1 use clippy_utils::consts::{constant, constant_full_int, miri_to_const, FullInt};
2 use clippy_utils::diagnostics::{
3 multispan_sugg, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
5 use clippy_utils::macros::{is_panic, root_macro_call};
6 use clippy_utils::peel_blocks_with_stmt;
7 use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
8 use clippy_utils::sugg::Sugg;
9 use clippy_utils::ty::is_type_diagnostic_item;
10 use clippy_utils::visitors::is_local_used;
12 get_parent_expr, is_lang_ctor, is_refutable, is_unit_expr, is_wild, meets_msrv, msrvs, path_to_local_id,
13 peel_blocks, peel_hir_pat_refs, recurse_or_patterns, strip_pat_refs,
16 use if_chain::if_chain;
17 use rustc_ast::ast::LitKind;
18 use rustc_errors::Applicability;
19 use rustc_hir::def::{CtorKind, DefKind, Res};
20 use rustc_hir::LangItem::{OptionNone, OptionSome};
22 self as hir, Arm, BindingAnnotation, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat,
23 PatKind, PathSegment, QPath, RangeEnd, TyKind,
25 use rustc_lint::{LateContext, LateLintPass};
26 use rustc_middle::ty::{self, Ty, VariantDef};
27 use rustc_semver::RustcVersion;
28 use rustc_session::{declare_tool_lint, impl_lint_pass};
29 use rustc_span::{sym, symbol::kw, Span};
30 use std::cmp::Ordering;
32 mod match_like_matches;
34 mod redundant_pattern_match;
37 declare_clippy_lint! {
39 /// Checks for matches with a single arm where an `if let`
40 /// will usually suffice.
42 /// ### Why is this bad?
43 /// Just readability – `if let` nests less than a `match`.
47 /// # fn bar(stool: &str) {}
48 /// # let x = Some("abc");
51 /// Some(ref foo) => bar(foo),
56 /// if let Some(ref foo) = x {
60 #[clippy::version = "pre 1.29.0"]
63 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
66 declare_clippy_lint! {
68 /// Checks for matches with two arms where an `if let else` will
71 /// ### Why is this bad?
72 /// Just readability – `if let` nests less than a `match`.
74 /// ### Known problems
75 /// Personal style preferences may differ.
81 /// # fn bar(foo: &usize) {}
82 /// # let other_ref: usize = 1;
83 /// # let x: Option<&usize> = Some(&1);
85 /// Some(ref foo) => bar(foo),
86 /// _ => bar(&other_ref),
90 /// Using `if let` with `else`:
93 /// # fn bar(foo: &usize) {}
94 /// # let other_ref: usize = 1;
95 /// # let x: Option<&usize> = Some(&1);
96 /// if let Some(ref foo) = x {
102 #[clippy::version = "pre 1.29.0"]
103 pub SINGLE_MATCH_ELSE,
105 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
108 declare_clippy_lint! {
110 /// Checks for matches where all arms match a reference,
111 /// suggesting to remove the reference and deref the matched expression
112 /// instead. It also checks for `if let &foo = bar` blocks.
114 /// ### Why is this bad?
115 /// It just makes the code less readable. That reference
116 /// destructuring adds nothing to the code.
122 /// &A(ref y) => foo(y),
129 /// A(ref y) => foo(y),
134 #[clippy::version = "pre 1.29.0"]
137 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
140 declare_clippy_lint! {
142 /// Checks for matches where match expression is a `bool`. It
143 /// suggests to replace the expression with an `if...else` block.
145 /// ### Why is this bad?
146 /// It makes the code less readable.
152 /// let condition: bool = true;
153 /// match condition {
158 /// Use if/else instead:
162 /// let condition: bool = true;
169 #[clippy::version = "pre 1.29.0"]
172 "a `match` on a boolean expression instead of an `if..else` block"
175 declare_clippy_lint! {
177 /// Checks for overlapping match arms.
179 /// ### Why is this bad?
180 /// It is likely to be an error and if not, makes the code
187 /// 1..=10 => println!("1 ... 10"),
188 /// 5..=15 => println!("5 ... 15"),
192 #[clippy::version = "pre 1.29.0"]
193 pub MATCH_OVERLAPPING_ARM,
195 "a `match` with overlapping arms"
198 declare_clippy_lint! {
200 /// Checks for arm which matches all errors with `Err(_)`
201 /// and take drastic actions like `panic!`.
