| use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then}; |
| use clippy_utils::source::{snippet_with_applicability, snippet_with_context}; |
| use clippy_utils::sugg::has_enclosing_paren; |
| use clippy_utils::ty::{implements_trait, peel_mid_ty_refs}; |
| use clippy_utils::{ |
| expr_use_ctxt, get_parent_expr, get_parent_node, is_lint_allowed, path_to_local, DefinedTy, ExprUseNode, |
| }; |
| use rustc_ast::util::parser::{PREC_POSTFIX, PREC_PREFIX}; |
| use rustc_data_structures::fx::FxIndexMap; |
| use rustc_errors::Applicability; |
| use rustc_hir::intravisit::{walk_ty, Visitor}; |
| use rustc_hir::{ |
| self as hir, BindingAnnotation, Body, BodyId, BorrowKind, Expr, ExprKind, HirId, MatchSource, Mutability, Node, |
| Pat, PatKind, Path, QPath, TyKind, UnOp, |
| }; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability}; |
| use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, TypeVisitableExt, TypeckResults}; |
| use rustc_session::{declare_tool_lint, impl_lint_pass}; |
| use rustc_span::symbol::sym; |
| use rustc_span::{Span, Symbol}; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for explicit `deref()` or `deref_mut()` method calls. |
| /// |
| /// ### Why is this bad? |
| /// Dereferencing by `&*x` or `&mut *x` is clearer and more concise, |
| /// when not part of a method chain. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// use std::ops::Deref; |
| /// let a: &mut String = &mut String::from("foo"); |
| /// let b: &str = a.deref(); |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```no_run |
| /// let a: &mut String = &mut String::from("foo"); |
| /// let b = &*a; |
| /// ``` |
| /// |
| /// This lint excludes all of: |
| /// ```rust,ignore |
| /// let _ = d.unwrap().deref(); |
| /// let _ = Foo::deref(&foo); |
| /// let _ = <Foo as Deref>::deref(&foo); |
| /// ``` |
| #[clippy::version = "1.44.0"] |
| pub EXPLICIT_DEREF_METHODS, |
| pedantic, |
| "Explicit use of deref or deref_mut method while not in a method chain." |
| } |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for address of operations (`&`) that are going to |
| /// be dereferenced immediately by the compiler. |
| /// |
| /// ### Why is this bad? |
| /// Suggests that the receiver of the expression borrows |
| /// the expression. |
| /// |
| /// ### Known problems |
| /// The lint cannot tell when the implementation of a trait |
| /// for `&T` and `T` do different things. Removing a borrow |
| /// in such a case can change the semantics of the code. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// fn fun(_a: &i32) {} |
| /// |
| /// let x: &i32 = &&&&&&5; |
| /// fun(&x); |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```no_run |
| /// # fn fun(_a: &i32) {} |
| /// let x: &i32 = &5; |
| /// fun(x); |
| /// ``` |
| #[clippy::version = "pre 1.29.0"] |
| pub NEEDLESS_BORROW, |
| style, |
| "taking a reference that is going to be automatically dereferenced" |
| } |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for `ref` bindings which create a reference to a reference. |
| /// |
| /// ### Why is this bad? |
| /// The address-of operator at the use site is clearer about the need for a reference. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// let x = Some(""); |
| /// if let Some(ref x) = x { |
| /// // use `x` here |
| /// } |
| /// ``` |
| /// |
| /// Use instead: |
| /// ```no_run |
| /// let x = Some(""); |
| /// if let Some(x) = x { |
| /// // use `&x` here |
| /// } |
| /// ``` |
| #[clippy::version = "1.54.0"] |
| pub REF_BINDING_TO_REFERENCE, |
| pedantic, |
| "`ref` binding to a reference" |
| } |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for dereferencing expressions which would be covered by auto-deref. |
| /// |
| /// ### Why is this bad? |
| /// This unnecessarily complicates the code. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// let x = String::new(); |
| /// let y: &str = &*x; |
| /// ``` |
| /// Use instead: |
| /// ```no_run |
| /// let x = String::new(); |
| /// let y: &str = &x; |
| /// ``` |
| #[clippy::version = "1.64.0"] |
| pub EXPLICIT_AUTO_DEREF, |
