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};
16 use core::iter::{once, ExactSizeIterator};
17 use if_chain::if_chain;
18 use rustc_ast::ast::{Attribute, 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, Guard, HirId, Local, MatchSource,
24 Mutability, Node, Pat, PatKind, PathSegment, QPath, RangeEnd, TyKind,
26 use rustc_hir::{HirIdMap, HirIdSet};
27 use rustc_lint::{LateContext, LateLintPass, LintContext};
28 use rustc_middle::ty::{self, Ty, TyS, VariantDef};
29 use rustc_semver::RustcVersion;
30 use rustc_session::{declare_tool_lint, impl_lint_pass};
31 use rustc_span::source_map::{Span, Spanned};
33 use std::cmp::Ordering;
34 use std::collections::hash_map::Entry;
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 !check_match_like_matches(cx, expr) {
625 lint_match_arms(cx, expr);
628 lint_match_arms(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 = remove_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(remove_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(
833 cx: &LateContext<'_>,
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 let path = match arms[1].pat.kind {
852 PatKind::TupleStruct(ref path, inner, _) => {
853 // Contains any non wildcard patterns (e.g., `Err(err)`)?
854 if !inner.iter().all(is_wild) {
857 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
859 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
860 PatKind::Path(ref path) => {
861 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
866 for &(ty_path, pat_path) in candidates {
867 if path == *pat_path && match_type(cx, ty, ty_path) {
868 report_single_match_single_pattern(cx, ex, arms, expr, els);
873 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
874 // Type of expression is `bool`.
875 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
880 "you seem to be trying to match on a boolean expression",
884 let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind {
885 if let ExprKind::Lit(ref lit) = arm_bool.kind {
887 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
888 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
898 if let Some((true_expr, false_expr)) = exprs {
899 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
900 (false, false) => Some(format!(
902 snippet(cx, ex.span, "b"),
903 expr_block(cx, true_expr, None, "..", Some(expr.span)),
904 expr_block(cx, false_expr, None, "..", Some(expr.span))
906 (false, true) => Some(format!(
908 snippet(cx, ex.span, "b"),
909 expr_block(cx, true_expr, None, "..", Some(expr.span))
912 let test = Sugg::hir(cx, ex, "..");
916 expr_block(cx, false_expr, None, "..", Some(expr.span))
919 (true, true) => None,
922 if let Some(sugg) = sugg {
923 diag.span_suggestion(
925 "consider using an `if`/`else` expression",
927 Applicability::HasPlaceholders,
937 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
938 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
939 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
940 if !ranges.is_empty() {
941 if let Some((start, end)) = overlapping(&ranges) {
944 MATCH_OVERLAPPING_ARM,
946 "some ranges overlap",
948 "overlaps with this",
955 fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
956 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
957 if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
959 if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
960 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
961 if path_str == "Err" {
962 let mut matching_wild = inner.iter().any(is_wild);
963 let mut ident_bind_name = String::from("_");
965 // Looking for unused bindings (i.e.: `_e`)
966 for pat in inner.iter() {
967 if let PatKind::Binding(_, id, ident, None) = pat.kind {
968 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
969 ident_bind_name = (&ident.name.as_str()).to_string();
970 matching_wild = true;
977 if is_panic_call(arm.body);
979 // `Err(_)` or `Err(_e)` arm with `panic!` found
980 span_lint_and_note(cx,
983 &format!("`Err({})` matches all errors", &ident_bind_name),
985 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
995 enum CommonPrefixSearcher<'a> {
997 Path(&'a [PathSegment<'a>]),
1000 impl CommonPrefixSearcher<'a> {
1001 fn with_path(&mut self, path: &'a [PathSegment<'a>]) {
1003 [path @ .., _] => self.with_prefix(path),
1008 fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) {
1010 Self::None => *self = Self::Path(path),
1011 Self::Path(self_path)
1014 .map(|p| p.ident.name)
1015 .eq(self_path.iter().map(|p| p.ident.name)) => {},
1016 Self::Path(_) => *self = Self::Mixed,
1022 fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool {
1023 let attrs = cx.tcx.get_attrs(variant_def.def_id);
1024 clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs)
1027 #[allow(clippy::too_many_lines)]
1028 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
1029 let ty = cx.typeck_results().expr_ty(ex).peel_refs();
1030 let adt_def = match ty.kind() {
1032 if adt_def.is_enum()
1033 && !(is_type_diagnostic_item(cx, ty, sym::Option) || is_type_diagnostic_item(cx, ty, sym::Result)) =>
1040 // First pass - check for violation, but don't do much book-keeping because this is hopefully
1041 // the uncommon case, and the book-keeping is slightly expensive.
