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 span_lint_and_help, span_lint_and_note,
7 expr_block, in_macro, is_allowed, is_expn_of, is_wild, match_qpath, match_type, multispan_sugg, remove_blocks,
8 snippet, snippet_block, snippet_with_applicability, span_lint_and_sugg, span_lint_and_then,
10 use if_chain::if_chain;
11 use rustc::lint::in_external_macro;
12 use rustc::ty::{self, Ty};
13 use rustc_errors::Applicability;
14 use rustc_hir::def::CtorKind;
16 use rustc_lint::{LateContext, LateLintPass, LintContext};
17 use rustc_session::{declare_tool_lint, impl_lint_pass};
18 use rustc_span::source_map::Span;
19 use std::cmp::Ordering;
20 use std::collections::Bound;
21 use syntax::ast::LitKind;
23 declare_clippy_lint! {
24 /// **What it does:** Checks for matches with a single arm where an `if let`
25 /// will usually suffice.
27 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
29 /// **Known problems:** None.
33 /// # fn bar(stool: &str) {}
34 /// # let x = Some("abc");
36 /// Some(ref foo) => bar(foo),
42 "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`"
45 declare_clippy_lint! {
46 /// **What it does:** Checks for matches with two arms where an `if let else` will
49 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
51 /// **Known problems:** Personal style preferences may differ.
58 /// # fn bar(foo: &usize) {}
59 /// # let other_ref: usize = 1;
60 /// # let x: Option<&usize> = Some(&1);
62 /// Some(ref foo) => bar(foo),
63 /// _ => bar(&other_ref),
67 /// Using `if let` with `else`:
70 /// # fn bar(foo: &usize) {}
71 /// # let other_ref: usize = 1;
72 /// # let x: Option<&usize> = Some(&1);
73 /// if let Some(ref foo) = x {
79 pub SINGLE_MATCH_ELSE,
81 "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
84 declare_clippy_lint! {
85 /// **What it does:** Checks for matches where all arms match a reference,
86 /// suggesting to remove the reference and deref the matched expression
87 /// instead. It also checks for `if let &foo = bar` blocks.
89 /// **Why is this bad?** It just makes the code less readable. That reference
90 /// destructuring adds nothing to the code.
92 /// **Known problems:** None.
97 /// &A(ref y) => foo(y),
104 "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression"
107 declare_clippy_lint! {
108 /// **What it does:** Checks for matches where match expression is a `bool`. It
109 /// suggests to replace the expression with an `if...else` block.
111 /// **Why is this bad?** It makes the code less readable.
113 /// **Known problems:** None.
119 /// let condition: bool = true;
120 /// match condition {
125 /// Use if/else instead:
129 /// let condition: bool = true;
138 "a `match` on a boolean expression instead of an `if..else` block"
141 declare_clippy_lint! {
142 /// **What it does:** Checks for overlapping match arms.
144 /// **Why is this bad?** It is likely to be an error and if not, makes the code
147 /// **Known problems:** None.
153 /// 1...10 => println!("1 ... 10"),
154 /// 5...15 => println!("5 ... 15"),
158 pub MATCH_OVERLAPPING_ARM,
160 "a `match` with overlapping arms"
163 declare_clippy_lint! {
164 /// **What it does:** Checks for arm which matches all errors with `Err(_)`
165 /// and take drastic actions like `panic!`.
167 /// **Why is this bad?** It is generally a bad practice, just like
168 /// catching all exceptions in java with `catch(Exception)`
170 /// **Known problems:** None.
174 /// let x: Result<i32, &str> = Ok(3);
176 /// Ok(_) => println!("ok"),
177 /// Err(_) => panic!("err"),
180 pub MATCH_WILD_ERR_ARM,
182 "a `match` with `Err(_)` arm and take drastic actions"
185 declare_clippy_lint! {
186 /// **What it does:** Checks for match which is used to add a reference to an
189 /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter.
191 /// **Known problems:** None.
195 /// let x: Option<()> = None;
196 /// let r: Option<&()> = match x {
198 /// Some(ref v) => Some(v),
203 "a `match` on an Option value instead of using `as_ref()` or `as_mut`"
206 declare_clippy_lint! {
207 /// **What it does:** Checks for wildcard enum matches using `_`.
209 /// **Why is this bad?** New enum variants added by library updates can be missed.
211 /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some
212 /// variants, and also may not use correct path to enum if it's not present in the current scope.
216 /// # enum Foo { A(usize), B(usize) }
217 /// # let x = Foo::B(1);
223 pub WILDCARD_ENUM_MATCH_ARM,
225 "a wildcard enum match arm using `_`"
228 declare_clippy_lint! {
229 /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm.
