'tcx>>) -> bool {
1799 lhs.len() == rhs.len()
1802 .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| TyS::same_type(l_ty, r_ty)))
1805 if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind {
1806 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
1807 let mut h = SpanlessHash::new(cx);
1808 h.hash_expr(&arm.body);
1812 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
1813 let min_index = usize::min(lindex, rindex);
1814 let max_index = usize::max(lindex, rindex);
1816 // Arms with a guard are ignored, those can’t always be merged together
1817 // This is also the case for arms in-between each there is an arm with a guard
1818 (min_index..=max_index).all(|index| arms[index].guard.is_none()) &&
1819 SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
1820 // all patterns should have the same bindings
1821 same_bindings(&bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
1824 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
1825 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
1830 "this `match` has identical arm bodies",
1832 diag.span_note(i.body.span, "same as this");
1834 // Note: this does not use `span_suggestion` on purpose:
1835 // there is no clean way
1836 // to remove the other arm. Building a span and suggest to replace it to ""
1837 // makes an even more confusing error message. Also in order not to make up a
1838 // span for the whole pattern, the suggestion is only shown when there is only
1839 // one pattern. The user should know about `|` if they are already using it…
1841 let lhs = snippet(cx, i.pat.span, "<pat1>");
1842 let rhs = snippet(cx, j.pat.span, "<pat2>");
1844 if let PatKind::Wild = j.pat.kind {
1845 // if the last arm is _, then i could be integrated into _
1846 // note that i.pat cannot be _, because that would mean that we're
1847 // hiding all the subsequent arms, and rust won't compile
1851 "`{}` has the same arm body as the `_` wildcard, consider removing it",
1856 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs));
1864 /// Returns the list of bindings in a pattern.
1865 fn bindings<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
1866 fn bindings_impl<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
1868 PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
1869 PatKind::TupleStruct(_, pats, _) => {
1871 bindings_impl(cx, pat, map);
1874 PatKind::Binding(.., ident, ref as_pat) => {
1875 if let Entry::Vacant(v) = map.entry(ident.name) {
1876 v.insert(cx.typeck_results().pat_ty(pat));
1878 if let Some(ref as_pat) = *as_pat {
1879 bindings_impl(cx, as_pat, map);
1882 PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
1884 bindings_impl(cx, pat, map);
1887 PatKind::Struct(_, fields, _) => {
1889 bindings_impl(cx, &pat.pat, map);
1892 PatKind::Slice(lhs, ref mid, rhs) => {
1894 bindings_impl(cx, pat, map);
1896 if let Some(ref mid) = *mid {
1897 bindings_impl(cx, mid, map);
1900 bindings_impl(cx, pat, map);
1903 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
1907 let mut result = FxHashMap::default();
1908 bindings_impl(cx, pat, &mut result);