-use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
+use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
+use clippy_utils::mir::{enclosing_mir, expr_local, local_assignments, used_exactly_once, PossibleBorrowerMap};
use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
-use clippy_utils::ty::peel_mid_ty_refs;
-use clippy_utils::{get_parent_expr, get_parent_node, is_lint_allowed, path_to_local};
+use clippy_utils::sugg::has_enclosing_paren;
+use clippy_utils::ty::{expr_sig, is_copy, peel_mid_ty_refs, ty_sig, variant_of_res};
+use clippy_utils::{
+ fn_def_id, get_parent_expr, get_parent_expr_for_hir, is_lint_allowed, meets_msrv, msrvs, path_to_local,
+ walk_to_expr_usage,
+};
use rustc_ast::util::parser::{PREC_POSTFIX, PREC_PREFIX};
use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::graph::iterate::{CycleDetector, TriColorDepthFirstSearch};
use rustc_errors::Applicability;
+use rustc_hir::intravisit::{walk_ty, Visitor};
use rustc_hir::{
- BindingAnnotation, Body, BodyId, BorrowKind, Destination, Expr, ExprKind, HirId, MatchSource, Mutability, Node,
- Pat, PatKind, UnOp,
+ self as hir,
+ def_id::{DefId, LocalDefId},
+ BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy, GenericArg, HirId, ImplItem,
+ ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind, Path, QPath, TraitItem,
+ TraitItemKind, TyKind, UnOp,
};
+use rustc_index::bit_set::BitSet;
+use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
-use rustc_middle::ty::{self, Ty, TyCtxt, TyS, TypeckResults};
+use rustc_middle::mir::{Rvalue, StatementKind};
+use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
+use rustc_middle::ty::{
+ self, Binder, BoundVariableKind, EarlyBinder, FnSig, GenericArgKind, List, ParamTy, PredicateKind,
+ ProjectionPredicate, Ty, TyCtxt, TypeVisitable, TypeckResults,
+};
+use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::{symbol::sym, Span};
-use std::iter;
+use rustc_span::{symbol::sym, Span, Symbol};
+use rustc_trait_selection::infer::InferCtxtExt as _;
+use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
+use std::collections::VecDeque;
declare_clippy_lint! {
/// ### What it does
/// let a: &mut String = &mut String::from("foo");
/// let b: &str = a.deref();
/// ```
- /// Could be written as:
+ ///
+ /// Use instead:
/// ```rust
/// let a: &mut String = &mut String::from("foo");
/// let b = &*a;
/// ```
///
- /// This lint excludes
+ /// This lint excludes:
/// ```rust,ignore
/// let _ = d.unwrap().deref();
/// ```
/// ```rust
/// fn fun(_a: &i32) {}
///
- /// // Bad
/// let x: &i32 = &&&&&&5;
/// fun(&x);
+ /// ```
///
- /// // Good
+ /// Use instead:
+ /// ```rust
+ /// # fn fun(_a: &i32) {}
/// let x: &i32 = &5;
/// fun(x);
/// ```
///
/// ### Example
/// ```rust
- /// // Bad
/// let x = Some("");
/// if let Some(ref x) = x {
/// // use `x` here
/// }
+ /// ```
///
- /// // Good
+ /// Use instead:
+ /// ```rust
/// let x = Some("");
/// if let Some(x) = x {
/// // use `&x` here
"`ref` binding to a reference"
}
-impl_lint_pass!(Dereferencing => [
+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
+ /// ```rust
+ /// let x = String::new();
+ /// let y: &str = &*x;
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// 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 {
+pub struct Dereferencing<'tcx> {
state: Option<(State, StateData)>,
// While parsing a `deref` method call in ufcs form, the path to the function is itself an
/// 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
///
/// e.g. `m!(x) | Foo::Bar(ref x)`
ref_locals: FxIndexMap<HirId, Option<RefPat>>,
+
+ /// Stack of (body owner, `PossibleBorrowerMap`) pairs. Used by
+ /// `needless_borrow_impl_arg_position` to determine when a borrowed expression can instead
+ /// be moved.
+ possible_borrowers: Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
+
+ // `IntoIterator` for arrays requires Rust 1.53.
