Use for_each_expr in place of some visitors

clippy_lints/src/blocks_in_if_conditions.rs

@@ -3,10 +3,11 @@ use clippy_utils::get_parent_expr;
 use clippy_utils::higher;
 use clippy_utils::source::snippet_block_with_applicability;
 use clippy_utils::ty::implements_trait;
+use clippy_utils::visitors::{for_each_expr, Descend};
+use core::ops::ControlFlow;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::intravisit::{walk_expr, Visitor};
+use rustc_hir::{BlockCheckMode, Expr, ExprKind};
-use rustc_hir::{BlockCheckMode, Closure, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -44,39 +45,6 @@ declare_clippy_lint! {
 
 declare_lint_pass!(BlocksInIfConditions => [BLOCKS_IN_IF_CONDITIONS]);
 
-struct ExVisitor<'a, 'tcx> {
-    found_block: Option<&'tcx Expr<'tcx>>,
-    cx: &'a LateContext<'tcx>,
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for ExVisitor<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
-        if let ExprKind::Closure(&Closure { body, .. }) = expr.kind {
-            // do not lint if the closure is called using an iterator (see #1141)
-            if_chain! {
-                if let Some(parent) = get_parent_expr(self.cx, expr);
-                if let ExprKind::MethodCall(_, self_arg, ..) = &parent.kind;
-                let caller = self.cx.typeck_results().expr_ty(self_arg);
-                if let Some(iter_id) = self.cx.tcx.get_diagnostic_item(sym::Iterator);
-                if implements_trait(self.cx, caller, iter_id, &[]);
-                then {
-                    return;
-                }
-            }
-
-            let body = self.cx.tcx.hir().body(body);
-            let ex = &body.value;
-            if let ExprKind::Block(block, _) = ex.kind {
-                if !body.value.span.from_expansion() && !block.stmts.is_empty() {
-                    self.found_block = Some(ex);
-                    return;
-                }
-            }
-        }
-        walk_expr(self, expr);
-    }
-}
-
 const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition";
 const COMPLEX_BLOCK_MESSAGE: &str = "in an `if` condition, avoid complex blocks or closures with blocks; \
                                     instead, move the block or closure higher and bind it with a `let`";
@@ -144,11 +112,31 @@ impl<'tcx> LateLintPass<'tcx> for BlocksInIfConditions {
                     }
                 }
             } else {
-                let mut visitor = ExVisitor { found_block: None, cx };
+                let _: Option<!> = for_each_expr(cond, |e| {
-                walk_expr(&mut visitor, cond);
+                    if let ExprKind::Closure(closure) = e.kind {
-                if let Some(block) = visitor.found_block {
+                        // do not lint if the closure is called using an iterator (see #1141)
-                    span_lint(cx, BLOCKS_IN_IF_CONDITIONS, block.span, COMPLEX_BLOCK_MESSAGE);
+                        if_chain! {
-                }
+                            if let Some(parent) = get_parent_expr(cx, e);
+                            if let ExprKind::MethodCall(_, self_arg, _, _) = &parent.kind;
+                            let caller = cx.typeck_results().expr_ty(self_arg);
+                            if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
+                            if implements_trait(cx, caller, iter_id, &[]);
+                            then {
+                                return ControlFlow::Continue(Descend::No);
+                            }
+                        }
+
+                        let body = cx.tcx.hir().body(closure.body);
+                        let ex = &body.value;
+                        if let ExprKind::Block(block, _) = ex.kind {
+                            if !body.value.span.from_expansion() && !block.stmts.is_empty() {
+                                span_lint(cx, BLOCKS_IN_IF_CONDITIONS, ex.span, COMPLEX_BLOCK_MESSAGE);
+                                return ControlFlow::Continue(Descend::No);
+                            }
+                        }
+                    }
+                    ControlFlow::Continue(Descend::Yes)
+                });
             }
         }
     }

clippy_lints/src/cognitive_complexity.rs

@@ -3,10 +3,12 @@
 use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::LimitStack;
+use core::ops::ControlFlow;
 use rustc_ast::ast::Attribute;
-use rustc_hir::intravisit::{walk_expr, FnKind, Visitor};
+use rustc_hir::intravisit::FnKind;
-use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId};
+use rustc_hir::{Body, ExprKind, FnDecl, HirId};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Span;
@@ -61,11 +63,27 @@ impl CognitiveComplexity {
             return;
         }
 
