Auto merge of #8355 - Jarcho:explicit_auto_deref_2, r=flip1995

Add lint `explicit_auto_deref` take 2

fixes: #234
fixes: #8367
fixes: #8380

Still things to do:

* ~~This currently only lints `&*<expr>` when it doesn't trigger `needless_borrow`.~~
* ~~This requires a borrow after a deref to trigger. So `*<expr>` changing `&&T` to `&T` won't be caught.~~
* The `deref` and `deref_mut` trait methods aren't linted.
* Neither ~~field accesses~~, nor method receivers are linted.
* ~~This probably shouldn't lint reborrowing.~~
* Full slicing to deref should probably be handled here as well. e.g. `&vec[..]` when just `&vec` would do

changelog: new lint `explicit_auto_deref`

33 files changed, 1560 insertions, 273 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc50ff3a44a..9bc93c1cb42 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3400,6 +3400,7 @@ Released 2018-09-13
 [`expect_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_fun_call
 [`expect_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_used
 [`expl_impl_clone_on_copy`]: https://rust-lang.github.io/rust-clippy/master/index.html#expl_impl_clone_on_copy
+[`explicit_auto_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_auto_deref
 [`explicit_counter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_counter_loop
 [`explicit_deref_methods`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_deref_methods
 [`explicit_into_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_into_iter_loop
diff --git a/clippy_dev/src/update_lints.rs b/clippy_dev/src/update_lints.rs
index 115f5f0064f..2e0659f42d7 100644
--- a/clippy_dev/src/update_lints.rs
+++ b/clippy_dev/src/update_lints.rs
@@ -413,7 +413,7 @@ fn remove_lint_declaration(name: &str, path: &Path, lints: &mut Vec<Lint>) -> io
                 .find("declare_lint_pass!")
                 .unwrap_or_else(|| panic!("failed to find `impl_lint_pass`"))
         });
-        let mut impl_lint_pass_end = (&content[impl_lint_pass_start..])
+        let mut impl_lint_pass_end = content[impl_lint_pass_start..]
             .find(']')
             .expect("failed to find `impl_lint_pass` terminator");
 
diff --git a/clippy_lints/src/dereference.rs b/clippy_lints/src/dereference.rs
index b47441eff37..59dcc1ebf19 100644
--- a/clippy_lints/src/dereference.rs
+++ b/clippy_lints/src/dereference.rs
@@ -1,20 +1,24 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::has_enclosing_paren;
-use clippy_utils::ty::peel_mid_ty_refs;
-use clippy_utils::{get_parent_expr, get_parent_node, is_lint_allowed, path_to_local};
+use clippy_utils::ty::{expr_sig, peel_mid_ty_refs, variant_of_res};
+use clippy_utils::{get_parent_expr, is_lint_allowed, path_to_local, walk_to_expr_usage};
 use rustc_ast::util::parser::{PREC_POSTFIX, PREC_PREFIX};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::Applicability;
+use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{
-    BindingAnnotation, Body, BodyId, BorrowKind, Destination, Expr, ExprKind, HirId, MatchSource, Mutability, Node,
-    Pat, PatKind, UnOp,
+    self as hir, BindingAnnotation, Body, BodyId, BorrowKind, Expr, ExprKind, GenericArg, HirId, ImplItem,
+    ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind, Path, QPath, TraitItem,
+    TraitItemKind, TyKind, UnOp,
 };
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeckResults};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeckResults};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::{symbol::sym, Span};
+use rustc_span::{symbol::sym, Span, Symbol};
+use rustc_trait_selection::infer::InferCtxtExt;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -104,10 +108,34 @@ declare_clippy_lint! {
     "`ref` binding to a reference"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for dereferencing expressions which would be covered by auto-deref.
+    ///
+    /// ### Why is this bad?
+    /// This unnecessarily complicates the code.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let x = String::new();
+    /// let y: &str = &*x;
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// let x = String::new();
+    /// let y: &str = &x;
+    /// ```
+    #[clippy::version = "1.60.0"]
+    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)]
@@ -136,6 +164,12 @@ struct StateData {
     /// Span of the top level expression
     span: Span,
     hir_id: HirId,
+    position: Position,
+}
+
+struct DerefedBorrow {
+    count: usize,
+    msg: &'static str,
 }
 
 enum State {
@@ -147,11 +181,19 @@ enum State {
         /// The required mutability
         target_mut: Mutability,
     },
-    DerefedBorrow {
-        count: usize,
-        required_precedence: i8,
-        msg: &'static str,
+    DerefedBorrow(DerefedBorrow),
+    ExplicitDeref {
+        // Span and id of the top-level deref expression if the parent expression is a borrow.
+        deref_span_id: Option<(Span, HirId)>,
+    },
+    ExplicitDerefField {
+        name: Symbol,
     },
+    Reborrow {
+        deref_span: Span,
+        deref_hir_id: HirId,
+    },
+    Borrow,
 }
 
 // A reference operation considered by this lint pass
@@ -207,13 +249,28 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
 
         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, expr);
 
                 match kind {
+                    RefOp::Deref => {
+                        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 { deref_span_id: 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() =>
                     {
                         self.state = Some((
                             State::DerefMethod {
@@ -228,12 +285,13 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
                             StateData {
                                 span: expr.span,
                                 hir_id: expr.hir_id,
+                                position
                             },
                         ));
                     },
                     RefOp::AddrOf => {
                         // Find the number of times the borrow is auto-derefed.
-                        let mut iter = find_adjustments(cx.tcx, typeck, expr).iter();
+                        let mut iter = adjustments.iter();
                         let mut deref_count = 0usize;
                         let next_adjust = loop {
                             match iter.next() {
@@ -274,40 +332,43 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
                             "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 (required_refs, required_precedence, msg) = if is_auto_borrow_position(parent, expr.hir_id)
-                        {
-                            (1, PREC_POSTFIX, if deref_count == 1 { borrow_msg } else { deref_msg })
+                        let (required_refs, msg) = if position.can_auto_borrow() {
+                            (1, if deref_count == 1 { borrow_msg } else { deref_msg })
                         } else if let Some(&Adjust::Borrow(AutoBorrow::Ref(_, mutability))) =
                             next_adjust.map(|a| &a.kind)
                         {
-                            if matches!(mutability, AutoBorrowMutability::Mut { .. })
-                                && !is_auto_reborrow_position(parent)
+                            if matches!(mutability, AutoBorrowMutability::Mut { .. }) && !position.is_reborrow_stable()
                             {
-                                (3, 0, deref_msg)
+                                (3, deref_msg)
                             } else {
-                                (2, 0, deref_msg)
+                                (2, deref_msg)
                             }
                         } else {
-                            (2, 0, deref_msg)
+                            (2, deref_msg)
                         };
 
                         if deref_count >= required_refs {
                             self.state = Some((
-                                State::DerefedBorrow {
+                                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,
-                                    required_precedence,
                                     msg,
-                                },
+                                }),
+                                StateData { span: expr.span, hir_id: expr.hir_id, position },
+                            ));
+                        } else if position.is_deref_stable() {
+                            self.state = Some((
+                                State::Borrow,
                                 StateData {
                                     span: expr.span,
                                     hir_id: expr.hir_id,
+                                    position
                                 },
                             ));
                         }
                     },
-                    _ => (),
+                    RefOp::Method(..) => (),
                 }
             },
             (
@@ -334,26 +395,90 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
                     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) => {
+                let position = data.position;
+                report(cx, expr, State::DerefedBorrow(state), data);
+                if position.is_deref_stable() {
+                    self.state = Some((
+                        State::Borrow,
+                        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 { deref_span_id: None },
+                        StateData { span: expr.span, hir_id: expr.hir_id, position },
+                    ));
+                }
+            },
+
+            (Some((State::Borrow, data)), RefOp::Deref) => {
+                if typeck.expr_ty(sub_expr).is_ref() {
+                    self.state = Some((
+                        State::Reborrow {
+                            deref_span: expr.span,
+                            deref_hir_id: expr.hir_id,
+                        },
+                        data,
+                    ));
+                } else {
+                    self.state = Some((
+                        State::ExplicitDeref {
+                            deref_span_id: Some((expr.span, expr.hir_id)),
+                        },
+                        data,
+                    ));
+                }
+            },
             (
                 Some((
-                    State::DerefedBorrow {
-                        count,
-                        required_precedence,
-                        msg,
+                    State::Reborrow {
+                        deref_span,
+                        deref_hir_id,
                     },
                     data,
                 )),
-                RefOp::AddrOf,
-            ) if count != 0 => {
+                RefOp::Deref,
+            ) => {
                 self.state = Some((
-                    State::DerefedBorrow {
-                        count: count - 1,
-                        required_precedence,
-                        msg,
+                    State::ExplicitDeref {
+                        deref_span_id: Some((deref_span, deref_hir_id)),
                     },
                     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),
         }
@@ -473,131 +598,362 @@ fn deref_method_same_type<'tcx>(result_ty: Ty<'tcx>, arg_ty: Ty<'tcx>) -> bool {
     }
 }
 
-// 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)]
+enum Position {
+    MethodReceiver,
+    /// The method is defined on a reference type. e.g. `impl Foo for &T`
+    MethodReceiverRefImpl,
+    Callee,
+    FieldAccess(Symbol),
+    Postfix,
+    Deref,
+    /// Any other location which will trigger auto-deref to a specific time.
+    DerefStable(i8),
+    /// Any other location which will trigger auto-reborrowing.
+    ReborrowStable(i8),
+    Other(i8),
 }
+impl Position {
+    fn is_deref_stable(self) -> bool {
+        matches!(self, Self::DerefStable(_))
+    }
 
