Auto merge of #7254 - Jarcho:needless_borrow_2, r=Manishearth

Move `needless_borrow` to style

fixes: #3742

#7105 should be merged first to fix the false positive.

changelog: move `needless_borrow` from `nursery` to `style`

15 files changed, 164 insertions, 173 deletions

diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index a263e8b0ca4..877d9054d7b 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -1361,6 +1361,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(needless_arbitrary_self_type::NEEDLESS_ARBITRARY_SELF_TYPE),
         LintId::of(needless_bool::BOOL_COMPARISON),
         LintId::of(needless_bool::NEEDLESS_BOOL),
+        LintId::of(needless_borrow::NEEDLESS_BORROW),
         LintId::of(needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE),
         LintId::of(needless_question_mark::NEEDLESS_QUESTION_MARK),
         LintId::of(needless_update::NEEDLESS_UPDATE),
@@ -1544,6 +1545,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(misc_early::REDUNDANT_PATTERN),
         LintId::of(mut_mutex_lock::MUT_MUTEX_LOCK),
         LintId::of(mut_reference::UNNECESSARY_MUT_PASSED),
+        LintId::of(needless_borrow::NEEDLESS_BORROW),
         LintId::of(neg_multiply::NEG_MULTIPLY),
         LintId::of(new_without_default::NEW_WITHOUT_DEFAULT),
         LintId::of(non_copy_const::BORROW_INTERIOR_MUTABLE_CONST),
@@ -1783,7 +1785,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(missing_const_for_fn::MISSING_CONST_FOR_FN),
         LintId::of(mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
         LintId::of(mutex_atomic::MUTEX_INTEGER),
-        LintId::of(needless_borrow::NEEDLESS_BORROW),
         LintId::of(path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE),
         LintId::of(redundant_pub_crate::REDUNDANT_PUB_CRATE),
         LintId::of(regex::TRIVIAL_REGEX),
diff --git a/clippy_lints/src/needless_borrow.rs b/clippy_lints/src/needless_borrow.rs
index 965b131770e..bcedebfccc7 100644
--- a/clippy_lints/src/needless_borrow.rs
+++ b/clippy_lints/src/needless_borrow.rs
@@ -34,7 +34,7 @@ declare_clippy_lint! {
     /// let x: &i32 = &5;
     /// ```
     pub NEEDLESS_BORROW,
-    nursery,
+    style,
     "taking a reference that is going to be automatically dereferenced"
 }
 
diff --git a/clippy_lints/src/ptr.rs b/clippy_lints/src/ptr.rs
index b0674f90678..12c44436874 100644
--- a/clippy_lints/src/ptr.rs
+++ b/clippy_lints/src/ptr.rs
@@ -211,7 +211,7 @@ fn check_invalid_ptr_usage<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
     ];
 
     if_chain! {
-        if let ExprKind::Call(ref fun, ref args) = expr.kind;
+        if let ExprKind::Call(fun, args) = expr.kind;
         if let ExprKind::Path(ref qpath) = fun.kind;
         if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
         let fun_def_path = cx.get_def_path(fun_def_id).into_iter().map(Symbol::to_ident_string).collect::<Vec<_>>();
diff --git a/clippy_lints/src/single_component_path_imports.rs b/clippy_lints/src/single_component_path_imports.rs
index a45bb102389..1eaad438237 100644
--- a/clippy_lints/src/single_component_path_imports.rs
+++ b/clippy_lints/src/single_component_path_imports.rs
@@ -70,7 +70,7 @@ fn check_mod(cx: &EarlyContext<'_>, items: &[P<Item>]) {
     for item in items {
         track_uses(
             cx,
-            &item,
+            item,
             &mut imports_reused_with_self,
             &mut single_use_usages,
             &mut macros,
@@ -117,7 +117,7 @@ fn track_uses(
 
     match &item.kind {
         ItemKind::Mod(_, ModKind::Loaded(ref items, ..)) => {
-            check_mod(cx, &items);
+            check_mod(cx, items);
         },
         ItemKind::MacroDef(MacroDef { macro_rules: true, .. }) => {
             macros.push(item.ident.name);
diff --git a/clippy_lints/src/unused_io_amount.rs b/clippy_lints/src/unused_io_amount.rs
index c27a6d4e347..ee082d30d93 100644
--- a/clippy_lints/src/unused_io_amount.rs
+++ b/clippy_lints/src/unused_io_amount.rs
@@ -66,7 +66,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedIoAmount {
 
 fn check_map_error(cx: &LateContext<'_>, call: &hir::Expr<'_>, expr: &hir::Expr<'_>) {
     let mut call = call;
-    while let hir::ExprKind::MethodCall(ref path, _, ref args, _) = call.kind {
+    while let hir::ExprKind::MethodCall(path, _, args, _) = call.kind {
         if matches!(&*path.ident.as_str(), "or" | "or_else" | "ok") {
             call = &args[0];
         } else {
diff --git a/clippy_lints/src/utils/internal_lints/metadata_collector.rs b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
index e9fa043b20f..a672af88271 100644
--- a/clippy_lints/src/utils/internal_lints/metadata_collector.rs
+++ b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
@@ -379,7 +379,7 @@ impl<'hir> LateLintPass<'hir> for MetadataCollector {
     /// }
     /// ```
     fn check_item(&mut self, cx: &LateContext<'hir>, item: &'hir Item<'_>) {
-        if let ItemKind::Static(ref ty, Mutability::Not, _) = item.kind {
+        if let ItemKind::Static(ty, Mutability::Not, _) = item.kind {
             // Normal lint
             if_chain! {
                 // item validation
@@ -489,7 +489,7 @@ fn extract_attr_docs(cx: &LateContext<'_>, item: &Item<'_>) -> Option<String> {
         .hir()
         .attrs(item.hir_id())
         .iter()
-        .filter_map(|ref x| x.doc_str().map(|sym| sym.as_str().to_string()))
+        .filter_map(|x| x.doc_str().map(|sym| sym.as_str().to_string()))
         .reduce(|mut acc, sym| {
             acc.push_str(&sym);
             acc.push('\n');
@@ -596,7 +596,7 @@ fn extract_emission_info<'hir>(
     let mut multi_part = false;
 
     for arg in args {
-        let (arg_ty, _) = walk_ptrs_ty_depth(cx.typeck_results().expr_ty(&arg));
+        let (arg_ty, _) = walk_ptrs_ty_depth(cx.typeck_results().expr_ty(arg));
 
         if match_type(cx, arg_ty, &paths::LINT) {
             // If we found the lint arg, extract the lint name
@@ -671,7 +671,7 @@ impl<'a, 'hir> intravisit::Visitor<'hir> for LintResolver<'a, 'hir> {
             if let ExprKind::Path(qpath) = &expr.kind;
             if let QPath::Resolved(_, path) = qpath;
 