| complexity, |
| "dereferencing when the compiler would automatically dereference" |
| } |
| |
| impl_lint_pass!(Dereferencing<'_> => [ |
| EXPLICIT_DEREF_METHODS, |
| NEEDLESS_BORROW, |
| REF_BINDING_TO_REFERENCE, |
| EXPLICIT_AUTO_DEREF, |
| ]); |
| |
| #[derive(Default)] |
| pub struct Dereferencing<'tcx> { |
| state: Option<(State, StateData<'tcx>)>, |
| |
| // While parsing a `deref` method call in ufcs form, the path to the function is itself an |
| // expression. This is to store the id of that expression so it can be skipped when |
| // `check_expr` is called for it. |
| skip_expr: Option<HirId>, |
| |
| /// The body the first local was found in. Used to emit lints when the traversal of the body has |
| /// been finished. Note we can't lint at the end of every body as they can be nested within each |
| /// other. |
| current_body: Option<BodyId>, |
| |
| /// The list of locals currently being checked by the lint. |
| /// If the value is `None`, then the binding has been seen as a ref pattern, but is not linted. |
| /// This is needed for or patterns where one of the branches can be linted, but another can not |
| /// be. |
| /// |
| /// e.g. `m!(x) | Foo::Bar(ref x)` |
| ref_locals: FxIndexMap<HirId, Option<RefPat>>, |
| } |
| |
| #[derive(Debug)] |
| struct StateData<'tcx> { |
| /// Span of the top level expression |
| span: Span, |
| hir_id: HirId, |
| adjusted_ty: Ty<'tcx>, |
| } |
| |
| struct DerefedBorrow { |
| count: usize, |
| msg: &'static str, |
| stability: TyCoercionStability, |
| for_field_access: Option<Symbol>, |
| } |
| |
| enum State { |
| // Any number of deref method calls. |
| DerefMethod { |
| // The number of calls in a sequence which changed the referenced type |
| ty_changed_count: usize, |
| is_ufcs: bool, |
| /// The required mutability |
| mutbl: Mutability, |
| }, |
| DerefedBorrow(DerefedBorrow), |
| ExplicitDeref { |
| mutability: Option<Mutability>, |
| }, |
| ExplicitDerefField { |
| name: Symbol, |
| }, |
| Reborrow { |
| mutability: Mutability, |
| }, |
| Borrow { |
| mutability: Mutability, |
| }, |
| } |
| |
| // A reference operation considered by this lint pass |
| enum RefOp { |
| Method { mutbl: Mutability, is_ufcs: bool }, |
| Deref, |
| AddrOf(Mutability), |
| } |
| |
| struct RefPat { |
| /// Whether every usage of the binding is dereferenced. |
| always_deref: bool, |
| /// The spans of all the ref bindings for this local. |
| spans: Vec<Span>, |
| /// The applicability of this suggestion. |
| app: Applicability, |
| /// All the replacements which need to be made. |
| replacements: Vec<(Span, String)>, |
| /// The [`HirId`] that the lint should be emitted at. |
| hir_id: HirId, |
| } |
| |
| impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> { |
| #[expect(clippy::too_many_lines)] |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| // Skip path expressions from deref calls. e.g. `Deref::deref(e)` |
| if Some(expr.hir_id) == self.skip_expr.take() { |
| return; |
| } |
| |
| if let Some(local) = path_to_local(expr) { |
| self.check_local_usage(cx, expr, local); |
| } |
| |
| // Stop processing sub expressions when a macro call is seen |
| if expr.span.from_expansion() { |
| if let Some((state, data)) = self.state.take() { |
| report(cx, expr, state, data); |
| } |
| return; |
| } |
| |
| let typeck = cx.typeck_results(); |
| let Some((kind, sub_expr)) = try_parse_ref_op(cx.tcx, typeck, expr) else { |
| // The whole chain of reference operations has been seen |
| if let Some((state, data)) = self.state.take() { |
| report(cx, expr, state, data); |
| } |
| return; |
| }; |
| |
| match (self.state.take(), kind) { |
| (None, kind) => { |
| let expr_ty = typeck.expr_ty(expr); |
| let use_cx = expr_use_ctxt(cx, expr); |
| let adjusted_ty = match &use_cx { |
| Some(use_cx) => match use_cx.adjustments { |
| [.., a] => a.target, |
| _ => expr_ty, |
| }, |
| _ => typeck.expr_ty_adjusted(expr), |
| }; |
| |
| match (use_cx, kind) { |
| (Some(use_cx), RefOp::Deref) => { |
| let sub_ty = typeck.expr_ty(sub_expr); |
| if let ExprUseNode::FieldAccess(name) = use_cx.node |
