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, in_macro, indent_of, is_allowed, is_expn_of, is_refutable, is_wild, match_qpath,
7 match_type, match_var, multispan_sugg, remove_blocks, snippet, snippet_block, snippet_with_applicability,
8 span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, walk_ptrs_ty,
10 use if_chain::if_chain;
11 use rustc::lint::in_external_macro;
12 use rustc::ty::{self, Ty};
13 use rustc_ast::ast::LitKind;
14 use rustc_errors::Applicability;
15 use rustc_hir::def::CtorKind;
17 print, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat,
18 PatKind, QPath, RangeEnd,
20 use rustc_lint::{LateContext, LateLintPass, LintContext};
21 use rustc_session::{declare_tool_lint, impl_lint_pass};
22 use rustc_span::source_map::Span;
23 use std::cmp::Ordering;
24 use std::collections::Bound;
26 declare_clippy_lint! {
27 /// **What it does:** Checks for matches with a single arm where an `if let`
28 /// will usually suffice.
30 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
32 /// **Known problems:** None.
36 /// # fn bar(stool: &str) {}
37 /// # let x = Some("abc");
39 /// Some(ref foo) => bar(foo),
45 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
48 declare_clippy_lint! {
49 /// **What it does:** Checks for matches with two arms where an `if let else` will
52 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
54 /// **Known problems:** Personal style preferences may differ.
61 /// # fn bar(foo: &usize) {}
62 /// # let other_ref: usize = 1;
63 /// # let x: Option<&usize> = Some(&1);
65 /// Some(ref foo) => bar(foo),
66 /// _ => bar(&other_ref),
70 /// Using `if let` with `else`:
73 /// # fn bar(foo: &usize) {}
74 /// # let other_ref: usize = 1;
75 /// # let x: Option<&usize> = Some(&1);
76 /// if let Some(ref foo) = x {
82 pub SINGLE_MATCH_ELSE,
84 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
87 declare_clippy_lint! {
88 /// **What it does:** Checks for matches where all arms match a reference,
89 /// suggesting to remove the reference and deref the matched expression
90 /// instead. It also checks for `if let &foo = bar` blocks.
92 /// **Why is this bad?** It just makes the code less readable. That reference
93 /// destructuring adds nothing to the code.
95 /// **Known problems:** None.
100 /// &A(ref y) => foo(y),
107 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
110 declare_clippy_lint! {
111 /// **What it does:** Checks for matches where match expression is a `bool`. It
112 /// suggests to replace the expression with an `if...else` block.
114 /// **Why is this bad?** It makes the code less readable.
116 /// **Known problems:** None.
122 /// let condition: bool = true;
123 /// match condition {
128 /// Use if/else instead:
132 /// let condition: bool = true;
141 "a `match` on a boolean expression instead of an `if..else` block"
144 declare_clippy_lint! {
145 /// **What it does:** Checks for overlapping match arms.
147 /// **Why is this bad?** It is likely to be an error and if not, makes the code
150 /// **Known problems:** None.
156 /// 1...10 => println!("1 ... 10"),
157 /// 5...15 => println!("5 ... 15"),
161 pub MATCH_OVERLAPPING_ARM,
163 "a `match` with overlapping arms"
166 declare_clippy_lint! {
167 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
168 /// and take drastic actions like `panic!`.
170 /// **Why is this bad?** It is generally a bad practice, just like
171 /// catching all exceptions in java with `catch(Exception)`
173 /// **Known problems:** None.
177 /// let x: Result<i32, &str> = Ok(3);
179 /// Ok(_) => println!("ok"),
180 /// Err(_) => panic!("err"),
183 pub MATCH_WILD_ERR_ARM,
185 "a `match` with `Err(_)` arm and take drastic actions"
188 declare_clippy_lint! {
189 /// **What it does:** Checks for match which is used to add a reference to an
192 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
194 /// **Known problems:** None.
198 /// let x: Option<()> = None;
199 /// let r: Option<&()> = match x {
201 /// Some(ref v) => Some(v),
206 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
209 declare_clippy_lint! {
210 /// **What it does:** Checks for wildcard enum matches using `_`.
212 /// **Why is this bad?** New enum variants added by library updates can be missed.
214 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
215 /// variants, and also may not use correct path to enum if it's not present in the current scope.
219 /// # enum Foo { A(usize), B(usize) }
220 /// # let x = Foo::B(1);
226 pub WILDCARD_ENUM_MATCH_ARM,
228 "a wildcard enum match arm using `_`"
231 declare_clippy_lint! {
232 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
234 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
235 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
237 /// **Known problems:** None.
