+ ExprKind::AddrOf(BorrowKind::Ref, _, sub_expr) => return Some((RefOp::AddrOf, sub_expr)),
+ _ => return None,
+ };
+ if tcx.is_diagnostic_item(sym::deref_method, def_id) {
+ Some((RefOp::Method(Mutability::Not), arg))
+ } else if tcx.trait_of_item(def_id)? == tcx.lang_items().deref_mut_trait()? {
+ Some((RefOp::Method(Mutability::Mut), 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(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),
+
+ // 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,
+ }
+}
+
+// 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::LlvmInlineAsm(..)
+ | ExprKind::Struct(..)
+ | ExprKind::Repeat(..)
+ | ExprKind::Yield(..) => true,
+ }
+}
+
+#[allow(clippy::needless_pass_by_value)]
+fn report(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data: StateData) {
+ match state {
+ State::DerefMethod {
+ ty_changed_count,
+ is_final_ufcs,
+ } => {
+ 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 data.target_mut == Mutability::Not && matches!(ty.kind(), ty::Ref(_, _, Mutability::Mut)) {
+ "&*"
+ } else {
+ ""
+ }
+ } else if data.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)
+ } else {
+ expr_str.into_owned()
+ };
+
+ span_lint_and_sugg(
+ cx,
+ EXPLICIT_DEREF_METHODS,
+ data.span,
+ match data.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),
+ app,
+ );