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, implements_trait, in_macro, indent_of, is_allowed, is_expn_of,
6 is_refutable, is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, meets_msrv, multispan_sugg,
7 peel_hir_pat_refs, peel_mid_ty_refs, peel_n_hir_expr_refs, remove_blocks, snippet, snippet_block, snippet_opt,
8 snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
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
696 // not a block, don't lint
700 let ty = cx.typeck_results().expr_ty(ex);
701 if *ty.kind() != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
702 check_single_match_single_pattern(cx, ex, arms, expr, els);
703 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
708 fn check_single_match_single_pattern(
709 cx: &LateContext<'_>,
713 els: Option<&Expr<'_>>,
715 if is_wild(&arms[1].pat) {
716 report_single_match_single_pattern(cx, ex, arms, expr, els);
720 fn report_single_match_single_pattern(
721 cx: &LateContext<'_>,
725 els: Option<&Expr<'_>>,
727 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
728 let els_str = els.map_or(String::new(), |els| {
729 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
732 let (msg, sugg) = if_chain! {
733 let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat);
734 if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind;
735 let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex));
736 if let Some(trait_id) = cx.tcx.lang_items().structural_peq_trait();
737 if ty.is_integral() || ty.is_char() || ty.is_str() || implements_trait(cx, ty, trait_id, &[]);
739 // scrutinee derives PartialEq and the pattern is a constant.
740 let pat_ref_count = match pat.kind {
741 // string literals are already a reference.
742 PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1,
745 // References are only implicitly added to the pattern, so no overflow here.
746 // e.g. will work: match &Some(_) { Some(_) => () }
747 // will not: match Some(_) { &Some(_) => () }
748 let ref_count_diff = ty_ref_count - pat_ref_count;
750 // Try to remove address of expressions first.
751 let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff);
752 let ref_count_diff = ref_count_diff - removed;
754 let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`";
756 "if {} == {}{} {}{}",
757 snippet(cx, ex.span, ".."),
758 // PartialEq for different reference counts may not exist.
759 "&".repeat(ref_count_diff),
760 snippet(cx, arms[0].pat.span, ".."),
761 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
766 let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`";
768 "if let {} = {} {}{}",
769 snippet(cx, arms[0].pat.span, ".."),
770 snippet(cx, ex.span, ".."),
771 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
785 Applicability::HasPlaceholders,
789 fn check_single_match_opt_like(
790 cx: &LateContext<'_>,
795 els: Option<&Expr<'_>>,
797 // list of candidate `Enum`s we know will never get any more members
799 (&paths::COW, "Borrowed"),
800 (&paths::COW, "Cow::Borrowed"),
801 (&paths::COW, "Cow::Owned"),
802 (&paths::COW, "Owned"),
803 (&paths::OPTION, "None"),
804 (&paths::RESULT, "Err"),
805 (&paths::RESULT, "Ok"),
808 let path = match arms[1].pat.kind {
809 PatKind::TupleStruct(ref path, ref inner, _) => {
810 // Contains any non wildcard patterns (e.g., `Err(err)`)?
811 if !inner.iter().all(is_wild) {
814 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
816 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
817 PatKind::Path(ref path) => {
818 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
823 for &(ty_path, pat_path) in candidates {
824 if path == *pat_path && match_type(cx, ty, ty_path) {
825 report_single_match_single_pattern(cx, ex, arms, expr, els);
830 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
831 // Type of expression is `bool`.