203 /// ### Why is this bad?
204 /// It is generally a bad practice, similar to
205 /// catching all exceptions in java with `catch(Exception)`
209 /// let x: Result<i32, &str> = Ok(3);
211 /// Ok(_) => println!("ok"),
212 /// Err(_) => panic!("err"),
215 #[clippy::version = "pre 1.29.0"]
216 pub MATCH_WILD_ERR_ARM,
218 "a `match` with `Err(_)` arm and take drastic actions"
221 declare_clippy_lint! {
223 /// Checks for match which is used to add a reference to an
226 /// ### Why is this bad?
227 /// Using `as_ref()` or `as_mut()` instead is shorter.
231 /// let x: Option<()> = None;
234 /// let r: Option<&()> = match x {
236 /// Some(ref v) => Some(v),
240 /// let r: Option<&()> = x.as_ref();
242 #[clippy::version = "pre 1.29.0"]
245 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
248 declare_clippy_lint! {
250 /// Checks for wildcard enum matches using `_`.
252 /// ### Why is this bad?
253 /// New enum variants added by library updates can be missed.
255 /// ### Known problems
256 /// Suggested replacements may be incorrect if guards exhaustively cover some
257 /// variants, and also may not use correct path to enum if it's not present in the current scope.
261 /// # enum Foo { A(usize), B(usize) }
262 /// # let x = Foo::B(1);
275 #[clippy::version = "1.34.0"]
276 pub WILDCARD_ENUM_MATCH_ARM,
278 "a wildcard enum match arm using `_`"
281 declare_clippy_lint! {
283 /// Checks for wildcard enum matches for a single variant.
285 /// ### Why is this bad?
286 /// New enum variants added by library updates can be missed.
288 /// ### Known problems
289 /// Suggested replacements may not use correct path to enum
290 /// if it's not present in the current scope.
294 /// # enum Foo { A, B, C }
295 /// # let x = Foo::B;
310 #[clippy::version = "1.45.0"]
311 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
313 "a wildcard enum match for a single variant"
316 declare_clippy_lint! {
318 /// Checks for wildcard pattern used with others patterns in same match arm.
320 /// ### Why is this bad?
321 /// Wildcard pattern already covers any other pattern as it will match anyway.
322 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
338 #[clippy::version = "1.42.0"]
339 pub WILDCARD_IN_OR_PATTERNS,
341 "a wildcard pattern used with others patterns in same match arm"
344 declare_clippy_lint! {
346 /// Checks for matches being used to destructure a single-variant enum
347 /// or tuple struct where a `let` will suffice.
349 /// ### Why is this bad?
350 /// Just readability – `let` doesn't nest, whereas a `match` does.
358 /// let wrapper = Wrapper::Data(42);
360 /// let data = match wrapper {
361 /// Wrapper::Data(i) => i,
365 /// The correct use would be:
371 /// let wrapper = Wrapper::Data(42);
372 /// let Wrapper::Data(data) = wrapper;
374 #[clippy::version = "pre 1.29.0"]
375 pub INFALLIBLE_DESTRUCTURING_MATCH,
377 "a `match` statement with a single infallible arm instead of a `let`"
380 declare_clippy_lint! {
382 /// Checks for useless match that binds to only one value.
384 /// ### Why is this bad?
385 /// Readability and needless complexity.
387 /// ### Known problems
388 /// Suggested replacements may be incorrect when `match`
389 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
404 /// let (c, d) = (a, b);
406 #[clippy::version = "1.43.0"]
407 pub MATCH_SINGLE_BINDING,
409 "a match with a single binding instead of using `let` statement"
412 declare_clippy_lint! {
414 /// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
416 /// ### Why is this bad?
417 /// Correctness and readability. It's like having a wildcard pattern after
418 /// matching all enum variants explicitly.