246 pub WILDCARD_IN_OR_PATTERNS,
248 "a wildcard pattern used with others patterns in same match arm"
251 declare_clippy_lint! {
252 /// **What it does:** Checks for matches being used to destructure a single-variant enum
253 /// or tuple struct where a `let` will suffice.
255 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
257 /// **Known problems:** None.
265 /// let wrapper = Wrapper::Data(42);
267 /// let data = match wrapper {
268 /// Wrapper::Data(i) => i,
272 /// The correct use would be:
278 /// let wrapper = Wrapper::Data(42);
279 /// let Wrapper::Data(data) = wrapper;
281 pub INFALLIBLE_DESTRUCTURING_MATCH,
283 "a `match` statement with a single infallible arm instead of a `let`"
286 declare_clippy_lint! {
287 /// **What it does:** Checks for useless match that binds to only one value.
289 /// **Why is this bad?** Readability and needless complexity.
291 /// **Known problems:** Suggested replacements may be incorrect when `match`
292 /// is actually binding temporary value, bringing a 'dropped while borrowed' error.
307 /// let (c, d) = (a, b);
309 pub MATCH_SINGLE_BINDING,
311 "a match with a single binding instead of using `let` statement"
314 declare_clippy_lint! {
315 /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched.
317 /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after
318 /// matching all enum variants explicitly.
320 /// **Known problems:** None.
324 /// # struct A { a: i32 }
325 /// let a = A { a: 5 };
329 /// A { a: 5, .. } => {},
335 /// A { a: 5 } => {},
339 pub REST_PAT_IN_FULLY_BOUND_STRUCTS,
341 "a match on a struct that binds all fields but still uses the wildcard pattern"
346 infallible_destructuring_match_linted: bool,
349 impl_lint_pass!(Matches => [
354 MATCH_OVERLAPPING_ARM,
357 WILDCARD_ENUM_MATCH_ARM,
358 WILDCARD_IN_OR_PATTERNS,
359 MATCH_SINGLE_BINDING,
360 INFALLIBLE_DESTRUCTURING_MATCH,
361 REST_PAT_IN_FULLY_BOUND_STRUCTS
364 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
365 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
366 if in_external_macro(cx.sess(), expr.span) {
369 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
370 check_single_match(cx, ex, arms, expr);
371 check_match_bool(cx, ex, arms, expr);
372 check_overlapping_arms(cx, ex, arms);
373 check_wild_err_arm(cx, ex, arms);
374 check_wild_enum_match(cx, ex, arms);
375 check_match_as_ref(cx, ex, arms, expr);
376 check_wild_in_or_pats(cx, arms);
378 if self.infallible_destructuring_match_linted {
379 self.infallible_destructuring_match_linted = false;
381 check_match_single_binding(cx, ex, arms, expr);
384 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
385 check_match_ref_pats(cx, ex, arms, expr);
389 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
391 if let Some(ref expr) = local.init;
392 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
393 if arms.len() == 1 && arms[0].guard.is_none();
394 if let PatKind::TupleStruct(
395 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
397 if let Some(arg) = get_arg_name(&args[0]);
398 let body = remove_blocks(&arms[0].body);
399 if match_var(body, arg);
402 let mut applicability = Applicability::MachineApplicable;
403 self.infallible_destructuring_match_linted = true;
406 INFALLIBLE_DESTRUCTURING_MATCH,
408 "you seem to be trying to use `match` to destructure a single infallible pattern. \
409 Consider using `let`",
413 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
414 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
415 snippet_with_applicability(cx, target.span, "..", &mut applicability),
423 fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) {
425 if let PatKind::Struct(ref qpath, fields, true) = pat.kind;
426 if let QPath::Resolved(_, ref path) = qpath;
427 if let Some(def_id) = path.res.opt_def_id();
428 let ty = cx.tcx.type_of(def_id);
429 if let ty::Adt(def, _) = ty.kind;
430 if def.is_struct() || def.is_union();
431 if fields.len() == def.non_enum_variant().fields.len();
436 REST_PAT_IN_FULLY_BOUND_STRUCTS,
438 "unnecessary use of `..` pattern in struct binding. All fields were already bound",
439 "consider removing `..` from this binding",
447 fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
448 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
449 if let PatKind::Or(..) = arms[0].pat.kind {
450 // don't lint for or patterns for now, this makes
451 // the lint noisy in unnecessary situations
454 let els = remove_blocks(&arms[1].body);
455 let els = if is_unit_expr(els) {
457 } else if let ExprKind::Block(_, _) = els.kind {
458 // matches with blocks that contain statements are prettier as `if let + else`
461 // allow match arms with just expressions
464 let ty = cx.tables.expr_ty(ex);
