X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=clippy_lints%2Fsrc%2Fmatches.rs;h=2f2dc4cfc6b03eb972d95bbb573c8789897e038d;hb=b094bb1bd7f1cc702823c91ca509f338fedee24a;hp=27e31222d006603c68715676936d92b15dc5cbcb;hpb=cf4e35339b1d5a613588b45c53d0e88da5363c65;p=rust.git diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs index 27e31222d00..2f2dc4cfc6b 100644 --- a/clippy_lints/src/matches.rs +++ b/clippy_lints/src/matches.rs @@ -1,28 +1,36 @@ use crate::consts::{constant, miri_to_const, Constant}; -use crate::utils::paths; -use crate::utils::sugg::Sugg; -use crate::utils::usage::is_unused; -use crate::utils::{ - expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable, - is_type_diagnostic_item, is_wild, match_qpath, match_type, match_var, multispan_sugg, remove_blocks, snippet, - snippet_block, snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, - span_lint_and_then, walk_ptrs_ty, +use clippy_utils::diagnostics::{ + multispan_sugg, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, }; +use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability}; +use clippy_utils::sugg::Sugg; +use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, peel_mid_ty_refs}; +use clippy_utils::visitors::LocalUsedVisitor; +use clippy_utils::{ + get_parent_expr, in_macro, is_allowed, is_expn_of, is_refutable, is_wild, match_qpath, meets_msrv, path_to_local, + path_to_local_id, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, remove_blocks, strip_pat_refs, +}; +use clippy_utils::{paths, search_same, SpanlessEq, SpanlessHash}; use if_chain::if_chain; use rustc_ast::ast::LitKind; +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::Applicability; -use rustc_hir::def::CtorKind; +use rustc_hir::def::{CtorKind, DefKind, Res}; use rustc_hir::{ - Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat, PatKind, - QPath, RangeEnd, + self as hir, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, HirId, Local, MatchSource, + Mutability, Node, Pat, PatKind, PathSegment, QPath, RangeEnd, TyKind, }; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::lint::in_external_macro; -use rustc_middle::ty::{self, Ty}; +use rustc_middle::ty::{self, Ty, TyS, VariantDef}; +use rustc_semver::RustcVersion; use rustc_session::{declare_tool_lint, impl_lint_pass}; -use rustc_span::source_map::Span; +use rustc_span::source_map::{Span, Spanned}; +use rustc_span::sym; use std::cmp::Ordering; -use std::collections::Bound; +use std::collections::hash_map::Entry; +use std::iter; +use std::ops::Bound; declare_clippy_lint! { /// **What it does:** Checks for matches with a single arm where an `if let` @@ -36,10 +44,16 @@ /// ```rust /// # fn bar(stool: &str) {} /// # let x = Some("abc"); + /// // Bad /// match x { /// Some(ref foo) => bar(foo), /// _ => (), /// } + /// + /// // Good + /// if let Some(ref foo) = x { + /// bar(foo); + /// } /// ``` pub SINGLE_MATCH, style, @@ -97,11 +111,19 @@ /// /// **Example:** /// ```rust,ignore + /// // Bad /// match x { /// &A(ref y) => foo(y), /// &B => bar(), /// _ => frob(&x), /// } + /// + /// // Good + /// match *x { + /// A(ref y) => foo(y), + /// B => bar(), + /// _ => frob(x), + /// } /// ``` pub MATCH_REF_PATS, style, @@ -138,7 +160,7 @@ /// } /// ``` pub MATCH_BOOL, - style, + pedantic, "a `match` on a boolean expression instead of an `if..else` block" } @@ -168,7 +190,7 @@ /// **What it does:** Checks for arm which matches all errors with `Err(_)` /// and take drastic actions like `panic!`. /// - /// **Why is this bad?** It is generally a bad practice, just like + /// **Why is this bad?** It is generally a bad practice, similar to /// catching all exceptions in java with `catch(Exception)` /// /// **Known problems:** None. @@ -182,7 +204,7 @@ /// } /// ``` pub MATCH_WILD_ERR_ARM, - style, + pedantic, "a `match` with `Err(_)` arm and take drastic actions" } @@ -197,10 +219,15 @@ /// **Example:** /// ```rust /// let x: Option<()> = None; + /// + /// // Bad /// let r: Option<&()> = match x { /// None => None, /// Some(ref v) => Some(v), /// }; + /// + /// // Good + /// let r: Option<&()> = x.as_ref(); /// ``` pub MATCH_AS_REF, complexity, @@ -219,16 +246,55 @@ /// ```rust /// # enum Foo { A(usize), B(usize) } /// # let x = Foo::B(1); + /// // Bad /// match x { - /// A => {}, + /// Foo::A(_) => {}, /// _ => {}, /// } + /// + /// // Good + /// match x { + /// Foo::A(_) => {}, + /// Foo::B(_) => {}, + /// } /// ``` pub WILDCARD_ENUM_MATCH_ARM, restriction, "a wildcard enum match arm using `_`" } +declare_clippy_lint! { + /// **What it does:** Checks for wildcard enum matches for a single variant. + /// + /// **Why is this bad?** New enum variants added by library updates can be missed. + /// + /// **Known problems:** Suggested replacements may not use correct path to enum + /// if it's not present in the current scope. + /// + /// **Example:** + /// + /// ```rust + /// # enum Foo { A, B, C } + /// # let x = Foo::B; + /// // Bad + /// match x { + /// Foo::A => {}, + /// Foo::B => {}, + /// _ => {}, + /// } + /// + /// // Good + /// match x { + /// Foo::A => {}, + /// Foo::B => {}, + /// Foo::C => {}, + /// } + /// ``` + pub MATCH_WILDCARD_FOR_SINGLE_VARIANTS, + pedantic, + "a wildcard enum match for a single variant" +} + declare_clippy_lint! { /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm. /// @@ -239,10 +305,17 @@ /// /// **Example:** /// ```rust + /// // Bad /// match "foo" { /// "a" => {}, /// "bar" | _ => {}, /// } + /// + /// // Good + /// match "foo" { + /// "a" => {}, + /// _ => {}, + /// } /// ``` pub WILDCARD_IN_OR_PATTERNS, complexity, @@ -342,11 +415,144 @@ "a match on a struct that binds all fields but still uses the wildcard pattern" } +declare_clippy_lint! { + /// **What it does:** Lint for redundant pattern matching over `Result`, `Option`, + /// `std::task::Poll` or `std::net::IpAddr` + /// + /// **Why is this bad?