+ msrv: Option<RustcVersion>,
+}
+
+impl<'tcx> Dereferencing<'tcx> {
+ #[must_use]
+ pub fn new(msrv: Option<RustcVersion>) -> Self {
+ Self {
+ msrv,
+ ..Dereferencing::default()
+ }
+ }
}
+#[derive(Debug)]
struct StateData {
/// Span of the top level expression
span: Span,
- /// The required mutability
- target_mut: Mutability,
+ hir_id: HirId,
+ position: Position,
}
+#[derive(Debug)]
+struct DerefedBorrow {
+ count: usize,
+ msg: &'static str,
+ snip_expr: Option<HirId>,
+}
+
+#[derive(Debug)]
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_final_ufcs: bool,
+ /// The required mutability
+ target_mut: Mutability,
+ },
+ DerefedBorrow(DerefedBorrow),
+ ExplicitDeref {
+ mutability: Option<Mutability>,
+ },
+ ExplicitDerefField {
+ name: Symbol,
},
- DerefedBorrow {
- count: u32,
+ Reborrow {
+ mutability: Mutability,
+ },
+ Borrow {
+ mutability: Mutability,
},
}
enum RefOp {
Method(Mutability),
Deref,
- AddrOf,
+ AddrOf(Mutability),
}
struct RefPat {
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 {
- #[allow(clippy::too_many_lines)]
+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() {
}
let typeck = cx.typeck_results();
- let (kind, sub_expr) = if let Some(x) = try_parse_ref_op(cx.tcx, typeck, expr) {
- x
- } else {
+ 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);
match (self.state.take(), kind) {
(None, kind) => {
- let parent = get_parent_node(cx.tcx, expr.hir_id);
let expr_ty = typeck.expr_ty(expr);
-
+ let (position, adjustments) = walk_parents(cx, &mut self.possible_borrowers, expr, self.msrv);
match kind {
+ RefOp::Deref => {
+ if let Position::FieldAccess {
+ name,
+ of_union: false,
+ } = position
+ && !ty_contains_field(typeck.expr_ty(sub_expr), name)
+ {
+ self.state = Some((
+ State::ExplicitDerefField { name },
+ StateData { span: expr.span, hir_id: expr.hir_id, position },
+ ));
+ } else if position.is_deref_stable() {
+ self.state = Some((
+ State::ExplicitDeref { mutability: None },
+ StateData { span: expr.span, hir_id: expr.hir_id, position },
+ ));
+ }
+ }
RefOp::Method(target_mut)
if !is_lint_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id)
- && is_linted_explicit_deref_position(parent, expr.hir_id, expr.span) =>
+ && position.lint_explicit_deref() =>
{
+ 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: if deref_method_same_type(expr_ty, typeck.expr_ty(sub_expr)) {
- 0
- } else {
- 1
- },
+ ty_changed_count,
is_final_ufcs: matches!(expr.kind, ExprKind::Call(..)),
+ target_mut,
},
StateData {
span: expr.span,
- target_mut,
+ hir_id: expr.hir_id,
+ position
},
));
},
- RefOp::AddrOf => {
+ RefOp::AddrOf(mutability) => {
// Find the number of times the borrow is auto-derefed.
- let mut iter = find_adjustments(cx.tcx, typeck, expr).iter();
- if let Some((i, adjust)) = iter.by_ref().enumerate().find_map(|(i, adjust)| {
- if !matches!(adjust.kind, Adjust::Deref(_)) {
- Some((i, adjust))
- } else if !adjust.target.is_ref() {
- // Add one to the number of references found.
- Some((i + 1, adjust))
+ let mut iter = 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,
+ };
+ };
+
+ // 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.
+ // 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 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";
+ let impl_msg = "the borrowed expression implements the required traits";
+
+ let (required_refs, msg, snip_expr) = if position.can_auto_borrow() {
+ (1, if deref_count == 1 { borrow_msg } else { deref_msg }, None)
+ } else if let Position::ImplArg(hir_id) = position {
+ (0, impl_msg, Some(hir_id))
+ } else if let Some(&Adjust::Borrow(AutoBorrow::Ref(_, mutability))) =
+ next_adjust.map(|a| &a.kind)
+ {
+ if matches!(mutability, AutoBorrowMutability::Mut { .. }) && !position.is_reborrow_stable()
+ {
+ (3, deref_msg, None)
} else {
- None
- }
- }) {
- // Found two consecutive derefs. At least one can be removed.
- if i > 1 {
- let target_mut = iter::once(adjust)
- .chain(iter)
- .find_map(|adjust| match adjust.kind {
- Adjust::Borrow(AutoBorrow::Ref(_, m)) => Some(m.into()),
- _ => None,
- })
- // This default should never happen. Auto-deref always reborrows.
- .unwrap_or(Mutability::Not);
- self.state = Some((
- // Subtract one for the current borrow expression, and one to cover the last
- // reference which can't be removed (it's either reborrowed, or needed for
- // auto-deref to happen).
- State::DerefedBorrow {
- count:
- // Truncation here would require more than a `u32::MAX` level reference. The compiler
- // does not support this.
- #[allow(clippy::cast_possible_truncation)]
- { i as u32 - 2 }
- },
- StateData {
- span: expr.span,
- target_mut,
- },
- ));
+ (2, deref_msg, None)
}
+ } else {
+ (2, deref_msg, None)
+ };
+
+ 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,
+ snip_expr,
+ }),
+ StateData { span: expr.span, hir_id: expr.hir_id, position },
+ ));
+ } else if position.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,
+ position
+ },
+ ));
}
},
- _ => (),
+ RefOp::Method(..) => (),
}
},
- (Some((State::DerefMethod { ty_changed_count, .. }, data)), RefOp::Method(_)) => {
+ (
+ Some((
+ State::DerefMethod {
+ target_mut,
+ ty_changed_count,
+ ..
