1480 lines
59 KiB
Rust
1480 lines
59 KiB
Rust
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
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use clippy_utils::mir::{enclosing_mir, expr_local, local_assignments, used_exactly_once, PossibleBorrowerMap};
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use clippy_utils::msrvs::{self, Msrv};
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use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
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use clippy_utils::sugg::has_enclosing_paren;
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use clippy_utils::ty::{is_copy, peel_mid_ty_refs};
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use clippy_utils::{
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expr_use_ctxt, get_parent_expr, get_parent_node, is_lint_allowed, path_to_local, DefinedTy, ExprUseNode,
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};
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use hir::def::DefKind;
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use hir::MatchSource;
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use rustc_ast::util::parser::{PREC_POSTFIX, PREC_PREFIX};
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use rustc_data_structures::fx::FxIndexMap;
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use rustc_data_structures::graph::iterate::{CycleDetector, TriColorDepthFirstSearch};
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use rustc_errors::Applicability;
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use rustc_hir::def::Res;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_hir::intravisit::{walk_ty, Visitor};
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use rustc_hir::{
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self as hir, BindingAnnotation, Body, BodyId, BorrowKind, Expr, ExprKind, HirId, Mutability, Node, Pat, PatKind,
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Path, QPath, TyKind, UnOp,
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};
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use rustc_index::bit_set::BitSet;
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use rustc_infer::infer::TyCtxtInferExt;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::mir::{Rvalue, StatementKind};
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use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
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use rustc_middle::ty::{
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self, ClauseKind, EarlyBinder, FnSig, GenericArg, GenericArgKind, List, ParamEnv, ParamTy, ProjectionPredicate, Ty,
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TyCtxt, TypeVisitableExt, TypeckResults,
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};
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::symbol::sym;
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use rustc_span::{Span, Symbol};
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use rustc_trait_selection::infer::InferCtxtExt as _;
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use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
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use rustc_trait_selection::traits::{Obligation, ObligationCause};
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use std::collections::VecDeque;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for explicit `deref()` or `deref_mut()` method calls.
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///
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/// ### Why is this bad?
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/// Dereferencing by `&*x` or `&mut *x` is clearer and more concise,
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/// when not part of a method chain.
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///
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/// ### Example
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/// ```rust
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/// use std::ops::Deref;
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/// let a: &mut String = &mut String::from("foo");
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/// let b: &str = a.deref();
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// let a: &mut String = &mut String::from("foo");
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/// let b = &*a;
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/// ```
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///
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/// This lint excludes all of:
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/// ```rust,ignore
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/// let _ = d.unwrap().deref();
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/// let _ = Foo::deref(&foo);
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/// let _ = <Foo as Deref>::deref(&foo);
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/// ```
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#[clippy::version = "1.44.0"]
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pub EXPLICIT_DEREF_METHODS,
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pedantic,
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"Explicit use of deref or deref_mut method while not in a method chain."
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for address of operations (`&`) that are going to
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/// be dereferenced immediately by the compiler.
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///
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/// ### Why is this bad?
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/// Suggests that the receiver of the expression borrows
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/// the expression.
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///
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/// ### Known problems
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/// The lint cannot tell when the implementation of a trait
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/// for `&T` and `T` do different things. Removing a borrow
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/// in such a case can change the semantics of the code.
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///
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/// ### Example
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/// ```rust
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/// fn fun(_a: &i32) {}
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///
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/// let x: &i32 = &&&&&&5;
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/// fun(&x);
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// # fn fun(_a: &i32) {}
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/// let x: &i32 = &5;
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/// fun(x);
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub NEEDLESS_BORROW,
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style,
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"taking a reference that is going to be automatically dereferenced"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `ref` bindings which create a reference to a reference.
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///
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/// ### Why is this bad?
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/// The address-of operator at the use site is clearer about the need for a reference.
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///
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/// ### Example
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/// ```rust
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/// let x = Some("");
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/// if let Some(ref x) = x {
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/// // use `x` here
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/// }
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// let x = Some("");
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/// if let Some(x) = x {
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/// // use `&x` here
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/// }
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/// ```
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#[clippy::version = "1.54.0"]
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pub REF_BINDING_TO_REFERENCE,
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pedantic,
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"`ref` binding to a reference"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for dereferencing expressions which would be covered by auto-deref.