** It's more concise and clear to just use the proper + /// utility function + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// # use std::task::Poll; + /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr}; + /// if let Ok(_) = Ok::(42) {} + /// if let Err(_) = Err::(42) {} + /// if let None = None::<()> {} + /// if let Some(_) = Some(42) {} + /// if let Poll::Pending = Poll::Pending::<()> {} + /// if let Poll::Ready(_) = Poll::Ready(42) {} + /// if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {} + /// if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {} + /// match Ok::(42) { + /// Ok(_) => true, + /// Err(_) => false, + /// }; + /// ``` + /// + /// The more idiomatic use would be: + /// + /// ```rust + /// # use std::task::Poll; + /// # use std::net::{IpAddr, Ipv4Addr, Ipv6Addr}; + /// if Ok::(42).is_ok() {} + /// if Err::(42).is_err() {} + /// if None::<()>.is_none() {} + /// if Some(42).is_some() {} + /// if Poll::Pending::<()>.is_pending() {} + /// if Poll::Ready(42).is_ready() {} + /// if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {} + /// if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {} + /// Ok::(42).is_ok(); + /// ``` + pub REDUNDANT_PATTERN_MATCHING, + style, + "use the proper utility function avoiding an `if let`" +} + +declare_clippy_lint! { + /// **What it does:** Checks for `match` or `if let` expressions producing a + /// `bool` that could be written using `matches!` + /// + /// **Why is this bad?** Readability and needless complexity. + /// + /// **Known problems:** This lint falsely triggers, if there are arms with + /// `cfg` attributes that remove an arm evaluating to `false`. + /// + /// **Example:** + /// ```rust + /// let x = Some(5); + /// + /// // Bad + /// let a = match x { + /// Some(0) => true, + /// _ => false, + /// }; + /// + /// let a = if let Some(0) = x { + /// true + /// } else { + /// false + /// }; + /// + /// // Good + /// let a = matches!(x, Some(0)); + /// ``` + pub MATCH_LIKE_MATCHES_MACRO, + style, + "a match that could be written with the matches! macro" +} + +declare_clippy_lint! { + /// **What it does:** Checks for `match` with identical arm bodies. + /// + /// **Why is this bad?** This is probably a copy & paste error. If arm bodies + /// are the same on purpose, you can factor them + /// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns). + /// + /// **Known problems:** False positive possible with order dependent `match` + /// (see issue + /// [#860](https://github.com/rust-lang/rust-clippy/issues/860)). + /// + /// **Example:** + /// ```rust,ignore + /// match foo { + /// Bar => bar(), + /// Quz => quz(), + /// Baz => bar(), // <= oops + /// } + /// ``` + /// + /// This should probably be + /// ```rust,ignore + /// match foo { + /// Bar => bar(), + /// Quz => quz(), + /// Baz => baz(), // <= fixed + /// } + /// ``` + /// + /// or if the original code was not a typo: + /// ```rust,ignore + /// match foo { + /// Bar | Baz => bar(), // <= shows the intent better + /// Quz => quz(), + /// } + /// ``` + pub MATCH_SAME_ARMS, + pedantic, + "`match` with identical arm bodies" +} + #[derive(Default)] pub struct Matches { + msrv: Option, infallible_destructuring_match_linted: bool, } +impl Matches { + #[must_use] + pub fn new(msrv: Option) -> Self { + Self { + msrv, + ..Matches::default() + } + } +} + impl_lint_pass!(Matches => [ SINGLE_MATCH, MATCH_REF_PATS, @@ -356,17 +562,34 @@ pub struct Matches { MATCH_WILD_ERR_ARM, MATCH_AS_REF, WILDCARD_ENUM_MATCH_ARM, + MATCH_WILDCARD_FOR_SINGLE_VARIANTS, WILDCARD_IN_OR_PATTERNS, MATCH_SINGLE_BINDING, INFALLIBLE_DESTRUCTURING_MATCH, - REST_PAT_IN_FULLY_BOUND_STRUCTS + REST_PAT_IN_FULLY_BOUND_STRUCTS, + REDUNDANT_PATTERN_MATCHING, + MATCH_LIKE_MATCHES_MACRO, + MATCH_SAME_ARMS, ]); -impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Matches { - fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) { - if in_external_macro(cx.sess(), expr.span) { +const MATCH_LIKE_MATCHES_MACRO_MSRV: RustcVersion = RustcVersion::new(1, 42, 0); + +impl<'tcx> LateLintPass<'tcx> for Matches { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if in_external_macro(cx.sess(), expr.span) || in_macro(expr.span) { return; } + + redundant_pattern_match::check(cx, expr); + + if meets_msrv(self.msrv.as_ref(), &MATCH_LIKE_MATCHES_MACRO_MSRV) { + if !check_match_like_matches(cx, expr) { + lint_match_arms(cx, expr); + } + } else { + lint_match_arms(cx, expr); + } + if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind { check_single_match(cx, ex, arms, expr); check_match_bool(cx, ex, arms, expr); @@ -387,7 +610,7 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) { } } - fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) { + fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) { if_chain! { if !in_external_macro(cx.sess(), local.span); if !in_macro(local.span); @@ -397,9 +620,9 @@ fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) { if let PatKind::TupleStruct( QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind; if args.len() == 1; - if let Some(arg) = get_arg_name(&args[0]); + if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind; let body = remove_blocks(&arms[0].body); - if match_var(body, arg); + if path_to_local_id(body, arg); then { let mut applicability = Applicability::MachineApplicable; @@ -423,15 +646,14 @@ fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) { } } - fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) { + fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) { if_chain! { if !in_external_macro(cx.sess(), pat.span); if !in_macro(pat.span); - if let PatKind::Struct(ref qpath, fields, true) = pat.kind; - if let QPath::Resolved(_, ref path) = qpath; + if let PatKind::Struct(QPath::Resolved(_, ref path), fields, true) = pat.kind; if let Some(def_id) = path.res.opt_def_id(); let ty = cx.tcx.type_of(def_id); - if let ty::Adt(def, _) = ty.kind; + if let ty::Adt(def, _) = ty.kind(); if def.is_struct() || def.is_union(); if fields.len() == def.non_enum_variant().fields.len(); @@ -447,10 +669,12 @@ fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>) { } } } + + extract_msrv_attr!