-            let (expr_ty, _) = walk_ptrs_ty_depth(self.cx.typeck_results().expr_ty(&expr));
+            let (expr_ty, _) = walk_ptrs_ty_depth(self.cx.typeck_results().expr_ty(expr));
             if match_type(self.cx, expr_ty, &paths::LINT);
             then {
                 if let hir::def::Res::Def(DefKind::Static, _) = path.res {
@@ -730,7 +730,7 @@ impl<'a, 'hir> intravisit::Visitor<'hir> for ApplicabilityResolver<'a, 'hir> {
     }
 
     fn visit_expr(&mut self, expr: &'hir hir::Expr<'hir>) {
-        let (expr_ty, _) = walk_ptrs_ty_depth(self.cx.typeck_results().expr_ty(&expr));
+        let (expr_ty, _) = walk_ptrs_ty_depth(self.cx.typeck_results().expr_ty(expr));
 
         if_chain! {
             if match_type(self.cx, expr_ty, &paths::APPLICABILITY);
diff --git a/clippy_utils/src/consts.rs b/clippy_utils/src/consts.rs
index 2a305d8bcbe..0d7fdeeb920 100644
--- a/clippy_utils/src/consts.rs
+++ b/clippy_utils/src/consts.rs
@@ -229,25 +229,25 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
     pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
         match e.kind {
             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
-            ExprKind::Block(ref block, _) => self.block(block),
+            ExprKind::Block(block, _) => self.block(block),
             ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.typeck_results.expr_ty_opt(e))),
-            ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec),
-            ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
-            ExprKind::Repeat(ref value, _) => {
+            ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
+            ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
+            ExprKind::Repeat(value, _) => {
                 let n = match self.typeck_results.expr_ty(e).kind() {
                     ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
                     _ => span_bug!(e.span, "typeck error"),
                 };
                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
             },
-            ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
+            ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
                 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
                 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
                 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
             }),
-            ExprKind::If(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
-            ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
-            ExprKind::Call(ref callee, ref args) => {
+            ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
+            ExprKind::Binary(op, left, right) => self.binop(op, left, right),
+            ExprKind::Call(callee, args) => {
                 // We only handle a few const functions for now.
                 if_chain! {
                     if args.is_empty();
@@ -273,8 +273,8 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                     }
                 }
             },
-            ExprKind::Index(ref arr, ref index) => self.index(arr, index),
-            ExprKind::AddrOf(_, _, ref inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
+            ExprKind::Index(arr, index) => self.index(arr, index),
+            ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
             // TODO: add other expressions.
             _ => None,
         }
@@ -349,7 +349,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                     )
                     .ok()
                     .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
-                let result = miri_to_const(&result);
+                let result = miri_to_const(result);
                 if result.is_some() {
                     self.needed_resolution = true;
                 }
diff --git a/clippy_utils/src/higher.rs b/clippy_utils/src/higher.rs
index 25b4491616c..8be36756b33 100644
--- a/clippy_utils/src/higher.rs
+++ b/clippy_utils/src/higher.rs
@@ -58,7 +58,7 @@ pub fn range<'a>(expr: &'a hir::Expr<'_>) -> Option<Range<'a>> {
     }
 
     match expr.kind {
-        hir::ExprKind::Call(ref path, ref args)
+        hir::ExprKind::Call(path, args)
             if matches!(
                 path.kind,
                 hir::ExprKind::Path(hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, _))
@@ -70,7 +70,7 @@ pub fn range<'a>(expr: &'a hir::Expr<'_>) -> Option<Range<'a>> {
                 limits: ast::RangeLimits::Closed,
             })
         },
-        hir::ExprKind::Struct(path, ref fields, None) => match path {
+        hir::ExprKind::Struct(path, fields, None) => match path {
             hir::QPath::LangItem(hir::LangItem::RangeFull, _) => Some(Range {
                 start: None,
                 end: None,
@@ -112,7 +112,7 @@ pub fn is_from_for_desugar(local: &hir::Local<'_>) -> bool {
     // }
     // ```
     if_chain! {
-        if let Some(ref expr) = local.init;
+        if let Some(expr) = local.init;
         if let hir::ExprKind::Match(_, _, hir::MatchSource::ForLoopDesugar) = expr.kind;
         then {
             return true;
@@ -140,14 +140,14 @@ pub fn for_loop<'tcx>(
     expr: &'tcx hir::Expr<'tcx>,
 ) -> Option<(&hir::Pat<'_>, &'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>, Span)> {
     if_chain! {
-        if let hir::ExprKind::Match(ref iterexpr, ref arms, hir::MatchSource::ForLoopDesugar) = expr.kind;
-        if let hir::ExprKind::Call(_, ref iterargs) = iterexpr.kind;
+        if let hir::ExprKind::Match(iterexpr, arms, hir::MatchSource::ForLoopDesugar) = expr.kind;
+        if let hir::ExprKind::Call(_, iterargs) = iterexpr.kind;
         if iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none();
-        if let hir::ExprKind::Loop(ref block, ..) = arms[0].body.kind;
+        if let hir::ExprKind::Loop(block, ..) = arms[0].body.kind;
         if block.expr.is_none();
         if let [ _, _, ref let_stmt, ref body ] = *block.stmts;
-        if let hir::StmtKind::Local(ref local) = let_stmt.kind;
-        if let hir::StmtKind::Expr(ref expr) = body.kind;
+        if let hir::StmtKind::Local(local) = let_stmt.kind;
+        if let hir::StmtKind::Expr(expr) = body.kind;
         then {
             return Some((&*local.pat, &iterargs[0], expr, arms[0].span));
         }
@@ -182,7 +182,7 @@ pub enum VecArgs<'a> {
 /// from `vec!`.
 pub fn vec_macro<'e>(cx: &LateContext<'_>, expr: &'e hir::Expr<'_>) -> Option<VecArgs<'e>> {
     if_chain! {
-        if let hir::ExprKind::Call(ref fun, ref args) = expr.kind;
+        if let hir::ExprKind::Call(fun, args) = expr.kind;
         if let hir::ExprKind::Path(ref qpath) = fun.kind;
         if is_expn_of(fun.span, "vec").is_some();
         if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
@@ -194,8 +194,8 @@ pub fn vec_macro<'e>(cx: &LateContext<'_>, expr: &'e hir::Expr<'_>) -> Option<Ve
             else if match_def_path(cx, fun_def_id, &paths::SLICE_INTO_VEC) && args.len() == 1 {
                 // `vec![a, b, c]` case
                 if_chain! {
-                    if let hir::ExprKind::Box(ref boxed) = args[0].kind;
-                    if let hir::ExprKind::Array(ref args) = boxed.kind;
+                    if let hir::ExprKind::Box(boxed) = args[0].kind;
+                    if let hir::ExprKind::Array(args) = boxed.kind;
                     then {
                         return Some(VecArgs::Vec(&*args));
                     }
@@ -227,7 +227,7 @@ pub fn extract_assert_macro_args<'tcx>(e: &'tcx Expr<'tcx>) -> Option<Vec<&'tcx
     /// compared
     fn ast_matchblock(matchblock_expr: &'tcx Expr<'tcx>) -> Option<Vec<&Expr<'_>>> {
         if_chain! {
-            if let ExprKind::Match(ref headerexpr, _, _) = &matchblock_expr.kind;
+            if let ExprKind::Match(headerexpr, _, _) = &matchblock_expr.kind;
             if let ExprKind::Tup([lhs, rhs]) = &headerexpr.kind;
             if let ExprKind::AddrOf(BorrowKind::Ref, _, lhs) = lhs.kind;
             if let ExprKind::AddrOf(BorrowKind::Ref, _, rhs) = rhs.kind;
@@ -238,12 +238,12 @@ pub fn extract_assert_macro_args<'tcx>(e: &'tcx Expr<'tcx>) -> Option<Vec<&'tcx
         None
     }
 
-    if let ExprKind::Block(ref block, _) = e.kind {
+    if let ExprKind::Block(block, _) = e.kind {
         if block.stmts.len() == 1 {
-            if let StmtKind::Semi(ref matchexpr) = block.stmts.get(0)?.kind {
+            if let StmtKind::Semi(matchexpr) = block.stmts.get(0)?.kind {
                 // macros with unique arg: `{debug_}assert!` (e.g., `debug_assert!(some_condition)`)
                 if_chain! {
-                    if let ExprKind::If(ref clause, _, _)  = matchexpr.kind;
+                    if let ExprKind::If(clause, _, _)  = matchexpr.kind;
                     if let ExprKind::Unary(UnOp::Not, condition) = clause.kind;
                     then {
                         return Some(vec![condition]);
@@ -252,8 +252,8 @@ pub fn extract_assert_macro_args<'tcx>(e: &'tcx Expr<'tcx>) -> Option<Vec<&'tcx
 