-/// Checks if the given expression is in a position which can be auto-reborrowed.
-/// Note: This is only correct assuming auto-deref is already occurring.
-fn is_auto_reborrow_position(parent: Option<Node<'_>>) -> bool {
-    match parent {
-        Some(Node::Expr(parent)) => matches!(parent.kind, ExprKind::MethodCall(..) | ExprKind::Call(..)),
-        Some(Node::Local(_)) => true,
-        _ => false,
+    fn is_reborrow_stable(self) -> bool {
+        matches!(self, Self::DerefStable(_) | Self::ReborrowStable(_))
     }
-}
 
-/// Checks if the given expression is a position which can auto-borrow.
-fn is_auto_borrow_position(parent: Option<Node<'_>>, child_id: HirId) -> bool {
-    if let Some(Node::Expr(parent)) = parent {
-        match parent.kind {
-            // ExprKind::MethodCall(_, [self_arg, ..], _) => self_arg.hir_id == child_id,
-            ExprKind::Field(..) => true,
-            ExprKind::Call(f, _) => f.hir_id == child_id,
-            _ => false,
-        }
-    } else {
-        false
+    fn can_auto_borrow(self) -> bool {
+        matches!(self, Self::MethodReceiver | Self::FieldAccess(_) | Self::Callee)
     }
-}
 
-/// Adjustments are sometimes made in the parent block rather than the expression itself.
-fn find_adjustments<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    typeck: &'tcx TypeckResults<'tcx>,
-    expr: &'tcx Expr<'tcx>,
-) -> &'tcx [Adjustment<'tcx>] {
-    let map = tcx.hir();
-    let mut iter = map.parent_iter(expr.hir_id);
-    let mut prev = expr;
+    fn lint_explicit_deref(self) -> bool {
+        matches!(self, Self::Other(_) | Self::DerefStable(_) | Self::ReborrowStable(_))
+    }
 
-    loop {
-        match typeck.expr_adjustments(prev) {
-            [] => (),
-            a => break a,
-        };
+    fn precedence(self) -> i8 {
+        match self {
+            Self::MethodReceiver
+            | Self::MethodReceiverRefImpl
+            | Self::Callee
+            | Self::FieldAccess(_)
+            | Self::Postfix => PREC_POSTFIX,
+            Self::Deref => PREC_PREFIX,
+            Self::DerefStable(p) | Self::ReborrowStable(p) | Self::Other(p) => p,
+        }
+    }
+}
 
-        match iter.next().map(|(_, x)| x) {
-            Some(Node::Block(_)) => {
-                if let Some((_, Node::Expr(e))) = iter.next() {
-                    prev = e;
+/// 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.
+#[allow(clippy::too_many_lines)]
+fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (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(ty, precedence))
+            },
+            Node::Item(&Item {
+                kind: ItemKind::Static(..) | ItemKind::Const(..),
+                def_id,
+                span,
+                ..
+            })
+            | Node::TraitItem(&TraitItem {
+                kind: TraitItemKind::Const(..),
+                def_id,
+                span,
+                ..
+            })
+            | Node::ImplItem(&ImplItem {
+                kind: ImplItemKind::Const(..),
+                def_id,
+                span,
+                ..
+            }) if span.ctxt() == ctxt => {
+                let ty = cx.tcx.type_of(def_id);
+                Some(if ty.is_ref() {
+                    Position::DerefStable(precedence)
                 } else {
-                    // This shouldn't happen. Blocks are always contained in an expression.
-                    break &[];
-                }
+                    Position::Other(precedence)
+                })
             },
-            Some(Node::Expr(&Expr {
-                kind: ExprKind::Break(Destination { target_id: Ok(id), .. }, _),
+
+            Node::Item(&Item {
+                kind: ItemKind::Fn(..),
+                def_id,
+                span,
+                ..
+            })
+            | Node::TraitItem(&TraitItem {
+                kind: TraitItemKind::Fn(..),
+                def_id,
+                span,
+                ..
+            })
+            | Node::ImplItem(&ImplItem {
+                kind: ImplItemKind::Fn(..),
+                def_id,
+                span,
                 ..
-            })) => {
-                if let Some(Node::Expr(e)) = map.find(id) {
-                    prev = e;
-                    iter = map.parent_iter(id);
+            }) if span.ctxt() == ctxt => {
+                let output = cx.tcx.fn_sig(def_id.to_def_id()).skip_binder().output();
+                Some(if !output.is_ref() {
+                    Position::Other(precedence)
+                } else if output.has_placeholders() || output.has_opaque_types() {
+                    Position::ReborrowStable(precedence)
+                } else {
+                    Position::DerefStable(precedence)
+                })
+            },
+
+            Node::Expr(parent) if parent.span.ctxt() == ctxt => match parent.kind {
+                ExprKind::Ret(_) => {
+                    let output = cx
+                        .tcx
+                        .fn_sig(cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()))
+                        .skip_binder()
+                        .output();
+                    Some(if !output.is_ref() {
+                        Position::Other(precedence)
+                    } else if output.has_placeholders() || output.has_opaque_types() {
+                        Position::ReborrowStable(precedence)
+                    } else {
+                        Position::DerefStable(precedence)
+                    })
+                },
+                ExprKind::Call(func, _) if func.hir_id == child_id => (child_id == e.hir_id).then(|| 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(ty) => binding_ty_auto_deref_stability(ty, precedence),
+                        None => param_auto_deref_stability(ty.skip_binder(), precedence),
+                    }),
+                ExprKind::MethodCall(_, args, _) => {
+                    let id = cx.typeck_results().type_dependent_def_id(parent.hir_id).unwrap();
+                    args.iter().position(|arg| arg.hir_id == child_id).map(|i| {
+                        if i == 0 {
+                            // 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 {
+                                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(child_id).unwrap_or_else(
+                                    || cx.tcx.mk_substs([].iter())
+                                ) && 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()
+                                && cx.tcx.infer_ctxt().enter(|infcx|
+                                    infcx
+                                        .type_implements_trait(trait_id, impl_ty, subs, cx.param_env)
+                                        .must_apply_modulo_regions()
+                                )
+                            {
+                                Position::MethodReceiverRefImpl
+                            } else {
+                                Position::MethodReceiver
+                            }
+                        } else {
+                            param_auto_deref_stability(cx.tcx.fn_sig(id).skip_binder().inputs()[i], precedence)
+                        }
+                    })
+                },
+                ExprKind::Struct(path, fields, _) => {
+                    let variant = variant_of_res(cx, cx.qpath_res(path, parent.hir_id));
+                    fields
+                        .iter()
+                        .find(|f| f.expr.hir_id == child_id)
+                        .zip(variant)
+                        .and_then(|(field, variant)| variant.fields.iter().find(|f| f.name == field.ident.name))
+                        .map(|field| param_auto_deref_stability(cx.tcx.type_of(field.did), precedence))
+                },
+                ExprKind::Field(child, name) if child.hir_id == e.hir_id => Some(Position::FieldAccess(name.name)),
+                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)
+}
+
+// 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(ty: &hir::Ty<'_>, precedence: i8) -> Position {
+    let TyKind::Rptr(_, ty) = &ty.kind else {
+        return Position::Other(precedence);
+    };
+    let mut ty = ty;
+
+    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. The destination should exist.
-                    break &[];
+                    Position::DerefStable(precedence)
                 }
             },
-            _ => break &[],
+            TyKind::Slice(_)
+            | TyKind::Array(..)
+            | TyKind::BareFn(_)
+            | TyKind::Never
+            | TyKind::Tup(_)
+            | TyKind::Ptr(_)
+            | TyKind::TraitObject(..)
+            | TyKind::Path(_) => Position::DerefStable(precedence),
+            TyKind::OpaqueDef(..)
+            | TyKind::Infer
+            | TyKind::Typeof(..)
+            | 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
+}
+
+// Checks whether a type is stable when switching to auto dereferencing,
+fn param_auto_deref_stability(ty: Ty<'_>, precedence: i8) -> Position {
+    let ty::Ref(_, mut ty, _) = *ty.kind() else {
+        return Position::Other(precedence);
+    };
+
+    loop {
+        break match *ty.kind() {
+            ty::Ref(_, ref_ty, _) => {
+                ty = ref_ty;
+                continue;
+            },
+            ty::Infer(_)
+            | ty::Error(_)
+            | ty::Param(_)
+            | ty::Bound(..)
+            | ty::Opaque(..)
+            | ty::Placeholder(_)
+            | ty::Dynamic(..) => Position::ReborrowStable(precedence),
+            ty::Adt(..) if ty.has_placeholders() || ty.has_param_types_or_consts() => {
+                Position::ReborrowStable(precedence)
+            },
+            ty::Adt(..)
+            | ty::Bool
+            | ty::Char
+            | ty::Int(_)
+            | ty::Uint(_)
+            | ty::Float(_)
+            | ty::Foreign(_)
+            | ty::Str
+            | ty::Array(..)
+            | ty::Slice(..)
+            | ty::RawPtr(..)
+            | ty::FnDef(..)
+            | ty::FnPtr(_)
+            | ty::Closure(..)
+            | ty::Generator(..)
+            | ty::GeneratorWitness(..)
+            | ty::Never
+            | ty::Tuple(_)
+            | ty::Projection(_) => Position::DerefStable(precedence),
+        };
+    }
+}
+
+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)]
-fn report<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, state: State, data: StateData) {
+#[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,
@@ -647,15 +1003,14 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, state: State, data: S
                 app,
             );
         },
-        State::DerefedBorrow {
-            required_precedence,
-            msg,
-            ..
-        } => {
+        State::DerefedBorrow(state) => {
             let mut app = Applicability::MachineApplicable;
-            let snip = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app).0;
-            span_lint_hir_and_then(cx, NEEDLESS_BORROW, data.hir_id, data.span, msg, |diag| {
-                let sugg = if required_precedence > expr.precedence().order() && !has_enclosing_paren(&snip) {
+            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 sugg = if !snip_is_macro
+                    && expr.precedence().order() < data.position.precedence()
+                    && !has_enclosing_paren(&snip)
+                {
                     format!("({})", snip)
                 } else {
                     snip.into()
@@ -663,6 +1018,48 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, state: State, data: S
                 diag.span_suggestion(data.span, "change this to", sugg, app);
             });
         },
+        State::ExplicitDeref { deref_span_id } => {
+            let (span, hir_id, precedence) = if let Some((span, hir_id)) = deref_span_id
+                && !cx.typeck_results().expr_ty(expr).is_ref()
+            {
+                (span, hir_id, PREC_PREFIX)
+            } else {
+                (data.span, data.hir_id, data.position.precedence())
+            };
+            span_lint_hir_and_then(
+                cx,
+                EXPLICIT_AUTO_DEREF,
+                hir_id,
+                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, span.ctxt(), "..", &mut app);
+                    let sugg =
+                        if !snip_is_macro && expr.precedence().order() < precedence && !has_enclosing_paren(&snip) {
+                            format!("({})", snip)
+                        } else {
+                            snip.into()
+                        };
+                    diag.span_suggestion(span, "try this", sugg, app);
+                },
+            );
+        },
+        State::ExplicitDerefField { .. } => {
+            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 { .. } => (),
     }
 }
 