231 /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway.
232 /// It makes the code less readable, especially to spot wildcard pattern use in match arm.
234 /// **Known problems:** None.
243 pub WILDCARD_IN_OR_PATTERNS,
245 "a wildcard pattern used with others patterns in same match arm"
248 declare_clippy_lint! {
249 /// **What it does:** Checks for matches being used to destructure a single-variant enum
250 /// or tuple struct where a `let` will suffice.
252 /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
254 /// **Known problems:** None.
262 /// let wrapper = Wrapper::Data(42);
264 /// let data = match wrapper {
265 /// Wrapper::Data(i) => i,
269 /// The correct use would be:
275 /// let wrapper = Wrapper::Data(42);
276 /// let Wrapper::Data(data) = wrapper;
278 pub INFALLIBLE_DESTRUCTURING_MATCH,
280 "a `match` statement with a single infallible arm instead of a `let`"
283 declare_clippy_lint! {
284 /// **What it does:** Checks for useless match that binds to only one value.
286 /// **Why is this bad?** Readability and needless complexity.
288 /// **Known problems:** None.
303 /// let (c, d) = (a, b);
305 pub MATCH_SINGLE_BINDING,
307 "a match with a single binding instead of using `let` statement"
312 infallible_destructuring_match_linted: bool,
315 impl_lint_pass!(Matches => [
320 MATCH_OVERLAPPING_ARM,
323 WILDCARD_ENUM_MATCH_ARM,
324 WILDCARD_IN_OR_PATTERNS,
325 MATCH_SINGLE_BINDING,
326 INFALLIBLE_DESTRUCTURING_MATCH
329 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches {
330 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
331 if in_external_macro(cx.sess(), expr.span) {
334 if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind {
335 check_single_match(cx, ex, arms, expr);
336 check_match_bool(cx, ex, arms, expr);
337 check_overlapping_arms(cx, ex, arms);
338 check_wild_err_arm(cx, ex, arms);
339 check_wild_enum_match(cx, ex, arms);
340 check_match_as_ref(cx, ex, arms, expr);
341 check_wild_in_or_pats(cx, arms);
343 if self.infallible_destructuring_match_linted {
344 self.infallible_destructuring_match_linted = false;
346 check_match_single_binding(cx, ex, arms, expr);
349 if let ExprKind::Match(ref ex, ref arms, _) = expr.kind {
350 check_match_ref_pats(cx, ex, arms, expr);
354 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
356 if let Some(ref expr) = local.init;
357 if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind;
358 if arms.len() == 1 && arms[0].guard.is_none();
359 if let PatKind::TupleStruct(
360 QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind;
362 if let Some(arg) = get_arg_name(&args[0]);
363 let body = remove_blocks(&arms[0].body);
364 if match_var(body, arg);
367 let mut applicability = Applicability::MachineApplicable;
368 self.infallible_destructuring_match_linted = true;
371 INFALLIBLE_DESTRUCTURING_MATCH,
373 "you seem to be trying to use `match` to destructure a single infallible pattern. \
374 Consider using `let`",
378 snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
379 snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
380 snippet_with_applicability(cx, target.span, "..", &mut applicability),
390 fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
391 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
392 if let PatKind::Or(..) = arms[0].pat.kind {
393 // don't lint for or patterns for now, this makes
394 // the lint noisy in unnecessary situations
397 let els = remove_blocks(&arms[1].body);
398 let els = if is_unit_expr(els) {
400 } else if let ExprKind::Block(_, _) = els.kind {
401 // matches with blocks that contain statements are prettier as `if let + else`
404 // allow match arms with just expressions
407 let ty = cx.tables.expr_ty(ex);
408 if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) {
409 check_single_match_single_pattern(cx, ex, arms, expr, els);
410 check_single_match_opt_like(cx, ex, arms, expr, ty, els);
415 fn check_single_match_single_pattern(
416 cx: &LateContext<'_, '_>,
420 els: Option<&Expr<'_>>,
422 if is_wild(&arms[1].pat) {
423 report_single_match_single_pattern(cx, ex, arms, expr, els);
427 fn report_single_match_single_pattern(
428 cx: &LateContext<'_, '_>,
432 els: Option<&Expr<'_>>,
434 let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH };
435 let els_str = els.map_or(String::new(), |els| {
436 format!(" else {}", expr_block(cx, els, None, ".."))