                 // debug macros with two args: `debug_assert_{ne, eq}` (e.g., `assert_ne!(a, b)`)
                 if_chain! {
-                    if let ExprKind::Block(ref matchblock,_) = matchexpr.kind;
-                    if let Some(ref matchblock_expr) = matchblock.expr;
+                    if let ExprKind::Block(matchblock,_) = matchexpr.kind;
+                    if let Some(matchblock_expr) = matchblock.expr;
                     then {
                         return ast_matchblock(matchblock_expr);
                     }
@@ -261,7 +261,7 @@ pub fn extract_assert_macro_args<'tcx>(e: &'tcx Expr<'tcx>) -> Option<Vec<&'tcx
             }
         } else if let Some(matchblock_expr) = block.expr {
             // macros with two args: `assert_{ne, eq}` (e.g., `assert_ne!(a, b)`)
-            return ast_matchblock(&matchblock_expr);
+            return ast_matchblock(matchblock_expr);
         }
     }
     None
diff --git a/clippy_utils/src/hir_utils.rs b/clippy_utils/src/hir_utils.rs
index 3b01158acd9..2fc12702f48 100644
--- a/clippy_utils/src/hir_utils.rs
+++ b/clippy_utils/src/hir_utils.rs
@@ -95,12 +95,12 @@ pub struct HirEqInterExpr<'a, 'b, 'tcx> {
 impl HirEqInterExpr<'_, '_, '_> {
     pub fn eq_stmt(&mut self, left: &Stmt<'_>, right: &Stmt<'_>) -> bool {
         match (&left.kind, &right.kind) {
-            (&StmtKind::Local(ref l), &StmtKind::Local(ref r)) => {
+            (&StmtKind::Local(l), &StmtKind::Local(r)) => {
                 // This additional check ensures that the type of the locals are equivalent even if the init
                 // expression or type have some inferred parts.
                 if let Some(typeck) = self.inner.maybe_typeck_results {
-                    let l_ty = typeck.pat_ty(&l.pat);
-                    let r_ty = typeck.pat_ty(&r.pat);
+                    let l_ty = typeck.pat_ty(l.pat);
+                    let r_ty = typeck.pat_ty(r.pat);
                     if !rustc_middle::ty::TyS::same_type(l_ty, r_ty) {
                         return false;
                     }
@@ -110,11 +110,9 @@ impl HirEqInterExpr<'_, '_, '_> {
                 // these only get added if the init and type is equal.
                 both(&l.init, &r.init, |l, r| self.eq_expr(l, r))
                     && both(&l.ty, &r.ty, |l, r| self.eq_ty(l, r))
-                    && self.eq_pat(&l.pat, &r.pat)
-            },
-            (&StmtKind::Expr(ref l), &StmtKind::Expr(ref r)) | (&StmtKind::Semi(ref l), &StmtKind::Semi(ref r)) => {
-                self.eq_expr(l, r)
+                    && self.eq_pat(l.pat, r.pat)
             },
+            (&StmtKind::Expr(l), &StmtKind::Expr(r)) | (&StmtKind::Semi(l), &StmtKind::Semi(r)) => self.eq_expr(l, r),
             _ => false,
         }
     }
@@ -165,7 +163,7 @@ impl HirEqInterExpr<'_, '_, '_> {
                 left.eq(right)
             },
             _ => {
-                over(&left.stmts, &right.stmts, |l, r| self.eq_stmt(l, r))
+                over(left.stmts, right.stmts, |l, r| self.eq_stmt(l, r))
                     && both(&left.expr, &right.expr, |l, r| self.eq_expr(l, r))
             },
         }
@@ -192,20 +190,20 @@ impl HirEqInterExpr<'_, '_, '_> {
             &reduce_exprkind(self.inner.cx, &left.kind),
             &reduce_exprkind(self.inner.cx, &right.kind),
         ) {
-            (&ExprKind::AddrOf(lb, l_mut, ref le), &ExprKind::AddrOf(rb, r_mut, ref re)) => {
+            (&ExprKind::AddrOf(lb, l_mut, le), &ExprKind::AddrOf(rb, r_mut, re)) => {
                 lb == rb && l_mut == r_mut && self.eq_expr(le, re)
             },
             (&ExprKind::Continue(li), &ExprKind::Continue(ri)) => {
                 both(&li.label, &ri.label, |l, r| l.ident.name == r.ident.name)
             },
-            (&ExprKind::Assign(ref ll, ref lr, _), &ExprKind::Assign(ref rl, ref rr, _)) => {
+            (&ExprKind::Assign(ll, lr, _), &ExprKind::Assign(rl, rr, _)) => {
                 self.inner.allow_side_effects && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
             },
-            (&ExprKind::AssignOp(ref lo, ref ll, ref lr), &ExprKind::AssignOp(ref ro, ref rl, ref rr)) => {
+            (&ExprKind::AssignOp(ref lo, ll, lr), &ExprKind::AssignOp(ref ro, rl, rr)) => {
                 self.inner.allow_side_effects && lo.node == ro.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
             },
-            (&ExprKind::Block(ref l, _), &ExprKind::Block(ref r, _)) => self.eq_block(l, r),
-            (&ExprKind::Binary(l_op, ref ll, ref lr), &ExprKind::Binary(r_op, ref rl, ref rr)) => {
+            (&ExprKind::Block(l, _), &ExprKind::Block(r, _)) => self.eq_block(l, r),
+            (&ExprKind::Binary(l_op, ll, lr), &ExprKind::Binary(r_op, rl, rr)) => {
                 l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
                     || swap_binop(l_op.node, ll, lr).map_or(false, |(l_op, ll, lr)| {
                         l_op == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
@@ -215,40 +213,37 @@ impl HirEqInterExpr<'_, '_, '_> {
                 both(&li.label, &ri.label, |l, r| l.ident.name == r.ident.name)
                     && both(le, re, |l, r| self.eq_expr(l, r))
             },
-            (&ExprKind::Box(ref l), &ExprKind::Box(ref r)) => self.eq_expr(l, r),
+            (&ExprKind::Box(l), &ExprKind::Box(r)) => self.eq_expr(l, r),
             (&ExprKind::Call(l_fun, l_args), &ExprKind::Call(r_fun, r_args)) => {
                 self.inner.allow_side_effects && self.eq_expr(l_fun, r_fun) && self.eq_exprs(l_args, r_args)
             },
-            (&ExprKind::Cast(ref lx, ref lt), &ExprKind::Cast(ref rx, ref rt))
-            | (&ExprKind::Type(ref lx, ref lt), &ExprKind::Type(ref rx, ref rt)) => {
+            (&ExprKind::Cast(lx, lt), &ExprKind::Cast(rx, rt)) | (&ExprKind::Type(lx, lt), &ExprKind::Type(rx, rt)) => {
                 self.eq_expr(lx, rx) && self.eq_ty(lt, rt)
             },
-            (&ExprKind::Field(ref l_f_exp, ref l_f_ident), &ExprKind::Field(ref r_f_exp, ref r_f_ident)) => {
+            (&ExprKind::Field(l_f_exp, ref l_f_ident), &ExprKind::Field(r_f_exp, ref r_f_ident)) => {
                 l_f_ident.name == r_f_ident.name && self.eq_expr(l_f_exp, r_f_exp)
             },
-            (&ExprKind::Index(ref la, ref li), &ExprKind::Index(ref ra, ref ri)) => {
-                self.eq_expr(la, ra) && self.eq_expr(li, ri)
-            },
-            (&ExprKind::If(ref lc, ref lt, ref le), &ExprKind::If(ref rc, ref rt, ref re)) => {
+            (&ExprKind::Index(la, li), &ExprKind::Index(ra, ri)) => self.eq_expr(la, ra) && self.eq_expr(li, ri),
+            (&ExprKind::If(lc, lt, ref le), &ExprKind::If(rc, rt, ref re)) => {
                 self.eq_expr(lc, rc) && self.eq_expr(&**lt, &**rt) && both(le, re, |l, r| self.eq_expr(l, r))
             },
             (&ExprKind::Lit(ref l), &ExprKind::Lit(ref r)) => l.node == r.node,
-            (&ExprKind::Loop(ref lb, ref ll, ref lls, _), &ExprKind::Loop(ref rb, ref rl, ref rls, _)) => {
+            (&ExprKind::Loop(lb, ref ll, ref lls, _), &ExprKind::Loop(rb, ref rl, ref rls, _)) => {
                 lls == rls && self.eq_block(lb, rb) && both(ll, rl, |l, r| l.ident.name == r.ident.name)
             },
-            (&ExprKind::Match(ref le, ref la, ref ls), &ExprKind::Match(ref re, ref ra, ref rs)) => {
+            (&ExprKind::Match(le, la, ref ls), &ExprKind::Match(re, ra, ref rs)) => {
                 ls == rs
                     && self.eq_expr(le, re)
                     && over(la, ra, |l, r| {
-                        self.eq_pat(&l.pat, &r.pat)
+                        self.eq_pat(l.pat, r.pat)
                             && both(&l.guard, &r.guard, |l, r| self.eq_guard(l, r))
-                            && self.eq_expr(&l.body, &r.body)
+                            && self.eq_expr(l.body, r.body)
                     })
             },
             (&ExprKind::MethodCall(l_path, _, l_args, _), &ExprKind::MethodCall(r_path, _, r_args, _)) => {
                 self.inner.allow_side_effects && self.eq_path_segment(l_path, r_path) && self.eq_exprs(l_args, r_args)
             },
-            (&ExprKind::Repeat(ref le, ref ll_id), &ExprKind::Repeat(ref re, ref rl_id)) => {
+            (&ExprKind::Repeat(le, ref ll_id), &ExprKind::Repeat(re, ref rl_id)) => {
                 let mut celcx = constant_context(self.inner.cx, self.inner.cx.tcx.typeck_body(ll_id.body));
                 let ll = celcx.expr(&self.inner.cx.tcx.hir().body(ll_id.body).value);
                 let mut celcx = constant_context(self.inner.cx, self.inner.cx.tcx.typeck_body(rl_id.body));
@@ -258,15 +253,15 @@ impl HirEqInterExpr<'_, '_, '_> {
             },
             (&ExprKind::Ret(ref l), &ExprKind::Ret(ref r)) => both(l, r, |l, r| self.eq_expr(l, r)),
             (&ExprKind::Path(ref l), &ExprKind::Path(ref r)) => self.eq_qpath(l, r),
-            (&ExprKind::Struct(ref l_path, ref lf, ref lo), &ExprKind::Struct(ref r_path, ref rf, ref ro)) => {
+            (&ExprKind::Struct(l_path, lf, ref lo), &ExprKind::Struct(r_path, rf, ref ro)) => {
                 self.eq_qpath(l_path, r_path)
                     && both(lo, ro, |l, r| self.eq_expr(l, r))
                     && over(lf, rf, |l, r| self.eq_expr_field(l, r))
             },
             (&ExprKind::Tup(l_tup), &ExprKind::Tup(r_tup)) => self.eq_exprs(l_tup, r_tup),
-            (&ExprKind::Unary(l_op, ref le), &ExprKind::Unary(r_op, ref re)) => l_op == r_op && self.eq_expr(le, re),
+            (&ExprKind::Unary(l_op, le), &ExprKind::Unary(r_op, re)) => l_op == r_op && self.eq_expr(le, re),
             (&ExprKind::Array(l), &ExprKind::Array(r)) => self.eq_exprs(l, r),
-            (&ExprKind::DropTemps(ref le), &ExprKind::DropTemps(ref re)) => self.eq_expr(le, re),
+            (&ExprKind::DropTemps(le), &ExprKind::DropTemps(re)) => self.eq_expr(le, re),
             _ => false,
         };
         is_eq || self.inner.expr_fallback.as_mut().map_or(false, |f| f(left, right))
@@ -277,7 +272,7 @@ impl HirEqInterExpr<'_, '_, '_> {
     }
 