diff --git a/clippy_lints/src/lib.register_all.rs b/clippy_lints/src/lib.register_all.rs
index 27acdd7c726..563ad891603 100644
--- a/clippy_lints/src/lib.register_all.rs
+++ b/clippy_lints/src/lib.register_all.rs
@@ -39,6 +39,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(crate_in_macro_def::CRATE_IN_MACRO_DEF),
     LintId::of(default::FIELD_REASSIGN_WITH_DEFAULT),
     LintId::of(default_instead_of_iter_empty::DEFAULT_INSTEAD_OF_ITER_EMPTY),
+    LintId::of(dereference::EXPLICIT_AUTO_DEREF),
     LintId::of(dereference::NEEDLESS_BORROW),
     LintId::of(derivable_impls::DERIVABLE_IMPLS),
     LintId::of(derive::DERIVE_HASH_XOR_EQ),
diff --git a/clippy_lints/src/lib.register_complexity.rs b/clippy_lints/src/lib.register_complexity.rs
index ed5446f5844..3784d3c68dc 100644
--- a/clippy_lints/src/lib.register_complexity.rs
+++ b/clippy_lints/src/lib.register_complexity.rs
@@ -9,6 +9,7 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec!
     LintId::of(bytes_count_to_len::BYTES_COUNT_TO_LEN),
     LintId::of(casts::CHAR_LIT_AS_U8),
     LintId::of(casts::UNNECESSARY_CAST),
+    LintId::of(dereference::EXPLICIT_AUTO_DEREF),
     LintId::of(derivable_impls::DERIVABLE_IMPLS),
     LintId::of(double_parens::DOUBLE_PARENS),
     LintId::of(explicit_write::EXPLICIT_WRITE),
diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs
index af7226f242f..d3c75f8b519 100644
--- a/clippy_lints/src/lib.register_lints.rs
+++ b/clippy_lints/src/lib.register_lints.rs
@@ -104,6 +104,7 @@ store.register_lints(&[
     default_instead_of_iter_empty::DEFAULT_INSTEAD_OF_ITER_EMPTY,
     default_numeric_fallback::DEFAULT_NUMERIC_FALLBACK,
     default_union_representation::DEFAULT_UNION_REPRESENTATION,
+    dereference::EXPLICIT_AUTO_DEREF,
     dereference::EXPLICIT_DEREF_METHODS,
     dereference::NEEDLESS_BORROW,
     dereference::REF_BINDING_TO_REFERENCE,
diff --git a/clippy_lints/src/matches/match_same_arms.rs b/clippy_lints/src/matches/match_same_arms.rs
index 16fefea5520..15513de7d86 100644
--- a/clippy_lints/src/matches/match_same_arms.rs
+++ b/clippy_lints/src/matches/match_same_arms.rs
@@ -285,7 +285,7 @@ impl<'a> NormalizedPat<'a> {
                 // TODO: Handle negative integers. They're currently treated as a wild match.
                 ExprKind::Lit(lit) => match lit.node {
                     LitKind::Str(sym, _) => Self::LitStr(sym),
-                    LitKind::ByteStr(ref bytes) => Self::LitBytes(&**bytes),
+                    LitKind::ByteStr(ref bytes) => Self::LitBytes(bytes),
                     LitKind::Byte(val) => Self::LitInt(val.into()),
                     LitKind::Char(val) => Self::LitInt(val.into()),
                     LitKind::Int(val, _) => Self::LitInt(val),
diff --git a/clippy_lints/src/matches/match_single_binding.rs b/clippy_lints/src/matches/match_single_binding.rs
index 9df2db45dcf..5ae4a65acaf 100644
--- a/clippy_lints/src/matches/match_single_binding.rs
+++ b/clippy_lints/src/matches/match_single_binding.rs
@@ -55,7 +55,7 @@ pub(crate) fn check<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], e
                         cx,
                         (ex, expr),
                         (bind_names, matched_vars),
-                        &*snippet_body,
+                        &snippet_body,
                         &mut applicability,
                         Some(span),
                     );
@@ -88,7 +88,7 @@ pub(crate) fn check<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], e
                         cx,
                         (ex, expr),
                         (bind_names, matched_vars),
-                        &*snippet_body,
+                        &snippet_body,
                         &mut applicability,
                         None,
                     );
diff --git a/clippy_lints/src/matches/match_str_case_mismatch.rs b/clippy_lints/src/matches/match_str_case_mismatch.rs
index 8302ce426e5..fa3b8d1fcea 100644
--- a/clippy_lints/src/matches/match_str_case_mismatch.rs
+++ b/clippy_lints/src/matches/match_str_case_mismatch.rs
@@ -118,7 +118,7 @@ fn lint(cx: &LateContext<'_>, case_method: &CaseMethod, bad_case_span: Span, bad
         MATCH_STR_CASE_MISMATCH,
         bad_case_span,
         "this `match` arm has a differing case than its expression",
-        &*format!("consider changing the case of this arm to respect `{}`", method_str),
+        &format!("consider changing the case of this arm to respect `{}`", method_str),
         format!("\"{}\"", suggestion),
         Applicability::MachineApplicable,
     );
diff --git a/clippy_lints/src/matches/redundant_pattern_match.rs b/clippy_lints/src/matches/redundant_pattern_match.rs
index 0ea3f3b673b..65cecd333f1 100644
--- a/clippy_lints/src/matches/redundant_pattern_match.rs
+++ b/clippy_lints/src/matches/redundant_pattern_match.rs
@@ -362,9 +362,9 @@ fn find_good_method_for_match<'a>(
         .qpath_res(path_right, arms[1].pat.hir_id)
         .opt_def_id()?;
     let body_node_pair = if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) {
-        (&(*arms[0].body).kind, &(*arms[1].body).kind)
+        (&arms[0].body.kind, &arms[1].body.kind)
     } else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) {
-        (&(*arms[1].body).kind, &(*arms[0].body).kind)
+        (&arms[1].body.kind, &arms[0].body.kind)
     } else {
         return None;
     };
diff --git a/clippy_lints/src/non_expressive_names.rs b/clippy_lints/src/non_expressive_names.rs
index c93b4b2f205..b96af06b8d7 100644
--- a/clippy_lints/src/non_expressive_names.rs
+++ b/clippy_lints/src/non_expressive_names.rs
@@ -326,7 +326,7 @@ impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
         // add the pattern after the expression because the bindings aren't available
         // yet in the init
         // expression
-        SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
+        SimilarNamesNameVisitor(self).visit_pat(&local.pat);
     }
     fn visit_block(&mut self, blk: &'tcx Block) {
         self.single_char_names.push(vec![]);
diff --git a/clippy_lints/src/ptr.rs b/clippy_lints/src/ptr.rs
index b06eba13d2f..5678b8f6ca6 100644
--- a/clippy_lints/src/ptr.rs
+++ b/clippy_lints/src/ptr.rs
@@ -574,14 +574,13 @@ fn check_ptr_arg_usage<'tcx>(cx: &LateContext<'tcx>, body: &'tcx Body<'_>, args:
                 Some((Node::Expr(e), child_id)) => match e.kind {
                     ExprKind::Call(f, expr_args) => {
                         let i = expr_args.iter().position(|arg| arg.hir_id == child_id).unwrap_or(0);
-                        if expr_sig(self.cx, f)
-                            .map(|sig| sig.input(i).skip_binder().peel_refs())
-                            .map_or(true, |ty| match *ty.kind() {
+                        if expr_sig(self.cx, f).and_then(|sig| sig.input(i)).map_or(true, |ty| {
+                            match *ty.skip_binder().peel_refs().kind() {
                                 ty::Param(_) => true,
                                 ty::Adt(def, _) => def.did() == args.ty_did,
                                 _ => false,
-                            })
-                        {
+                            }
+                        }) {
                             // Passed to a function taking the non-dereferenced type.
                             set_skip_flag();
                         }
diff --git a/clippy_lints/src/redundant_static_lifetimes.rs b/clippy_lints/src/redundant_static_lifetimes.rs
index 0825f00f421..f8801f769e8 100644
--- a/clippy_lints/src/redundant_static_lifetimes.rs
+++ b/clippy_lints/src/redundant_static_lifetimes.rs
@@ -87,7 +87,7 @@ impl RedundantStaticLifetimes {
                         _ => {},
                     }
                 }
-                self.visit_type(&*borrow_type.ty, cx, reason);
+                self.visit_type(&borrow_type.ty, cx, reason);
             },
             _ => {},
         }
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 73c1bdd0e3f..a2772edf738 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -2058,6 +2058,21 @@ pub fn peel_hir_expr_refs<'a>(expr: &'a Expr<'a>) -> (&'a Expr<'a>, usize) {
     (e, count)
 }
 