442 "you seem to be trying to use match for destructuring a single pattern. Consider using `if \
446 "if let {} = {} {}{}",
447 snippet(cx, arms[0].pat.span, ".."),
448 snippet(cx, ex.span, ".."),
449 expr_block(cx, &arms[0].body, None, ".."),
452 Applicability::HasPlaceholders,
456 fn check_single_match_opt_like(
457 cx: &LateContext<'_, '_>,
462 els: Option<&Expr<'_>>,
464 // list of candidate `Enum`s we know will never get any more members
466 (&paths::COW, "Borrowed"),
467 (&paths::COW, "Cow::Borrowed"),
468 (&paths::COW, "Cow::Owned"),
469 (&paths::COW, "Owned"),
470 (&paths::OPTION, "None"),
471 (&paths::RESULT, "Err"),
472 (&paths::RESULT, "Ok"),
475 let path = match arms[1].pat.kind {
476 PatKind::TupleStruct(ref path, ref inner, _) => {
477 // Contains any non wildcard patterns (e.g., `Err(err)`)?
478 if !inner.iter().all(is_wild) {
481 print::to_string(print::NO_ANN, |s| s.print_qpath(path, false))
483 PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(),
484 PatKind::Path(ref path) => print::to_string(print::NO_ANN, |s| s.print_qpath(path, false)),
488 for &(ty_path, pat_path) in candidates {
489 if path == *pat_path && match_type(cx, ty, ty_path) {
490 report_single_match_single_pattern(cx, ex, arms, expr, els);
495 fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
496 // Type of expression is `bool`.
497 if cx.tables.expr_ty(ex).kind == ty::Bool {
502 "you seem to be trying to match on a boolean expression",
506 let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind {
507 if let ExprKind::Lit(ref lit) = arm_bool.kind {
509 LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)),
510 LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)),
520 if let Some((true_expr, false_expr)) = exprs {
521 let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) {
522 (false, false) => Some(format!(
524 snippet(cx, ex.span, "b"),
525 expr_block(cx, true_expr, None, ".."),
526 expr_block(cx, false_expr, None, "..")
528 (false, true) => Some(format!(
530 snippet(cx, ex.span, "b"),
531 expr_block(cx, true_expr, None, "..")
534 let test = Sugg::hir(cx, ex, "..");
535 Some(format!("if {} {}", !test, expr_block(cx, false_expr, None, "..")))
537 (true, true) => None,
540 if let Some(sugg) = sugg {
543 "consider using an `if`/`else` expression",
545 Applicability::HasPlaceholders,
555 fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
556 if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() {
557 let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex));
558 let type_ranges = type_ranges(&ranges);
559 if !type_ranges.is_empty() {
560 if let Some((start, end)) = overlapping(&type_ranges) {
563 MATCH_OVERLAPPING_ARM,
565 "some ranges overlap",
567 "overlaps with this",
574 fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
575 let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex));
576 if match_type(cx, ex_ty, &paths::RESULT) {
578 if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind {
579 let path_str = print::to_string(print::NO_ANN, |s| s.print_qpath(path, false));
580 if path_str == "Err" {
581 let mut matching_wild = inner.iter().any(is_wild);
582 let mut ident_bind_name = String::from("_");
584 // Looking for unused bindings (i.e.: `_e`)
585 inner.iter().for_each(|pat| {
586 if let PatKind::Binding(.., ident, None) = &pat.kind {
587 if ident.as_str().starts_with('_') && is_unused(ident, arm.body) {
588 ident_bind_name = (&ident.name.as_str()).to_string();
589 matching_wild = true;
596 if let ExprKind::Block(ref block, _) = arm.body.kind;
597 if is_panic_block(block);
599 // `Err(_)` or `Err(_e)` arm with `panic!` found
600 span_lint_and_note(cx,
603 &format!("`Err({})` matches all errors", &ident_bind_name),
605 "match each error separately or use the error output",
615 fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) {
616 let ty = cx.tables.expr_ty(ex);
618 // If there isn't a nice closed set of possible values that can be conveniently enumerated,
619 // don't complain about not enumerating the mall.
623 // First pass - check for violation, but don't do much book-keeping because this is hopefully
624 // the uncommon case, and the book-keeping is slightly expensive.
