X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=clippy_lints%2Fsrc%2Fmatches.rs;h=a183d0c66e8ced59d9da785a2e9b2d18ef4545b2;hb=21da42ce29c33e4a33b215a93b19bf8b5f06228d;hp=b754a45aa404fff34f544e54dceee07490e24c46;hpb=245b006a2e9453307443356d511e9e89967cfef9;p=rust.git diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs index b754a45aa40..a183d0c66e8 100644 --- a/clippy_lints/src/matches.rs +++ b/clippy_lints/src/matches.rs @@ -1,42 +1,54 @@ -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::consts::{constant, miri_to_const, Constant}; +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::higher; +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_expn_of, is_lang_ctor, is_lint_allowed, is_refutable, is_wild, meets_msrv, msrvs, + 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 core::array; +use core::iter::{once, ExactSizeIterator}; use if_chain::if_chain; -use rustc_ast::ast::LitKind; +use rustc_ast::ast::{Attribute, LitKind}; use rustc_errors::Applicability; -use rustc_hir::def::CtorKind; +use rustc_hir::def::{CtorKind, DefKind, Res}; +use rustc_hir::LangItem::{OptionNone, OptionSome}; 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_hir::{HirIdMap, HirIdSet}; 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` + /// ### What it does + /// Checks for matches with a single arm where an `if let` /// will usually suffice. /// - /// **Why is this bad?** Just readability – `if let` nests less than a `match`. - /// - /// **Known problems:** None. + /// ### Why is this bad? + /// Just readability – `if let` nests less than a `match`. /// - /// **Example:** + /// ### Example /// ```rust /// # fn bar(stool: &str) {} /// # let x = Some("abc"); - /// /// // Bad /// match x { /// Some(ref foo) => bar(foo), @@ -54,15 +66,17 @@ } declare_clippy_lint! { - /// **What it does:** Checks for matches with two arms where an `if let else` will + /// ### What it does + /// Checks for matches with two arms where an `if let else` will /// usually suffice. /// - /// **Why is this bad?** Just readability – `if let` nests less than a `match`. - /// - /// **Known problems:** Personal style preferences may differ. + /// ### Why is this bad? + /// Just readability – `if let` nests less than a `match`. /// - /// **Example:** + /// ### Known problems + /// Personal style preferences may differ. /// + /// ### Example /// Using `match`: /// /// ```rust @@ -93,16 +107,16 @@ } declare_clippy_lint! { - /// **What it does:** Checks for matches where all arms match a reference, + /// ### What it does + /// Checks for matches where all arms match a reference, /// suggesting to remove the reference and deref the matched expression /// instead. It also checks for `if let &foo = bar` blocks. /// - /// **Why is this bad?** It just makes the code less readable. That reference + /// ### Why is this bad? + /// It just makes the code less readable. That reference /// destructuring adds nothing to the code. /// - /// **Known problems:** None. - /// - /// **Example:** + /// ### Example /// ```rust,ignore /// // Bad /// match x { @@ -124,14 +138,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for matches where match expression is a `bool`. It + /// ### What it does + /// Checks for matches where match expression is a `bool`. It /// suggests to replace the expression with an `if...else` block. /// - /// **Why is this bad?** It makes the code less readable. - /// - /// **Known problems:** None. + /// ### Why is this bad? + /// It makes the code less readable. /// - /// **Example:** + /// ### Example /// ```rust /// # fn foo() {} /// # fn bar() {} @@ -158,14 +172,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for overlapping match arms. + /// ### What it does + /// Checks for overlapping match arms. /// - /// **Why is this bad?** It is likely to be an error and if not, makes the code + /// ### Why is this bad? + /// It is likely to be an error and if not, makes the code /// less obvious. /// - /// **Known problems:** None. - /// - /// **Example:** + /// ### Example /// ```rust /// let x = 5; /// match x { @@ -180,15 +194,15 @@ } declare_clippy_lint! { - /// **What it does:** Checks for arm which matches all errors with `Err(_)` + /// ### 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, similar to + /// ### Why is this bad? + /// It is generally a bad practice, similar to /// catching all exceptions in java with `catch(Exception)` /// - /// **Known problems:** None. - /// - /// **Example:** + /// ### Example /// ```rust /// let x: Result = Ok(3); /// match x { @@ -202,14 +216,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for match which is used to add a reference to an + /// ### What it does + /// Checks for match which is used to add a reference to an /// `Option` value. /// - /// **Why is this bad?** Using `as_ref()` or `as_mut()` instead is shorter. - /// - /// **Known problems:** None. + /// ### Why is this bad? + /// Using `as_ref()` or `as_mut()` instead is shorter. /// - /// **Example:** + /// ### Example /// ```rust /// let x: Option<()> = None; /// @@ -228,18 +242,20 @@ } declare_clippy_lint! { - /// **What it does:** Checks for wildcard enum matches using `_`. + /// ### What it does + /// Checks for wildcard enum matches using `_`. /// - /// **Why is this bad?