+/// Peels off all references on the type. Returns the underlying type and the number of references
+/// removed.
+pub fn peel_hir_ty_refs<'a>(mut ty: &'a hir::Ty<'a>) -> (&'a hir::Ty<'a>, usize) {
+    let mut count = 0;
+    loop {
+        match &ty.kind {
+            TyKind::Rptr(_, ref_ty) => {
+                ty = ref_ty.ty;
+                count += 1;
+            },
+            _ => break (ty, count),
+        }
+    }
+}
+
 /// Removes `AddrOf` operators (`&`) or deref operators (`*`), but only if a reference type is
 /// dereferenced. An overloaded deref such as `Vec` to slice would not be removed.
 pub fn peel_ref_operators<'hir>(cx: &LateContext<'_>, mut expr: &'hir Expr<'hir>) -> &'hir Expr<'hir> {
@@ -2110,7 +2125,7 @@ fn with_test_item_names<'tcx>(tcx: TyCtxt<'tcx>, module: LocalDefId, f: impl Fn(
                 }
             }
             names.sort_unstable();
-            f(&*entry.insert(names))
+            f(entry.insert(names))
         },
     }
 }
@@ -2168,6 +2183,50 @@ pub fn is_test_module_or_function(tcx: TyCtxt<'_>, item: &Item<'_>) -> bool {
             && item.ident.name.as_str().split('_').any(|a| a == "test" || a == "tests")
 }
 
+/// Walks the HIR tree from the given expression, up to the node where the value produced by the
+/// expression is consumed. Calls the function for every node encountered this way until it returns
+/// `Some`.
+///
+/// This allows walking through `if`, `match`, `break`, block expressions to find where the value
+/// produced by the expression is consumed.
+pub fn walk_to_expr_usage<'tcx, T>(
+    cx: &LateContext<'tcx>,
+    e: &Expr<'tcx>,
+    mut f: impl FnMut(Node<'tcx>, HirId) -> Option<T>,
+) -> Option<T> {
+    let map = cx.tcx.hir();
+    let mut iter = map.parent_iter(e.hir_id);
+    let mut child_id = e.hir_id;
+
+    while let Some((parent_id, parent)) = iter.next() {
+        if let Some(x) = f(parent, child_id) {
+            return Some(x);
+        }
+        let parent = match parent {
+            Node::Expr(e) => e,
+            Node::Block(Block { expr: Some(body), .. }) | Node::Arm(Arm { body, .. }) if body.hir_id == child_id => {
+                child_id = parent_id;
+                continue;
+            },
+            Node::Arm(a) if a.body.hir_id == child_id => {
+                child_id = parent_id;
+                continue;
+            },
+            _ => return None,
+        };
+        match parent.kind {
+            ExprKind::If(child, ..) | ExprKind::Match(child, ..) if child.hir_id != child_id => child_id = parent_id,
+            ExprKind::Break(Destination { target_id: Ok(id), .. }, _) => {
+                child_id = id;
+                iter = map.parent_iter(id);
+            },
+            ExprKind::Block(..) => child_id = parent_id,
+            _ => return None,
+        }
+    }
+    None
+}
+
 macro_rules! op_utils {
     ($($name:ident $assign:ident)*) => {
         /// Binary operation traits like `LangItem::Add`
diff --git a/clippy_utils/src/ty.rs b/clippy_utils/src/ty.rs
index 4c079151f24..6ca36eed4e6 100644
--- a/clippy_utils/src/ty.rs
+++ b/clippy_utils/src/ty.rs
@@ -6,16 +6,16 @@ use core::ops::ControlFlow;
 use rustc_ast::ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
-use rustc_hir::def::{CtorKind, DefKind, Res};
+use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::{Expr, LangItem, TyKind, Unsafety};
+use rustc_hir::{Expr, FnDecl, LangItem, TyKind, Unsafety};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::{ConstValue, Scalar};
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst};
 use rustc_middle::ty::{
-    self, AdtDef, Binder, BoundRegion, FnSig, IntTy, ParamEnv, Predicate, PredicateKind, Region, RegionKind, Ty,
-    TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor, UintTy, VariantDiscr,
+    self, AdtDef, Binder, BoundRegion, DefIdTree, FnSig, IntTy, ParamEnv, Predicate, PredicateKind, ProjectionTy,
+    Region, RegionKind, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor, UintTy, VariantDef, VariantDiscr,
 };
 use rustc_span::symbol::Ident;
 use rustc_span::{sym, Span, Symbol, DUMMY_SP};
@@ -502,16 +502,46 @@ pub fn all_predicates_of(tcx: TyCtxt<'_>, id: DefId) -> impl Iterator<Item = &(P
 #[derive(Clone, Copy)]
 pub enum ExprFnSig<'tcx> {
     Sig(Binder<'tcx, FnSig<'tcx>>),
-    Closure(Binder<'tcx, FnSig<'tcx>>),
+    Closure(Option<&'tcx FnDecl<'tcx>>, Binder<'tcx, FnSig<'tcx>>),
     Trait(Binder<'tcx, Ty<'tcx>>, Option<Binder<'tcx, Ty<'tcx>>>),
 }
 impl<'tcx> ExprFnSig<'tcx> {
-    /// Gets the argument type at the given offset.
-    pub fn input(self, i: usize) -> Binder<'tcx, Ty<'tcx>> {
+    /// Gets the argument type at the given offset. This will return `None` when the index is out of
+    /// bounds only for variadic functions, otherwise this will panic.
+    pub fn input(self, i: usize) -> Option<Binder<'tcx, Ty<'tcx>>> {
         match self {
-            Self::Sig(sig) => sig.input(i),
-            Self::Closure(sig) => sig.input(0).map_bound(|ty| ty.tuple_fields()[i]),
-            Self::Trait(inputs, _) => inputs.map_bound(|ty| ty.tuple_fields()[i]),
+            Self::Sig(sig) => {
+                if sig.c_variadic() {
+                    sig.inputs().map_bound(|inputs| inputs.get(i).copied()).transpose()
+                } else {
+                    Some(sig.input(i))
+                }
+            },
+            Self::Closure(_, sig) => Some(sig.input(0).map_bound(|ty| ty.tuple_fields()[i])),
+            Self::Trait(inputs, _) => Some(inputs.map_bound(|ty| ty.tuple_fields()[i])),
+        }
+    }
+
+    /// Gets the argument type at the given offset. For closures this will also get the type as
+    /// written. This will return `None` when the index is out of bounds only for variadic
+    /// functions, otherwise this will panic.
+    pub fn input_with_hir(self, i: usize) -> Option<(Option<&'tcx hir::Ty<'tcx>>, Binder<'tcx, Ty<'tcx>>)> {
+        match self {
+            Self::Sig(sig) => {
+                if sig.c_variadic() {
+                    sig.inputs()
+                        .map_bound(|inputs| inputs.get(i).copied())
+                        .transpose()
+                        .map(|arg| (None, arg))
+                } else {
+                    Some((None, sig.input(i)))
+                }
+            },
+            Self::Closure(decl, sig) => Some((
+                decl.and_then(|decl| decl.inputs.get(i)),
+                sig.input(0).map_bound(|ty| ty.tuple_fields()[i]),
+            )),
+            Self::Trait(inputs, _) => Some((None, inputs.map_bound(|ty| ty.tuple_fields()[i]))),
         }
     }
 