     fn eq_expr_field(&mut self, left: &ExprField<'_>, right: &ExprField<'_>) -> bool {
-        left.ident.name == right.ident.name && self.eq_expr(&left.expr, &right.expr)
+        left.ident.name == right.ident.name && self.eq_expr(left.expr, right.expr)
     }
 
     fn eq_guard(&mut self, left: &Guard<'_>, right: &Guard<'_>) -> bool {
@@ -308,11 +303,11 @@ impl HirEqInterExpr<'_, '_, '_> {
     /// Checks whether two patterns are the same.
     fn eq_pat(&mut self, left: &Pat<'_>, right: &Pat<'_>) -> bool {
         match (&left.kind, &right.kind) {
-            (&PatKind::Box(ref l), &PatKind::Box(ref r)) => self.eq_pat(l, r),
-            (&PatKind::Struct(ref lp, ref la, ..), &PatKind::Struct(ref rp, ref ra, ..)) => {
+            (&PatKind::Box(l), &PatKind::Box(r)) => self.eq_pat(l, r),
+            (&PatKind::Struct(ref lp, la, ..), &PatKind::Struct(ref rp, ra, ..)) => {
                 self.eq_qpath(lp, rp) && over(la, ra, |l, r| self.eq_pat_field(l, r))
             },
-            (&PatKind::TupleStruct(ref lp, ref la, ls), &PatKind::TupleStruct(ref rp, ref ra, rs)) => {
+            (&PatKind::TupleStruct(ref lp, la, ls), &PatKind::TupleStruct(ref rp, ra, rs)) => {
                 self.eq_qpath(lp, rp) && over(la, ra, |l, r| self.eq_pat(l, r)) && ls == rs
             },
             (&PatKind::Binding(lb, li, _, ref lp), &PatKind::Binding(rb, ri, _, ref rp)) => {
@@ -323,15 +318,13 @@ impl HirEqInterExpr<'_, '_, '_> {
                 eq
             },
             (&PatKind::Path(ref l), &PatKind::Path(ref r)) => self.eq_qpath(l, r),
-            (&PatKind::Lit(ref l), &PatKind::Lit(ref r)) => self.eq_expr(l, r),
-            (&PatKind::Tuple(ref l, ls), &PatKind::Tuple(ref r, rs)) => {
-                ls == rs && over(l, r, |l, r| self.eq_pat(l, r))
-            },
+            (&PatKind::Lit(l), &PatKind::Lit(r)) => self.eq_expr(l, r),
+            (&PatKind::Tuple(l, ls), &PatKind::Tuple(r, rs)) => ls == rs && over(l, r, |l, r| self.eq_pat(l, r)),
             (&PatKind::Range(ref ls, ref le, li), &PatKind::Range(ref rs, ref re, ri)) => {
                 both(ls, rs, |a, b| self.eq_expr(a, b)) && both(le, re, |a, b| self.eq_expr(a, b)) && (li == ri)
             },
-            (&PatKind::Ref(ref le, ref lm), &PatKind::Ref(ref re, ref rm)) => lm == rm && self.eq_pat(le, re),
-            (&PatKind::Slice(ref ls, ref li, ref le), &PatKind::Slice(ref rs, ref ri, ref re)) => {
+            (&PatKind::Ref(le, ref lm), &PatKind::Ref(re, ref rm)) => lm == rm && self.eq_pat(le, re),
+            (&PatKind::Slice(ls, ref li, le), &PatKind::Slice(rs, ref ri, re)) => {
                 over(ls, rs, |l, r| self.eq_pat(l, r))
                     && over(le, re, |l, r| self.eq_pat(l, r))
                     && both(li, ri, |l, r| self.eq_pat(l, r))
@@ -344,10 +337,10 @@ impl HirEqInterExpr<'_, '_, '_> {
     #[allow(clippy::similar_names)]
     fn eq_qpath(&mut self, left: &QPath<'_>, right: &QPath<'_>) -> bool {
         match (left, right) {
-            (&QPath::Resolved(ref lty, ref lpath), &QPath::Resolved(ref rty, ref rpath)) => {
+            (&QPath::Resolved(ref lty, lpath), &QPath::Resolved(ref rty, rpath)) => {
                 both(lty, rty, |l, r| self.eq_ty(l, r)) && self.eq_path(lpath, rpath)
             },
-            (&QPath::TypeRelative(ref lty, ref lseg), &QPath::TypeRelative(ref rty, ref rseg)) => {
+            (&QPath::TypeRelative(lty, lseg), &QPath::TypeRelative(rty, rseg)) => {
                 self.eq_ty(lty, rty) && self.eq_path_segment(lseg, rseg)
             },
             (&QPath::LangItem(llang_item, _), &QPath::LangItem(rlang_item, _)) => llang_item == rlang_item,
@@ -359,14 +352,14 @@ impl HirEqInterExpr<'_, '_, '_> {
         match (left.res, right.res) {
             (Res::Local(l), Res::Local(r)) => l == r || self.locals.get(&l) == Some(&r),
             (Res::Local(_), _) | (_, Res::Local(_)) => false,
-            _ => over(&left.segments, &right.segments, |l, r| self.eq_path_segment(l, r)),
+            _ => over(left.segments, right.segments, |l, r| self.eq_path_segment(l, r)),
         }
     }
 
