1 use crate::consts::{constant, miri_to_const, Constant};
2 use crate::utils::sugg::Sugg;
3 use crate::utils::usage::is_unused;
5 expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable,
6 is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, multispan_sugg, remove_blocks, snippet,
7 snippet_block, snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
10 use crate::utils::{paths, search_same, SpanlessEq, SpanlessHash};
11 use if_chain::if_chain;
12 use rustc_ast::ast::LitKind;
13 use rustc_data_structures::fx::FxHashMap;
14 use rustc_errors::Applicability;
15 use rustc_hir::def::CtorKind;
17 Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, Local, MatchSource, Mutability, Node, Pat,
18 PatKind, QPath, RangeEnd,
20 use rustc_lint::{LateContext, LateLintPass, LintContext};
21 use rustc_middle::lint::in_external_macro;
22 use rustc_middle::ty::{self, Ty, TyS};
23 use rustc_session::{declare_tool_lint, impl_lint_pass};
24 use rustc_span::source_map::{Span, Spanned};
25 use rustc_span::{sym, Symbol};
26 use std::cmp::Ordering;
27 use std::collections::hash_map::Entry;
28 use std::collections::Bound;
30 declare_clippy_lint! {
31 /// **What it does:** Checks for matches with a single arm where an `if let`
32 /// will usually suffice.
34 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
36 /// **Known problems:** None.
40 /// # fn bar(stool: &str) {}
41 /// # let x = Some("abc");
44 /// Some(ref foo) => bar(foo),
49 /// if let Some(ref foo) = x {
55 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
58 declare_clippy_lint! {
59 /// **What it does:** Checks for matches with two arms where an `if let else` will
62 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
64 /// **Known problems:** Personal style preferences may differ.
71 /// # fn bar(foo: &usize) {}
72 /// # let other_ref: usize = 1;
73 /// # let x: Option<&usize> = Some(&1);
75 /// Some(ref foo) => bar(foo),
76 /// _ => bar(&other_ref),
80 /// Using `if let` with `else`:
83 /// # fn bar(foo: &usize) {}
84 /// # let other_ref: usize = 1;
85 /// # let x: Option<&usize> = Some(&1);
86 /// if let Some(ref foo) = x {
92 pub SINGLE_MATCH_ELSE,
94 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
97 declare_clippy_lint! {
98 /// **What it does:** Checks for matches where all arms match a reference,
99 /// suggesting to remove the reference and deref the matched expression
100 /// instead. It also checks for `if let &foo = bar` blocks.
102 /// **Why is this bad?** It just makes the code less readable. That reference
103 /// destructuring adds nothing to the code.
105 /// **Known problems:** None.
111 /// &A(ref y) => foo(y),
118 /// A(ref y) => foo(y),
125 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
128 declare_clippy_lint! {
129 /// **What it does:** Checks for matches where match expression is a `bool`. It
130 /// suggests to replace the expression with an `if...else` block.
132 /// **Why is this bad?** It makes the code less readable.
134 /// **Known problems:** None.
140 /// let condition: bool = true;
141 /// match condition {
146 /// Use if/else instead:
150 /// let condition: bool = true;
159 "a `match` on a boolean expression instead of an `if..else` block"
162 declare_clippy_lint! {
163 /// **What it does:** Checks for overlapping match arms.
165 /// **Why is this bad?** It is likely to be an error and if not, makes the code
168 /// **Known problems:** None.
174 /// 1...10 => println!("1 ... 10"),
175 /// 5...15 => println!("5 ... 15"),
179 pub MATCH_OVERLAPPING_ARM,
181 "a `match` with overlapping arms"
184 declare_clippy_lint! {
185 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
186 /// and take drastic actions like `panic!`.
188 /// **Why is this bad?** It is generally a bad practice, similar to
189 /// catching all exceptions in java with `catch(Exception)`
191 /// **Known problems:** None.
195 /// let x: Result<i32, &str> = Ok(3);
197 /// Ok(_) => println!("ok"),
198 /// Err(_) => panic!("err"),
201 pub MATCH_WILD_ERR_ARM,
203 "a `match` with `Err(_)` arm and take drastic actions"
206 declare_clippy_lint! {
207 /// **What it does:** Checks for match which is used to add a reference to an
210 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
212 /// **Known problems:** None.
216 /// let x: Option<()> = None;
219 /// let r: Option<&()> = match x {
221 /// Some(ref v) => Some(v),
225 /// let r: Option<&()> = x.as_ref();
229 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
232 declare_clippy_lint! {
233 /// **What it does:** Checks for wildcard enum matches using `_`.
235 /// **Why is this bad?** New enum variants added by library updates can be missed.
