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::higher;
6 use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
7 use clippy_utils::sugg::Sugg;
8 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, peel_mid_ty_refs};
9 use clippy_utils::visitors::is_local_used;
11 get_parent_expr, is_expn_of, is_lang_ctor, is_lint_allowed, is_refutable, is_unit_expr, is_wild, meets_msrv, msrvs,
12 path_to_local, path_to_local_id, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, remove_blocks,
15 use clippy_utils::{paths, search_same, SpanlessEq, SpanlessHash};
17 use core::iter::{once, ExactSizeIterator};
18 use if_chain::if_chain;
19 use rustc_ast::ast::{Attribute, LitKind};
20 use rustc_errors::Applicability;
21 use rustc_hir::def::{CtorKind, DefKind, Res};
22 use rustc_hir::LangItem::{OptionNone, OptionSome};
24 self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, HirId, Local, MatchSource,
25 Mutability, Node, Pat, PatKind, PathSegment, QPath, RangeEnd, TyKind,
27 use rustc_hir::{HirIdMap, HirIdSet};
28 use rustc_lint::{LateContext, LateLintPass, LintContext};
29 use rustc_middle::ty::{self, Ty, TyS, VariantDef};
30 use rustc_semver::RustcVersion;
31 use rustc_session::{declare_tool_lint, impl_lint_pass};
32 use rustc_span::source_map::{Span, Spanned};
34 use std::cmp::Ordering;
35 use std::collections::hash_map::Entry;
38 declare_clippy_lint! {
40 /// Checks for matches with a single arm where an `if let`
41 /// will usually suffice.
43 /// ### Why is this bad?
44 /// Just readability – `if let` nests less than a `match`.
48 /// # fn bar(stool: &str) {}
49 /// # let x = Some("abc");
52 /// Some(ref foo) => bar(foo),
57 /// if let Some(ref foo) = x {
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 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),
135 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
138 declare_clippy_lint! {
140 /// Checks for matches where match expression is a `bool`. It
141 /// suggests to replace the expression with an `if...else` block.
143 /// ### Why is this bad?
144 /// It makes the code less readable.
150 /// let condition: bool = true;
151 /// match condition {
156 /// Use if/else instead:
160 /// let condition: bool = true;
169 "a `match` on a boolean expression instead of an `if..else` block"
172 declare_clippy_lint! {
174 /// Checks for overlapping match arms.
176 /// ### Why is this bad?
177 /// It is likely to be an error and if not, makes the code
184 /// 1..=10 => println!("1 ... 10"),
185 /// 5..=15 => println!("5 ... 15"),
189 pub MATCH_OVERLAPPING_ARM,
191 "a `match` with overlapping arms"
194 declare_clippy_lint! {
196 /// Checks for arm which matches all errors with `Err(_)`
197 /// and take drastic actions like `panic!`.
199 /// ### Why is this bad?
200 /// It is generally a bad practice, similar to
201 /// catching all exceptions in java with `catch(Exception)`
205 /// let x: Result<i32, &str> = Ok(3);
207 /// Ok(_) => println!("ok"),
208 /// Err(_) => panic!("err"),
211 pub MATCH_WILD_ERR_ARM,
213 "a `match` with `Err(_)` arm and take drastic actions"
216 declare_clippy_lint! {
218 /// Checks for match which is used to add a reference to an
221 /// ### Why is this bad?
222 /// Using `as_ref()` or `as_mut()` instead is shorter.
226 /// let x: Option<()> = None;
229 /// let r: Option<&()> = match x {
231 /// Some(ref v) => Some(v),
235 /// let r: Option<&()> = x.as_ref();
239 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
242 declare_clippy_lint! {
244 /// Checks for wildcard enum matches using `_`.
246 /// ### Why is this bad?
247 /// New enum variants added by library updates can be missed.
249 /// ### Known problems
250 /// Suggested replacements may be incorrect if guards exhaustively cover some
251 /// variants, and also may not use correct path to enum if it's not present in the current scope.
255 /// # enum Foo { A(usize), B(usize) }
256 /// # let x = Foo::B(1);
269 pub WILDCARD_ENUM_MATCH_ARM,
271 "a wildcard enum match arm using `_`"
274 declare_clippy_lint! {
276 /// Checks for wildcard enum matches for a single variant.
278 /// ### Why is this bad?
279 /// New enum variants added by library updates can be missed.
281 /// ### Known problems
282 /// Suggested replacements may not use correct path to enum
283 /// if it's not present in the current scope.
287 /// # enum Foo { A, B, C }
288 /// # let x = Foo::B;
303 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
305 "a wildcard enum match for a single variant"
308 declare_clippy_lint! {
310 /// Checks for wildcard pattern used with others patterns in same match arm.
312 /// ### Why is this bad?
313 /// Wildcard pattern already covers any other pattern as it will match anyway.
314 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
330 pub WILDCARD_IN_OR_PATTERNS,
332 "a wildcard pattern used with others patterns in same match arm"
335 declare_clippy_lint! {
337 /// Checks for matches being used to destructure a single-variant enum
338 /// or tuple struct where a `let` will suffice.
340 /// ### Why is this bad?
341 /// Just readability – `let` doesn't nest, whereas a `match` does.
349 /// let wrapper = Wrapper::Data(42);
351 /// let data = match wrapper {
352 /// Wrapper::Data(i) => i,
356 /// The correct use would be:
362 /// let wrapper = Wrapper::Data(42);
363 /// let Wrapper::Data(data) = wrapper;
365 pub INFALLIBLE_DESTRUCTURING_MATCH,
367 "a `match` statement with a single infallible arm instead of a `let`"
370 declare_clippy_lint! {
372 /// Checks for useless match that binds to only one value.
374 /// ### Why is this bad?
375 /// Readability and needless complexity.