** New enum variants added by library updates can be missed. + /// ### Why is this bad? + /// New enum variants added by library updates can be missed. /// - /// **Known problems:** Suggested replacements may be incorrect if guards exhaustively cover some + /// ### Known problems + /// Suggested replacements may be incorrect if guards exhaustively cover some /// variants, and also may not use correct path to enum if it's not present in the current scope. /// - /// **Example:** + /// ### Example /// ```rust /// # enum Foo { A(usize), B(usize) } /// # let x = Foo::B(1); - /// /// // Bad /// match x { /// Foo::A(_) => {}, @@ -258,15 +274,17 @@ } declare_clippy_lint! { - /// **What it does:** Checks for wildcard enum matches for a single variant. + /// ### 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. + /// ### 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 + /// ### Known problems + /// Suggested replacements may not use correct path to enum /// if it's not present in the current scope. /// - /// **Example:** - /// + /// ### Example /// ```rust /// # enum Foo { A, B, C } /// # let x = Foo::B; @@ -290,14 +308,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for wildcard pattern used with others patterns in same match arm. + /// ### What it does + /// Checks for wildcard pattern used with others patterns in same match arm. /// - /// **Why is this bad?** Wildcard pattern already covers any other pattern as it will match anyway. + /// ### Why is this bad? + /// Wildcard pattern already covers any other pattern as it will match anyway. /// It makes the code less readable, especially to spot wildcard pattern use in match arm. /// - /// **Known problems:** None. - /// - /// **Example:** + /// ### Example /// ```rust /// // Bad /// match "foo" { @@ -317,14 +335,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for matches being used to destructure a single-variant enum + /// ### What it does + /// Checks for matches being used to destructure a single-variant enum /// or tuple struct where a `let` will suffice. /// - /// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does. - /// - /// **Known problems:** None. + /// ### Why is this bad? + /// Just readability – `let` doesn't nest, whereas a `match` does. /// - /// **Example:** + /// ### Example /// ```rust /// enum Wrapper { /// Data(i32), @@ -352,14 +370,17 @@ } declare_clippy_lint! { - /// **What it does:** Checks for useless match that binds to only one value. + /// ### What it does + /// Checks for useless match that binds to only one value. /// - /// **Why is this bad?** Readability and needless complexity. + /// ### Why is this bad? + /// Readability and needless complexity. /// - /// **Known problems:** Suggested replacements may be incorrect when `match` + /// ### Known problems + /// Suggested replacements may be incorrect when `match` /// is actually binding temporary value, bringing a 'dropped while borrowed' error. /// - /// **Example:** + /// ### Example /// ```rust /// # let a = 1; /// # let b = 2; @@ -380,14 +401,14 @@ } declare_clippy_lint! { - /// **What it does:** Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched. + /// ### What it does + /// Checks for unnecessary '..' pattern binding on struct when all fields are explicitly matched. /// - /// **Why is this bad?** Correctness and readability. It's like having a wildcard pattern after + /// ### Why is this bad? + /// Correctness and readability. It's like having a wildcard pattern after /// matching all enum variants explicitly. /// - /// **Known problems:** None. - /// - /// **Example:** + /// ### Example /// ```rust /// # struct A { a: i32 } /// let a = A { a: 5 }; @@ -409,11 +430,157 @@ "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 + /// This will change the drop order for the matched type. Both `if let` and + /// `while let` will drop the value at the end of the block, both `if` and `while` will drop the + /// value before entering the block. For most types this change will not matter, but for a few + /// types this will not be an acceptable change (e.g. locks). See the + /// [reference](https://doc.rust-lang.org/reference/destructors.html#drop-scopes) for more about + /// drop order. + /// + /// ### 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, @@ -427,15 +594,29 @@ pub struct Matches { 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<'tcx> LateLintPass<'tcx> for Matches { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { - if in_external_macro(cx.sess(), expr.span) { + if in_external_macro(cx.sess(), expr.span) || in_macro(expr.span) { return; } - if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind { + + redundant_pattern_match::check(cx, expr); + + if meets_msrv(self.msrv.as_ref(), &msrvs::MATCHES_MACRO) { + if !check_match_like_matches(cx, expr) { + lint_match_arms(cx, expr); + } + } else { + lint_match_arms(cx, expr); + } + + if let ExprKind::Match(ex, arms, MatchSource::Normal) = expr.kind { check_single_match(cx, ex, arms, expr); check_match_bool(cx, ex, arms, expr); check_overlapping_arms(cx, ex, arms); @@ -451,7 +632,10 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { } } if let ExprKind::Match(ref ex, ref arms, _) = expr.kind { - check_match_ref_pats(cx, ex, arms, expr); + check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr); + } + if let Some(higher::IfLet { let_pat, let_expr, .. }) = higher::IfLet::hir(expr) { + check_match_ref_pats(cx, let_expr, once(let_pat), expr); } } @@ -459,15 +643,15 @@ 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); - if let Some(ref expr) = local.init; - if let ExprKind::Match(ref target, ref arms, MatchSource::Normal) = expr.kind; + if let Some(expr) = local.init; + if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind; if arms.len() == 1 && arms[0].guard.is_none(); if let PatKind::TupleStruct( - QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pat.kind; + QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind; if args.len() == 1; - if let Some(arg) = get_arg_name(&args[0]); - let body = remove_blocks(&arms[0].body); - if match_var(body, arg); + if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind; + let body = remove_blocks(arms[0].body); + if path_to_local_id(body, arg); then { let mut applicability = Applicability::MachineApplicable; @@ -495,11 +679,10 @@ 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(_, 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(); @@ -515,6 +698,8 @@ fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) { } } } + + extract_msrv_attr!(LateContext); } #[rustfmt::skip] @@ -530,18 +715,23 @@ fn check_single_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], exp // 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_lint_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); } @@ -555,7 +745,7 @@ fn check_single_match_single_pattern( expr: &Expr<'_>, els: Option<&Expr<'_>>, ) { - if is_wild(&arms[1].pat) { + if is_wild(arms[1].pat) { report_single_match_single_pattern(cx, ex, arms, expr, els); } } @@ -571,20 +761,63 @@ 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 (pat, pat_ref_count) = peel_hir_pat_refs(arms[0].pat); + let (msg, sugg) = if_chain! { + 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(spe_trait_id) = cx.tcx.lang_items().structural_peq_trait(); + if let Some(pe_trait_id) = cx.tcx.lang_items().eq_trait(); + if ty.is_integral() || ty.is_char() || ty.is_str() + || (implements_trait(cx, ty, spe_trait_id, &[]) + && implements_trait(cx, ty, pe_trait_id, &[ty.into()])); + 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, ); } @@ -609,7 +842,7 @@ fn check_single_match_opt_like( ]; let path = match arms[1].pat.kind { - PatKind::TupleStruct(ref path, ref inner, _) => { + PatKind::TupleStruct(ref path, inner, _) => { // Contains any non wildcard patterns (e.g., `Err(err)`)? if !inner.iter().all(is_wild) { return; @@ -632,7 +865,7 @@ fn check_single_match_opt_like( 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, @@ -641,7 +874,7 @@ fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: move |diag| { if arms.len() == 2 { // no guards - let exprs = if let PatKind::Lit(ref arm_bool) = arms[0].pat.kind { + let exprs = if let PatKind::Lit(arm_bool) = arms[0].pat.kind { if let ExprKind::Lit(ref lit) = arm_bool.kind { match lit.node { LitKind::Bool(true) => Some((&*arms[0].body, &*arms[1].body)), @@ -695,8 +928,8 @@ fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: } fn check_overlapping_arms<'tcx>(cx: &LateContext<'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)); + 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) { @@ -713,29 +946,31 @@ fn check_overlapping_arms<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms } } -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 { + if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind { let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)); if path_str == "Err" { let mut matching_wild = inner.iter().any(is_wild); let mut ident_bind_name = String::from("_"); 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) { + for pat in inner.iter() { + 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; } } - }); + } } if_chain! { if matching_wild; - if let ExprKind::Block(ref block, _) = arm.body.kind; + if let ExprKind::Block(block, _) = arm.body.kind; if is_panic_block(block); then { // `Err(_)` or `Err(_e)` arm with `panic!