832 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
837 "you seem to be trying to match on a boolean expression",
841 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
842 if let ExprKind::Lit(ref lit) = arm_bool.kind {
844 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
845 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
855 if let Some((true_expr, false_expr)) = exprs {
856 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
857 (false, false) => Some(format!(
859 snippet(cx, ex.span, "b"),
860 expr_block(cx, true_expr, None, "..", Some(expr.span)),
861 expr_block(cx, false_expr, None, "..", Some(expr.span))
863 (false, true) => Some(format!(
865 snippet(cx, ex.span, "b"),
866 expr_block(cx, true_expr, None, "..", Some(expr.span))
869 let test = Sugg::hir(cx, ex, "..");
873 expr_block(cx, false_expr, None, "..", Some(expr.span))
876 (true, true) => None,
879 if let Some(sugg) = sugg {
880 diag.span_suggestion(
882 "consider using an `if`/`else` expression",
884 Applicability::HasPlaceholders,
894 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
895 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
896 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
897 let type_ranges = type_ranges(&ranges);
898 if !type_ranges.is_empty() {
899 if let Some((start, end)) = overlapping(&type_ranges) {
902 MATCH_OVERLAPPING_ARM,
904 "some ranges overlap",
906 "overlaps with this",
913 fn check_wild_err_arm(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
914 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
915 if is_type_diagnostic_item(cx, ex_ty, sym::result_type) {
917 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
918 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
919 if path_str == "Err" {
920 let mut matching_wild = inner.iter().any(is_wild);
921 let mut ident_bind_name = String::from("_");
923 // Looking for unused bindings (i.e.: `_e`)
924 inner.iter().for_each(|pat| {
925 if let PatKind::Binding(.., ident, None) = &pat.kind {
926 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
927 ident_bind_name = (&ident.name.as_str()).to_string();
928 matching_wild = true;
935 if let ExprKind::Block(ref block, _) = arm.body.kind;
936 if is_panic_block(block);
938 // `Err(_)` or `Err(_e)` arm with `panic!` found
939 span_lint_and_note(cx,
942 &format!("`Err({})` matches all errors", &ident_bind_name),
944 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
954 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
955 let ty = cx.typeck_results().expr_ty(ex);
957 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
958 // don't complain about not enumerating the mall.
962 // First pass - check for violation, but don't do much book-keeping because this is hopefully
963 // the uncommon case, and the book-keeping is slightly expensive.
964 let mut wildcard_span = None;
965 let mut wildcard_ident = None;
967 if let PatKind::Wild = arm.pat.kind {
968 wildcard_span = Some(arm.pat.span);
969 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
970 wildcard_span = Some(arm.pat.span);
971 wildcard_ident = Some(ident);
975 if let Some(wildcard_span) = wildcard_span {
976 // Accumulate the variants which should be put in place of the wildcard because they're not
979 let mut missing_variants = vec![];
980 if let ty::Adt(def, _) = ty.kind() {
981 for variant in &def.variants {
982 missing_variants.push(variant);
987 if arm.guard.is_some() {
988 // Guards mean that this case probably isn't exhaustively covered. Technically
989 // this is incorrect, as we should really check whether each variant is exhaustively
990 // covered by the set of guards that cover it, but that's really hard to do.
993 if let PatKind::Path(ref path) = arm.pat.kind {
994 if let QPath::Resolved(_, p) = path {
995 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
997 } else if let PatKind::TupleStruct(QPath::Resolved(_, p), ref patterns, ..) = arm.pat.kind {
998 // Some simple checks for exhaustive patterns.
999 // There is a room for improvements to detect more cases,
1000 // but it can be more expensive to do so.
1001 let is_pattern_exhaustive =
1002 |pat: &&Pat<'_>| matches!(pat.kind, PatKind::Wild | PatKind::Binding(.., None));
1003 if patterns.iter().all(is_pattern_exhaustive) {
1004 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
1009 let mut suggestion: Vec<String> = missing_variants
1012 let suffix = match v.ctor_kind {
1013 CtorKind::Fn => "(..)",
1014 CtorKind::Const | CtorKind::Fictive => "",
1016 let ident_str = if let Some(ident) = wildcard_ident {
1017 format!("{} @ ", ident.name)
1021 // This path assumes that the enum type is imported into scope.
