1 use crate::consts::{constant, miri_to_const, Constant};
2 use crate::utils::paths;
3 use crate::utils::sugg::Sugg;
4 use crate::utils::usage::is_unused;
6 expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable,
7 is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, multispan_sugg, remove_blocks, snippet,
8 snippet_block, snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
9 span_lint_and_then, walk_ptrs_ty,
11 use if_chain::if_chain;
12 use rustc_ast::ast::LitKind;
13 use rustc_errors::Applicability;
14 use rustc_hir::def::CtorKind;
16 Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat, PatKind,
19 use rustc_lint::{LateContext, LateLintPass, LintContext};
20 use rustc_middle::lint::in_external_macro;
21 use rustc_middle::ty::{self, Ty};
22 use rustc_session::{declare_tool_lint, impl_lint_pass};
23 use rustc_span::source_map::Span;
24 use std::cmp::Ordering;
25 use std::collections::Bound;
27 declare_clippy_lint! {
28 /// **What it does:** Checks for matches with a single arm where an `if let`
29 /// will usually suffice.
31 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
33 /// **Known problems:** None.
37 /// # fn bar(stool: &str) {}
38 /// # let x = Some("abc");
42 /// Some(ref foo) => bar(foo),
47 /// if let Some(ref foo) = x {
53 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
56 declare_clippy_lint! {
57 /// **What it does:** Checks for matches with two arms where an `if let else` will
60 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
62 /// **Known problems:** Personal style preferences may differ.
69 /// # fn bar(foo: &usize) {}
70 /// # let other_ref: usize = 1;
71 /// # let x: Option<&usize> = Some(&1);
73 /// Some(ref foo) => bar(foo),
74 /// _ => bar(&other_ref),
78 /// Using `if let` with `else`:
81 /// # fn bar(foo: &usize) {}
82 /// # let other_ref: usize = 1;
83 /// # let x: Option<&usize> = Some(&1);
84 /// if let Some(ref foo) = x {
90 pub SINGLE_MATCH_ELSE,
92 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
95 declare_clippy_lint! {
96 /// **What it does:** Checks for matches where all arms match a reference,
97 /// suggesting to remove the reference and deref the matched expression
98 /// instead. It also checks for `if let &foo = bar` blocks.
100 /// **Why is this bad?** It just makes the code less readable. That reference
101 /// destructuring adds nothing to the code.
103 /// **Known problems:** None.
109 /// &A(ref y) => foo(y),
116 /// A(ref y) => foo(y),
123 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
126 declare_clippy_lint! {
127 /// **What it does:** Checks for matches where match expression is a `bool`. It
128 /// suggests to replace the expression with an `if...else` block.
130 /// **Why is this bad?** It makes the code less readable.
132 /// **Known problems:** None.
138 /// let condition: bool = true;
139 /// match condition {
144 /// Use if/else instead:
148 /// let condition: bool = true;
157 "a `match` on a boolean expression instead of an `if..else` block"
160 declare_clippy_lint! {
161 /// **What it does:** Checks for overlapping match arms.
163 /// **Why is this bad?** It is likely to be an error and if not, makes the code
166 /// **Known problems:** None.
172 /// 1...10 => println!("1 ... 10"),
173 /// 5...15 => println!("5 ... 15"),
177 pub MATCH_OVERLAPPING_ARM,
179 "a `match` with overlapping arms"
182 declare_clippy_lint! {
183 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
184 /// and take drastic actions like `panic!`.
186 /// **Why is this bad?** It is generally a bad practice, similar to
187 /// catching all exceptions in java with `catch(Exception)`
189 /// **Known problems:** None.
193 /// let x: Result<i32, &str> = Ok(3);
195 /// Ok(_) => println!("ok"),
196 /// Err(_) => panic!("err"),
199 pub MATCH_WILD_ERR_ARM,
201 "a `match` with `Err(_)` arm and take drastic actions"
204 declare_clippy_lint! {
205 /// **What it does:** Checks for match which is used to add a reference to an
208 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
210 /// **Known problems:** None.