237 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
238 /// variants, and also may not use correct path to enum if it's not present in the current scope.
242 /// # enum Foo { A(usize), B(usize) }
243 /// # let x = Foo::B(1);
256 pub WILDCARD_ENUM_MATCH_ARM,
258 "a wildcard enum match arm using `_`"
261 declare_clippy_lint! {
262 /// **What it does:** Checks for wildcard enum matches for a single variant.
264 /// **Why is this bad?** New enum variants added by library updates can be missed.
266 /// **Known problems:** Suggested replacements may not use correct path to enum
267 /// if it's not present in the current scope.
272 /// # enum Foo { A, B, C }
273 /// # let x = Foo::B;
288 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
290 "a wildcard enum match for a single variant"
293 declare_clippy_lint! {
294 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
296 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
297 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
299 /// **Known problems:** None.
315 pub WILDCARD_IN_OR_PATTERNS,
317 "a wildcard pattern used with others patterns in same match arm"
320 declare_clippy_lint! {
321 /// **What it does:** Checks for matches being used to destructure a single-variant enum
322 /// or tuple struct where a `let` will suffice.
324 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
326 /// **Known problems:** None.
334 /// let wrapper = Wrapper::Data(42);
336 /// let data = match wrapper {
337 /// Wrapper::Data(i) => i,
341 /// The correct use would be:
347 /// let wrapper = Wrapper::Data(42);
348 /// let Wrapper::Data(data) = wrapper;
350 pub INFALLIBLE_DESTRUCTURING_MATCH,
352 "a `match` statement with a single infallible arm instead of a `let`"
355 declare_clippy_lint! {
356 /// **What it does:** Checks for useless match that binds to only one value.
358 /// **Why is this bad?** Readability and needless complexity.
360 /// **Known problems:** Suggested replacements may be incorrect when `match`
361 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
376 /// let (c, d) = (a, b);
378 pub MATCH_SINGLE_BINDING,
380 "a match with a single binding instead of using `let` statement"
383 declare_clippy_lint! {
384 /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
386 /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after
387 /// matching all enum variants explicitly.
389 /// **Known problems:** None.
393 /// # struct A { a: i32 }
394 /// let a = A { a: 5 };
398 /// A { a: 5, .. } => {},
404 /// A { a: 5 } => {},
408 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
410 "a match on a struct that binds all fields but still uses the wildcard pattern"
413 declare_clippy_lint! {
414 /// **What it does:** Lint for redundant pattern matching over `Result` or
417 /// **Why is this bad?** It's more concise and clear to just use the proper
420 /// **Known problems:** None.
425 /// if let Ok(_) = Ok::<i32, i32>(42) {}
426 /// if let Err(_) = Err::<i32, i32>(42) {}
427 /// if let None = None::<()> {}
428 /// if let Some(_) = Some(42) {}
429 /// match Ok::<i32, i32>(42) {
435 /// The more idiomatic use would be:
438 /// if Ok::<i32, i32>(42).is_ok() {}
439 /// if Err::<i32, i32>(42).is_err() {}
440 /// if None::<()>.is_none() {}
441 /// if Some(42).is_some() {}
442 /// Ok::<i32, i32>(42).is_ok();
444 pub REDUNDANT_PATTERN_MATCHING,
446 "use the proper utility function avoiding an `if let`"
449 declare_clippy_lint! {
450 /// **What it does:** Checks for `match` or `if let` expressions producing a
451 /// `bool` that could be written using `matches!`
453 /// **Why is this bad?** Readability and needless complexity.
455 /// **Known problems:** None
462 /// let a = match x {
467 /// let a = if let Some(0) = x {
474 /// let a = matches!(x, Some(0));
476 pub MATCH_LIKE_MATCHES_MACRO,
478 "a match that could be written with the matches! macro"
481 declare_clippy_lint! {
482 /// **What it does:** Checks for `match` with identical arm bodies.
