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;
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"
415 infallible_destructuring_match_linted: bool,
418 impl_lint_pass!(Matches => [
423 MATCH_OVERLAPPING_ARM,
426 WILDCARD_ENUM_MATCH_ARM,
427 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
428 WILDCARD_IN_OR_PATTERNS,
429 MATCH_SINGLE_BINDING,
430 INFALLIBLE_DESTRUCTURING_MATCH,
431 REST_PAT_IN_FULLY_BOUND_STRUCTS
434 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
435 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
436 if in_external_macro(cx.sess(), expr.span) {
439 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
440 check_single_match(cx, ex, arms, expr);
441 check_match_bool(cx, ex, arms, expr);
442 check_overlapping_arms(cx, ex, arms);
443 check_wild_err_arm(cx, ex, arms);
444 check_wild_enum_match(cx, ex, arms);
445 check_match_as_ref(cx, ex, arms, expr);
446 check_wild_in_or_pats(cx, arms);
448 if self.infallible_destructuring_match_linted {
449 self.infallible_destructuring_match_linted = false;
451 check_match_single_binding(cx, ex, arms, expr);
454 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
455 check_match_ref_pats(cx, ex, arms, expr);
459 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
461 if !in_external_macro(cx.sess(), local.span);
462 if !in_macro(local.span);
463 if let Some(ref expr) = local.init;
464 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
465 if arms.len() == 1 && arms[0].guard.is_none();
466 if let PatKind::TupleStruct(
467 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
469 if let Some(arg) = get_arg_name(&args[0]);
470 let body = remove_blocks(&arms[0].body);
471 if match_var(body, arg);
474 let mut applicability = Applicability::MachineApplicable;
475 self.infallible_destructuring_match_linted = true;
478 INFALLIBLE_DESTRUCTURING_MATCH,
480 "you seem to be trying to use `match` to destructure a single infallible pattern. \
481 Consider using `let`",
485 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
486 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
487 snippet_with_applicability(cx, target.span, "..", &mut applicability),
495 fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) {
497 if !in_external_macro(cx.sess(), pat.span);
498 if !in_macro(pat.span);
499 if let PatKind::Struct(ref qpath, fields, true) = pat.kind;
500 if let QPath::Resolved(_, ref path) = qpath;
501 if let Some(def_id) = path.res.opt_def_id();
502 let ty = cx.tcx.type_of(def_id);
503 if let ty::Adt(def, _) = ty.kind;
504 if def.is_struct() || def.is_union();
505 if fields.len() == def.non_enum_variant().fields.len();
510 REST_PAT_IN_FULLY_BOUND_STRUCTS,
512 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
514 "consider removing `..` from this binding",
522 fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
523 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
524 if in_macro(expr.span) {
525 // Don't lint match expressions present in
526 // macro_rules! block
529 if let PatKind::Or(..) = arms[0].pat.kind {
530 // don't lint for or patterns for now, this makes
531 // the lint noisy in unnecessary situations
534 let els = remove_blocks(&arms[1].body);
535 let els = if is_unit_expr(els) {
537 } else if let ExprKind::Block(_, _) = els.kind {
538 // matches with blocks that contain statements are prettier as `if let + else`
541 // allow match arms with just expressions
544 let ty = cx.tables.expr_ty(ex);
545 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
546 check_single_match_single_pattern(cx, ex, arms, expr, els);
547 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
552 fn check_single_match_single_pattern(
553 cx: &LateContext<'_, '_>,
557 els: Option<&Expr<'_>>,
559 if is_wild(&arms[1].pat) {
560 report_single_match_single_pattern(cx, ex, arms, expr, els);
564 fn report_single_match_single_pattern(
565 cx: &LateContext<'_, '_>,
569 els: Option<&Expr<'_>>,
571 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
572 let els_str = els.map_or(String::new(), |els| {
573 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
579 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
583 "if let {} = {} {}{}",
584 snippet(cx, arms[0].pat.span, ".."),
585 snippet(cx, ex.span, ".."),
586 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
589 Applicability::HasPlaceholders,
593 fn check_single_match_opt_like(
594 cx: &LateContext<'_, '_>,
599 els: Option<&Expr<'_>>,
601 // list of candidate `Enum`s we know will never get any more members
603 (&paths::COW, "Borrowed"),
604 (&paths::COW, "Cow::Borrowed"),
605 (&paths::COW, "Cow::Owned"),
606 (&paths::COW, "Owned"),
607 (&paths::OPTION, "None"),
608 (&paths::RESULT, "Err"),
609 (&paths::RESULT, "Ok"),
612 let path = match arms[1].pat.kind {
613 PatKind::TupleStruct(ref path, ref inner, _) => {
614 // Contains any non wildcard patterns (e.g., `Err(err)`)?