(LateContext); } #[rustfmt::skip] -fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { +fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() { if in_macro(expr.span) { // Don't lint match expressions present in @@ -462,18 +686,23 @@ fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], // the lint noisy in unnecessary situations return; } - let els = remove_blocks(&arms[1].body); - let els = if is_unit_expr(els) { + let els = arms[1].body; + let els = if is_unit_expr(remove_blocks(els)) { None - } else if let ExprKind::Block(_, _) = els.kind { - // matches with blocks that contain statements are prettier as `if let + else` + } else if let ExprKind::Block(Block { stmts, expr: block_expr, .. }, _) = els.kind { + if stmts.len() == 1 && block_expr.is_none() || stmts.is_empty() && block_expr.is_some() { + // single statement/expr "else" block, don't lint + return; + } + // block with 2+ statements or 1 expr and 1+ statement Some(els) } else { - // allow match arms with just expressions + // not a block, don't lint return; }; - let ty = cx.tables.expr_ty(ex); - if ty.kind != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) { + + let ty = cx.typeck_results().expr_ty(ex); + if *ty.kind() != ty::Bool || is_allowed(cx, MATCH_BOOL, ex.hir_id) { check_single_match_single_pattern(cx, ex, arms, expr, els); check_single_match_opt_like(cx, ex, arms, expr, ty, els); } @@ -481,7 +710,7 @@ fn check_single_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], } fn check_single_match_single_pattern( - cx: &LateContext<'_, '_>, + cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, @@ -493,7 +722,7 @@ fn check_single_match_single_pattern( } fn report_single_match_single_pattern( - cx: &LateContext<'_, '_>, + cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, @@ -503,26 +732,66 @@ fn report_single_match_single_pattern( let els_str = els.map_or(String::new(), |els| { format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span))) }); + + let (msg, sugg) = if_chain! { + let (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat); + if let PatKind::Path(_) | PatKind::Lit(_) = pat.kind; + let (ty, ty_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(ex)); + if let Some(trait_id) = cx.tcx.lang_items().structural_peq_trait(); + if ty.is_integral() || ty.is_char() || ty.is_str() || implements_trait(cx, ty, trait_id, &[]); + then { + // scrutinee derives PartialEq and the pattern is a constant. + let pat_ref_count = match pat.kind { + // string literals are already a reference. + PatKind::Lit(Expr { kind: ExprKind::Lit(lit), .. }) if lit.node.is_str() => pat_ref_count + 1, + _ => pat_ref_count, + }; + // References are only implicitly added to the pattern, so no overflow here. + // e.g. will work: match &Some(_) { Some(_) => () } + // will not: match Some(_) { &Some(_) => () } + let ref_count_diff = ty_ref_count - pat_ref_count; + + // Try to remove address of expressions first. + let (ex, removed) = peel_n_hir_expr_refs(ex, ref_count_diff); + let ref_count_diff = ref_count_diff - removed; + + let msg = "you seem to be trying to use `match` for an equality check. Consider using `if`"; + let sugg = format!( + "if {} == {}{} {}{}", + snippet(cx, ex.span, ".."), + // PartialEq for different reference counts may not exist. + "&".repeat(ref_count_diff), + snippet(cx, arms[0].pat.span, ".."), + expr_block(cx, &arms[0].body, None, "..", Some(expr.span)), + els_str, + ); + (msg, sugg) + } else { + let msg = "you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`"; + let sugg = format!( + "if let {} = {} {}{}", + snippet(cx, arms[0].pat.span, ".."), + snippet(cx, ex.span, ".."), + expr_block(cx, &arms[0].body, None, "..", Some(expr.span)), + els_str, + ); + (msg, sugg) + } + }; + span_lint_and_sugg( cx, lint, expr.span, - "you seem to be trying to use match for destructuring a single pattern. Consider using `if \ - let`", + msg, "try this", - format!( - "if let {} = {} {}{}", - snippet(cx, arms[0].pat.span, ".."), - snippet(cx, ex.span, ".."), - expr_block(cx, &arms[0].body, None, "..", Some(expr.span)), - els_str, - ), + sugg, Applicability::HasPlaceholders, ); } fn check_single_match_opt_like( - cx: &LateContext<'_, '_>, + cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, @@ -562,9 +831,9 @@ fn check_single_match_opt_like( } } -fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { +fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { // Type of expression is `bool`. - if cx.tables.expr_ty(ex).kind == ty::Bool { + if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool { span_lint_and_then( cx, MATCH_BOOL, @@ -626,9 +895,9 @@ fn check_match_bool(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], e } } -fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) { - if arms.len() >= 2 && cx.tables.expr_ty(ex).is_integral() { - let ranges = all_ranges(cx, arms, cx.tables.expr_ty(ex)); +fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) { + if arms.len() >= 2 && cx.typeck_results().expr_ty(ex).is_integral() { + let ranges = all_ranges(cx, arms, cx.typeck_results().expr_ty(ex)); let type_ranges = type_ranges(&ranges); if !type_ranges.is_empty() { if let Some((start, end)) = overlapping(&type_ranges) { @@ -637,7 +906,7 @@ fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<' MATCH_OVERLAPPING_ARM, start.span, "some ranges overlap", - end.span, + Some(end.span), "overlaps with this", ); } @@ -645,9 +914,9 @@ fn check_overlapping_arms<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ex: &'tcx Expr<' } } -fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) { - let ex_ty = walk_ptrs_ty(cx.tables.expr_ty(ex)); - if is_type_diagnostic_item(cx, ex_ty, sym!