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::paths;
7 use clippy_utils::peel_blocks_with_stmt;
8 use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
9 use clippy_utils::sugg::Sugg;
10 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, peel_mid_ty_refs};
11 use clippy_utils::visitors::is_local_used;
13 get_parent_expr, is_lang_ctor, is_lint_allowed, is_refutable, is_unit_expr, is_wild, meets_msrv, msrvs,
14 path_to_local_id, peel_blocks, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, strip_pat_refs,
17 use if_chain::if_chain;
18 use rustc_ast::ast::LitKind;
19 use rustc_errors::Applicability;
20 use rustc_hir::def::{CtorKind, DefKind, Res};
21 use rustc_hir::LangItem::{OptionNone, OptionSome};
23 self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat,
24 PatKind, PathSegment, QPath, RangeEnd, TyKind,
26 use rustc_lint::{LateContext, LateLintPass};
27 use rustc_middle::ty::{self, Ty, TyS, VariantDef};
28 use rustc_semver::RustcVersion;
29 use rustc_session::{declare_tool_lint, impl_lint_pass};
30 use rustc_span::{sym, symbol::kw, Span};
31 use std::cmp::{max, Ordering};
33 mod match_like_matches;
36 declare_clippy_lint! {
38 /// Checks for matches with a single arm where an `if let`
39 /// will usually suffice.
41 /// ### Why is this bad?
42 /// Just readability – `if let` nests less than a `match`.
46 /// # fn bar(stool: &str) {}
47 /// # let x = Some("abc");
50 /// Some(ref foo) => bar(foo),
55 /// if let Some(ref foo) = x {
59 #[clippy::version = "pre 1.29.0"]
62 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
65 declare_clippy_lint! {
67 /// Checks for matches with two arms where an `if let else` will
70 /// ### Why is this bad?
71 /// Just readability – `if let` nests less than a `match`.
73 /// ### Known problems
74 /// Personal style preferences may differ.
80 /// # fn bar(foo: &usize) {}
81 /// # let other_ref: usize = 1;
82 /// # let x: Option<&usize> = Some(&1);
84 /// Some(ref foo) => bar(foo),
85 /// _ => bar(&other_ref),
89 /// Using `if let` with `else`:
92 /// # fn bar(foo: &usize) {}
93 /// # let other_ref: usize = 1;
94 /// # let x: Option<&usize> = Some(&1);
95 /// if let Some(ref foo) = x {
101 #[clippy::version = "pre 1.29.0"]
102 pub SINGLE_MATCH_ELSE,
104 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
107 declare_clippy_lint! {
109 /// Checks for matches where all arms match a reference,
110 /// suggesting to remove the reference and deref the matched expression
111 /// instead. It also checks for `if let &foo = bar` blocks.
113 /// ### Why is this bad?
114 /// It just makes the code less readable. That reference
115 /// destructuring adds nothing to the code.
121 /// &A(ref y) => foo(y),
128 /// A(ref y) => foo(y),
133 #[clippy::version = "pre 1.29.0"]
136 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
139 declare_clippy_lint! {
141 /// Checks for matches where match expression is a `bool`. It
142 /// suggests to replace the expression with an `if...else` block.
144 /// ### Why is this bad?
145 /// It makes the code less readable.
151 /// let condition: bool = true;
152 /// match condition {
157 /// Use if/else instead:
161 /// let condition: bool = true;
168 #[clippy::version = "pre 1.29.0"]
171 "a `match` on a boolean expression instead of an `if..else` block"
174 declare_clippy_lint! {
176 /// Checks for overlapping match arms.
178 /// ### Why is this bad?
179 /// It is likely to be an error and if not, makes the code
186 /// 1..=10 => println!("1 ... 10"),
187 /// 5..=15 => println!("5 ... 15"),
191 #[clippy::version = "pre 1.29.0"]
192 pub MATCH_OVERLAPPING_ARM,
194 "a `match` with overlapping arms"
197 declare_clippy_lint! {
199 /// Checks for arm which matches all errors with `Err(_)`
200 /// and take drastic actions like `panic!`.
202 /// ### Why is this bad?
203 /// It is generally a bad practice, similar to
204 /// catching all exceptions in java with `catch(Exception)`
208 /// let x: Result<i32, &str> = Ok(3);
210 /// Ok(_) => println!("ok"),
211 /// Err(_) => panic!("err"),
214 #[clippy::version = "pre 1.29.0"]
215 pub MATCH_WILD_ERR_ARM,
217 "a `match` with `Err(_)` arm and take drastic actions"
220 declare_clippy_lint! {
222 /// Checks for match which is used to add a reference to an
225 /// ### Why is this bad?
226 /// Using `as_ref()` or `as_mut()` instead is shorter.
230 /// let x: Option<()> = None;
233 /// let r: Option<&()> = match x {
235 /// Some(ref v) => Some(v),
239 /// let r: Option<&()> = x.as_ref();
241 #[clippy::version = "pre 1.29.0"]
244 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
247 declare_clippy_lint! {
249 /// Checks for wildcard enum matches using `_`.
251 /// ### Why is this bad?
252 /// New enum variants added by library updates can be missed.
254 /// ### Known problems
255 /// Suggested replacements may be incorrect if guards exhaustively cover some
256 /// variants, and also may not use correct path to enum if it's not present in the current scope.
260 /// # enum Foo { A(usize), B(usize) }
261 /// # let x = Foo::B(1);
274 #[clippy::version = "1.34.0"]
275 pub WILDCARD_ENUM_MATCH_ARM,
277 "a wildcard enum match arm using `_`"
280 declare_clippy_lint! {
282 /// Checks for wildcard enum matches for a single variant.
284 /// ### Why is this bad?
285 /// New enum variants added by library updates can be missed.