1042 let mut wildcard_span = None;
1043 let mut wildcard_ident = None;
1044 let mut has_non_wild = false;
1046 match peel_hir_pat_refs(arm.pat).0.kind {
1047 PatKind::Wild => wildcard_span = Some(arm.pat.span),
1048 PatKind::Binding(_, _, ident, None) => {
1049 wildcard_span = Some(arm.pat.span);
1050 wildcard_ident = Some(ident);
1052 _ => has_non_wild = true,
1055 let wildcard_span = match wildcard_span {
1056 Some(x) if has_non_wild => x,
1060 // Accumulate the variants which should be put in place of the wildcard because they're not
1062 let has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x));
1063 let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect();
1065 let mut path_prefix = CommonPrefixSearcher::None;
1067 // Guards mean that this case probably isn't exhaustively covered. Technically
1068 // this is incorrect, as we should really check whether each variant is exhaustively
1069 // covered by the set of guards that cover it, but that's really hard to do.
1070 recurse_or_patterns(arm.pat, |pat| {
1071 let path = match &peel_hir_pat_refs(pat).0.kind {
1072 PatKind::Path(path) => {
1073 #[allow(clippy::match_same_arms)]
1074 let id = match cx.qpath_res(path, pat.hir_id) {
1076 DefKind::Const | DefKind::ConstParam | DefKind::AnonConst | DefKind::InlineConst,
1079 Res::Def(_, id) => id,
1082 if arm.guard.is_none() {
1083 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1087 PatKind::TupleStruct(path, patterns, ..) => {
1088 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1089 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) {
1090 missing_variants.retain(|e| e.ctor_def_id != Some(id));
1095 PatKind::Struct(path, patterns, ..) => {
1096 if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() {
1097 if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) {
1098 missing_variants.retain(|e| e.def_id != id);
1106 QPath::Resolved(_, path) => path_prefix.with_path(path.segments),
1107 QPath::TypeRelative(
1109 kind: TyKind::Path(QPath::Resolved(_, path)),
1113 ) => path_prefix.with_prefix(path.segments),
1119 let format_suggestion = |variant: &VariantDef| {
1122 if let Some(ident) = wildcard_ident {
1123 format!("{} @ ", ident.name)
1127 if let CommonPrefixSearcher::Path(path_prefix) = path_prefix {
1128 let mut s = String::new();
1129 for seg in path_prefix {
1130 s.push_str(&seg.ident.as_str());
1135 let mut s = cx.tcx.def_path_str(adt_def.did);
1140 match variant.ctor_kind {
1141 CtorKind::Fn if variant.fields.len() == 1 => "(_)",
1142 CtorKind::Fn => "(..)",
1143 CtorKind::Const => "",
1144 CtorKind::Fictive => "{ .. }",
1149 match missing_variants.as_slice() {
1151 [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg(
1153 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
1155 "wildcard matches only a single variant and will also match any future added variants",
1157 format_suggestion(x),
1158 Applicability::MaybeIncorrect,
1161 let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect();
1162 let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden {
1163 suggestions.push("_".into());
1164 "wildcard matches known variants and will also match future added variants"
1166 "wildcard match will also match any future added variants"
1171 WILDCARD_ENUM_MATCH_ARM,
1175 suggestions.join(" | "),
1176 Applicability::MaybeIncorrect,
1182 // If the block contains only a `panic!` macro (as expression or statement)
1183 fn is_panic_call(expr: &Expr<'_>) -> bool {
1184 // Unwrap any wrapping blocks
1185 let span = if let ExprKind::Block(block, _) = expr.kind {
1186 match (&block.expr, block.stmts.len(), block.stmts.first()) {
1187 (&Some(exp), 0, _) => exp.span,
1188 (&None, 1, Some(stmt)) => stmt.span,
1195 is_expn_of(span, "panic").is_some() && is_expn_of(span, "unreachable").is_none()
1198 fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>)