(result_type)) { +fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) { + let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs(); + if is_type_diagnostic_item(cx, ex_ty, sym::result_type) { for arm in arms { if let PatKind::TupleStruct(ref path, ref inner, _) = arm.pat.kind { let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)); @@ -657,8 +926,10 @@ fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) if !matching_wild { // Looking for unused bindings (i.e.: `_e`) inner.iter().for_each(|pat| { - if let PatKind::Binding(.., ident, None) = &pat.kind { - if ident.as_str().starts_with('_') && is_unused(ident, arm.body) { + if let PatKind::Binding(_, id, ident, None) = pat.kind { + if ident.as_str().starts_with('_') + && !LocalUsedVisitor::new(cx, id).check_expr(arm.body) + { ident_bind_name = (&ident.name.as_str()).to_string(); matching_wild = true; } @@ -675,8 +946,8 @@ fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) MATCH_WILD_ERR_ARM, arm.pat.span, &format!("`Err({})` matches all errors", &ident_bind_name), - arm.pat.span, - "match each error separately or use the error output", + None, + "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable", ); } } @@ -686,96 +957,181 @@ fn check_wild_err_arm(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) } } -fn check_wild_enum_match(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>]) { - let ty = cx.tables.expr_ty(ex); - if !ty.is_enum() { - // If there isn't a nice closed set of possible values that can be conveniently enumerated, - // don't complain about not enumerating the mall. - return; +enum CommonPrefixSearcher<'a> { + None, + Path(&'a [PathSegment<'a>]), + Mixed, +} +impl CommonPrefixSearcher<'a> { + fn with_path(&mut self, path: &'a [PathSegment<'a>]) { + match path { + [path @ .., _] => self.with_prefix(path), + [] => (), + } + } + + fn with_prefix(&mut self, path: &'a [PathSegment<'a>]) { + match self { + Self::None => *self = Self::Path(path), + Self::Path(self_path) + if path + .iter() + .map(|p| p.ident.name) + .eq(self_path.iter().map(|p| p.ident.name)) => {}, + Self::Path(_) => *self = Self::Mixed, + Self::Mixed => (), + } } +} + +#[allow(clippy::too_many_lines)] +fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) { + let ty = cx.typeck_results().expr_ty(ex).peel_refs(); + let adt_def = match ty.kind() { + ty::Adt(adt_def, _) + if adt_def.is_enum() + && !(is_type_diagnostic_item(cx, ty, sym::option_type) + || is_type_diagnostic_item(cx, ty, sym::result_type)) => + { + adt_def + }, + _ => return, + }; // First pass - check for violation, but don't do much book-keeping because this is hopefully // the uncommon case, and the book-keeping is slightly expensive. let mut wildcard_span = None; let mut wildcard_ident = None; + let mut has_non_wild = false; for arm in arms { - if let PatKind::Wild = arm.pat.kind { - wildcard_span = Some(arm.pat.span); - } else if let PatKind::Binding(_, _, ident, None) = arm.pat.kind { - wildcard_span = Some(arm.pat.span); - wildcard_ident = Some(ident); + match peel_hir_pat_refs(arm.pat).0.kind { + PatKind::Wild => wildcard_span = Some(arm.pat.span), + PatKind::Binding(_, _, ident, None) => { + wildcard_span = Some(arm.pat.span); + wildcard_ident = Some(ident); + }, + _ => has_non_wild = true, } } + let wildcard_span = match wildcard_span { + Some(x) if has_non_wild => x, + _ => return, + }; - if let Some(wildcard_span) = wildcard_span { - // Accumulate the variants which should be put in place of the wildcard because they're not - // already covered. + // Accumulate the variants which should be put in place of the wildcard because they're not + // already covered. + let mut missing_variants: Vec<_> = adt_def.variants.iter().collect(); - let mut missing_variants = vec![]; - if let ty::Adt(def, _) = ty.kind { - for variant in &def.variants { - missing_variants.push(variant); + let mut path_prefix = CommonPrefixSearcher::None; + for arm in arms { + // Guards mean that this case probably isn't exhaustively covered. Technically + // this is incorrect, as we should really check whether each variant is exhaustively + // covered by the set of guards that cover it, but that's really hard to do. + recurse_or_patterns(arm.pat, |pat| { + let path = match &peel_hir_pat_refs(pat).0.kind { + PatKind::Path(path) => { + #[allow(clippy::match_same_arms)] + let id = match cx.qpath_res(path, pat.hir_id) { + Res::Def(DefKind::Const | DefKind::ConstParam | DefKind::AnonConst, _) => return, + Res::Def(_, id) => id, + _ => return, + }; + if arm.guard.is_none() { + missing_variants.retain(|e| e.ctor_def_id != Some(id)); + } + path + }, + PatKind::TupleStruct(path, patterns, ..) => { + if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) { + let id = cx.qpath_res(path, pat.hir_id).def_id(); + missing_variants.retain(|e| e.ctor_def_id != Some(id)); + } + path + }, + PatKind::Struct(path, patterns, ..) => { + if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) { + let id = cx.qpath_res(path, pat.hir_id).def_id(); + missing_variants.retain(|e| e.def_id != id); + } + path + }, + _ => return, + }; + match path { + QPath::Resolved(_, path) => path_prefix.with_path(path.segments), + QPath::TypeRelative( + hir::Ty { + kind: TyKind::Path(QPath::Resolved(_, path)), + .. + }, + _, + ) => path_prefix.with_prefix(path.segments), + _ => (), } - } + }); + } - for arm in arms { - if arm.guard.is_some() { - // Guards mean that this case probably isn't exhaustively covered. Technically - // this is incorrect, as we should really check whether each variant is exhaustively - // covered by the set of guards that cover it, but that's really hard to do. - continue; - } - if let PatKind::Path(ref path) = arm.pat.kind { - if let QPath::Resolved(_, p) = path { - missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id())); - } - } else if let PatKind::TupleStruct(ref path, ..) = arm.pat.kind { - if let QPath::Resolved(_, p) = path { - missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id())); + let format_suggestion = |variant: &VariantDef| { + format!