287 /// ### Known problems
288 /// Suggested replacements may not use correct path to enum
289 /// if it's not present in the current scope.
293 /// # enum Foo { A, B, C }
294 /// # let x = Foo::B;
309 #[clippy::version = "1.45.0"]
310 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
312 "a wildcard enum match for a single variant"
315 declare_clippy_lint! {
317 /// Checks for wildcard pattern used with others patterns in same match arm.
319 /// ### Why is this bad?
320 /// Wildcard pattern already covers any other pattern as it will match anyway.
321 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
337 #[clippy::version = "1.42.0"]
338 pub WILDCARD_IN_OR_PATTERNS,
340 "a wildcard pattern used with others patterns in same match arm"
343 declare_clippy_lint! {
345 /// Checks for matches being used to destructure a single-variant enum
346 /// or tuple struct where a `let` will suffice.
348 /// ### Why is this bad?
349 /// Just readability – `let` doesn't nest, whereas a `match` does.
357 /// let wrapper = Wrapper::Data(42);
359 /// let data = match wrapper {
360 /// Wrapper::Data(i) => i,
364 /// The correct use would be:
370 /// let wrapper = Wrapper::Data(42);
371 /// let Wrapper::Data(data) = wrapper;
373 #[clippy::version = "pre 1.29.0"]
374 pub INFALLIBLE_DESTRUCTURING_MATCH,
376 "a `match` statement with a single infallible arm instead of a `let`"
379 declare_clippy_lint! {
381 /// Checks for useless match that binds to only one value.
383 /// ### Why is this bad?
384 /// Readability and needless complexity.
386 /// ### Known problems
387 /// Suggested replacements may be incorrect when `match`
388 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
403 /// let (c, d) = (a, b);
405 #[clippy::version = "1.43.0"]
406 pub MATCH_SINGLE_BINDING,
408 "a match with a single binding instead of using `let` statement"
411 declare_clippy_lint! {
413 /// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
415 /// ### Why is this bad?
416 /// Correctness and readability. It's like having a wildcard pattern after
417 /// matching all enum variants explicitly.
421 /// # struct A { a: i32 }
422 /// let a = A { a: 5 };
426 /// A { a: 5, .. } => {},
432 /// A { a: 5 } => {},
436 #[clippy::version = "1.43.0"]
437 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
439 "a match on a struct that binds all fields but still uses the wildcard pattern"
442 declare_clippy_lint! {
444 /// Lint for redundant pattern matching over `Result`, `Option`,
445 /// `std::task::Poll` or `std::net::IpAddr`
447 /// ### Why is this bad?
448 /// It's more concise and clear to just use the proper
451 /// ### Known problems
452 /// This will change the drop order for the matched type. Both `if let` and
453 /// `while let` will drop the value at the end of the block, both `if` and `while` will drop the
454 /// value before entering the block. For most types this change will not matter, but for a few
455 /// types this will not be an acceptable change (e.g. locks). See the
456 /// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about
461 /// # use std::task::Poll;
462 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
463 /// if let Ok(_) = Ok::<i32, i32>(42) {}
464 /// if let Err(_) = Err::<i32, i32>(42) {}
465 /// if let None = None::<()> {}
466 /// if let Some(_) = Some(42) {}
467 /// if let Poll::Pending = Poll::Pending::<()> {}
468 /// if let Poll::Ready(_) = Poll::Ready(42) {}
469 /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
470 /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
471 /// match Ok::<i32, i32>(42) {
477 /// The more idiomatic use would be:
480 /// # use std::task::Poll;
481 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
482 /// if Ok::<i32, i32>(42).is_ok() {}
483 /// if Err::<i32, i32>(42).is_err() {}
484 /// if None::<()>.is_none() {}
485 /// if Some(42).is_some() {}
486 /// if Poll::Pending::<()>.is_pending() {}
487 /// if Poll::Ready(42).is_ready() {}
488 /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
489 /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
490 /// Ok::<i32, i32>(42).is_ok();
492 #[clippy::version = "1.31.0"]
493 pub REDUNDANT_PATTERN_MATCHING,
495 "use the proper utility function avoiding an `if let`"
498 declare_clippy_lint! {
500 /// Checks for `match` or `if let` expressions producing a
501 /// `bool` that could be written using `matches!`
503 /// ### Why is this bad?
504 /// Readability and needless complexity.
506 /// ### Known problems
507 /// This lint falsely triggers, if there are arms with
508 /// `cfg` attributes that remove an arm evaluating to `false`.
515 /// let a = match x {
520 /// let a = if let Some(0) = x {
527 /// let a = matches!(x, Some(0));
529 #[clippy::version = "1.47.0"]
530 pub MATCH_LIKE_MATCHES_MACRO,
532 "a match that could be written with the matches! macro"
535 declare_clippy_lint! {
537 /// Checks for `match` with identical arm bodies.
539 /// ### Why is this bad?