377 /// ### Known problems
378 /// Suggested replacements may be incorrect when `match`
379 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
394 /// let (c, d) = (a, b);
396 pub MATCH_SINGLE_BINDING,
398 "a match with a single binding instead of using `let` statement"
401 declare_clippy_lint! {
403 /// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
405 /// ### Why is this bad?
406 /// Correctness and readability. It's like having a wildcard pattern after
407 /// matching all enum variants explicitly.
411 /// # struct A { a: i32 }
412 /// let a = A { a: 5 };
416 /// A { a: 5, .. } => {},
422 /// A { a: 5 } => {},
426 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
428 "a match on a struct that binds all fields but still uses the wildcard pattern"
431 declare_clippy_lint! {
433 /// Lint for redundant pattern matching over `Result`, `Option`,
434 /// `std::task::Poll` or `std::net::IpAddr`
436 /// ### Why is this bad?
437 /// It's more concise and clear to just use the proper
440 /// ### Known problems
441 /// This will change the drop order for the matched type. Both `if let` and
442 /// `while let` will drop the value at the end of the block, both `if` and `while` will drop the
443 /// value before entering the block. For most types this change will not matter, but for a few
444 /// types this will not be an acceptable change (e.g. locks). See the
445 /// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about
450 /// # use std::task::Poll;
451 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
452 /// if let Ok(_) = Ok::<i32, i32>(42) {}
453 /// if let Err(_) = Err::<i32, i32>(42) {}
454 /// if let None = None::<()> {}
455 /// if let Some(_) = Some(42) {}
456 /// if let Poll::Pending = Poll::Pending::<()> {}
457 /// if let Poll::Ready(_) = Poll::Ready(42) {}
458 /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
459 /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
460 /// match Ok::<i32, i32>(42) {
466 /// The more idiomatic use would be:
469 /// # use std::task::Poll;
470 /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
471 /// if Ok::<i32, i32>(42).is_ok() {}
472 /// if Err::<i32, i32>(42).is_err() {}
473 /// if None::<()>.is_none() {}
474 /// if Some(42).is_some() {}
475 /// if Poll::Pending::<()>.is_pending() {}
476 /// if Poll::Ready(42).is_ready() {}
477 /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
478 /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
479 /// Ok::<i32, i32>(42).is_ok();
481 pub REDUNDANT_PATTERN_MATCHING,
483 "use the proper utility function avoiding an `if let`"
486 declare_clippy_lint! {
488 /// Checks for `match` or `if let` expressions producing a
489 /// `bool` that could be written using `matches!`
491 /// ### Why is this bad?
492 /// Readability and needless complexity.
494 /// ### Known problems
495 /// This lint falsely triggers, if there are arms with
496 /// `cfg` attributes that remove an arm evaluating to `false`.
503 /// let a = match x {
508 /// let a = if let Some(0) = x {
515 /// let a = matches!(x, Some(0));
517 pub MATCH_LIKE_MATCHES_MACRO,
519 "a match that could be written with the matches! macro"
522 declare_clippy_lint! {
524 /// Checks for `match` with identical arm bodies.
526 /// ### Why is this bad?
527 /// This is probably a copy & paste error. If arm bodies
528 /// are the same on purpose, you can factor them
529 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
531 /// ### Known problems
532 /// False positive possible with order dependent `match`
534 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
541 /// Baz => bar(), // <= oops
545 /// This should probably be
550 /// Baz => baz(), // <= fixed
554 /// or if the original code was not a typo:
557 /// Bar | Baz => bar(), // <= shows the intent better
563 "`match` with identical arm bodies"
568 msrv: Option<RustcVersion>,
569 infallible_destructuring_match_linted: bool,
574 pub fn new(msrv: Option<RustcVersion>) -> Self {
582 impl_lint_pass!(Matches => [
587 MATCH_OVERLAPPING_ARM,
590 WILDCARD_ENUM_MATCH_ARM,
591 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
592 WILDCARD_IN_OR_PATTERNS,
593 MATCH_SINGLE_BINDING,
594 INFALLIBLE_DESTRUCTURING_MATCH,
595 REST_PAT_IN_FULLY_BOUND_STRUCTS,
596 REDUNDANT_PATTERN_MATCHING,
597 MATCH_LIKE_MATCHES_MACRO,
601 impl<'tcx> LateLintPass<'tcx> for Matches {
602 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
603 if expr.span.from_expansion() {
607 redundant_pattern_match::check(cx, expr);
609 if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) {
610 if !check_match_like_matches(cx, expr) {
611 lint_match_arms(cx, expr);
614 lint_match_arms(cx, expr);
617 if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind {
618 check_single_match(cx, ex, arms, expr);
619 check_match_bool(cx, ex, arms, expr);
620 check_overlapping_arms(cx, ex, arms);
621 check_wild_err_arm(cx, ex, arms);
622 check_wild_enum_match(cx, ex, arms);
623 check_match_as_ref(cx, ex, arms, expr);
624 check_wild_in_or_pats(cx, arms);
626 if self.infallible_destructuring_match_linted {
627 self.infallible_destructuring_match_linted = false;
629 check_match_single_binding(cx, ex, arms, expr);
632 if let ExprKind::Match(ex, arms, _) = expr.kind {
633 check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr);
637 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
639 if !local.span.from_expansion();
640 if let Some(expr) = local.init;
641 if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
642 if arms.len() == 1 && arms[0].guard.is_none();
643 if let PatKind::TupleStruct(
644 QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
646 if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
647 let body = remove_blocks(arms[0].body);
648 if path_to_local_id(body, arg);
651 let mut applicability = Applicability::MachineApplicable;
652 self.infallible_destructuring_match_linted = true;
655 INFALLIBLE_DESTRUCTURING_MATCH,
657 "you seem to be trying to use `match` to destructure a single infallible pattern. \
658 Consider using `let`",
662 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
663 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
664 snippet_with_applicability(cx, target.span, "..", &mut applicability),
672 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
674 if !pat.span.from_expansion();
675 if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
676 if let Some(def_id) = path.res.opt_def_id();
677 let ty = cx.tcx.type_of(def_id);
678 if let ty::Adt(def, _) = ty.kind();
679 if def.is_struct() || def.is_union();
680 if fields.len() == def.non_enum_variant().fields.len();
685 REST_PAT_IN_FULLY_BOUND_STRUCTS,
687 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
689 "consider removing `..` from this binding",
695 extract_msrv_attr!(LateContext);
699 fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
700 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
701 if expr.span.from_expansion() {
702 // Don't lint match expressions present in
703 // macro_rules! block
706 if let PatKind::Or(..) = arms[0].pat.kind {
707 // don't lint for or patterns for now, this makes
708 // the lint noisy in unnecessary situations
711 let els = arms[1].body;