615 if !inner.iter().all(is_wild) {
618 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
620 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
621 PatKind::Path(ref path) => {
622 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
627 for &(ty_path, pat_path) in candidates {
628 if path == *pat_path && match_type(cx, ty, ty_path) {
629 report_single_match_single_pattern(cx, ex, arms, expr, els);
634 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
635 // Type of expression is `bool`.
636 if cx.tables.expr_ty(ex).kind == ty::Bool {
641 "you seem to be trying to match on a boolean expression",
645 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
646 if let ExprKind::Lit(ref lit) = arm_bool.kind {
648 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
649 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
659 if let Some((true_expr, false_expr)) = exprs {
660 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
661 (false, false) => Some(format!(
663 snippet(cx, ex.span, "b"),
664 expr_block(cx, true_expr, None, "..", Some(expr.span)),
665 expr_block(cx, false_expr, None, "..", Some(expr.span))
667 (false, true) => Some(format!(
669 snippet(cx, ex.span, "b"),
670 expr_block(cx, true_expr, None, "..", Some(expr.span))
673 let test = Sugg::hir(cx, ex, "..");
677 expr_block(cx, false_expr, None, "..", Some(expr.span))
680 (true, true) => None,
683 if let Some(sugg) = sugg {
684 diag.span_suggestion(
686 "consider using an `if`/`else` expression",
688 Applicability::HasPlaceholders,
698 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
699 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
700 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
701 let type_ranges = type_ranges(&ranges);
702 if !type_ranges.is_empty() {
703 if let Some((start, end)) = overlapping(&type_ranges) {
706 MATCH_OVERLAPPING_ARM,
708 "some ranges overlap",
710 "overlaps with this",
717 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
718 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
719 if is_type_diagnostic_item(cx, ex_ty, sym!(result_type)) {
721 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
722 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
723 if path_str == "Err" {
724 let mut matching_wild = inner.iter().any(is_wild);
725 let mut ident_bind_name = String::from("_");
727 // Looking for unused bindings (i.e.: `_e`)
728 inner.iter().for_each(|pat| {
729 if let PatKind::Binding(.., ident, None) = &pat.kind {
730 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
731 ident_bind_name = (&ident.name.as_str()).to_string();
732 matching_wild = true;
739 if let ExprKind::Block(ref block, _) = arm.body.kind;
740 if is_panic_block(block);
742 // `Err(_)` or `Err(_e)` arm with `panic!` found
743 span_lint_and_note(cx,
746 &format!("`Err({})` matches all errors", &ident_bind_name),
748 "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable",
758 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
759 let ty = cx.tables.expr_ty(ex);
761 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
762 // don't complain about not enumerating the mall.
766 // First pass - check for violation, but don't do much book-keeping because this is hopefully
767 // the uncommon case, and the book-keeping is slightly expensive.
768 let mut wildcard_span = None;
769 let mut wildcard_ident = None;
771 if let PatKind::Wild = arm.pat.kind {
772 wildcard_span = Some(arm.pat.span);
773 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
774 wildcard_span = Some(arm.pat.span);
775 wildcard_ident = Some(ident);
779 if let Some(wildcard_span) = wildcard_span {
780 // Accumulate the variants which should be put in place of the wildcard because they're not
783 let mut missing_variants = vec![];
784 if let ty::Adt(def, _) = ty.kind {
785 for variant in &def.variants {
786 missing_variants.push(variant);
791 if arm.guard.is_some() {
792 // Guards mean that this case probably isn't exhaustively covered. Technically
793 // this is incorrect, as we should really check whether each variant is exhaustively
794 // covered by the set of guards that cover it, but that's really hard to do.
797 if let PatKind::Path(ref path) = arm.pat.kind {
798 if let QPath::Resolved(_, p) = path {
799 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
801 } else if let PatKind::TupleStruct(ref path, ref patterns, ..) = arm.pat.kind {
802 if let QPath::Resolved(_, p) = path {
803 // Some simple checks for exhaustive patterns.
804 // There is a room for improvements to detect more cases,
805 // but it can be more expensive to do so.
806 let is_pattern_exhaustive = |pat: &&Pat<'_>| {
807 if let PatKind::Wild | PatKind::Binding(.., None) = pat.kind {
813 if patterns.iter().all(is_pattern_exhaustive) {
814 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
820 let mut suggestion: Vec<String> = missing_variants
823 let suffix = match v.ctor_kind {
824 CtorKind::Fn => "(..)",
825 CtorKind::Const | CtorKind::Fictive => "",
827 let ident_str = if let Some(ident) = wildcard_ident {
828 format!("{} @ ", ident.name)
832 // This path assumes that the enum type is imported into scope.