540 /// This is probably a copy & paste error. If arm bodies
541 /// are the same on purpose, you can factor them
542 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
544 /// ### Known problems
545 /// False positive possible with order dependent `match`
547 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
554 /// Baz => bar(), // <= oops
558 /// This should probably be
563 /// Baz => baz(), // <= fixed
567 /// or if the original code was not a typo:
570 /// Bar | Baz => bar(), // <= shows the intent better
574 #[clippy::version = "pre 1.29.0"]
577 "`match` with identical arm bodies"
582 msrv: Option<RustcVersion>,
583 infallible_destructuring_match_linted: bool,
588 pub fn new(msrv: Option<RustcVersion>) -> Self {
596 impl_lint_pass!(Matches => [
601 MATCH_OVERLAPPING_ARM,
604 WILDCARD_ENUM_MATCH_ARM,
605 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
606 WILDCARD_IN_OR_PATTERNS,
607 MATCH_SINGLE_BINDING,
608 INFALLIBLE_DESTRUCTURING_MATCH,
609 REST_PAT_IN_FULLY_BOUND_STRUCTS,
610 REDUNDANT_PATTERN_MATCHING,
611 MATCH_LIKE_MATCHES_MACRO,
615 impl<'tcx> LateLintPass<'tcx> for Matches {
616 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
617 if expr.span.from_expansion() {
621 redundant_pattern_match::check(cx, expr);
623 if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) {
624 if !match_like_matches::check(cx, expr) {
625 match_same_arms::check(cx, expr);
628 match_same_arms::check(cx, expr);
631 if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
632 check_single_match(cx, ex, arms, expr);
633 check_match_bool(cx, ex, arms, expr);
634 check_overlapping_arms(cx, ex, arms);
635 check_wild_err_arm(cx, ex, arms);
636 check_wild_enum_match(cx, ex, arms);
637 check_match_as_ref(cx, ex, arms, expr);
638 check_wild_in_or_pats(cx, arms);
640 if self.infallible_destructuring_match_linted {
641 self.infallible_destructuring_match_linted = false;
643 check_match_single_binding(cx, ex, arms, expr);
646 if let ExprKind::Match(ex, arms, _) = expr.kind {
647 check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr);
651 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
653 if !local.span.from_expansion();
654 if let Some(expr) = local.init;
655 if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
656 if arms.len() == 1 && arms[0].guard.is_none();
657 if let PatKind::TupleStruct(
658 QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
660 if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
661 let body = peel_blocks(arms[0].body);
662 if path_to_local_id(body, arg);
665 let mut applicability = Applicability::MachineApplicable;
666 self.infallible_destructuring_match_linted = true;
669 INFALLIBLE_DESTRUCTURING_MATCH,
671 "you seem to be trying to use `match` to destructure a single infallible pattern. \
672 Consider using `let`",
676 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
677 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
678 snippet_with_applicability(cx, target.span, "..", &mut applicability),
686 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
688 if !pat.span.from_expansion();
689 if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
690 if let Some(def_id) = path.res.opt_def_id();
691 let ty = cx.tcx.type_of(def_id);
692 if let ty::Adt(def, _) = ty.kind();
693 if def.is_struct() || def.is_union();
694 if fields.len() == def.non_enum_variant().fields.len();
699 REST_PAT_IN_FULLY_BOUND_STRUCTS,
701 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
703 "consider removing `..` from this binding",
709 extract_msrv_attr!(LateContext);
713 fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
714 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
715 if expr.span.from_expansion() {
716 // Don't lint match expressions present in
717 // macro_rules! block
720 if let PatKind::Or(..) = arms[0].pat.kind {
721 // don't lint for or patterns for now, this makes
722 // the lint noisy in unnecessary situations
725 let els = arms[1].body;
726 let els = if is_unit_expr(peel_blocks(els)) {
728 } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
729 if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
730 // single statement/expr "else" block, don't lint
733 // block with 2+ statements or 1 expr and 1+ statement
736 // not a block, don't lint
740 let ty = cx.typeck_results().expr_ty(ex);
741 if *ty.kind() != ty::Bool || is_lint_allowed(cx, MATCH_BOOL, ex.hir_id) {
742 check_single_match_single_pattern(cx, ex, arms, expr, els);
743 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
748 fn check_single_match_single_pattern(
749 cx: &LateContext<'_>,
753 els: Option<&Expr<'_>>,
755 if is_wild(arms[1].pat) {
756 report_single_match_single_pattern(cx, ex, arms, expr, els);
760 fn report_single_match_single_pattern(
761 cx: &LateContext<'_>,
765 els: Option<&Expr<'_>>,
767 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
768 let els_str = els.map_or(String::new(), |els| {
769 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
772 let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat);
773 let (msg, sugg) = if_chain! {
774 if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind;
775 let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex));
776 if let Some(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait();
777 if let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait();
778 if ty.is_integral() || ty.is_char() || ty.is_str()
779 || (implements_trait(cx, ty, spe_trait_id, &[])
780 && implements_trait(cx, ty, pe_trait_id, &[ty.into()]));
782 // scrutinee derives PartialEq and the pattern is a constant.
783 let pat_ref_count = match pat.kind {
784 // string literals are already a reference.
785 PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1,
788 // References are only implicitly added to the pattern, so no overflow here.
789 // e.g. will work: match &Some(_) { Some(_) => () }
790 // will not: match Some(_) { &Some(_) => () }
791 let ref_count_diff = ty_ref_count - pat_ref_count;
793 // Try to remove address of expressions first.
794 let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff);
795 let ref_count_diff = ref_count_diff - removed;
797 let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`";
799 "if {} == {}{} {}{}",
800 snippet(cx, ex.span, ".."),
801 // PartialEq for different reference counts may not exist.
802 "&".repeat(ref_count_diff),
803 snippet(cx, arms[0].pat.span, ".."),
804 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
809 let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`";
811 "if let {} = {} {}{}",
812 snippet(cx, arms[0].pat.span, ".."),
813 snippet(cx, ex.span, ".."),
814 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
828 Applicability::HasPlaceholders,
832 fn check_single_match_opt_like<'a>(
833 cx: &LateContext<'a>,
838 els: Option<&Expr<'_>>,
840 // list of candidate `Enum`s we know will never get any more members
842 (&paths::COW, "Borrowed"),
843 (&paths::COW, "Cow::Borrowed"),
844 (&paths::COW, "Cow::Owned"),
845 (&paths::COW, "Owned"),
846 (&paths::OPTION, "None"),
847 (&paths::RESULT, "Err"),
848 (&paths::RESULT, "Ok"),
851 // We want to suggest to exclude an arm that contains only wildcards or forms the exhaustive
852 // match with the second branch, without enum variants in matches.