214 /// let x: Option<()> = None;
217 /// let r: Option<&()> = match x {
219 /// Some(ref v) => Some(v),
223 /// let r: Option<&()> = x.as_ref();
227 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
230 declare_clippy_lint! {
231 /// **What it does:** Checks for wildcard enum matches using `_`.
233 /// **Why is this bad?** New enum variants added by library updates can be missed.
235 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
236 /// variants, and also may not use correct path to enum if it's not present in the current scope.
240 /// # enum Foo { A(usize), B(usize) }
241 /// # let x = Foo::B(1);
255 pub WILDCARD_ENUM_MATCH_ARM,
257 "a wildcard enum match arm using `_`"
260 declare_clippy_lint! {
261 /// **What it does:** Checks for wildcard enum matches for a single variant.
263 /// **Why is this bad?** New enum variants added by library updates can be missed.
265 /// **Known problems:** Suggested replacements may not use correct path to enum
266 /// if it's not present in the current scope.
271 /// # enum Foo { A, B, C }
272 /// # let x = Foo::B;
287 pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
289 "a wildcard enum match for a single variant"
292 declare_clippy_lint! {
293 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
295 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
296 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
298 /// **Known problems:** None.
314 pub WILDCARD_IN_OR_PATTERNS,
316 "a wildcard pattern used with others patterns in same match arm"
319 declare_clippy_lint! {
320 /// **What it does:** Checks for matches being used to destructure a single-variant enum
321 /// or tuple struct where a `let` will suffice.
323 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
325 /// **Known problems:** None.
333 /// let wrapper = Wrapper::Data(42);
335 /// let data = match wrapper {
336 /// Wrapper::Data(i) => i,
340 /// The correct use would be:
346 /// let wrapper = Wrapper::Data(42);
347 /// let Wrapper::Data(data) = wrapper;
349 pub INFALLIBLE_DESTRUCTURING_MATCH,
351 "a `match` statement with a single infallible arm instead of a `let`"
354 declare_clippy_lint! {
355 /// **What it does:** Checks for useless match that binds to only one value.
357 /// **Why is this bad?** Readability and needless complexity.
359 /// **Known problems:** Suggested replacements may be incorrect when `match`
360 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
375 /// let (c, d) = (a, b);
377 pub MATCH_SINGLE_BINDING,
379 "a match with a single binding instead of using `let` statement"
382 declare_clippy_lint! {
383 /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
385 /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after
386 /// matching all enum variants explicitly.
388 /// **Known problems:** None.
392 /// # struct A { a: i32 }
393 /// let a = A { a: 5 };
397 /// A { a: 5, .. } => {},
403 /// A { a: 5 } => {},
407 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
409 "a match on a struct that binds all fields but still uses the wildcard pattern"
414 infallible_destructuring_match_linted: bool,
417 impl_lint_pass!(Matches => [
422 MATCH_OVERLAPPING_ARM,
425 WILDCARD_ENUM_MATCH_ARM,
426 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
427 WILDCARD_IN_OR_PATTERNS,
428 MATCH_SINGLE_BINDING,
429 INFALLIBLE_DESTRUCTURING_MATCH,
430 REST_PAT_IN_FULLY_BOUND_STRUCTS
433 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
434 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
435 if in_external_macro(cx.sess(), expr.span) {
438 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
439 check_single_match(cx, ex, arms, expr);
440 check_match_bool(cx, ex, arms, expr);
441 check_overlapping_arms(cx, ex, arms);
442 check_wild_err_arm(cx, ex, arms);
443 check_wild_enum_match(cx, ex, arms);
444 check_match_as_ref(cx, ex, arms, expr);
445 check_wild_in_or_pats(cx, arms);
447 if self.infallible_destructuring_match_linted {
448 self.infallible_destructuring_match_linted = false;
450 check_match_single_binding(cx, ex, arms, expr);
453 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
454 check_match_ref_pats(cx, ex, arms, expr);