1022 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
1026 if suggestion.is_empty() {
1030 let mut message = "wildcard match will miss any future added variants";
1032 if let ty::Adt(def, _) = ty.kind() {
1033 if def.is_variant_list_non_exhaustive() {
1034 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
1035 suggestion.push(String::from("_"));
1039 if suggestion.len() == 1 {
1040 // No need to check for non-exhaustive enum as in that case len would be greater than 1
1043 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1047 suggestion[0].clone(),
1048 Applicability::MaybeIncorrect,
1054 WILDCARD_ENUM_MATCH_ARM,
1058 suggestion.join(" | "),
1059 Applicability::MaybeIncorrect,
1064 // If the block contains only a `panic!` macro (as expression or statement)
1065 fn is_panic_block(block: &Block<'_>) -> bool {
1066 match (&block.expr, block.stmts.len(), block.stmts.first()) {
1067 (&Some(ref exp), 0, _) => {
1068 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
1070 (&None, 1, Some(stmt)) => {
1071 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
1077 fn check_match_ref_pats(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1078 if has_only_ref_pats(arms) {
1079 let mut suggs = Vec::with_capacity(arms.len() + 1);
1080 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
1081 let span = ex.span.source_callsite();
1082 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1084 "you don't need to add `&` to both the expression and the patterns",
1088 let span = ex.span.source_callsite();
1089 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1091 "you don't need to add `&` to all patterns",
1092 "instead of prefixing all patterns with `&`, you can dereference the expression",
1096 suggs.extend(arms.iter().filter_map(|a| {
1097 if let PatKind::Ref(ref refp, _) = a.pat.kind {
1098 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
1104 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1105 if !expr.span.from_expansion() {
1106 multispan_sugg(diag, msg, suggs);
1112 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1113 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1114 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
1115 is_ref_some_arm(&arms[1])
1116 } else if is_none_arm(&arms[1]) {
1117 is_ref_some_arm(&arms[0])
1121 if let Some(rb) = arm_ref {
1122 let suggestion = if rb == BindingAnnotation::Ref {
1128 let output_ty = cx.typeck_results().expr_ty(expr);
1129 let input_ty = cx.typeck_results().expr_ty(ex);
1131 let cast = if_chain! {
1132 if let ty::Adt(_, substs) = input_ty.kind();
1133 let input_ty = substs.type_at(0);
1134 if let ty::Adt(_, substs) = output_ty.kind();
1135 let output_ty = substs.type_at(0);
1136 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1137 if input_ty != output_ty;
1145 let mut applicability = Applicability::MachineApplicable;
1150 &format!("use `{}()` instead", suggestion),
1154 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1164 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1166 if let PatKind::Or(ref fields) = arm.pat.kind {
1167 // look for multiple fields in this arm that contains at least one Wild pattern
1168 if fields.len() > 1 && fields.iter().any(is_wild) {
1171 WILDCARD_IN_OR_PATTERNS,
1173 "wildcard pattern covers any other pattern as it will match anyway.",
1175 "Consider handling `_` separately.",
1182 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1183 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1184 if let ExprKind::Match(ex, arms, ref match_source) = &expr.kind {
1185 match match_source {
1186 MatchSource::Normal => find_matches_sugg(cx, ex, arms, expr, false),
1187 MatchSource::IfLetDesugar { .. } => find_matches_sugg(cx, ex, arms, expr, true),
1195 /// Lint a `match` or desugared `if let` for replacement by `matches!`
1196 fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, desugared: bool) -> bool {
1199 if cx.typeck_results().expr_ty(expr).is_bool();
1200 if let Some((b1_arm, b0_arms)) = arms.split_last();
1201 if let Some(b0) = find_bool_lit(&b0_arms[0].body.kind, desugared);
1202 if let Some(b1) = find_bool_lit(&b1_arm.body.kind, desugared);
1203 if is_wild(&b1_arm.pat);
1205 let if_guard = &b0_arms[0].guard;
1206 if if_guard.is_none() || b0_arms.len() == 1;
1207 if b0_arms[0].attrs.is_empty();
1208 if b0_arms[1..].iter()
1210 find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) &&
1211 arm.guard.is_none() && arm.attrs.is_empty()
1214 // The suggestion may be incorrect, because some arms can have `cfg` attributes
1215 // evaluated into `false` and so such arms will be stripped before.
1216 let mut applicability = Applicability::MaybeIncorrect;
1218 use itertools::Itertools as _;
1220 .map(|arm| snippet_with_applicability(cx, arm.pat.span, "..", &mut applicability))
1223 let pat_and_guard = if let Some(Guard::If(g)) = if_guard {
1224 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1230 MATCH_LIKE_MATCHES_MACRO,
1232 &format!("{} expression looks like `matches!` macro", if desugared { "if let .. else" } else { "match" }),
1235 "{}matches!({}, {})",
1236 if b0 { "" } else { "!" },
1237 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1249 /// Extract a `bool` or `{ bool }`
1250 fn find_bool_lit(ex: &ExprKind<'_>, desugared: bool) -> Option<bool> {
1252 ExprKind::Lit(Spanned {
1253 node: LitKind::Bool(b), ..
1263 if let ExprKind::Lit(Spanned {
1264 node: LitKind::Bool(b), ..