853 if !contains_only_wilds(arms[1].pat) && !form_exhaustive_matches(arms[0].pat, arms[1].pat) {
857 let mut paths_and_types = Vec::new();
858 if !collect_pat_paths(&mut paths_and_types, cx, arms[1].pat, ty) {
862 let in_candidate_enum = |path_info: &(String, &TyS<'_>)| -> bool {
863 let (path, ty) = path_info;
864 for &(ty_path, pat_path) in candidates {
865 if path == pat_path && match_type(cx, ty, ty_path) {
871 if paths_and_types.iter().all(in_candidate_enum) {
872 report_single_match_single_pattern(cx, ex, arms, expr, els);
876 /// Collects paths and their types from the given patterns. Returns true if the given pattern could
877 /// be simplified, false otherwise.
878 fn collect_pat_paths<'a>(acc: &mut Vec<(String, Ty<'a>)>, cx: &LateContext<'a>, pat: &Pat<'_>, ty: Ty<'a>) -> bool {
880 PatKind::Wild => true,
881 PatKind::Tuple(inner, _) => inner.iter().all(|p| {
882 let p_ty = cx.typeck_results().pat_ty(p);
883 collect_pat_paths(acc, cx, p, p_ty)
885 PatKind::TupleStruct(ref path, ..) => {
886 let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
887 s.print_qpath(path, false);
889 acc.push((path, ty));
892 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => {
893 acc.push((ident.to_string(), ty));
896 PatKind::Path(ref path) => {
897 let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
898 s.print_qpath(path, false);
900 acc.push((path, ty));
907 /// Returns true if the given arm of pattern matching contains wildcard patterns.
908 fn contains_only_wilds(pat: &Pat<'_>) -> bool {
910 PatKind::Wild => true,
911 PatKind::Tuple(inner, _) | PatKind::TupleStruct(_, inner, ..) => inner.iter().all(contains_only_wilds),
916 /// Returns true if the given patterns forms only exhaustive matches that don't contain enum
917 /// patterns without a wildcard.
918 fn form_exhaustive_matches(left: &Pat<'_>, right: &Pat<'_>) -> bool {
919 match (&left.kind, &right.kind) {
920 (PatKind::Wild, _) | (_, PatKind::Wild) => true,
921 (PatKind::Tuple(left_in, left_pos), PatKind::Tuple(right_in, right_pos)) => {
922 // We don't actually know the position and the presence of the `..` (dotdot) operator
923 // in the arms, so we need to evaluate the correct offsets here in order to iterate in
924 // both arms at the same time.
927 if left_pos.is_some() { 1 } else { 0 }
930 if right_pos.is_some() { 1 } else { 0 }
933 let mut left_pos = left_pos.unwrap_or(usize::MAX);
934 let mut right_pos = right_pos.unwrap_or(usize::MAX);
935 let mut left_dot_space = 0;
936 let mut right_dot_space = 0;
938 let mut found_dotdot = false;
941 if left_dot_space < len - left_in.len() {
947 right_dot_space += 1;
948 if right_dot_space < len - right_in.len() {
956 if !contains_only_wilds(&left_in[i - left_dot_space])
957 && !contains_only_wilds(&right_in[i - right_dot_space])
968 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
969 // Type of expression is `bool`.
970 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
975 "you seem to be trying to match on a boolean expression",
979 let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
980 if let ExprKind::Lit(ref lit) = arm_bool.kind {
982 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
983 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
993 if let Some((true_expr, false_expr)) = exprs {
994 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
995 (false, false) => Some(format!(
997 snippet(cx, ex.span, "b"),
998 expr_block(cx, true_expr, None, "..", Some(expr.span)),
999 expr_block(cx, false_expr, None, "..", Some(expr.span))
1001 (false, true) => Some(format!(
1003 snippet(cx, ex.span, "b"),
1004 expr_block(cx, true_expr, None, "..", Some(expr.span))
1007 let test = Sugg::hir(cx, ex, "..");
1011 expr_block(cx, false_expr, None, "..", Some(expr.span))
1014 (true, true) => None,
1017 if let Some(sugg) = sugg {
1018 diag.span_suggestion(
1020 "consider using an `if`/`else` expression",
1022 Applicability::HasPlaceholders,
1032 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
1033 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
1034 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
1035 if !ranges.is_empty() {
1036 if let Some((start, end)) = overlapping(&ranges) {
1039 MATCH_OVERLAPPING_ARM,
1041 "some ranges overlap",
1043 "overlaps with this",
1050 fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
1051 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
1052 if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
1054 if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
1055 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
1056 if path_str == "Err" {
1057 let mut matching_wild = inner.iter().any(is_wild);
1058 let mut ident_bind_name = kw::Underscore;
1060 // Looking for unused bindings (i.e.: `_e`)
1061 for pat in inner.iter() {
1062 if let PatKind::Binding(_, id, ident, None) = pat.kind {
1063 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
1064 ident_bind_name = ident.name;
1065 matching_wild = true;
1072 if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
1073 if is_panic(cx, macro_call.def_id);
1075 // `Err(_)` or `Err(_e)` arm with `panic!` found
1076 span_lint_and_note(cx,
1079 &format!("`Err({})` matches all errors", ident_bind_name),
1081 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
1091 enum CommonPrefixSearcher<'a> {
1093 Path(&'a [PathSegment<'a>]),
1096 impl<'a> CommonPrefixSearcher<'a> {
1097 fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
1099 [path @ .., _] => self.with_prefix(path),
1104 fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
1106 Self::None => *self = Self::Path(path),
1107 Self::Path(self_path)
1110 .map(|p| p.ident.name)
1111 .eq(self_path.iter().map(|p| p.ident.name)) => {},
1112 Self::Path(_) => *self = Self::Mixed,
1118 fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
1119 let attrs = cx.tcx.get_attrs(variant_def.def_id);
1120 clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
1123 #[allow(clippy::too_many_lines)]
1124 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
1125 let ty = cx.typeck_results().expr_ty(ex).peel_refs();
1126 let adt_def = match ty.kind() {
1128 if adt_def.is_enum()
1129 && !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
1136 // First pass - check for violation, but don't do much book-keeping because this is hopefully
1137 // the uncommon case, and the book-keeping is slightly expensive.
