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, }; use if_chain::if_chain; use rustc_ast::ast::LitKind; use rustc_errors::Applicability; use rustc_hir::def::CtorKind; use rustc_hir::{ Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Guard, Local, MatchSource, Mutability, Node, Pat, PatKind, QPath, RangeEnd, }; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::lint::in_external_macro; use rustc_middle::ty::{self, Ty}; use rustc_session::{declare_tool_lint, impl_lint_pass}; use rustc_span::source_map::{Span, Spanned}; use std::cmp::Ordering; use std::collections::Bound; declare_clippy_lint! { /// **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. /// /// **Example:** /// ```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, "a `match` statement with a single nontrivial arm (i.e., where the other arm is `_ => {}`) instead of `if let`" } declare_clippy_lint! { /// **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. /// /// **Example:** /// /// Using `match`: /// /// ```rust /// # fn bar(foo: &usize) {} /// # let other_ref: usize = 1; /// # let x: Option<&usize> = Some(&1); /// match x { /// Some(ref foo) => bar(foo), /// _ => bar(&other_ref), /// } /// ``` /// /// Using `if let` with `else`: /// /// ```rust /// # fn bar(foo: &usize) {} /// # let other_ref: usize = 1; /// # let x: Option<&usize> = Some(&1); /// if let Some(ref foo) = x { /// bar(foo); /// } else { /// bar(&other_ref); /// } /// ``` pub SINGLE_MATCH_ELSE, pedantic, "a `match` statement with two arms where the second arm's pattern is a placeholder instead of a specific match pattern" } declare_clippy_lint! { /// **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 /// destructuring adds nothing to the code. /// /// **Known problems:** None. /// /// **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, "a `match` or `if let` with all arms prefixed with `&` instead of deref-ing the match expression" } declare_clippy_lint! { /// **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. /// /// **Example:** /// ```rust /// # fn foo() {} /// # fn bar() {} /// let condition: bool = true; /// match condition { /// true => foo(), /// false => bar(), /// } /// ``` /// Use if/else instead: /// ```rust /// # fn foo() {} /// # fn bar() {} /// let condition: bool = true; /// if condition { /// foo(); /// } else { /// bar(); /// } /// ``` pub MATCH_BOOL, pedantic, "a `match` on a boolean expression instead of an `if..else` block" } declare_clippy_lint! { /// **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 /// less obvious. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let x = 5; /// match x { /// 1...10 => println!("1 ... 10"), /// 5...15 => println!("5 ... 15"), /// _ => (), /// } /// ``` pub MATCH_OVERLAPPING_ARM, style, "a `match` with overlapping arms" } declare_clippy_lint! { /// **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 /// catching all exceptions in java with `catch(Exception)` /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let x: Result = Ok(3); /// match x { /// Ok(_) => println!("ok"), /// Err(_) => panic!("err"), /// } /// ``` pub MATCH_WILD_ERR_ARM, pedantic, "a `match` with `Err(_)` arm and take drastic actions" } declare_clippy_lint! { /// **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. /// /// **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, "a `match` on an Option value instead of using `as_ref()` or `as_mut`" } declare_clippy_lint! { /// **What it does:** Checks for wildcard enum matches using `_`. /// /// **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 /// variants, and also may not use correct path to enum if it's not present in the current scope. /// /// **Example:** /// ```rust /// # enum Foo { A(usize), B(usize) } /// # let x = Foo::B(1); /// /// // Bad /// match x { /// 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. /// /// **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:** /// ```rust /// // Bad /// match "foo" { /// "a" => {}, /// "bar" | _ => {}, /// } /// /// // Good /// match "foo" { /// "a" => {}, /// _ => {}, /// } /// ``` pub WILDCARD_IN_OR_PATTERNS, complexity, "a wildcard pattern used with others patterns in same match arm" } declare_clippy_lint! { /// **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. /// /// **Example:** /// ```rust /// enum Wrapper { /// Data(i32), /// } /// /// let wrapper = Wrapper::Data(42); /// /// let data = match wrapper { /// Wrapper::Data(i) => i, /// }; /// ``` /// /// The correct use would be: /// ```rust /// enum Wrapper { /// Data(i32), /// } /// /// let wrapper = Wrapper::Data(42); /// let Wrapper::Data(data) = wrapper; /// ``` pub INFALLIBLE_DESTRUCTURING_MATCH, style, "a `match` statement with a single infallible arm instead of a `let`" } declare_clippy_lint! { /// **What it does:** Checks for useless match that binds to only one value. /// /// **Why is this bad?