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 let PatKind::Or(..) = arms[0].pat.kind {
451 // don't lint for or patterns for now, this makes
452 // the lint noisy in unnecessary situations
455 let els = remove_blocks(&arms[1].body);
456 let els = if is_unit_expr(els) {
458 } else if let ExprKind::Block(_, _) = els.kind {
459 // matches with blocks that contain statements are prettier as `if let + else`
462 // allow match arms with just expressions
465 let ty = cx.tables.expr_ty(ex);
466 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
467 check_single_match_single_pattern(cx, ex, arms, expr, els);
468 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
473 fn check_single_match_single_pattern(
474 cx: &LateContext<'_, '_>,
478 els: Option<&Expr<'_>>,
480 if is_wild(&arms[1].pat) {
481 report_single_match_single_pattern(cx, ex, arms, expr, els);
485 fn report_single_match_single_pattern(
486 cx: &LateContext<'_, '_>,
490 els: Option<&Expr<'_>>,
492 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
493 let els_str = els.map_or(String::new(), |els| {
494 format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span)))
500 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
504 "if let {} = {} {}{}",
505 snippet(cx, arms[0].pat.span, ".."),
506 snippet(cx, ex.span, ".."),
507 expr_block(cx, &arms[0].body, None, "..", Some(expr.span)),
510 Applicability::HasPlaceholders,
514 fn check_single_match_opt_like(
515 cx: &LateContext<'_, '_>,
520 els: Option<&Expr<'_>>,
522 // list of candidate `Enum`s we know will never get any more members
524 (&paths::COW, "Borrowed"),
525 (&paths::COW, "Cow::Borrowed"),
526 (&paths::COW, "Cow::Owned"),
527 (&paths::COW, "Owned"),
528 (&paths::OPTION, "None"),
529 (&paths::RESULT, "Err"),
530 (&paths::RESULT, "Ok"),
533 let path = match arms[1].pat.kind {
534 PatKind::TupleStruct(ref path, ref inner, _) => {
535 // Contains any non wildcard patterns (e.g., `Err(err)`)?
536 if !inner.iter().all(is_wild) {
539 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
541 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
542 PatKind::Path(ref path) => {
543 rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false))
548 for &(ty_path, pat_path) in candidates {
549 if path == *pat_path && match_type(cx, ty, ty_path) {
550 report_single_match_single_pattern(cx, ex, arms, expr, els);
555 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
556 // Type of expression is `bool`.
557 if cx.tables.expr_ty(ex).kind == ty::Bool {
562 "you seem to be trying to match on a boolean expression",
566 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
567 if let ExprKind::Lit(ref lit) = arm_bool.kind {
569 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
570 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
580 if let Some((true_expr, false_expr)) = exprs {
581 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
582 (false, false) => Some(format!(
584 snippet(cx, ex.span, "b"),
585 expr_block(cx, true_expr, None, "..", Some(expr.span)),
586 expr_block(cx, false_expr, None, "..", Some(expr.span))
588 (false, true) => Some(format!(
590 snippet(cx, ex.span, "b"),
591 expr_block(cx, true_expr, None, "..", Some(expr.span))
594 let test = Sugg::hir(cx, ex, "..");
598 expr_block(cx, false_expr, None, "..", Some(expr.span))
601 (true, true) => None,
604 if let Some(sugg) = sugg {
607 "consider using an `if`/`else` expression",
609 Applicability::HasPlaceholders,
619 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
620 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
621 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
622 let type_ranges = type_ranges(&ranges);
623 if !type_ranges.is_empty() {
624 if let Some((start, end)) = overlapping(&type_ranges) {
627 MATCH_OVERLAPPING_ARM,
629 "some ranges overlap",
631 "overlaps with this",
638 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
639 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
640 if match_type(cx, ex_ty, &paths::RESULT) {
642 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
643 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
644 if path_str == "Err" {
645 let mut matching_wild = inner.iter().any(is_wild);
646 let mut ident_bind_name = String::from("_");
648 // Looking for unused bindings (i.e.: `_e`)
649 inner.iter().for_each(|pat| {
650 if let PatKind::Binding(.., ident, None) = &pat.kind {
651 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
652 ident_bind_name = (&ident.name.as_str()).to_string();
653 matching_wild = true;
660 if let ExprKind::Block(ref block, _) = arm.body.kind;
661 if is_panic_block(block);
663 // `Err(_)` or `Err(_e)` arm with `panic!` found
664 span_lint_and_note(cx,
667 &format!("`Err({})` matches all errors", &ident_bind_name),
669 "match each error separately or use the error output",
679 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
680 let ty = cx.tables.expr_ty(ex);
682 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
683 // don't complain about not enumerating the mall.
687 // First pass - check for violation, but don't do much book-keeping because this is hopefully
688 // the uncommon case, and the book-keeping is slightly expensive.
