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, is_wild,
7 match_qpath, match_type, match_var, multispan_sugg, remove_blocks, snippet, snippet_block,
8 snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
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");
40 /// Some(ref foo) => bar(foo),
46 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
49 declare_clippy_lint! {
50 /// **What it does:** Checks for matches with two arms where an `if let else` will
53 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
55 /// **Known problems:** Personal style preferences may differ.
62 /// # fn bar(foo: &usize) {}
63 /// # let other_ref: usize = 1;
64 /// # let x: Option<&usize> = Some(&1);
66 /// Some(ref foo) => bar(foo),
67 /// _ => bar(&other_ref),
71 /// Using `if let` with `else`:
74 /// # fn bar(foo: &usize) {}
75 /// # let other_ref: usize = 1;
76 /// # let x: Option<&usize> = Some(&1);
77 /// if let Some(ref foo) = x {
83 pub SINGLE_MATCH_ELSE,
85 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
88 declare_clippy_lint! {
89 /// **What it does:** Checks for matches where all arms match a reference,
90 /// suggesting to remove the reference and deref the matched expression
91 /// instead. It also checks for `if let &foo = bar` blocks.
93 /// **Why is this bad?** It just makes the code less readable. That reference
94 /// destructuring adds nothing to the code.
96 /// **Known problems:** None.
101 /// &A(ref y) => foo(y),
108 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
111 declare_clippy_lint! {
112 /// **What it does:** Checks for matches where match expression is a `bool`. It
113 /// suggests to replace the expression with an `if...else` block.
115 /// **Why is this bad?** It makes the code less readable.
117 /// **Known problems:** None.
123 /// let condition: bool = true;
124 /// match condition {
129 /// Use if/else instead:
133 /// let condition: bool = true;
142 "a `match` on a boolean expression instead of an `if..else` block"
145 declare_clippy_lint! {
146 /// **What it does:** Checks for overlapping match arms.
148 /// **Why is this bad?** It is likely to be an error and if not, makes the code
151 /// **Known problems:** None.
157 /// 1...10 => println!("1 ... 10"),
158 /// 5...15 => println!("5 ... 15"),
162 pub MATCH_OVERLAPPING_ARM,
164 "a `match` with overlapping arms"
167 declare_clippy_lint! {
168 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
169 /// and take drastic actions like `panic!`.
171 /// **Why is this bad?** It is generally a bad practice, just like
172 /// catching all exceptions in java with `catch(Exception)`
174 /// **Known problems:** None.
178 /// let x: Result<i32, &str> = Ok(3);
180 /// Ok(_) => println!("ok"),
181 /// Err(_) => panic!("err"),
184 pub MATCH_WILD_ERR_ARM,
186 "a `match` with `Err(_)` arm and take drastic actions"
189 declare_clippy_lint! {
190 /// **What it does:** Checks for match which is used to add a reference to an
193 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
195 /// **Known problems:** None.
199 /// let x: Option<()> = None;
200 /// let r: Option<&()> = match x {
202 /// Some(ref v) => Some(v),
207 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
210 declare_clippy_lint! {
211 /// **What it does:** Checks for wildcard enum matches using `_`.
213 /// **Why is this bad?** New enum variants added by library updates can be missed.
215 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
216 /// variants, and also may not use correct path to enum if it's not present in the current scope.
220 /// # enum Foo { A(usize), B(usize) }
221 /// # let x = Foo::B(1);
227 pub WILDCARD_ENUM_MATCH_ARM,
229 "a wildcard enum match arm using `_`"
232 declare_clippy_lint! {
233 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
235 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
236 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
238 /// **Known problems:** None.
247 pub WILDCARD_IN_OR_PATTERNS,
249 "a wildcard pattern used with others patterns in same match arm"
252 declare_clippy_lint! {
253 /// **What it does:** Checks for matches being used to destructure a single-variant enum
254 /// or tuple struct where a `let` will suffice.
256 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
258 /// **Known problems:** None.
266 /// let wrapper = Wrapper::Data(42);
268 /// let data = match wrapper {
269 /// Wrapper::Data(i) => i,
273 /// The correct use would be:
279 /// let wrapper = Wrapper::Data(42);
280 /// let Wrapper::Data(data) = wrapper;
282 pub INFALLIBLE_DESTRUCTURING_MATCH,
284 "a `match` statement with a single infallible arm instead of a `let`"
287 declare_clippy_lint! {
288 /// **What it does:** Checks for useless match that binds to only one value.
290 /// **Why is this bad?** Readability and needless complexity.