     fn eq_path_parameters(&mut self, left: &GenericArgs<'_>, right: &GenericArgs<'_>) -> bool {
         if !(left.parenthesized || right.parenthesized) {
-            over(&left.args, &right.args, |l, r| self.eq_generic_arg(l, r)) // FIXME(flip1995): may not work
-                && over(&left.bindings, &right.bindings, |l, r| self.eq_type_binding(l, r))
+            over(left.args, right.args, |l, r| self.eq_generic_arg(l, r)) // FIXME(flip1995): may not work
+                && over(left.bindings, right.bindings, |l, r| self.eq_type_binding(l, r))
         } else if left.parenthesized && right.parenthesized {
             over(left.inputs(), right.inputs(), |l, r| self.eq_ty(l, r))
                 && both(&Some(&left.bindings[0].ty()), &Some(&right.bindings[0].ty()), |l, r| {
@@ -390,8 +383,8 @@ impl HirEqInterExpr<'_, '_, '_> {
     #[allow(clippy::similar_names)]
     fn eq_ty(&mut self, left: &Ty<'_>, right: &Ty<'_>) -> bool {
         match (&left.kind, &right.kind) {
-            (&TyKind::Slice(ref l_vec), &TyKind::Slice(ref r_vec)) => self.eq_ty(l_vec, r_vec),
-            (&TyKind::Array(ref lt, ref ll_id), &TyKind::Array(ref rt, ref rl_id)) => {
+            (&TyKind::Slice(l_vec), &TyKind::Slice(r_vec)) => self.eq_ty(l_vec, r_vec),
+            (&TyKind::Array(lt, ref ll_id), &TyKind::Array(rt, ref rl_id)) => {
                 let cx = self.inner.cx;
                 let eval_const =
                     |body| constant_context(cx, cx.tcx.typeck_body(body)).expr(&cx.tcx.hir().body(body).value);
@@ -404,14 +397,14 @@ impl HirEqInterExpr<'_, '_, '_> {
                 l_rmut.mutbl == r_rmut.mutbl && self.eq_ty(&*l_rmut.ty, &*r_rmut.ty)
             },
             (&TyKind::Path(ref l), &TyKind::Path(ref r)) => self.eq_qpath(l, r),
-            (&TyKind::Tup(ref l), &TyKind::Tup(ref r)) => over(l, r, |l, r| self.eq_ty(l, r)),
+            (&TyKind::Tup(l), &TyKind::Tup(r)) => over(l, r, |l, r| self.eq_ty(l, r)),
             (&TyKind::Infer, &TyKind::Infer) => true,
             _ => false,
         }
     }
 
     fn eq_type_binding(&mut self, left: &TypeBinding<'_>, right: &TypeBinding<'_>) -> bool {
-        left.ident.name == right.ident.name && self.eq_ty(&left.ty(), &right.ty())
+        left.ident.name == right.ident.name && self.eq_ty(left.ty(), right.ty())
     }
 }
 
@@ -540,7 +533,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
             self.hash_stmt(s);
         }
 
-        if let Some(ref e) = b.expr {
+        if let Some(e) = b.expr {
             self.hash_expr(e);
         }
 
@@ -570,7 +563,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
         std::mem::discriminant(&e.kind).hash(&mut self.s);
 
         match e.kind {
-            ExprKind::AddrOf(kind, m, ref e) => {
+            ExprKind::AddrOf(kind, m, e) => {
                 match kind {
                     BorrowKind::Ref => 0,
                     BorrowKind::Raw => 1,
@@ -584,20 +577,20 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                     self.hash_name(i.ident.name);
                 }
             },
-            ExprKind::Assign(ref l, ref r, _) => {
+            ExprKind::Assign(l, r, _) => {
                 self.hash_expr(l);
                 self.hash_expr(r);
             },
-            ExprKind::AssignOp(ref o, ref l, ref r) => {
+            ExprKind::AssignOp(ref o, l, r) => {
                 o.node
                     .hash_stable(&mut self.cx.tcx.get_stable_hashing_context(), &mut self.s);
                 self.hash_expr(l);
                 self.hash_expr(r);
             },
-            ExprKind::Block(ref b, _) => {
+            ExprKind::Block(b, _) => {
                 self.hash_block(b);
             },
-            ExprKind::Binary(op, ref l, ref r) => {
+            ExprKind::Binary(op, l, r) => {
                 op.node
                     .hash_stable(&mut self.cx.tcx.get_stable_hashing_context(), &mut self.s);
                 self.hash_expr(l);
@@ -607,18 +600,18 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 if let Some(i) = i.label {
                     self.hash_name(i.ident.name);
                 }
-                if let Some(ref j) = *j {
+                if let Some(j) = *j {
                     self.hash_expr(&*j);
                 }
             },
-            ExprKind::Box(ref e) | ExprKind::DropTemps(ref e) | ExprKind::Yield(ref e, _) => {
+            ExprKind::Box(e) | ExprKind::DropTemps(e) | ExprKind::Yield(e, _) => {
                 self.hash_expr(e);
             },
-            ExprKind::Call(ref fun, args) => {
+            ExprKind::Call(fun, args) => {
                 self.hash_expr(fun);
                 self.hash_exprs(args);
             },
-            ExprKind::Cast(ref e, ref ty) | ExprKind::Type(ref e, ref ty) => {
+            ExprKind::Cast(e, ty) | ExprKind::Type(e, ty) => {
                 self.hash_expr(e);
                 self.hash_ty(ty);
             },
@@ -631,15 +624,15 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 // closures inherit TypeckResults
                 self.hash_expr(&self.cx.tcx.hir().body(eid).value);
             },
-            ExprKind::Field(ref e, ref f) => {
+            ExprKind::Field(e, ref f) => {
                 self.hash_expr(e);
                 self.hash_name(f.name);
             },
-            ExprKind::Index(ref a, ref i) => {
+            ExprKind::Index(a, i) => {
                 self.hash_expr(a);
                 self.hash_expr(i);
             },
-            ExprKind::InlineAsm(ref asm) => {
+            ExprKind::InlineAsm(asm) => {
                 for piece in asm.template {
                     match piece {
                         InlineAsmTemplatePiece::String(s) => s.hash(&mut self.s),
@@ -694,22 +687,22 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
             ExprKind::Lit(ref l) => {
                 l.node.hash(&mut self.s);
             },
-            ExprKind::Loop(ref b, ref i, ..) => {
+            ExprKind::Loop(b, ref i, ..) => {
                 self.hash_block(b);
                 if let Some(i) = *i {
                     self.hash_name(i.ident.name);
                 }
             },
-            ExprKind::If(ref cond, ref then, ref else_opt) => {
+            ExprKind::If(cond, then, ref else_opt) => {
                 let c: fn(_, _, _) -> _ = ExprKind::If;
                 c.hash(&mut self.s);
                 self.hash_expr(cond);
-                self.hash_expr(&**then);
-                if let Some(ref e) = *else_opt {
+                self.hash_expr(then);
+                if let Some(e) = *else_opt {
                     self.hash_expr(e);
                 }
             },
-            ExprKind::Match(ref e, arms, ref s) => {
+            ExprKind::Match(e, arms, ref s) => {
                 self.hash_expr(e);
 