-        let expr = &body.value;
+        let expr = body.value;
+
+        let mut cc = 1u64;
+        let mut returns = 0u64;
+        let _: Option<!> = for_each_expr(expr, |e| {
+            match e.kind {
+                ExprKind::If(_, _, _) => {
+                    cc += 1;
+                },
+                ExprKind::Match(_, arms, _) => {
+                    if arms.len() > 1 {
+                        cc += 1;
+                    }
+                    cc += arms.iter().filter(|arm| arm.guard.is_some()).count() as u64;
+                },
+                ExprKind::Ret(_) => returns += 1,
+                _ => {},
+            }
+            ControlFlow::Continue(())
+        });
 
-        let mut helper = CcHelper { cc: 1, returns: 0 };
-        helper.visit_expr(expr);
-        let CcHelper { cc, returns } = helper;
         let ret_ty = cx.typeck_results().node_type(expr.hir_id);
         let ret_adjust = if is_type_diagnostic_item(cx, ret_ty, sym::Result) {
             returns
@@ -74,13 +92,12 @@ impl CognitiveComplexity {
             (returns / 2)
         };
 
-        let mut rust_cc = cc;
         // prevent degenerate cases where unreachable code contains `return` statements
-        if rust_cc >= ret_adjust {
+        if cc >= ret_adjust {
-            rust_cc -= ret_adjust;
+            cc -= ret_adjust;
         }
 
-        if rust_cc > self.limit.limit() {
+        if cc > self.limit.limit() {
             let fn_span = match kind {
                 FnKind::ItemFn(ident, _, _) | FnKind::Method(ident, _) => ident.span,
                 FnKind::Closure => {
@@ -107,7 +124,7 @@ impl CognitiveComplexity {
                 COGNITIVE_COMPLEXITY,
                 fn_span,
                 &format!(
-                    "the function has a cognitive complexity of ({rust_cc}/{})",
+                    "the function has a cognitive complexity of ({cc}/{})",
                     self.limit.limit()
                 ),
                 None,
@@ -140,27 +157,3 @@ impl<'tcx> LateLintPass<'tcx> for CognitiveComplexity {
         self.limit.pop_attrs(cx.sess(), attrs, "cognitive_complexity");
     }
 }
-
-struct CcHelper {
-    cc: u64,
-    returns: u64,
-}
-
-impl<'tcx> Visitor<'tcx> for CcHelper {
-    fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
-        walk_expr(self, e);
-        match e.kind {
-            ExprKind::If(_, _, _) => {
-                self.cc += 1;
-            },
-            ExprKind::Match(_, arms, _) => {
-                if arms.len() > 1 {
-                    self.cc += 1;
-                }
-                self.cc += arms.iter().filter(|arm| arm.guard.is_some()).count() as u64;
-            },
-            ExprKind::Ret(_) => self.returns += 1,
-            _ => {},
-        }
-    }
-}

clippy_lints/src/functions/must_use.rs

@@ -1,7 +1,7 @@
 use rustc_ast::ast::Attribute;
 use rustc_errors::Applicability;
 use rustc_hir::def_id::{DefIdSet, LocalDefId};
-use rustc_hir::{self as hir, def::Res, intravisit, QPath};
+use rustc_hir::{self as hir, def::Res, QPath};
 use rustc_lint::{LateContext, LintContext};
 use rustc_middle::{
     lint::in_external_macro,
@@ -13,8 +13,11 @@ use clippy_utils::attrs::is_proc_macro;
 use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_then};
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::is_must_use_ty;
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{match_def_path, return_ty, trait_ref_of_method};
 