1138 let mut wildcard_span = None;
1139 let mut wildcard_ident = None;
1140 let mut has_non_wild = false;
1142 match peel_hir_pat_refs(arm.pat).0.kind {
1143 PatKind::Wild => wildcard_span = Some(arm.pat.span),
1144 PatKind::Binding(_, _, ident, None) => {
1145 wildcard_span = Some(arm.pat.span);
1146 wildcard_ident = Some(ident);
1148 _ => has_non_wild = true,
1151 let wildcard_span = match wildcard_span {
1152 Some(x) if has_non_wild => x,
1156 // Accumulate the variants which should be put in place of the wildcard because they're not
1158 let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
1159 let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
1161 let mut path_prefix = CommonPrefixSearcher::None;
1163 // Guards mean that this case probably isn't exhaustively covered. Technically
1164 // this is incorrect, as we should really check whether each variant is exhaustively
1165 // covered by the set of guards that cover it, but that's really hard to do.
1166 recurse_or_patterns(arm.pat, |pat| {
1167 let path = match &peel_hir_pat_refs(pat).0.kind {
1168 PatKind::Path(path) => {
1169 #[allow(clippy::match_same_arms)]
1170 let id = match cx.qpath_res(path, pat.hir_id) {
1172 DefKind::Const | DefKind::ConstParam | DefKind::AnonConst | DefKind::InlineConst,
1175 Res::Def(_, id) => id,
1178 if arm.guard.is_none() {
1179 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1183 PatKind::TupleStruct(path, patterns, ..) => {
1184 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1185 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
1186 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1191 PatKind::Struct(path, patterns, ..) => {
1192 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1193 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
1194 missing_variants.retain(|e| e.def_id != id);
1202 QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
1203 QPath::TypeRelative(
1205 kind: TyKind::Path(QPath::Resolved(_, path)),
1209 ) => path_prefix.with_prefix(path.segments),
1215 let format_suggestion = |variant: &VariantDef| {
1218 if let Some(ident) = wildcard_ident {
1219 format!("{} @ ", ident.name)
1223 if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
1224 let mut s = String::new();
1225 for seg in path_prefix {
1226 s.push_str(seg.ident.as_str());
1231 let mut s = cx.tcx.def_path_str(adt_def.did);
1236 match variant.ctor_kind {
1237 CtorKind::Fn if variant.fields.len() == 1 => "(_)",
1238 CtorKind::Fn => "(..)",
1239 CtorKind::Const => "",
1240 CtorKind::Fictive => "{ .. }",
1245 match missing_variants.as_slice() {
1247 [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
1249 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1251 "wildcard matches only a single variant and will also match any future added variants",
1253 format_suggestion(x),
1254 Applicability::MaybeIncorrect,
1257 let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
1258 let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
1259 suggestions.push("_".into());
1260 "wildcard matches known variants and will also match future added variants"
1262 "wildcard match will also match any future added variants"
1267 WILDCARD_ENUM_MATCH_ARM,
1271 suggestions.join(" | "),
1272 Applicability::MaybeIncorrect,
1278 fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
1281 I: Clone + Iterator<Item = &'a Pat<'b>>,
1283 if !has_multiple_ref_pats(pats.clone()) {
1287 let (first_sugg, msg, title);
1288 let span = ex.span.source_callsite();
1289 if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
1290 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1292 title = "you don't need to add `&` to both the expression and the patterns";
1294 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1295 msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
1296 title = "you don't need to add `&` to all patterns";
1299 let remaining_suggs = pats.filter_map(|pat| {
1300 if let PatKind::Ref(refp, _) = pat.kind {
1301 Some((pat.span, snippet(cx, refp.span, "..").to_string()))
1307 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1308 if !expr.span.from_expansion() {
1309 multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
1314 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1315 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1316 let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
1317 is_ref_some_arm(cx, &arms[1])
1318 } else if is_none_arm(cx, &arms[1]) {
1319 is_ref_some_arm(cx, &arms[0])
1323 if let Some(rb) = arm_ref {
1324 let suggestion = if rb == BindingAnnotation::Ref {
1330 let output_ty = cx.typeck_results().expr_ty(expr);
1331 let input_ty = cx.typeck_results().expr_ty(ex);
1333 let cast = if_chain! {
1334 if let ty::Adt(_, substs) = input_ty.kind();
1335 let input_ty = substs.type_at(0);
1336 if let ty::Adt(_, substs) = output_ty.kind();
1337 let output_ty = substs.type_at(0);
1338 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1339 if input_ty != output_ty;
1347 let mut applicability = Applicability::MachineApplicable;
1352 &format!("use `{}()` instead", suggestion),
1356 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1366 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1368 if let PatKind::Or(fields) = arm.pat.kind {
1369 // look for multiple fields in this arm that contains at least one Wild pattern
1370 if fields.len() > 1 && fields.iter().any(is_wild) {
1373 WILDCARD_IN_OR_PATTERNS,
1375 "wildcard pattern covers any other pattern as it will match anyway",
1377 "consider handling `_` separately",
1384 #[allow(clippy::too_many_lines)]
1385 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1386 if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1391 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1392 // to prevent false positives as there is currently no better way to detect if code was excluded by
1393 // a macro. See PR #6435
1395 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1396 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1397 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1398 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1399 if rest_snippet.contains("=>");
1401 // The code it self contains another thick arrow "=>"
1402 // -> Either another arm or a comment
1407 let matched_vars = ex.span;
1408 let bind_names = arms[0].pat.span;
1409 let match_body = peel_blocks(arms[0].body);
1410 let mut snippet_body = if match_body.span.from_expansion() {
1411 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1413 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1416 // Do we need to add ';' to suggestion ?