( + "{}{}{}{}", + if let Some(ident) = wildcard_ident { + format!("{} @ ", ident.name) + } else { + String::new() + }, + if let CommonPrefixSearcher::Path(path_prefix) = path_prefix { + let mut s = String::new(); + for seg in path_prefix { + s.push_str(&seg.ident.as_str()); + s.push_str("::"); } + s + } else { + let mut s = cx.tcx.def_path_str(adt_def.did); + s.push_str("::"); + s + }, + variant.ident.name, + match variant.ctor_kind { + CtorKind::Fn if variant.fields.len() == 1 => "(_)", + CtorKind::Fn => "(..)", + CtorKind::Const => "", + CtorKind::Fictive => "{ .. }", } - } - - let mut suggestion: Vec = missing_variants - .iter() - .map(|v| { - let suffix = match v.ctor_kind { - CtorKind::Fn => "(..)", - CtorKind::Const | CtorKind::Fictive => "", - }; - let ident_str = if let Some(ident) = wildcard_ident { - format!("{} @ ", ident.name) - } else { - String::new() - }; - // This path assumes that the enum type is imported into scope. - format!("{}{}{}", ident_str, cx.tcx.def_path_str(v.def_id), suffix) - }) - .collect(); - - if suggestion.is_empty() { - return; - } - - let mut message = "wildcard match will miss any future added variants"; - - if let ty::Adt(def, _) = ty.kind { - if def.is_variant_list_non_exhaustive() { - message = "match on non-exhaustive enum doesn't explicitly match all known variants"; - suggestion.push(String::from("_")); - } - } + ) + }; - span_lint_and_sugg( + match missing_variants.as_slice() { + [] => (), + [x] if !adt_def.is_variant_list_non_exhaustive() => span_lint_and_sugg( cx, - WILDCARD_ENUM_MATCH_ARM, + MATCH_WILDCARD_FOR_SINGLE_VARIANTS, wildcard_span, - message, + "wildcard matches only a single variant and will also match any future added variants", "try this", - suggestion.join(" | "), - Applicability::MachineApplicable, - ) - } + format_suggestion(x), + Applicability::MaybeIncorrect, + ), + variants => { + let mut suggestions: Vec<_> = variants.iter().cloned().map(format_suggestion).collect(); + let message = if adt_def.is_variant_list_non_exhaustive() { + suggestions.push("_".into()); + "wildcard matches known variants and will also match future added variants" + } else { + "wildcard match will also match any future added variants" + }; + + span_lint_and_sugg( + cx, + WILDCARD_ENUM_MATCH_ARM, + wildcard_span, + message, + "try this", + suggestions.join(" | "), + Applicability::MaybeIncorrect, + ) + }, + }; } // If the block contains only a `panic!` macro (as expression or statement) @@ -791,7 +1147,7 @@ fn is_panic_block(block: &Block<'_>) -> bool { } } -fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { +fn check_match_ref_pats(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { if has_only_ref_pats(arms) { let mut suggs = Vec::with_capacity(arms.len() + 1); let (title, msg) = if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind { @@ -820,13 +1176,13 @@ fn check_match_ref_pats(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_> span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| { if !expr.span.from_expansion() { - multispan_sugg(diag, msg.to_owned(), suggs); + multispan_sugg(diag, msg, suggs); } }); } } -fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { +fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { if arms.len() == 2 && arms[0].guard.is_none() && arms[1].guard.is_none() { let arm_ref: Option = if is_none_arm(&arms[0]) { is_ref_some_arm(&arms[1]) @@ -842,15 +1198,15 @@ fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], "as_mut" }; - let output_ty = cx.tables.expr_ty(expr); - let input_ty = cx.tables.expr_ty(ex); + let output_ty = cx.typeck_results().expr_ty(expr); + let input_ty = cx.typeck_results().expr_ty(ex); let cast = if_chain! { - if let ty::Adt(_, substs) = input_ty.kind; + if let ty::Adt(_, substs) = input_ty.kind(); let input_ty = substs.type_at(0); - if let ty::Adt(_, substs) = output_ty.kind; + if let ty::Adt(_, substs) = output_ty.kind(); let output_ty = substs.type_at(0); - if let ty::Ref(_, output_ty, _) = output_ty.kind; + if let ty::Ref(_, output_ty, _) = *output_ty.kind(); if input_ty != output_ty; then { ".map(|x| x as _)" @@ -878,7 +1234,7 @@ fn check_match_as_ref(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], } } -fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) { +fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) { for arm in arms { if let PatKind::Or(ref fields) = arm.pat.kind { // look for multiple fields in this arm that contains at least one Wild pattern @@ -887,19 +1243,140 @@ fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) { cx, WILDCARD_IN_OR_PATTERNS, arm.pat.span, - "wildcard pattern covers any other pattern as it will match anyway.", + "wildcard pattern covers any other pattern as it will match anyway", None, - "Consider handling `_` separately.", + "consider handling `_` separately", ); } } } } -fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) { +/// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!