+ },
+ data,
+ )),
+ RefOp::Method(_),
+ ) => {
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 + 1
},
is_final_ufcs: matches!(expr.kind, ExprKind::Call(..)),
+ target_mut,
+ },
+ 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 position = data.position;
+ report(cx, expr, State::DerefedBorrow(state), data);
+ if position.is_deref_stable() {
+ self.state = Some((
+ State::Borrow { mutability },
+ StateData {
+ span: expr.span,
+ hir_id: expr.hir_id,
+ position,
+ },
+ ));
+ }
+ },
+ (Some((State::DerefedBorrow(state), data)), RefOp::Deref) => {
+ let position = data.position;
+ report(cx, expr, State::DerefedBorrow(state), data);
+ if let Position::FieldAccess{name, ..} = position
+ && !ty_contains_field(typeck.expr_ty(sub_expr), name)
+ {
+ self.state = Some((
+ State::ExplicitDerefField { name },
+ StateData { span: expr.span, hir_id: expr.hir_id, position },
+ ));
+ } else if position.is_deref_stable() {
+ self.state = Some((
+ State::ExplicitDeref { mutability: None },
+ StateData { span: expr.span, hir_id: expr.hir_id, position },
+ ));
+ }
+ },
+
+ (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,
));
},
- (Some((State::DerefedBorrow { count }, data)), RefOp::AddrOf) if count != 0 => {
- self.state = Some((State::DerefedBorrow { count: count - 1 }, 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 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 {
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;
- span_lint_and_then(
+ let lint = if pat.always_deref {
+ NEEDLESS_BORROW
+ } else {
+ REF_BINDING_TO_REFERENCE
+ };
+ span_lint_hir_and_then(
cx,
- if pat.always_deref {
- NEEDLESS_BORROW
- } else {
- REF_BINDING_TO_REFERENCE
- },
+ lint,
+ pat.hir_id,
pat.spans,
"this pattern creates a reference to a reference",
|diag| {
self.current_body = None;
}
}
+
+ extract_msrv_attr!(LateContext);
}
fn try_parse_ref_op<'tcx>(
expr: &'tcx Expr<'_>,
) -> Option<(RefOp, &'tcx Expr<'tcx>)> {
let (def_id, arg) = match expr.kind {
- ExprKind::MethodCall(_, [arg], _) => (typeck.type_dependent_def_id(expr.hir_id)?, arg),
+ ExprKind::MethodCall(_, arg, [], _) => (typeck.type_dependent_def_id(expr.hir_id)?, arg),
ExprKind::Call(
Expr {
kind: ExprKind::Path(path),
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, _, sub_expr) => return Some((RefOp::AddrOf, 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) {
// Checks whether the type for a deref call actually changed the type, not just the mutability of
// the reference.
-fn deref_method_same_type(result_ty: Ty<'_>, arg_ty: Ty<'_>) -> bool {
+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, _)) => TyS::same_type(result_ty, arg_ty),
+ (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
}
}
-// Checks whether the parent node is a suitable context for switching from a deref method to the
-// deref operator.
-fn is_linted_explicit_deref_position(parent: Option<Node<'_>>, child_id: HirId, child_span: Span) -> bool {
- let parent = match parent {
- Some(Node::Expr(e)) if e.span.ctxt() == child_span.ctxt() => e,
- _ => return true,
- };
- match parent.kind {
- // Leave deref calls in the middle of a method chain.
- // e.g. x.deref().foo()
- ExprKind::MethodCall(_, [self_arg, ..], _) if self_arg.hir_id == child_id => false,
-
- // Leave deref calls resulting in a called function
- // e.g. (x.deref())()
- ExprKind::Call(func_expr, _) if func_expr.hir_id == child_id => false,
-
- // Makes an ugly suggestion
- // e.g. *x.deref() => *&*x
- ExprKind::Unary(UnOp::Deref, _)
- // Postfix expressions would require parens
- | ExprKind::Match(_, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar)
- | ExprKind::Field(..)
- | ExprKind::Index(..)
- | ExprKind::Err => false,
-
- ExprKind::Box(..)
- | ExprKind::ConstBlock(..)
- | ExprKind::Array(_)
- | ExprKind::Call(..)
- | ExprKind::MethodCall(..)
- | ExprKind::Tup(..)
- | ExprKind::Binary(..)
- | ExprKind::Unary(..)
- | ExprKind::Lit(..)
- | ExprKind::Cast(..)
- | ExprKind::Type(..)
- | ExprKind::DropTemps(..)
- | ExprKind::If(..)
- | ExprKind::Loop(..)
- | ExprKind::Match(..)
- | ExprKind::Let(..)
- | ExprKind::Closure(..)
- | ExprKind::Block(..)
- | ExprKind::Assign(..)
- | ExprKind::AssignOp(..)
- | ExprKind::Path(..)
- | ExprKind::AddrOf(..)
- | ExprKind::Break(..)
- | ExprKind::Continue(..)
- | ExprKind::Ret(..)
- | ExprKind::InlineAsm(..)
- | ExprKind::Struct(..)
- | ExprKind::Repeat(..)
- | ExprKind::Yield(..) => true,
+/// The position of an expression relative to it's parent.
+#[derive(Clone, Copy, Debug)]
+enum Position {
+ MethodReceiver,
+ /// The method is defined on a reference type. e.g. `impl Foo for &T`
+ MethodReceiverRefImpl,
+ Callee,
+ ImplArg(HirId),
+ FieldAccess {
+ name: Symbol,
+ of_union: bool,
+ }, // union fields cannot be auto borrowed
+ Postfix,
+ Deref,
+ /// Any other location which will trigger auto-deref to a specific time.