1201 I: Clone + Iterator<Item = &'a Pat<'b>>,
1203 if !has_multiple_ref_pats(pats.clone()) {
1207 let (first_sugg, msg, title);
1208 let span = ex.span.source_callsite();
1209 if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = ex.kind {
1210 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1212 title = "you don't need to add `&` to both the expression and the patterns";
1214 first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1215 msg = "instead of prefixing all patterns with `&`, you can dereference the expression";
1216 title = "you don't need to add `&` to all patterns";
1219 let remaining_suggs = pats.filter_map(|pat| {
1220 if let PatKind::Ref(refp, _) = pat.kind {
1221 Some((pat.span, snippet(cx, refp.span, "..").to_string()))
1227 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1228 if !expr.span.from_expansion() {
1229 multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs));
1234 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1235 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1236 let arm_ref: Option<BindingAnnotation> = if is_none_arm(cx, &arms[0]) {
1237 is_ref_some_arm(cx, &arms[1])
1238 } else if is_none_arm(cx, &arms[1]) {
1239 is_ref_some_arm(cx, &arms[0])
1243 if let Some(rb) = arm_ref {
1244 let suggestion = if rb == BindingAnnotation::Ref {
1250 let output_ty = cx.typeck_results().expr_ty(expr);
1251 let input_ty = cx.typeck_results().expr_ty(ex);
1253 let cast = if_chain! {
1254 if let ty::Adt(_, substs) = input_ty.kind();
1255 let input_ty = substs.type_at(0);
1256 if let ty::Adt(_, substs) = output_ty.kind();
1257 let output_ty = substs.type_at(0);
1258 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1259 if input_ty != output_ty;
1267 let mut applicability = Applicability::MachineApplicable;
1272 &format!("use `{}()` instead", suggestion),
1276 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1286 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1288 if let PatKind::Or(fields) = arm.pat.kind {
1289 // look for multiple fields in this arm that contains at least one Wild pattern
1290 if fields.len() > 1 && fields.iter().any(is_wild) {
1293 WILDCARD_IN_OR_PATTERNS,
1295 "wildcard pattern covers any other pattern as it will match anyway",
1297 "consider handling `_` separately",
1304 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1305 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1306 if let Some(higher::IfLet {
1310 if_else: Some(if_else),
1311 }) = higher::IfLet::hir(cx, expr)
1313 return find_matches_sugg(
1316 IntoIterator::into_iter([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]),
1322 if let ExprKind::Match(scrut, arms, MatchSource::Normal) = expr.kind {
1323 return find_matches_sugg(
1326 arms.iter().map(|arm| {
1328 cx.tcx.hir().attrs(arm.hir_id),
1342 /// Lint a `match` or `if let` for replacement by `matches!`
1343 fn find_matches_sugg<'a, 'b, I>(
1344 cx: &LateContext<'_>,
1353 + DoubleEndedIterator
1358 Option<&'a Pat<'b>>,
1360 Option<&'a Guard<'b>>,
1366 if cx.typeck_results().expr_ty(expr).is_bool();
1367 if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back();
1368 let iter_without_last = iter.clone();
1369 if let Some((first_attrs, _, first_expr, first_guard)) = iter.next();
1370 if let Some(b0) = find_bool_lit(&first_expr.kind, is_if_let);
1371 if let Some(b1) = find_bool_lit(&last_expr.kind, is_if_let);
1373 if first_guard.is_none() || iter.len() == 0;
1374 if first_attrs.is_empty();
1377 find_bool_lit(&arm.2.kind, is_if_let).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty()
1380 if let Some(last_pat) = last_pat_opt {
1381 if !is_wild(last_pat) {
1386 // The suggestion may be incorrect, because some arms can have `cfg` attributes
1387 // evaluated into `false` and so such arms will be stripped before.