| && adjusted_ty.ty_adt_def().map_or(true, |adt| !adt.is_union()) |
| && !ty_contains_field(sub_ty, name.name) |
| { |
| self.state = Some(( |
| State::ExplicitDerefField { name: name.name }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| } else if sub_ty.is_ref() |
| // Linting method receivers would require verifying that name lookup |
| // would resolve the same way. This is complicated by trait methods. |
| && !use_cx.node.is_recv() |
| && let Some(ty) = use_cx.node.defined_ty(cx) |
| && TyCoercionStability::for_defined_ty(cx, ty, use_cx.node.is_return()).is_deref_stable() |
| { |
| self.state = Some(( |
| State::ExplicitDeref { mutability: None }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| } |
| }, |
| (_, RefOp::Method { mutbl, is_ufcs }) |
| if !is_lint_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id) |
| // Allow explicit deref in method chains. e.g. `foo.deref().bar()` |
| && (is_ufcs || !in_postfix_position(cx, expr)) => |
| { |
| let ty_changed_count = usize::from(!deref_method_same_type(expr_ty, typeck.expr_ty(sub_expr))); |
| self.state = Some(( |
| State::DerefMethod { |
| ty_changed_count, |
| is_ufcs, |
| mutbl, |
| }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| }, |
| (Some(use_cx), RefOp::AddrOf(mutability)) => { |
| // Find the number of times the borrow is auto-derefed. |
| let mut iter = use_cx.adjustments.iter(); |
| let mut deref_count = 0usize; |
| let next_adjust = loop { |
| match iter.next() { |
| Some(adjust) => { |
| if !matches!(adjust.kind, Adjust::Deref(_)) { |
| break Some(adjust); |
| } else if !adjust.target.is_ref() { |
| deref_count += 1; |
| break iter.next(); |
| } |
| deref_count += 1; |
| }, |
| None => break None, |
| }; |
| }; |
| |
| let stability = use_cx.node.defined_ty(cx).map_or(TyCoercionStability::None, |ty| { |
| TyCoercionStability::for_defined_ty(cx, ty, use_cx.node.is_return()) |
| }); |
| let can_auto_borrow = match use_cx.node { |
| ExprUseNode::Callee => true, |
| ExprUseNode::FieldAccess(_) => adjusted_ty.ty_adt_def().map_or(true, |adt| !adt.is_union()), |
| ExprUseNode::MethodArg(hir_id, _, 0) if !use_cx.moved_before_use => { |
| // Check for calls to trait methods where the trait is implemented |
| // on a reference. |
| // Two cases need to be handled: |
| // * `self` methods on `&T` will never have auto-borrow |
| // * `&self` methods on `&T` can have auto-borrow, but `&self` methods on `T` will take |
| // priority. |
| if let Some(fn_id) = typeck.type_dependent_def_id(hir_id) |
| && let Some(trait_id) = cx.tcx.trait_of_item(fn_id) |
| && let arg_ty = cx |
| .tcx |
| .erase_regions(use_cx.adjustments.last().map_or(expr_ty, |a| a.target)) |
| && let ty::Ref(_, sub_ty, _) = *arg_ty.kind() |
| && let args = cx |
| .typeck_results() |
| .node_args_opt(hir_id) |
| .map(|args| &args[1..]) |
| .unwrap_or_default() |
| && let impl_ty = |
| if cx.tcx.fn_sig(fn_id).instantiate_identity().skip_binder().inputs()[0] |
| .is_ref() |
| { |
| // Trait methods taking `&self` |
| sub_ty |
| } else { |
| // Trait methods taking `self` |
| arg_ty |
| } |
| && impl_ty.is_ref() |
| && implements_trait( |
| cx, |
| impl_ty, |
| trait_id, |
| &args[..cx.tcx.generics_of(trait_id).params.len() - 1], |
| ) |
| { |
| false |
| } else { |
| true |
| } |
| }, |
| _ => false, |
| }; |
| |
| let deref_msg = |
| "this expression creates a reference which is immediately dereferenced by the compiler"; |
| let borrow_msg = "this expression borrows a value the compiler would automatically borrow"; |
| |
| // Determine the required number of references before any can be removed. In all cases the |
| // reference made by the current expression will be removed. After that there are four cases to |
| // handle. |
| // |
| // 1. Auto-borrow will trigger in the current position, so no further references are required. |
| // 2. Auto-deref ends at a reference, or the underlying type, so one extra needs to be left to |
| // handle the automatically inserted re-borrow. |
| // 3. Auto-deref hits a user-defined `Deref` impl, so at least one reference needs to exist to |