+ /// Contains the precedence of the parent expression and whether the target type is sized.
+ DerefStable(i8, bool),
+ /// Any other location which will trigger auto-reborrowing.
+ /// Contains the precedence of the parent expression.
+ ReborrowStable(i8),
+ /// Contains the precedence of the parent expression.
+ Other(i8),
+}
+impl Position {
+ fn is_deref_stable(self) -> bool {
+ matches!(self, Self::DerefStable(..))
+ }
+
+ fn is_reborrow_stable(self) -> bool {
+ matches!(self, Self::DerefStable(..) | Self::ReborrowStable(_))
+ }
+
+ fn can_auto_borrow(self) -> bool {
+ matches!(
+ self,
+ Self::MethodReceiver | Self::FieldAccess { of_union: false, .. } | Self::Callee
+ )
+ }
+
+ fn lint_explicit_deref(self) -> bool {
+ matches!(self, Self::Other(_) | Self::DerefStable(..) | Self::ReborrowStable(_))
+ }
+
+ fn precedence(self) -> i8 {
+ match self {
+ Self::MethodReceiver
+ | Self::MethodReceiverRefImpl
+ | Self::Callee
+ | Self::FieldAccess { .. }
+ | Self::Postfix => PREC_POSTFIX,
+ Self::ImplArg(_) | Self::Deref => PREC_PREFIX,
+ Self::DerefStable(p, _) | Self::ReborrowStable(p) | Self::Other(p) => p,
+ }
}
}
-/// Adjustments are sometimes made in the parent block rather than the expression itself.
-fn find_adjustments<'tcx>(
- tcx: TyCtxt<'tcx>,
- typeck: &'tcx TypeckResults<'_>,
- expr: &'tcx Expr<'_>,
-) -> &'tcx [Adjustment<'tcx>] {
- let map = tcx.hir();
- let mut iter = map.parent_iter(expr.hir_id);
- let mut prev = expr;
+/// Walks up the parent expressions attempting to determine both how stable the auto-deref result
+/// is, and which adjustments will be applied to it. Note this will not consider auto-borrow
+/// locations as those follow different rules.
+#[expect(clippy::too_many_lines)]
+fn walk_parents<'tcx>(
+ cx: &LateContext<'tcx>,
+ possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
+ e: &'tcx Expr<'_>,
+ msrv: Option<RustcVersion>,
+) -> (Position, &'tcx [Adjustment<'tcx>]) {
+ let mut adjustments = [].as_slice();
+ let mut precedence = 0i8;
+ let ctxt = e.span.ctxt();
+ let position = walk_to_expr_usage(cx, e, &mut |parent, child_id| {
+ // LocalTableInContext returns the wrong lifetime, so go use `expr_adjustments` instead.
+ if adjustments.is_empty() && let Node::Expr(e) = cx.tcx.hir().get(child_id) {
+ adjustments = cx.typeck_results().expr_adjustments(e);
+ }
+ match parent {
+ Node::Local(Local { ty: Some(ty), span, .. }) if span.ctxt() == ctxt => {
+ Some(binding_ty_auto_deref_stability(cx, ty, precedence, List::empty()))
+ },
+ Node::Item(&Item {
+ kind: ItemKind::Static(..) | ItemKind::Const(..),
+ owner_id,
+ span,
+ ..
+ })
+ | Node::TraitItem(&TraitItem {
+ kind: TraitItemKind::Const(..),
+ owner_id,
+ span,
+ ..
+ })
+ | Node::ImplItem(&ImplItem {
+ kind: ImplItemKind::Const(..),
+ owner_id,
+ span,
+ ..
+ }) if span.ctxt() == ctxt => {
+ let ty = cx.tcx.type_of(owner_id.def_id);
+ Some(ty_auto_deref_stability(cx, ty, precedence).position_for_result(cx))
+ },
- loop {
- match typeck.expr_adjustments(prev) {
- [] => (),
- a => break a,
- };
+ Node::Item(&Item {
+ kind: ItemKind::Fn(..),
+ owner_id,
+ span,
+ ..
+ })
+ | Node::TraitItem(&TraitItem {
+ kind: TraitItemKind::Fn(..),
+ owner_id,
+ span,
+ ..
+ })
+ | Node::ImplItem(&ImplItem {
+ kind: ImplItemKind::Fn(..),
+ owner_id,
+ span,
+ ..
+ }) if span.ctxt() == ctxt => {
+ let output = cx
+ .tcx
+ .erase_late_bound_regions(cx.tcx.fn_sig(owner_id.to_def_id()).output());
+ Some(ty_auto_deref_stability(cx, output, precedence).position_for_result(cx))
+ },
+
+ Node::ExprField(field) if field.span.ctxt() == ctxt => match get_parent_expr_for_hir(cx, field.hir_id) {
+ Some(Expr {
+ hir_id,
+ kind: ExprKind::Struct(path, ..),
+ ..