@@ -519,7 +549,7 @@ impl<'tcx> ExprFnSig<'tcx> {
     /// specified.
     pub fn output(self) -> Option<Binder<'tcx, Ty<'tcx>>> {
         match self {
-            Self::Sig(sig) | Self::Closure(sig) => Some(sig.output()),
+            Self::Sig(sig) | Self::Closure(_, sig) => Some(sig.output()),
             Self::Trait(_, output) => output,
         }
     }
@@ -530,74 +560,123 @@ pub fn expr_sig<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option<ExprFnS
     if let Res::Def(DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::AssocFn, id) = path_res(cx, expr) {
         Some(ExprFnSig::Sig(cx.tcx.fn_sig(id)))
     } else {
-        let ty = cx.typeck_results().expr_ty_adjusted(expr).peel_refs();
-        match *ty.kind() {
-            ty::Closure(_, subs) => Some(ExprFnSig::Closure(subs.as_closure().sig())),
-            ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs))),
-            ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig)),
-            ty::Dynamic(bounds, _) => {
-                let lang_items = cx.tcx.lang_items();
-                match bounds.principal() {
-                    Some(bound)
-                        if Some(bound.def_id()) == lang_items.fn_trait()
-                            || Some(bound.def_id()) == lang_items.fn_once_trait()
-                            || Some(bound.def_id()) == lang_items.fn_mut_trait() =>
-                    {
-                        let output = bounds
-                            .projection_bounds()
-                            .find(|p| lang_items.fn_once_output().map_or(false, |id| id == p.item_def_id()))
-                            .map(|p| p.map_bound(|p| p.term.ty().expect("return type was a const")));
-                        Some(ExprFnSig::Trait(bound.map_bound(|b| b.substs.type_at(0)), output))
-                    },
-                    _ => None,
+        ty_sig(cx, cx.typeck_results().expr_ty_adjusted(expr).peel_refs())
+    }
+}
+
+fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'tcx>> {
+    match *ty.kind() {
+        ty::Closure(id, subs) => {
+            let decl = id
+                .as_local()
+                .and_then(|id| cx.tcx.hir().fn_decl_by_hir_id(cx.tcx.hir().local_def_id_to_hir_id(id)));
+            Some(ExprFnSig::Closure(decl, subs.as_closure().sig()))
+        },
+        ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs))),
+        ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig)),
+        ty::Dynamic(bounds, _) => {
+            let lang_items = cx.tcx.lang_items();
+            match bounds.principal() {
+                Some(bound)
+                    if Some(bound.def_id()) == lang_items.fn_trait()
+                        || Some(bound.def_id()) == lang_items.fn_once_trait()
+                        || Some(bound.def_id()) == lang_items.fn_mut_trait() =>
+                {
+                    let output = bounds
+                        .projection_bounds()
+                        .find(|p| lang_items.fn_once_output().map_or(false, |id| id == p.item_def_id()))
+                        .map(|p| p.map_bound(|p| p.term.ty().unwrap()));
+                    Some(ExprFnSig::Trait(bound.map_bound(|b| b.substs.type_at(0)), output))
+                },
+                _ => None,
+            }
+        },
+        ty::Projection(proj) => match cx.tcx.try_normalize_erasing_regions(cx.param_env, ty) {
+            Ok(normalized_ty) if normalized_ty != ty => ty_sig(cx, normalized_ty),
+            _ => sig_for_projection(cx, proj).or_else(|| sig_from_bounds(cx, ty)),
+        },
+        ty::Param(_) => sig_from_bounds(cx, ty),
+        _ => None,
+    }
+}
+
+fn sig_from_bounds<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'tcx>> {
+    let mut inputs = None;
+    let mut output = None;
+    let lang_items = cx.tcx.lang_items();
+
+    for (pred, _) in all_predicates_of(cx.tcx, cx.typeck_results().hir_owner.to_def_id()) {
+        match pred.kind().skip_binder() {
+            PredicateKind::Trait(p)
+                if (lang_items.fn_trait() == Some(p.def_id())
+                    || lang_items.fn_mut_trait() == Some(p.def_id())
+                    || lang_items.fn_once_trait() == Some(p.def_id()))
+                    && p.self_ty() == ty =>
+            {
+                if inputs.is_some() {
+                    // Multiple different fn trait impls. Is this even allowed?
+                    return None;
                 }
+                inputs = Some(pred.kind().rebind(p.trait_ref.substs.type_at(1)));
             },
-            ty::Param(_) | ty::Projection(..) => {
-                let mut inputs = None;
-                let mut output = None;
-                let lang_items = cx.tcx.lang_items();
-
-                for (pred, _) in all_predicates_of(cx.tcx, cx.typeck_results().hir_owner.to_def_id()) {
-                    let mut is_input = false;
-                    if let Some(ty) = pred
-                        .kind()
-                        .map_bound(|pred| match pred {
-                            PredicateKind::Trait(p)
-                                if (lang_items.fn_trait() == Some(p.def_id())
-                                    || lang_items.fn_mut_trait() == Some(p.def_id())
-                                    || lang_items.fn_once_trait() == Some(p.def_id()))
-                                    && p.self_ty() == ty =>
-                            {
-                                is_input = true;
-                                Some(p.trait_ref.substs.type_at(1))
-                            },
-                            PredicateKind::Projection(p)
-                                if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output()
-                                    && p.projection_ty.self_ty() == ty =>
-                            {
-                                is_input = false;
-                                p.term.ty()
-                            },
-                            _ => None,
-                        })
-                        .transpose()
-                    {
-                        if is_input && inputs.is_none() {
-                            inputs = Some(ty);
-                        } else if !is_input && output.is_none() {
-                            output = Some(ty);
-                        } else {
-                            // Multiple different fn trait impls. Is this even allowed?
-                            return None;
-                        }
-                    }
+            PredicateKind::Projection(p)
+                if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output()
+                    && p.projection_ty.self_ty() == ty =>
+            {
+                if output.is_some() {
+                    // Multiple different fn trait impls. Is this even allowed?
+                    return None;
                 }
+                output = Some(pred.kind().rebind(p.term.ty().unwrap()));
+            },
+            _ => (),
+        }
+    }
+
+    inputs.map(|ty| ExprFnSig::Trait(ty, output))
+}
 
-                inputs.map(|ty| ExprFnSig::Trait(ty, output))
+fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: ProjectionTy<'tcx>) -> Option<ExprFnSig<'tcx>> {
+    let mut inputs = None;
+    let mut output = None;
+    let lang_items = cx.tcx.lang_items();
+
+    for pred in cx
+        .tcx
+        .bound_explicit_item_bounds(ty.item_def_id)
+        .transpose_iter()
+        .map(|x| x.map_bound(|(p, _)| p))
+    {
+        match pred.0.kind().skip_binder() {
+            PredicateKind::Trait(p)
+                if (lang_items.fn_trait() == Some(p.def_id())
+                    || lang_items.fn_mut_trait() == Some(p.def_id())
+                    || lang_items.fn_once_trait() == Some(p.def_id())) =>
+            {
+                if inputs.is_some() {
+                    // Multiple different fn trait impls. Is this even allowed?
+                    return None;
+                }
+                inputs = Some(
+                    pred.map_bound(|pred| pred.kind().rebind(p.trait_ref.substs.type_at(1)))
+                        .subst(cx.tcx, ty.substs),
+                );
             },
-            _ => None,
+            PredicateKind::Projection(p) if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output() => {
+                if output.is_some() {
+                    // Multiple different fn trait impls. Is this even allowed?
+                    return None;
+                }
+                output = Some(
+                    pred.map_bound(|pred| pred.kind().rebind(p.term.ty().unwrap()))
+                        .subst(cx.tcx, ty.substs),
+                );
+            },
+            _ => (),
         }
     }
+
+    inputs.map(|ty| ExprFnSig::Trait(ty, output))
 }
 