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///
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/// ### Why is this bad?
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/// This unnecessarily complicates the code.
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///
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/// ### Example
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/// ```rust
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/// let x = String::new();
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/// let y: &str = &*x;
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/// ```
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/// Use instead:
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/// ```rust
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/// let x = String::new();
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/// let y: &str = &x;
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/// ```
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#[clippy::version = "1.64.0"]
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pub EXPLICIT_AUTO_DEREF,
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complexity,
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"dereferencing when the compiler would automatically dereference"
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}
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impl_lint_pass!(Dereferencing<'_> => [
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EXPLICIT_DEREF_METHODS,
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NEEDLESS_BORROW,
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REF_BINDING_TO_REFERENCE,
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EXPLICIT_AUTO_DEREF,
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]);
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#[derive(Default)]
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pub struct Dereferencing<'tcx> {
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state: Option<(State, StateData<'tcx>)>,
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// While parsing a `deref` method call in ufcs form, the path to the function is itself an
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// expression. This is to store the id of that expression so it can be skipped when
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// `check_expr` is called for it.
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skip_expr: Option<HirId>,
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/// The body the first local was found in. Used to emit lints when the traversal of the body has
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/// been finished. Note we can't lint at the end of every body as they can be nested within each
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/// other.
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current_body: Option<BodyId>,
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/// The list of locals currently being checked by the lint.
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/// If the value is `None`, then the binding has been seen as a ref pattern, but is not linted.
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/// This is needed for or patterns where one of the branches can be linted, but another can not
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/// be.
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///
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/// e.g. `m!(x) | Foo::Bar(ref x)`
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ref_locals: FxIndexMap<HirId, Option<RefPat>>,
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/// Stack of (body owner, `PossibleBorrowerMap`) pairs. Used by
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/// `needless_borrow_impl_arg_position` to determine when a borrowed expression can instead
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/// be moved.
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possible_borrowers: Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
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// `IntoIterator` for arrays requires Rust 1.53.
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msrv: Msrv,
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}
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impl<'tcx> Dereferencing<'tcx> {
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#[must_use]
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pub fn new(msrv: Msrv) -> Self {
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Self {
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msrv,
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..Dereferencing::default()
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}
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}
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}
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#[derive(Debug)]
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struct StateData<'tcx> {
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/// Span of the top level expression
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span: Span,
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hir_id: HirId,
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adjusted_ty: Ty<'tcx>,
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}
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struct DerefedBorrow {
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count: usize,
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msg: &'static str,
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stability: TyCoercionStability,
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for_field_access: Option<Symbol>,
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}
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enum State {
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// Any number of deref method calls.
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DerefMethod {
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// The number of calls in a sequence which changed the referenced type
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ty_changed_count: usize,
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is_ufcs: bool,
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/// The required mutability
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mutbl: Mutability,
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},
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DerefedBorrow(DerefedBorrow),
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ExplicitDeref {
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mutability: Option<Mutability>,
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},
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ExplicitDerefField {
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name: Symbol,
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},
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Reborrow {
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mutability: Mutability,
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},
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Borrow {
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mutability: Mutability,
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},
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}
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// A reference operation considered by this lint pass
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enum RefOp {
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Method { mutbl: Mutability, is_ufcs: bool },
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Deref,
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AddrOf(Mutability),
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}
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struct RefPat {
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/// Whether every usage of the binding is dereferenced.
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always_deref: bool,
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/// The spans of all the ref bindings for this local.
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spans: Vec<Span>,
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/// The applicability of this suggestion.
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app: Applicability,
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/// All the replacements which need to be made.
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replacements: Vec<(Span, String)>,
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/// The [`HirId`] that the lint should be emitted at.