484 /// **Why is this bad?** This is probably a copy & paste error. If arm bodies
485 /// are the same on purpose, you can factor them
486 /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
488 /// **Known problems:** False positive possible with order dependent `match`
490 /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
497 /// Baz => bar(), // <= oops
501 /// This should probably be
506 /// Baz => baz(), // <= fixed
510 /// or if the original code was not a typo:
513 /// Bar | Baz => bar(), // <= shows the intent better
519 "`match` with identical arm bodies"
524 infallible_destructuring_match_linted: bool,
527 impl_lint_pass!(Matches => [
532 MATCH_OVERLAPPING_ARM,
535 WILDCARD_ENUM_MATCH_ARM,
536 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
537 WILDCARD_IN_OR_PATTERNS,
538 MATCH_SINGLE_BINDING,
539 INFALLIBLE_DESTRUCTURING_MATCH,
540 REST_PAT_IN_FULLY_BOUND_STRUCTS,
541 REDUNDANT_PATTERN_MATCHING,
542 MATCH_LIKE_MATCHES_MACRO,
546 impl<'tcx> LateLintPass<'tcx> for Matches {
547 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
548 if in_external_macro(cx.sess(), expr.span) || in_macro(expr.span) {
552 redundant_pattern_match::check(cx, expr);
553 if !check_match_like_matches(cx, expr) {
554 lint_match_arms(cx, expr);
557 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
558 check_single_match(cx, ex, arms, expr);
559 check_match_bool(cx, ex, arms, expr);
560 check_overlapping_arms(cx, ex, arms);
561 check_wild_err_arm(cx, ex, arms);
562 check_wild_enum_match(cx, ex, arms);
563 check_match_as_ref(cx, ex, arms, expr);
564 check_wild_in_or_pats(cx, arms);
566 if self.infallible_destructuring_match_linted {
567 self.infallible_destructuring_match_linted = false;
569 check_match_single_binding(cx, ex, arms, expr);
572 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
573 check_match_ref_pats(cx, ex, arms, expr);
577 fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
579 if !in_external_macro(cx.sess(), local.span);
580 if !in_macro(local.span);
581 if let Some(ref expr) = local.init;
582 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
583 if arms.len() == 1 && arms[0].guard.is_none();
584 if let PatKind::TupleStruct(
585 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
587 if let Some(arg) = get_arg_name(&args[0]);
588 let body = remove_blocks(&arms[0].body);
589 if match_var(body, arg);
592 let mut applicability = Applicability::MachineApplicable;
593 self.infallible_destructuring_match_linted = true;
596 INFALLIBLE_DESTRUCTURING_MATCH,
598 "you seem to be trying to use `match` to destructure a single infallible pattern. \
599 Consider using `let`",
603 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
604 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
605 snippet_with_applicability(cx, target.span, "..", &mut applicability),
613 fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
615 if !in_external_macro(cx.sess(), pat.span);
616 if !in_macro(pat.span);
617 if let PatKind::Struct(ref qpath, fields, true) = pat.kind;
618 if let QPath::Resolved(_, ref path) = qpath;
619 if let Some(def_id) = path.res.opt_def_id();
620 let ty = cx.tcx.type_of(def_id);
621 if let ty::Adt(def, _) = ty.kind();
622 if def.is_struct() || def.is_union();
623 if fields.len() == def.non_enum_variant().fields.len();
628 REST_PAT_IN_FULLY_BOUND_STRUCTS,
630 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
632 "consider removing `..` from this binding",
640 fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
641 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
642 if in_macro(expr.span) {
643 // Don't lint match expressions present in
644 // macro_rules! block
647 if let PatKind::Or(..) = arms[0].pat.kind {
648 // don't lint for or patterns for now, this makes
649 // the lint noisy in unnecessary situations
652 let els = arms[1].body;
653 let els = if is_unit_expr(remove_blocks(els)) {
655 } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind {
656 if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() {
657 // single statement/expr "else" block, don't lint
660 // block with 2+ statements or 1 expr and 1+ statement
664 // not a block, don't lint
668 let ty = cx.typeck_results().expr_ty(ex);
669 if *ty.kind() != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
670 check_single_match_single_pattern(cx, ex, arms, expr, els);
671 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
676 fn check_single_match_single_pattern(
677 cx: &LateContext<'_>,
681 els: Option<&Expr<'_>>,
683 if is_wild(&arms[1].pat) {
684 report_single_match_single_pattern(cx, ex, arms, expr, els);
688 fn report_single_match_single_pattern(
689 cx: &LateContext<'_>,
693 els: Option<&Expr<'_>>,
695 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
696 let els_str = els.map_or(String::new(), |els| {
697 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
703 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
707 "if let {} = {} {}{}",
708 snippet(cx, arms[0].pat.span, ".."),
709 snippet(cx, ex.span, ".."),
710 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
713 Applicability::HasPlaceholders,
717 fn check_single_match_opt_like(
718 cx: &LateContext<'_>,
723 els: Option<&Expr<'_>>,
725 // list of candidate `Enum`s we know will never get any more members
727 (&paths::COW, "Borrowed"),
728 (&paths::COW, "Cow::Borrowed"),
729 (&paths::COW, "Cow::Owned"),
730 (&paths::COW, "Owned"),
731 (&paths::OPTION, "None"),
732 (&paths::RESULT, "Err"),
733 (&paths::RESULT, "Ok"),
736 let path = match arms[1].pat.kind {
737 PatKind::TupleStruct(ref path, ref inner, _) => {
738 // Contains any non wildcard patterns (e.g., `Err(err)`)?