| // start auto-deref. |
| // 4. If the chain of non-user-defined derefs ends with a mutable re-borrow, and re-borrow |
| // adjustments will not be inserted automatically, then leave one further reference to avoid |
| // moving a mutable borrow. e.g. |
| // |
| // ```rust |
| // fn foo<T>(x: &mut Option<&mut T>, y: &mut T) { |
| // let x = match x { |
| // // Removing the borrow will cause `x` to be moved |
| // Some(x) => &mut *x, |
| // None => y |
| // }; |
| // } |
| // ``` |
| let (required_refs, msg) = if can_auto_borrow { |
| (1, if deref_count == 1 { borrow_msg } else { deref_msg }) |
| } else if let Some(&Adjustment { |
| kind: Adjust::Borrow(AutoBorrow::Ref(_, mutability)), |
| .. |
| }) = next_adjust |
| && matches!(mutability, AutoBorrowMutability::Mut { .. }) |
| && !stability.is_reborrow_stable() |
| { |
| (3, deref_msg) |
| } else { |
| (2, deref_msg) |
| }; |
| |
| if deref_count >= required_refs { |
| self.state = Some(( |
| State::DerefedBorrow(DerefedBorrow { |
| // One of the required refs is for the current borrow expression, the remaining ones |
| // can't be removed without breaking the code. See earlier comment. |
| count: deref_count - required_refs, |
| msg, |
| stability, |
| for_field_access: match use_cx.node { |
| ExprUseNode::FieldAccess(name) => Some(name.name), |
| _ => None, |
| }, |
| }), |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty: use_cx.adjustments.last().map_or(expr_ty, |a| a.target), |
| }, |
| )); |
| } else if stability.is_deref_stable() |
| // Auto-deref doesn't combine with other adjustments |
| && next_adjust.map_or(true, |a| matches!(a.kind, Adjust::Deref(_) | Adjust::Borrow(_))) |
| && iter.all(|a| matches!(a.kind, Adjust::Deref(_) | Adjust::Borrow(_))) |
| { |
| self.state = Some(( |
| State::Borrow { mutability }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty: use_cx.adjustments.last().map_or(expr_ty, |a| a.target), |
| }, |
| )); |
| } |
| }, |
| (None, _) | (_, RefOp::Method { .. }) => (), |
| } |
| }, |
| ( |
| Some(( |
| State::DerefMethod { |
| mutbl, |
| ty_changed_count, |
| .. |
| }, |
| data, |
| )), |
| RefOp::Method { is_ufcs, .. }, |
| ) => { |
| self.state = Some(( |
| State::DerefMethod { |
| ty_changed_count: if deref_method_same_type(typeck.expr_ty(expr), typeck.expr_ty(sub_expr)) { |
| ty_changed_count |
| } else { |
| ty_changed_count + 1 |
| }, |
| is_ufcs, |
| mutbl, |
| }, |
| data, |
| )); |
| }, |
| (Some((State::DerefedBorrow(state), data)), RefOp::AddrOf(_)) if state.count != 0 => { |
| self.state = Some(( |
| State::DerefedBorrow(DerefedBorrow { |
| count: state.count - 1, |
| ..state |
| }), |
| data, |
| )); |
| }, |
| (Some((State::DerefedBorrow(state), data)), RefOp::AddrOf(mutability)) => { |
| let adjusted_ty = data.adjusted_ty; |
| let stability = state.stability; |
| report(cx, expr, State::DerefedBorrow(state), data); |
| if stability.is_deref_stable() { |
| self.state = Some(( |
| State::Borrow { mutability }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| } |
| }, |
| (Some((State::DerefedBorrow(state), data)), RefOp::Deref) => { |
| let adjusted_ty = data.adjusted_ty; |
| let stability = state.stability; |
| let for_field_access = state.for_field_access; |
| report(cx, expr, State::DerefedBorrow(state), data); |
| if let Some(name) = for_field_access |
| && !ty_contains_field(typeck.expr_ty(sub_expr), name) |
| { |
| self.state = Some(( |
| State::ExplicitDerefField { name }, |
| StateData { |
| span: expr.span, |
| hir_id: expr.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| } else if stability.is_deref_stable() |
| && let Some(parent) = get_parent_expr(cx, expr) |
| { |
| self.state = Some(( |
| State::ExplicitDeref { mutability: None }, |
| StateData { |
| span: parent.span, |
| hir_id: parent.hir_id, |
| adjusted_ty, |
| }, |
| )); |
| } |
| }, |
| |
| (Some((State::Borrow { mutability }, data)), RefOp::Deref) => { |
| if typeck.expr_ty(sub_expr).is_ref() { |
| self.state = Some((State::Reborrow { mutability }, data)); |
| } else { |
| self.state = Some(( |
| State::ExplicitDeref { |