292 /// **Known problems:** Suggested replacements may be incorrect when `match`
293 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
308 /// let (c, d) = (a, b);
310 pub MATCH_SINGLE_BINDING,
312 "a match with a single binding instead of using `let` statement"
315 declare_clippy_lint! {
316 /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
318 /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after
319 /// matching all enum variants explicitly.
321 /// **Known problems:** None.
325 /// # struct A { a: i32 }
326 /// let a = A { a: 5 };
330 /// A { a: 5, .. } => {},
336 /// A { a: 5 } => {},
340 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
342 "a match on a struct that binds all fields but still uses the wildcard pattern"
347 infallible_destructuring_match_linted: bool,
350 impl_lint_pass!(Matches => [
355 MATCH_OVERLAPPING_ARM,
358 WILDCARD_ENUM_MATCH_ARM,
359 WILDCARD_IN_OR_PATTERNS,
360 MATCH_SINGLE_BINDING,
361 INFALLIBLE_DESTRUCTURING_MATCH,
362 REST_PAT_IN_FULLY_BOUND_STRUCTS
365 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
366 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
367 if in_external_macro(cx.sess(), expr.span) {
370 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
371 check_single_match(cx, ex, arms, expr);
372 check_match_bool(cx, ex, arms, expr);
373 check_overlapping_arms(cx, ex, arms);
374 check_wild_err_arm(cx, ex, arms);
375 check_wild_enum_match(cx, ex, arms);
376 check_match_as_ref(cx, ex, arms, expr);
377 check_wild_in_or_pats(cx, arms);
379 if self.infallible_destructuring_match_linted {
380 self.infallible_destructuring_match_linted = false;
382 check_match_single_binding(cx, ex, arms, expr);
385 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
386 check_match_ref_pats(cx, ex, arms, expr);
390 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
392 if let Some(ref expr) = local.init;
393 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
394 if arms.len() == 1 && arms[0].guard.is_none();
395 if let PatKind::TupleStruct(
396 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
398 if let Some(arg) = get_arg_name(&args[0]);
399 let body = remove_blocks(&arms[0].body);
400 if match_var(body, arg);
403 let mut applicability = Applicability::MachineApplicable;
404 self.infallible_destructuring_match_linted = true;
407 INFALLIBLE_DESTRUCTURING_MATCH,
409 "you seem to be trying to use `match` to destructure a single infallible pattern. \
410 Consider using `let`",
414 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
415 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
416 snippet_with_applicability(cx, target.span, "..", &mut applicability),
424 fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) {
426 if let PatKind::Struct(ref qpath, fields, true) = pat.kind;
427 if let QPath::Resolved(_, ref path) = qpath;
428 if let Some(def_id) = path.res.opt_def_id();
429 let ty = cx.tcx.type_of(def_id);
430 if let ty::Adt(def, _) = ty.kind;
431 if def.is_struct() || def.is_union();
432 if fields.len() == def.non_enum_variant().fields.len();
437 REST_PAT_IN_FULLY_BOUND_STRUCTS,
439 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
440 "consider removing `..` from this binding",
448 fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
449 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
450 if in_macro(expr.span) {
451 // Don't lint match expressions present in
452 // macro_rules! block
455 if let PatKind::Or(..) = arms[0].pat.kind {
456 // don't lint for or patterns for now, this makes
457 // the lint noisy in unnecessary situations
460 let els = remove_blocks(&arms[1].body);
461 let els = if is_unit_expr(els) {
463 } else if let ExprKind::Block(_, _) = els.kind {
464 // matches with blocks that contain statements are prettier as `if let + else`
467 // allow match arms with just expressions
470 let ty = cx.tables.expr_ty(ex);
471 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
472 check_single_match_single_pattern(cx, ex, arms, expr, els);
473 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
478 fn check_single_match_single_pattern(
479 cx: &LateContext<'_, '_>,
483 els: Option<&Expr<'_>>,
485 if is_wild(&arms[1].pat) {
486 report_single_match_single_pattern(cx, ex, arms, expr, els);
490 fn report_single_match_single_pattern(
491 cx: &LateContext<'_, '_>,
495 els: Option<&Expr<'_>>,
497 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
498 let els_str = els.map_or(String::new(), |els| {
499 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
505 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
509 "if let {} = {} {}{}",
510 snippet(cx, arms[0].pat.span, ".."),
511 snippet(cx, ex.span, ".."),
512 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
515 Applicability::HasPlaceholders,
519 fn check_single_match_opt_like(
520 cx: &LateContext<'_, '_>,
525 els: Option<&Expr<'_>>,
527 // list of candidate `Enum`s we know will never get any more members
529 (&paths::COW, "Borrowed"),
530 (&paths::COW, "Cow::Borrowed"),
531 (&paths::COW, "Cow::Owned"),
532 (&paths::COW, "Owned"),
533 (&paths::OPTION, "None"),
534 (&paths::RESULT, "Err"),
535 (&paths::RESULT, "Ok"),
538 let path = match arms[1].pat.kind {
539 PatKind::TupleStruct(ref path, ref inner, _) => {
540 // Contains any non wildcard patterns (e.g., `Err(err)`)?