625 let mut wildcard_span = None;
626 let mut wildcard_ident = None;
628 if let PatKind::Wild = arm.pat.kind {
629 wildcard_span = Some(arm.pat.span);
630 } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind {
631 wildcard_span = Some(arm.pat.span);
632 wildcard_ident = Some(ident);
636 if let Some(wildcard_span) = wildcard_span {
637 // Accumulate the variants which should be put in place of the wildcard because they're not
640 let mut missing_variants = vec![];
641 if let ty::Adt(def, _) = ty.kind {
642 for variant in &def.variants {
643 missing_variants.push(variant);
648 if arm.guard.is_some() {
649 // Guards mean that this case probably isn't exhaustively covered. Technically
650 // this is incorrect, as we should really check whether each variant is exhaustively
651 // covered by the set of guards that cover it, but that's really hard to do.
654 if let PatKind::Path(ref path) = arm.pat.kind {
655 if let QPath::Resolved(_, p) = path {
656 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
658 } else if let PatKind::TupleStruct(ref path, ..) = arm.pat.kind {
659 if let QPath::Resolved(_, p) = path {
660 missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id()));
665 let mut suggestion: Vec<String> = missing_variants
668 let suffix = match v.ctor_kind {
669 CtorKind::Fn => "(..)",
670 CtorKind::Const | CtorKind::Fictive => "",
672 let ident_str = if let Some(ident) = wildcard_ident {
673 format!("{} @ ", ident.name)
677 // This path assumes that the enum type is imported into scope.
678 format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix)
682 if suggestion.is_empty() {
686 let mut message = "wildcard match will miss any future added variants";
688 if let ty::Adt(def, _) = ty.kind {
689 if def.is_variant_list_non_exhaustive() {
690 message = "match on non-exhaustive enum doesn't explicitly match all known variants";
691 suggestion.push(String::from("_"));
697 WILDCARD_ENUM_MATCH_ARM,
701 suggestion.join(" | "),
702 Applicability::MachineApplicable,
707 // If the block contains only a `panic!` macro (as expression or statement)
708 fn is_panic_block(block: &Block<'_>) -> bool {
709 match (&block.expr, block.stmts.len(), block.stmts.first()) {
710 (&Some(ref exp), 0, _) => {
711 is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none()
713 (&None, 1, Some(stmt)) => {
714 is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none()
720 fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
721 if has_only_ref_pats(arms) {
722 let mut suggs = Vec::new();
723 let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind {
724 let span = ex.span.source_callsite();
725 suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string()));
727 "you don't need to add `&` to both the expression and the patterns",
731 let span = ex.span.source_callsite();
732 suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string()));
734 "you don't need to add `&` to all patterns",
735 "instead of prefixing all patterns with `&`, you can dereference the expression",
739 suggs.extend(arms.iter().filter_map(|a| {
740 if let PatKind::Ref(ref refp, _) = a.pat.kind {
741 Some((a.pat.span, snippet(cx, refp.span, "..").to_string()))
747 span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |db| {
748 if !expr.span.from_expansion() {
749 multispan_sugg(db, msg.to_owned(), suggs);
755 fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
756 if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() {
757 let arm_ref: Option<BindingAnnotation> = if is_none_arm(&arms[0]) {
758 is_ref_some_arm(&arms[1])
759 } else if is_none_arm(&arms[1]) {
760 is_ref_some_arm(&arms[0])
764 if let Some(rb) = arm_ref {
765 let suggestion = if rb == BindingAnnotation::Ref {
771 let output_ty = cx.tables.expr_ty(expr);
772 let input_ty = cx.tables.expr_ty(ex);
774 let cast = if_chain! {
775 if let ty::Adt(_, substs) = input_ty.kind;
776 let input_ty = substs.type_at(0);
777 if let ty::Adt(_, substs) = output_ty.kind;
778 let output_ty = substs.type_at(0);
779 if let ty::Ref(_, output_ty, _) = output_ty.kind;
780 if input_ty != output_ty;
788 let mut applicability = Applicability::MachineApplicable;
793 &format!("use `{}()` instead", suggestion),
797 snippet_with_applicability(cx, ex.span, "_", &mut applicability),
807 fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
809 if let PatKind::Or(ref fields) = arm.pat.kind {
810 // look for multiple fields in this arm that contains at least one Wild pattern
811 if fields.len() > 1 && fields.iter().any(is_wild) {
814 WILDCARD_IN_OR_PATTERNS,
816 "wildcard pattern covers any other pattern as it will match anyway.",
817 "Consider handling `_` separately.",
824 fn check_match_single_binding(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
825 if in_macro(expr.span) {
829 if is_refutable(cx, arms[0].pat) {
832 match arms[0].pat.kind {
833 PatKind::Binding(..) | PatKind::Tuple(_, _) => {
834 let bind_names = arms[0].pat.span;
835 let matched_vars = ex.span;
836 let match_body = remove_blocks(&arms[0].body);
839 MATCH_SINGLE_BINDING,
841 "this match could be written as a `let` statement",
842 "consider using `let` statement",
845 snippet(cx, bind_names, ".."),
846 snippet(cx, matched_vars, ".."),
847 snippet_block(cx, match_body.span, "..")