739 if !inner.iter().all(is_wild) {
742 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
744 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
745 PatKind::Path(ref path) => {
746 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
751 for &(ty_path, pat_path) in candidates {
752 if path == *pat_path && match_type(cx, ty, ty_path) {
753 report_single_match_single_pattern(cx, ex, arms, expr, els);
758 fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
759 // Type of expression is `bool`.
760 if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool {
765 "you seem to be trying to match on a boolean expression",
769 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
770 if let ExprKind::Lit(ref lit) = arm_bool.kind {
772 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
773 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
783 if let Some((true_expr, false_expr)) = exprs {
784 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
785 (false, false) => Some(format!(
787 snippet(cx, ex.span, "b"),
788 expr_block(cx, true_expr, None, "..", Some(expr.span)),
789 expr_block(cx, false_expr, None, "..", Some(expr.span))
791 (false, true) => Some(format!(
793 snippet(cx, ex.span, "b"),
794 expr_block(cx, true_expr, None, "..", Some(expr.span))
797 let test = Sugg::hir(cx, ex, "..");
801 expr_block(cx, false_expr, None, "..", Some(expr.span))
804 (true, true) => None,
807 if let Some(sugg) = sugg {
808 diag.span_suggestion(
810 "consider using an `if`/`else` expression",
812 Applicability::HasPlaceholders,
822 fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
823 if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() {
824 let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex));
825 let type_ranges = type_ranges(&ranges);
826 if !type_ranges.is_empty() {
827 if let Some((start, end)) = overlapping(&type_ranges) {
830 MATCH_OVERLAPPING_ARM,
832 "some ranges overlap",
834 "overlaps with this",
841 fn check_wild_err_arm(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
842 let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
843 if is_type_diagnostic_item(cx, ex_ty, sym::result_type) {
845 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
846 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
847 if path_str == "Err" {
848 let mut matching_wild = inner.iter().any(is_wild);
849 let mut ident_bind_name = String::from("_");
851 // Looking for unused bindings (i.e.: `_e`)
852 inner.iter().for_each(|pat| {
853 if let PatKind::Binding(.., ident, None) = &pat.kind {
854 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
855 ident_bind_name = (&ident.name.as_str()).to_string();
856 matching_wild = true;
863 if let ExprKind::Block(ref block, _) = arm.body.kind;
864 if is_panic_block(block);
866 // `Err(_)` or `Err(_e)` arm with `panic!` found
867 span_lint_and_note(cx,
870 &format!("`Err({})` matches all errors", &ident_bind_name),
872 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
882 fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
883 let ty = cx.typeck_results().expr_ty(ex);
885 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
886 // don't complain about not enumerating the mall.
890 // First pass - check for violation, but don't do much book-keeping because this is hopefully
891 // the uncommon case, and the book-keeping is slightly expensive.
892 let mut wildcard_span = None;
893 let mut wildcard_ident = None;
895 if let PatKind::Wild = arm.pat.kind {
896 wildcard_span = Some(arm.pat.span);
897 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
898 wildcard_span = Some(arm.pat.span);
899 wildcard_ident = Some(ident);
903 if let Some(wildcard_span) = wildcard_span {
904 // Accumulate the variants which should be put in place of the wildcard because they're not
907 let mut missing_variants = vec![];
908 if let ty::Adt(def, _) = ty.kind() {
909 for variant in &def.variants {
910 missing_variants.push(variant);
915 if arm.guard.is_some() {
916 // Guards mean that this case probably isn't exhaustively covered. Technically
917 // this is incorrect, as we should really check whether each variant is exhaustively
918 // covered by the set of guards that cover it, but that's really hard to do.
921 if let PatKind::Path(ref path) = arm.pat.kind {
922 if let QPath::Resolved(_, p) = path {
923 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
925 } else if let PatKind::TupleStruct(ref path, ref patterns, ..) = arm.pat.kind {
926 if let QPath::Resolved(_, p) = path {
927 // Some simple checks for exhaustive patterns.
928 // There is a room for improvements to detect more cases,
929 // but it can be more expensive to do so.
930 let is_pattern_exhaustive =
931 |pat: &&Pat<'_>| matches!(pat.kind, PatKind::Wild | PatKind::Binding(.., None));
932 if patterns.iter().all(is_pattern_exhaustive) {
933 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
939 let mut suggestion: Vec<String> = missing_variants
942 let suffix = match v.ctor_kind {
943 CtorKind::Fn => "(..)",
944 CtorKind::Const | CtorKind::Fictive => "",
946 let ident_str = if let Some(ident) = wildcard_ident {
947 format!("{} @ ", ident.name)
951 // This path assumes that the enum type is imported into scope.