422 /// # struct A { a: i32 }
423 /// let a = A { a: 5 };
427 /// A { a: 5, .. } => {},
433 /// A { a: 5 } => {},
437 #[clippy::version = "1.43.0"]
438 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
440 "a match on a struct that binds all fields but still uses the wildcard pattern"
443 declare_clippy_lint! {
445 /// Lint for redundant pattern matching over `Result`, `Option`,
446 /// `std::task::Poll` or `std::net::IpAddr`
448 /// ### Why is this bad?
449 /// It's more concise and clear to just use the proper
452 /// ### Known problems
453 /// This will change the drop order for the matched type. Both `if let` and
454 /// `while let` will drop the value at the end of the block, both `if` and `while` will drop the
455 /// value before entering the block. For most types this change will not matter, but for a few
456 /// types this will not be an acceptable change (e.g. locks). See the
457 /// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about
462 /// # use std::task::Poll;
463 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
464 /// if let Ok(_) = Ok::<i32, i32>(42) {}
465 /// if let Err(_) = Err::<i32, i32>(42) {}
466 /// if let None = None::<()> {}
467 /// if let Some(_) = Some(42) {}
468 /// if let Poll::Pending = Poll::Pending::<()> {}
469 /// if let Poll::Ready(_) = Poll::Ready(42) {}
470 /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
471 /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
472 /// match Ok::<i32, i32>(42) {
478 /// The more idiomatic use would be:
481 /// # use std::task::Poll;
482 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
483 /// if Ok::<i32, i32>(42).is_ok() {}
484 /// if Err::<i32, i32>(42).is_err() {}
485 /// if None::<()>.is_none() {}
486 /// if Some(42).is_some() {}
487 /// if Poll::Pending::<()>.is_pending() {}
488 /// if Poll::Ready(42).is_ready() {}
489 /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
490 /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
491 /// Ok::<i32, i32>(42).is_ok();
493 #[clippy::version = "1.31.0"]
494 pub REDUNDANT_PATTERN_MATCHING,
496 "use the proper utility function avoiding an `if let`"
499 declare_clippy_lint! {
501 /// Checks for `match` or `if let` expressions producing a
502 /// `bool` that could be written using `matches!`
504 /// ### Why is this bad?
505 /// Readability and needless complexity.
507 /// ### Known problems
508 /// This lint falsely triggers, if there are arms with
509 /// `cfg` attributes that remove an arm evaluating to `false`.
516 /// let a = match x {
521 /// let a = if let Some(0) = x {
528 /// let a = matches!(x, Some(0));
530 #[clippy::version = "1.47.0"]
531 pub MATCH_LIKE_MATCHES_MACRO,
533 "a match that could be written with the matches! macro"
536 declare_clippy_lint! {
538 /// Checks for `match` with identical arm bodies.
540 /// ### Why is this bad?
541 /// This is probably a copy & paste error. If arm bodies
542 /// are the same on purpose, you can factor them
543 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
545 /// ### Known problems
546 /// False positive possible with order dependent `match`
548 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
555 /// Baz => bar(), // <= oops
559 /// This should probably be
564 /// Baz => baz(), // <= fixed
568 /// or if the original code was not a typo:
571 /// Bar | Baz => bar(), // <= shows the intent better
575 #[clippy::version = "pre 1.29.0"]
578 "`match` with identical arm bodies"
583 msrv: Option<RustcVersion>,
584 infallible_destructuring_match_linted: bool,
589 pub fn new(msrv: Option<RustcVersion>) -> Self {
597 impl_lint_pass!(Matches => [
602 MATCH_OVERLAPPING_ARM,
605 WILDCARD_ENUM_MATCH_ARM,
606 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
607 WILDCARD_IN_OR_PATTERNS,
608 MATCH_SINGLE_BINDING,
609 INFALLIBLE_DESTRUCTURING_MATCH,
610 REST_PAT_IN_FULLY_BOUND_STRUCTS,
611 REDUNDANT_PATTERN_MATCHING,
612 MATCH_LIKE_MATCHES_MACRO,
616 impl<'tcx> LateLintPass<'tcx> for Matches {
617 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
618 if expr.span.from_expansion() {
622 redundant_pattern_match::check(cx, expr);
624 if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) {
625 if !match_like_matches::check(cx, expr) {
626 match_same_arms::check(cx, expr);
629 match_same_arms::check(cx, expr);
632 if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
633 single_match::check(cx, ex, arms, expr);
634 check_match_bool(cx, ex, arms, expr);
635 check_overlapping_arms(cx, ex, arms);
636 check_wild_err_arm(cx, ex, arms);
637 check_wild_enum_match(cx, ex, arms);
638 check_match_as_ref(cx, ex, arms, expr);
639 check_wild_in_or_pats(cx, arms);
641 if self.infallible_destructuring_match_linted {
642 self.infallible_destructuring_match_linted = false;
644 check_match_single_binding(cx, ex, arms, expr);
647 if let ExprKind::Match(ex, arms, _) = expr.kind {
648 check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr);
652 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