 #[derive(Clone, Copy)]
@@ -695,3 +774,18 @@ pub fn for_each_top_level_late_bound_region<B>(
     }
     ty.visit_with(&mut V { index: 0, f })
 }
+
+/// Gets the struct or enum variant from the given `Res`
+pub fn variant_of_res<'tcx>(cx: &LateContext<'tcx>, res: Res) -> Option<&'tcx VariantDef> {
+    match res {
+        Res::Def(DefKind::Struct, id) => Some(cx.tcx.adt_def(id).non_enum_variant()),
+        Res::Def(DefKind::Variant, id) => Some(cx.tcx.adt_def(cx.tcx.parent(id)).variant_with_id(id)),
+        Res::Def(DefKind::Ctor(CtorOf::Struct, _), id) => Some(cx.tcx.adt_def(cx.tcx.parent(id)).non_enum_variant()),
+        Res::Def(DefKind::Ctor(CtorOf::Variant, _), id) => {
+            let var_id = cx.tcx.parent(id);
+            Some(cx.tcx.adt_def(cx.tcx.parent(var_id)).variant_with_id(var_id))
+        },
+        Res::SelfCtor(id) => Some(cx.tcx.type_of(id).ty_adt_def().unwrap().non_enum_variant()),
+        _ => None,
+    }
+}
diff --git a/tests/ui/explicit_auto_deref.fixed b/tests/ui/explicit_auto_deref.fixed
new file mode 100644
index 00000000000..d4ff1b1566d
--- /dev/null
+++ b/tests/ui/explicit_auto_deref.fixed
@@ -0,0 +1,214 @@
+// run-rustfix
+
+#![warn(clippy::explicit_auto_deref)]
+#![allow(
+    dead_code,
+    unused_braces,
+    clippy::borrowed_box,
+    clippy::needless_borrow,
+    clippy::needless_return,
+    clippy::ptr_arg,
+    clippy::redundant_field_names,
+    clippy::too_many_arguments,
+    clippy::borrow_deref_ref,
+    clippy::let_unit_value
+)]
+
+trait CallableStr {
+    type T: Fn(&str);
+    fn callable_str(&self) -> Self::T;
+}
+impl CallableStr for () {
+    type T = fn(&str);
+    fn callable_str(&self) -> Self::T {
+        fn f(_: &str) {}
+        f
+    }
+}
+impl CallableStr for i32 {
+    type T = <() as CallableStr>::T;
+    fn callable_str(&self) -> Self::T {
+        ().callable_str()
+    }
+}
+
+trait CallableT<U: ?Sized> {
+    type T: Fn(&U);
+    fn callable_t(&self) -> Self::T;
+}
+impl<U: ?Sized> CallableT<U> for () {
+    type T = fn(&U);
+    fn callable_t(&self) -> Self::T {
+        fn f<U: ?Sized>(_: &U) {}
+        f::<U>
+    }
+}
+impl<U: ?Sized> CallableT<U> for i32 {
+    type T = <() as CallableT<U>>::T;
+    fn callable_t(&self) -> Self::T {
+        ().callable_t()
+    }
+}
+
+fn f_str(_: &str) {}
+fn f_string(_: &String) {}
+fn f_t<T>(_: T) {}
+fn f_ref_t<T: ?Sized>(_: &T) {}
+
+fn f_str_t<T>(_: &str, _: T) {}
+
+fn f_box_t<T>(_: &Box<T>) {}
+
+extern "C" {
+    fn var(_: u32, ...);
+}
+
+fn main() {
+    let s = String::new();
+
+    let _: &str = &s;
+    let _ = &*s; // Don't lint. Inferred type would change.
+    let _: &_ = &*s; // Don't lint. Inferred type would change.
+
+    f_str(&s);
+    f_t(&*s); // Don't lint. Inferred type would change.
+    f_ref_t(&*s); // Don't lint. Inferred type would change.
+
+    f_str_t(&s, &*s); // Don't lint second param.
+
+    let b = Box::new(Box::new(Box::new(5)));
+    let _: &Box<i32> = &b;
+    let _: &Box<_> = &**b; // Don't lint. Inferred type would change.
+
+    f_box_t(&**b); // Don't lint. Inferred type would change.
+
+    let c = |_x: &str| ();
+    c(&s);
+
+    let c = |_x| ();
+    c(&*s); // Don't lint. Inferred type would change.
+
+    fn _f(x: &String) -> &str {
+        x
+    }
+
+    fn _f1(x: &String) -> &str {
+        { x }
+    }
+
+    fn _f2(x: &String) -> &str {
+        { x }
+    }
+
+    fn _f3(x: &Box<Box<Box<i32>>>) -> &Box<i32> {
+        x
+    }
+
+    fn _f4(
+        x: String,
+        f1: impl Fn(&str),
+        f2: &dyn Fn(&str),
+        f3: fn(&str),
+        f4: impl CallableStr,
+        f5: <() as CallableStr>::T,
+        f6: <i32 as CallableStr>::T,
+        f7: &dyn CallableStr<T = fn(&str)>,
+        f8: impl CallableT<str>,
+        f9: <() as CallableT<str>>::T,
+        f10: <i32 as CallableT<str>>::T,
+        f11: &dyn CallableT<str, T = fn(&str)>,
+    ) {
+        f1(&x);
+        f2(&x);
+        f3(&x);
+        f4.callable_str()(&x);
+        f5(&x);
+        f6(&x);
+        f7.callable_str()(&x);
+        f8.callable_t()(&x);
+        f9(&x);
+        f10(&x);
+        f11.callable_t()(&x);
+    }
+
+    struct S1<'a>(&'a str);
+    let _ = S1(&s);
+
+    struct S2<'a> {
+        s: &'a str,
+    }
+    let _ = S2 { s: &s };
+
+    struct S3<'a, T: ?Sized>(&'a T);
+    let _ = S3(&*s); // Don't lint. Inferred type would change.
+
+    struct S4<'a, T: ?Sized> {
+        s: &'a T,
+    }
+    let _ = S4 { s: &*s }; // Don't lint. Inferred type would change.
+
+    enum E1<'a> {
+        S1(&'a str),
+        S2 { s: &'a str },
+    }
+    impl<'a> E1<'a> {
+        fn m1(s: &'a String) {
+            let _ = Self::S1(s);
+            let _ = Self::S2 { s: s };
+        }
+    }
+    let _ = E1::S1(&s);
+    let _ = E1::S2 { s: &s };
+
+    enum E2<'a, T: ?Sized> {
+        S1(&'a T),
+        S2 { s: &'a T },
+    }
+    let _ = E2::S1(&*s); // Don't lint. Inferred type would change.
+    let _ = E2::S2 { s: &*s }; // Don't lint. Inferred type would change.
+
+    let ref_s = &s;
+    let _: &String = &*ref_s; // Don't lint reborrow.
+    f_string(&*ref_s); // Don't lint reborrow.
+
+    struct S5 {
+        foo: u32,
+    }
+    let b = Box::new(Box::new(S5 { foo: 5 }));
+    let _ = b.foo;
+    let _ = b.foo;
+    let _ = b.foo;
+
+    struct S6 {
+        foo: S5,
+    }
+    impl core::ops::Deref for S6 {
+        type Target = S5;
+        fn deref(&self) -> &Self::Target {
+            &self.foo
+        }
+    }
+    let s6 = S6 { foo: S5 { foo: 5 } };
+    let _ = (*s6).foo; // Don't lint. `S6` also has a field named `foo`
+
+    let ref_str = &"foo";
+    let _ = f_str(ref_str);
+    let ref_ref_str = &ref_str;
+    let _ = f_str(ref_ref_str);
+
+    fn _f5(x: &u32) -> u32 {
+        if true {
+            *x
+        } else {
+            return *x;
+        }
+    }
+
+    f_str(&&ref_str); // `needless_borrow` will suggest removing both references
+    f_str(&ref_str); // `needless_borrow` will suggest removing only one reference
+
+    let x = &&40;
+    unsafe {
+        var(0, &**x);
+    }
+}
diff --git a/tests/ui/explicit_auto_deref.rs b/tests/ui/explicit_auto_deref.rs
new file mode 100644
index 00000000000..99294a7947b
--- /dev/null
+++ b/tests/ui/explicit_auto_deref.rs
@@ -0,0 +1,214 @@
+// run-rustfix
+
+#![warn(clippy::explicit_auto_deref)]
+#![allow(
+    dead_code,
+    unused_braces,
+    clippy::borrowed_box,
+    clippy::needless_borrow,
+    clippy::needless_return,
+    clippy::ptr_arg,
+    clippy::redundant_field_names,
+    clippy::too_many_arguments,
+    clippy::borrow_deref_ref,
+    clippy::let_unit_value
+)]
+
+trait CallableStr {
+    type T: Fn(&str);
+    fn callable_str(&self) -> Self::T;
+}
+impl CallableStr for () {
+    type T = fn(&str);
+    fn callable_str(&self) -> Self::T {
+        fn f(_: &str) {}
+        f
+    }
+}
+impl CallableStr for i32 {
+    type T = <() as CallableStr>::T;
+    fn callable_str(&self) -> Self::T {
+        ().callable_str()
+    }
+}
+
+trait CallableT<U: ?Sized> {
+    type T: Fn(&U);
+    fn callable_t(&self) -> Self::T;
+}
+impl<U: ?Sized> CallableT<U> for () {
+    type T = fn(&U);
+    fn callable_t(&self) -> Self::T {
+        fn f<U: ?Sized>(_: &U) {}
+        f::<U>
+    }
+}
+impl<U: ?Sized> CallableT<U> for i32 {
+    type T = <() as CallableT<U>>::T;
+    fn callable_t(&self) -> Self::T {
+        ().callable_t()
+    }
+}
+
+fn f_str(_: &str) {}
+fn f_string(_: &String) {}
+fn f_t<T>(_: T) {}
+fn f_ref_t<T: ?Sized>(_: &T) {}
+
+fn f_str_t<T>(_: &str, _: T) {}
+
+fn f_box_t<T>(_: &Box<T>) {}
+
+extern "C" {
+    fn var(_: u32, ...);
+}
+
+fn main() {
+    let s = String::new();
+
+    let _: &str = &*s;
+    let _ = &*s; // Don't lint. Inferred type would change.
+    let _: &_ = &*s; // Don't lint. Inferred type would change.
+
+    f_str(&*s);
+    f_t(&*s); // Don't lint. Inferred type would change.
+    f_ref_t(&*s); // Don't lint. Inferred type would change.
+
+    f_str_t(&*s, &*s); // Don't lint second param.
+
+    let b = Box::new(Box::new(Box::new(5)));
+    let _: &Box<i32> = &**b;
+    let _: &Box<_> = &**b; // Don't lint. Inferred type would change.
+
+    f_box_t(&**b); // Don't lint. Inferred type would change.
+
+    let c = |_x: &str| ();
+    c(&*s);
+
+    let c = |_x| ();
+    c(&*s); // Don't lint. Inferred type would change.
+
+    fn _f(x: &String) -> &str {
+        &**x
+    }
+
+    fn _f1(x: &String) -> &str {
+        { &**x }
+    }
+
+    fn _f2(x: &String) -> &str {
+        &**{ x }
+    }
+
+    fn _f3(x: &Box<Box<Box<i32>>>) -> &Box<i32> {
+        &***x
+    }
+
+    fn _f4(
+        x: String,
+        f1: impl Fn(&str),
+        f2: &dyn Fn(&str),
+        f3: fn(&str),
+        f4: impl CallableStr,
+        f5: <() as CallableStr>::T,
+        f6: <i32 as CallableStr>::T,
+        f7: &dyn CallableStr<T = fn(&str)>,
+        f8: impl CallableT<str>,
+        f9: <() as CallableT<str>>::T,
+        f10: <i32 as CallableT<str>>::T,
+        f11: &dyn CallableT<str, T = fn(&str)>,
+    ) {
+        f1(&*x);
+        f2(&*x);
+        f3(&*x);
+        f4.callable_str()(&*x);
+        f5(&*x);
+        f6(&*x);
+        f7.callable_str()(&*x);
+        f8.callable_t()(&*x);
+        f9(&*x);
+        f10(&*x);
+        f11.callable_t()(&*x);
+    }
+
+    struct S1<'a>(&'a str);
+    let _ = S1(&*s);
+
+    struct S2<'a> {
+        s: &'a str,
+    }
+    let _ = S2 { s: &*s };
+
+    struct S3<'a, T: ?Sized>(&'a T);
+    let _ = S3(&*s); // Don't lint. Inferred type would change.
+
+    struct S4<'a, T: ?Sized> {
+        s: &'a T,
+    }
+    let _ = S4 { s: &*s }; // Don't lint. Inferred type would change.
+
+    enum E1<'a> {
+        S1(&'a str),
+        S2 { s: &'a str },
+    }
+    impl<'a> E1<'a> {
+        fn m1(s: &'a String) {
+            let _ = Self::S1(&**s);
+            let _ = Self::S2 { s: &**s };
+        }
+    }
+    let _ = E1::S1(&*s);
+    let _ = E1::S2 { s: &*s };
+
+    enum E2<'a, T: ?Sized> {
+        S1(&'a T),
+        S2 { s: &'a T },
+    }
+    let _ = E2::S1(&*s); // Don't lint. Inferred type would change.
+    let _ = E2::S2 { s: &*s }; // Don't lint. Inferred type would change.
+
+    let ref_s = &s;
+    let _: &String = &*ref_s; // Don't lint reborrow.
+    f_string(&*ref_s); // Don't lint reborrow.
+
+    struct S5 {
+        foo: u32,
+    }
+    let b = Box::new(Box::new(S5 { foo: 5 }));
+    let _ = b.foo;
+    let _ = (*b).foo;
+    let _ = (**b).foo;
+
+    struct S6 {
+        foo: S5,
+    }
+    impl core::ops::Deref for S6 {
+        type Target = S5;
+        fn deref(&self) -> &Self::Target {
+            &self.foo
+        }
+    }
+    let s6 = S6 { foo: S5 { foo: 5 } };
+    let _ = (*s6).foo; // Don't lint. `S6` also has a field named `foo`
+
+    let ref_str = &"foo";
+    let _ = f_str(*ref_str);
+    let ref_ref_str = &ref_str;
+    let _ = f_str(**ref_ref_str);
+
+    fn _f5(x: &u32) -> u32 {
+        if true {
+            *x
+        } else {
+            return *x;
+        }
+    }
+
+    f_str(&&*ref_str); // `needless_borrow` will suggest removing both references
+    f_str(&&**ref_str); // `needless_borrow` will suggest removing only one reference
+
+    let x = &&40;
+    unsafe {
+        var(0, &**x);
+    }
+}
diff --git a/tests/ui/explicit_auto_deref.stderr b/tests/ui/explicit_auto_deref.stderr
new file mode 100644
index 00000000000..55f956e37ae
--- /dev/null
+++ b/tests/ui/explicit_auto_deref.stderr
@@ -0,0 +1,196 @@
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:69:20
+   |
+LL |     let _: &str = &*s;
+   |                    ^^ help: try this: `s`
+   |
+   = note: `-D clippy::explicit-auto-deref` implied by `-D warnings`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:73:12
+   |
+LL |     f_str(&*s);
+   |            ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:77:14
+   |
+LL |     f_str_t(&*s, &*s); // Don't lint second param.
+   |              ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:80:25
+   |
+LL |     let _: &Box<i32> = &**b;
+   |                         ^^^ help: try this: `b`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:86:8
+   |
+LL |     c(&*s);
+   |        ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:92:9
+   |
+LL |         &**x
+   |         ^^^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:96:11
+   |
+LL |         { &**x }
+   |           ^^^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:100:9
+   |
+LL |         &**{ x }
+   |         ^^^^^^^^ help: try this: `{ x }`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:104:9
+   |
+LL |         &***x
+   |         ^^^^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:121:13
+   |
+LL |         f1(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:122:13
+   |
+LL |         f2(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:123:13
+   |
+LL |         f3(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:124:28
+   |
+LL |         f4.callable_str()(&*x);
+   |                            ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:125:13
+   |
+LL |         f5(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:126:13
+   |
+LL |         f6(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:127:28
+   |
+LL |         f7.callable_str()(&*x);
+   |                            ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:128:26
+   |
+LL |         f8.callable_t()(&*x);
+   |                          ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:129:13
+   |
+LL |         f9(&*x);
+   |             ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:130:14
+   |
+LL |         f10(&*x);
+   |              ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:131:27
+   |
+LL |         f11.callable_t()(&*x);
+   |                           ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:135:17
+   |
+LL |     let _ = S1(&*s);
+   |                 ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:140:22
+   |
+LL |     let _ = S2 { s: &*s };
+   |                      ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:156:30
+   |
+LL |             let _ = Self::S1(&**s);
+   |                              ^^^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:157:35
+   |
+LL |             let _ = Self::S2 { s: &**s };
+   |                                   ^^^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:160:21
+   |
+LL |     let _ = E1::S1(&*s);
+   |                     ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:161:26
+   |
+LL |     let _ = E1::S2 { s: &*s };
+   |                          ^^ help: try this: `s`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:179:13
+   |
+LL |     let _ = (*b).foo;
+   |             ^^^^ help: try this: `b`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:180:13
+   |
+LL |     let _ = (**b).foo;
+   |             ^^^^^ help: try this: `b`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:195:19
+   |
+LL |     let _ = f_str(*ref_str);
+   |                   ^^^^^^^^ help: try this: `ref_str`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:197:19
+   |
+LL |     let _ = f_str(**ref_ref_str);
+   |                   ^^^^^^^^^^^^^ help: try this: `ref_ref_str`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:207:13
+   |
+LL |     f_str(&&*ref_str); // `needless_borrow` will suggest removing both references
+   |             ^^^^^^^^ help: try this: `ref_str`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:208:12
+   |
+LL |     f_str(&&**ref_str); // `needless_borrow` will suggest removing only one reference
+   |            ^^^^^^^^^^ help: try this: `ref_str`
+
+error: aborting due to 32 previous errors
+
diff --git a/tests/ui/explicit_deref_methods.fixed b/tests/ui/explicit_deref_methods.fixed
index 92f27e68549..523cae183ee 100644
--- a/tests/ui/explicit_deref_methods.fixed
+++ b/tests/ui/explicit_deref_methods.fixed
@@ -4,7 +4,8 @@
     unused_variables,
     clippy::clone_double_ref,
     clippy::needless_borrow,
-    clippy::borrow_deref_ref
+    clippy::borrow_deref_ref,
+    clippy::explicit_auto_deref
 )]
 #![warn(clippy::explicit_deref_methods)]
 