` +fn check_match_like_matches<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool { + if let ExprKind::Match(ex, arms, ref match_source) = &expr.kind { + match match_source { + MatchSource::Normal => find_matches_sugg(cx, ex, arms, expr, false), + MatchSource::IfLetDesugar { .. } => find_matches_sugg(cx, ex, arms, expr, true), + _ => false, + } + } else { + false + } +} + +/// Lint a `match` or desugared `if let` for replacement by `matches!` +fn find_matches_sugg(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, desugared: bool) -> bool { + if_chain! { + if arms.len() >= 2; + if cx.typeck_results().expr_ty(expr).is_bool(); + if let Some((b1_arm, b0_arms)) = arms.split_last(); + if let Some(b0) = find_bool_lit(&b0_arms[0].body.kind, desugared); + if let Some(b1) = find_bool_lit(&b1_arm.body.kind, desugared); + if is_wild(&b1_arm.pat); + if b0 != b1; + let if_guard = &b0_arms[0].guard; + if if_guard.is_none() || b0_arms.len() == 1; + if cx.tcx.hir().attrs(b0_arms[0].hir_id).is_empty(); + if b0_arms[1..].iter() + .all(|arm| { + find_bool_lit(&arm.body.kind, desugared).map_or(false, |b| b == b0) && + arm.guard.is_none() && cx.tcx.hir().attrs(arm.hir_id).is_empty() + }); + then { + // The suggestion may be incorrect, because some arms can have `cfg` attributes + // evaluated into `false` and so such arms will be stripped before. + let mut applicability = Applicability::MaybeIncorrect; + let pat = { + use itertools::Itertools as _; + b0_arms.iter() + .map(|arm| snippet_with_applicability(cx, arm.pat.span, "..", &mut applicability)) + .join(" | ") + }; + let pat_and_guard = if let Some(Guard::If(g)) = if_guard { + format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability)) + } else { + pat + }; + + // strip potential borrows (#6503), but only if the type is a reference + let mut ex_new = ex; + if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind { + if let ty::Ref(..) = cx.typeck_results().expr_ty(&ex_inner).kind() { + ex_new = ex_inner; + } + }; + span_lint_and_sugg( + cx, + MATCH_LIKE_MATCHES_MACRO, + expr.span, + &format!("{} expression looks like `matches!` macro", if desugared { "if let .. else" } else { "match" }), + "try this", + format!( + "{}matches!({}, {})", + if b0 { "" } else { "!" }, + snippet_with_applicability(cx, ex_new.span, "..", &mut applicability), + pat_and_guard, + ), + applicability, + ); + true + } else { + false + } + } +} + +/// Extract a `bool` or `{ bool }` +fn find_bool_lit(ex: &ExprKind<'_>, desugared: bool) -> Option { + match ex { + ExprKind::Lit(Spanned { + node: LitKind::Bool(b), .. + }) => Some(*b), + ExprKind::Block( + rustc_hir::Block { + stmts: &[], + expr: Some(exp), + .. + }, + _, + ) if desugared => { + if let ExprKind::Lit(Spanned { + node: LitKind::Bool(b), .. + }) = exp.kind + { + Some(b) + } else { + None + } + }, + _ => None, + } +} + +#[allow(clippy::too_many_lines)] +fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) { if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) { return; } + + // HACK: + // This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here + // to prevent false positives as there is currently no better way to detect if code was excluded by + // a macro. See PR #6435 + if_chain! { + if let Some(match_snippet) = snippet_opt(cx, expr.span); + if let Some(arm_snippet) = snippet_opt(cx, arms[0].span); + if let Some(ex_snippet) = snippet_opt(cx, ex.span); + let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, ""); + if rest_snippet.contains("=>"); + then { + // The code it self contains another thick arrow "=>" + // -> Either another arm or a comment + return; + } + } + let matched_vars = ex.span; let bind_names = arms[0].pat.span; let match_body = remove_blocks(&arms[0].body); @@ -913,13 +1390,13 @@ fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: match match_body.kind { ExprKind::Block(block, _) => { // macro + expr_ty(body) == () - if block.span.from_expansion() && cx.tables.expr_ty(&match_body).is_unit() { + if block.span.from_expansion() && cx.typeck_results().expr_ty(&match_body).is_unit() { snippet_body.push(';'); } }, _ => { // expr_ty(body) == () - if cx.tables.expr_ty(&match_body).is_unit() { + if cx.typeck_results().expr_ty(&match_body).is_unit() { snippet_body.push(';'); } }, @@ -952,7 +1429,18 @@ fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0)); cbrace_start = format!("{{\n{}", indent); } - }; + } + // If the parent is already an arm, and the body is another match statement, + // we need curly braces around suggestion + let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id); + if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) { + if let ExprKind::Match(..) = arm.body.kind { + cbrace_end = format!("\n{}}}", indent); + // Fix body indent due to the match + indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0)); + cbrace_start = format!("{{\n{}", indent); + } + } ( expr.span, format!