712 let els = if is_unit_expr(remove_blocks(els)) {
714 } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
715 if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
716 // single statement/expr "else" block, don't lint
719 // block with 2+ statements or 1 expr and 1+ statement
722 // not a block, don't lint
726 let ty = cx.typeck_results().expr_ty(ex);
727 if *ty.kind() != ty::Bool || is_lint_allowed(cx, MATCH_BOOL, ex.hir_id) {
728 check_single_match_single_pattern(cx, ex, arms, expr, els);
729 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
734 fn check_single_match_single_pattern(
735 cx: &LateContext<'_>,
739 els: Option<&Expr<'_>>,
741 if is_wild(arms[1].pat) {
742 report_single_match_single_pattern(cx, ex, arms, expr, els);
746 fn report_single_match_single_pattern(
747 cx: &LateContext<'_>,
751 els: Option<&Expr<'_>>,
753 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
754 let els_str = els.map_or(String::new(), |els| {
755 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
758 let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat);
759 let (msg, sugg) = if_chain! {
760 if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind;
761 let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex));
762 if let Some(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait();
763 if let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait();
764 if ty.is_integral() || ty.is_char() || ty.is_str()
765 || (implements_trait(cx, ty, spe_trait_id, &[])
766 && implements_trait(cx, ty, pe_trait_id, &[ty.into()]));
768 // scrutinee derives PartialEq and the pattern is a constant.
769 let pat_ref_count = match pat.kind {
770 // string literals are already a reference.
771 PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1,
774 // References are only implicitly added to the pattern, so no overflow here.
775 // e.g. will work: match &Some(_) { Some(_) => () }
776 // will not: match Some(_) { &Some(_) => () }
777 let ref_count_diff = ty_ref_count - pat_ref_count;
779 // Try to remove address of expressions first.
780 let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff);
781 let ref_count_diff = ref_count_diff - removed;
783 let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`";
785 "if {} == {}{} {}{}",
786 snippet(cx, ex.span, ".."),
787 // PartialEq for different reference counts may not exist.
788 "&".repeat(ref_count_diff),
789 snippet(cx, arms[0].pat.span, ".."),
790 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
795 let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`";
797 "if let {} = {} {}{}",
798 snippet(cx, arms[0].pat.span, ".."),
799 snippet(cx, ex.span, ".."),
800 expr_block(cx, arms[0].body, None, "..", Some(expr.span)),
814 Applicability::HasPlaceholders,
818 fn check_single_match_opt_like(
819 cx: &LateContext<'_>,
824 els: Option<&Expr<'_>>,
826 // list of candidate `Enum`s we know will never get any more members
828 (&paths::COW, "Borrowed"),
829 (&paths::COW, "Cow::Borrowed"),
830 (&paths::COW, "Cow::Owned"),
831 (&paths::COW, "Owned"),
832 (&paths::OPTION, "None"),
833 (&paths::RESULT, "Err"),
834 (&paths::RESULT, "Ok"),
837 let path = match arms[1].pat.kind {
838 PatKind::TupleStruct(ref path, inner, _) => {
839 // Contains any non wildcard patterns (e.g., `Err(err)`)?
840 if !inner.iter().all(is_wild) {
843 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
845 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
846 PatKind::Path(ref path) => {
847 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
852 for &(ty_path, pat_path) in candidates {
853 if path == *pat_path && match_type(cx, ty, ty_path) {
854 report_single_match_single_pattern(cx, ex, arms, expr, els);
859 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
860 // Type of expression is `bool`.
861 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
866 "you seem to be trying to match on a boolean expression",
870 let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
871 if let ExprKind::Lit(ref lit) = arm_bool.kind {
873 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
874 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
884 if let Some((true_expr, false_expr)) = exprs {
885 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
886 (false, false) => Some(format!(
888 snippet(cx, ex.span, "b"),
889 expr_block(cx, true_expr, None, "..", Some(expr.span)),
890 expr_block(cx, false_expr, None, "..", Some(expr.span))
892 (false, true) => Some(format!(
894 snippet(cx, ex.span, "b"),
895 expr_block(cx, true_expr, None, "..", Some(expr.span))
898 let test = Sugg::hir(cx, ex, "..");
902 expr_block(cx, false_expr, None, "..", Some(expr.span))
905 (true, true) => None,
908 if let Some(sugg) = sugg {
909 diag.span_suggestion(
911 "consider using an `if`/`else` expression",
913 Applicability::HasPlaceholders,
923 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
924 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
925 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
926 if !ranges.is_empty() {
927 if let Some((start, end)) = overlapping(&ranges) {
930 MATCH_OVERLAPPING_ARM,
932 "some ranges overlap",
934 "overlaps with this",
941 fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
942 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
943 if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
945 if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
946 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
947 if path_str == "Err" {
948 let mut matching_wild = inner.iter().any(is_wild);
949 let mut ident_bind_name = String::from("_");
951 // Looking for unused bindings (i.e.: `_e`)
952 for pat in inner.iter() {
953 if let PatKind::Binding(_, id, ident, None) = pat.kind {
954 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
955 ident_bind_name = (&ident.name.as_str()).to_string();
956 matching_wild = true;
963 if is_panic_call(arm.body);
965 // `Err(_)` or `Err(_e)` arm with `panic!` found
966 span_lint_and_note(cx,
969 &format!("`Err({})` matches all errors", &ident_bind_name),
971 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
981 enum CommonPrefixSearcher<'a> {
983 Path(&'a [PathSegment<'a>]),
986 impl CommonPrefixSearcher<'a> {
987 fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
989 [path @ .., _] => self.with_prefix(path),
994 fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
996 Self::None => *self = Self::Path(path),
997 Self::Path(self_path)
1000 .map(|p| p.ident.name)
1001 .eq(self_path.iter().map(|p| p.ident.name)) => {},
1002 Self::Path(_) => *self = Self::Mixed,
1008 fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
1009 let attrs = cx.tcx.get_attrs(variant_def.def_id);
1010 clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
1013 #[allow(clippy::too_many_lines)]
1014 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
1015 let ty = cx.typeck_results().expr_ty(ex).peel_refs();
1016 let adt_def = match ty.kind() {
1018 if adt_def.is_enum()
1019 && !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
1026 // First pass - check for violation, but don't do much book-keeping because this is hopefully
1027 // the uncommon case, and the book-keeping is slightly expensive.