` found @@ -754,129 +989,195 @@ 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 => (), + } } +} + +fn is_hidden(cx: &LateContext<'_>, variant_def: &VariantDef) -> bool { + let attrs = cx.tcx.get_attrs(variant_def.def_id); + clippy_utils::attrs::is_doc_hidden(attrs) || clippy_utils::attrs::is_unstable(attrs) +} + +#[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 has_hidden = adt_def.variants.iter().any(|x| is_hidden(cx, x)); + let mut missing_variants: Vec<_> = adt_def.variants.iter().filter(|x| !is_hidden(cx, x)).collect(); - let mut missing_variants = vec![]; - if let ty::Adt(def, _) = ty.kind { - for variant in &def.variants { - missing_variants.push(variant); - } - } - - 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, ref patterns, ..) = arm.pat.kind { - if let QPath::Resolved(_, p) = path { - // Some simple checks for exhaustive patterns. - // There is a room for improvements to detect more cases, - // but it can be more expensive to do so. - let is_pattern_exhaustive = |pat: &&Pat<'_>| { - if let PatKind::Wild | PatKind::Binding(.., None) = pat.kind { - true - } else { - false - } + 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 patterns.iter().all(is_pattern_exhaustive) { - missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id())); + if arm.guard.is_none() { + missing_variants.retain(|e| e.ctor_def_id != Some(id)); } - } + path + }, + PatKind::TupleStruct(path, patterns, ..) => { + if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() { + if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p)) { + missing_variants.retain(|e| e.ctor_def_id != Some(id)); + } + } + path + }, + PatKind::Struct(path, patterns, ..) => { + if let Some(id) = cx.qpath_res(path, pat.hir_id).opt_def_id() { + if arm.guard.is_none() && patterns.iter().all(|p| !is_refutable(cx, p.pat)) { + 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), + _ => (), } - } - - 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("_")); + 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 => "{ .. }", } - } + ) + }; + + match missing_variants.as_slice() { + [] => (), + [x] if !adt_def.is_variant_list_non_exhaustive() && !has_hidden => span_lint_and_sugg( + cx, + MATCH_WILDCARD_FOR_SINGLE_VARIANTS, + wildcard_span, + "wildcard matches only a single variant and will also match any future added variants", + "try this", + format_suggestion(x), + Applicability::MaybeIncorrect, + ), + variants => { + let mut suggestions: Vec<_> = variants.iter().copied().map(format_suggestion).collect(); + let message = if adt_def.is_variant_list_non_exhaustive() || has_hidden { + suggestions.push("_".into()); + "wildcard matches known variants and will also match future added variants" + } else { + "wildcard match will also match any future added variants" + }; - if suggestion.len() == 1 { - // No need to check for non-exhaustive enum as in that case len would be greater than 1 span_lint_and_sugg( cx, - MATCH_WILDCARD_FOR_SINGLE_VARIANTS, + WILDCARD_ENUM_MATCH_ARM, wildcard_span, message, "try this", - suggestion[0].clone(), + suggestions.join(" | "), Applicability::MaybeIncorrect, - ) - }; - - span_lint_and_sugg( - cx, - WILDCARD_ENUM_MATCH_ARM, - wildcard_span, - message, - "try this", - suggestion.join(" | "), - Applicability::MaybeIncorrect, - ) - } + ); + }, + }; } // If the block contains only a `panic!` macro (as expression or statement) fn is_panic_block(block: &Block<'_>) -> bool { match (&block.expr, block.stmts.len(), block.stmts.first()) { - (&Some(ref exp), 0, _) => { - is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none() - }, + (&Some(exp), 0, _) => is_expn_of(exp.span, "panic").is_some() && is_expn_of(exp.span, "unreachable").is_none(), (&None, 1, Some(stmt)) => { is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none() }, @@ -884,47 +1185,48 @@ fn is_panic_block(block: &Block<'_>) -> bool { } } -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 { - let span = ex.span.source_callsite(); - suggs.push((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string())); - ( - "you don't need to add `&` to both the expression and the patterns", - "try", - ) - } else { - let span = ex.span.source_callsite(); - suggs.push((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string())); - ( - "you don't need to add `&` to all patterns", - "instead of prefixing all patterns with `&`, you can dereference the expression", - ) - }; - - suggs.extend(arms.iter().filter_map(|a| { - if let PatKind::Ref(ref refp, _) = a.pat.kind { - Some((a.pat.span, snippet(cx, refp.span, "..").to_string())) - } else { - None - } - })); +fn check_match_ref_pats<'a, 'b, I>(cx: &LateContext<'_>, ex: &Expr<'_>, pats: I, expr: &Expr<'_>) +where + 'b: 'a, + I: Clone + Iterator>, +{ + if !has_only_ref_pats(pats.clone()) { + return; + } - span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| { - if !expr.span.from_expansion() { - multispan_sugg(diag, msg, suggs); - } - }); + let (first_sugg, msg, title); + let span = ex.span.source_callsite(); + if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, ref inner) = ex.kind { + first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, inner, "..").to_string())); + msg = "try"; + title = "you don't need to add `&` to both the expression and the patterns"; + } else { + first_sugg = once((span, Sugg::hir_with_macro_callsite(cx, ex, "..").deref().to_string())); + msg = "instead of prefixing all patterns with `&`, you can dereference the expression"; + title = "you don't need to add `&` to all patterns"; } + + let remaining_suggs = pats.filter_map(|pat| { + if let PatKind::Ref(ref refp, _) = pat.kind { + Some((pat.span, snippet(cx, refp.span, "..").to_string())) + } else { + None + } + }); + + span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| { + if !expr.span.from_expansion() { + multispan_sugg(diag, msg, first_sugg.chain(remaining_suggs)); + } + }); } 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]) - } else if is_none_arm(&arms[1]) { - is_ref_some_arm(&arms[0]) + let arm_ref: Option = if is_none_arm(cx, &arms[0]) { + is_ref_some_arm(cx, &arms[1]) + } else if is_none_arm(cx, &arms[1]) { + is_ref_some_arm(cx, &arms[0]) } else { None }; @@ -935,15 +1237,15 @@ fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], exp "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 _)" @@ -966,36 +1268,210 @@ fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], exp cast, ), applicability, - ) + ); } } } fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) { for arm in arms { - if let PatKind::Or(ref fields) = arm.pat.kind { + if let PatKind::Or(fields) = arm.pat.kind { // look for multiple fields in this arm that contains at least one Wild pattern if fields.len() > 1 && fields.iter().any(is_wild) { span_lint_and_help( 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", ); } } } } +/// 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 Some(higher::IfLet { + let_pat, + let_expr, + if_then, + if_else: Some(if_else), + }) = higher::IfLet::hir(expr) + { + return find_matches_sugg( + cx, + let_expr, + array::IntoIter::new([(&[][..], Some(let_pat), if_then, None), (&[][..], None, if_else, None)]), + expr, + true, + ); + } + + if let ExprKind::Match(scrut, arms, MatchSource::Normal) = expr.kind { + return find_matches_sugg( + cx, + scrut, + arms.iter().map(|arm| { + ( + cx.tcx.hir().attrs(arm.hir_id), + Some(arm.pat), + arm.body, + arm.guard.as_ref(), + ) + }), + expr, + false, + ); + } + + false +} + +/// Lint a `match` or `if let` for replacement by `matches!` +fn find_matches_sugg<'a, 'b, I>( + cx: &LateContext<'_>, + ex: &Expr<'_>, + mut iter: I, + expr: &Expr<'_>, + is_if_let: bool, +) -> bool +where + 'b: 'a, + I: Clone + + DoubleEndedIterator + + ExactSizeIterator + + Iterator< + Item = ( + &'a [Attribute], + Option<&'a Pat<'b>>, + &'a Expr<'b>, + Option<&'a Guard<'b>>, + ), + >, +{ + if_chain! { + if iter.len() >= 2; + if cx.typeck_results().expr_ty(expr).is_bool(); + if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back(); + let iter_without_last = iter.clone(); + if let Some((first_attrs, _, first_expr, first_guard)) = iter.next(); + if let Some(b0) = find_bool_lit(&first_expr.kind, is_if_let); + if let Some(b1) = find_bool_lit(&last_expr.kind, is_if_let); + if b0 != b1; + if first_guard.is_none() || iter.len() == 0; + if first_attrs.is_empty(); + if iter + .all(|arm| { + find_bool_lit(&arm.2.kind, is_if_let).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty() + }); + then { + if let Some(ref last_pat) = last_pat_opt { + if !is_wild(last_pat) { + return false; + } + } + + // 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 _; + iter_without_last + .filter_map(|arm| { + let pat_span = arm.1?.span; + Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability)) + }) + .join(" | ") + }; + let pat_and_guard = if let Some(Guard::If(g)) = first_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 is_if_let { "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<'_>, is_if_let: bool) -> Option { + match ex { + ExprKind::Lit(Spanned { + node: LitKind::Bool(b), .. + }) => Some(*b), + ExprKind::Block( + rustc_hir::Block { + stmts: &[], + expr: Some(exp), + .. + }, + _, + ) if is_if_let => { + 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); + let match_body = remove_blocks(arms[0].body); let mut snippet_body = if match_body.span.from_expansion() { Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string() } else { @@ -1006,13 +1482,13 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A 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(';'); } }, @@ -1045,7 +1521,18 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A 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!( @@ -1070,15 +1557,34 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A ); }, PatKind::Wild => { - span_lint_and_sugg( - cx, - MATCH_SINGLE_BINDING, - expr.span, - "this match could be replaced by its body itself", - "consider using the match body instead", - snippet_body, - Applicability::MachineApplicable, - ); + if ex.can_have_side_effects() { + let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0)); + let sugg = format!