+ }) => variant_of_res(cx, cx.qpath_res(path, *hir_id))
+ .and_then(|variant| variant.fields.iter().find(|f| f.name == field.ident.name))
+ .map(|field_def| {
+ ty_auto_deref_stability(cx, cx.tcx.type_of(field_def.did), precedence).position_for_arg()
+ }),
+ _ => None,
+ },
+
+ Node::Expr(parent) if parent.span.ctxt() == ctxt => match parent.kind {
+ ExprKind::Ret(_) => {
+ let owner_id = cx.tcx.hir().body_owner(cx.enclosing_body.unwrap());
+ Some(
+ if let Node::Expr(
+ closure_expr @ Expr {
+ kind: ExprKind::Closure(closure),
+ ..
+ },
+ ) = cx.tcx.hir().get(owner_id)
+ {
+ closure_result_position(cx, closure, cx.typeck_results().expr_ty(closure_expr), precedence)
+ } else {
+ let output = cx
+ .tcx
+ .erase_late_bound_regions(cx.tcx.fn_sig(cx.tcx.hir().local_def_id(owner_id)).output());
+ ty_auto_deref_stability(cx, output, precedence).position_for_result(cx)
+ },
+ )
+ },
+ ExprKind::Closure(closure) => Some(closure_result_position(
+ cx,
+ closure,
+ cx.typeck_results().expr_ty(parent),
+ precedence,
+ )),
+ ExprKind::Call(func, _) if func.hir_id == child_id => {
+ (child_id == e.hir_id).then_some(Position::Callee)
+ },
+ ExprKind::Call(func, args) => args
+ .iter()
+ .position(|arg| arg.hir_id == child_id)
+ .zip(expr_sig(cx, func))
+ .and_then(|(i, sig)| {
+ sig.input_with_hir(i).map(|(hir_ty, ty)| {
+ match hir_ty {
+ // Type inference for closures can depend on how they're called. Only go by the explicit
+ // types here.
+ Some(hir_ty) => {
+ binding_ty_auto_deref_stability(cx, hir_ty, precedence, ty.bound_vars())
+ },
+ None => {
+ // `e.hir_id == child_id` for https://github.com/rust-lang/rust-clippy/issues/9739
+ // `!call_is_qualified(func)` for https://github.com/rust-lang/rust-clippy/issues/9782
+ if e.hir_id == child_id
+ && !call_is_qualified(func)
+ && let ty::Param(param_ty) = ty.skip_binder().kind()
+ {
+ needless_borrow_impl_arg_position(
+ cx,
+ possible_borrowers,
+ parent,
+ i,
+ *param_ty,
+ e,
+ precedence,
+ msrv,
+ )
+ } else {
+ ty_auto_deref_stability(cx, cx.tcx.erase_late_bound_regions(ty), precedence)
+ .position_for_arg()
+ }
+ },
+ }
+ })
+ }),
+ ExprKind::MethodCall(method, receiver, args, _) => {
+ let id = cx.typeck_results().type_dependent_def_id(parent.hir_id).unwrap();
+ if receiver.hir_id == child_id {
+ // 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 e.hir_id != child_id {
+ return Some(Position::ReborrowStable(precedence))
+ } else if let Some(trait_id) = cx.tcx.trait_of_item(id)
+ && let arg_ty = cx.tcx.erase_regions(cx.typeck_results().expr_ty_adjusted(e))
+ && let ty::Ref(_, sub_ty, _) = *arg_ty.kind()
+ && let subs = cx
+ .typeck_results()
+ .node_substs_opt(parent.hir_id).map(|subs| &subs[1..]).unwrap_or_default()
+ && let impl_ty = if cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref() {
+ // Trait methods taking `&self`
+ sub_ty
+ } else {
+ // Trait methods taking `self`
+ arg_ty
+ } && impl_ty.is_ref()
+ && let infcx = cx.tcx.infer_ctxt().build()
+ && infcx
+ .type_implements_trait(trait_id, [impl_ty.into()].into_iter().chain(subs.iter().copied()), cx.param_env)
+ .must_apply_modulo_regions()
+ {
+ return Some(Position::MethodReceiverRefImpl)
+ }
+ return Some(Position::MethodReceiver);
+ }
+ args.iter().position(|arg| arg.hir_id == child_id).map(|i| {
+ let ty = cx.tcx.fn_sig(id).skip_binder().inputs()[i + 1];
+ // `e.hir_id == child_id` for https://github.com/rust-lang/rust-clippy/issues/9739
+ // `method.args.is_none()` for https://github.com/rust-lang/rust-clippy/issues/9782
+ if e.hir_id == child_id && method.args.is_none() && let ty::Param(param_ty) = ty.kind() {
+ needless_borrow_impl_arg_position(
+ cx,
+ possible_borrowers,
+ parent,
+ i + 1,
+ *param_ty,
+ e,
+ precedence,
+ msrv,
+ )
+ } else {
+ ty_auto_deref_stability(
+ cx,
+ cx.tcx.erase_late_bound_regions(cx.tcx.fn_sig(id).input(i + 1)),
+ precedence,
+ )
+ .position_for_arg()
+ }
+ })
+ },
+ ExprKind::Field(child, name) if child.hir_id == e.hir_id => Some(Position::FieldAccess {
+ name: name.name,
+ of_union: is_union(cx.typeck_results(), child),