1276 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1277 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1282 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1283 // to prevent false positives as there is currently no better way to detect if code was excluded by
1284 // a macro. See PR #6435
1286 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1287 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1288 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1289 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1290 if rest_snippet.contains("=>");
1292 // The code it self contains another thick arrow "=>"
1293 // -> Either another arm or a comment
1298 let matched_vars = ex.span;
1299 let bind_names = arms[0].pat.span;
1300 let match_body = remove_blocks(&arms[0].body);
1301 let mut snippet_body = if match_body.span.from_expansion() {
1302 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1304 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1307 // Do we need to add ';' to suggestion ?
1308 match match_body.kind {
1309 ExprKind::Block(block, _) => {
1310 // macro + expr_ty(body) == ()
1311 if block.span.from_expansion() && cx.typeck_results().expr_ty(&match_body).is_unit() {
1312 snippet_body.push(';');
1316 // expr_ty(body) == ()
1317 if cx.typeck_results().expr_ty(&match_body).is_unit() {
1318 snippet_body.push(';');
1323 let mut applicability = Applicability::MaybeIncorrect;
1324 match arms[0].pat.kind {
1325 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1326 // If this match is in a local (`let`) stmt
1327 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1329 parent_let_node.span,
1331 "let {} = {};\n{}let {} = {};",
1332 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1333 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1334 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1335 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1340 // If we are in closure, we need curly braces around suggestion
1341 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1342 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1343 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1344 if let ExprKind::Closure(..) = parent_expr.kind {
1345 cbrace_end = format!("\n{}}}", indent);
1346 // Fix body indent due to the closure
1347 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1348 cbrace_start = format!("{{\n{}", indent);
1354 "{}let {} = {};\n{}{}{}",
1356 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1357 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1366 MATCH_SINGLE_BINDING,
1368 "this match could be written as a `let` statement",
1369 "consider using `let` statement",
1377 MATCH_SINGLE_BINDING,
1379 "this match could be replaced by its body itself",
1380 "consider using the match body instead",
1382 Applicability::MachineApplicable,
1389 /// Returns true if the `ex` match expression is in a local (`let`) statement
1390 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1392 let map = &cx.tcx.hir();
1393 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1394 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1396 return Some(parent_let_expr);
1402 /// Gets all arms that are unbounded `PatRange`s.
1403 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<Constant>> {
1407 ref pat, guard: None, ..
1410 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1411 let lhs = match lhs {
1412 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1413 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1415 let rhs = match rhs {
1416 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1417 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1419 let rhs = match range_end {
1420 RangeEnd::Included => Bound::Included(rhs),
1421 RangeEnd::Excluded => Bound::Excluded(rhs),
1423 return Some(SpannedRange {
1429 if let PatKind::Lit(ref value) = pat.kind {
1430 let value = constant(cx, cx.typeck_results(), value)?.0;
1431 return Some(SpannedRange {
1433 node: (value.clone(), Bound::Included(value)),
1442 #[derive(Debug, Eq, PartialEq)]
1443 pub struct SpannedRange<T> {
1445 pub node: (T, Bound<T>),
1448 type TypedRanges = Vec<SpannedRange<u128>>;
1450 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1451 /// and other types than
1452 /// `Uint` and `Int` probably don't make sense.
1453 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1456 .filter_map(|range| match range.node {
1457 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1459 node: (start, Bound::Included(end)),
1461 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1463 node: (start, Bound::Excluded(end)),
1465 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1467 node: (start, Bound::Unbounded),
1474 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1476 ExprKind::Tup(ref v) if v.is_empty() => true,
1477 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1482 // Checks if arm has the form `None => None`
1483 fn is_none_arm(arm: &Arm<'_>) -> bool {
1484 matches!(arm.pat.kind, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE))
1487 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1488 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1490 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1491 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1492 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1493 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1494 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1495 if let ExprKind::Path(ref some_path) = e.kind;