1388 let mut applicability = Applicability::MaybeIncorrect;
1390 use itertools::Itertools as _;
1393 let pat_span = arm.1?.span;
1394 Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability))
1398 let pat_and_guard = if let Some(Guard::If(g)) = first_guard {
1399 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1404 // strip potential borrows (#6503), but only if the type is a reference
1405 let mut ex_new = ex;
1406 if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
1407 if let ty::Ref(..) = cx.typeck_results().expr_ty(ex_inner).kind() {
1413 MATCH_LIKE_MATCHES_MACRO,
1415 &format!("{} expression looks like `matches!` macro", if is_if_let { "if let .. else" } else { "match" }),
1418 "{}matches!({}, {})",
1419 if b0 { "" } else { "!" },
1420 snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
1432 /// Extract a `bool` or `{ bool }`
1433 fn find_bool_lit(ex: &ExprKind<'_>, is_if_let: bool) -> Option<bool> {
1435 ExprKind::Lit(Spanned {
1436 node: LitKind::Bool(b), ..
1446 if let ExprKind::Lit(Spanned {
1447 node: LitKind::Bool(b), ..
1459 #[allow(clippy::too_many_lines)]
1460 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1461 if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1466 // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
1467 // to prevent false positives as there is currently no better way to detect if code was excluded by
1468 // a macro. See PR #6435
1470 if let Some(match_snippet) = snippet_opt(cx, expr.span);
1471 if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
1472 if let Some(ex_snippet) = snippet_opt(cx, ex.span);
1473 let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
1474 if rest_snippet.contains("=>");
1476 // The code it self contains another thick arrow "=>"
1477 // -> Either another arm or a comment
1482 let matched_vars = ex.span;
1483 let bind_names = arms[0].pat.span;
1484 let match_body = remove_blocks(arms[0].body);
1485 let mut snippet_body = if match_body.span.from_expansion() {
1486 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1488 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1491 // Do we need to add ';' to suggestion ?
1492 match match_body.kind {
1493 ExprKind::Block(block, _) => {
1494 // macro + expr_ty(body) == ()
1495 if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
1496 snippet_body.push(';');
1500 // expr_ty(body) == ()
1501 if cx.typeck_results().expr_ty(match_body).is_unit() {
1502 snippet_body.push(';');
1507 let mut applicability = Applicability::MaybeIncorrect;
1508 match arms[0].pat.kind {
1509 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1510 // If this match is in a local (`let`) stmt
1511 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1513 parent_let_node.span,
1515 "let {} = {};\n{}let {} = {};",
1516 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1517 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1518 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1519 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1524 // If we are in closure, we need curly braces around suggestion
1525 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1526 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1527 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1528 if let ExprKind::Closure(..) = parent_expr.kind {
1529 cbrace_end = format!("\n{}}}", indent);
1530 // Fix body indent due to the closure
1531 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1532 cbrace_start = format!("{{\n{}", indent);
1535 // If the parent is already an arm, and the body is another match statement,
1536 // we need curly braces around suggestion
1537 let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
1538 if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
1539 if let ExprKind::Match(..) = arm.body.kind {
1540 cbrace_end = format!("\n{}}}", indent);
1541 // Fix body indent due to the match
1542 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1543 cbrace_start = format!("{{\n{}", indent);
1549 "{}let {} = {};\n{}{}{}",
1551 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1552 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1561 MATCH_SINGLE_BINDING,
1563 "this match could be written as a `let` statement",
1564 "consider using `let` statement",
1570 if ex.can_have_side_effects() {
1571 let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
1574 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1580 MATCH_SINGLE_BINDING,
1582 "this match could be replaced by its scrutinee and body",
1583 "consider using the scrutinee and body instead",
1590 MATCH_SINGLE_BINDING,
1592 "this match could be replaced by its body itself",
1593 "consider using the match body instead",
1595 Applicability::MachineApplicable,
1603 /// Returns true if the `ex` match expression is in a local (`let`) statement
1604 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1605 let map = &cx.tcx.hir();
1607 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1608 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1610 return Some(parent_let_expr);
1616 /// Gets the ranges for each range pattern arm. Applies `ty` bounds for open ranges.