458 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
460 if !in_external_macro(cx.sess(), local.span);
461 if !in_macro(local.span);
462 if let Some(ref expr) = local.init;
463 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
464 if arms.len() == 1 && arms[0].guard.is_none();
465 if let PatKind::TupleStruct(
466 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
468 if let Some(arg) = get_arg_name(&args[0]);
469 let body = remove_blocks(&arms[0].body);
470 if match_var(body, arg);
473 let mut applicability = Applicability::MachineApplicable;
474 self.infallible_destructuring_match_linted = true;
477 INFALLIBLE_DESTRUCTURING_MATCH,
479 "you seem to be trying to use `match` to destructure a single infallible pattern. \
480 Consider using `let`",
484 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
485 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
486 snippet_with_applicability(cx, target.span, "..", &mut applicability),
494 fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) {
496 if !in_external_macro(cx.sess(), pat.span);
497 if !in_macro(pat.span);
498 if let PatKind::Struct(ref qpath, fields, true) = pat.kind;
499 if let QPath::Resolved(_, ref path) = qpath;
500 if let Some(def_id) = path.res.opt_def_id();
501 let ty = cx.tcx.type_of(def_id);
502 if let ty::Adt(def, _) = ty.kind;
503 if def.is_struct() || def.is_union();
504 if fields.len() == def.non_enum_variant().fields.len();
509 REST_PAT_IN_FULLY_BOUND_STRUCTS,
511 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
513 "consider removing `..` from this binding",
521 fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
522 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
523 if in_macro(expr.span) {
524 // Don't lint match expressions present in
525 // macro_rules! block
528 if let PatKind::Or(..) = arms[0].pat.kind {
529 // don't lint for or patterns for now, this makes
530 // the lint noisy in unnecessary situations
533 let els = remove_blocks(&arms[1].body);
534 let els = if is_unit_expr(els) {
536 } else if let ExprKind::Block(_, _) = els.kind {
537 // matches with blocks that contain statements are prettier as `if let + else`
540 // allow match arms with just expressions
543 let ty = cx.tables.expr_ty(ex);
544 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
545 check_single_match_single_pattern(cx, ex, arms, expr, els);
546 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
551 fn check_single_match_single_pattern(
552 cx: &LateContext<'_, '_>,
556 els: Option<&Expr<'_>>,
558 if is_wild(&arms[1].pat) {
559 report_single_match_single_pattern(cx, ex, arms, expr, els);
563 fn report_single_match_single_pattern(
564 cx: &LateContext<'_, '_>,
568 els: Option<&Expr<'_>>,
570 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
571 let els_str = els.map_or(String::new(), |els| {
572 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
578 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
582 "if let {} = {} {}{}",
583 snippet(cx, arms[0].pat.span, ".."),
584 snippet(cx, ex.span, ".."),
585 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
588 Applicability::HasPlaceholders,
592 fn check_single_match_opt_like(
593 cx: &LateContext<'_, '_>,
598 els: Option<&Expr<'_>>,
600 // list of candidate `Enum`s we know will never get any more members
602 (&paths::COW, "Borrowed"),
603 (&paths::COW, "Cow::Borrowed"),
604 (&paths::COW, "Cow::Owned"),
605 (&paths::COW, "Owned"),
606 (&paths::OPTION, "None"),
607 (&paths::RESULT, "Err"),
608 (&paths::RESULT, "Ok"),
611 let path = match arms[1].pat.kind {
612 PatKind::TupleStruct(ref path, ref inner, _) => {
613 // Contains any non wildcard patterns (e.g., `Err(err)`)?
614 if !inner.iter().all(is_wild) {
617 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
619 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
620 PatKind::Path(ref path) => {
621 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
626 for &(ty_path, pat_path) in candidates {
627 if path == *pat_path && match_type(cx, ty, ty_path) {
628 report_single_match_single_pattern(cx, ex, arms, expr, els);
633 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
634 // Type of expression is `bool`.