952 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
956 if suggestion.is_empty() {
960 let mut message = "wildcard match will miss any future added variants";
962 if let ty::Adt(def, _) = ty.kind() {
963 if def.is_variant_list_non_exhaustive() {
964 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
965 suggestion.push(String::from("_"));
969 if suggestion.len() == 1 {
970 // No need to check for non-exhaustive enum as in that case len would be greater than 1
973 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
977 suggestion[0].clone(),
978 Applicability::MaybeIncorrect,
984 WILDCARD_ENUM_MATCH_ARM,
988 suggestion.join(" | "),
989 Applicability::MaybeIncorrect,
994 // If the block contains only a `panic!` macro (as expression or statement)
995 fn is_panic_block(block: &Block<'_>) -> bool {
996 match (&block.expr, block.stmts.len(), block.stmts.first()) {
997 (&Some(ref exp), 0, _) => {
998 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
1000 (&None, 1, Some(stmt)) => {
1001 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
1007 fn check_match_ref_pats(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1008 if has_only_ref_pats(arms) {
1009 let mut suggs = Vec::with_capacity(arms.len() + 1);
1010 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
1011 let span = ex.span.source_callsite();
1012 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
1014 "you don't need to add `&` to both the expression and the patterns",
1018 let span = ex.span.source_callsite();
1019 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
1021 "you don't need to add `&` to all patterns",
1022 "instead of prefixing all patterns with `&`, you can dereference the expression",
1026 suggs.extend(arms.iter().filter_map(|a| {
1027 if let PatKind::Ref(ref refp, _) = a.pat.kind {
1028 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
1034 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
1035 if !expr.span.from_expansion() {
1036 multispan_sugg(diag, msg, suggs);
1042 fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1043 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
1044 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
1045 is_ref_some_arm(&arms[1])
1046 } else if is_none_arm(&arms[1]) {
1047 is_ref_some_arm(&arms[0])
1051 if let Some(rb) = arm_ref {
1052 let suggestion = if rb == BindingAnnotation::Ref {
1058 let output_ty = cx.typeck_results().expr_ty(expr);
1059 let input_ty = cx.typeck_results().expr_ty(ex);
1061 let cast = if_chain! {
1062 if let ty::Adt(_, substs) = input_ty.kind();
1063 let input_ty = substs.type_at(0);
1064 if let ty::Adt(_, substs) = output_ty.kind();
1065 let output_ty = substs.type_at(0);
1066 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
1067 if input_ty != output_ty;
1075 let mut applicability = Applicability::MachineApplicable;
1080 &format!("use `{}()` instead", suggestion),
1084 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
1094 fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
1096 if let PatKind::Or(ref fields) = arm.pat.kind {
1097 // look for multiple fields in this arm that contains at least one Wild pattern
1098 if fields.len() > 1 && fields.iter().any(is_wild) {
1101 WILDCARD_IN_OR_PATTERNS,
1103 "wildcard pattern covers any other pattern as it will match anyway.",
1105 "Consider handling `_` separately.",
1112 /// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
1113 fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
1114 if let ExprKind::Match(ex, arms, ref match_source) = &expr.kind {
1115 match match_source {
1116 MatchSource::Normal => find_matches_sugg(cx, ex, arms, expr, false),
1117 MatchSource::IfLetDesugar { .. } => find_matches_sugg(cx, ex, arms, expr, true),
1125 /// Lint a `match` or desugared `if let` for replacement by `matches!`
1126 fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, desugared: bool) -> bool {
1129 if cx.typeck_results().expr_ty(expr).is_bool();
1130 if let Some((b1_arm, b0_arms)) = arms.split_last();
1131 if let Some(b0) = find_bool_lit(&b0_arms[0].body.kind, desugared);
1132 if let Some(b1) = find_bool_lit(&b1_arm.body.kind, desugared);
1133 if is_wild(&b1_arm.pat);
1135 let if_guard = &b0_arms[0].guard;
1136 if if_guard.is_none() || b0_arms.len() == 1;
1137 if b0_arms[1..].iter()
1139 find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) &&
1143 let mut applicability = Applicability::MachineApplicable;
1145 use itertools::Itertools as _;
1147 .map(|arm| snippet_with_applicability(cx, arm.pat.span, "..", &mut applicability))
1150 let pat_and_guard = if let Some(Guard::If(g)) = if_guard {
1151 format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
1157 MATCH_LIKE_MATCHES_MACRO,
1159 &format!("{} expression looks like `matches!` macro", if desugared { "if let .. else" } else { "match" }),
1162 "{}matches!({}, {})",
1163 if b0 { "" } else { "!" },
1164 snippet_with_applicability(cx, ex.span, "..", &mut applicability),
1176 /// Extract a `bool` or `{ bool }`
1177 fn find_bool_lit(ex: &ExprKind<'_>, desugared: bool) -> Option<bool> {
1179 ExprKind::Lit(Spanned {
1180 node: LitKind::Bool(b), ..