                 for arm in arms {
@@ -717,39 +710,39 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                     if let Some(ref e) = arm.guard {
                         self.hash_guard(e);
                     }
-                    self.hash_expr(&arm.body);
+                    self.hash_expr(arm.body);
                 }
 
                 s.hash(&mut self.s);
             },
-            ExprKind::MethodCall(ref path, ref _tys, args, ref _fn_span) => {
+            ExprKind::MethodCall(path, ref _tys, args, ref _fn_span) => {
                 self.hash_name(path.ident.name);
                 self.hash_exprs(args);
             },
             ExprKind::ConstBlock(ref l_id) => {
                 self.hash_body(l_id.body);
             },
-            ExprKind::Repeat(ref e, ref l_id) => {
+            ExprKind::Repeat(e, ref l_id) => {
                 self.hash_expr(e);
                 self.hash_body(l_id.body);
             },
             ExprKind::Ret(ref e) => {
-                if let Some(ref e) = *e {
+                if let Some(e) = *e {
                     self.hash_expr(e);
                 }
             },
             ExprKind::Path(ref qpath) => {
                 self.hash_qpath(qpath);
             },
-            ExprKind::Struct(ref path, fields, ref expr) => {
+            ExprKind::Struct(path, fields, ref expr) => {
                 self.hash_qpath(path);
 
                 for f in fields {
                     self.hash_name(f.ident.name);
-                    self.hash_expr(&f.expr);
+                    self.hash_expr(f.expr);
                 }
 
-                if let Some(ref e) = *expr {
+                if let Some(e) = *expr {
                     self.hash_expr(e);
                 }
             },
@@ -759,7 +752,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
             ExprKind::Array(v) => {
                 self.hash_exprs(v);
             },
-            ExprKind::Unary(lop, ref le) => {
+            ExprKind::Unary(lop, le) => {
                 lop.hash_stable(&mut self.cx.tcx.get_stable_hashing_context(), &mut self.s);
                 self.hash_expr(le);
             },
@@ -778,10 +771,10 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
 
     pub fn hash_qpath(&mut self, p: &QPath<'_>) {
         match *p {
-            QPath::Resolved(_, ref path) => {
+            QPath::Resolved(_, path) => {
                 self.hash_path(path);
             },
-            QPath::TypeRelative(_, ref path) => {
+            QPath::TypeRelative(_, path) => {
                 self.hash_name(path.ident.name);
             },
             QPath::LangItem(lang_item, ..) => {
@@ -875,7 +868,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
         match &b.kind {
             StmtKind::Local(local) => {
                 self.hash_pat(local.pat);
-                if let Some(ref init) = local.init {
+                if let Some(init) = local.init {
                     self.hash_expr(init);
                 }
             },
@@ -888,7 +881,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
 
     pub fn hash_guard(&mut self, g: &Guard<'_>) {
         match g {
-            Guard::If(ref expr) | Guard::IfLet(_, ref expr) => {
+            Guard::If(expr) | Guard::IfLet(_, expr) => {
                 self.hash_expr(expr);
             },
         }
@@ -921,25 +914,25 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 self.hash_body(anon_const.body);
             },
             TyKind::Ptr(ref mut_ty) => {
-                self.hash_ty(&mut_ty.ty);
+                self.hash_ty(mut_ty.ty);
                 mut_ty.mutbl.hash(&mut self.s);
             },
             TyKind::Rptr(lifetime, ref mut_ty) => {
                 self.hash_lifetime(lifetime);
-                self.hash_ty(&mut_ty.ty);
+                self.hash_ty(mut_ty.ty);
                 mut_ty.mutbl.hash(&mut self.s);
             },
             TyKind::BareFn(bfn) => {
                 bfn.unsafety.hash(&mut self.s);
                 bfn.abi.hash(&mut self.s);
                 for arg in bfn.decl.inputs {
-                    self.hash_ty(&arg);
+                    self.hash_ty(arg);
                 }
                 match bfn.decl.output {
                     FnRetTy::DefaultReturn(_) => {
                         ().hash(&mut self.s);
                     },
-                    FnRetTy::Return(ref ty) => {
+                    FnRetTy::Return(ty) => {
                         self.hash_ty(ty);
                     },
                 }
@@ -951,8 +944,8 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 }
             },
             TyKind::Path(ref qpath) => match qpath {
-                QPath::Resolved(ref maybe_ty, ref path) => {
-                    if let Some(ref ty) = maybe_ty {
+                QPath::Resolved(ref maybe_ty, path) => {
+                    if let Some(ty) = maybe_ty {
                         self.hash_ty(ty);
                     }
                     for segment in path.segments {
@@ -960,7 +953,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                         self.hash_generic_args(segment.args().args);
                     }
                 },
-                QPath::TypeRelative(ref ty, ref segment) => {
+                QPath::TypeRelative(ty, segment) => {
                     self.hash_ty(ty);
                     segment.ident.name.hash(&mut self.s);
                 },
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 2b9b214daa7..610011af059 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -328,7 +328,7 @@ pub fn is_trait_method(cx: &LateContext<'_>, expr: &Expr<'_>, diag_item: Symbol)
 
 /// Checks if an expression references a variable of the given name.
 pub fn match_var(expr: &Expr<'_>, var: Symbol) -> bool {
-    if let ExprKind::Path(QPath::Resolved(None, ref path)) = expr.kind {
+    if let ExprKind::Path(QPath::Resolved(None, path)) = expr.kind {
         if let [p] = path.segments {
             return p.ident.name == var;
         }
@@ -338,8 +338,8 @@ pub fn match_var(expr: &Expr<'_>, var: Symbol) -> bool {
 
 pub fn last_path_segment<'tcx>(path: &QPath<'tcx>) -> &'tcx PathSegment<'tcx> {
     match *path {
-        QPath::Resolved(_, ref path) => path.segments.last().expect("A path must have at least one segment"),
-        QPath::TypeRelative(_, ref seg) => seg,
+        QPath::Resolved(_, path) => path.segments.last().expect("A path must have at least one segment"),
+        QPath::TypeRelative(_, seg) => seg,
         QPath::LangItem(..) => panic!("last_path_segment: lang item has no path segments"),
     }
 }
@@ -367,8 +367,8 @@ pub fn get_qpath_generic_tys(path: &QPath<'tcx>) -> impl Iterator<Item = &'tcx h
 
 pub fn single_segment_path<'tcx>(path: &QPath<'tcx>) -> Option<&'tcx PathSegment<'tcx>> {
     match *path {
-        QPath::Resolved(_, ref path) => path.segments.get(0),
-        QPath::TypeRelative(_, ref seg) => Some(seg),
+        QPath::Resolved(_, path) => path.segments.get(0),
+        QPath::TypeRelative(_, seg) => Some(seg),
         QPath::LangItem(..) => None,
     }
 }
@@ -388,8 +388,8 @@ pub fn single_segment_path<'tcx>(path: &QPath<'tcx>) -> Option<&'tcx PathSegment
 /// ```
 pub fn match_qpath(path: &QPath<'_>, segments: &[&str]) -> bool {
     match *path {
-        QPath::Resolved(_, ref path) => match_path(path, segments),
-        QPath::TypeRelative(ref ty, ref segment) => match ty.kind {
+        QPath::Resolved(_, path) => match_path(path, segments),
+        QPath::TypeRelative(ty, segment) => match ty.kind {
             TyKind::Path(ref inner_path) => {
                 if let [prefix @ .., end] = segments {
                     if match_qpath(inner_path, prefix) {
@@ -457,7 +457,7 @@ pub fn match_path(path: &Path<'_>, segments: &[&str]) -> bool {
 