( @@ -992,7 +1480,7 @@ fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: } /// Returns true if the `ex` match expression is in a local (`let`) statement -fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> { +fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> { if_chain! { let map = &cx.tcx.hir(); if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id)); @@ -1005,11 +1493,7 @@ fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Loc } /// Gets all arms that are unbounded `PatRange`s. -fn all_ranges<'a, 'tcx>( - cx: &LateContext<'a, 'tcx>, - arms: &'tcx [Arm<'_>], - ty: Ty<'tcx>, -) -> Vec> { +fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec> { arms.iter() .flat_map(|arm| { if let Arm { @@ -1018,11 +1502,11 @@ fn all_ranges<'a, 'tcx>( { if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind { let lhs = match lhs { - Some(lhs) => constant(cx, cx.tables, lhs)?.0, + Some(lhs) => constant(cx, cx.typeck_results(), lhs)?.0, None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?, }; let rhs = match rhs { - Some(rhs) => constant(cx, cx.tables, rhs)?.0, + Some(rhs) => constant(cx, cx.typeck_results(), rhs)?.0, None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?, }; let rhs = match range_end { @@ -1036,7 +1520,7 @@ fn all_ranges<'a, 'tcx>( } if let PatKind::Lit(ref value) = pat.kind { - let value = constant(cx, cx.tables, value)?.0; + let value = constant(cx, cx.typeck_results(), value)?.0; return Some(SpannedRange { span: pat.span, node: (value.clone(), Bound::Included(value)), @@ -1090,10 +1574,7 @@ fn is_unit_expr(expr: &Expr<'_>) -> bool { // Checks if arm has the form `None => None` fn is_none_arm(arm: &Arm<'_>) -> bool { - match arm.pat.kind { - PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true, - _ => false, - } + matches!(arm.pat.kind, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE)) } // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`) @@ -1106,8 +1587,7 @@ fn is_ref_some_arm(arm: &Arm<'_>) -> Option { if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind; if let ExprKind::Path(ref some_path) = e.kind; if match_qpath(some_path, &paths::OPTION_SOME) && args.len() == 1; - if let ExprKind::Path(ref qpath) = args[0].kind; - if let &QPath::Resolved(_, ref path2) = qpath; + if let ExprKind::Path(QPath::Resolved(_, ref path2)) = args[0].kind; if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name; then { return Some(rb) @@ -1189,7 +1669,7 @@ fn cmp(&self, other: &Self) -> Ordering { values.sort(); - for (a, b) in values.iter().zip(values.iter().skip(1)) { + for (a, b) in iter::zip(&values, &values[1..]) { match (a, b) { (&Kind::Start(_, ra), &Kind::End(_, rb)) => { if ra.node != rb.node { @@ -1197,13 +1677,247 @@ fn cmp(&self, other: &Self) -> Ordering { } }, (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (), - _ => return Some((a.range(), b.range())), + _ => { + // skip if the range `a` is completely included into the range `b` + if let Ordering::Equal | Ordering::Less = a.cmp(&b) { + let kind_a = Kind::End(a.range().node.1, a.range()); + let kind_b = Kind::End(b.range().node.1, b.range()); + if let Ordering::Equal | Ordering::Greater = kind_a.cmp(&kind_b) { + return None; + } + } + return Some((a.range(), b.range())); + }, } } None } +mod redundant_pattern_match { + use super::REDUNDANT_PATTERN_MATCHING; + use clippy_utils::diagnostics::span_lint_and_then; + use clippy_utils::source::snippet; + use clippy_utils::{is_trait_method, match_qpath, paths}; + use if_chain::if_chain; + use rustc_ast::ast::LitKind; + use rustc_errors::Applicability; + use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath}; + use rustc_lint::LateContext; + use rustc_span::sym; + + pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if let ExprKind::Match(op, arms, ref match_source) = &expr.kind { + match match_source { + MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms), + MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms, "if"), + MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, arms, "while"), + _ => {}, + } + } + } + + fn find_sugg_for_if_let<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + op: &Expr<'_>, + arms: &[Arm<'_>], + keyword: &'static str, + ) { + let good_method = match arms[0].pat.kind { + PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => { + if let PatKind::Wild = patterns[0].kind { + if match_qpath(path, &paths::RESULT_OK) { + "is_ok()" + } else if match_qpath(path, &paths::RESULT_ERR) { + "is_err()" + } else if match_qpath(path, &paths::OPTION_SOME) { + "is_some()" + } else if match_qpath(path, &paths::POLL_READY) { + "is_ready()" + } else if match_qpath(path, &paths::IPADDR_V4) { + "is_ipv4()" + } else if match_qpath(path, &paths::IPADDR_V6) { + "is_ipv6()" + } else { + return; + } + } else { + return; + } + }, + PatKind::Path(ref path) => { + if match_qpath(path, &paths::OPTION_NONE) { + "is_none()" + } else if match_qpath(path, &paths::POLL_PENDING) { + "is_pending()" + } else { + return; + } + }, + _ => return, + }; + + // check that `while_let_on_iterator` lint does not trigger + if_chain! { + if keyword == "while"; + if let ExprKind::MethodCall(method_path, _, _, _) = op.kind; + if method_path.ident.name == sym::next; + if is_trait_method(cx, op, sym::Iterator); + then { + return; + } + } + + let result_expr = match &op.kind { + ExprKind::AddrOf(_, _, borrowed) => borrowed, + _ => op, + }; + span_lint_and_then( + cx, + REDUNDANT_PATTERN_MATCHING, + arms[0].pat.span, + &format!("redundant pattern matching, consider using `{}`", good_method), + |diag| { + // while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + let expr_span = expr.span; + + // while let ... = ... { ... } + // ^^^ + let op_span = result_expr.span.source_callsite(); + + // while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^ + let span = expr_span.until(op_span.shrink_to_hi()); + diag.span_suggestion( + span, + "try this", + format!("{} {}.