| mutability: Some(mutability), |
| }, |
| data, |
| )); |
| } |
| }, |
| (Some((State::Reborrow { mutability }, data)), RefOp::Deref) => { |
| self.state = Some(( |
| State::ExplicitDeref { |
| mutability: Some(mutability), |
| }, |
| data, |
| )); |
| }, |
| (state @ Some((State::ExplicitDeref { .. }, _)), RefOp::Deref) => { |
| self.state = state; |
| }, |
| (Some((State::ExplicitDerefField { name }, data)), RefOp::Deref) |
| if !ty_contains_field(typeck.expr_ty(sub_expr), name) => |
| { |
| self.state = Some((State::ExplicitDerefField { name }, data)); |
| }, |
| |
| (Some((state, data)), _) => report(cx, expr, state, data), |
| } |
| } |
| |
| fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) { |
| if let PatKind::Binding(BindingAnnotation::REF, id, name, _) = pat.kind { |
| if let Some(opt_prev_pat) = self.ref_locals.get_mut(&id) { |
| // This binding id has been seen before. Add this pattern to the list of changes. |
| if let Some(prev_pat) = opt_prev_pat { |
| if pat.span.from_expansion() { |
| // Doesn't match the context of the previous pattern. Can't lint here. |
| *opt_prev_pat = None; |
| } else { |
| prev_pat.spans.push(pat.span); |
| prev_pat.replacements.push(( |
| pat.span, |
| snippet_with_context(cx, name.span, pat.span.ctxt(), "..", &mut prev_pat.app) |
| .0 |
| .into(), |
| )); |
| } |
| } |
| return; |
| } |
| |
| if_chain! { |
| if !pat.span.from_expansion(); |
| if let ty::Ref(_, tam, _) = *cx.typeck_results().pat_ty(pat).kind(); |
| // only lint immutable refs, because borrowed `&mut T` cannot be moved out |
| if let ty::Ref(_, _, Mutability::Not) = *tam.kind(); |
| then { |
| let mut app = Applicability::MachineApplicable; |
| let snip = snippet_with_context(cx, name.span, pat.span.ctxt(), "..", &mut app).0; |
| self.current_body = self.current_body.or(cx.enclosing_body); |
| self.ref_locals.insert( |
| id, |
| Some(RefPat { |
| always_deref: true, |
| spans: vec![pat.span], |
| app, |
| replacements: vec![(pat.span, snip.into())], |
| hir_id: pat.hir_id, |
| }), |
| ); |
| } |
| } |
| } |
| } |
| |
| fn check_body_post(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) { |
| if Some(body.id()) == self.current_body { |
| for pat in self.ref_locals.drain(..).filter_map(|(_, x)| x) { |
| let replacements = pat.replacements; |
| let app = pat.app; |
| let lint = if pat.always_deref { |
| NEEDLESS_BORROW |
| } else { |
| REF_BINDING_TO_REFERENCE |
| }; |
| span_lint_hir_and_then( |
| cx, |
| lint, |
| pat.hir_id, |
| pat.spans, |
| "this pattern creates a reference to a reference", |
| |diag| { |
| diag.multipart_suggestion("try", replacements, app); |
| }, |
| ); |
| } |
| self.current_body = None; |
| } |
| } |
| } |
| |
| fn try_parse_ref_op<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| typeck: &'tcx TypeckResults<'_>, |
| expr: &'tcx Expr<'_>, |
| ) -> Option<(RefOp, &'tcx Expr<'tcx>)> { |
| let (is_ufcs, def_id, arg) = match expr.kind { |
| ExprKind::MethodCall(_, arg, [], _) => (false, typeck.type_dependent_def_id(expr.hir_id)?, arg), |
| ExprKind::Call( |
| Expr { |
| kind: ExprKind::Path(path), |
| hir_id, |
| .. |
| }, |
| [arg], |
| ) => (true, typeck.qpath_res(path, *hir_id).opt_def_id()?, arg), |
| ExprKind::Unary(UnOp::Deref, sub_expr) if !typeck.expr_ty(sub_expr).is_unsafe_ptr() => { |
| return Some((RefOp::Deref, sub_expr)); |
| }, |
| ExprKind::AddrOf(BorrowKind::Ref, mutability, sub_expr) => return Some((RefOp::AddrOf(mutability), sub_expr)), |
| _ => return None, |
| }; |
| if tcx.is_diagnostic_item(sym::deref_method, def_id) { |
| Some(( |
| RefOp::Method { |
| mutbl: Mutability::Not, |
| is_ufcs, |
| }, |
| arg, |
| )) |
| } else if tcx.trait_of_item(def_id)? == tcx.lang_items().deref_mut_trait()? { |
| Some(( |
| RefOp::Method { |
| mutbl: Mutability::Mut, |
| is_ufcs, |
| }, |
| arg, |
| )) |
| } else { |
| None |
| } |
| } |
| |
| // Checks whether the type for a deref call actually changed the type, not just the mutability of |
| // the reference. |
| fn deref_method_same_type<'tcx>(result_ty: Ty<'tcx>, arg_ty: Ty<'tcx>) -> bool { |
| match (result_ty.kind(), arg_ty.kind()) { |