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hir_id: HirId,
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}
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impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
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#[expect(clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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// Skip path expressions from deref calls. e.g. `Deref::deref(e)`
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if Some(expr.hir_id) == self.skip_expr.take() {
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return;
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}
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if let Some(local) = path_to_local(expr) {
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self.check_local_usage(cx, expr, local);
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}
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// Stop processing sub expressions when a macro call is seen
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if expr.span.from_expansion() {
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if let Some((state, data)) = self.state.take() {
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report(cx, expr, state, data);
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}
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return;
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}
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let typeck = cx.typeck_results();
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let Some((kind, sub_expr)) = try_parse_ref_op(cx.tcx, typeck, expr) else {
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// The whole chain of reference operations has been seen
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if let Some((state, data)) = self.state.take() {
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report(cx, expr, state, data);
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}
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return;
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};
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match (self.state.take(), kind) {
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(None, kind) => {
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let expr_ty = typeck.expr_ty(expr);
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let use_cx = expr_use_ctxt(cx, expr);
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let adjusted_ty = match &use_cx {
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Some(use_cx) => match use_cx.adjustments {
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[.., a] => a.target,
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_ => expr_ty,
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},
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_ => typeck.expr_ty_adjusted(expr),
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};
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match (use_cx, kind) {
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(Some(use_cx), RefOp::Deref) => {
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let sub_ty = typeck.expr_ty(sub_expr);
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if let ExprUseNode::FieldAccess(name) = use_cx.node
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&& adjusted_ty.ty_adt_def().map_or(true, |adt| !adt.is_union())
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&& !ty_contains_field(sub_ty, name.name)
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{
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self.state = Some((
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State::ExplicitDerefField { name: name.name },
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StateData {
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span: expr.span,
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hir_id: expr.hir_id,
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adjusted_ty,
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},
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));
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} else if sub_ty.is_ref()
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// Linting method receivers would require verifying that name lookup
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|
// would resolve the same way. This is complicated by trait methods.
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&& !use_cx.node.is_recv()
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&& let Some(ty) = use_cx.node.defined_ty(cx)
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&& TyCoercionStability::for_defined_ty(cx, ty, use_cx.node.is_return()).is_deref_stable()
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{
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self.state = Some((
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State::ExplicitDeref { mutability: None },
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StateData {
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span: expr.span,
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hir_id: expr.hir_id,
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adjusted_ty,
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},
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));
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}
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},
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(_, RefOp::Method { mutbl, is_ufcs })
|
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if !is_lint_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id)
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|
// Allow explicit deref in method chains. e.g. `foo.deref().bar()`
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&& (is_ufcs || !in_postfix_position(cx, expr)) =>
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{
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let ty_changed_count = usize::from(!deref_method_same_type(expr_ty, typeck.expr_ty(sub_expr)));
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self.state = Some((
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State::DerefMethod {
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ty_changed_count,
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is_ufcs,
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mutbl,
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},
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StateData {
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span: expr.span,
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hir_id: expr.hir_id,
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adjusted_ty,