689 let mut wildcard_span = None;
690 let mut wildcard_ident = None;
692 if let PatKind::Wild = arm.pat.kind {
693 wildcard_span = Some(arm.pat.span);
694 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
695 wildcard_span = Some(arm.pat.span);
696 wildcard_ident = Some(ident);
700 if let Some(wildcard_span) = wildcard_span {
701 // Accumulate the variants which should be put in place of the wildcard because they're not
704 let mut missing_variants = vec![];
705 if let ty::Adt(def, _) = ty.kind {
706 for variant in &def.variants {
707 missing_variants.push(variant);
712 if arm.guard.is_some() {
713 // Guards mean that this case probably isn't exhaustively covered. Technically
714 // this is incorrect, as we should really check whether each variant is exhaustively
715 // covered by the set of guards that cover it, but that's really hard to do.
718 if let PatKind::Path(ref path) = arm.pat.kind {
719 if let QPath::Resolved(_, p) = path {
720 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
722 } else if let PatKind::TupleStruct(ref path, ..) = arm.pat.kind {
723 if let QPath::Resolved(_, p) = path {
724 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
729 let mut suggestion: Vec<String> = missing_variants
732 let suffix = match v.ctor_kind {
733 CtorKind::Fn => "(..)",
734 CtorKind::Const | CtorKind::Fictive => "",
736 let ident_str = if let Some(ident) = wildcard_ident {
737 format!("{} @ ", ident.name)
741 // This path assumes that the enum type is imported into scope.
742 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
746 if suggestion.is_empty() {
750 let mut message = "wildcard match will miss any future added variants";
752 if let ty::Adt(def, _) = ty.kind {
753 if def.is_variant_list_non_exhaustive() {
754 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
755 suggestion.push(String::from("_"));
761 WILDCARD_ENUM_MATCH_ARM,
765 suggestion.join(" | "),
766 Applicability::MachineApplicable,
771 // If the block contains only a `panic!` macro (as expression or statement)
772 fn is_panic_block(block: &Block<'_>) -> bool {
773 match (&block.expr, block.stmts.len(), block.stmts.first()) {
774 (&Some(ref exp), 0, _) => {
775 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
777 (&None, 1, Some(stmt)) => {
778 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
784 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
785 if has_only_ref_pats(arms) {
786 let mut suggs = Vec::with_capacity(arms.len() + 1);
787 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
788 let span = ex.span.source_callsite();
789 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
791 "you don't need to add `&` to both the expression and the patterns",
795 let span = ex.span.source_callsite();
796 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
798 "you don't need to add `&` to all patterns",
799 "instead of prefixing all patterns with `&`, you can dereference the expression",
803 suggs.extend(arms.iter().filter_map(|a| {
804 if let PatKind::Ref(ref refp, _) = a.pat.kind {
805 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
811 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |db| {
812 if !expr.span.from_expansion() {
813 multispan_sugg(db, msg.to_owned(), suggs);
819 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
820 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
821 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
822 is_ref_some_arm(&arms[1])
823 } else if is_none_arm(&arms[1]) {
824 is_ref_some_arm(&arms[0])
828 if let Some(rb) = arm_ref {
829 let suggestion = if rb == BindingAnnotation::Ref {
835 let output_ty = cx.tables.expr_ty(expr);
836 let input_ty = cx.tables.expr_ty(ex);
838 let cast = if_chain! {
839 if let ty::Adt(_, substs) = input_ty.kind;
840 let input_ty = substs.type_at(0);
841 if let ty::Adt(_, substs) = output_ty.kind;
842 let output_ty = substs.type_at(0);
843 if let ty::Ref(_, output_ty, _) = output_ty.kind;
844 if input_ty != output_ty;
852 let mut applicability = Applicability::MachineApplicable;
857 &format!("use `{}()` instead", suggestion),
861 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
871 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
873 if let PatKind::Or(ref fields) = arm.pat.kind {
874 // look for multiple fields in this arm that contains at least one Wild pattern
875 if fields.len() > 1 && fields.iter().any(is_wild) {
878 WILDCARD_IN_OR_PATTERNS,
880 "wildcard pattern covers any other pattern as it will match anyway.",
881 "Consider handling `_` separately.",
888 fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
889 if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
892 let matched_vars = ex.span;
893 let bind_names = arms[0].pat.span;
894 let match_body = remove_blocks(&arms[0].body);
895 let mut snippet_body = if match_body.span.from_expansion() {
896 Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
898 snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
901 // Do we need to add ';' to suggestion ?