1496 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1497 if let ExprKind::Path(QPath::Resolved(_, ref path2)) = args[0].kind;
1498 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1506 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1511 PatKind::Ref(..) => Some(true), // &-patterns
1512 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1513 _ => None, // any other pattern is not fine
1516 .collect::<Option<Vec<bool>>>();
1517 // look for Some(v) where there's at least one true element
1518 mapped.map_or(false, |v| v.iter().any(|el| *el))
1521 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1525 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1527 Start(T, &'a SpannedRange<T>),
1528 End(Bound<T>, &'a SpannedRange<T>),
1531 impl<'a, T: Copy> Kind<'a, T> {
1532 fn range(&self) -> &'a SpannedRange<T> {
1534 Kind::Start(_, r) | Kind::End(_, r) => r,
1538 fn value(self) -> Bound<T> {
1540 Kind::Start(t, _) => Bound::Included(t),
1541 Kind::End(t, _) => t,
1546 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1547 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1548 Some(self.cmp(other))
1552 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1553 fn cmp(&self, other: &Self) -> Ordering {
1554 match (self.value(), other.value()) {
1555 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1556 // Range patterns cannot be unbounded (yet)
1557 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1558 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1559 Ordering::Equal => Ordering::Greater,
1562 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1563 Ordering::Equal => Ordering::Less,
1570 let mut values = Vec::with_capacity(2 * ranges.len());
1573 values.push(Kind::Start(r.node.0, r));
1574 values.push(Kind::End(r.node.1, r));
1579 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1581 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1582 if ra.node != rb.node {
1583 return Some((ra, rb));
1586 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1587 _ => return Some((a.range(), b.range())),
1594 mod redundant_pattern_match {
1595 use super::REDUNDANT_PATTERN_MATCHING;
1596 use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
1597 use if_chain::if_chain;
1598 use rustc_ast::ast::LitKind;
1599 use rustc_errors::Applicability;
1600 use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath};
1601 use rustc_lint::LateContext;
1602 use rustc_span::sym;
1604 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1605 if let ExprKind::Match(op, arms, ref match_source) = &expr.kind {
1606 match match_source {
1607 MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
1608 MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms, "if"),
1609 MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, arms, "while"),
1615 fn find_sugg_for_if_let<'tcx>(
1616 cx: &LateContext<'tcx>,
1617 expr: &'tcx Expr<'_>,
1620 keyword: &'static str,
1622 let good_method = match arms[0].pat.kind {
1623 PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => {
1624 if let PatKind::Wild = patterns[0].kind {
1625 if match_qpath(path, &paths::RESULT_OK) {
1627 } else if match_qpath(path, &paths::RESULT_ERR) {
1629 } else if match_qpath(path, &paths::OPTION_SOME) {
1631 } else if match_qpath(path, &paths::POLL_READY) {
1633 } else if match_qpath(path, &paths::IPADDR_V4) {
1635 } else if match_qpath(path, &paths::IPADDR_V6) {
1644 PatKind::Path(ref path) => {
1645 if match_qpath(path, &paths::OPTION_NONE) {
1647 } else if match_qpath(path, &paths::POLL_PENDING) {
1656 // check that `while_let_on_iterator` lint does not trigger
1658 if keyword == "while";
1659 if let ExprKind::MethodCall(method_path, _, _, _) = op.kind;
1660 if method_path.ident.name == sym::next;
1661 if match_trait_method(cx, op, &paths::ITERATOR);
1667 let result_expr = match &op.kind {
1668 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1673 REDUNDANT_PATTERN_MATCHING,
1675 &format!("redundant pattern matching, consider using `{}`", good_method),
1677 // while let ... = ... { ... }
1678 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1679 let expr_span = expr.span;
1681 // while let ... = ... { ... }
1683 let op_span = result_expr.span.source_callsite();
1685 // while let ... = ... { ... }
1686 // ^^^^^^^^^^^^^^^^^^^
1687 let span = expr_span.until(op_span.shrink_to_hi());
1688 diag.span_suggestion(
1691 format!("{} {}.{}", keyword, snippet(cx, op_span, "_"), good_method),
1692 Applicability::MachineApplicable, // snippet
1698 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
1699 if arms.len() == 2 {
1700 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
1702 let found_good_method = match node_pair {
1704 PatKind::TupleStruct(ref path_left, ref patterns_left, _),
1705 PatKind::TupleStruct(ref path_right, ref patterns_right, _),
1706 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
1707 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
1708 find_good_method_for_match(
1718 find_good_method_for_match(
1732 (PatKind::TupleStruct(ref path_left, ref patterns, _), PatKind::Path(ref path_right))