654 if !local.span.from_expansion();
655 if let Some(expr) = local.init;
656 if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
657 if arms.len() == 1 && arms[0].guard.is_none();
658 if let PatKind::TupleStruct(
659 QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
661 if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
662 let body = peel_blocks(arms[0].body);
663 if path_to_local_id(body, arg);
666 let mut applicability = Applicability::MachineApplicable;
667 self.infallible_destructuring_match_linted = true;
670 INFALLIBLE_DESTRUCTURING_MATCH,
672 "you seem to be trying to use `match` to destructure a single infallible pattern. \
673 Consider using `let`",
677 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
678 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
679 snippet_with_applicability(cx, target.span, "..", &mut applicability),
687 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
689 if !pat.span.from_expansion();
690 if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
691 if let Some(def_id) = path.res.opt_def_id();
692 let ty = cx.tcx.type_of(def_id);
693 if let ty::Adt(def, _) = ty.kind();
694 if def.is_struct() || def.is_union();
695 if fields.len() == def.non_enum_variant().fields.len();
700 REST_PAT_IN_FULLY_BOUND_STRUCTS,
702 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
704 "consider removing `..` from this binding",
710 extract_msrv_attr!(LateContext);
713 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
714 // Type of expression is `bool`.
715 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
720 "you seem to be trying to match on a boolean expression",
724 let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
725 if let ExprKind::Lit(ref lit) = arm_bool.kind {
727 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
728 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
738 if let Some((true_expr, false_expr)) = exprs {
739 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
740 (false, false) => Some(format!(
742 snippet(cx, ex.span, "b"),
743 expr_block(cx, true_expr, None, "..", Some(expr.span)),
744 expr_block(cx, false_expr, None, "..", Some(expr.span))
746 (false, true) => Some(format!(
748 snippet(cx, ex.span, "b"),
749 expr_block(cx, true_expr, None, "..", Some(expr.span))
752 let test = Sugg::hir(cx, ex, "..");
756 expr_block(cx, false_expr, None, "..", Some(expr.span))
759 (true, true) => None,
762 if let Some(sugg) = sugg {
763 diag.span_suggestion(
765 "consider using an `if`/`else` expression",
767 Applicability::HasPlaceholders,
777 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
778 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
779 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
780 if !ranges.is_empty() {
781 if let Some((start, end)) = overlapping(&ranges) {
784 MATCH_OVERLAPPING_ARM,
786 "some ranges overlap",
788 "overlaps with this",
795 fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
796 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
797 if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
799 if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
800 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
801 if path_str == "Err" {
802 let mut matching_wild = inner.iter().any(is_wild);
803 let mut ident_bind_name = kw::Underscore;
805 // Looking for unused bindings (i.e.: `_e`)
806 for pat in inner.iter() {
807 if let PatKind::Binding(_, id, ident, None) = pat.kind {
808 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
809 ident_bind_name = ident.name;
810 matching_wild = true;
817 if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
818 if is_panic(cx, macro_call.def_id);
820 // `Err(_)` or `Err(_e)` arm with `panic!` found
821 span_lint_and_note(cx,
824 &format!("`Err({})` matches all errors", ident_bind_name),
826 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
836 enum CommonPrefixSearcher<'a> {
838 Path(&'a [PathSegment<'a>]),
841 impl<'a> CommonPrefixSearcher<'a> {
842 fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
844 [path @ .., _] => self.with_prefix(path),
849 fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
851 Self::None => *self = Self::Path(path),
852 Self::Path(self_path)
855 .map(|p| p.ident.name)
856 .eq(self_path.iter().map(|p| p.ident.name)) => {},
857 Self::Path(_) => *self = Self::Mixed,
863 fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
864 let attrs = cx.tcx.get_attrs(variant_def.def_id);
865 clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
868 #[allow(clippy::too_many_lines)]
869 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
870 let ty = cx.typeck_results().expr_ty(ex).peel_refs();
871 let adt_def = match ty.kind() {
874 && !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
881 // First pass - check for violation, but don't do much book-keeping because this is hopefully
882 // the uncommon case, and the book-keeping is slightly expensive.