1028 let mut wildcard_span = None;
1029 let mut wildcard_ident = None;
1030 let mut has_non_wild = false;
1032 match peel_hir_pat_refs(arm.pat).0.kind {
1033 PatKind::Wild => wildcard_span = Some(arm.pat.span),
1034 PatKind::Binding(_, _, ident, None) => {
1035 wildcard_span = Some(arm.pat.span);
1036 wildcard_ident = Some(ident);
1038 _ => has_non_wild = true,
1041 let wildcard_span = match wildcard_span {
1042 Some(x) if has_non_wild => x,
1046 // Accumulate the variants which should be put in place of the wildcard because they're not
1048 let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
1049 let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
1051 let mut path_prefix = CommonPrefixSearcher::None;
1053 // Guards mean that this case probably isn't exhaustively covered. Technically
1054 // this is incorrect, as we should really check whether each variant is exhaustively
1055 // covered by the set of guards that cover it, but that's really hard to do.
1056 recurse_or_patterns(arm.pat, |pat| {
1057 let path = match &peel_hir_pat_refs(pat).0.kind {
1058 PatKind::Path(path) => {
1059 #[allow(clippy::match_same_arms)]
1060 let id = match cx.qpath_res(path, pat.hir_id) {
1061 Res::Def(DefKind::Const | DefKind::ConstParam | DefKind::AnonConst, _) => return,
1062 Res::Def(_, id) => id,
1065 if arm.guard.is_none() {
1066 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1070 PatKind::TupleStruct(path, patterns, ..) => {
1071 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1072 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
1073 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1078 PatKind::Struct(path, patterns, ..) => {
1079 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1080 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
1081 missing_variants.retain(|e| e.def_id != id);
1089 QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
1090 QPath::TypeRelative(
1092 kind: TyKind::Path(QPath::Resolved(_, path)),
1096 ) => path_prefix.with_prefix(path.segments),
1102 let format_suggestion = |variant: &VariantDef| {
1105 if let Some(ident) = wildcard_ident {
1106 format!("{} @ ", ident.name)
1110 if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
1111 let mut s = String::new();
1112 for seg in path_prefix {
1113 s.push_str(&seg.ident.as_str());
1118 let mut s = cx.tcx.def_path_str(adt_def.did);
1123 match variant.ctor_kind {
1124 CtorKind::Fn if variant.fields.len() == 1 => "(_)",
1125 CtorKind::Fn => "(..)",
1126 CtorKind::Const => "",
1127 CtorKind::Fictive => "{ .. }",
1132 match missing_variants.as_slice() {
1134 [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
1136 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1138 "wildcard matches only a single variant and will also match any future added variants",
1140 format_suggestion(x),
1141 Applicability::MaybeIncorrect,
1144 let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
1145 let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
1146 suggestions.push("_".into());
1147 "wildcard matches known variants and will also match future added variants"
1149 "wildcard match will also match any future added variants"
1154 WILDCARD_ENUM_MATCH_ARM,
1158 suggestions.join(" | "),
1159 Applicability::MaybeIncorrect,
1165 // If the block contains only a `panic!` macro (as expression or statement)
1166 fn is_panic_call(expr: &Expr<'_>) -> bool {
1167 // Unwrap any wrapping blocks
1168 let span = if let ExprKind::Block(block, _) = expr.kind {
1169 match (&block.expr, block.stmts.len(), block.stmts.first()) {
1170 (&Some(exp), 0, _) => exp.span,
1171 (&None, 1, Some(stmt)) => stmt.span,
1178 is_expn_of(span, "panic").is_some() && is_expn_of(span, "unreachable").is_none()
1181 fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
1184 I: Clone + Iterator<Item = &'a Pat<'b>>,
1186 if !has_multiple_ref_pats(pats.clone()) {
1190 let (first_sugg, msg, title);
1191 let span = ex.span.source_callsite();
1192 if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
1193 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1195 title = "you don't need to add `&` to both the expression and the patterns";
1197 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1198 msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
1199 title = "you don't need to add `&` to all patterns";
1202 let remaining_suggs = pats.filter_map(|pat| {
1203 if let PatKind::Ref(refp, _) = pat.kind {
1204 Some((pat.span, snippet(cx, refp.span, "..").to_string()))
1210 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1211 if !expr.span.from_expansion() {
1212 multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
1217 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1218 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1219 let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
1220 is_ref_some_arm(cx, &arms[1])
1221 } else if is_none_arm(cx, &arms[1]) {
1222 is_ref_some_arm(cx, &arms[0])
1226 if let Some(rb) = arm_ref {
1227 let suggestion = if rb == BindingAnnotation::Ref {
1233 let output_ty = cx.typeck_results().expr_ty(expr);
1234 let input_ty = cx.typeck_results().expr_ty(ex);
1236 let cast = if_chain! {
1237 if let ty::Adt(_, substs) = input_ty.kind();
1238 let input_ty = substs.type_at(0);
1239 if let ty::Adt(_, substs) = output_ty.kind();
1240 let output_ty = substs.type_at(0);
1241 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1242 if input_ty != output_ty;
1250 let mut applicability = Applicability::MachineApplicable;
1255 &format!("use `{}()` instead", suggestion),
1259 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1269 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1271 if let PatKind::Or(fields) = arm.pat.kind {
1272 // look for multiple fields in this arm that contains at least one Wild pattern
1273 if fields.len() > 1 && fields.iter().any(is_wild) {
1276 WILDCARD_IN_OR_PATTERNS,
1278 "wildcard pattern covers any other pattern as it will match anyway",
1280 "consider handling `_` separately",
1287 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1288 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1289 if let Some(higher::IfLet {
1293 if_else: Some(if_else),
1294 }) = higher::IfLet::hir(cx, expr)
1296 return find_matches_sugg(
1299 array::IntoIter::new([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