833 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
837 if suggestion.is_empty() {
841 let mut message = "wildcard match will miss any future added variants";
843 if let ty::Adt(def, _) = ty.kind {
844 if def.is_variant_list_non_exhaustive() {
845 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
846 suggestion.push(String::from("_"));
850 if suggestion.len() == 1 {
851 // No need to check for non-exhaustive enum as in that case len would be greater than 1
854 MATCH_WILDCARD_FOR_SINGLE_VARIANTS,
858 suggestion[0].clone(),
859 Applicability::MaybeIncorrect,
865 WILDCARD_ENUM_MATCH_ARM,
869 suggestion.join(" | "),
870 Applicability::MaybeIncorrect,
875 // If the block contains only a `panic!` macro (as expression or statement)
876 fn is_panic_block(block: &Block<'_>) -> bool {
877 match (&block.expr, block.stmts.len(), block.stmts.first()) {
878 (&Some(ref exp), 0, _) => {
879 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
881 (&None, 1, Some(stmt)) => {
882 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
888 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
889 if has_only_ref_pats(arms) {
890 let mut suggs = Vec::with_capacity(arms.len() + 1);
891 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
892 let span = ex.span.source_callsite();
893 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
895 "you don't need to add `&` to both the expression and the patterns",
899 let span = ex.span.source_callsite();
900 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
902 "you don't need to add `&` to all patterns",
903 "instead of prefixing all patterns with `&`, you can dereference the expression",
907 suggs.extend(arms.iter().filter_map(|a| {
908 if let PatKind::Ref(ref refp, _) = a.pat.kind {
909 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
915 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| {
916 if !expr.span.from_expansion() {
917 multispan_sugg(diag, msg, suggs);
923 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
924 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
925 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
926 is_ref_some_arm(&arms[1])
927 } else if is_none_arm(&arms[1]) {
928 is_ref_some_arm(&arms[0])
932 if let Some(rb) = arm_ref {
933 let suggestion = if rb == BindingAnnotation::Ref {
939 let output_ty = cx.tables.expr_ty(expr);
940 let input_ty = cx.tables.expr_ty(ex);
942 let cast = if_chain! {
943 if let ty::Adt(_, substs) = input_ty.kind;
944 let input_ty = substs.type_at(0);
945 if let ty::Adt(_, substs) = output_ty.kind;
946 let output_ty = substs.type_at(0);
947 if let ty::Ref(_, output_ty, _) = output_ty.kind;
948 if input_ty != output_ty;
956 let mut applicability = Applicability::MachineApplicable;
961 &format!("use `{}()` instead", suggestion),
965 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
975 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
977 if let PatKind::Or(ref fields) = arm.pat.kind {
978 // look for multiple fields in this arm that contains at least one Wild pattern
979 if fields.len() > 1 && fields.iter().any(is_wild) {
982 WILDCARD_IN_OR_PATTERNS,
984 "wildcard pattern covers any other pattern as it will match anyway.",
986 "Consider handling `_` separately.",
993 fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
994 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
997 let matched_vars = ex.span;
998 let bind_names = arms[0].pat.span;
999 let match_body = remove_blocks(&arms[0].body);
1000 let mut snippet_body = if match_body.span.from_expansion() {
1001 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
1003 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
1006 // Do we need to add ';' to suggestion ?
1007 match match_body.kind {
1008 ExprKind::Block(block, _) => {
1009 // macro + expr_ty(body) == ()
1010 if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() {
1011 snippet_body.push(';');
1015 // expr_ty(body) == ()
1016 if cx.tables.expr_ty(&match_body).is_unit() {
1017 snippet_body.push(';');
1022 let mut applicability = Applicability::MaybeIncorrect;
1023 match arms[0].pat.kind {
1024 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
1025 // If this match is in a local (`let`) stmt
1026 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
1028 parent_let_node.span,
1030 "let {} = {};\n{}let {} = {};",
1031 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1032 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1033 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
1034 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
1039 // If we are in closure, we need curly braces around suggestion
1040 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
1041 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
1042 if let Some(parent_expr) = get_parent_expr(cx, expr) {
1043 if let ExprKind::Closure(..) = parent_expr.kind {
1044 cbrace_end = format!("\n{}}}", indent);
1045 // Fix body indent due to the closure
1046 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
1047 cbrace_start = format!("{{\n{}", indent);
1053 "{}let {} = {};\n{}{}{}",
1055 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
1056 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
1065 MATCH_SINGLE_BINDING,
1067 "this match could be written as a `let` statement",
1068 "consider using `let` statement",
1076 MATCH_SINGLE_BINDING,
1078 "this match could be replaced by its body itself",
1079 "consider using the match body instead",
1081 Applicability::MachineApplicable,
1088 /// Returns true if the `ex` match expression is in a local (`let`) statement
1089 fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
1091 let map = &cx.tcx.hir();
1092 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
1093 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
1095 return Some(parent_let_expr);
1101 /// Gets all arms that are unbounded `PatRange`s.