465 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
466 check_single_match_single_pattern(cx, ex, arms, expr, els);
467 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
472 fn check_single_match_single_pattern(
473 cx: &LateContext<'_, '_>,
477 els: Option<&Expr<'_>>,
479 if is_wild(&arms[1].pat) {
480 report_single_match_single_pattern(cx, ex, arms, expr, els);
484 fn report_single_match_single_pattern(
485 cx: &LateContext<'_, '_>,
489 els: Option<&Expr<'_>>,
491 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
492 let els_str = els.map_or(String::new(), |els| {
493 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
499 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
503 "if let {} = {} {}{}",
504 snippet(cx, arms[0].pat.span, ".."),
505 snippet(cx, ex.span, ".."),
506 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
509 Applicability::HasPlaceholders,
513 fn check_single_match_opt_like(
514 cx: &LateContext<'_, '_>,
519 els: Option<&Expr<'_>>,
521 // list of candidate `Enum`s we know will never get any more members
523 (&paths::COW, "Borrowed"),
524 (&paths::COW, "Cow::Borrowed"),
525 (&paths::COW, "Cow::Owned"),
526 (&paths::COW, "Owned"),
527 (&paths::OPTION, "None"),
528 (&paths::RESULT, "Err"),
529 (&paths::RESULT, "Ok"),
532 let path = match arms[1].pat.kind {
533 PatKind::TupleStruct(ref path, ref inner, _) => {
534 // Contains any non wildcard patterns (e.g., `Err(err)`)?
535 if !inner.iter().all(is_wild) {
538 print::to_string(print::NO_ANN, |s| s.print_qpath(path, false))
540 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
541 PatKind::Path(ref path) => print::to_string(print::NO_ANN, |s| s.print_qpath(path, false)),
545 for &(ty_path, pat_path) in candidates {
546 if path == *pat_path && match_type(cx, ty, ty_path) {
547 report_single_match_single_pattern(cx, ex, arms, expr, els);
552 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
553 // Type of expression is `bool`.
554 if cx.tables.expr_ty(ex).kind == ty::Bool {
559 "you seem to be trying to match on a boolean expression",
563 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
564 if let ExprKind::Lit(ref lit) = arm_bool.kind {
566 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
567 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
577 if let Some((true_expr, false_expr)) = exprs {
578 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
579 (false, false) => Some(format!(
581 snippet(cx, ex.span, "b"),
582 expr_block(cx, true_expr, None, "..", Some(expr.span)),
583 expr_block(cx, false_expr, None, "..", Some(expr.span))
585 (false, true) => Some(format!(
587 snippet(cx, ex.span, "b"),
588 expr_block(cx, true_expr, None, "..", Some(expr.span))
591 let test = Sugg::hir(cx, ex, "..");
595 expr_block(cx, false_expr, None, "..", Some(expr.span))
598 (true, true) => None,
601 if let Some(sugg) = sugg {
604 "consider using an `if`/`else` expression",
606 Applicability::HasPlaceholders,
616 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
617 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
618 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
619 let type_ranges = type_ranges(&ranges);
620 if !type_ranges.is_empty() {
621 if let Some((start, end)) = overlapping(&type_ranges) {
624 MATCH_OVERLAPPING_ARM,
626 "some ranges overlap",
628 "overlaps with this",
635 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
636 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
637 if match_type(cx, ex_ty, &paths::RESULT) {
639 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
640 let path_str = print::to_string(print::NO_ANN, |s| s.print_qpath(path, false));
641 if path_str == "Err" {
642 let mut matching_wild = inner.iter().any(is_wild);
643 let mut ident_bind_name = String::from("_");
645 // Looking for unused bindings (i.e.: `_e`)
646 inner.iter().for_each(|pat| {
647 if let PatKind::Binding(.., ident, None) = &pat.kind {
648 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
649 ident_bind_name = (&ident.name.as_str()).to_string();
650 matching_wild = true;
657 if let ExprKind::Block(ref block, _) = arm.body.kind;
658 if is_panic_block(block);
660 // `Err(_)` or `Err(_e)` arm with `panic!` found
661 span_lint_and_note(cx,
664 &format!("`Err({})` matches all errors", &ident_bind_name),
666 "match each error separately or use the error output",
676 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
677 let ty = cx.tables.expr_ty(ex);
679 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
680 // don't complain about not enumerating the mall.
684 // First pass - check for violation, but don't do much book-keeping because this is hopefully
685 // the uncommon case, and the book-keeping is slightly expensive.