1190 if let ExprKind::Lit(Spanned {
1191 node: LitKind::Bool(b), ..
1203 fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
1204 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
1207 let matched_vars = ex.span;
1208 let bind_names = arms[0].pat.span;
1209 let match_body = remove_blocks(&arms[0].body);
1210 let mut snippet_body = if match_body.span.from_expansion() {
1211 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1213 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1216 // Do we need to add ';' to suggestion ?
1217 match match_body.kind {
1218 ExprKind::Block(block, _) => {
1219 // macro + expr_ty(body) == ()
1220 if block.span.from_expansion() && cx.typeck_results().expr_ty(&match_body).is_unit() {
1221 snippet_body.push(';');
1225 // expr_ty(body) == ()
1226 if cx.typeck_results().expr_ty(&match_body).is_unit() {
1227 snippet_body.push(';');
1232 let mut applicability = Applicability::MaybeIncorrect;
1233 match arms[0].pat.kind {
1234 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1235 // If this match is in a local (`let`) stmt
1236 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1238 parent_let_node.span,
1240 "let {} = {};\n{}let {} = {};",
1241 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1242 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1243 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1244 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1249 // If we are in closure, we need curly braces around suggestion
1250 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1251 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1252 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1253 if let ExprKind::Closure(..) = parent_expr.kind {
1254 cbrace_end = format!("\n{}}}", indent);
1255 // Fix body indent due to the closure
1256 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1257 cbrace_start = format!("{{\n{}", indent);
1263 "{}let {} = {};\n{}{}{}",
1265 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1266 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1275 MATCH_SINGLE_BINDING,
1277 "this match could be written as a `let` statement",
1278 "consider using `let` statement",
1286 MATCH_SINGLE_BINDING,
1288 "this match could be replaced by its body itself",
1289 "consider using the match body instead",
1291 Applicability::MachineApplicable,
1298 /// Returns true if the `ex` match expression is in a local (`let`) statement
1299 fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1301 let map = &cx.tcx.hir();
1302 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1303 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1305 return Some(parent_let_expr);
1311 /// Gets all arms that are unbounded `PatRange`s.
1312 fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec<SpannedRange<Constant>> {
1316 ref pat, guard: None, ..
1319 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1320 let lhs = match lhs {
1321 Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0,
1322 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1324 let rhs = match rhs {
1325 Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0,
1326 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1328 let rhs = match range_end {
1329 RangeEnd::Included => Bound::Included(rhs),
1330 RangeEnd::Excluded => Bound::Excluded(rhs),
1332 return Some(SpannedRange {
1338 if let PatKind::Lit(ref value) = pat.kind {
1339 let value = constant(cx, cx.typeck_results(), value)?.0;
1340 return Some(SpannedRange {
1342 node: (value.clone(), Bound::Included(value)),
1351 #[derive(Debug, Eq, PartialEq)]
1352 pub struct SpannedRange<T> {
1354 pub node: (T, Bound<T>),
1357 type TypedRanges = Vec<SpannedRange<u128>>;
1359 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1360 /// and other types than
1361 /// `Uint` and `Int` probably don't make sense.