1102 fn all_ranges<'a, 'tcx>(
1103 cx: &LateContext<'a, 'tcx>,
1104 arms: &'tcx [Arm<'_>],
1106 ) -> Vec<SpannedRange<Constant>> {
1110 ref pat, guard: None, ..
1113 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1114 let lhs = match lhs {
1115 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
1116 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1118 let rhs = match rhs {
1119 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
1120 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1122 let rhs = match range_end {
1123 RangeEnd::Included => Bound::Included(rhs),
1124 RangeEnd::Excluded => Bound::Excluded(rhs),
1126 return Some(SpannedRange {
1132 if let PatKind::Lit(ref value) = pat.kind {
1133 let value = constant(cx, cx.tables, value)?.0;
1134 return Some(SpannedRange {
1136 node: (value.clone(), Bound::Included(value)),
1145 #[derive(Debug, Eq, PartialEq)]
1146 pub struct SpannedRange<T> {
1148 pub node: (T, Bound<T>),
1151 type TypedRanges = Vec<SpannedRange<u128>>;
1153 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1154 /// and other types than
1155 /// `Uint` and `Int` probably don't make sense.
1156 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1159 .filter_map(|range| match range.node {
1160 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1162 node: (start, Bound::Included(end)),
1164 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1166 node: (start, Bound::Excluded(end)),
1168 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1170 node: (start, Bound::Unbounded),
1177 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1179 ExprKind::Tup(ref v) if v.is_empty() => true,
1180 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1185 // Checks if arm has the form `None => None`
1186 fn is_none_arm(arm: &Arm<'_>) -> bool {
1187 match arm.pat.kind {
1188 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
1193 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1194 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1196 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1197 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1198 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1199 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1200 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1201 if let ExprKind::Path(ref some_path) = e.kind;
1202 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1203 if let ExprKind::Path(ref qpath) = args[0].kind;
1204 if let &QPath::Resolved(_, ref path2) = qpath;
1205 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1213 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1218 PatKind::Ref(..) => Some(true), // &-patterns
1219 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1220 _ => None, // any other pattern is not fine
1223 .collect::<Option<Vec<bool>>>();
1224 // look for Some(v) where there's at least one true element
1225 mapped.map_or(false, |v| v.iter().any(|el| *el))
1228 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1232 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1234 Start(T, &'a SpannedRange<T>),
1235 End(Bound<T>, &'a SpannedRange<T>),
1238 impl<'a, T: Copy> Kind<'a, T> {
1239 fn range(&self) -> &'a SpannedRange<T> {
1241 Kind::Start(_, r) | Kind::End(_, r) => r,
1245 fn value(self) -> Bound<T> {
1247 Kind::Start(t, _) => Bound::Included(t),
1248 Kind::End(t, _) => t,
1253 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1254 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1255 Some(self.cmp(other))
1259 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1260 fn cmp(&self, other: &Self) -> Ordering {
1261 match (self.value(), other.value()) {
1262 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1263 // Range patterns cannot be unbounded (yet)
1264 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1265 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1266 Ordering::Equal => Ordering::Greater,
1269 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1270 Ordering::Equal => Ordering::Less,
1277 let mut values = Vec::with_capacity(2 * ranges.len());
1280 values.push(Kind::Start(r.node.0, r));
1281 values.push(Kind::End(r.node.1, r));
1286 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1288 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1289 if ra.node != rb.node {
1290 return Some((ra, rb));
1293 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1294 _ => return Some((a.range(), b.range())),
1302 fn test_overlapping() {
1303 use rustc_span::source_map::DUMMY_SP;
1305 let sp = |s, e| SpannedRange {
1310 assert_eq!(None, overlapping::<u8>(&[]));
1311 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1314 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1319 sp(1, Bound::Included(4)),
1320 sp(5, Bound::Included(6)),
1321 sp(10, Bound::Included(11))
1325 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1326 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1329 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1331 sp(1, Bound::Included(4)),
1332 sp(5, Bound::Included(6)),
1333 sp(6, Bound::Included(11))