1617 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<FullInt>> {
1620 if let Arm { pat, guard: None, .. } = *arm {
1621 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1622 let lhs_const = match lhs {
1623 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1624 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1626 let rhs_const = match rhs {
1627 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1628 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1631 let lhs_val = lhs_const.int_value(cx, ty)?;
1632 let rhs_val = rhs_const.int_value(cx, ty)?;
1634 let rhs_bound = match range_end {
1635 RangeEnd::Included => EndBound::Included(rhs_val),
1636 RangeEnd::Excluded => EndBound::Excluded(rhs_val),
1638 return Some(SpannedRange {
1640 node: (lhs_val, rhs_bound),
1644 if let PatKind::Lit(value) = pat.kind {
1645 let value = constant_full_int(cx, cx.typeck_results(), value)?;
1646 return Some(SpannedRange {
1648 node: (value, EndBound::Included(value)),
1657 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
1658 pub enum EndBound<T> {
1663 #[derive(Debug, Eq, PartialEq)]
1664 struct SpannedRange<T> {
1666 pub node: (T, EndBound<T>),
1669 // Checks if arm has the form `None => None`
1670 fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
1671 matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone))
1674 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1675 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
1677 if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
1678 if is_lang_ctor(cx, qpath, OptionSome);
1679 if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
1680 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1681 if let ExprKind::Call(e, args) = remove_blocks(arm.body).kind;
1682 if let ExprKind::Path(ref some_path) = e.kind;
1683 if is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1;
1684 if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind;
1685 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1693 fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
1696 I: Iterator<Item = &'a Pat<'b>>,
1698 let mut ref_count = 0;
1699 for opt in pats.map(|pat| match pat.kind {
1700 PatKind::Ref(..) => Some(true), // &-patterns
1701 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1702 _ => None, // any other pattern is not fine
1704 if let Some(inner) = opt {
1715 fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1719 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
1726 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1727 struct RangeBound<'a, T>(T, BoundKind, &'a SpannedRange<T>);
1729 impl<'a, T: Copy + Ord> PartialOrd for RangeBound<'a, T> {
1730 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1731 Some(self.cmp(other))
1735 impl<'a, T: Copy + Ord> Ord for RangeBound<'a, T> {
1736 fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
1737 let RangeBound(self_value, self_kind, _) = *self;
1738 (self_value, self_kind).cmp(&(*other_value, *other_kind))
1742 let mut values = Vec::with_capacity(2 * ranges.len());
1744 for r @ SpannedRange { node: (start, end), .. } in ranges {
1745 values.push(RangeBound(*start, BoundKind::Start, r));
1746 values.push(match end {
1747 EndBound::Excluded(val) => RangeBound(*val, BoundKind::EndExcluded, r),
1748 EndBound::Included(val) => RangeBound(*val, BoundKind::EndIncluded, r),
1754 let mut started = vec![];
1756 for RangeBound(_, kind, range) in values {
1758 BoundKind::Start => started.push(range),
1759 BoundKind::EndExcluded | BoundKind::EndIncluded => {
1760 let mut overlap = None;
1762 while let Some(last_started) = started.pop() {
1763 if last_started == range {
1766 overlap = Some(last_started);
1769 if let Some(first_overlapping) = overlap {
1770 return Some((range, first_overlapping));
1779 mod redundant_pattern_match {
1780 use super::REDUNDANT_PATTERN_MATCHING;
1781 use clippy_utils::diagnostics::span_lint_and_then;
1782 use clippy_utils::higher;
1783 use clippy_utils::source::snippet;
1784 use clippy_utils::sugg::Sugg;
1785 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
1786 use clippy_utils::{is_lang_ctor, is_qpath_def_path, is_trait_method, paths};
1787 use if_chain::if_chain;
1788 use rustc_ast::ast::LitKind;
1789 use rustc_data_structures::fx::FxHashSet;
1790 use rustc_errors::Applicability;
1791 use rustc_hir::LangItem::{OptionNone, OptionSome, PollPending, PollReady, ResultErr, ResultOk};
1793 intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
1794 Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
1796 use rustc_lint::LateContext;
1797 use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
1798 use rustc_span::sym;
1800 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1801 if let Some(higher::IfLet {
1806 }) = higher::IfLet::hir(cx, expr)
1808 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
1810 if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
1811 find_sugg_for_match(cx, expr, op, arms);
1813 if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
1814 find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
1818 /// Checks if the drop order for a type matters. Some std types implement drop solely to
1819 /// deallocate memory. For these types, and composites containing them, changing the drop order
1820 /// won't result in any observable side effects.