+ }),
+ ExprKind::Unary(UnOp::Deref, child) if child.hir_id == e.hir_id => Some(Position::Deref),
+ ExprKind::Match(child, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar)
+ | ExprKind::Index(child, _)
+ if child.hir_id == e.hir_id =>
+ {
+ Some(Position::Postfix)
+ },
+ _ if child_id == e.hir_id => {
+ precedence = parent.precedence().order();
+ None
+ },
+ _ => None,
+ },
+ _ => None,
+ }
+ })
+ .unwrap_or(Position::Other(precedence));
+ (position, adjustments)
+}
+
+fn is_union<'tcx>(typeck: &'tcx TypeckResults<'_>, path_expr: &'tcx Expr<'_>) -> bool {
+ typeck
+ .expr_ty_adjusted(path_expr)
+ .ty_adt_def()
+ .map_or(false, rustc_middle::ty::AdtDef::is_union)
+}
+
+fn closure_result_position<'tcx>(
+ cx: &LateContext<'tcx>,
+ closure: &'tcx Closure<'_>,
+ ty: Ty<'tcx>,
+ precedence: i8,
+) -> Position {
+ match closure.fn_decl.output {
+ FnRetTy::Return(hir_ty) => {
+ if let Some(sig) = ty_sig(cx, ty)
+ && let Some(output) = sig.output()
+ {
+ binding_ty_auto_deref_stability(cx, hir_ty, precedence, output.bound_vars())
+ } else {
+ Position::Other(precedence)
+ }
+ },
+ FnRetTy::DefaultReturn(_) => Position::Other(precedence),
+ }
+}
+
+// Checks the stability of auto-deref 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 binding_ty_auto_deref_stability<'tcx>(
+ cx: &LateContext<'tcx>,
+ ty: &'tcx hir::Ty<'_>,
+ precedence: i8,
+ binder_args: &'tcx List<BoundVariableKind>,
+) -> Position {
+ let TyKind::Rptr(_, ty) = &ty.kind else {
+ return Position::Other(precedence);
+ };
+ let mut ty = ty;
- match iter.next().map(|(_, x)| x) {
- Some(Node::Block(_)) => {
- if let Some((_, Node::Expr(e))) = iter.next() {
- prev = e;
+ loop {
+ break match ty.ty.kind {
+ TyKind::Rptr(_, 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 {
+ GenericArg::Infer(_) => true,
+ GenericArg::Type(ty) => ty_contains_infer(ty),
+ _ => false,
+ })
+ {
+ Position::ReborrowStable(precedence)
} else {
- // This shouldn't happen. Blocks are always contained in an expression.
- break &[];
+ Position::DerefStable(
+ precedence,
+ cx.tcx
+ .erase_late_bound_regions(Binder::bind_with_vars(
+ cx.typeck_results().node_type(ty.ty.hir_id),
+ binder_args,
+ ))
+ .is_sized(cx.tcx, cx.param_env.without_caller_bounds()),
+ )
}
},
- Some(Node::Expr(&Expr {
- kind: ExprKind::Break(Destination { target_id: Ok(id), .. }, _),
- ..
- })) => {
- if let Some(Node::Expr(e)) = map.find(id) {
- prev = e;
- iter = map.parent_iter(id);
- } else {
- // This shouldn't happen. The destination should exist.
- break &[];
+ TyKind::Slice(_) => Position::DerefStable(precedence, false),
+ TyKind::Array(..) | TyKind::Ptr(_) | TyKind::BareFn(_) => Position::DerefStable(precedence, true),
+ TyKind::Never
+ | TyKind::Tup(_)
+ | TyKind::Path(_) => Position::DerefStable(
+ precedence,
+ cx.tcx
+ .erase_late_bound_regions(Binder::bind_with_vars(
+ cx.typeck_results().node_type(ty.ty.hir_id),
+ binder_args,
+ ))
+ .is_sized(cx.tcx, cx.param_env.without_caller_bounds()),
+ ),
+ TyKind::OpaqueDef(..) | TyKind::Infer | TyKind::Typeof(..) | TyKind::TraitObject(..) | TyKind::Err => {
+ Position::ReborrowStable(precedence)
+ },
+ };
+ }
+}
+
+// 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: &GenericArg<'_>) {
+ if self.0 || matches!(arg, GenericArg::Infer(_)) {
+ self.0 = true;
+ } else if let GenericArg::Type(ty) = arg {
+ self.visit_ty(ty);
+ }
+ }
+ }
+ let mut v = V(false);
+ v.visit_ty(ty);
+ v.0
+}
+
+fn call_is_qualified(expr: &Expr<'_>) -> bool {
+ if let ExprKind::Path(path) = &expr.kind {
+ match path {
+ QPath::Resolved(_, path) => path.segments.last().map_or(false, |segment| segment.args.is_some()),
+ QPath::TypeRelative(_, segment) => segment.args.is_some(),
+ QPath::LangItem(..) => false,
+ }
+ } else {
+ false
+ }
+}
+
+// Checks whether:
+// * child is an expression of the form `&e` in an argument position requiring an `impl Trait`
+// * `e`'s type implements `Trait` and is copyable
+// If the conditions are met, returns `Some(Position::ImplArg(..))`; otherwise, returns `None`.