| (ty::Ref(_, result_ty, _), ty::Ref(_, arg_ty, _)) => result_ty == arg_ty, |
| |
| // The result type for a deref method is always a reference |
| // Not matching the previous pattern means the argument type is not a reference |
| // This means that the type did change |
| _ => false, |
| } |
| } |
| |
| fn in_postfix_position<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> bool { |
| if let Some(parent) = get_parent_expr(cx, e) |
| && parent.span.eq_ctxt(e.span) |
| { |
| match parent.kind { |
| ExprKind::Call(child, _) | ExprKind::MethodCall(_, child, _, _) | ExprKind::Index(child, _, _) |
| if child.hir_id == e.hir_id => |
| { |
| true |
| }, |
| ExprKind::Match(.., MatchSource::TryDesugar(_) | MatchSource::AwaitDesugar) | ExprKind::Field(_, _) => true, |
| _ => false, |
| } |
| } else { |
| false |
| } |
| } |
| |
| #[derive(Clone, Copy)] |
| enum TyCoercionStability { |
| Deref, |
| Reborrow, |
| None, |
| } |
| impl TyCoercionStability { |
| fn is_deref_stable(self) -> bool { |
| matches!(self, Self::Deref) |
| } |
| |
| fn is_reborrow_stable(self) -> bool { |
| matches!(self, Self::Deref | Self::Reborrow) |
| } |
| |
| fn for_defined_ty<'tcx>(cx: &LateContext<'tcx>, ty: DefinedTy<'tcx>, for_return: bool) -> Self { |
| match ty { |
| DefinedTy::Hir(ty) => Self::for_hir_ty(ty), |
| DefinedTy::Mir(ty) => Self::for_mir_ty( |
| cx.tcx, |
| ty.param_env, |
| cx.tcx.erase_late_bound_regions(ty.value), |
| for_return, |
| ), |
| } |
| } |
| |
| // Checks the stability of type coercions when assigned to a binding with the given explicit type. |
| // |
| // e.g. |
| // let x = Box::new(Box::new(0u32)); |
| // let y1: &Box<_> = x.deref(); |
| // let y2: &Box<_> = &x; |
| // |
| // Here `y1` and `y2` would resolve to different types, so the type `&Box<_>` is not stable when |
| // switching to auto-dereferencing. |
| fn for_hir_ty<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> Self { |
| let TyKind::Ref(_, ty) = &ty.kind else { |
| return Self::None; |
| }; |
| let mut ty = ty; |
| |
| loop { |
| break match ty.ty.kind { |
| TyKind::Ref(_, ref ref_ty) => { |
| ty = ref_ty; |
| continue; |
| }, |
| TyKind::Path( |
| QPath::TypeRelative(_, path) |
| | QPath::Resolved( |
| _, |
| Path { |
| segments: [.., path], .. |
| }, |
| ), |
| ) => { |
| if let Some(args) = path.args |
| && args.args.iter().any(|arg| match arg { |
| hir::GenericArg::Infer(_) => true, |
| hir::GenericArg::Type(ty) => ty_contains_infer(ty), |
| _ => false, |
| }) |
| { |
| Self::Reborrow |
| } else { |
| Self::Deref |
| } |
| }, |
| TyKind::Slice(_) |
| | TyKind::Array(..) |
| | TyKind::Ptr(_) |
| | TyKind::BareFn(_) |
| | TyKind::Never |
| | TyKind::Tup(_) |
| | TyKind::Path(_) => Self::Deref, |
| TyKind::OpaqueDef(..) |
| | TyKind::Infer |
| | TyKind::Typeof(..) |
| | TyKind::TraitObject(..) |
| | TyKind::Err(_) => Self::Reborrow, |
| }; |
| } |
| } |
| |
| fn for_mir_ty<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>, for_return: bool) -> Self { |
| let ty::Ref(_, mut ty, _) = *ty.kind() else { |
| return Self::None; |
| }; |
| |
| ty = tcx.try_normalize_erasing_regions(param_env, ty).unwrap_or(ty); |
| loop { |
| break match *ty.kind() { |
| ty::Ref(_, ref_ty, _) => { |
| ty = ref_ty; |
| continue; |
| }, |
| ty::Param(_) if for_return => Self::Deref, |
| ty::Alias(ty::Weak | ty::Inherent, _) => unreachable!("should have been normalized away above"), |
| ty::Alias(ty::Projection, _) if !for_return && ty.has_non_region_param() => Self::Reborrow, |
| ty::Infer(_) |
| | ty::Error(_) |
| | ty::Bound(..) |
| | ty::Alias(ty::Opaque, ..) |
| | ty::Placeholder(_) |
| | ty::Dynamic(..) |
| | ty::Param(_) => Self::Reborrow, |
| ty::Adt(_, args) |
| if ty.has_placeholders() |
| || ty.has_opaque_types() |
| || (!for_return && args.has_non_region_param()) => |
| { |
| Self::Reborrow |
| }, |
| ty::Bool |
| | ty::Char |
| | ty::Int(_) |
| | ty::Uint(_) |
| | ty::Array(..) |
| | ty::Float(_) |
| | ty::RawPtr(..) |
| | ty::FnPtr(_) |
| | ty::Str |
| | ty::Slice(..) |
| | ty::Adt(..) |
| | ty::Foreign(_) |
| | ty::FnDef(..) |