1417 match match_body.kind {
1418 ExprKind::Block(block, _) => {
1419 // macro + expr_ty(body) == ()
1420 if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
1421 snippet_body.push(';');
1425 // expr_ty(body) == ()
1426 if cx.typeck_results().expr_ty(match_body).is_unit() {
1427 snippet_body.push(';');
1432 let mut applicability = Applicability::MaybeIncorrect;
1433 match arms[0].pat.kind {
1434 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1435 // If this match is in a local (`let`) stmt
1436 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1438 parent_let_node.span,
1440 "let {} = {};\n{}let {} = {};",
1441 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1442 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1443 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1444 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1449 // If we are in closure, we need curly braces around suggestion
1450 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1451 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1452 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1453 if let ExprKind::Closure(..) = parent_expr.kind {
1454 cbrace_end = format!("\n{}}}", indent);
1455 // Fix body indent due to the closure
1456 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1457 cbrace_start = format!("{{\n{}", indent);
1460 // If the parent is already an arm, and the body is another match statement,
1461 // we need curly braces around suggestion
1462 let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
1463 if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
1464 if let ExprKind::Match(..) = arm.body.kind {
1465 cbrace_end = format!("\n{}}}", indent);
1466 // Fix body indent due to the match
1467 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1468 cbrace_start = format!("{{\n{}", indent);
1474 "{}let {} = {};\n{}{}{}",
1476 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1477 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1486 MATCH_SINGLE_BINDING,
1488 "this match could be written as a `let` statement",
1489 "consider using `let` statement",
1495 if ex.can_have_side_effects() {
1496 let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
1499 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1505 MATCH_SINGLE_BINDING,
1507 "this match could be replaced by its scrutinee and body",
1508 "consider using the scrutinee and body instead",
1515 MATCH_SINGLE_BINDING,
1517 "this match could be replaced by its body itself",
1518 "consider using the match body instead",
1520 Applicability::MachineApplicable,
1528 /// Returns true if the `ex` match expression is in a local (`let`) statement
1529 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1530 let map = &cx.tcx.hir();
1532 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1533 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1535 return Some(parent_let_expr);
1541 /// Gets the ranges for each range pattern arm. Applies `ty` bounds for open ranges.
1542 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
1545 if let Arm { pat, guard: None, .. } = *arm {
1546 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1547 let lhs_const = match lhs {
1548 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1549 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1551 let rhs_const = match rhs {
1552 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1553 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1556 let lhs_val = lhs_const.int_value(cx, ty)?;
1557 let rhs_val = rhs_const.int_value(cx, ty)?;
1559 let rhs_bound = match range_end {
1560 RangeEnd::Included => EndBound::Included(rhs_val),
1561 RangeEnd::Excluded => EndBound::Excluded(rhs_val),
1563 return Some(SpannedRange {
1565 node: (lhs_val, rhs_bound),
1569 if let PatKind::Lit(value) = pat.kind {
1570 let value = constant_full_int(cx, cx.typeck_results(), value)?;
1571 return Some(SpannedRange {
1573 node: (value, EndBound::Included(value)),
1582 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
1583 pub enum EndBound<T> {
1588 #[derive(Debug, Eq, PartialEq)]
1589 struct SpannedRange<T> {
1591 pub node: (T, EndBound<T>),
1594 // Checks if arm has the form `None => None`
1595 fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
1596 matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
1599 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1600 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
1602 if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
1603 if is_lang_ctor(cx, qpath, OptionSome);
1604 if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
1605 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1606 if let ExprKind::Call(e, args) = peel_blocks(arm.body).kind;
1607 if let ExprKind::Path(ref some_path) = e.kind;
1608 if is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1;
1609 if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
1610 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1618 fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
1621 I: Iterator<Item = &'a Pat<'b>>,
1623 let mut ref_count = 0;
1624 for opt in pats.map(|pat| match pat.kind {
1625 PatKind::Ref(..) => Some(true), // &-patterns
1626 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1627 _ => None, // any other pattern is not fine
1629 if let Some(inner) = opt {
1640 fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1644 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
1651 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1652 struct RangeBound<'a, T>(T, BoundKind, &'a SpannedRange<T>);
1654 impl<'a, T: Copy + Ord> PartialOrd for RangeBound<'a, T> {
1655 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1656 Some(self.cmp(other))
1660 impl<'a, T: Copy + Ord> Ord for RangeBound<'a, T> {
1661 fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
1662 let RangeBound(self_value, self_kind, _) = *self;
1663 (self_value, self_kind).cmp(&(*other_value, *other_kind))
1667 let mut values = Vec::with_capacity(2 * ranges.len());
1669 for r @ SpannedRange { node: (start, end), .. } in ranges {
1670 values.push(RangeBound(*start, BoundKind::Start, r));
1671 values.push(match end {
1672 EndBound::Excluded(val) => RangeBound(*val, BoundKind::EndExcluded, r),
1673 EndBound::Included(val) => RangeBound(*val, BoundKind::EndIncluded, r),
1679 let mut started = vec![];
1681 for RangeBound(_, kind, range) in values {
1683 BoundKind::Start => started.push(range),
1684 BoundKind::EndExcluded | BoundKind::EndIncluded => {
1685 let mut overlap = None;
1687 while let Some(last_started) = started.pop() {
1688 if last_started == range {
1691 overlap = Some(last_started);
1694 if let Some(first_overlapping) = overlap {
1695 return Some((range, first_overlapping));
1704 mod redundant_pattern_match {
1705 use super::REDUNDANT_PATTERN_MATCHING;
1706 use clippy_utils::diagnostics::span_lint_and_then;
1707 use clippy_utils::source::snippet;
1708 use clippy_utils::sugg::Sugg;
1709 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
1710 use clippy_utils::{higher, match_def_path};
1711 use clippy_utils::{is_lang_ctor, is_trait_method, paths};
1712 use if_chain::if_chain;
1713 use rustc_ast::ast::LitKind;
1714 use rustc_data_structures::fx::FxHashSet;
1715 use rustc_errors::Applicability;
1716 use rustc_hir::LangItem::{OptionNone, PollPending};
1718 intravisit::{walk_expr, Visitor},
1719 Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
1721 use rustc_lint::LateContext;
1722 use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
1723 use rustc_span::sym;
1725 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1726 if let Some(higher::IfLet {
1731 }) = higher::IfLet::hir(cx, expr)
1733 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
1735 if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
1736 find_sugg_for_match(cx, expr, op, arms);
1738 if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
1739 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
1743 /// Checks if the drop order for a type matters. Some std types implement drop solely to
1744 /// deallocate memory. For these types, and composites containing them, changing the drop order
1745 /// won't result in any observable side effects.