1821 fn type_needs_ordered_drop(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
1822 type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
1825 fn type_needs_ordered_drop_inner(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
1826 if !seen.insert(ty) {
1829 if !ty.needs_drop(cx.tcx, cx.param_env) {
1835 .map_or(false, |id| implements_trait(cx, ty, id, &[]))
1837 // This type doesn't implement drop, so no side effects here.
1838 // Check if any component type has any.
1840 ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1841 ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
1842 ty::Adt(adt, subs) => adt
1844 .map(|f| f.ty(cx.tcx, subs))
1845 .any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
1849 // Check for std types which implement drop, but only for memory allocation.
1850 else if is_type_diagnostic_item(cx, ty, sym::Vec)
1851 || is_type_lang_item(cx, ty, LangItem::OwnedBox)
1852 || is_type_diagnostic_item(cx, ty, sym::Rc)
1853 || is_type_diagnostic_item(cx, ty, sym::Arc)
1854 || is_type_diagnostic_item(cx, ty, sym::cstring_type)
1855 || is_type_diagnostic_item(cx, ty, sym::BTreeMap)
1856 || is_type_diagnostic_item(cx, ty, sym::LinkedList)
1857 || match_type(cx, ty, &paths::WEAK_RC)
1858 || match_type(cx, ty, &paths::WEAK_ARC)
1860 // Check all of the generic arguments.
1861 if let ty::Adt(_, subs) = ty.kind() {
1862 subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
1871 // Extract the generic arguments out of a type
1872 fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
1874 if let ty::Adt(_, subs) = ty.kind();
1875 if let Some(sub) = subs.get(index);
1876 if let GenericArgKind::Type(sub_ty) = sub.unpack();
1885 // Checks if there are any temporaries created in the given expression for which drop order
1887 fn temporaries_need_ordered_drop(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1888 struct V<'a, 'tcx> {
1889 cx: &'a LateContext<'tcx>,
1892 impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
1893 type Map = ErasedMap<'tcx>;
1894 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1895 NestedVisitorMap::None
1898 fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
1900 // Taking the reference of a value leaves a temporary
1901 // e.g. In `&String::new()` the string is a temporary value.
1902 // Remaining fields are temporary values
1903 // e.g. In `(String::new(), 0).1` the string is a temporary value.
1904 ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
1905 if !matches!(expr.kind, ExprKind::Path(_)) {
1906 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
1909 self.visit_expr(expr);
1913 // the base type is alway taken by reference.
1914 // e.g. In `(vec![0])[0]` the vector is a temporary value.
1915 ExprKind::Index(base, index) => {
1916 if !matches!(base.kind, ExprKind::Path(_)) {
1917 if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
1920 self.visit_expr(base);
1923 self.visit_expr(index);
1925 // Method calls can take self by reference.
1926 // e.g. In `String::new().len()` the string is a temporary value.
1927 ExprKind::MethodCall(_, _, [self_arg, args @ ..], _) => {
1928 if !matches!(self_arg.kind, ExprKind::Path(_)) {
1929 let self_by_ref = self
1932 .type_dependent_def_id(expr.hir_id)
1933 .map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
1935 && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg))
1939 self.visit_expr(self_arg);
1942 args.iter().for_each(|arg| self.visit_expr(arg));
1944 // Either explicitly drops values, or changes control flow.
1945 ExprKind::DropTemps(_)
1947 | ExprKind::Break(..)
1948 | ExprKind::Yield(..)
1949 | ExprKind::Block(Block { expr: None, .. }, _)
1950 | ExprKind::Loop(..) => (),
1952 // Only consider the final expression.