635 if cx.tables.expr_ty(ex).kind == ty::Bool {
640 "you seem to be trying to match on a boolean expression",
644 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
645 if let ExprKind::Lit(ref lit) = arm_bool.kind {
647 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
648 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
658 if let Some((true_expr, false_expr)) = exprs {
659 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
660 (false, false) => Some(format!(
662 snippet(cx, ex.span, "b"),
663 expr_block(cx, true_expr, None, "..", Some(expr.span)),
664 expr_block(cx, false_expr, None, "..", Some(expr.span))
666 (false, true) => Some(format!(
668 snippet(cx, ex.span, "b"),
669 expr_block(cx, true_expr, None, "..", Some(expr.span))
672 let test = Sugg::hir(cx, ex, "..");
676 expr_block(cx, false_expr, None, "..", Some(expr.span))
679 (true, true) => None,
682 if let Some(sugg) = sugg {
683 diag.span_suggestion(
685 "consider using an `if`/`else` expression",
687 Applicability::HasPlaceholders,
697 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
698 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
699 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
700 let type_ranges = type_ranges(&ranges);
701 if !type_ranges.is_empty() {
702 if let Some((start, end)) = overlapping(&type_ranges) {
705 MATCH_OVERLAPPING_ARM,
707 "some ranges overlap",
709 "overlaps with this",
716 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
717 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
718 if is_type_diagnostic_item(cx, ex_ty, sym!(result_type)) {
720 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
721 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
722 if path_str == "Err" {
723 let mut matching_wild = inner.iter().any(is_wild);
724 let mut ident_bind_name = String::from("_");
726 // Looking for unused bindings (i.e.: `_e`)
727 inner.iter().for_each(|pat| {
728 if let PatKind::Binding(.., ident, None) = &pat.kind {
729 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
730 ident_bind_name = (&ident.name.as_str()).to_string();
731 matching_wild = true;
738 if let ExprKind::Block(ref block, _) = arm.body.kind;
739 if is_panic_block(block);
741 // `Err(_)` or `Err(_e)` arm with `panic!` found
742 span_lint_and_note(cx,
745 &format!("`Err({})` matches all errors", &ident_bind_name),
747 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
757 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
758 let ty = cx.tables.expr_ty(ex);
760 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
761 // don't complain about not enumerating the mall.
765 // First pass - check for violation, but don't do much book-keeping because this is hopefully
766 // the uncommon case, and the book-keeping is slightly expensive.
767 let mut wildcard_span = None;
768 let mut wildcard_ident = None;
770 if let PatKind::Wild = arm.pat.kind {
771 wildcard_span = Some(arm.pat.span);
772 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
773 wildcard_span = Some(arm.pat.span);
774 wildcard_ident = Some(ident);
778 if let Some(wildcard_span) = wildcard_span {
779 // Accumulate the variants which should be put in place of the wildcard because they're not
782 let mut missing_variants = vec![];
783 if let ty::Adt(def, _) = ty.kind {
784 for variant in &def.variants {
785 missing_variants.push(variant);
790 if arm.guard.is_some() {
791 // Guards mean that this case probably isn't exhaustively covered. Technically
792 // this is incorrect, as we should really check whether each variant is exhaustively
793 // covered by the set of guards that cover it, but that's really hard to do.
796 if let PatKind::Path(ref path) = arm.pat.kind {
797 if let QPath::Resolved(_, p) = path {
798 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
800 } else if let PatKind::TupleStruct(ref path, ref patterns, ..) = arm.pat.kind {
801 if let QPath::Resolved(_, p) = path {
802 // Some simple checks for exhaustive patterns.
803 // There is a room for improvements to detect more cases,
804 // but it can be more expensive to do so.
805 let is_pattern_exhaustive = |pat: &&Pat<'_>| {
806 if let PatKind::Wild | PatKind::Binding(.., None) = pat.kind {
812 if patterns.iter().all(is_pattern_exhaustive) {
813 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
819 let mut suggestion: Vec<String> = missing_variants
822 let suffix = match v.ctor_kind {
823 CtorKind::Fn => "(..)",
824 CtorKind::Const | CtorKind::Fictive => "",
826 let ident_str = if let Some(ident) = wildcard_ident {
827 format!("{} @ ", ident.name)
831 // This path assumes that the enum type is imported into scope.