{}", keyword, snippet(cx, op_span, "_"), good_method), + Applicability::MachineApplicable, // snippet + ); + }, + ); + } + + fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) { + if arms.len() == 2 { + let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind); + + let found_good_method = match node_pair { + ( + PatKind::TupleStruct(ref path_left, ref patterns_left, _), + PatKind::TupleStruct(ref path_right, ref patterns_right, _), + ) if patterns_left.len() == 1 && patterns_right.len() == 1 => { + if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) { + find_good_method_for_match( + arms, + path_left, + path_right, + &paths::RESULT_OK, + &paths::RESULT_ERR, + "is_ok()", + "is_err()", + ) + .or_else(|| { + find_good_method_for_match( + arms, + path_left, + path_right, + &paths::IPADDR_V4, + &paths::IPADDR_V6, + "is_ipv4()", + "is_ipv6()", + ) + }) + } else { + None + } + }, + (PatKind::TupleStruct(ref path_left, ref patterns, _), PatKind::Path(ref path_right)) + | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, ref patterns, _)) + if patterns.len() == 1 => + { + if let PatKind::Wild = patterns[0].kind { + find_good_method_for_match( + arms, + path_left, + path_right, + &paths::OPTION_SOME, + &paths::OPTION_NONE, + "is_some()", + "is_none()", + ) + .or_else(|| { + find_good_method_for_match( + arms, + path_left, + path_right, + &paths::POLL_READY, + &paths::POLL_PENDING, + "is_ready()", + "is_pending()", + ) + }) + } else { + None + } + }, + _ => None, + }; + + if let Some(good_method) = found_good_method { + let span = expr.span.to(op.span); + let result_expr = match &op.kind { + ExprKind::AddrOf(_, _, borrowed) => borrowed, + _ => op, + }; + span_lint_and_then( + cx, + REDUNDANT_PATTERN_MATCHING, + expr.span, + &format!("redundant pattern matching, consider using `{}`", good_method), + |diag| { + diag.span_suggestion( + span, + "try this", + format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method), + Applicability::MaybeIncorrect, // snippet + ); + }, + ); + } + } + } + + fn find_good_method_for_match<'a>( + arms: &[Arm<'_>], + path_left: &QPath<'_>, + path_right: &QPath<'_>, + expected_left: &[&str], + expected_right: &[&str], + should_be_left: &'a str, + should_be_right: &'a str, + ) -> Option<&'a str> { + let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) { + (&(*arms[0].body).kind, &(*arms[1].body).kind) + } else if match_qpath(path_right, expected_left) && match_qpath(path_left, expected_right) { + (&(*arms[1].body).kind, &(*arms[0].body).kind) + } else { + return None; + }; + + match body_node_pair { + (ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) { + (LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left), + (LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right), + _ => None, + }, + _ => None, + } + } +} + #[test] fn test_overlapping() { use rustc_span::source_map::DUMMY_SP; @@ -1240,3 +1954,106 @@ fn test_overlapping() { ],) ); } + +/// Implementation of `MATCH_SAME_ARMS`. +fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) { + if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.kind { + let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 { + let mut h = SpanlessHash::new(cx); + h.hash_expr(&arm.body); + h.finish() + }; + + let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool { + let min_index = usize::min(lindex, rindex); + let max_index = usize::max(lindex, rindex); + + let mut local_map: FxHashMap = FxHashMap::default(); + let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| { + if_chain! { + if let Some(a_id) = path_to_local(a); + if let Some(b_id) = path_to_local(b); + let entry = match local_map.entry(a_id) { + Entry::Vacant(entry) => entry, + // check if using the same bindings as before + Entry::Occupied(entry) => return *entry.get() == b_id, + }; + // the names technically don't have to match; this makes the lint more conservative + if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id); + if TyS::same_type(cx.typeck_results().expr_ty(a), cx.typeck_results().expr_ty(b)); + if pat_contains_local(lhs.pat, a_id); + if pat_contains_local(rhs.pat, b_id); + then { + entry.insert(b_id); + true + } else { + false + } + } + }; + // Arms with a guard are ignored, those can’t always be merged together + // This is also the case for arms in-between each there is an arm with a guard + (min_index..=max_index).all(|index| arms[index].guard.is_none()) + && SpanlessEq::new(cx) + .expr_fallback(eq_fallback) + .eq_expr(&lhs.body, &rhs.body) + // these checks could be removed to allow unused bindings + && bindings_eq(lhs.pat, local_map.keys().copied().collect()) + && bindings_eq(rhs.pat, local_map.values().copied().collect()) + }; + + let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect(); + for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) { + span_lint_and_then( + cx, + MATCH_SAME_ARMS, + j.body.span, + "this `match` has identical arm bodies", + |diag| { + diag.span_note(i.body.span, "same as this"); + + // Note: this does not use `span_suggestion` on purpose: + // there is no clean way + // to remove the other arm. Building a span and suggest to replace it to "" + // makes an even more confusing error message. Also in order not to make up a + // span for the whole pattern, the suggestion is only shown when there is only + // one pattern. The user should know about `|` if they are already using it… + + let lhs = snippet(cx, i.pat.span, ""); + let rhs = snippet(cx, j.pat.span, ""); + + if let PatKind::Wild = j.pat.kind { + // if the last arm is _, then i could be integrated into _ + // note that i.pat cannot be _, because that would mean that we're + // hiding all the subsequent arms, and rust won't compile + diag.span_note( + i.body.span, + &format!( + "`{}` has the same arm body as the `_` wildcard, consider removing it", + lhs + ), + ); + } else { + diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs)); + } + }, + ); + } + } +} + +fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool { + let mut result = false; + pat.walk_short(|p| { + result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id); + !result + }); + result +} + +/// Returns true if all the bindings in the `Pat` are in `ids` and vice versa +fn bindings_eq(pat: &Pat<'_>, mut ids: FxHashSet) -> bool { + let mut result = true; + pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id)); + result && ids.is_empty() +}