541 if !inner.iter().all(is_wild) {
544 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
546 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
547 PatKind::Path(ref path) => {
548 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
553 for &(ty_path, pat_path) in candidates {
554 if path == *pat_path && match_type(cx, ty, ty_path) {
555 report_single_match_single_pattern(cx, ex, arms, expr, els);
560 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
561 // Type of expression is `bool`.
562 if cx.tables.expr_ty(ex).kind == ty::Bool {
567 "you seem to be trying to match on a boolean expression",
571 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
572 if let ExprKind::Lit(ref lit) = arm_bool.kind {
574 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
575 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
585 if let Some((true_expr, false_expr)) = exprs {
586 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
587 (false, false) => Some(format!(
589 snippet(cx, ex.span, "b"),
590 expr_block(cx, true_expr, None, "..", Some(expr.span)),
591 expr_block(cx, false_expr, None, "..", Some(expr.span))
593 (false, true) => Some(format!(
595 snippet(cx, ex.span, "b"),
596 expr_block(cx, true_expr, None, "..", Some(expr.span))
599 let test = Sugg::hir(cx, ex, "..");
603 expr_block(cx, false_expr, None, "..", Some(expr.span))
606 (true, true) => None,
609 if let Some(sugg) = sugg {
612 "consider using an `if`/`else` expression",
614 Applicability::HasPlaceholders,
624 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
625 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
626 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
627 let type_ranges = type_ranges(&ranges);
628 if !type_ranges.is_empty() {
629 if let Some((start, end)) = overlapping(&type_ranges) {
632 MATCH_OVERLAPPING_ARM,
634 "some ranges overlap",
636 "overlaps with this",
643 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
644 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
645 if match_type(cx, ex_ty, &paths::RESULT) {
647 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
648 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
649 if path_str == "Err" {
650 let mut matching_wild = inner.iter().any(is_wild);
651 let mut ident_bind_name = String::from("_");
653 // Looking for unused bindings (i.e.: `_e`)
654 inner.iter().for_each(|pat| {
655 if let PatKind::Binding(.., ident, None) = &pat.kind {
656 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
657 ident_bind_name = (&ident.name.as_str()).to_string();
658 matching_wild = true;
665 if let ExprKind::Block(ref block, _) = arm.body.kind;
666 if is_panic_block(block);
668 // `Err(_)` or `Err(_e)` arm with `panic!` found
669 span_lint_and_note(cx,
672 &format!("`Err({})` matches all errors", &ident_bind_name),
674 "match each error separately or use the error output",
684 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
685 let ty = cx.tables.expr_ty(ex);
687 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
688 // don't complain about not enumerating the mall.
692 // First pass - check for violation, but don't do much book-keeping because this is hopefully
693 // the uncommon case, and the book-keeping is slightly expensive.
694 let mut wildcard_span = None;
695 let mut wildcard_ident = None;
697 if let PatKind::Wild = arm.pat.kind {
698 wildcard_span = Some(arm.pat.span);
699 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
700 wildcard_span = Some(arm.pat.span);
701 wildcard_ident = Some(ident);
705 if let Some(wildcard_span) = wildcard_span {
706 // Accumulate the variants which should be put in place of the wildcard because they're not
709 let mut missing_variants = vec![];
710 if let ty::Adt(def, _) = ty.kind {
711 for variant in &def.variants {
712 missing_variants.push(variant);
717 if arm.guard.is_some() {
718 // Guards mean that this case probably isn't exhaustively covered. Technically
719 // this is incorrect, as we should really check whether each variant is exhaustively
720 // covered by the set of guards that cover it, but that's really hard to do.