+// The "is copyable" condition is to avoid the case where removing the `&` means `e` would have to
+// be moved, but it cannot be.
+#[expect(clippy::too_many_arguments, clippy::too_many_lines)]
+fn needless_borrow_impl_arg_position<'tcx>(
+ cx: &LateContext<'tcx>,
+ possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
+ parent: &Expr<'tcx>,
+ arg_index: usize,
+ param_ty: ParamTy,
+ mut expr: &Expr<'tcx>,
+ precedence: i8,
+ msrv: Option<RustcVersion>,
+) -> Position {
+ let destruct_trait_def_id = cx.tcx.lang_items().destruct_trait();
+ let sized_trait_def_id = cx.tcx.lang_items().sized_trait();
+
+ let Some(callee_def_id) = fn_def_id(cx, parent) else { return Position::Other(precedence) };
+ let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
+ let substs_with_expr_ty = cx
+ .typeck_results()
+ .node_substs(if let ExprKind::Call(callee, _) = parent.kind {
+ callee.hir_id
+ } else {
+ parent.hir_id
+ });
+
+ let predicates = cx.tcx.param_env(callee_def_id).caller_bounds();
+ let projection_predicates = predicates
+ .iter()
+ .filter_map(|predicate| {
+ if let PredicateKind::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 PredicateKind::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 Position::Other(precedence);
+ }
+
+ // 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, callee_def_id, projection_predicate))
+ {
+ return Position::Other(precedence);
+ }
+
+ // `substs_with_referent_ty` can be constructed outside of `check_referent` because the same
+ // elements are modified each time `check_referent` is called.
+ let mut substs_with_referent_ty = substs_with_expr_ty.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 substs_with_referent_ty,
+ ) {
+ return false;
+ }
+
+ predicates.iter().all(|predicate| {
+ if let PredicateKind::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) = substs_with_referent_ty[param_ty.index as usize].unpack()
+ && ty.is_array()
+ && !meets_msrv(msrv, msrvs::ARRAY_INTO_ITERATOR)
+ {
+ return false;
+ }
+
+ let predicate = EarlyBinder(predicate).subst(cx.tcx, &substs_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 needless_borrow = false;
+ while let ExprKind::AddrOf(_, _, referent) = expr.kind {
+ if !check_reference_and_referent(expr, referent) {
+ break;
+ }
+ expr = referent;
+ needless_borrow = true;
+ }
+
+ if needless_borrow {
+ Position::ImplArg(expr.hir_id)
+ } else {
+ Position::Other(precedence)
+ }
+}
+
+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).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::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 {
+ let mir = enclosing_mir(cx.tcx, reference.hir_id);
+ if 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.has_deref()
+ // 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 `substs`, 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>],
+ substs: &mut [ty::GenericArg<'tcx>],
+) -> bool {
+ let mut replaced = BitSet::new_empty(substs.len());
+
+ let mut deque = VecDeque::with_capacity(substs.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;
+ }
+
+ substs[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 item_def_id = projection_predicate.projection_ty.item_def_id;
+ let assoc_item = cx.tcx.associated_item(item_def_id);
+ let projection = cx.tcx
+ .mk_projection(assoc_item.def_id, cx.tcx.mk_substs_trait(new_ty, []));
+
+ if let Ok(projected_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, projection)
+ && substs[term_param_ty.index as usize] != ty::GenericArg::from(projected_ty)
+ {
+ deque.push_back((*term_param_ty, projected_ty));
+ }
}
+ }
+ }
+ }
+
+ true
+}
+
+struct TyPosition<'tcx> {
+ position: Position,
+ ty: Option<Ty<'tcx>>,
+}
+impl From<Position> for TyPosition<'_> {
+ fn from(position: Position) -> Self {
+ Self { position, ty: None }
+ }
+}
+impl<'tcx> TyPosition<'tcx> {
+ fn new_deref_stable_for_result(precedence: i8, ty: Ty<'tcx>) -> Self {
+ Self {
+ position: Position::ReborrowStable(precedence),
+ ty: Some(ty),
+ }
+ }
+ fn position_for_result(self, cx: &LateContext<'tcx>) -> Position {
+ match (self.position, self.ty) {
+ (Position::ReborrowStable(precedence), Some(ty)) => {
+ Position::DerefStable(precedence, ty.is_sized(cx.tcx, cx.param_env))
},
- _ => break &[],
+ (position, _) => position,
}
}
+ fn position_for_arg(self) -> Position {
+ self.position
+ }
}
-#[allow(clippy::needless_pass_by_value)]
-fn report(cx: &LateContext<'_>, expr: &Expr<'_>, state: State, data: StateData) {
+// Checks whether a type is stable when switching to auto dereferencing,
+fn ty_auto_deref_stability<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, precedence: i8) -> TyPosition<'tcx> {
+ let ty::Ref(_, mut ty, _) = *ty.kind() else {
+ return Position::Other(precedence).into();
+ };
+
+ loop {
+ break match *ty.kind() {
+ ty::Ref(_, ref_ty, _) => {
+ ty = ref_ty;
+ continue;
+ },
+ ty::Param(_) => TyPosition::new_deref_stable_for_result(precedence, ty),
+ ty::Projection(_) if ty.has_non_region_param() => TyPosition::new_deref_stable_for_result(precedence, ty),
+ ty::Infer(_) | ty::Error(_) | ty::Bound(..) | ty::Opaque(..) | ty::Placeholder(_) | ty::Dynamic(..) => {
+ Position::ReborrowStable(precedence).into()
+ },
+ ty::Adt(..) if ty.has_placeholders() || ty.has_opaque_types() => {
+ Position::ReborrowStable(precedence).into()
+ },
+ ty::Adt(_, substs) if substs.has_non_region_param() => {
+ TyPosition::new_deref_stable_for_result(precedence, ty)
+ },
+ ty::Bool
+ | ty::Char
+ | ty::Int(_)
+ | ty::Uint(_)
+ | ty::Array(..)