1746 fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
1747 type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
1750 fn type_needs_ordered_drop_inner<'tcx>(
1751 cx: &LateContext<'tcx>,
1753 seen: &mut FxHashSet<Ty<'tcx>>,
1755 if !seen.insert(ty) {
1758 if !ty.needs_drop(cx.tcx, cx.param_env) {
1764 .map_or(false, |id| implements_trait(cx, ty, id, &[]))
1766 // This type doesn't implement drop, so no side effects here.
1767 // Check if any component type has any.
1769 ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1770 ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
1771 ty::Adt(adt, subs) => adt
1773 .map(|f| f.ty(cx.tcx, subs))
1774 .any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1778 // Check for std types which implement drop, but only for memory allocation.
1779 else if is_type_diagnostic_item(cx, ty, sym::Vec)
1780 || is_type_lang_item(cx, ty, LangItem::OwnedBox)
1781 || is_type_diagnostic_item(cx, ty, sym::Rc)
1782 || is_type_diagnostic_item(cx, ty, sym::Arc)
1783 || is_type_diagnostic_item(cx, ty, sym::cstring_type)
1784 || is_type_diagnostic_item(cx, ty, sym::BTreeMap)
1785 || is_type_diagnostic_item(cx, ty, sym::LinkedList)
1786 || match_type(cx, ty, &paths::WEAK_RC)
1787 || match_type(cx, ty, &paths::WEAK_ARC)
1789 // Check all of the generic arguments.
1790 if let ty::Adt(_, subs) = ty.kind() {
1791 subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
1800 // Extract the generic arguments out of a type
1801 fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
1803 if let ty::Adt(_, subs) = ty.kind();
1804 if let Some(sub) = subs.get(index);
1805 if let GenericArgKind::Type(sub_ty) = sub.unpack();
1814 // Checks if there are any temporaries created in the given expression for which drop order
1816 fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1817 struct V<'a, 'tcx> {
1818 cx: &'a LateContext<'tcx>,
1821 impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
1822 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
1824 // Taking the reference of a value leaves a temporary
1825 // e.g. In `&String::new()` the string is a temporary value.
1826 // Remaining fields are temporary values
1827 // e.g. In `(String::new(), 0).1` the string is a temporary value.
1828 ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
1829 if !matches!(expr.kind, ExprKind::Path(_)) {
1830 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
1833 self.visit_expr(expr);
1837 // the base type is alway taken by reference.
1838 // e.g. In `(vec![0])[0]` the vector is a temporary value.
1839 ExprKind::Index(base, index) => {
1840 if !matches!(base.kind, ExprKind::Path(_)) {
1841 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
1844 self.visit_expr(base);
1847 self.visit_expr(index);
1849 // Method calls can take self by reference.
1850 // e.g. In `String::new().len()` the string is a temporary value.
1851 ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
1852 if !matches!(self_arg.kind, ExprKind::Path(_)) {
1853 let self_by_ref = self
1856 .type_dependent_def_id(expr.hir_id)
1857 .map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
1859 && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg))
1863 self.visit_expr(self_arg);
1866 args.iter().for_each(|arg| self.visit_expr(arg));
1868 // Either explicitly drops values, or changes control flow.
1869 ExprKind::DropTemps(_)
1871 | ExprKind::Break(..)
1872 | ExprKind::Yield(..)
1873 | ExprKind::Block(Block { expr: None, .. }, _)
1874 | ExprKind::Loop(..) => (),
1876 // Only consider the final expression.