diff --git a/tests/ui/explicit_deref_methods.rs b/tests/ui/explicit_deref_methods.rs
index d118607f992..0bbc1ae57cd 100644
--- a/tests/ui/explicit_deref_methods.rs
+++ b/tests/ui/explicit_deref_methods.rs
@@ -4,7 +4,8 @@
     unused_variables,
     clippy::clone_double_ref,
     clippy::needless_borrow,
-    clippy::borrow_deref_ref
+    clippy::borrow_deref_ref,
+    clippy::explicit_auto_deref
 )]
 #![warn(clippy::explicit_deref_methods)]
 
diff --git a/tests/ui/explicit_deref_methods.stderr b/tests/ui/explicit_deref_methods.stderr
index 8e8b358972b..4b10ed1377b 100644
--- a/tests/ui/explicit_deref_methods.stderr
+++ b/tests/ui/explicit_deref_methods.stderr
@@ -1,5 +1,5 @@
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:35:19
+  --> $DIR/explicit_deref_methods.rs:36:19
    |
 LL |     let b: &str = a.deref();
    |                   ^^^^^^^^^ help: try this: `&*a`
@@ -7,67 +7,67 @@ LL |     let b: &str = a.deref();
    = note: `-D clippy::explicit-deref-methods` implied by `-D warnings`
 
 error: explicit `deref_mut` method call
-  --> $DIR/explicit_deref_methods.rs:37:23
+  --> $DIR/explicit_deref_methods.rs:38:23
    |
 LL |     let b: &mut str = a.deref_mut();
    |                       ^^^^^^^^^^^^^ help: try this: `&mut **a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:40:39
+  --> $DIR/explicit_deref_methods.rs:41:39
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                       ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:40:50
+  --> $DIR/explicit_deref_methods.rs:41:50
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                                  ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:42:20
+  --> $DIR/explicit_deref_methods.rs:43:20
    |
 LL |     println!("{}", a.deref());
    |                    ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:45:11
+  --> $DIR/explicit_deref_methods.rs:46:11
    |
 LL |     match a.deref() {
    |           ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:49:28
+  --> $DIR/explicit_deref_methods.rs:50:28
    |
 LL |     let b: String = concat(a.deref());
    |                            ^^^^^^^^^ help: try this: `&*a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:51:13
+  --> $DIR/explicit_deref_methods.rs:52:13
    |
 LL |     let b = just_return(a).deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `just_return(a)`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:53:28
+  --> $DIR/explicit_deref_methods.rs:54:28
    |
 LL |     let b: String = concat(just_return(a).deref());
    |                            ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `just_return(a)`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:55:19
+  --> $DIR/explicit_deref_methods.rs:56:19
    |
 LL |     let b: &str = a.deref().deref();
    |                   ^^^^^^^^^^^^^^^^^ help: try this: `&**a`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:58:13
+  --> $DIR/explicit_deref_methods.rs:59:13
    |
 LL |     let b = opt_a.unwrap().deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*opt_a.unwrap()`
 
 error: explicit `deref` method call
-  --> $DIR/explicit_deref_methods.rs:84:31
+  --> $DIR/explicit_deref_methods.rs:85:31
    |
 LL |     let b: &str = expr_deref!(a.deref());
    |                               ^^^^^^^^^ help: try this: `&*a`
diff --git a/tests/ui/needless_borrow.fixed b/tests/ui/needless_borrow.fixed
index e7a483c0582..cb005122436 100644
--- a/tests/ui/needless_borrow.fixed
+++ b/tests/ui/needless_borrow.fixed
@@ -62,7 +62,18 @@ fn main() {
         0 => &mut x,
         _ => &mut *x,
     };
-
+    let y: &mut i32 = match 0 {
+        // Lint here. The type given above triggers auto-borrow.
+        0 => x,
+        _ => &mut *x,
+    };
+    fn ref_mut_i32(_: &mut i32) {}
+    ref_mut_i32(match 0 {
+        // Lint here. The type given above triggers auto-borrow.
+        0 => x,
+        _ => &mut *x,
+    });
+    // use 'x' after to make sure it's still usable in the fixed code.
     *x = 5;
 
     let s = String::new();
@@ -74,6 +85,36 @@ fn main() {
     let _ = x.0;
     let x = &x as *const (i32, i32);
     let _ = unsafe { (*x).0 };
+
+    // Issue #8367
+    trait Foo {
+        fn foo(self);
+    }
+    impl Foo for &'_ () {
+        fn foo(self) {}
+    }
+    (&()).foo(); // Don't lint. `()` doesn't implement `Foo`
+    (&()).foo();
+
+    impl Foo for i32 {
+        fn foo(self) {}
+    }
+    impl Foo for &'_ i32 {
+        fn foo(self) {}
+    }
+    (&5).foo(); // Don't lint. `5` will call `<i32 as Foo>::foo`
+    (&5).foo();
+
+    trait FooRef {
+        fn foo_ref(&self);
+    }
+    impl FooRef for () {
+        fn foo_ref(&self) {}
+    }
+    impl FooRef for &'_ () {
+        fn foo_ref(&self) {}
+    }
+    (&&()).foo_ref(); // Don't lint. `&()` will call `<() as FooRef>::foo_ref`
 }
 