1305 if let ExprKind::Match(scrut, arms, MatchSource::Normal) = expr.kind {
1306 return find_matches_sugg(
1309 arms.iter().map(|arm| {
1311 cx.tcx.hir().attrs(arm.hir_id),
1325 /// Lint a `match` or `if let` for replacement by `matches!`
1326 fn find_matches_sugg<'a, 'b, I>(
1327 cx: &LateContext<'_>,
1336 + DoubleEndedIterator
1341 Option<&'a Pat<'b>>,
1343 Option<&'a Guard<'b>>,
1349 if cx.typeck_results().expr_ty(expr).is_bool();
1350 if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back();
1351 let iter_without_last = iter.clone();
1352 if let Some((first_attrs, _, first_expr, first_guard)) = iter.next();
1353 if let Some(b0) = find_bool_lit(&first_expr.kind, is_if_let);
1354 if let Some(b1) = find_bool_lit(&last_expr.kind, is_if_let);
1356 if first_guard.is_none() || iter.len() == 0;
1357 if first_attrs.is_empty();
1360 find_bool_lit(&arm.2.kind, is_if_let).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty()
1363 if let Some(last_pat) = last_pat_opt {
1364 if !is_wild(last_pat) {
1369 // The suggestion may be incorrect, because some arms can have `cfg` attributes
1370 // evaluated into `false` and so such arms will be stripped before.
1371 let mut applicability = Applicability::MaybeIncorrect;
1373 use itertools::Itertools as _;
1376 let pat_span = arm.1?.span;
1377 Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability))
1381 let pat_and_guard = if let Some(Guard::If(g)) = first_guard {
1382 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1387 // strip potential borrows (#6503), but only if the type is a reference
1388 let mut ex_new = ex;
1389 if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
1390 if let ty::Ref(..) = cx.typeck_results().expr_ty(ex_inner).kind() {
1396 MATCH_LIKE_MATCHES_MACRO,
1398 &format!("{} expression looks like `matches!` macro", if is_if_let { "if let .. else" } else { "match" }),
1401 "{}matches!({}, {})",
1402 if b0 { "" } else { "!" },
1403 snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
1415 /// Extract a `bool` or `{ bool }`
1416 fn find_bool_lit(ex: &ExprKind<'_>, is_if_let: bool) -> Option<bool> {
1418 ExprKind::Lit(Spanned {
1419 node: LitKind::Bool(b), ..
1429 if let ExprKind::Lit(Spanned {
1430 node: LitKind::Bool(b), ..
1442 #[allow(clippy::too_many_lines)]
1443 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1444 if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1449 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1450 // to prevent false positives as there is currently no better way to detect if code was excluded by
1451 // a macro. See PR #6435
1453 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1454 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1455 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1456 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1457 if rest_snippet.contains("=>");
1459 // The code it self contains another thick arrow "=>"
1460 // -> Either another arm or a comment
1465 let matched_vars = ex.span;
1466 let bind_names = arms[0].pat.span;
1467 let match_body = remove_blocks(arms[0].body);
1468 let mut snippet_body = if match_body.span.from_expansion() {
1469 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1471 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1474 // Do we need to add ';' to suggestion ?
1475 match match_body.kind {
1476 ExprKind::Block(block, _) => {
1477 // macro + expr_ty(body) == ()
1478 if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
1479 snippet_body.push(';');
1483 // expr_ty(body) == ()
1484 if cx.typeck_results().expr_ty(match_body).is_unit() {
1485 snippet_body.push(';');
1490 let mut applicability = Applicability::MaybeIncorrect;
1491 match arms[0].pat.kind {
1492 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1493 // If this match is in a local (`let`) stmt
1494 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1496 parent_let_node.span,
1498 "let {} = {};\n{}let {} = {};",
1499 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1500 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1501 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1502 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1507 // If we are in closure, we need curly braces around suggestion
1508 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1509 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1510 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1511 if let ExprKind::Closure(..) = parent_expr.kind {
1512 cbrace_end = format!("\n{}}}", indent);
1513 // Fix body indent due to the closure
1514 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1515 cbrace_start = format!("{{\n{}", indent);
1518 // If the parent is already an arm, and the body is another match statement,
1519 // we need curly braces around suggestion
1520 let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
1521 if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
1522 if let ExprKind::Match(..) = arm.body.kind {
1523 cbrace_end = format!("\n{}}}", indent);
1524 // Fix body indent due to the match
1525 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1526 cbrace_start = format!("{{\n{}", indent);
1532 "{}let {} = {};\n{}{}{}",
1534 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1535 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1544 MATCH_SINGLE_BINDING,
1546 "this match could be written as a `let` statement",
1547 "consider using `let` statement",
1553 if ex.can_have_side_effects() {
1554 let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
1557 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1563 MATCH_SINGLE_BINDING,
1565 "this match could be replaced by its scrutinee and body",
1566 "consider using the scrutinee and body instead",
1573 MATCH_SINGLE_BINDING,
1575 "this match could be replaced by its body itself",
1576 "consider using the match body instead",
1578 Applicability::MachineApplicable,
1586 /// Returns true if the `ex` match expression is in a local (`let`) statement
1587 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1588 let map = &cx.tcx.hir();
1590 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1591 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1593 return Some(parent_let_expr);
1599 /// Gets all arms that are unbounded `PatRange`s.