** Readability and needless complexity. /// /// **Known problems:** Suggested replacements may be incorrect when `match` /// is actually binding temporary value, bringing a 'dropped while borrowed' error. /// /// **Example:** /// ```rust /// # let a = 1; /// # let b = 2; /// /// // Bad /// match (a, b) { /// (c, d) => { /// // useless match /// } /// } /// /// // Good /// let (c, d) = (a, b); /// ``` pub MATCH_SINGLE_BINDING, complexity, "a match with a single binding instead of using `let` statement" } declare_clippy_lint! { /// **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 /// matching all enum variants explicitly. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// # struct A { a: i32 } /// let a = A { a: 5 }; /// /// // Bad /// match a { /// A { a: 5, .. } => {}, /// _ => {}, /// } /// /// // Good /// match a { /// A { a: 5 } => {}, /// _ => {}, /// } /// ``` pub REST_PAT_IN_FULLY_BOUND_STRUCTS, restriction, "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` or /// `Option` /// /// **Why is this bad?** It's more concise and clear to just use the proper /// utility function /// /// **Known problems:** None. /// /// **Example:** /// /// ```rust /// if let Ok(_) = Ok::(42) {} /// if let Err(_) = Err::(42) {} /// if let None = None::<()> {} /// if let Some(_) = Some(42) {} /// match Ok::(42) { /// Ok(_) => true, /// Err(_) => false, /// }; /// ``` /// /// The more idiomatic use would be: /// /// ```rust /// if Ok::(42).is_ok() {} /// if Err::(42).is_err() {} /// if None::<()>.is_none() {} /// if Some(42).is_some() {} /// 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:** None /// /// **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" } #[derive(Default)] pub struct Matches { infallible_destructuring_match_linted: bool, } impl_lint_pass!(Matches => [ SINGLE_MATCH, MATCH_REF_PATS, MATCH_BOOL, SINGLE_MATCH_ELSE, MATCH_OVERLAPPING_ARM, 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, REDUNDANT_PATTERN_MATCHING, MATCH_LIKE_MATCHES_MACRO ]); 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); check_match_like_matches(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); check_overlapping_arms(cx, ex, arms); check_wild_err_arm(cx, ex, arms); check_wild_enum_match(cx, ex, arms); check_match_as_ref(cx, ex, arms, expr); check_wild_in_or_pats(cx, arms); if self.infallible_destructuring_match_linted { self.infallible_destructuring_match_linted = false; } else { check_match_single_binding(cx, ex, arms, expr); } } if let ExprKind::Match(ref ex, ref arms, _) = expr.kind { check_match_ref_pats(cx, ex, arms, expr); } } 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 arms.len() == 1 && arms[0].guard.is_none(); 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]); let body = remove_blocks(&arms[0].body); if match_var(body, arg); then { let mut applicability = Applicability::MachineApplicable; self.infallible_destructuring_match_linted = true; span_lint_and_sugg( cx, INFALLIBLE_DESTRUCTURING_MATCH, local.span, "you seem to be trying to use `match` to destructure a single infallible pattern. \ Consider using `let`", "try this", format!( "let {}({}) = {};", snippet_with_applicability(cx, variant_name.span, "..", &mut applicability), snippet_with_applicability(cx, local.pat.span, "..", &mut applicability), snippet_with_applicability(cx, target.span, "..", &mut applicability), ), applicability, ); } } } 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 Some(def_id) = path.res.opt_def_id(); let ty = cx.tcx.type_of(def_id); if let ty::Adt(def, _) = ty.kind(); if def.is_struct() || def.is_union(); if fields.len() == def.non_enum_variant().fields.len(); then { span_lint_and_help( cx, REST_PAT_IN_FULLY_BOUND_STRUCTS, pat.span, "unnecessary use of `..` pattern in struct binding. All fields were already bound", None, "consider removing `..` from this binding", ); } } } } #[rustfmt::skip] 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 // macro_rules! block return; } if let PatKind::Or(..) = arms[0].pat.kind { // don't lint for or patterns for now, this makes // the lint noisy in unnecessary situations return; } let els = arms[1].body; let els = if is_unit_expr(remove_blocks(els)) { None } 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; } else { // block with 2+ statements or 1 expr and 1+ statement Some(els) } } else { // not a block, don't lint return; }; 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); } } } fn check_single_match_single_pattern( cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, els: Option<&Expr<'_>>, ) { if is_wild(&arms[1].pat) { report_single_match_single_pattern(cx, ex, arms, expr, els); } } fn report_single_match_single_pattern( cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, els: Option<&Expr<'_>>, ) { let lint = if els.is_some() { SINGLE_MATCH_ELSE } else { SINGLE_MATCH }; let els_str = els.map_or(String::new(), |els| { format!