( + "{};\n{}{}", + snippet_with_applicability(cx, ex.span, "..", &mut applicability), + indent, + snippet_body + ); + span_lint_and_sugg( + cx, + MATCH_SINGLE_BINDING, + expr.span, + "this match could be replaced by its scrutinee and body", + "consider using the scrutinee and body instead", + sugg, + applicability, + ); + } else { + span_lint_and_sugg( + cx, + MATCH_SINGLE_BINDING, + expr.span, + "this match could be replaced by its body itself", + "consider using the match body instead", + snippet_body, + Applicability::MachineApplicable, + ); + } }, _ => (), } @@ -1086,8 +1592,8 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A /// 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>> { + let map = &cx.tcx.hir(); if_chain! { - let map = &cx.tcx.hir(); if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id)); if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id)); then { @@ -1100,18 +1606,15 @@ fn opt_parent_let<'a>(cx: &LateContext<'a>, ex: &Expr<'a>) -> Option<&'a Local<' /// Gets all arms that are unbounded `PatRange`s. fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) -> Vec> { arms.iter() - .flat_map(|arm| { - if let Arm { - ref pat, guard: None, .. - } = *arm - { + .filter_map(|arm| { + if let Arm { pat, guard: None, .. } = *arm { 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 { @@ -1124,8 +1627,8 @@ fn all_ranges<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>], ty: Ty<'tcx>) }); } - if let PatKind::Lit(ref value) = pat.kind { - let value = constant(cx, cx.tables(), value)?.0; + if let PatKind::Lit(value) = pat.kind { + let value = constant(cx, cx.typeck_results(), value)?.0; return Some(SpannedRange { span: pat.span, node: (value.clone(), Bound::Included(value)), @@ -1171,32 +1674,28 @@ fn type_ranges(ranges: &[SpannedRange]) -> TypedRanges { fn is_unit_expr(expr: &Expr<'_>) -> bool { match expr.kind { - ExprKind::Tup(ref v) if v.is_empty() => true, - ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true, + ExprKind::Tup(v) if v.is_empty() => true, + ExprKind::Block(b, _) if b.stmts.is_empty() && b.expr.is_none() => true, _ => false, } } // 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, - } +fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool { + matches!(arm.pat.kind, PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone)) } // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`) -fn is_ref_some_arm(arm: &Arm<'_>) -> Option { +fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option { if_chain! { - if let PatKind::TupleStruct(ref path, ref pats, _) = arm.pat.kind; - if pats.len() == 1 && match_qpath(path, &paths::OPTION_SOME); - if let PatKind::Binding(rb, .., ident, _) = pats[0].kind; + if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind; + if is_lang_ctor(cx, qpath, OptionSome); + if let PatKind::Binding(rb, .., ident, _) = first_pat.kind; if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut; - if let ExprKind::Call(ref e, ref args) = remove_blocks(&arm.body).kind; + if let ExprKind::Call(e, 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 is_lang_ctor(cx, some_path, OptionSome) && args.len() == 1; + if let ExprKind::Path(QPath::Resolved(_, path2)) = args[0].kind; if path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name; then { return Some(rb) @@ -1205,19 +1704,26 @@ fn is_ref_some_arm(arm: &Arm<'_>) -> Option { None } -fn has_only_ref_pats(arms: &[Arm<'_>]) -> bool { - let mapped = arms - .iter() - .map(|a| { - match a.pat.kind { - PatKind::Ref(..) => Some(true), // &-patterns - PatKind::Wild => Some(false), // an "anything" wildcard is also fine - _ => None, // any other pattern is not fine +fn has_only_ref_pats<'a, 'b, I>(pats: I) -> bool +where + 'b: 'a, + I: Iterator>, +{ + let mut at_least_one_is_true = false; + for opt in pats.map(|pat| match pat.kind { + PatKind::Ref(..) => Some(true), // &-patterns + PatKind::Wild => Some(false), // an "anything" wildcard is also fine + _ => None, // any other pattern is not fine + }) { + if let Some(inner) = opt { + if inner { + at_least_one_is_true = true; } - }) - .collect::>>(); - // look for Some(v) where there's at least one true element - mapped.map_or(false, |v| v.iter().any(|el| *el)) + } else { + return false; + } + } + at_least_one_is_true } pub fn overlapping(ranges: &[SpannedRange]) -> Option<(&SpannedRange, &SpannedRange)> @@ -1278,7 +1784,7 @@ 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.iter().skip(1)) { match (a, b) { (&Kind::Start(_, ra), &Kind::End(_, rb)) => { if ra.node != rb.node { @@ -1286,13 +1792,456 @@ 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::higher; + use clippy_utils::source::{snippet, snippet_with_applicability}; + use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type}; + use clippy_utils::{is_lang_ctor, is_qpath_def_path, is_trait_method, paths}; + use if_chain::if_chain; + use rustc_ast::ast::LitKind; + use rustc_data_structures::fx::FxHashSet; + use rustc_errors::Applicability; + use rustc_hir::LangItem::{OptionNone, OptionSome, PollPending, PollReady, ResultErr, ResultOk}; + use rustc_hir::{ + intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor}, + Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, + }; + use rustc_lint::LateContext; + use rustc_middle::ty::{self, subst::GenericArgKind, Ty}; + use rustc_span::sym; + + pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if let Some(higher::IfLet { + if_else, + let_pat, + let_expr, + .. + }) = higher::IfLet::ast(cx, expr) + { + find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some()) + } + if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind { + find_sugg_for_match(cx, expr, op, arms) + } + if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) { + find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false) + } + } + + /// Checks if the