 /// If the expression is a path to a local, returns the canonical `HirId` of the local.
 pub fn path_to_local(expr: &Expr<'_>) -> Option<HirId> {
-    if let ExprKind::Path(QPath::Resolved(None, ref path)) = expr.kind {
+    if let ExprKind::Path(QPath::Resolved(None, path)) = expr.kind {
         if let Res::Local(id) = path.res {
             return Some(id);
         }
@@ -661,12 +661,12 @@ pub fn method_chain_args<'a>(expr: &'a Expr<'_>, methods: &[&str]) -> Option<Vec
     let mut matched = Vec::with_capacity(methods.len());
     for method_name in methods.iter().rev() {
         // method chains are stored last -> first
-        if let ExprKind::MethodCall(ref path, _, ref args, _) = current.kind {
+        if let ExprKind::MethodCall(path, _, args, _) = current.kind {
             if path.ident.name.as_str() == *method_name {
                 if args.iter().any(|e| e.span.from_expansion()) {
                     return None;
                 }
-                matched.push(&**args); // build up `matched` backwards
+                matched.push(args); // build up `matched` backwards
                 current = &args[0] // go to parent expression
             } else {
                 return None;
@@ -712,7 +712,7 @@ pub fn get_pat_name(pat: &Pat<'_>) -> Option<Symbol> {
     match pat.kind {
         PatKind::Binding(.., ref spname, _) => Some(spname.name),
         PatKind::Path(ref qpath) => single_segment_path(qpath).map(|ps| ps.ident.name),
-        PatKind::Box(ref p) | PatKind::Ref(ref p, _) => get_pat_name(&*p),
+        PatKind::Box(p) | PatKind::Ref(p, _) => get_pat_name(&*p),
         _ => None,
     }
 }
@@ -854,7 +854,7 @@ pub fn get_enclosing_block<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Optio
             kind: ImplItemKind::Fn(_, eid),
             ..
         }) => match cx.tcx.hir().body(eid).value.kind {
-            ExprKind::Block(ref block, _) => Some(block),
+            ExprKind::Block(block, _) => Some(block),
             _ => None,
         },
         _ => None,
@@ -1028,7 +1028,7 @@ pub fn return_ty<'tcx>(cx: &LateContext<'tcx>, fn_item: hir::HirId) -> Ty<'tcx>
 
 /// Checks if an expression is constructing a tuple-like enum variant or struct
 pub fn is_ctor_or_promotable_const_function(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
-    if let ExprKind::Call(ref fun, _) = expr.kind {
+    if let ExprKind::Call(fun, _) = expr.kind {
         if let ExprKind::Path(ref qp) = fun.kind {
             let res = cx.qpath_res(qp, fun.hir_id);
             return match res {
@@ -1058,21 +1058,21 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
     match pat.kind {
         PatKind::Wild => false,
         PatKind::Binding(_, _, _, pat) => pat.map_or(false, |pat| is_refutable(cx, pat)),
-        PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => is_refutable(cx, pat),
+        PatKind::Box(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat),
         PatKind::Lit(..) | PatKind::Range(..) => true,
         PatKind::Path(ref qpath) => is_enum_variant(cx, qpath, pat.hir_id),
-        PatKind::Or(ref pats) => {
+        PatKind::Or(pats) => {
             // TODO: should be the honest check, that pats is exhaustive set
             are_refutable(cx, pats.iter().map(|pat| &**pat))
         },
-        PatKind::Tuple(ref pats, _) => are_refutable(cx, pats.iter().map(|pat| &**pat)),
-        PatKind::Struct(ref qpath, ref fields, _) => {
+        PatKind::Tuple(pats, _) => are_refutable(cx, pats.iter().map(|pat| &**pat)),
+        PatKind::Struct(ref qpath, fields, _) => {
             is_enum_variant(cx, qpath, pat.hir_id) || are_refutable(cx, fields.iter().map(|field| &*field.pat))
         },
-        PatKind::TupleStruct(ref qpath, ref pats, _) => {
+        PatKind::TupleStruct(ref qpath, pats, _) => {
             is_enum_variant(cx, qpath, pat.hir_id) || are_refutable(cx, pats.iter().map(|pat| &**pat))
         },
-        PatKind::Slice(ref head, ref middle, ref tail) => {
+        PatKind::Slice(head, ref middle, tail) => {
             match &cx.typeck_results().node_type(pat.hir_id).kind() {
                 rustc_ty::Slice(..) => {
                     // [..] is the only irrefutable slice pattern.
@@ -1111,7 +1111,7 @@ pub fn is_automatically_derived(attrs: &[ast::Attribute]) -> bool {
 /// Ie. `x`, `{ x }` and `{{{{ x }}}}` all give `x`. `{ x; y }` and `{}` return
 /// themselves.
 pub fn remove_blocks<'tcx>(mut expr: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
-    while let ExprKind::Block(ref block, ..) = expr.kind {
+    while let ExprKind::Block(block, ..) = expr.kind {
         match (block.stmts.is_empty(), block.expr.as_ref()) {
             (true, Some(e)) => expr = e,
             _ => break,
@@ -1130,7 +1130,7 @@ pub fn is_self(slf: &Param<'_>) -> bool {
 
 pub fn is_self_ty(slf: &hir::Ty<'_>) -> bool {
     if_chain! {
-        if let TyKind::Path(QPath::Resolved(None, ref path)) = slf.kind;
+        if let TyKind::Path(QPath::Resolved(None, path)) = slf.kind;
         if let Res::SelfTy(..) = path.res;
         then {
             return true
@@ -1148,7 +1148,7 @@ pub fn iter_input_pats<'tcx>(decl: &FnDecl<'_>, body: &'tcx Body<'_>) -> impl It
 pub fn is_try<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
     fn is_ok(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
         if_chain! {
-            if let PatKind::TupleStruct(ref path, ref pat, None) = arm.pat.kind;
+            if let PatKind::TupleStruct(ref path, pat, None) = arm.pat.kind;
             if is_lang_ctor(cx, path, ResultOk);
             if let PatKind::Binding(_, hir_id, _, None) = pat[0].kind;
             if path_to_local_id(arm.body, hir_id);
@@ -1167,7 +1167,7 @@ pub fn is_try<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'tcx>) -> Option<&'tc
         }
     }
 
-    if let ExprKind::Match(_, ref arms, ref source) = expr.kind {
+    if let ExprKind::Match(_, arms, ref source) = expr.kind {
         // desugared from a `?` operator
         if let MatchSource::TryDesugar = *source {
             return Some(expr);
@@ -1254,7 +1254,7 @@ pub fn match_function_call<'tcx>(
     path: &[&str],
 ) -> Option<&'tcx [Expr<'tcx>]> {
     if_chain! {
-        if let ExprKind::Call(ref fun, args) = expr.kind;
+        if let ExprKind::Call(fun, args) = expr.kind;
         if let ExprKind::Path(ref qpath) = fun.kind;
         if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
         if match_def_path(cx, fun_def_id, path);
@@ -1316,15 +1316,15 @@ pub fn if_sequence<'tcx>(mut expr: &'tcx Expr<'tcx>) -> (Vec<&'tcx Expr<'tcx>>,
     let mut conds = Vec::new();
     let mut blocks: Vec<&Block<'_>> = Vec::new();
 
-    while let ExprKind::If(ref cond, ref then_expr, ref else_expr) = expr.kind {
-        conds.push(&**cond);
-        if let ExprKind::Block(ref block, _) = then_expr.kind {
+    while let ExprKind::If(cond, then_expr, ref else_expr) = expr.kind {
+        conds.push(cond);
+        if let ExprKind::Block(block, _) = then_expr.kind {
             blocks.push(block);
         } else {
             panic!("ExprKind::If node is not an ExprKind::Block");
         }
 