+use core::ops::ControlFlow;
+
 use super::{DOUBLE_MUST_USE, MUST_USE_CANDIDATE, MUST_USE_UNIT};
 
 pub(super) fn check_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
@@ -200,63 +203,6 @@ fn is_mutable_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span, tys: &m
     }
 }
 
-struct StaticMutVisitor<'a, 'tcx> {
-    cx: &'a LateContext<'tcx>,
-    mutates_static: bool,
-}
-
-impl<'a, 'tcx> intravisit::Visitor<'tcx> for StaticMutVisitor<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-        use hir::ExprKind::{AddrOf, Assign, AssignOp, Call, MethodCall};
-
-        if self.mutates_static {
-            return;
-        }
-        match expr.kind {
-            Call(_, args) => {
-                let mut tys = DefIdSet::default();
-                for arg in args {
-                    if self.cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
-                        && is_mutable_ty(
-                            self.cx,
-                            self.cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg),
-                            arg.span,
-                            &mut tys,
-                        )
-                        && is_mutated_static(arg)
-                    {
-                        self.mutates_static = true;
-                        return;
-                    }
-                    tys.clear();
-                }
-            },
-            MethodCall(_, receiver, args, _) => {
-                let mut tys = DefIdSet::default();
-                for arg in std::iter::once(receiver).chain(args.iter()) {
-                    if self.cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
-                        && is_mutable_ty(
-                            self.cx,
-                            self.cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg),
-                            arg.span,
-                            &mut tys,
-                        )
-                        && is_mutated_static(arg)
-                    {
-                        self.mutates_static = true;
-                        return;
-                    }
-                    tys.clear();
-                }
-            },
-            Assign(target, ..) | AssignOp(_, target, _) | AddrOf(_, hir::Mutability::Mut, target) => {
-                self.mutates_static |= is_mutated_static(target);
-            },
-            _ => {},
-        }
-    }
-}
-
 fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
     use hir::ExprKind::{Field, Index, Path};
 
@@ -269,10 +215,53 @@ fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
 }
 
 fn mutates_static<'tcx>(cx: &LateContext<'tcx>, body: &'tcx hir::Body<'_>) -> bool {
-    let mut v = StaticMutVisitor {
+    for_each_expr(body.value, |e| {
-        cx,
+        use hir::ExprKind::{AddrOf, Assign, AssignOp, Call, MethodCall};
-        mutates_static: false,
+
-    };
+        match e.kind {
-    intravisit::walk_expr(&mut v, body.value);
+            Call(_, args) => {
-    v.mutates_static
+                let mut tys = DefIdSet::default();
+                for arg in args {
+                    if cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
+                        && is_mutable_ty(
+                            cx,
+                            cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg),
+                            arg.span,
+                            &mut tys,
+                        )
+                        && is_mutated_static(arg)
+                    {
+                        return ControlFlow::Break(());
+                    }
+                    tys.clear();
+                }
+                ControlFlow::Continue(())
+            },
+            MethodCall(_, receiver, args, _) => {
+                let mut tys = DefIdSet::default();
+                for arg in std::iter::once(receiver).chain(args.iter()) {
+                    if cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
+                        && is_mutable_ty(
+                            cx,
+                            cx.tcx.typeck(arg.hir_id.owner.def_id).expr_ty(arg),
+                            arg.span,
+                            &mut tys,
+                        )
+                        && is_mutated_static(arg)
+                    {
+                        return ControlFlow::Break(());
+                    }
+                    tys.clear();
+                }
+                ControlFlow::Continue(())
+            },
+            Assign(target, ..) | AssignOp(_, target, _) | AddrOf(_, hir::Mutability::Mut, target)
+                if is_mutated_static(target) =>
+            {
+                ControlFlow::Break(())
+            },
+            _ => ControlFlow::Continue(()),
+        }
+    })
+    .is_some()
 }

clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs

@@ -5,8 +5,11 @@ use rustc_span::def_id::LocalDefId;
 