883 let mut wildcard_span = None;
884 let mut wildcard_ident = None;
885 let mut has_non_wild = false;
887 match peel_hir_pat_refs(arm.pat).0.kind {
888 PatKind::Wild => wildcard_span = Some(arm.pat.span),
889 PatKind::Binding(_, _, ident, None) => {
890 wildcard_span = Some(arm.pat.span);
891 wildcard_ident = Some(ident);
893 _ => has_non_wild = true,
896 let wildcard_span = match wildcard_span {
897 Some(x) if has_non_wild => x,
901 // Accumulate the variants which should be put in place of the wildcard because they're not
903 let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
904 let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
906 let mut path_prefix = CommonPrefixSearcher::None;
908 // Guards mean that this case probably isn't exhaustively covered. Technically
909 // this is incorrect, as we should really check whether each variant is exhaustively
910 // covered by the set of guards that cover it, but that's really hard to do.
911 recurse_or_patterns(arm.pat, |pat| {
912 let path = match &peel_hir_pat_refs(pat).0.kind {
913 PatKind::Path(path) => {
914 #[allow(clippy::match_same_arms)]
915 let id = match cx.qpath_res(path, pat.hir_id) {
917 DefKind::Const | DefKind::ConstParam | DefKind::AnonConst | DefKind::InlineConst,
920 Res::Def(_, id) => id,
923 if arm.guard.is_none() {
924 missing_variants.retain(|e| e.ctor_def_id != Some(id));
928 PatKind::TupleStruct(path, patterns, ..) => {
929 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
930 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
931 missing_variants.retain(|e| e.ctor_def_id != Some(id));
936 PatKind::Struct(path, patterns, ..) => {
937 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
938 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
939 missing_variants.retain(|e| e.def_id != id);
947 QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
950 kind: TyKind::Path(QPath::Resolved(_, path)),
954 ) => path_prefix.with_prefix(path.segments),
960 let format_suggestion = |variant: &VariantDef| {
963 if let Some(ident) = wildcard_ident {
964 format!("{} @ ", ident.name)
968 if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
969 let mut s = String::new();
970 for seg in path_prefix {
971 s.push_str(seg.ident.as_str());
976 let mut s = cx.tcx.def_path_str(adt_def.did);
981 match variant.ctor_kind {
982 CtorKind::Fn if variant.fields.len() == 1 => "(_)",
983 CtorKind::Fn => "(..)",
984 CtorKind::Const => "",
985 CtorKind::Fictive => "{ .. }",
990 match missing_variants.as_slice() {
992 [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
994 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
996 "wildcard matches only a single variant and will also match any future added variants",
998 format_suggestion(x),
999 Applicability::MaybeIncorrect,
1002 let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
1003 let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
1004 suggestions.push("_".into());
1005 "wildcard matches known variants and will also match future added variants"
1007 "wildcard match will also match any future added variants"
1012 WILDCARD_ENUM_MATCH_ARM,
1016 suggestions.join(" | "),
1017 Applicability::MaybeIncorrect,
1023 fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
1026 I: Clone + Iterator<Item = &'a Pat<'b>>,
1028 if !has_multiple_ref_pats(pats.clone()) {
1032 let (first_sugg, msg, title);
1033 let span = ex.span.source_callsite();
1034 if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
1035 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1037 title = "you don't need to add `&` to both the expression and the patterns";
1039 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1040 msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
1041 title = "you don't need to add `&` to all patterns";
1044 let remaining_suggs = pats.filter_map(|pat| {
1045 if let PatKind::Ref(refp, _) = pat.kind {
1046 Some((pat.span, snippet(cx, refp.span, "..").to_string()))
1052 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1053 if !expr.span.from_expansion() {
1054 multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
1059 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1060 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1061 let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
1062 is_ref_some_arm(cx, &arms[1])
1063 } else if is_none_arm(cx, &arms[1]) {
1064 is_ref_some_arm(cx, &arms[0])
1068 if let Some(rb) = arm_ref {
1069 let suggestion = if rb == BindingAnnotation::Ref {
1075 let output_ty = cx.typeck_results().expr_ty(expr);
1076 let input_ty = cx.typeck_results().expr_ty(ex);
1078 let cast = if_chain! {
1079 if let ty::Adt(_, substs) = input_ty.kind();
1080 let input_ty = substs.type_at(0);
1081 if let ty::Adt(_, substs) = output_ty.kind();