1600 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
1603 if let Arm { pat, guard: None, .. } = *arm {
1604 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1605 let lhs = match lhs {
1606 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1607 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1609 let rhs = match rhs {
1610 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1611 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1614 let lhs_val = lhs.int_value(cx, ty)?;
1615 let rhs_val = rhs.int_value(cx, ty)?;
1617 let rhs_bound = match range_end {
1618 RangeEnd::Included => Bound::Included(rhs_val),
1619 RangeEnd::Excluded => Bound::Excluded(rhs_val),
1621 return Some(SpannedRange {
1623 node: (lhs_val, rhs_bound),
1627 if let PatKind::Lit(value) = pat.kind {
1628 let value = constant_full_int(cx, cx.typeck_results(), value)?;
1629 return Some(SpannedRange {
1631 node: (value, Bound::Included(value)),
1640 #[derive(Debug, Eq, PartialEq)]
1641 pub struct SpannedRange<T> {
1643 pub node: (T, Bound<T>),
1646 // Checks if arm has the form `None => None`
1647 fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
1648 matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
1651 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1652 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
1654 if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
1655 if is_lang_ctor(cx, qpath, OptionSome);
1656 if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
1657 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1658 if let ExprKind::Call(e, args) = remove_blocks(arm.body).kind;
1659 if let ExprKind::Path(ref some_path) = e.kind;
1660 if is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1;
1661 if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
1662 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1670 fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
1673 I: Iterator<Item = &'a Pat<'b>>,
1675 let mut ref_count = 0;
1676 for opt in pats.map(|pat| match pat.kind {
1677 PatKind::Ref(..) => Some(true), // &-patterns
1678 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1679 _ => None, // any other pattern is not fine
1681 if let Some(inner) = opt {
1692 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1696 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1698 Start(T, &'a SpannedRange<T>),
1699 End(Bound<T>, &'a SpannedRange<T>),
1702 impl<'a, T: Copy> Kind<'a, T> {
1703 fn value(self) -> Bound<T> {
1705 Kind::Start(t, _) => Bound::Included(t),
1706 Kind::End(t, _) => t,
1711 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1712 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1713 Some(self.cmp(other))
1717 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1718 fn cmp(&self, other: &Self) -> Ordering {
1719 match (self.value(), other.value()) {
1720 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => {
1721 let value_cmp = a.cmp(&b);
1722 // In the case of ties, starts come before ends
1723 if value_cmp == Ordering::Equal {
1724 match (self, other) {
1725 (Kind::Start(..), Kind::End(..)) => Ordering::Less,
1726 (Kind::End(..), Kind::Start(..)) => Ordering::Greater,
1727 _ => Ordering::Equal,
1733 // Range patterns cannot be unbounded (yet)
1734 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1735 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1736 Ordering::Equal => Ordering::Greater,
1739 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1740 Ordering::Equal => Ordering::Less,
1747 let mut values = Vec::with_capacity(2 * ranges.len());
1750 values.push(Kind::Start(r.node.0, r));
1751 values.push(Kind::End(r.node.1, r));
1756 let mut started = vec![];
1758 for value in values {
1760 Kind::Start(_, r) => started.push(r),
1761 Kind::End(_, er) => {
1762 let mut overlap = None;
1764 while let Some(sr) = started.pop() {
1771 if let Some(sr) = overlap {
1772 return Some((er, sr));
1781 mod redundant_pattern_match {
1782 use super::REDUNDANT_PATTERN_MATCHING;
1783 use clippy_utils::diagnostics::span_lint_and_then;
1784 use clippy_utils::higher;
1785 use clippy_utils::source::snippet;
1786 use clippy_utils::sugg::Sugg;
1787 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
1788 use clippy_utils::{is_lang_ctor, is_qpath_def_path, is_trait_method, paths};
1789 use if_chain::if_chain;
1790 use rustc_ast::ast::LitKind;
1791 use rustc_data_structures::fx::FxHashSet;
1792 use rustc_errors::Applicability;
1793 use rustc_hir::LangItem::{OptionNone, OptionSome, PollPending, PollReady, ResultErr, ResultOk};
1795 intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
1796 Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
1798 use rustc_lint::LateContext;
1799 use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
1800 use rustc_span::sym;
1802 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1803 if let Some(higher::IfLet {
1808 }) = higher::IfLet::hir(cx, expr)
1810 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
1812 if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
1813 find_sugg_for_match(cx, expr, op, arms);
1815 if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
1816 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
1820 /// Checks if the drop order for a type matters. Some std types implement drop solely to
1821 /// deallocate memory. For these types, and composites containing them, changing the drop order
1822 /// won't result in any observable side effects.
1823 fn type_needs_ordered_drop(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
1824 type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
1827 fn type_needs_ordered_drop_inner(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
1828 if !seen.insert(ty) {
1831 if !ty.needs_drop(cx.tcx, cx.param_env) {
1837 .map_or(false, |id| implements_trait(cx, ty, id, &[]))
1839 // This type doesn't implement drop, so no side effects here.
1840 // Check if any component type has any.