+ | ty::Float(_)
+ | ty::RawPtr(..)
+ | ty::FnPtr(_) => Position::DerefStable(precedence, true).into(),
+ ty::Str | ty::Slice(..) => Position::DerefStable(precedence, false).into(),
+ ty::Adt(..)
+ | ty::Foreign(_)
+ | ty::FnDef(..)
+ | ty::Generator(..)
+ | ty::GeneratorWitness(..)
+ | ty::Closure(..)
+ | ty::Never
+ | ty::Tuple(_)
+ | ty::Projection(_) => {
+ Position::DerefStable(precedence, ty.is_sized(cx.tcx, cx.param_env.without_caller_bounds())).into()
+ },
+ };
+ }
+}
+
+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) {
match state {
State::DerefMethod {
ty_changed_count,
is_final_ufcs,
+ target_mut,
} => {
let mut app = Applicability::MachineApplicable;
let (expr_str, expr_is_macro_call) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app);
};
let addr_of_str = if ty_changed_count < ref_count {
// Check if a reborrow from &mut T -> &T is required.
- if data.target_mut == Mutability::Not && matches!(ty.kind(), ty::Ref(_, _, Mutability::Mut)) {
+ if target_mut == Mutability::Not && matches!(ty.kind(), ty::Ref(_, _, Mutability::Mut)) {
"&*"
} else {
""
}
- } else if data.target_mut == Mutability::Mut {
+ } else if target_mut == Mutability::Mut {
"&mut "
} else {
"&"
};
let expr_str = if !expr_is_macro_call && is_final_ufcs && expr.precedence().order() < PREC_PREFIX {
- format!("({})", expr_str)
+ format!("({expr_str})")
} else {
expr_str.into_owned()
};
cx,
EXPLICIT_DEREF_METHODS,
data.span,
- match data.target_mut {
+ match target_mut {
Mutability::Not => "explicit `deref` method call",
Mutability::Mut => "explicit `deref_mut` method call",
},
"try this",
- format!("{}{}{}", addr_of_str, deref_str, expr_str),
+ format!("{addr_of_str}{deref_str}{expr_str}"),
app,
);
},
- State::DerefedBorrow { .. } => {
+ State::DerefedBorrow(state) => {
let mut app = Applicability::MachineApplicable;
- let snip = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app).0;
- span_lint_and_sugg(
+ let snip_expr = state.snip_expr.map_or(expr, |hir_id| cx.tcx.hir().expect_expr(hir_id));
+ let (snip, snip_is_macro) = snippet_with_context(cx, snip_expr.span, data.span.ctxt(), "..", &mut app);
+ span_lint_hir_and_then(cx, NEEDLESS_BORROW, data.hir_id, data.span, state.msg, |diag| {
+ let calls_field = matches!(expr.kind, ExprKind::Field(..)) && matches!(data.position, Position::Callee);
+ let sugg = if !snip_is_macro
+ && !has_enclosing_paren(&snip)
+ && (expr.precedence().order() < data.position.precedence() || calls_field)
+ {
+ 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(..)
+ ) && matches!(data.position, Position::DerefStable(_, true))
+ {
+ // 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, 0)
+ } else {
+ ("", data.position.precedence())
+ };
+ span_lint_hir_and_then(
cx,
- NEEDLESS_BORROW,
+ EXPLICIT_AUTO_DEREF,
+ data.hir_id,
data.span,
- &format!(
- "this expression borrows a reference (`{}`) that is immediately dereferenced by the compiler",
- cx.typeck_results().expr_ty(expr),
- ),
- "change this to",
- snip.into(),
- app,
+ "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 this", sugg, app);
+ },
+ );
+ },
+ State::ExplicitDerefField { .. } => {
+ if matches!(
+ expr.kind,
+ ExprKind::Block(..)
+ | ExprKind::ConstBlock(_)
+ | ExprKind::If(..)
+ | ExprKind::Loop(..)
+ | ExprKind::Match(..)
+ ) && matches!(data.position, Position::DerefStable(_, true))
+ {
+ // 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 this", snip.into_owned(), app);
+ },
);
},
+ State::Borrow { .. } | State::Reborrow { .. } => (),
}
}
-impl Dereferencing {
- fn check_local_usage(&mut self, cx: &LateContext<'_>, e: &Expr<'_>, local: HirId) {
+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
} 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)));
+ 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)));
+ 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
projects / rust.git / blobdiff