drop order for a type matters. Some std types implement drop solely to + /// deallocate memory. For these types, and composites containing them, changing the drop order + /// won't result in any observable side effects. + fn type_needs_ordered_drop(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool { + type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default()) + } + + fn type_needs_ordered_drop_inner(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet>) -> bool { + if !seen.insert(ty) { + return false; + } + if !ty.needs_drop(cx.tcx, cx.param_env) { + false + } else if !cx + .tcx + .lang_items() + .drop_trait() + .map_or(false, |id| implements_trait(cx, ty, id, &[])) + { + // This type doesn't implement drop, so no side effects here. + // Check if any component type has any. + match ty.kind() { + ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)), + ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen), + ty::Adt(adt, subs) => adt + .all_fields() + .map(|f| f.ty(cx.tcx, subs)) + .any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)), + _ => true, + } + } + // Check for std types which implement drop, but only for memory allocation. + else if is_type_diagnostic_item(cx, ty, sym::vec_type) + || is_type_lang_item(cx, ty, LangItem::OwnedBox) + || is_type_diagnostic_item(cx, ty, sym::Rc) + || is_type_diagnostic_item(cx, ty, sym::Arc) + || is_type_diagnostic_item(cx, ty, sym::cstring_type) + || is_type_diagnostic_item(cx, ty, sym::BTreeMap) + || is_type_diagnostic_item(cx, ty, sym::LinkedList) + || match_type(cx, ty, &paths::WEAK_RC) + || match_type(cx, ty, &paths::WEAK_ARC) + { + // Check all of the generic arguments. + if let ty::Adt(_, subs) = ty.kind() { + subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)) + } else { + true + } + } else { + true + } + } + + // Extract the generic arguments out of a type + fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option> { + if_chain! { + if let ty::Adt(_, subs) = ty.kind(); + if let Some(sub) = subs.get(index); + if let GenericArgKind::Type(sub_ty) = sub.unpack(); + then { + Some(sub_ty) + } else { + None + } + } + } + + // Checks if there are any temporaries created in the given expression for which drop order + // matters. + fn temporaries_need_ordered_drop(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool { + struct V<'a, 'tcx> { + cx: &'a LateContext<'tcx>, + res: bool, + } + impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> { + type Map = ErasedMap<'tcx>; + fn nested_visit_map(&mut self) -> NestedVisitorMap { + NestedVisitorMap::None + } + + fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { + match expr.kind { + // Taking the reference of a value leaves a temporary + // e.g. In `&String::new()` the string is a temporary value. + // Remaining fields are temporary values + // e.g. In `(String::new(), 0).1` the string is a temporary value. + ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => { + if !matches!(expr.kind, ExprKind::Path(_)) { + if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) { + self.res = true; + } else { + self.visit_expr(expr); + } + } + }, + // the base type is alway taken by reference. + // e.g. In `(vec![0])[0]` the vector is a temporary value. + ExprKind::Index(base, index) => { + if !matches!(base.kind, ExprKind::Path(_)) { + if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) { + self.res = true; + } else { + self.visit_expr(base); + } + } + self.visit_expr(index); + }, + // Method calls can take self by reference. + // e.g. In `String::new().len()` the string is a temporary value. + ExprKind::MethodCall(_, _, [self_arg, args @ ..], _) => { + if !matches!(self_arg.kind, ExprKind::Path(_)) { + let self_by_ref = self + .cx + .typeck_results() + .type_dependent_def_id(expr.hir_id) + .map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref()); + if self_by_ref + && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg)) + { + self.res = true; + } else { + self.visit_expr(self_arg); + } + } + args.iter().for_each(|arg| self.visit_expr(arg)); + }, + // Either explicitly drops values, or changes control flow. + ExprKind::DropTemps(_) + | ExprKind::Ret(_) + | ExprKind::Break(..) + | ExprKind::Yield(..) + | ExprKind::Block(Block { expr: None, .. }, _) + | ExprKind::Loop(..) => (), + + // Only consider the final expression. + ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr), + + _ => walk_expr(self, expr), + } + } + } + + let mut v = V { cx, res: false }; + v.visit_expr(expr); + v.res + } + + fn find_sugg_for_if_let<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + let_pat: &Pat<'_>, + let_expr: &'tcx Expr<'_>, + keyword: &'static str, + has_else: bool, + ) { + // also look inside refs + let mut kind = &let_pat.kind; + // if we have &None for example, peel it so we can detect "if let None = x" + if let PatKind::Ref(inner, _mutability) = kind { + kind = &inner.kind; + } + let op_ty = cx.typeck_results().expr_ty(let_expr); + // Determine which function should be used, and the type contained by the corresponding + // variant. + let (good_method, inner_ty) = match kind { + PatKind::TupleStruct(ref path, [sub_pat], _) => { + if let PatKind::Wild = sub_pat.kind { + if is_lang_ctor(cx, path, ResultOk) { + ("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty)) + } else if is_lang_ctor(cx, path, ResultErr) { + ("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty)) + } else if is_lang_ctor(cx, path, OptionSome) { + ("is_some()", op_ty) + } else if is_lang_ctor(cx, path, PollReady) { + ("is_ready()", op_ty) + } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V4) { + ("is_ipv4()", op_ty) + } else if is_qpath_def_path(cx, path, sub_pat.hir_id, &paths::IPADDR_V6) { + ("is_ipv6()", op_ty) + } else { + return; + } + } else { + return; + } + }, + PatKind::Path(ref path) => { + let method = if is_lang_ctor(cx, path, OptionNone) { + "is_none()" + } else if is_lang_ctor(cx, path, PollPending) { + "is_pending()" + } else { + return; + }; + // `None` and `Pending` don't have an inner type. + (method, cx.tcx.types.unit) + }, + _ => return, + }; + + // If this is the last expression in a block or there is an else clause then the whole + // type needs to be considered, not just the inner type of the branch being matched on. + // Note the last expression in a block is dropped after all local bindings. + let check_ty = if has_else + || (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..))))) + { + op_ty + } else { + inner_ty + }; + + // All temporaries created in the scrutinee expression are dropped at the same time as the + // scrutinee would be, so they have to be considered as well. + // e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held + // for the duration if body. + let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr); + + // check that `while_let_on_iterator` lint does not trigger + if_chain! { + if keyword == "while"; + if let ExprKind::MethodCall(method_path, _, _, _) = let_expr.kind; + if method_path.ident.name == sym::next; + if is_trait_method(cx, let_expr, sym::Iterator); + then { + return; + } + } + + let result_expr = match &let_expr.kind { + ExprKind::AddrOf(_, _, borrowed) => borrowed, + _ => let_expr, + }; + span_lint_and_then( + cx, + REDUNDANT_PATTERN_MATCHING, + let_pat.span, + &format!("redundant pattern matching, consider using `{}`", good_method), + |diag| { + // if/while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + let expr_span = expr.span; + + // if/while let ... = ... { ... } + // ^^^ + let op_span = result_expr.span.source_callsite(); + + // if/while let ... = ... { ... } + // ^^^^^^^^^^^^^^^^^^^ + let span = expr_span.until(op_span.shrink_to_hi()); + + let mut app = if needs_drop { + Applicability::MaybeIncorrect + } else { + Applicability::MachineApplicable + }; + let sugg = snippet_with_applicability(cx, op_span, "_", &mut app); + + diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app); + + if needs_drop { + diag.note("this will change drop order of the result, as well as all temporaries"); + diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important"); + } + }, + ); + } + + 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, patterns_left, _), + PatKind::TupleStruct(ref path_right, 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( + cx, + arms, + path_left, + path_right, + &paths::RESULT_OK, + &paths::RESULT_ERR, + "is_ok()", + "is_err()", + ) + .or_else(|| { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::IPADDR_V4, + &paths::IPADDR_V6, + "is_ipv4()", + "is_ipv6()", + ) + }) + } else { + None + } + }, + (PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right)) + | (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _)) + if patterns.len() == 1 => + { + if let PatKind::Wild = patterns[0].kind { + find_good_method_for_match( + cx, + arms, + path_left, + path_right, + &paths::OPTION_SOME, + &paths::OPTION_NONE, + "is_some()", + "is_none()", + ) + .or_else(|| { + find_good_method_for_match( + cx, + 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 + ); + }, + ); + } + } + } + + #[allow(clippy::too_many_arguments)] + fn find_good_method_for_match<'a>( + cx: &LateContext<'_>, + 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 is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, expected_left) + && is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_right) + { + (&(*arms[0].body).kind, &(*arms[1].body).kind) + } else if is_qpath_def_path(cx, path_right, arms[1].pat.hir_id, expected_left) + && is_qpath_def_path(cx, path_left, arms[0].pat.hir_id, 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; @@ -1329,3 +2278,107 @@ fn test_overlapping() { ],) ); } + +/// Implementation of `MATCH_SAME_ARMS`. +fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) { + if let ExprKind::Match(_, 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: HirIdMap = HirIdMap::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,)) + .help("...or consider changing the match arm bodies"); + } + }, + ); + } + } +} + +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: HirIdSet) -> bool { + let mut result = true; + pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id)); + result && ids.is_empty() +}