686 let mut wildcard_span = None;
687 let mut wildcard_ident = None;
689 if let PatKind::Wild = arm.pat.kind {
690 wildcard_span = Some(arm.pat.span);
691 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
692 wildcard_span = Some(arm.pat.span);
693 wildcard_ident = Some(ident);
697 if let Some(wildcard_span) = wildcard_span {
698 // Accumulate the variants which should be put in place of the wildcard because they're not
701 let mut missing_variants = vec![];
702 if let ty::Adt(def, _) = ty.kind {
703 for variant in &def.variants {
704 missing_variants.push(variant);
709 if arm.guard.is_some() {
710 // Guards mean that this case probably isn't exhaustively covered. Technically
711 // this is incorrect, as we should really check whether each variant is exhaustively
712 // covered by the set of guards that cover it, but that's really hard to do.
715 if let PatKind::Path(ref path) = arm.pat.kind {
716 if let QPath::Resolved(_, p) = path {
717 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
719 } else if let PatKind::TupleStruct(ref path, ..) = arm.pat.kind {
720 if let QPath::Resolved(_, p) = path {
721 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
726 let mut suggestion: Vec<String> = missing_variants
729 let suffix = match v.ctor_kind {
730 CtorKind::Fn => "(..)",
731 CtorKind::Const | CtorKind::Fictive => "",
733 let ident_str = if let Some(ident) = wildcard_ident {
734 format!("{} @ ", ident.name)
738 // This path assumes that the enum type is imported into scope.
739 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
743 if suggestion.is_empty() {
747 let mut message = "wildcard match will miss any future added variants";
749 if let ty::Adt(def, _) = ty.kind {
750 if def.is_variant_list_non_exhaustive() {
751 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
752 suggestion.push(String::from("_"));
758 WILDCARD_ENUM_MATCH_ARM,
762 suggestion.join(" | "),
763 Applicability::MachineApplicable,
768 // If the block contains only a `panic!` macro (as expression or statement)
769 fn is_panic_block(block: &Block<'_>) -> bool {
770 match (&block.expr, block.stmts.len(), block.stmts.first()) {
771 (&Some(ref exp), 0, _) => {
772 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
774 (&None, 1, Some(stmt)) => {
775 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
781 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
782 if has_only_ref_pats(arms) {
783 let mut suggs = Vec::with_capacity(arms.len() + 1);
784 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
785 let span = ex.span.source_callsite();
786 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
788 "you don't need to add `&` to both the expression and the patterns",
792 let span = ex.span.source_callsite();
793 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
795 "you don't need to add `&` to all patterns",
796 "instead of prefixing all patterns with `&`, you can dereference the expression",
800 suggs.extend(arms.iter().filter_map(|a| {
801 if let PatKind::Ref(ref refp, _) = a.pat.kind {
802 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
808 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |db| {
809 if !expr.span.from_expansion() {
810 multispan_sugg(db, msg.to_owned(), suggs);
816 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
817 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
818 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
819 is_ref_some_arm(&arms[1])
820 } else if is_none_arm(&arms[1]) {
821 is_ref_some_arm(&arms[0])
825 if let Some(rb) = arm_ref {
826 let suggestion = if rb == BindingAnnotation::Ref {
832 let output_ty = cx.tables.expr_ty(expr);
833 let input_ty = cx.tables.expr_ty(ex);
835 let cast = if_chain! {
836 if let ty::Adt(_, substs) = input_ty.kind;
837 let input_ty = substs.type_at(0);
838 if let ty::Adt(_, substs) = output_ty.kind;
839 let output_ty = substs.type_at(0);
840 if let ty::Ref(_, output_ty, _) = output_ty.kind;
841 if input_ty != output_ty;
849 let mut applicability = Applicability::MachineApplicable;
854 &format!("use `{}()` instead", suggestion),
858 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
868 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
870 if let PatKind::Or(ref fields) = arm.pat.kind {
871 // look for multiple fields in this arm that contains at least one Wild pattern
872 if fields.len() > 1 && fields.iter().any(is_wild) {
875 WILDCARD_IN_OR_PATTERNS,
877 "wildcard pattern covers any other pattern as it will match anyway.",
878 "Consider handling `_` separately.",
885 fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
886 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
889 let matched_vars = ex.span;
890 let bind_names = arms[0].pat.span;
891 let match_body = remove_blocks(&arms[0].body);
892 let mut snippet_body = if match_body.span.from_expansion() {
893 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
895 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
898 // Do we need to add ';' to suggestion ?