(" else {}", expr_block(cx, els, None, "..", Some(expr.span))) }); 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`", "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, ), Applicability::HasPlaceholders, ); } fn check_single_match_opt_like( cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>, ty: Ty<'_>, els: Option<&Expr<'_>>, ) { // list of candidate `Enum`s we know will never get any more members let candidates = &[ (&paths::COW, "Borrowed"), (&paths::COW, "Cow::Borrowed"), (&paths::COW, "Cow::Owned"), (&paths::COW, "Owned"), (&paths::OPTION, "None"), (&paths::RESULT, "Err"), (&paths::RESULT, "Ok"), ]; let path = match arms[1].pat.kind { PatKind::TupleStruct(ref path, ref inner, _) => { // Contains any non wildcard patterns (e.g., `Err(err)`)? if !inner.iter().all(is_wild) { return; } rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)) }, PatKind::Binding(BindingAnnotation::Unannotated, .., ident, None) => ident.to_string(), PatKind::Path(ref path) => { rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false)) }, _ => return, }; for &(ty_path, pat_path) in candidates { if path == *pat_path && match_type(cx, ty, ty_path) { report_single_match_single_pattern(cx, ex, arms, expr, els); } } } fn check_match_bool(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) { // Type of expression is `bool`. if *cx.typeck_results().expr_ty(ex).kind() == ty::Bool { span_lint_and_then( cx, MATCH_BOOL, expr.span, "you seem to be trying to match on a boolean expression", move |diag| { if arms.len() == 2 { // no guards let exprs = if let PatKind::Lit(ref 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)), LitKind::Bool(false) => Some((&*arms[1].body, &*arms[0].body)), _ => None, } } else { None } } else { None }; if let Some((true_expr, false_expr)) = exprs { let sugg = match (is_unit_expr(true_expr), is_unit_expr(false_expr)) { (false, false) => Some(format!( "if {} {} else {}", snippet(cx, ex.span, "b"), expr_block(cx, true_expr, None, "..", Some(expr.span)), expr_block(cx, false_expr, None, "..", Some(expr.span)) )), (false, true) => Some(format!( "if {} {}", snippet(cx, ex.span, "b"), expr_block(cx, true_expr, None, "..", Some(expr.span)) )), (true, false) => { let test = Sugg::hir(cx, ex, ".."); Some(format!( "if {} {}", !test, expr_block(cx, false_expr, None, "..", Some(expr.span)) )) }, (true, true) => None, }; if let Some(sugg) = sugg { diag.span_suggestion( expr.span, "consider using an `if`/`else` expression", sugg, Applicability::HasPlaceholders, ); } } } }, ); } } 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) { span_lint_and_note( cx, MATCH_OVERLAPPING_ARM, start.span, "some ranges overlap", Some(end.span), "overlaps with this", ); } } } } fn check_wild_err_arm(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) { 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)); 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) { 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 is_panic_block(block); then { // `Err(_)` or `Err(_e)` arm with `panic!` found span_lint_and_note(cx, MATCH_WILD_ERR_ARM, arm.pat.span, &format!("`Err({})` matches all errors", &ident_bind_name), None, "match each error separately or use the error output, or use `.except(msg)` if the error case is unreachable", ); } } } } } } } fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>]) { let ty = cx.typeck_results().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; } // 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; 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); } } 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. 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<'_>| matches!(pat.kind, PatKind::Wild | PatKind::Binding(.., None)); if patterns.iter().all(is_pattern_exhaustive) { missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id())); } } } } 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("_")); } } 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_span, message, "try this", suggestion[0].clone(), 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() }, (&None, 1, Some(stmt)) => { is_expn_of(stmt.span, "panic").is_some() && is_expn_of(stmt.span, "unreachable").is_none() }, _ => false, } } 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 } })); span_lint_and_then(cx, MATCH_REF_PATS, expr.span, title, |diag| { if !expr.span.from_expansion() { multispan_sugg(diag, msg, 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]) } else { None }; if let Some(rb) = arm_ref { let suggestion = if rb == BindingAnnotation::Ref { "as_ref" } else { "as_mut" }; 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(); let input_ty = substs.type_at(0); 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 input_ty != output_ty; then { ".map(|x| x as _)" } else { "" } }; let mut applicability = Applicability::MachineApplicable; span_lint_and_sugg( cx, MATCH_AS_REF, expr.span, &format!