832 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
836 if suggestion.is_empty() {
840 let mut message = "wildcard match will miss any future added variants";
842 if let ty::Adt(def, _) = ty.kind {
843 if def.is_variant_list_non_exhaustive() {
844 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
845 suggestion.push(String::from("_"));
849 if suggestion.len() == 1 {
850 // No need to check for non-exhaustive enum as in that case len would be greater than 1
853 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
857 suggestion[0].clone(),
858 Applicability::MaybeIncorrect,
864 WILDCARD_ENUM_MATCH_ARM,
868 suggestion.join(" | "),
869 Applicability::MaybeIncorrect,
874 // If the block contains only a `panic!` macro (as expression or statement)
875 fn is_panic_block(block: &Block<'_>) -> bool {
876 match (&block.expr, block.stmts.len(), block.stmts.first()) {
877 (&Some(ref exp), 0, _) => {
878 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
880 (&None, 1, Some(stmt)) => {
881 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
887 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
888 if has_only_ref_pats(arms) {
889 let mut suggs = Vec::with_capacity(arms.len() + 1);
890 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
891 let span = ex.span.source_callsite();
892 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
894 "you don't need to add `&` to both the expression and the patterns",
898 let span = ex.span.source_callsite();
899 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
901 "you don't need to add `&` to all patterns",
902 "instead of prefixing all patterns with `&`, you can dereference the expression",
906 suggs.extend(arms.iter().filter_map(|a| {
907 if let PatKind::Ref(ref refp, _) = a.pat.kind {
908 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
914 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
915 if !expr.span.from_expansion() {
916 multispan_sugg(diag, msg, suggs);
922 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
923 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
924 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
925 is_ref_some_arm(&arms[1])
926 } else if is_none_arm(&arms[1]) {
927 is_ref_some_arm(&arms[0])
931 if let Some(rb) = arm_ref {
932 let suggestion = if rb == BindingAnnotation::Ref {
938 let output_ty = cx.tables.expr_ty(expr);
939 let input_ty = cx.tables.expr_ty(ex);
941 let cast = if_chain! {
942 if let ty::Adt(_, substs) = input_ty.kind;
943 let input_ty = substs.type_at(0);
944 if let ty::Adt(_, substs) = output_ty.kind;
945 let output_ty = substs.type_at(0);
946 if let ty::Ref(_, output_ty, _) = output_ty.kind;
947 if input_ty != output_ty;
955 let mut applicability = Applicability::MachineApplicable;
960 &format!("use `{}()` instead", suggestion),
964 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
974 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
976 if let PatKind::Or(ref fields) = arm.pat.kind {
977 // look for multiple fields in this arm that contains at least one Wild pattern
978 if fields.len() > 1 && fields.iter().any(is_wild) {
981 WILDCARD_IN_OR_PATTERNS,
983 "wildcard pattern covers any other pattern as it will match anyway.",
985 "Consider handling `_` separately.",
992 fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
993 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
996 let matched_vars = ex.span;
997 let bind_names = arms[0].pat.span;
998 let match_body = remove_blocks(&arms[0].body);
999 let mut snippet_body = if match_body.span.from_expansion() {
1000 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1002 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1005 // Do we need to add ';' to suggestion ?
1006 match match_body.kind {
1007 ExprKind::Block(block, _) => {
1008 // macro + expr_ty(body) == ()
1009 if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() {
1010 snippet_body.push(';');
1014 // expr_ty(body) == ()
1015 if cx.tables.expr_ty(&match_body).is_unit() {
1016 snippet_body.push(';');
1021 let mut applicability = Applicability::MaybeIncorrect;
1022 match arms[0].pat.kind {
1023 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1024 // If this match is in a local (`let`) stmt
1025 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1027 parent_let_node.span,
1029 "let {} = {};\n{}let {} = {};",
1030 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1031 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1032 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1033 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1038 // If we are in closure, we need curly braces around suggestion
1039 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1040 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1041 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1042 if let ExprKind::Closure(..) = parent_expr.kind {
1043 cbrace_end = format!("\n{}}}", indent);
1044 // Fix body indent due to the closure
1045 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1046 cbrace_start = format!("{{\n{}", indent);
1052 "{}let {} = {};\n{}{}{}",
1054 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1055 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1064 MATCH_SINGLE_BINDING,
1066 "this match could be written as a `let` statement",
1067 "consider using `let` statement",
1075 MATCH_SINGLE_BINDING,
1077 "this match could be replaced by its body itself",
1078 "consider using the match body instead",
1080 Applicability::MachineApplicable,
1087 /// Returns true if the `ex` match expression is in a local (`let`) statement
1088 fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1090 let map = &cx.tcx.hir();
1091 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1092 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1094 return Some(parent_let_expr);
1100 /// Gets all arms that are unbounded `PatRange`s.