849 Applicability::MachineApplicable,
857 /// Gets all arms that are unbounded `PatRange`s.
858 fn all_ranges<'a, 'tcx>(
859 cx: &LateContext<'a, 'tcx>,
860 arms: &'tcx [Arm<'_>],
862 ) -> Vec<SpannedRange<Constant>> {
866 ref pat, guard: None, ..
869 if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind {
870 let lhs = match lhs {
871 Some(lhs) => constant(cx, cx.tables, lhs)?.0,
872 None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?,
874 let rhs = match rhs {
875 Some(rhs) => constant(cx, cx.tables, rhs)?.0,
876 None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?,
878 let rhs = match range_end {
879 RangeEnd::Included => Bound::Included(rhs),
880 RangeEnd::Excluded => Bound::Excluded(rhs),
882 return Some(SpannedRange {
888 if let PatKind::Lit(ref value) = pat.kind {
889 let value = constant(cx, cx.tables, value)?.0;
890 return Some(SpannedRange {
892 node: (value.clone(), Bound::Included(value)),
901 #[derive(Debug, Eq, PartialEq)]
902 pub struct SpannedRange<T> {
904 pub node: (T, Bound<T>),
907 type TypedRanges = Vec<SpannedRange<u128>>;
909 /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway
910 /// and other types than
911 /// `Uint` and `Int` probably don't make sense.
912 fn type_ranges(ranges: &[SpannedRange<Constant>]) -> TypedRanges {
915 .filter_map(|range| match range.node {
916 (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange {
918 node: (start, Bound::Included(end)),
920 (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange {
922 node: (start, Bound::Excluded(end)),
924 (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange {
926 node: (start, Bound::Unbounded),
933 fn is_unit_expr(expr: &Expr<'_>) -> bool {
935 ExprKind::Tup(ref v) if v.is_empty() => true,
936 ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
941 // Checks if arm has the form `None => None`
942 fn is_none_arm(arm: &Arm<'_>) -> bool {
944 PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true,
949 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
950 fn is_ref_some_arm(arm: &Arm<'_>) -> Option<BindingAnnotation> {
952 if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind;
953 if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME);
954 if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
955 if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
956 if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind;
957 if let ExprKind::Path(ref some_path) = e.kind;
958 if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1;
959 if let ExprKind::Path(ref qpath) = args[0].kind;
960 if let &QPath::Resolved(_, ref path2) = qpath;
961 if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name;
969 fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool {
974 PatKind::Ref(..) => Some(true), // &-patterns
975 PatKind::Wild => Some(false), // an "anything" wildcard is also fine
976 _ => None, // any other pattern is not fine
979 .collect::<Option<Vec<bool>>>();
980 // look for Some(v) where there's at least one true element
981 mapped.map_or(false, |v| v.iter().any(|el| *el))
984 pub fn overlapping<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)>
988 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
990 Start(T, &'a SpannedRange<T>),
991 End(Bound<T>, &'a SpannedRange<T>),
994 impl<'a, T: Copy> Kind<'a, T> {
995 fn range(&self) -> &'a SpannedRange<T> {
997 Kind::Start(_, r) | Kind::End(_, r) => r,
1001 fn value(self) -> Bound<T> {
1003 Kind::Start(t, _) => Bound::Included(t),
1004 Kind::End(t, _) => t,
1009 impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> {
1010 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1011 Some(self.cmp(other))
1015 impl<'a, T: Copy + Ord> Ord for Kind<'a, T> {
1016 fn cmp(&self, other: &Self) -> Ordering {
1017 match (self.value(), other.value()) {
1018 (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b),
1019 // Range patterns cannot be unbounded (yet)
1020 (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(),
1021 (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) {
1022 Ordering::Equal => Ordering::Greater,
1025 (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) {
1026 Ordering::Equal => Ordering::Less,
1033 let mut values = Vec::with_capacity(2 * ranges.len());
1036 values.push(Kind::Start(r.node.0, r));
1037 values.push(Kind::End(r.node.1, r));
1042 for (a, b) in values.iter().zip(values.iter().skip(1)) {
1044 (&Kind::Start(_, ra), &Kind::End(_, rb)) => {
1045 if ra.node != rb.node {
1046 return Some((ra, rb));
1049 (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (),
1050 _ => return Some((a.range(), b.range())),