1953 ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
1955 _ => walk_expr(self, expr),
1960 let mut v = V { cx, res: false };
1965 fn find_sugg_for_if_let<'tcx>(
1966 cx: &LateContext<'tcx>,
1967 expr: &'tcx Expr<'_>,
1969 let_expr: &'tcx Expr<'_>,
1970 keyword: &'static str,
1973 // also look inside refs
1974 let mut kind = &let_pat.kind;
1975 // if we have &None for example, peel it so we can detect "if let None = x"
1976 if let PatKind::Ref(inner, _mutability) = kind {
1979 let op_ty = cx.typeck_results().expr_ty(let_expr);
1980 // Determine which function should be used, and the type contained by the corresponding
1982 let (good_method, inner_ty) = match kind {
1983 PatKind::TupleStruct(ref path, [sub_pat], _) => {
1984 if let PatKind::Wild = sub_pat.kind {
1985 if is_lang_ctor(cx, path, ResultOk) {
1986 ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
1987 } else if is_lang_ctor(cx, path, ResultErr) {
1988 ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
1989 } else if is_lang_ctor(cx, path, OptionSome) {
1990 ("is_some()", op_ty)
1991 } else if is_lang_ctor(cx, path, PollReady) {
1992 ("is_ready()", op_ty)
1993 } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V4) {
1994 ("is_ipv4()", op_ty)
1995 } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V6) {
1996 ("is_ipv6()", op_ty)
2004 PatKind::Path(ref path) => {
2005 let method = if is_lang_ctor(cx, path, OptionNone) {
2007 } else if is_lang_ctor(cx, path, PollPending) {
2012 // `None` and `Pending` don't have an inner type.
2013 (method, cx.tcx.types.unit)
2018 // If this is the last expression in a block or there is an else clause then the whole
2019 // type needs to be considered, not just the inner type of the branch being matched on.
2020 // Note the last expression in a block is dropped after all local bindings.
2021 let check_ty = if has_else
2022 || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
2029 // All temporaries created in the scrutinee expression are dropped at the same time as the
2030 // scrutinee would be, so they have to be considered as well.
2031 // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
2032 // for the duration if body.
2033 let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
2035 // check that `while_let_on_iterator` lint does not trigger
2037 if keyword == "while";
2038 if let ExprKind::MethodCall(method_path, _, _, _) = let_expr.kind;
2039 if method_path.ident.name == sym::next;
2040 if is_trait_method(cx, let_expr, sym::Iterator);
2046 let result_expr = match &let_expr.kind {
2047 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2048 ExprKind::Unary(UnOp::Deref, deref) => deref,
2054 REDUNDANT_PATTERN_MATCHING,
2056 &format!("redundant pattern matching, consider using `{}`", good_method),
2058 // if/while let ... = ... { ... }
2059 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2060 let expr_span = expr.span;
2062 // if/while let ... = ... { ... }
2064 let op_span = result_expr.span.source_callsite();
2066 // if/while let ... = ... { ... }
2067 // ^^^^^^^^^^^^^^^^^^^
2068 let span = expr_span.until(op_span.shrink_to_hi());
2070 let app = if needs_drop {
2071 Applicability::MaybeIncorrect
2073 Applicability::MachineApplicable
2076 let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
2080 diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
2083 diag.note("this will change drop order of the result, as well as all temporaries");
2084 diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
2090 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
2091 if arms.len() == 2 {
2092 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
2094 let found_good_method = match node_pair {
2096 PatKind::TupleStruct(ref path_left, patterns_left, _),
2097 PatKind::TupleStruct(ref path_right, patterns_right, _),
2098 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
2099 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
2100 find_good_method_for_match(
2111 find_good_method_for_match(
2126 (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
2127 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
2128 if patterns.len() == 1 =>
2130 if let PatKind::Wild = patterns[0].kind {
2131 find_good_method_for_match(
2136 &paths::OPTION_SOME,
2137 &paths::OPTION_NONE,
2142 find_good_method_for_match(
2148 &paths::POLL_PENDING,
2160 if let Some(good_method) = found_good_method {
2161 let span = expr.span.to(op.span);
2162 let result_expr = match &op.kind {
2163 ExprKind::AddrOf(_, _, borrowed) => borrowed,
2168 REDUNDANT_PATTERN_MATCHING,
2170 &format!("redundant pattern matching, consider using `{}`", good_method),
2172 diag.span_suggestion(
2175 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
2176 Applicability::MaybeIncorrect, // snippet
2184 #[allow(clippy::too_many_arguments)]
2185 fn find_good_method_for_match<'a>(
2186 cx: &LateContext<'_>,
2188 path_left: &QPath<'_>,