1082 let output_ty = substs.type_at(0);
1083 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1084 if input_ty != output_ty;
1092 let mut applicability = Applicability::MachineApplicable;
1097 &format!("use `{}()` instead", suggestion),
1101 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1111 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1113 if let PatKind::Or(fields) = arm.pat.kind {
1114 // look for multiple fields in this arm that contains at least one Wild pattern
1115 if fields.len() > 1 && fields.iter().any(is_wild) {
1118 WILDCARD_IN_OR_PATTERNS,
1120 "wildcard pattern covers any other pattern as it will match anyway",
1122 "consider handling `_` separately",
1129 #[allow(clippy::too_many_lines)]
1130 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1131 if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1136 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1137 // to prevent false positives as there is currently no better way to detect if code was excluded by
1138 // a macro. See PR #6435
1140 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1141 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1142 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1143 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1144 if rest_snippet.contains("=>");
1146 // The code it self contains another thick arrow "=>"
1147 // -> Either another arm or a comment
1152 let matched_vars = ex.span;
1153 let bind_names = arms[0].pat.span;
1154 let match_body = peel_blocks(arms[0].body);
1155 let mut snippet_body = if match_body.span.from_expansion() {
1156 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1158 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1161 // Do we need to add ';' to suggestion ?
1162 match match_body.kind {
1163 ExprKind::Block(block, _) => {
1164 // macro + expr_ty(body) == ()
1165 if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
1166 snippet_body.push(';');
1170 // expr_ty(body) == ()
1171 if cx.typeck_results().expr_ty(match_body).is_unit() {
1172 snippet_body.push(';');
1177 let mut applicability = Applicability::MaybeIncorrect;
1178 match arms[0].pat.kind {
1179 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1180 // If this match is in a local (`let`) stmt
1181 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1183 parent_let_node.span,
1185 "let {} = {};\n{}let {} = {};",
1186 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1187 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1188 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1189 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1194 // If we are in closure, we need curly braces around suggestion
1195 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1196 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1197 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1198 if let ExprKind::Closure(..) = parent_expr.kind {
1199 cbrace_end = format!("\n{}}}", indent);
1200 // Fix body indent due to the closure
1201 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1202 cbrace_start = format!("{{\n{}", indent);
1205 // If the parent is already an arm, and the body is another match statement,
1206 // we need curly braces around suggestion
1207 let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
1208 if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
1209 if let ExprKind::Match(..) = arm.body.kind {
1210 cbrace_end = format!("\n{}}}", indent);
1211 // Fix body indent due to the match
1212 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1213 cbrace_start = format!("{{\n{}", indent);
1219 "{}let {} = {};\n{}{}{}",
1221 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1222 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1231 MATCH_SINGLE_BINDING,
1233 "this match could be written as a `let` statement",
1234 "consider using `let` statement",
1240 if ex.can_have_side_effects() {
1241 let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
1244 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1250 MATCH_SINGLE_BINDING,
1252 "this match could be replaced by its scrutinee and body",
1253 "consider using the scrutinee and body instead",
1260 MATCH_SINGLE_BINDING,
1262 "this match could be replaced by its body itself",
1263 "consider using the match body instead",
1265 Applicability::MachineApplicable,
1273 /// Returns true if the `ex` match expression is in a local (`let`) statement
1274 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1275 let map = &cx.tcx.hir();
1277 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1278 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1280 return Some(parent_let_expr);
1286 /// Gets the ranges for each range pattern arm. Applies `ty` bounds for open ranges.