1101 fn all_ranges<'a, 'tcx>(
1102 cx: &LateContext<'a, 'tcx>,
1103 arms: &'tcx [Arm<'_>],
1105 ) -> Vec<SpannedRange<Constant>> {
1109 ref pat, guard: None, ..
1112 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1113 let lhs = match lhs {
1114 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
1115 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1117 let rhs = match rhs {
1118 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
1119 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1121 let rhs = match range_end {
1122 RangeEnd::Included => Bound::Included(rhs),
1123 RangeEnd::Excluded => Bound::Excluded(rhs),
1125 return Some(SpannedRange {
1131 if let PatKind::Lit(ref value) = pat.kind {
1132 let value = constant(cx, cx.tables, value)?.0;
1133 return Some(SpannedRange {
1135 node: (value.clone(), Bound::Included(value)),
1144 #[derive(Debug, Eq, PartialEq)]
1145 pub struct SpannedRange<T> {
1147 pub node: (T, Bound<T>),
1150 type TypedRanges = Vec<SpannedRange<u128>>;
1152 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1153 /// and other types than
1154 /// `Uint` and `Int` probably don't make sense.
1155 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1158 .filter_map(|range| match range.node {
1159 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1161 node: (start, Bound::Included(end)),
1163 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1165 node: (start, Bound::Excluded(end)),
1167 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1169 node: (start, Bound::Unbounded),
1176 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1178 ExprKind::Tup(ref v) if v.is_empty() => true,
1179 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1184 // Checks if arm has the form `None => None`
1185 fn is_none_arm(arm: &Arm<'_>) -> bool {
1186 match arm.pat.kind {
1187 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
1192 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1193 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1195 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1196 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1197 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1198 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1199 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1200 if let ExprKind::Path(ref some_path) = e.kind;
1201 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1202 if let ExprKind::Path(ref qpath) = args[0].kind;
1203 if let &QPath::Resolved(_, ref path2) = qpath;
1204 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1212 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1217 PatKind::Ref(..) => Some(true), // &-patterns
1218 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1219 _ => None, // any other pattern is not fine
1222 .collect::<Option<Vec<bool>>>();
1223 // look for Some(v) where there's at least one true element
1224 mapped.map_or(false, |v| v.iter().any(|el| *el))
1227 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1231 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1233 Start(T, &'a SpannedRange<T>),
1234 End(Bound<T>, &'a SpannedRange<T>),
1237 impl<'a, T: Copy> Kind<'a, T> {
1238 fn range(&self) -> &'a SpannedRange<T> {
1240 Kind::Start(_, r) | Kind::End(_, r) => r,
1244 fn value(self) -> Bound<T> {
1246 Kind::Start(t, _) => Bound::Included(t),
1247 Kind::End(t, _) => t,
1252 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1253 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1254 Some(self.cmp(other))
1258 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1259 fn cmp(&self, other: &Self) -> Ordering {
1260 match (self.value(), other.value()) {
1261 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1262 // Range patterns cannot be unbounded (yet)
1263 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1264 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1265 Ordering::Equal => Ordering::Greater,
1268 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1269 Ordering::Equal => Ordering::Less,
1276 let mut values = Vec::with_capacity(2 * ranges.len());
1279 values.push(Kind::Start(r.node.0, r));
1280 values.push(Kind::End(r.node.1, r));
1285 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1287 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1288 if ra.node != rb.node {
1289 return Some((ra, rb));
1292 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1293 _ => return Some((a.range(), b.range())),
1301 fn test_overlapping() {
1302 use rustc_span::source_map::DUMMY_SP;
1304 let sp = |s, e| SpannedRange {
1309 assert_eq!(None, overlapping::<u8>(&[]));
1310 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1313 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1318 sp(1, Bound::Included(4)),
1319 sp(5, Bound::Included(6)),
1320 sp(10, Bound::Included(11))
1324 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1325 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1328 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1330 sp(1, Bound::Included(4)),
1331 sp(5, Bound::Included(6)),
1332 sp(6, Bound::Included(11))