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},
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));
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},
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|
(Some(use_cx), RefOp::AddrOf(mutability)) => {
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let defined_ty = use_cx.node.defined_ty(cx);
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|
|
|
// Check needless_borrow for generic arguments.
|
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if !use_cx.is_ty_unified
|
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&& let Some(DefinedTy::Mir(ty)) = defined_ty
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&& let ty::Param(ty) = *ty.value.skip_binder().kind()
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&& let Some((hir_id, fn_id, i)) = match use_cx.node {
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ExprUseNode::MethodArg(_, _, 0) => None,
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ExprUseNode::MethodArg(hir_id, None, i) => {
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typeck.type_dependent_def_id(hir_id).map(|id| (hir_id, id, i))
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},
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ExprUseNode::FnArg(&Expr { kind: ExprKind::Path(ref p), hir_id, .. }, i)
|
|
if !path_has_args(p) => match typeck.qpath_res(p, hir_id) {
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|
Res::Def(DefKind::Fn | DefKind::Ctor(..) | DefKind::AssocFn, id) => {
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Some((hir_id, id, i))
|
|
},
|
|
_ => None,
|
|
},
|
|
_ => None,
|
|
} && let count = needless_borrow_generic_arg_count(
|
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cx,
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&mut self.possible_borrowers,
|
|
fn_id,
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typeck.node_args(hir_id),
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i,
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|
ty,
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|
expr,
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|
&self.msrv,
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|
) && count != 0
|
|
{
|
|
self.state = Some((
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State::DerefedBorrow(DerefedBorrow {
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count: count - 1,
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msg: "the borrowed expression implements the required traits",
|
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stability: TyCoercionStability::None,
|
|
for_field_access: None,
|
|
}),
|
|
StateData {
|
|
span: expr.span,
|
|
hir_id: expr.hir_id,
|
|
adjusted_ty: use_cx.adjustments.last().map_or(expr_ty, |a| a.target),
|
|
},
|
|
));
|
|
return;
|
|
}
|
|
|
|
// 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 = defined_ty.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()
|
|
&& cx.tcx.infer_ctxt().build()
|
|
.type_implements_trait(
|
|
trait_id,
|
|
[impl_ty.into()].into_iter().chain(args.iter().copied()),
|
|
cx.param_env,
|
|
)
|
|
.must_apply_modulo_regions()
|
|
{
|
|
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() {
|
|
self.state = Some((
|
|
State::ExplicitDeref { mutability: None },
|
|
StateData {
|
|
span: expr.span,
|
|
hir_id: expr.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 self.possible_borrowers.last().map_or(false, |&(local_def_id, _)| {
|
|
local_def_id == cx.tcx.hir().body_owner_def_id(body.id())
|
|
}) {
|
|
self.possible_borrowers.pop();
|
|
}
|
|
|
|
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;
|
|
}
|
|
}
|
|
|
|
extract_msrv_attr!(LateContext);
|
|
}
|
|
|
|
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 path_has_args(p: &QPath<'_>) -> bool {
|
|
match *p {
|
|
QPath::Resolved(_, Path { segments: [.., s], .. }) | QPath::TypeRelative(_, s) => s.args.is_some(),
|
|
_ => 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.ctxt() == e.span.ctxt()
|
|
{
|
|
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::Generator(..)
|
|
| ty::GeneratorWitness(..)
|
|
| ty::GeneratorWitnessMIR(..)
|
|
| 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
|
|
}
|
|
|
|
/// Checks for the number of borrow expressions which can be removed from the given expression
|
|
/// where the expression is used as an argument to a function expecting a generic type.
|
|
///
|
|
/// The following constraints will be checked:
|
|
/// * The borrowed expression meets all the generic type's constraints.
|
|
/// * The generic type appears only once in the functions signature.
|
|
/// * The borrowed value will not be moved if it is used later in the function.
|
|
#[expect(clippy::too_many_arguments)]
|
|
fn needless_borrow_generic_arg_count<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
|
|
fn_id: DefId,
|
|
callee_args: &'tcx List<GenericArg<'tcx>>,
|
|
arg_index: usize,
|
|
param_ty: ParamTy,
|
|
mut expr: &Expr<'tcx>,
|
|
msrv: &Msrv,
|
|
) -> usize {
|
|
let destruct_trait_def_id = cx.tcx.lang_items().destruct_trait();
|
|
let sized_trait_def_id = cx.tcx.lang_items().sized_trait();
|
|
|
|
let fn_sig = cx.tcx.fn_sig(fn_id).instantiate_identity().skip_binder();
|
|
let predicates = cx.tcx.param_env(fn_id).caller_bounds();
|
|
let projection_predicates = predicates
|
|
.iter()
|
|
.filter_map(|predicate| {
|
|
if let ClauseKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
|
|
Some(projection_predicate)
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
.collect::<Vec<_>>();
|
|
|
|
let mut trait_with_ref_mut_self_method = false;
|
|
|
|
// If no traits were found, or only the `Destruct`, `Sized`, or `Any` traits were found, return.
|
|
if predicates
|
|
.iter()
|
|
.filter_map(|predicate| {
|
|
if let ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder()
|
|
&& trait_predicate.trait_ref.self_ty() == param_ty.to_ty(cx.tcx)
|
|
{
|
|
Some(trait_predicate.trait_ref.def_id)
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
.inspect(|trait_def_id| {
|
|
trait_with_ref_mut_self_method |= has_ref_mut_self_method(cx, *trait_def_id);
|
|
})
|
|
.all(|trait_def_id| {
|
|
Some(trait_def_id) == destruct_trait_def_id
|
|
|| Some(trait_def_id) == sized_trait_def_id
|
|
|| cx.tcx.is_diagnostic_item(sym::Any, trait_def_id)
|
|
})
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
// See:
|
|
// - https://github.com/rust-lang/rust-clippy/pull/9674#issuecomment-1289294201
|
|
// - https://github.com/rust-lang/rust-clippy/pull/9674#issuecomment-1292225232
|
|
if projection_predicates
|
|
.iter()
|
|
.any(|projection_predicate| is_mixed_projection_predicate(cx, fn_id, projection_predicate))
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
// `args_with_referent_ty` can be constructed outside of `check_referent` because the same
|
|
// elements are modified each time `check_referent` is called.