1287 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
1290 if let Arm { pat, guard: None, .. } = *arm {
1291 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1292 let lhs_const = match lhs {
1293 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1294 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1296 let rhs_const = match rhs {
1297 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1298 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1301 let lhs_val = lhs_const.int_value(cx, ty)?;
1302 let rhs_val = rhs_const.int_value(cx, ty)?;
1304 let rhs_bound = match range_end {
1305 RangeEnd::Included => EndBound::Included(rhs_val),
1306 RangeEnd::Excluded => EndBound::Excluded(rhs_val),
1308 return Some(SpannedRange {
1310 node: (lhs_val, rhs_bound),
1314 if let PatKind::Lit(value) = pat.kind {
1315 let value = constant_full_int(cx, cx.typeck_results(), value)?;
1316 return Some(SpannedRange {
1318 node: (value, EndBound::Included(value)),
1327 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
1328 pub enum EndBound<T> {
1333 #[derive(Debug, Eq, PartialEq)]
1334 struct SpannedRange<T> {
1336 pub node: (T, EndBound<T>),
1339 // Checks if arm has the form `None => None`
1340 fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
1341 matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
1344 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1345 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
1347 if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
1348 if is_lang_ctor(cx, qpath, OptionSome);
1349 if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
1350 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1351 if let ExprKind::Call(e, args) = peel_blocks(arm.body).kind;
1352 if let ExprKind::Path(ref some_path) = e.kind;
1353 if is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1;
1354 if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
1355 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1363 fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
1366 I: Iterator<Item = &'a Pat<'b>>,
1368 let mut ref_count = 0;
1369 for opt in pats.map(|pat| match pat.kind {
1370 PatKind::Ref(..) => Some(true), // &-patterns
1371 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1372 _ => None, // any other pattern is not fine
1374 if let Some(inner) = opt {
1385 fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1389 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
1396 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1397 struct RangeBound<'a, T>(T, BoundKind, &'a SpannedRange<T>);
1399 impl<'a, T: Copy + Ord> PartialOrd for RangeBound<'a, T> {
1400 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1401 Some(self.cmp(other))
1405 impl<'a, T: Copy + Ord> Ord for RangeBound<'a, T> {
1406 fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
1407 let RangeBound(self_value, self_kind, _) = *self;
1408 (self_value, self_kind).cmp(&(*other_value, *other_kind))
1412 let mut values = Vec::with_capacity(2 * ranges.len());
1414 for r @ SpannedRange { node: (start, end), .. } in ranges {
1415 values.push(RangeBound(*start, BoundKind::Start, r));
1416 values.push(match end {
1417 EndBound::Excluded(val) => RangeBound(*val, BoundKind::EndExcluded, r),
1418 EndBound::Included(val) => RangeBound(*val, BoundKind::EndIncluded, r),
1424 let mut started = vec![];
1426 for RangeBound(_, kind, range) in values {
1428 BoundKind::Start => started.push(range),
1429 BoundKind::EndExcluded | BoundKind::EndIncluded => {
1430 let mut overlap = None;
1432 while let Some(last_started) = started.pop() {
1433 if last_started == range {
1436 overlap = Some(last_started);
1439 if let Some(first_overlapping) = overlap {
1440 return Some((range, first_overlapping));
1450 fn test_overlapping() {
1451 use rustc_span::source_map::DUMMY_SP;
1453 let sp = |s, e| SpannedRange {
1458 assert_eq!(None, overlapping::<u8>(&[]));
1459 assert_eq!(None, overlapping(&[sp(1, EndBound::Included(4))]));
1462 overlapping(&[sp(1, EndBound::Included(4)), sp(5, EndBound::Included(6))])
1467 sp(1, EndBound::Included(4)),
1468 sp(5, EndBound::Included(6)),
1469 sp(10, EndBound::Included(11))
1473 Some((&sp(1, EndBound::Included(4)), &sp(3, EndBound::Included(6)))),
1474 overlapping(&[sp(1, EndBound::Included(4)), sp(3, EndBound::Included(6))])
1477 Some((&sp(5, EndBound::Included(6)), &sp(6, EndBound::Included(11)))),
1479 sp(1, EndBound::Included(4)),
1480 sp(5, EndBound::Included(6)),
1481 sp(6, EndBound::Included(11))