1362 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1365 .filter_map(|range| match range.node {
1366 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1368 node: (start, Bound::Included(end)),
1370 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1372 node: (start, Bound::Excluded(end)),
1374 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1376 node: (start, Bound::Unbounded),
1383 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1385 ExprKind::Tup(ref v) if v.is_empty() => true,
1386 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1391 // Checks if arm has the form `None => None`
1392 fn is_none_arm(arm: &Arm<'_>) -> bool {
1393 matches!(arm.pat.kind, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE))
1396 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1397 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1399 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1400 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1401 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1402 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1403 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1404 if let ExprKind::Path(ref some_path) = e.kind;
1405 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1406 if let ExprKind::Path(ref qpath) = args[0].kind;
1407 if let &QPath::Resolved(_, ref path2) = qpath;
1408 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1416 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1421 PatKind::Ref(..) => Some(true), // &-patterns
1422 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1423 _ => None, // any other pattern is not fine
1426 .collect::<Option<Vec<bool>>>();
1427 // look for Some(v) where there's at least one true element
1428 mapped.map_or(false, |v| v.iter().any(|el| *el))
1431 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1435 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1437 Start(T, &'a SpannedRange<T>),
1438 End(Bound<T>, &'a SpannedRange<T>),
1441 impl<'a, T: Copy> Kind<'a, T> {
1442 fn range(&self) -> &'a SpannedRange<T> {
1444 Kind::Start(_, r) | Kind::End(_, r) => r,
1448 fn value(self) -> Bound<T> {
1450 Kind::Start(t, _) => Bound::Included(t),
1451 Kind::End(t, _) => t,
1456 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1457 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1458 Some(self.cmp(other))
1462 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1463 fn cmp(&self, other: &Self) -> Ordering {
1464 match (self.value(), other.value()) {
1465 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1466 // Range patterns cannot be unbounded (yet)
1467 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1468 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1469 Ordering::Equal => Ordering::Greater,
1472 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1473 Ordering::Equal => Ordering::Less,
1480 let mut values = Vec::with_capacity(2 * ranges.len());
1483 values.push(Kind::Start(r.node.0, r));
1484 values.push(Kind::End(r.node.1, r));
1489 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1491 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1492 if ra.node != rb.node {
1493 return Some((ra, rb));
1496 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1497 _ => return Some((a.range(), b.range())),
1504 mod redundant_pattern_match {
1505 use super::REDUNDANT_PATTERN_MATCHING;
1506 use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
1507 use if_chain::if_chain;
1508 use rustc_ast::ast::LitKind;
1509 use rustc_errors::Applicability;
1510 use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath};
1511 use rustc_lint::LateContext;
1512 use rustc_span::sym;
1514 pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1515 if let ExprKind::Match(op, arms, ref match_source) = &expr.kind {
1516 match match_source {
1517 MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
1518 MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms, "if"),
1519 MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, arms, "while"),
1525 fn find_sugg_for_if_let<'tcx>(
1526 cx: &LateContext<'tcx>,
1527 expr: &'tcx Expr<'_>,
1530 keyword: &'static str,
1532 let good_method = match arms[0].pat.kind {
1533 PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => {
1534 if let PatKind::Wild = patterns[0].kind {
1535 if match_qpath(path, &paths::RESULT_OK) {
1537 } else if match_qpath(path, &paths::RESULT_ERR) {
1539 } else if match_qpath(path, &paths::OPTION_SOME) {
1548 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()",
1552 // check that `while_let_on_iterator` lint does not trigger
1554 if keyword == "while";
1555 if let ExprKind::MethodCall(method_path, _, _, _) = op.kind;
1556 if method_path.ident.name == sym::next;
1557 if match_trait_method(cx, op, &paths::ITERATOR);
1563 let result_expr = match &op.kind {
1564 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1569 REDUNDANT_PATTERN_MATCHING,
1571 &format!("redundant pattern matching, consider using `{}`", good_method),
1573 // while let ... = ... { ... }
1574 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1575 let expr_span = expr.span;
1577 // while let ... = ... { ... }
1579 let op_span = result_expr.span.source_callsite();
1581 // while let ... = ... { ... }
1582 // ^^^^^^^^^^^^^^^^^^^
1583 let span = expr_span.until(op_span.shrink_to_hi());
1584 diag.span_suggestion(
1587 format!("{} {}.{}", keyword, snippet(cx, op_span, "_"), good_method),
1588 Applicability::MachineApplicable, // snippet
1594 fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
1595 if arms.len() == 2 {
1596 let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
1598 let found_good_method = match node_pair {
1600 PatKind::TupleStruct(ref path_left, ref patterns_left, _),
1601 PatKind::TupleStruct(ref path_right, ref patterns_right, _),
1602 ) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
1603 if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
1604 find_good_method_for_match(
1617 (PatKind::TupleStruct(ref path_left, ref patterns, _), PatKind::Path(ref path_right))
1618 | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, ref patterns, _))
1619 if patterns.len() == 1 =>
1621 if let PatKind::Wild = patterns[0].kind {
1622 find_good_method_for_match(
1626 &paths::OPTION_SOME,
1627 &paths::OPTION_NONE,
1638 if let Some(good_method) = found_good_method {
1639 let span = expr.span.to(op.span);
1640 let result_expr = match &op.kind {
1641 ExprKind::AddrOf(_, _, borrowed) => borrowed,
1646 REDUNDANT_PATTERN_MATCHING,
1648 &format!("redundant pattern matching, consider using `{}`", good_method),
1650 diag.span_suggestion(
1653 format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
1654 Applicability::MaybeIncorrect, // snippet
1662 fn find_good_method_for_match<'a>(
1664 path_left: &QPath<'_>,
1665 path_right: &QPath<'_>,
1666 expected_left: &[&str],
1667 expected_right: &[&str],
1668 should_be_left: &'a str,
1669 should_be_right: &'a str,
1670 ) -> Option<&'a str> {
1671 let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
1672 (&(*arms[0].body).kind, &(*arms[1].body).kind)
1673 } else if match_qpath(path_right, expected_left) && match_qpath(path_left, expected_right) {
1674 (&(*arms[1].body).kind, &(*arms[0].body).kind)
1679 match body_node_pair {
1680 (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
1681 (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
1682 (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
1691 fn test_overlapping() {
1692 use rustc_span::source_map::DUMMY_SP;
1694 let sp = |s, e| SpannedRange {
1699 assert_eq!(None, overlapping::<u8>(&[]));
1700 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1703 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1708 sp(1, Bound::Included(4)),
1709 sp(5, Bound::Included(6)),
1710 sp(10, Bound::Included(11))
1714 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1715 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1718 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1720 sp(1, Bound::Included(4)),
1721 sp(5, Bound::Included(6)),
1722 sp(6, Bound::Included(11))
1727 /// Implementation of `MATCH_SAME_ARMS`.