2189 path_right: &QPath<'_>,
2190 expected_left: &[&str],
2191 expected_right: &[&str],
2192 should_be_left: &'a str,
2193 should_be_right: &'a str,
2194 ) -> Option<&'a str> {
2195 let body_node_pair = if is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, expected_left)
2196 && is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_right)
2198 (&(*arms[0].body).kind, &(*arms[1].body).kind)
2199 } else if is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_left)
2200 && is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, expected_right)
2202 (&(*arms[1].body).kind, &(*arms[0].body).kind)
2207 match body_node_pair {
2208 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
2209 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
2210 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
2219 fn test_overlapping() {
2220 use rustc_span::source_map::DUMMY_SP;
2222 let sp = |s, e| SpannedRange {
2227 assert_eq!(None, overlapping::<u8>(&[]));
2228 assert_eq!(None, overlapping(&[sp(1, EndBound::Included(4))]));
2231 overlapping(&[sp(1, EndBound::Included(4)), sp(5, EndBound::Included(6))])
2236 sp(1, EndBound::Included(4)),
2237 sp(5, EndBound::Included(6)),
2238 sp(10, EndBound::Included(11))
2242 Some((&sp(1, EndBound::Included(4)), &sp(3, EndBound::Included(6)))),
2243 overlapping(&[sp(1, EndBound::Included(4)), sp(3, EndBound::Included(6))])
2246 Some((&sp(5, EndBound::Included(6)), &sp(6, EndBound::Included(11)))),
2248 sp(1, EndBound::Included(4)),
2249 sp(5, EndBound::Included(6)),
2250 sp(6, EndBound::Included(11))
2255 /// Implementation of `MATCH_SAME_ARMS`.
2256 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
2257 if let ExprKind::Match(_, arms, MatchSource::Normal) = expr.kind {
2258 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
2259 let mut h = SpanlessHash::new(cx);
2260 h.hash_expr(arm.body);
2264 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
2265 let min_index = usize::min(lindex, rindex);
2266 let max_index = usize::max(lindex, rindex);
2268 let mut local_map: HirIdMap<HirId> = HirIdMap::default();
2269 let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
2271 if let Some(a_id) = path_to_local(a);
2272 if let Some(b_id) = path_to_local(b);
2273 let entry = match local_map.entry(a_id) {
2274 Entry::Vacant(entry) => entry,
2275 // check if using the same bindings as before
2276 Entry::Occupied(entry) => return *entry.get() == b_id,
2278 // the names technically don't have to match; this makes the lint more conservative
2279 if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id);
2280 if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b));
2281 if pat_contains_local(lhs.pat, a_id);
2282 if pat_contains_local(rhs.pat, b_id);
2291 // Arms with a guard are ignored, those can’t always be merged together
2292 // This is also the case for arms in-between each there is an arm with a guard
2293 (min_index..=max_index).all(|index| arms[index].guard.is_none())
2294 && SpanlessEq::new(cx)
2295 .expr_fallback(eq_fallback)
2296 .eq_expr(lhs.body, rhs.body)
2297 // these checks could be removed to allow unused bindings
2298 && bindings_eq(lhs.pat, local_map.keys().copied().collect())
2299 && bindings_eq(rhs.pat, local_map.values().copied().collect())
2302 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
2303 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
2308 "this `match` has identical arm bodies",
2310 diag.span_note(i.body.span, "same as this");
2312 // Note: this does not use `span_suggestion` on purpose:
2313 // there is no clean way
2314 // to remove the other arm. Building a span and suggest to replace it to ""
2315 // makes an even more confusing error message. Also in order not to make up a
2316 // span for the whole pattern, the suggestion is only shown when there is only
2317 // one pattern. The user should know about `|` if they are already using it…
2319 let lhs = snippet(cx, i.pat.span, "<pat1>");
2320 let rhs = snippet(cx, j.pat.span, "<pat2>");
2322 if let PatKind::Wild = j.pat.kind {
2323 // if the last arm is _, then i could be integrated into _
2324 // note that i.pat cannot be _, because that would mean that we're
2325 // hiding all the subsequent arms, and rust won't compile
2329 "`{}` has the same arm body as the `_` wildcard, consider removing it",
2334 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
2335 .help("...or consider changing the match arm bodies");
2343 fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool {
2344 let mut result = false;
2345 pat.walk_short(|p| {
2346 result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id);
2352 /// Returns true if all the bindings in the `Pat` are in `ids` and vice versa
2353 fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool {
2354 let mut result = true;
2355 pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
2356 result && ids.is_empty()