1733 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, ref patterns, _))
1734 if patterns.len() == 1 =>
1736 if let PatKind::Wild = patterns[0].kind {
1737 find_good_method_for_match(
1741 &paths::OPTION_SOME,
1742 &paths::OPTION_NONE,
1747 find_good_method_for_match(
1752 &paths::POLL_PENDING,
1764 if let Some(good_method) = found_good_method {
1765 let span = expr.span.to(op.span);
1766 let result_expr = match &op.kind {
1767 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1772 REDUNDANT_PATTERN_MATCHING,
1774 &format!("redundant pattern matching, consider using `{}`", good_method),
1776 diag.span_suggestion(
1779 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
1780 Applicability::MaybeIncorrect, // snippet
1788 fn find_good_method_for_match<'a>(
1790 path_left: &QPath<'_>,
1791 path_right: &QPath<'_>,
1792 expected_left: &[&str],
1793 expected_right: &[&str],
1794 should_be_left: &'a str,
1795 should_be_right: &'a str,
1796 ) -> Option<&'a str> {
1797 let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
1798 (&(*arms[0].body).kind, &(*arms[1].body).kind)
1799 } else if match_qpath(path_right, expected_left) && match_qpath(path_left, expected_right) {
1800 (&(*arms[1].body).kind, &(*arms[0].body).kind)
1805 match body_node_pair {
1806 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
1807 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
1808 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
1817 fn test_overlapping() {
1818 use rustc_span::source_map::DUMMY_SP;
1820 let sp = |s, e| SpannedRange {
1825 assert_eq!(None, overlapping::<u8>(&[]));
1826 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1829 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1834 sp(1, Bound::Included(4)),
1835 sp(5, Bound::Included(6)),
1836 sp(10, Bound::Included(11))
1840 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1841 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1844 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1846 sp(1, Bound::Included(4)),
1847 sp(5, Bound::Included(6)),
1848 sp(6, Bound::Included(11))
1853 /// Implementation of `MATCH_SAME_ARMS`.
1854 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
1855 fn same_bindings<'tcx>(lhs: &FxHashMap<Symbol, Ty<'tcx>>, rhs: &FxHashMap<Symbol, Ty<'tcx>>) -> bool {
1856 lhs.len() == rhs.len()
1859 .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| TyS::same_type(l_ty, r_ty)))
1862 if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind {
1863 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
1864 let mut h = SpanlessHash::new(cx);
1865 h.hash_expr(&arm.body);
1869 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
1870 let min_index = usize::min(lindex, rindex);
1871 let max_index = usize::max(lindex, rindex);
1873 // Arms with a guard are ignored, those can’t always be merged together
1874 // This is also the case for arms in-between each there is an arm with a guard
1875 (min_index..=max_index).all(|index| arms[index].guard.is_none()) &&
1876 SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
1877 // all patterns should have the same bindings
1878 same_bindings(&bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
1881 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
1882 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
1887 "this `match` has identical arm bodies",
1889 diag.span_note(i.body.span, "same as this");
1891 // Note: this does not use `span_suggestion` on purpose:
1892 // there is no clean way
1893 // to remove the other arm. Building a span and suggest to replace it to ""
1894 // makes an even more confusing error message. Also in order not to make up a
1895 // span for the whole pattern, the suggestion is only shown when there is only
1896 // one pattern. The user should know about `|` if they are already using it…
1898 let lhs = snippet(cx, i.pat.span, "<pat1>");
1899 let rhs = snippet(cx, j.pat.span, "<pat2>");
1901 if let PatKind::Wild = j.pat.kind {
1902 // if the last arm is _, then i could be integrated into _
1903 // note that i.pat cannot be _, because that would mean that we're
1904 // hiding all the subsequent arms, and rust won't compile
1908 "`{}` has the same arm body as the `_` wildcard, consider removing it",
1913 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs));
1921 /// Returns the list of bindings in a pattern.
1922 fn bindings<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
1923 fn bindings_impl<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
1925 PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
1926 PatKind::TupleStruct(_, pats, _) => {
1928 bindings_impl(cx, pat, map);
1931 PatKind::Binding(.., ident, ref as_pat) => {
1932 if let Entry::Vacant(v) = map.entry(ident.name) {
1933 v.insert(cx.typeck_results().pat_ty(pat));
1935 if let Some(ref as_pat) = *as_pat {
1936 bindings_impl(cx, as_pat, map);
1939 PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
1941 bindings_impl(cx, pat, map);
1944 PatKind::Struct(_, fields, _) => {
1946 bindings_impl(cx, &pat.pat, map);
1949 PatKind::Slice(lhs, ref mid, rhs) => {
1951 bindings_impl(cx, pat, map);
1953 if let Some(ref mid) = *mid {
1954 bindings_impl(cx, mid, map);
1957 bindings_impl(cx, pat, map);
1960 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
1964 let mut result = FxHashMap::default();
1965 bindings_impl(cx, pat, &mut result);