|
|
let mut args_with_referent_ty = callee_args.to_vec();
|
|
|
|
let mut check_reference_and_referent = |reference, referent| {
|
|
let referent_ty = cx.typeck_results().expr_ty(referent);
|
|
|
|
if !is_copy(cx, referent_ty)
|
|
&& (referent_ty.has_significant_drop(cx.tcx, cx.param_env)
|
|
|| !referent_used_exactly_once(cx, possible_borrowers, reference))
|
|
{
|
|
return false;
|
|
}
|
|
|
|
// https://github.com/rust-lang/rust-clippy/pull/9136#pullrequestreview-1037379321
|
|
if trait_with_ref_mut_self_method && !matches!(referent_ty.kind(), ty::Ref(_, _, Mutability::Mut)) {
|
|
return false;
|
|
}
|
|
|
|
if !replace_types(
|
|
cx,
|
|
param_ty,
|
|
referent_ty,
|
|
fn_sig,
|
|
arg_index,
|
|
&projection_predicates,
|
|
&mut args_with_referent_ty,
|
|
) {
|
|
return false;
|
|
}
|
|
|
|
predicates.iter().all(|predicate| {
|
|
if let ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder()
|
|
&& cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_predicate.trait_ref.def_id)
|
|
&& let ty::Param(param_ty) = trait_predicate.self_ty().kind()
|
|
&& let GenericArgKind::Type(ty) = args_with_referent_ty[param_ty.index as usize].unpack()
|
|
&& ty.is_array()
|
|
&& !msrv.meets(msrvs::ARRAY_INTO_ITERATOR)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
let predicate = EarlyBinder::bind(predicate).instantiate(cx.tcx, &args_with_referent_ty);
|
|
let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate);
|
|
let infcx = cx.tcx.infer_ctxt().build();
|
|
infcx.predicate_must_hold_modulo_regions(&obligation)
|
|
})
|
|
};
|
|
|
|
let mut count = 0;
|
|
while let ExprKind::AddrOf(_, _, referent) = expr.kind {
|
|
if !check_reference_and_referent(expr, referent) {
|
|
break;
|
|
}
|
|
expr = referent;
|
|
count += 1;
|
|
}
|
|
count
|
|
}
|
|
|
|
fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
|
|
cx.tcx
|
|
.associated_items(trait_def_id)
|
|
.in_definition_order()
|
|
.any(|assoc_item| {
|
|
if assoc_item.fn_has_self_parameter {
|
|
let self_ty = cx
|
|
.tcx
|
|
.fn_sig(assoc_item.def_id)
|
|
.instantiate_identity()
|
|
.skip_binder()
|
|
.inputs()[0];
|
|
matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Mut))
|
|
} else {
|
|
false
|
|
}
|
|
})
|
|
}
|
|
|
|
fn is_mixed_projection_predicate<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
callee_def_id: DefId,
|
|
projection_predicate: &ProjectionPredicate<'tcx>,
|
|
) -> bool {
|
|
let generics = cx.tcx.generics_of(callee_def_id);
|
|
// The predicate requires the projected type to equal a type parameter from the parent context.
|
|
if let Some(term_ty) = projection_predicate.term.ty()
|
|
&& let ty::Param(term_param_ty) = term_ty.kind()
|
|
&& (term_param_ty.index as usize) < generics.parent_count
|
|
{
|
|
// The inner-most self type is a type parameter from the current function.