("use `{}()` instead", suggestion), "try this", format!( "{}.{}(){}", snippet_with_applicability(cx, ex.span, "_", &mut applicability), suggestion, 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 { // 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.", None, "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<'_>) { 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), _ => return, } } } /// 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) { if_chain! { if arms.len() == 2; if cx.typeck_results().expr_ty(expr).is_bool(); if is_wild(&arms[1].pat); if let Some(first) = find_bool_lit(&arms[0].body.kind, desugared); if let Some(second) = find_bool_lit(&arms[1].body.kind, desugared); if first != second; then { let mut applicability = Applicability::MachineApplicable; let pat_and_guard = if let Some(Guard::If(g)) = arms[0].guard { format!("{} if {}", snippet_with_applicability(cx, arms[0].pat.span, "..", &mut applicability), snippet_with_applicability(cx, g.span, "..", &mut applicability)) } else { format!("{}", snippet_with_applicability(cx, arms[0].pat.span, "..", &mut applicability)) }; 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 first { "" } else { "!" }, snippet_with_applicability(cx, ex.span, "..", &mut applicability), pat_and_guard, ), applicability, ) } } } /// 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, } } 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; } let matched_vars = ex.span; let bind_names = arms[0].pat.span; 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 { snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string() }; // Do we need to add ';' to suggestion ? match match_body.kind { ExprKind::Block(block, _) => { // macro + expr_ty(body) == () if block.span.from_expansion() && cx.typeck_results().expr_ty(&match_body).is_unit() { snippet_body.push(';'); } }, _ => { // expr_ty(body) == () if cx.typeck_results().expr_ty(&match_body).is_unit() { snippet_body.push(';'); } }, } let mut applicability = Applicability::MaybeIncorrect; match arms[0].pat.kind { PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => { // If this match is in a local (`let`) stmt let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) { ( parent_let_node.span, format!( "let {} = {};\n{}let {} = {};", snippet_with_applicability(cx, bind_names, "..", &mut applicability), snippet_with_applicability(cx, matched_vars, "..", &mut applicability), " ".repeat(indent_of(cx, expr.span).unwrap_or(0)), snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability), snippet_body ), ) } else { // If we are in closure, we need curly braces around suggestion let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0)); let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string()); if let Some(parent_expr) = get_parent_expr(cx, expr) { if let ExprKind::Closure(..) = parent_expr.kind { cbrace_end = format!("\n{}}}", indent); // Fix body indent due to the closure indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0)); cbrace_start = format!("{{\n{}", indent); } }; ( expr.span, format!( "{}let {} = {};\n{}{}{}", cbrace_start, snippet_with_applicability(cx, bind_names, "..", &mut applicability), snippet_with_applicability(cx, matched_vars, "..", &mut applicability), indent, snippet_body, cbrace_end ), ) }; span_lint_and_sugg( cx, MATCH_SINGLE_BINDING, target_span, "this match could be written as a `let` statement", "consider using `let` statement", sugg, applicability, ); }, 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, ); }, _ => (), } } /// 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>> { 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 { return Some(parent_let_expr); } } None } /// 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 { if let PatKind::Range(ref lhs, ref rhs, range_end) = pat.kind { let lhs = match lhs { 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.typeck_results(), rhs)?.0, None => miri_to_const(ty.numeric_max_val(cx.tcx)?)