1877 ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
1879 _ => walk_expr(self, expr),
1884 let mut v = V { cx, res: false };
1889 fn find_sugg_for_if_let<'tcx>(
1890 cx: &LateContext<'tcx>,
1891 expr: &'tcx Expr<'_>,
1893 let_expr: &'tcx Expr<'_>,
1894 keyword: &'static str,
1897 // also look inside refs
1898 // if we have &None for example, peel it so we can detect "if let None = x"
1899 let check_pat = match let_pat.kind {
1900 PatKind::Ref(inner, _mutability) => inner,
1903 let op_ty = cx.typeck_results().expr_ty(let_expr);
1904 // Determine which function should be used, and the type contained by the corresponding
1906 let (good_method, inner_ty) = match check_pat.kind {
1907 PatKind::TupleStruct(ref qpath, [sub_pat], _) => {
1908 if let PatKind::Wild = sub_pat.kind {
1909 let res = cx.typeck_results().qpath_res(qpath, check_pat.hir_id);
1910 let Some(id) = res.opt_def_id().and_then(|ctor_id| cx.tcx.parent(ctor_id)) else { return };
1911 let lang_items = cx.tcx.lang_items();
1912 if Some(id) == lang_items.result_ok_variant() {
1913 ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
1914 } else if Some(id) == lang_items.result_err_variant() {
1915 ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
1916 } else if Some(id) == lang_items.option_some_variant() {
1917 ("is_some()", op_ty)
1918 } else if Some(id) == lang_items.poll_ready_variant() {
1919 ("is_ready()", op_ty)
1920 } else if match_def_path(cx, id, &paths::IPADDR_V4) {
1921 ("is_ipv4()", op_ty)
1922 } else if match_def_path(cx, id, &paths::IPADDR_V6) {
1923 ("is_ipv6()", op_ty)
1931 PatKind::Path(ref path) => {
1932 let method = if is_lang_ctor(cx, path, OptionNone) {
1934 } else if is_lang_ctor(cx, path, PollPending) {
1939 // `None` and `Pending` don't have an inner type.
1940 (method, cx.tcx.types.unit)
1945 // If this is the last expression in a block or there is an else clause then the whole
1946 // type needs to be considered, not just the inner type of the branch being matched on.
1947 // Note the last expression in a block is dropped after all local bindings.
1948 let check_ty = if has_else
1949 || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
1956 // All temporaries created in the scrutinee expression are dropped at the same time as the
1957 // scrutinee would be, so they have to be considered as well.
1958 // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
1959 // for the duration if body.
1960 let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
1962 // check that `while_let_on_iterator` lint does not trigger
1964 if keyword == "while";
1965 if let ExprKind::MethodCall(method_path, _, _) = let_expr.kind;
1966 if method_path.ident.name == sym::next;
1967 if is_trait_method(cx, let_expr, sym::Iterator);
1973 let result_expr = match &let_expr.kind {
1974 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1975 ExprKind::Unary(UnOp::Deref, deref) => deref,
1981 REDUNDANT_PATTERN_MATCHING,
1983 &format!("redundant pattern matching, consider using `{}`", good_method),
1985 // if/while let ... = ... { ... }
1986 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1987 let expr_span = expr.span;
1989 // if/while let ... = ... { ... }
1991 let op_span = result_expr.span.source_callsite();
1993 // if/while let ... = ... { ... }
1994 // ^^^^^^^^^^^^^^^^^^^
1995 let span = expr_span.until(op_span.shrink_to_hi());
1997 let app = if needs_drop {
1998 Applicability::MaybeIncorrect
2000 Applicability::MachineApplicable
2003 let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
2007 diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
2010 diag.note("this will change drop order of the result, as well as all temporaries");
2011 diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
2017 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
2018 if arms.len() == 2 {
2019 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
2021 let found_good_method = match node_pair {
2023 PatKind::TupleStruct(ref path_left, patterns_left, _),
2024 PatKind::TupleStruct(ref path_right, patterns_right, _),
2025 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
2026 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
2027 find_good_method_for_match(
2038 find_good_method_for_match(
2053 (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
2054 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
2055 if patterns.len() == 1 =>
2057 if let PatKind::Wild = patterns[0].kind {
2058 find_good_method_for_match(
2063 &paths::OPTION_SOME,
2064 &paths::OPTION_NONE,
2069 find_good_method_for_match(
2075 &paths::POLL_PENDING,
2087 if let Some(good_method) = found_good_method {
2088 let span = expr.span.to(op.span);
2089 let result_expr = match &op.kind {
2090 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2095 REDUNDANT_PATTERN_MATCHING,
2097 &format!("redundant pattern matching, consider using `{}`", good_method),
2099 diag.span_suggestion(
2102 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
2103 Applicability::MaybeIncorrect, // snippet
2111 #[allow(clippy::too_many_arguments)]
2112 fn find_good_method_for_match<'a>(
2113 cx: &LateContext<'_>,
2115 path_left: &QPath<'_>,
2116 path_right: &QPath<'_>,
2117 expected_left: &[&str],
2118 expected_right: &[&str],
2119 should_be_left: &'a str,
2120 should_be_right: &'a str,
2121 ) -> Option<&'a str> {
2124 .qpath_res(path_left, arms[0].pat.hir_id)
2128 .qpath_res(path_right, arms[1].pat.hir_id)
2130 let body_node_pair =
2131 if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) {
2132 (&(*arms[0].body).kind, &(*arms[1].body).kind)
2133 } else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) {
2134 (&(*arms[1].body).kind, &(*arms[0].body).kind)
2139 match body_node_pair {
2140 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
2141 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
2142 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
2151 fn test_overlapping() {
2152 use rustc_span::source_map::DUMMY_SP;
2154 let sp = |s, e| SpannedRange {
2159 assert_eq!(None, overlapping::<u8>(&[]));
2160 assert_eq!(None, overlapping(&[sp(1, EndBound::Included(4))]));
2163 overlapping(&[sp(1, EndBound::Included(4)), sp(5, EndBound::Included(6))])
2168 sp(1, EndBound::Included(4)),
2169 sp(5, EndBound::Included(6)),
2170 sp(10, EndBound::Included(11))
2174 Some((&sp(1, EndBound::Included(4)), &sp(3, EndBound::Included(6)))),
2175 overlapping(&[sp(1, EndBound::Included(4)), sp(3, EndBound::Included(6))])
2178 Some((&sp(5, EndBound::Included(6)), &sp(6, EndBound::Included(11)))),
2180 sp(1, EndBound::Included(4)),
2181 sp(5, EndBound::Included(6)),
2182 sp(6, EndBound::Included(11))