| | ty::Coroutine(..) |
| | ty::CoroutineWitness(..) |
| | ty::Closure(..) |
| | ty::Never |
| | ty::Tuple(_) |
| | ty::Alias(ty::Projection, _) => Self::Deref, |
| }; |
| } |
| } |
| } |
| |
| // Checks whether a type is inferred at some point. |
| // e.g. `_`, `Box<_>`, `[_]` |
| fn ty_contains_infer(ty: &hir::Ty<'_>) -> bool { |
| struct V(bool); |
| impl Visitor<'_> for V { |
| fn visit_ty(&mut self, ty: &hir::Ty<'_>) { |
| if self.0 |
| || matches!( |
| ty.kind, |
| TyKind::OpaqueDef(..) | TyKind::Infer | TyKind::Typeof(_) | TyKind::Err(_) |
| ) |
| { |
| self.0 = true; |
| } else { |
| walk_ty(self, ty); |
| } |
| } |
| |
| fn visit_generic_arg(&mut self, arg: &hir::GenericArg<'_>) { |
| if self.0 || matches!(arg, hir::GenericArg::Infer(_)) { |
| self.0 = true; |
| } else if let hir::GenericArg::Type(ty) = arg { |
| self.visit_ty(ty); |
| } |
| } |
| } |
| let mut v = V(false); |
| v.visit_ty(ty); |
| v.0 |
| } |
| |
| fn ty_contains_field(ty: Ty<'_>, name: Symbol) -> bool { |
| if let ty::Adt(adt, _) = *ty.kind() { |
| adt.is_struct() && adt.all_fields().any(|f| f.name == name) |
| } else { |
| false |
| } |
| } |
| |
| #[expect(clippy::needless_pass_by_value, clippy::too_many_lines)] |
| fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data: StateData<'tcx>) { |
| match state { |
| State::DerefMethod { |
| ty_changed_count, |
| is_ufcs, |
| mutbl, |
| } => { |
| let mut app = Applicability::MachineApplicable; |
| let (expr_str, _expr_is_macro_call) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app); |
| let ty = cx.typeck_results().expr_ty(expr); |
| let (_, ref_count) = peel_mid_ty_refs(ty); |
| let deref_str = if ty_changed_count >= ref_count && ref_count != 0 { |
| // a deref call changing &T -> &U requires two deref operators the first time |
| // this occurs. One to remove the reference, a second to call the deref impl. |
| "*".repeat(ty_changed_count + 1) |
| } else { |
| "*".repeat(ty_changed_count) |
| }; |
| let addr_of_str = if ty_changed_count < ref_count { |
| // Check if a reborrow from &mut T -> &T is required. |
| if mutbl == Mutability::Not && matches!(ty.kind(), ty::Ref(_, _, Mutability::Mut)) { |
| "&*" |
| } else { |
| "" |
| } |
| } else if mutbl == Mutability::Mut { |
| "&mut " |
| } else { |
| "&" |
| }; |
| |
| // expr_str (the suggestion) is never shown if is_final_ufcs is true, since it's |
| // `expr.kind == ExprKind::Call`. Therefore, this is, afaik, always unnecessary. |
| /* |
| expr_str = if !expr_is_macro_call && is_final_ufcs && expr.precedence().order() < PREC_PREFIX { |
| Cow::Owned(format!("({expr_str})")) |
| } else { |
| expr_str |
| }; |
| */ |
| |
| // Fix #10850, do not lint if it's `Foo::deref` instead of `foo.deref()`. |
| if is_ufcs { |
| return; |
| } |
| |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_DEREF_METHODS, |
| data.span, |
| match mutbl { |
| Mutability::Not => "explicit `deref` method call", |
| Mutability::Mut => "explicit `deref_mut` method call", |
| }, |
| "try", |
| format!("{addr_of_str}{deref_str}{expr_str}"), |
| app, |
| ); |
| }, |
| State::DerefedBorrow(state) => { |
| let mut app = Applicability::MachineApplicable; |
| let (snip, snip_is_macro) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app); |
| span_lint_hir_and_then(cx, NEEDLESS_BORROW, data.hir_id, data.span, state.msg, |diag| { |
| let (precedence, calls_field) = match get_parent_node(cx.tcx, data.hir_id) { |
| Some(Node::Expr(e)) => match e.kind { |
| ExprKind::Call(callee, _) if callee.hir_id != data.hir_id => (0, false), |
| ExprKind::Call(..) => (PREC_POSTFIX, matches!(expr.kind, ExprKind::Field(..))), |
| _ => (e.precedence().order(), false), |
| }, |
| _ => (0, false), |
| }; |
| let sugg = if !snip_is_macro |
| && (calls_field || expr.precedence().order() < precedence) |
| && !has_enclosing_paren(&snip) |
| { |
| format!("({snip})") |
| } else { |
| snip.into() |
| }; |
| diag.span_suggestion(data.span, "change this to", sugg, app); |
| }); |
| }, |
| State::ExplicitDeref { mutability } => { |
| if matches!( |
| expr.kind, |
| ExprKind::Block(..) |