902 match match_body.kind {
903 ExprKind::Block(block, _) => {
904 // macro + expr_ty(body) == ()
905 if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() {
906 snippet_body.push(';');
910 // expr_ty(body) == ()
911 if cx.tables.expr_ty(&match_body).is_unit() {
912 snippet_body.push(';');
917 let mut applicability = Applicability::MaybeIncorrect;
918 match arms[0].pat.kind {
919 PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
920 // If this match is in a local (`let`) stmt
921 let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
923 parent_let_node.span,
925 "let {} = {};\n{}let {} = {};",
926 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
927 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
928 " ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
929 snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
934 // If we are in closure, we need curly braces around suggestion
935 let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
936 let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
937 if let Some(parent_expr) = get_parent_expr(cx, expr) {
938 if let ExprKind::Closure(..) = parent_expr.kind {
939 cbrace_end = format!("\n{}}}", indent);
940 // Fix body indent due to the closure
941 indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
942 cbrace_start = format!("{{\n{}", indent);
948 "{}let {} = {};\n{}{}{}",
950 snippet_with_applicability(cx, bind_names, "..", &mut applicability),
951 snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
960 MATCH_SINGLE_BINDING,
962 "this match could be written as a `let` statement",
963 "consider using `let` statement",
971 MATCH_SINGLE_BINDING,
973 "this match could be replaced by its body itself",
974 "consider using the match body instead",
976 Applicability::MachineApplicable,
983 /// Returns true if the `ex` match expression is in a local (`let`) statement
984 fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
986 let map = &cx.tcx.hir();
987 if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
988 if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
990 return Some(parent_let_expr);
996 /// Gets all arms that are unbounded `PatRange`s.
997 fn all_ranges<'a, 'tcx>(
998 cx: &LateContext<'a, 'tcx>,
999 arms: &'tcx [Arm<'_>],
1001 ) -> Vec<SpannedRange<Constant>> {
1005 ref pat, guard: None, ..
1008 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
1009 let lhs = match lhs {
1010 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
1011 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
1013 let rhs = match rhs {
1014 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
1015 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
1017 let rhs = match range_end {
1018 RangeEnd::Included => Bound::Included(rhs),
1019 RangeEnd::Excluded => Bound::Excluded(rhs),
1021 return Some(SpannedRange {
1027 if let PatKind::Lit(ref value) = pat.kind {
1028 let value = constant(cx, cx.tables, value)?.0;
1029 return Some(SpannedRange {
1031 node: (value.clone(), Bound::Included(value)),
1040 #[derive(Debug, Eq, PartialEq)]
1041 pub struct SpannedRange<T> {
1043 pub node: (T, Bound<T>),
1046 type TypedRanges = Vec<SpannedRange<u128>>;
1048 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
1049 /// and other types than
1050 /// `Uint` and `Int` probably don't make sense.
1051 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
1054 .filter_map(|range| match range.node {
1055 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
1057 node: (start, Bound::Included(end)),
1059 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
1061 node: (start, Bound::Excluded(end)),
1063 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
1065 node: (start, Bound::Unbounded),
1072 fn is_unit_expr(expr: &Expr<'_>) -> bool {
1074 ExprKind::Tup(ref v) if v.is_empty() => true,
1075 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
1080 // Checks if arm has the form `None => None`
1081 fn is_none_arm(arm: &Arm<'_>) -> bool {
1082 match arm.pat.kind {
1083 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
1088 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
1089 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
1091 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
1092 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
1093 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
1094 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
1095 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
1096 if let ExprKind::Path(ref some_path) = e.kind;
1097 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
1098 if let ExprKind::Path(ref qpath) = args[0].kind;
1099 if let &QPath::Resolved(_, ref path2) = qpath;
1100 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
1108 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
1113 PatKind::Ref(..) => Some(true), // &-patterns
1114 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
1115 _ => None, // any other pattern is not fine
1118 .collect::<Option<Vec<bool>>>();
1119 // look for Some(v) where there's at least one true element
1120 mapped.map_or(false, |v| v.iter().any(|el| *el))
1123 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
1127 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
1129 Start(T, &'a SpannedRange<T>),
1130 End(Bound<T>, &'a SpannedRange<T>),
1133 impl<'a, T: Copy> Kind<'a, T> {
1134 fn range(&self) -> &'a SpannedRange<T> {
1136 Kind::Start(_, r) | Kind::End(_, r) => r,
1140 fn value(self) -> Bound<T> {
1142 Kind::Start(t, _) => Bound::Included(t),
1143 Kind::End(t, _) => t,
1148 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1149 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1150 Some(self.cmp(other))
1154 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1155 fn cmp(&self, other: &Self) -> Ordering {
1156 match (self.value(), other.value()) {
1157 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1158 // Range patterns cannot be unbounded (yet)
1159 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1160 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1161 Ordering::Equal => Ordering::Greater,
1164 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1165 Ordering::Equal => Ordering::Less,
1172 let mut values = Vec::with_capacity(2 * ranges.len());
1175 values.push(Kind::Start(r.node.0, r));
1176 values.push(Kind::End(r.node.1, r));
1181 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1183 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1184 if ra.node != rb.node {
1185 return Some((ra, rb));
1188 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1189 _ => return Some((a.range(), b.range())),