|
|
let mut projection_ty = projection_predicate.projection_ty;
|
|
loop {
|
|
match projection_ty.self_ty().kind() {
|
|
ty::Alias(ty::Projection, inner_projection_ty) => {
|
|
projection_ty = *inner_projection_ty;
|
|
}
|
|
ty::Param(param_ty) => {
|
|
return (param_ty.index as usize) >= generics.parent_count;
|
|
}
|
|
_ => {
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
fn referent_used_exactly_once<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
|
|
reference: &Expr<'tcx>,
|
|
) -> bool {
|
|
if let Some(mir) = enclosing_mir(cx.tcx, reference.hir_id)
|
|
&& let Some(local) = expr_local(cx.tcx, reference)
|
|
&& let [location] = *local_assignments(mir, local).as_slice()
|
|
&& let Some(statement) = mir.basic_blocks[location.block].statements.get(location.statement_index)
|
|
&& let StatementKind::Assign(box (_, Rvalue::Ref(_, _, place))) = statement.kind
|
|
&& !place.is_indirect_first_projection()
|
|
// Ensure not in a loop (https://github.com/rust-lang/rust-clippy/issues/9710)
|
|
&& TriColorDepthFirstSearch::new(&mir.basic_blocks).run_from(location.block, &mut CycleDetector).is_none()
|
|
{
|
|
let body_owner_local_def_id = cx.tcx.hir().enclosing_body_owner(reference.hir_id);
|
|
if possible_borrowers
|
|
.last()
|
|
.map_or(true, |&(local_def_id, _)| local_def_id != body_owner_local_def_id)
|
|
{
|
|
possible_borrowers.push((body_owner_local_def_id, PossibleBorrowerMap::new(cx, mir)));
|
|
}
|
|
let possible_borrower = &mut possible_borrowers.last_mut().unwrap().1;
|
|
// If `only_borrowers` were used here, the `copyable_iterator::warn` test would fail. The reason is
|
|
// that `PossibleBorrowerVisitor::visit_terminator` considers `place.local` a possible borrower of
|
|
// itself. See the comment in that method for an explanation as to why.
|
|
possible_borrower.bounded_borrowers(&[local], &[local, place.local], place.local, location)
|
|
&& used_exactly_once(mir, place.local).unwrap_or(false)
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
// Iteratively replaces `param_ty` with `new_ty` in `args`, and similarly for each resulting
|
|
// projected type that is a type parameter. Returns `false` if replacing the types would have an
|
|
// effect on the function signature beyond substituting `new_ty` for `param_ty`.
|
|
// See: https://github.com/rust-lang/rust-clippy/pull/9136#discussion_r927212757
|
|
fn replace_types<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
param_ty: ParamTy,
|
|
new_ty: Ty<'tcx>,
|
|
fn_sig: FnSig<'tcx>,
|
|
arg_index: usize,
|
|
projection_predicates: &[ProjectionPredicate<'tcx>],
|
|
args: &mut [ty::GenericArg<'tcx>],
|
|
) -> bool {
|
|
let mut replaced = BitSet::new_empty(args.len());
|
|
|
|
let mut deque = VecDeque::with_capacity(args.len());
|
|
deque.push_back((param_ty, new_ty));
|
|
|
|
while let Some((param_ty, new_ty)) = deque.pop_front() {
|
|
// If `replaced.is_empty()`, then `param_ty` and `new_ty` are those initially passed in.
|
|
if !fn_sig
|
|
.inputs_and_output
|
|
.iter()
|
|
.enumerate()
|
|
.all(|(i, ty)| (replaced.is_empty() && i == arg_index) || !ty.contains(param_ty.to_ty(cx.tcx)))
|
|
{
|
|
return false;
|
|
}
|
|
|
|
args[param_ty.index as usize] = ty::GenericArg::from(new_ty);
|
|
|
|
// The `replaced.insert(...)` check provides some protection against infinite loops.
|
|
if replaced.insert(param_ty.index) {
|
|
for projection_predicate in projection_predicates {
|
|
if projection_predicate.projection_ty.self_ty() == param_ty.to_ty(cx.tcx)
|
|
&& let Some(term_ty) = projection_predicate.term.ty()
|
|
&& let ty::Param(term_param_ty) = term_ty.kind()
|
|
{
|
|
let projection = cx.tcx.mk_ty_from_kind(ty::Alias(
|
|
ty::Projection,
|
|
projection_predicate.projection_ty.with_self_ty(cx.tcx, new_ty),
|
|
));
|
|
|
|
if let Ok(projected_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, projection)
|
|
&& args[term_param_ty.index as usize] != ty::GenericArg::from(projected_ty)
|
|
{
|
|
deque.push_back((*term_param_ty, projected_ty));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
true
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
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,
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|