1842 ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1843 ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
1844 ty::Adt(adt, subs) => adt
1846 .map(|f| f.ty(cx.tcx, subs))
1847 .any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1851 // Check for std types which implement drop, but only for memory allocation.
1852 else if is_type_diagnostic_item(cx, ty, sym::Vec)
1853 || is_type_lang_item(cx, ty, LangItem::OwnedBox)
1854 || is_type_diagnostic_item(cx, ty, sym::Rc)
1855 || is_type_diagnostic_item(cx, ty, sym::Arc)
1856 || is_type_diagnostic_item(cx, ty, sym::cstring_type)
1857 || is_type_diagnostic_item(cx, ty, sym::BTreeMap)
1858 || is_type_diagnostic_item(cx, ty, sym::LinkedList)
1859 || match_type(cx, ty, &paths::WEAK_RC)
1860 || match_type(cx, ty, &paths::WEAK_ARC)
1862 // Check all of the generic arguments.
1863 if let ty::Adt(_, subs) = ty.kind() {
1864 subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
1873 // Extract the generic arguments out of a type
1874 fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
1876 if let ty::Adt(_, subs) = ty.kind();
1877 if let Some(sub) = subs.get(index);
1878 if let GenericArgKind::Type(sub_ty) = sub.unpack();
1887 // Checks if there are any temporaries created in the given expression for which drop order
1889 fn temporaries_need_ordered_drop(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1890 struct V<'a, 'tcx> {
1891 cx: &'a LateContext<'tcx>,
1894 impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
1895 type Map = ErasedMap<'tcx>;
1896 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1897 NestedVisitorMap::None
1900 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
1902 // Taking the reference of a value leaves a temporary
1903 // e.g. In `&String::new()` the string is a temporary value.
1904 // Remaining fields are temporary values
1905 // e.g. In `(String::new(), 0).1` the string is a temporary value.
1906 ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
1907 if !matches!(expr.kind, ExprKind::Path(_)) {
1908 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
1911 self.visit_expr(expr);
1915 // the base type is alway taken by reference.
1916 // e.g. In `(vec![0])[0]` the vector is a temporary value.
1917 ExprKind::Index(base, index) => {
1918 if !matches!(base.kind, ExprKind::Path(_)) {
1919 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
1922 self.visit_expr(base);
1925 self.visit_expr(index);
1927 // Method calls can take self by reference.
1928 // e.g. In `String::new().len()` the string is a temporary value.
1929 ExprKind::MethodCall(_, _, [self_arg, args @ ..], _) => {
1930 if !matches!(self_arg.kind, ExprKind::Path(_)) {
1931 let self_by_ref = self
1934 .type_dependent_def_id(expr.hir_id)
1935 .map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
1937 && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg))
1941 self.visit_expr(self_arg);
1944 args.iter().for_each(|arg| self.visit_expr(arg));
1946 // Either explicitly drops values, or changes control flow.
1947 ExprKind::DropTemps(_)
1949 | ExprKind::Break(..)
1950 | ExprKind::Yield(..)
1951 | ExprKind::Block(Block { expr: None, .. }, _)
1952 | ExprKind::Loop(..) => (),
1954 // Only consider the final expression.
1955 ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
1957 _ => walk_expr(self, expr),
1962 let mut v = V { cx, res: false };
1967 fn find_sugg_for_if_let<'tcx>(
1968 cx: &LateContext<'tcx>,
1969 expr: &'tcx Expr<'_>,
1971 let_expr: &'tcx Expr<'_>,
1972 keyword: &'static str,
1975 // also look inside refs
1976 let mut kind = &let_pat.kind;
1977 // if we have &None for example, peel it so we can detect "if let None = x"
1978 if let PatKind::Ref(inner, _mutability) = kind {
1981 let op_ty = cx.typeck_results().expr_ty(let_expr);
1982 // Determine which function should be used, and the type contained by the corresponding
1984 let (good_method, inner_ty) = match kind {
1985 PatKind::TupleStruct(ref path, [sub_pat], _) => {
1986 if let PatKind::Wild = sub_pat.kind {
1987 if is_lang_ctor(cx, path, ResultOk) {
1988 ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
1989 } else if is_lang_ctor(cx, path, ResultErr) {
1990 ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
1991 } else if is_lang_ctor(cx, path, OptionSome) {
1992 ("is_some()", op_ty)
1993 } else if is_lang_ctor(cx, path, PollReady) {
1994 ("is_ready()", op_ty)
1995 } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V4) {
1996 ("is_ipv4()", op_ty)
1997 } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V6) {
1998 ("is_ipv6()", op_ty)
2006 PatKind::Path(ref path) => {
2007 let method = if is_lang_ctor(cx, path, OptionNone) {
2009 } else if is_lang_ctor(cx, path, PollPending) {
2014 // `None` and `Pending` don't have an inner type.
2015 (method, cx.tcx.types.unit)
2020 // If this is the last expression in a block or there is an else clause then the whole
2021 // type needs to be considered, not just the inner type of the branch being matched on.
2022 // Note the last expression in a block is dropped after all local bindings.
2023 let check_ty = if has_else
2024 || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
2031 // All temporaries created in the scrutinee expression are dropped at the same time as the
2032 // scrutinee would be, so they have to be considered as well.
2033 // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
2034 // for the duration if body.