| | ExprKind::ConstBlock(_) |
| | ExprKind::If(..) |
| | ExprKind::Loop(..) |
| | ExprKind::Match(..) |
| ) && let ty::Ref(_, ty, _) = data.adjusted_ty.kind() |
| && ty.is_sized(cx.tcx, cx.param_env) |
| { |
| // Rustc bug: auto deref doesn't work on block expression when targeting sized types. |
| return; |
| } |
| |
| let (prefix, precedence) = if let Some(mutability) = mutability |
| && !cx.typeck_results().expr_ty(expr).is_ref() |
| { |
| let prefix = match mutability { |
| Mutability::Not => "&", |
| Mutability::Mut => "&mut ", |
| }; |
| (prefix, PREC_PREFIX) |
| } else { |
| ("", 0) |
| }; |
| span_lint_hir_and_then( |
| cx, |
| EXPLICIT_AUTO_DEREF, |
| data.hir_id, |
| data.span, |
| "deref which would be done by auto-deref", |
| |diag| { |
| let mut app = Applicability::MachineApplicable; |
| let (snip, snip_is_macro) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app); |
| let sugg = |
| if !snip_is_macro && expr.precedence().order() < precedence && !has_enclosing_paren(&snip) { |
| format!("{prefix}({snip})") |
| } else { |
| format!("{prefix}{snip}") |
| }; |
| diag.span_suggestion(data.span, "try", sugg, app); |
| }, |
| ); |
| }, |
| State::ExplicitDerefField { .. } => { |
| if matches!( |
| expr.kind, |
| ExprKind::Block(..) |
| | ExprKind::ConstBlock(_) |
| | ExprKind::If(..) |
| | ExprKind::Loop(..) |
| | ExprKind::Match(..) |
| ) && data.adjusted_ty.is_sized(cx.tcx, cx.param_env) |
| { |
| // Rustc bug: auto deref doesn't work on block expression when targeting sized types. |
| return; |
| } |
| |
| if let ExprKind::Field(parent_expr, _) = expr.kind |
| && let ty::Adt(adt, _) = cx.typeck_results().expr_ty(parent_expr).kind() |
| && adt.is_union() |
| { |
| // Auto deref does not apply on union field |
| return; |
| } |
| span_lint_hir_and_then( |
| cx, |
| EXPLICIT_AUTO_DEREF, |
| data.hir_id, |
| data.span, |
| "deref which would be done by auto-deref", |
| |diag| { |
| let mut app = Applicability::MachineApplicable; |
| let snip = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app).0; |
| diag.span_suggestion(data.span, "try", snip.into_owned(), app); |
| }, |
| ); |
| }, |
| State::Borrow { .. } | State::Reborrow { .. } => (), |
| } |
| } |
| |
| impl<'tcx> Dereferencing<'tcx> { |
| fn check_local_usage(&mut self, cx: &LateContext<'tcx>, e: &Expr<'tcx>, local: HirId) { |
| if let Some(outer_pat) = self.ref_locals.get_mut(&local) { |
| if let Some(pat) = outer_pat { |
| // Check for auto-deref |
| if !matches!( |
| cx.typeck_results().expr_adjustments(e), |
| [ |
| Adjustment { |
| kind: Adjust::Deref(_), |
| .. |
| }, |
| Adjustment { |
| kind: Adjust::Deref(_), |
| .. |
| }, |
| .. |
| ] |
| ) { |
| match get_parent_expr(cx, e) { |
| // Field accesses are the same no matter the number of references. |
| Some(Expr { |
| kind: ExprKind::Field(..), |
| .. |
| }) => (), |
| Some(&Expr { |
| span, |
| kind: ExprKind::Unary(UnOp::Deref, _), |
| .. |
| }) if !span.from_expansion() => { |
| // Remove explicit deref. |
| let snip = snippet_with_context(cx, e.span, span.ctxt(), "..", &mut pat.app).0; |
| pat.replacements.push((span, snip.into())); |
| }, |
| Some(parent) if !parent.span.from_expansion() => { |
| // Double reference might be needed at this point. |
| if parent.precedence().order() == PREC_POSTFIX { |
| // Parentheses would be needed here, don't lint. |
| *outer_pat = None; |
| } else { |
| pat.always_deref = false; |
| let snip = snippet_with_context(cx, e.span, parent.span.ctxt(), "..", &mut pat.app).0; |
| pat.replacements.push((e.span, format!("&{snip}"))); |
| } |
| }, |
| _ if !e.span.from_expansion() => { |
| // Double reference might be needed at this point. |
| pat.always_deref = false; |
| let snip = snippet_with_applicability(cx, e.span, "..", &mut pat.app); |
| pat.replacements.push((e.span, format!("&{snip}"))); |
| }, |
| // Edge case for macros. The span of the identifier will usually match the context of the |
| // binding, but not if the identifier was created in a macro. e.g. `concat_idents` and proc |
| // macros |
| _ => *outer_pat = None, |
| } |
| } |
| } |
| } |
| } |
| } |