?, }; let rhs = match range_end { RangeEnd::Included => Bound::Included(rhs), RangeEnd::Excluded => Bound::Excluded(rhs), }; return Some(SpannedRange { span: pat.span, node: (lhs, rhs), }); } if let PatKind::Lit(ref value) = pat.kind { let value = constant(cx, cx.typeck_results(), value)?.0; return Some(SpannedRange { span: pat.span, node: (value.clone(), Bound::Included(value)), }); } } None }) .collect() } #[derive(Debug, Eq, PartialEq)] pub struct SpannedRange { pub span: Span, pub node: (T, Bound), } type TypedRanges = Vec>; /// Gets all `Int` ranges or all `Uint` ranges. Mixed types are an error anyway /// and other types than /// `Uint` and `Int` probably don't make sense. fn type_ranges(ranges: &[SpannedRange]) -> TypedRanges { ranges .iter() .filter_map(|range| match range.node { (Constant::Int(start), Bound::Included(Constant::Int(end))) => Some(SpannedRange { span: range.span, node: (start, Bound::Included(end)), }), (Constant::Int(start), Bound::Excluded(Constant::Int(end))) => Some(SpannedRange { span: range.span, node: (start, Bound::Excluded(end)), }), (Constant::Int(start), Bound::Unbounded) => Some(SpannedRange { span: range.span, node: (start, Bound::Unbounded), }), _ => None, }) .collect() } 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, _ => false, } } // Checks if arm has the form `None => None` fn is_none_arm(arm: &Arm<'_>) -> bool { 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`) fn is_ref_some_arm(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 rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut; 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 path2.segments.len() == 1 && ident.name == path2.segments[0].ident.name; then { return Some(rb) } } 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 } }) .collect::>>(); // look for Some(v) where there's at least one true element mapped.map_or(false, |v| v.iter().any(|el| *el)) } pub fn overlapping(ranges: &[SpannedRange]) -> Option<(&SpannedRange, &SpannedRange)> where T: Copy + Ord, { #[derive(Copy, Clone, Debug, Eq, PartialEq)] enum Kind<'a, T> { Start(T, &'a SpannedRange), End(Bound, &'a SpannedRange), } impl<'a, T: Copy> Kind<'a, T> { fn range(&self) -> &'a SpannedRange { match *self { Kind::Start(_, r) | Kind::End(_, r) => r, } } fn value(self) -> Bound { match self { Kind::Start(t, _) => Bound::Included(t), Kind::End(t, _) => t, } } } impl<'a, T: Copy + Ord> PartialOrd for Kind<'a, T> { fn partial_cmp(&self, other: &Self) -> Option { Some(self.cmp(other)) } } impl<'a, T: Copy + Ord> Ord for Kind<'a, T> { fn cmp(&self, other: &Self) -> Ordering { match (self.value(), other.value()) { (Bound::Included(a), Bound::Included(b)) | (Bound::Excluded(a), Bound::Excluded(b)) => a.cmp(&b), // Range patterns cannot be unbounded (yet) (Bound::Unbounded, _) | (_, Bound::Unbounded) => unimplemented!(), (Bound::Included(a), Bound::Excluded(b)) => match a.cmp(&b) { Ordering::Equal => Ordering::Greater, other => other, }, (Bound::Excluded(a), Bound::Included(b)) => match a.cmp(&b) { Ordering::Equal => Ordering::Less, other => other, }, } } } let mut values = Vec::with_capacity(2 * ranges.len()); for r in ranges { values.push(Kind::Start(r.node.0, r)); values.push(Kind::End(r.node.1, r)); } values.sort(); for (a, b) in values.iter().zip(values.iter().skip(1)) { match (a, b) { (&Kind::Start(_, ra), &Kind::End(_, rb)) => { if ra.node != rb.node { return Some((ra, rb)); } }, (&Kind::End(a, _), &Kind::Start(b, _)) if a != Bound::Included(b) => (), _ => return Some((a.range(), b.range())), } } None } mod redundant_pattern_match { use super::REDUNDANT_PATTERN_MATCHING; use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then}; 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; 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 { return; } } else { return; } }, PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()", _ => 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 match_trait_method(cx, op, &paths::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()", ) } 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()", ) } 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; let sp = |s, e| SpannedRange { span: DUMMY_SP, node: (s, e), }; assert_eq!(None, overlapping::(&[])); assert_eq!(None, overlapping(&[sp(1, Bound::Included(4))])); assert_eq!( None, overlapping(&[sp(1, Bound::Included(4)), sp(5, Bound::Included(6))]) ); assert_eq!( None, overlapping(&[ sp(1, Bound::Included(4)), sp(5, Bound::Included(6)), sp(10, Bound::Included(11)) ],) ); assert_eq!( Some((&sp(1, Bound::Included(4)), &sp(3, Bound::Included(6)))), overlapping(&[sp(1, Bound::Included(4)), sp(3, Bound::Included(6))]) ); assert_eq!( Some((&sp(5, Bound::Included(6)), &sp(6, Bound::Included(11)))), overlapping(&[ sp(1, Bound::Included(4)), sp(5, Bound::Included(6)), sp(6, Bound::Included(11)) ],) ); }