1728 fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
1729 fn same_bindings<'tcx>(lhs: &FxHashMap<Symbol, Ty<'tcx>>, rhs: &FxHashMap<Symbol, Ty<'tcx>>) -> bool {
1730 lhs.len() == rhs.len()
1733 .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| TyS::same_type(l_ty, r_ty)))
1736 if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind {
1737 let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
1738 let mut h = SpanlessHash::new(cx);
1739 h.hash_expr(&arm.body);
1743 let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
1744 let min_index = usize::min(lindex, rindex);
1745 let max_index = usize::max(lindex, rindex);
1747 // Arms with a guard are ignored, those can’t always be merged together
1748 // This is also the case for arms in-between each there is an arm with a guard
1749 (min_index..=max_index).all(|index| arms[index].guard.is_none()) &&
1750 SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
1751 // all patterns should have the same bindings
1752 same_bindings(&bindings(cx, &lhs.pat), &bindings(cx, &rhs.pat))
1755 let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
1756 for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
1761 "this `match` has identical arm bodies",
1763 diag.span_note(i.body.span, "same as this");
1765 // Note: this does not use `span_suggestion` on purpose:
1766 // there is no clean way
1767 // to remove the other arm. Building a span and suggest to replace it to ""
1768 // makes an even more confusing error message. Also in order not to make up a
1769 // span for the whole pattern, the suggestion is only shown when there is only
1770 // one pattern. The user should know about `|` if they are already using it…
1772 let lhs = snippet(cx, i.pat.span, "<pat1>");
1773 let rhs = snippet(cx, j.pat.span, "<pat2>");
1775 if let PatKind::Wild = j.pat.kind {
1776 // if the last arm is _, then i could be integrated into _
1777 // note that i.pat cannot be _, because that would mean that we're
1778 // hiding all the subsequent arms, and rust won't compile
1782 "`{}` has the same arm body as the `_` wildcard, consider removing it",
1787 diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs));
1795 /// Returns the list of bindings in a pattern.
1796 fn bindings<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>) -> FxHashMap<Symbol, Ty<'tcx>> {
1797 fn bindings_impl<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'_>, map: &mut FxHashMap<Symbol, Ty<'tcx>>) {
1799 PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
1800 PatKind::TupleStruct(_, pats, _) => {
1802 bindings_impl(cx, pat, map);
1805 PatKind::Binding(.., ident, ref as_pat) => {
1806 if let Entry::Vacant(v) = map.entry(ident.name) {
1807 v.insert(cx.typeck_results().pat_ty(pat));
1809 if let Some(ref as_pat) = *as_pat {
1810 bindings_impl(cx, as_pat, map);
1813 PatKind::Or(fields) | PatKind::Tuple(fields, _) => {
1815 bindings_impl(cx, pat, map);
1818 PatKind::Struct(_, fields, _) => {
1820 bindings_impl(cx, &pat.pat, map);
1823 PatKind::Slice(lhs, ref mid, rhs) => {
1825 bindings_impl(cx, pat, map);
1827 if let Some(ref mid) = *mid {
1828 bindings_impl(cx, mid, map);
1831 bindings_impl(cx, pat, map);
1834 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
1838 let mut result = FxHashMap::default();
1839 bindings_impl(cx, pat, &mut result);