723 if let PatKind::Path(ref path) = arm.pat.kind {
724 if let QPath::Resolved(_, p) = path {
725 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
727 } else if let PatKind::TupleStruct(ref path, ..) = arm.pat.kind {
728 if let QPath::Resolved(_, p) = path {
729 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
734 let mut suggestion: Vec<String> = missing_variants
737 let suffix = match v.ctor_kind {
738 CtorKind::Fn => "(..)",
739 CtorKind::Const | CtorKind::Fictive => "",
741 let ident_str = if let Some(ident) = wildcard_ident {
742 format!("{} @ ", ident.name)
746 // This path assumes that the enum type is imported into scope.
747 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
751 if suggestion.is_empty() {
755 let mut message = "wildcard match will miss any future added variants";
757 if let ty::Adt(def, _) = ty.kind {
758 if def.is_variant_list_non_exhaustive() {
759 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
760 suggestion.push(String::from("_"));
766 WILDCARD_ENUM_MATCH_ARM,
770 suggestion.join(" | "),
771 Applicability::MachineApplicable,
776 // If the block contains only a `panic!` macro (as expression or statement)
777 fn is_panic_block(block: &Block<'_>) -> bool {
778 match (&block.expr, block.stmts.len(), block.stmts.first()) {
779 (&Some(ref exp), 0, _) => {
780 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
782 (&None, 1, Some(stmt)) => {
783 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
789 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
790 if has_only_ref_pats(arms) {
791 let mut suggs = Vec::with_capacity(arms.len() + 1);
792 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
793 let span = ex.span.source_callsite();
794 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
796 "you don't need to add `&` to both the expression and the patterns",
800 let span = ex.span.source_callsite();
801 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
803 "you don't need to add `&` to all patterns",
804 "instead of prefixing all patterns with `&`, you can dereference the expression",
808 suggs.extend(arms.iter().filter_map(|a| {
809 if let PatKind::Ref(ref refp, _) = a.pat.kind {
810 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
816 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |db| {
817 if !expr.span.from_expansion() {
818 multispan_sugg(db, msg.to_owned(), suggs);
824 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
825 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
826 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
827 is_ref_some_arm(&arms[1])
828 } else if is_none_arm(&arms[1]) {
829 is_ref_some_arm(&arms[0])
833 if let Some(rb) = arm_ref {
834 let suggestion = if rb == BindingAnnotation::Ref {
840 let output_ty = cx.tables.expr_ty(expr);
841 let input_ty = cx.tables.expr_ty(ex);
843 let cast = if_chain! {
844 if let ty::Adt(_, substs) = input_ty.kind;
845 let input_ty = substs.type_at(0);
846 if let ty::Adt(_, substs) = output_ty.kind;
847 let output_ty = substs.type_at(0);
848 if let ty::Ref(_, output_ty, _) = output_ty.kind;
849 if input_ty != output_ty;
857 let mut applicability = Applicability::MachineApplicable;
862 &format!("use `{}()` instead", suggestion),
866 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
876 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
878 if let PatKind::Or(ref fields) = arm.pat.kind {
879 // look for multiple fields in this arm that contains at least one Wild pattern
880 if fields.len() > 1 && fields.iter().any(is_wild) {
883 WILDCARD_IN_OR_PATTERNS,
885 "wildcard pattern covers any other pattern as it will match anyway.",
886 "Consider handling `_` separately.",
893 fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
894 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
897 let matched_vars = ex.span;
898 let bind_names = arms[0].pat.span;
899 let match_body = remove_blocks(&arms[0].body);
900 let mut snippet_body = if match_body.span.from_expansion() {
901 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
903 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
906 // Do we need to add ';' to suggestion ?
907 match match_body.kind {
908 ExprKind::Block(block, _) => {
909 // macro + expr_ty(body) == ()
910 if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() {
911 snippet_body.push(';');
915 // expr_ty(body) == ()
916 if cx.tables.expr_ty(&match_body).is_unit() {
917 snippet_body.push(';');
922 let mut applicability = Applicability::MaybeIncorrect;
923 match arms[0].pat.kind {
924 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
925 // If this match is in a local (`let`) stmt
926 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
928 parent_let_node.span,
930 "let {} = {};\n{}let {} = {};",
931 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
932 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
933 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
934 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
939 // If we are in closure, we need curly braces around suggestion
940 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
941 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
942 if let Some(parent_expr) = get_parent_expr(cx, expr) {
943 if let ExprKind::Closure(..) = parent_expr.kind {
944 cbrace_end = format!("\n{}}}", indent);
945 // Fix body indent due to the closure
946 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
947 cbrace_start = format!("{{\n{}", indent);
953 "{}let {} = {};\n{}{}{}",
955 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
956 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
965 MATCH_SINGLE_BINDING,
967 "this match could be written as a `let` statement",
968 "consider using `let` statement",
976 MATCH_SINGLE_BINDING,
978 "this match could be replaced by its body itself",
979 "consider using the match body instead",
981 Applicability::MachineApplicable,
988 /// Returns true if the `ex` match expression is in a local (`let`) statement
989 fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
991 let map = &cx.tcx.hir();
992 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
993 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
995 return Some(parent_let_expr);
1001 /// Gets all arms that are unbounded `PatRange`s.