 #[allow(clippy::needless_borrowed_reference)]
diff --git a/tests/ui/needless_borrow.rs b/tests/ui/needless_borrow.rs
index 1d6bf46405a..d636a401003 100644
--- a/tests/ui/needless_borrow.rs
+++ b/tests/ui/needless_borrow.rs
@@ -62,7 +62,18 @@ fn main() {
         0 => &mut x,
         _ => &mut *x,
     };
-
+    let y: &mut i32 = match 0 {
+        // Lint here. The type given above triggers auto-borrow.
+        0 => &mut x,
+        _ => &mut *x,
+    };
+    fn ref_mut_i32(_: &mut i32) {}
+    ref_mut_i32(match 0 {
+        // Lint here. The type given above triggers auto-borrow.
+        0 => &mut x,
+        _ => &mut *x,
+    });
+    // use 'x' after to make sure it's still usable in the fixed code.
     *x = 5;
 
     let s = String::new();
@@ -74,6 +85,36 @@ fn main() {
     let _ = (&x).0;
     let x = &x as *const (i32, i32);
     let _ = unsafe { (&*x).0 };
+
+    // Issue #8367
+    trait Foo {
+        fn foo(self);
+    }
+    impl Foo for &'_ () {
+        fn foo(self) {}
+    }
+    (&()).foo(); // Don't lint. `()` doesn't implement `Foo`
+    (&&()).foo();
+
+    impl Foo for i32 {
+        fn foo(self) {}
+    }
+    impl Foo for &'_ i32 {
+        fn foo(self) {}
+    }
+    (&5).foo(); // Don't lint. `5` will call `<i32 as Foo>::foo`
+    (&&5).foo();
+
+    trait FooRef {
+        fn foo_ref(&self);
+    }
+    impl FooRef for () {
+        fn foo_ref(&self) {}
+    }
+    impl FooRef for &'_ () {
+        fn foo_ref(&self) {}
+    }
+    (&&()).foo_ref(); // Don't lint. `&()` will call `<() as FooRef>::foo_ref`
 }
 
 #[allow(clippy::needless_borrowed_reference)]
diff --git a/tests/ui/needless_borrow.stderr b/tests/ui/needless_borrow.stderr
index be59d8f546d..8a2e2b98959 100644
--- a/tests/ui/needless_borrow.stderr
+++ b/tests/ui/needless_borrow.stderr
@@ -84,17 +84,41 @@ error: this expression creates a reference which is immediately dereferenced by
 LL |     let y: &mut i32 = &mut &mut x;
    |                       ^^^^^^^^^^^ help: change this to: `x`
 
+error: this expression creates a reference which is immediately dereferenced by the compiler
+  --> $DIR/needless_borrow.rs:67:14
+   |
+LL |         0 => &mut x,
+   |              ^^^^^^ help: change this to: `x`
+
+error: this expression creates a reference which is immediately dereferenced by the compiler
+  --> $DIR/needless_borrow.rs:73:14
+   |
+LL |         0 => &mut x,
+   |              ^^^^^^ help: change this to: `x`
+
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:74:13
+  --> $DIR/needless_borrow.rs:85:13
    |
 LL |     let _ = (&x).0;
    |             ^^^^ help: change this to: `x`
 
 error: this expression borrows a value the compiler would automatically borrow
-  --> $DIR/needless_borrow.rs:76:22
+  --> $DIR/needless_borrow.rs:87:22
    |
 LL |     let _ = unsafe { (&*x).0 };
    |                      ^^^^^ help: change this to: `(*x)`
 
-error: aborting due to 16 previous errors
+error: this expression creates a reference which is immediately dereferenced by the compiler
+  --> $DIR/needless_borrow.rs:97:5
+   |
+LL |     (&&()).foo();
+   |     ^^^^^^ help: change this to: `(&())`
+
+error: this expression creates a reference which is immediately dereferenced by the compiler
+  --> $DIR/needless_borrow.rs:106:5
+   |
+LL |     (&&5).foo();
+   |     ^^^^^ help: change this to: `(&5)`
+
+error: aborting due to 20 previous errors
 
diff --git a/tests/ui/needless_borrow_pat.rs b/tests/ui/needless_borrow_pat.rs
index 04b6283da3c..222e8e61799 100644
--- a/tests/ui/needless_borrow_pat.rs
+++ b/tests/ui/needless_borrow_pat.rs
@@ -1,7 +1,7 @@
 // FIXME: run-rustfix waiting on multi-span suggestions
 
 #![warn(clippy::needless_borrow)]
-#![allow(clippy::needless_borrowed_reference)]
+#![allow(clippy::needless_borrowed_reference, clippy::explicit_auto_deref)]
 
 fn f1(_: &str) {}
 macro_rules! m1 {
diff --git a/tests/ui/ref_binding_to_reference.rs b/tests/ui/ref_binding_to_reference.rs
index 570ef406e4a..c8d0e56b197 100644
--- a/tests/ui/ref_binding_to_reference.rs
+++ b/tests/ui/ref_binding_to_reference.rs
@@ -2,7 +2,7 @@
 
 #![feature(lint_reasons)]
 #![warn(clippy::ref_binding_to_reference)]
-#![allow(clippy::needless_borrowed_reference)]
+#![allow(clippy::needless_borrowed_reference, clippy::explicit_auto_deref)]
 
 fn f1(_: &str) {}
 macro_rules! m2 {
diff --git a/tests/ui/search_is_some_fixable_none.fixed b/tests/ui/search_is_some_fixable_none.fixed
index 6831fb2cf59..5190c5304c7 100644
--- a/tests/ui/search_is_some_fixable_none.fixed
+++ b/tests/ui/search_is_some_fixable_none.fixed
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code)]
+#![allow(dead_code, clippy::explicit_auto_deref)]
 #![warn(clippy::search_is_some)]
 
 fn main() {
diff --git a/tests/ui/search_is_some_fixable_none.rs b/tests/ui/search_is_some_fixable_none.rs
index 767518ab0c0..310d87333a9 100644
--- a/tests/ui/search_is_some_fixable_none.rs
+++ b/tests/ui/search_is_some_fixable_none.rs
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code)]
+#![allow(dead_code, clippy::explicit_auto_deref)]
 #![warn(clippy::search_is_some)]
 
 fn main() {
diff --git a/tests/ui/search_is_some_fixable_some.fixed b/tests/ui/search_is_some_fixable_some.fixed
index 7c940a2b069..5a2aee465d1 100644
--- a/tests/ui/search_is_some_fixable_some.fixed
+++ b/tests/ui/search_is_some_fixable_some.fixed
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code)]
+#![allow(dead_code, clippy::explicit_auto_deref)]
 #![warn(clippy::search_is_some)]
 
 fn main() {
diff --git a/tests/ui/search_is_some_fixable_some.rs b/tests/ui/search_is_some_fixable_some.rs
index 77fd52e4ce7..0e98ae18a21 100644
--- a/tests/ui/search_is_some_fixable_some.rs
+++ b/tests/ui/search_is_some_fixable_some.rs
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code)]
+#![allow(dead_code, clippy::explicit_auto_deref)]
 #![warn(clippy::search_is_some)]
 
 fn main() {
diff --git a/tests/ui/useless_asref.fixed b/tests/ui/useless_asref.fixed
index e431661d180..90cb8945e77 100644
--- a/tests/ui/useless_asref.fixed
+++ b/tests/ui/useless_asref.fixed
@@ -1,6 +1,7 @@
 // run-rustfix
 
 #![deny(clippy::useless_asref)]
+#![allow(clippy::explicit_auto_deref)]
 
 use std::fmt::Debug;
 
diff --git a/tests/ui/useless_asref.rs b/tests/ui/useless_asref.rs
index 6ae931d7aa4..cb9f8ae5909 100644
--- a/tests/ui/useless_asref.rs
+++ b/tests/ui/useless_asref.rs
@@ -1,6 +1,7 @@
 // run-rustfix
 
 #![deny(clippy::useless_asref)]
+#![allow(clippy::explicit_auto_deref)]
 
 use std::fmt::Debug;
 
diff --git a/tests/ui/useless_asref.stderr b/tests/ui/useless_asref.stderr
index 5876b54aca8..b21c67bb364 100644
--- a/tests/ui/useless_asref.stderr
+++ b/tests/ui/useless_asref.stderr
@@ -1,5 +1,5 @@
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:43:18
+  --> $DIR/useless_asref.rs:44:18
    |
 LL |         foo_rstr(rstr.as_ref());
    |                  ^^^^^^^^^^^^^ help: try this: `rstr`
@@ -11,61 +11,61 @@ LL | #![deny(clippy::useless_asref)]
    |         ^^^^^^^^^^^^^^^^^^^^^
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:45:20
+  --> $DIR/useless_asref.rs:46:20
    |
 LL |         foo_rslice(rslice.as_ref());
    |                    ^^^^^^^^^^^^^^^ help: try this: `rslice`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:49:21
+  --> $DIR/useless_asref.rs:50:21
    |
 LL |         foo_mrslice(mrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:51:20
+  --> $DIR/useless_asref.rs:52:20
    |
 LL |         foo_rslice(mrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:58:20
+  --> $DIR/useless_asref.rs:59:20
    |
 LL |         foo_rslice(rrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^ help: try this: `rrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:60:18
+  --> $DIR/useless_asref.rs:61:18
    |
 LL |         foo_rstr(rrrrrstr.as_ref());
    |                  ^^^^^^^^^^^^^^^^^ help: try this: `rrrrrstr`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:65:21
+  --> $DIR/useless_asref.rs:66:21
    |
 LL |         foo_mrslice(mrrrrrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:67:20
+  --> $DIR/useless_asref.rs:68:20
    |
 LL |         foo_rslice(mrrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:71:16
+  --> $DIR/useless_asref.rs:72:16
    |
 LL |     foo_rrrrmr((&&&&MoreRef).as_ref());
    |                ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(&&&&MoreRef)`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:121:13
+  --> $DIR/useless_asref.rs:122:13
    |
 LL |     foo_mrt(mrt.as_mut());
    |             ^^^^^^^^^^^^ help: try this: `mrt`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:123:12
+  --> $DIR/useless_asref.rs:124:12
    |
 LL |     foo_rt(mrt.as_ref());
    |            ^^^^^^^^^^^^ help: try this: `mrt`