899 match match_body.kind {
900 ExprKind::Block(block, _) => {
901 // macro + expr_ty(body) == ()
902 if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() {
903 snippet_body.push(';');
907 // expr_ty(body) == ()
908 if cx.tables.expr_ty(&match_body).is_unit() {
909 snippet_body.push(';');
914 let mut applicability = Applicability::MaybeIncorrect;
915 match arms[0].pat.kind {
916 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
917 // If this match is in a local (`let`) stmt
918 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
920 parent_let_node.span,
922 "let {} = {};\n{}let {} = {};",
923 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
924 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
925 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
926 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
934 "let {} = {};\n{}{}",
935 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
936 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
937 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
944 MATCH_SINGLE_BINDING,
946 "this match could be written as a `let` statement",
947 "consider using `let` statement",
955 MATCH_SINGLE_BINDING,
957 "this match could be replaced by its body itself",
958 "consider using the match body instead",
960 Applicability::MachineApplicable,
967 /// Returns true if the `ex` match expression is in a local (`let`) statement
968 fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
970 let map = &cx.tcx.hir();
971 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
972 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
974 return Some(parent_let_expr);
980 /// Gets all arms that are unbounded `PatRange`s.
981 fn all_ranges<'a, 'tcx>(
982 cx: &LateContext<'a, 'tcx>,
983 arms: &'tcx [Arm<'_>],
985 ) -> Vec<SpannedRange<Constant>> {
989 ref pat, guard: None, ..
992 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
993 let lhs = match lhs {
994 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
995 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
997 let rhs = match rhs {
998 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
999 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1001 let rhs = match range_end {
1002 RangeEnd::Included => Bound::Included(rhs),
1003 RangeEnd::Excluded => Bound::Excluded(rhs),
1005 return Some(SpannedRange {
1011 if let PatKind::Lit(ref value) = pat.kind {
1012 let value = constant(cx, cx.tables, value)?.0;
1013 return Some(SpannedRange {
1015 node: (value.clone(), Bound::Included(value)),
1024 #[derive(Debug, Eq, PartialEq)]
1025 pub struct SpannedRange<T> {
1027 pub node: (T, Bound<T>),
1030 type TypedRanges = Vec<SpannedRange<u128>>;
1032 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1033 /// and other types than
1034 /// `Uint` and `Int` probably don't make sense.
1035 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1038 .filter_map(|range| match range.node {
1039 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1041 node: (start, Bound::Included(end)),
1043 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1045 node: (start, Bound::Excluded(end)),
1047 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1049 node: (start, Bound::Unbounded),
1056 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1058 ExprKind::Tup(ref v) if v.is_empty() => true,
1059 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1064 // Checks if arm has the form `None => None`
1065 fn is_none_arm(arm: &Arm<'_>) -> bool {
1066 match arm.pat.kind {
1067 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
1072 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1073 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1075 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1076 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1077 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1078 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1079 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1080 if let ExprKind::Path(ref some_path) = e.kind;
1081 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1082 if let ExprKind::Path(ref qpath) = args[0].kind;
1083 if let &QPath::Resolved(_, ref path2) = qpath;
1084 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1092 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1097 PatKind::Ref(..) => Some(true), // &-patterns
1098 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1099 _ => None, // any other pattern is not fine
1102 .collect::<Option<Vec<bool>>>();
1103 // look for Some(v) where there's at least one true element
1104 mapped.map_or(false, |v| v.iter().any(|el| *el))
1107 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1111 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1113 Start(T, &'a SpannedRange<T>),
1114 End(Bound<T>, &'a SpannedRange<T>),
1117 impl<'a, T: Copy> Kind<'a, T> {
1118 fn range(&self) -> &'a SpannedRange<T> {
1120 Kind::Start(_, r) | Kind::End(_, r) => r,
1124 fn value(self) -> Bound<T> {
1126 Kind::Start(t, _) => Bound::Included(t),
1127 Kind::End(t, _) => t,
1132 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1133 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1134 Some(self.cmp(other))
1138 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1139 fn cmp(&self, other: &Self) -> Ordering {
1140 match (self.value(), other.value()) {
1141 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1142 // Range patterns cannot be unbounded (yet)
1143 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1144 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1145 Ordering::Equal => Ordering::Greater,
1148 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1149 Ordering::Equal => Ordering::Less,
1156 let mut values = Vec::with_capacity(2 * ranges.len());
1159 values.push(Kind::Start(r.node.0, r));
1160 values.push(Kind::End(r.node.1, r));
1165 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1167 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1168 if ra.node != rb.node {
1169 return Some((ra, rb));
1172 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1173 _ => return Some((a.range(), b.range())),