1002 fn all_ranges<'a, 'tcx>(
1003 cx: &LateContext<'a, 'tcx>,
1004 arms: &'tcx [Arm<'_>],
1006 ) -> Vec<SpannedRange<Constant>> {
1010 ref pat, guard: None, ..
1013 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1014 let lhs = match lhs {
1015 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
1016 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1018 let rhs = match rhs {
1019 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
1020 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1022 let rhs = match range_end {
1023 RangeEnd::Included => Bound::Included(rhs),
1024 RangeEnd::Excluded => Bound::Excluded(rhs),
1026 return Some(SpannedRange {
1032 if let PatKind::Lit(ref value) = pat.kind {
1033 let value = constant(cx, cx.tables, value)?.0;
1034 return Some(SpannedRange {
1036 node: (value.clone(), Bound::Included(value)),
1045 #[derive(Debug, Eq, PartialEq)]
1046 pub struct SpannedRange<T> {
1048 pub node: (T, Bound<T>),
1051 type TypedRanges = Vec<SpannedRange<u128>>;
1053 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1054 /// and other types than
1055 /// `Uint` and `Int` probably don't make sense.
1056 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1059 .filter_map(|range| match range.node {
1060 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1062 node: (start, Bound::Included(end)),
1064 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1066 node: (start, Bound::Excluded(end)),
1068 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1070 node: (start, Bound::Unbounded),
1077 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1079 ExprKind::Tup(ref v) if v.is_empty() => true,
1080 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1085 // Checks if arm has the form `None => None`
1086 fn is_none_arm(arm: &Arm<'_>) -> bool {
1087 match arm.pat.kind {
1088 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
1093 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1094 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1096 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1097 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1098 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1099 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1100 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1101 if let ExprKind::Path(ref some_path) = e.kind;
1102 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1103 if let ExprKind::Path(ref qpath) = args[0].kind;
1104 if let &QPath::Resolved(_, ref path2) = qpath;
1105 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1113 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1118 PatKind::Ref(..) => Some(true), // &-patterns
1119 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1120 _ => None, // any other pattern is not fine
1123 .collect::<Option<Vec<bool>>>();
1124 // look for Some(v) where there's at least one true element
1125 mapped.map_or(false, |v| v.iter().any(|el| *el))
1128 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1132 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1134 Start(T, &'a SpannedRange<T>),
1135 End(Bound<T>, &'a SpannedRange<T>),
1138 impl<'a, T: Copy> Kind<'a, T> {
1139 fn range(&self) -> &'a SpannedRange<T> {
1141 Kind::Start(_, r) | Kind::End(_, r) => r,
1145 fn value(self) -> Bound<T> {
1147 Kind::Start(t, _) => Bound::Included(t),
1148 Kind::End(t, _) => t,
1153 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1154 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1155 Some(self.cmp(other))
1159 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1160 fn cmp(&self, other: &Self) -> Ordering {
1161 match (self.value(), other.value()) {
1162 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1163 // Range patterns cannot be unbounded (yet)
1164 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1165 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1166 Ordering::Equal => Ordering::Greater,
1169 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1170 Ordering::Equal => Ordering::Less,
1177 let mut values = Vec::with_capacity(2 * ranges.len());
1180 values.push(Kind::Start(r.node.0, r));
1181 values.push(Kind::End(r.node.1, r));
1186 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1188 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1189 if ra.node != rb.node {
1190 return Some((ra, rb));
1193 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1194 _ => return Some((a.range(), b.range())),
1202 fn test_overlapping() {
1203 use rustc_span::source_map::DUMMY_SP;
1205 let sp = |s, e| SpannedRange {
1210 assert_eq!(None, overlapping::<u8>(&[]));
1211 assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))]));
1214 overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))])
1219 sp(1, Bound::Included(4)),
1220 sp(5, Bound::Included(6)),
1221 sp(10, Bound::Included(11))
1225 Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))),
1226 overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))])
1229 Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))),
1231 sp(1, Bound::Included(4)),
1232 sp(5, Bound::Included(6)),
1233 sp(6, Bound::Included(11))