| 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 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, 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; |
| 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<i32, &str> = 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" |
| } |
| |
| #[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 |
| ]); |
| |
| 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) { |
| return; |
| } |
| 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 = remove_blocks(&arms[1].body); |
| let els = if is_unit_expr(els) { |
| None |
| } else if let ExprKind::Block(_, _) = els.kind { |
| // matches with blocks that contain statements are prettier as `if let + else` |
| Some(els) |
| } else { |
| // allow match arms with just expressions |
| return; |
| }; |
| let ty = cx.tables().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.tables().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.tables().expr_ty(ex).is_integral() { |
| let ranges = all_ranges(cx, arms, cx.tables().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 = walk_ptrs_ty(cx.tables().expr_ty(ex)); |
| 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.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; |
| } |
| |
| // 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<'_>| { |
| if let PatKind::Wild | PatKind::Binding(.., None) = pat.kind { |
| true |
| } else { |
| false |
| } |
| }; |
| if patterns.iter().all(is_pattern_exhaustive) { |
| missing_variants.retain(|e| e.ctor_def_id != Some(p.res.def_id())); |
| } |
| } |
| } |
| } |
| |
| let mut suggestion: Vec<String> = 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<BindingAnnotation> = 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.tables().expr_ty(expr); |
| let input_ty = cx.tables().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.", |
| ); |
| } |
| } |
| } |
| } |
| |
| 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.tables().expr_ty(&match_body).is_unit() { |
| snippet_body.push(';'); |
| } |
| }, |
| _ => { |
| // expr_ty(body) == () |
| if cx.tables().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<SpannedRange<Constant>> { |
| 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.tables(), lhs)?.0, |
| None => miri_to_const(ty.numeric_min_val(cx.tcx)?)?, |
| }; |
| let rhs = match rhs { |
| Some(rhs) => constant(cx, cx.tables(), 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.tables(), value)?.0; |
| return Some(SpannedRange { |
| span: pat.span, |
| node: (value.clone(), Bound::Included(value)), |
| }); |
| } |
| } |
| None |
| }) |
| .collect() |
| } |
| |
| #[derive(Debug, Eq, PartialEq)] |
| pub struct SpannedRange<T> { |
| pub span: Span, |
| pub node: (T, Bound<T>), |
| } |
| |
| type TypedRanges = Vec<SpannedRange<u128>>; |
| |
| /// 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<Constant>]) -> 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 { |
| match arm.pat.kind { |
| PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => true, |
| _ => false, |
| } |
| } |
| |
| // 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<BindingAnnotation> { |
| 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::<Option<Vec<bool>>>(); |
| // 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<T>(ranges: &[SpannedRange<T>]) -> Option<(&SpannedRange<T>, &SpannedRange<T>)> |
| where |
| T: Copy + Ord, |
| { |
| #[derive(Copy, Clone, Debug, Eq, PartialEq)] |
| enum Kind<'a, T> { |
| Start(T, &'a SpannedRange<T>), |
| End(Bound<T>, &'a SpannedRange<T>), |
| } |
| |
| impl<'a, T: Copy> Kind<'a, T> { |
| fn range(&self) -> &'a SpannedRange<T> { |
| match *self { |
| Kind::Start(_, r) | Kind::End(_, r) => r, |
| } |
| } |
| |
| fn value(self) -> Bound<T> { |
| 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<Ordering> { |
| 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 |
| } |
| |
| #[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::<u8>(&[])); |
| 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)) |
| ],) |
| ); |
| } |