2035 let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
2037 // check that `while_let_on_iterator` lint does not trigger
2039 if keyword == "while";
2040 if let ExprKind::MethodCall(method_path, _, _, _) = let_expr.kind;
2041 if method_path.ident.name == sym::next;
2042 if is_trait_method(cx, let_expr, sym::Iterator);
2048 let result_expr = match &let_expr.kind {
2049 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2050 ExprKind::Unary(UnOp::Deref, deref) => deref,
2056 REDUNDANT_PATTERN_MATCHING,
2058 &format!("redundant pattern matching, consider using `{}`", good_method),
2060 // if/while let ... = ... { ... }
2061 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2062 let expr_span = expr.span;
2064 // if/while let ... = ... { ... }
2066 let op_span = result_expr.span.source_callsite();
2068 // if/while let ... = ... { ... }
2069 // ^^^^^^^^^^^^^^^^^^^
2070 let span = expr_span.until(op_span.shrink_to_hi());
2072 let app = if needs_drop {
2073 Applicability::MaybeIncorrect
2075 Applicability::MachineApplicable
2078 let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
2082 diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
2085 diag.note("this will change drop order of the result, as well as all temporaries");
2086 diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
2092 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
2093 if arms.len() == 2 {
2094 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
2096 let found_good_method = match node_pair {
2098 PatKind::TupleStruct(ref path_left, patterns_left, _),
2099 PatKind::TupleStruct(ref path_right, patterns_right, _),
2100 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
2101 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
2102 find_good_method_for_match(
2113 find_good_method_for_match(
2128 (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
2129 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
2130 if patterns.len() == 1 =>
2132 if let PatKind::Wild = patterns[0].kind {
2133 find_good_method_for_match(
2138 &paths::OPTION_SOME,
2139 &paths::OPTION_NONE,
2144 find_good_method_for_match(
2150 &paths::POLL_PENDING,
2162 if let Some(good_method) = found_good_method {
2163 let span = expr.span.to(op.span);
2164 let result_expr = match &op.kind {
2165 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2170 REDUNDANT_PATTERN_MATCHING,
2172 &format!("redundant pattern matching, consider using `{}`", good_method),
2174 diag.span_suggestion(
2177 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
2178 Applicability::MaybeIncorrect, // snippet
2186 #[allow(clippy::too_many_arguments)]
2187 fn find_good_method_for_match<'a>(
2188 cx: &LateContext<'_>,
2190 path_left: &QPath<'_>,
2191 path_right: &QPath<'_>,
2192 expected_left: &[&str],
2193 expected_right: &[&str],
2194 should_be_left: &'a str,
2195 should_be_right: &'a str,
2196 ) -> Option<&'a str> {
2197 let body_node_pair = if is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, expected_left)
2198 && is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_right)
2200 (&(*arms[0].body).kind, &(*arms[1].body).kind)
2201 } else if is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_left)
2202 && is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, expected_right)
2204 (&(*arms[1].body).kind, &(*arms[0].body).kind)
2209 match body_node_pair {
2210 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
2211 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
2212 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
2221 fn test_overlapping() {
2222 use rustc_span::source_map::DUMMY_SP;
2224 let sp = |s, e| SpannedRange {
2229 assert_eq!(None, overlapping::<u8>(&[]));
2230 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
2233 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
2238 sp(1, Bound::Included(4)),
2239 sp(5, Bound::Included(6)),
2240 sp(10, Bound::Included(11))
2244 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
2245 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
2248 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
2250 sp(1, Bound::Included(4)),
2251 sp(5, Bound::Included(6)),
2252 sp(6, Bound::Included(11))
2257 /// Implementation of `MATCH_SAME_ARMS`.
2258 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
2259 if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind {
2260 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
2261 let mut h = SpanlessHash::new(cx);
2262 h.hash_expr(arm.body);
2266 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
2267 let min_index = usize::min(lindex, rindex);
2268 let max_index = usize::max(lindex, rindex);
2270 let mut local_map: HirIdMap<HirId> = HirIdMap::default();
2271 let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
2273 if let Some(a_id) = path_to_local(a);
2274 if let Some(b_id) = path_to_local(b);
2275 let entry = match local_map.entry(a_id) {
2276 Entry::Vacant(entry) => entry,
2277 // check if using the same bindings as before
2278 Entry::Occupied(entry) => return *entry.get() == b_id,
2280 // the names technically don't have to match; this makes the lint more conservative
2281 if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id);
2282 if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b));
2283 if pat_contains_local(lhs.pat, a_id);
2284 if pat_contains_local(rhs.pat, b_id);
2293 // Arms with a guard are ignored, those can’t always be merged together
2294 // This is also the case for arms in-between each there is an arm with a guard
2295 (min_index..=max_index).all(|index| arms[index].guard.is_none())
2296 && SpanlessEq::new(cx)
2297 .expr_fallback(eq_fallback)
2298 .eq_expr(lhs.body, rhs.body)
2299 // these checks could be removed to allow unused bindings
2300 && bindings_eq(lhs.pat, local_map.keys().copied().collect())
2301 && bindings_eq(rhs.pat, local_map.values().copied().collect())
2304 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
2305 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
2310 "this `match` has identical arm bodies",
2312 diag.span_note(i.body.span, "same as this");
2314 // Note: this does not use `span_suggestion` on purpose:
2315 // there is no clean way
2316 // to remove the other arm. Building a span and suggest to replace it to ""
2317 // makes an even more confusing error message. Also in order not to make up a
2318 // span for the whole pattern, the suggestion is only shown when there is only
2319 // one pattern. The user should know about `|` if they are already using it…
2321 let lhs = snippet(cx, i.pat.span, "<pat1>");
2322 let rhs = snippet(cx, j.pat.span, "<pat2>");
2324 if let PatKind::Wild = j.pat.kind {
2325 // if the last arm is _, then i could be integrated into _
2326 // note that i.pat cannot be _, because that would mean that we're
2327 // hiding all the subsequent arms, and rust won't compile
2331 "`{}` has the same arm body as the `_` wildcard, consider removing it",
2336 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
2337 .help("...or consider changing the match arm bodies");
2345 fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool {
2346 let mut result = false;
2347 pat.walk_short(|p| {
2348 result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id);
2354 /// Returns true if all the bindings in the `Pat` are in `ids` and vice versa
2355 fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool {
2356 let mut result = true;
2357 pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
2358 result && ids.is_empty()