-        if let Some(ref else_expr) = *else_expr {
+        if let Some(else_expr) = *else_expr {
             expr = else_expr;
         } else {
             break;
@@ -1333,8 +1333,8 @@ pub fn if_sequence<'tcx>(mut expr: &'tcx Expr<'tcx>) -> (Vec<&'tcx Expr<'tcx>>,
 
     // final `else {..}`
     if !blocks.is_empty() {
-        if let ExprKind::Block(ref block, _) = expr.kind {
-            blocks.push(&**block);
+        if let ExprKind::Block(block, _) = expr.kind {
+            blocks.push(block);
         }
     }
 
@@ -1383,7 +1383,7 @@ pub fn must_use_attr(attrs: &[Attribute]) -> Option<&Attribute> {
 // check if expr is calling method or function with #[must_use] attribute
 pub fn is_must_use_func_call(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     let did = match expr.kind {
-        ExprKind::Call(ref path, _) => if_chain! {
+        ExprKind::Call(path, _) => if_chain! {
             if let ExprKind::Path(ref qpath) = path.kind;
             if let def::Res::Def(_, did) = cx.qpath_res(qpath, path.hir_id);
             then {
@@ -1396,7 +1396,7 @@ pub fn is_must_use_func_call(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
         _ => None,
     };
 
-    did.map_or(false, |did| must_use_attr(&cx.tcx.get_attrs(did)).is_some())
+    did.map_or(false, |did| must_use_attr(cx.tcx.get_attrs(did)).is_some())
 }
 
 /// Gets the node where an expression is either used, or it's type is unified with another branch.
diff --git a/clippy_utils/src/numeric_literal.rs b/clippy_utils/src/numeric_literal.rs
index 268bc5b3205..546706d51d7 100644
--- a/clippy_utils/src/numeric_literal.rs
+++ b/clippy_utils/src/numeric_literal.rs
@@ -52,7 +52,7 @@ impl<'a> NumericLiteral<'a> {
 
     pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
         if lit_kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
-            let (unsuffixed, suffix) = split_suffix(&src, lit_kind);
+            let (unsuffixed, suffix) = split_suffix(src, lit_kind);
             let float = matches!(lit_kind, LitKind::Float(..));
             Some(NumericLiteral::new(unsuffixed, suffix, float))
         } else {
diff --git a/clippy_utils/src/ptr.rs b/clippy_utils/src/ptr.rs
index 5885cc83560..791688cd194 100644
--- a/clippy_utils/src/ptr.rs
+++ b/clippy_utils/src/ptr.rs
@@ -55,7 +55,7 @@ impl<'a, 'tcx> Visitor<'tcx> for PtrCloneVisitor<'a, 'tcx> {
         if self.abort {
             return;
         }
-        if let ExprKind::MethodCall(ref seg, _, ref args, _) = expr.kind {
+        if let ExprKind::MethodCall(seg, _, args, _) = expr.kind {
             if args.len() == 1 && match_var(&args[0], self.name) {
                 if seg.ident.name.as_str() == "capacity" {
                     self.abort = true;
@@ -79,5 +79,5 @@ impl<'a, 'tcx> Visitor<'tcx> for PtrCloneVisitor<'a, 'tcx> {
 }
 
 fn get_binding_name(arg: &Param<'_>) -> Option<Symbol> {
-    get_pat_name(&arg.pat)
+    get_pat_name(arg.pat)
 }
diff --git a/clippy_utils/src/qualify_min_const_fn.rs b/clippy_utils/src/qualify_min_const_fn.rs
index a08dcf19e5b..0e6ead675c2 100644
--- a/clippy_utils/src/qualify_min_const_fn.rs
+++ b/clippy_utils/src/qualify_min_const_fn.rs
@@ -255,7 +255,7 @@ fn check_place(tcx: TyCtxt<'tcx>, place: Place<'tcx>, span: Span, body: &Body<'t
         cursor = proj_base;
         match elem {
             ProjectionElem::Field(..) => {
-                let base_ty = Place::ty_from(place.local, &proj_base, body, tcx).ty;
+                let base_ty = Place::ty_from(place.local, proj_base, body, tcx).ty;
                 if let Some(def) = base_ty.ty_adt_def() {
                     // No union field accesses in `const fn`
                     if def.is_union() {
diff --git a/clippy_utils/src/ty.rs b/clippy_utils/src/ty.rs
index c36e215f184..a92d3be5d3c 100644
--- a/clippy_utils/src/ty.rs
+++ b/clippy_utils/src/ty.rs
@@ -142,21 +142,18 @@ pub fn has_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
 // Returns whether the type has #[must_use] attribute
 pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
     match ty.kind() {
-        ty::Adt(ref adt, _) => must_use_attr(&cx.tcx.get_attrs(adt.did)).is_some(),
-        ty::Foreign(ref did) => must_use_attr(&cx.tcx.get_attrs(*did)).is_some(),
-        ty::Slice(ref ty)
-        | ty::Array(ref ty, _)
-        | ty::RawPtr(ty::TypeAndMut { ref ty, .. })
-        | ty::Ref(_, ref ty, _) => {
+        ty::Adt(adt, _) => must_use_attr(cx.tcx.get_attrs(adt.did)).is_some(),
+        ty::Foreign(ref did) => must_use_attr(cx.tcx.get_attrs(*did)).is_some(),
+        ty::Slice(ty) | ty::Array(ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
             // for the Array case we don't need to care for the len == 0 case
             // because we don't want to lint functions returning empty arrays
             is_must_use_ty(cx, *ty)
         },
-        ty::Tuple(ref substs) => substs.types().any(|ty| is_must_use_ty(cx, ty)),
+        ty::Tuple(substs) => substs.types().any(|ty| is_must_use_ty(cx, ty)),
         ty::Opaque(ref def_id, _) => {
             for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
                 if let ty::PredicateKind::Trait(trait_predicate, _) = predicate.kind().skip_binder() {
-                    if must_use_attr(&cx.tcx.get_attrs(trait_predicate.trait_ref.def_id)).is_some() {
+                    if must_use_attr(cx.tcx.get_attrs(trait_predicate.trait_ref.def_id)).is_some() {
                         return true;
                     }
                 }
@@ -166,7 +163,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         ty::Dynamic(binder, _) => {
             for predicate in binder.iter() {
                 if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate.skip_binder() {
-                    if must_use_attr(&cx.tcx.get_attrs(trait_ref.def_id)).is_some() {
+                    if must_use_attr(cx.tcx.get_attrs(trait_ref.def_id)).is_some() {
                         return true;
                     }
                 }
@@ -305,7 +302,7 @@ pub fn type_is_unsafe_function<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bo
 /// Returns the base type for HIR references and pointers.
 pub fn walk_ptrs_hir_ty<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
     match ty.kind {
-        TyKind::Ptr(ref mut_ty) | TyKind::Rptr(_, ref mut_ty) => walk_ptrs_hir_ty(&mut_ty.ty),
+        TyKind::Ptr(ref mut_ty) | TyKind::Rptr(_, ref mut_ty) => walk_ptrs_hir_ty(mut_ty.ty),
         _ => ty,
     }
 }
diff --git a/clippy_utils/src/usage.rs b/clippy_utils/src/usage.rs
index 650b70c63af..31d5a888c69 100644
--- a/clippy_utils/src/usage.rs
+++ b/clippy_utils/src/usage.rs
@@ -71,12 +71,12 @@ impl<'tcx> Delegate<'tcx> for MutVarsDelegate {
 
     fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, bk: ty::BorrowKind) {
         if let ty::BorrowKind::MutBorrow = bk {
-            self.update(&cmt)
+            self.update(cmt)
         }
     }
 
     fn mutate(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId) {
-        self.update(&cmt)
+        self.update(cmt)
     }
 
     fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}