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::type_is_unsafe_function;
+use clippy_utils::visitors::for_each_expr_with_closures;
 use clippy_utils::{iter_input_pats, path_to_local};
 
+use core::ops::ControlFlow;
+
 use super::NOT_UNSAFE_PTR_ARG_DEREF;
 
 pub(super) fn check_fn<'tcx>(
@@ -39,21 +42,34 @@ fn check_raw_ptr<'tcx>(
     body: &'tcx hir::Body<'tcx>,
     def_id: LocalDefId,
 ) {
-    let expr = &body.value;
     if unsafety == hir::Unsafety::Normal && cx.access_levels.is_exported(def_id) {
         let raw_ptrs = iter_input_pats(decl, body)
             .filter_map(|arg| raw_ptr_arg(cx, arg))
             .collect::<HirIdSet>();
 
         if !raw_ptrs.is_empty() {
-            let typeck_results = cx.tcx.typeck_body(body.id());
+            let typeck = cx.tcx.typeck_body(body.id());
-            let mut v = DerefVisitor {
+            let _: Option<!> = for_each_expr_with_closures(cx, body.value, |e| {
-                cx,
+                match e.kind {
-                ptrs: raw_ptrs,
+                    hir::ExprKind::Call(f, args) if type_is_unsafe_function(cx, typeck.expr_ty(f)) => {
-                typeck_results,
+                        for arg in args {
-            };
+                            check_arg(cx, &raw_ptrs, arg);
-
+                        }
-            intravisit::walk_expr(&mut v, expr);
+                    },
+                    hir::ExprKind::MethodCall(_, recv, args, _) => {
+                        let def_id = typeck.type_dependent_def_id(e.hir_id).unwrap();
+                        if cx.tcx.fn_sig(def_id).skip_binder().unsafety == hir::Unsafety::Unsafe {
+                            check_arg(cx, &raw_ptrs, recv);
+                            for arg in args {
+                                check_arg(cx, &raw_ptrs, arg);
+                            }
+                        }
+                    },
+                    hir::ExprKind::Unary(hir::UnOp::Deref, ptr) => check_arg(cx, &raw_ptrs, ptr),
+                    _ => (),
+                }
+                ControlFlow::Continue(())
+            });
         }
     }
 }
@@ -70,54 +86,13 @@ fn raw_ptr_arg(cx: &LateContext<'_>, arg: &hir::Param<'_>) -> Option<hir::HirId>
     }
 }
 
-struct DerefVisitor<'a, 'tcx> {
+fn check_arg(cx: &LateContext<'_>, raw_ptrs: &HirIdSet, arg: &hir::Expr<'_>) {
-    cx: &'a LateContext<'tcx>,
+    if path_to_local(arg).map_or(false, |id| raw_ptrs.contains(&id)) {
-    ptrs: HirIdSet,
+        span_lint(
-    typeck_results: &'a ty::TypeckResults<'tcx>,
+            cx,
-}
+            NOT_UNSAFE_PTR_ARG_DEREF,
-
+            arg.span,
-impl<'a, 'tcx> intravisit::Visitor<'tcx> for DerefVisitor<'a, 'tcx> {
+            "this public function might dereference a raw pointer but is not marked `unsafe`",
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
+        );
-        match expr.kind {
-            hir::ExprKind::Call(f, args) => {
-                let ty = self.typeck_results.expr_ty(f);
-
-                if type_is_unsafe_function(self.cx, ty) {
-                    for arg in args {
-                        self.check_arg(arg);
-                    }
-                }
-            },
-            hir::ExprKind::MethodCall(_, receiver, args, _) => {
-                let def_id = self.typeck_results.type_dependent_def_id(expr.hir_id).unwrap();
-                let base_type = self.cx.tcx.type_of(def_id);
-
-                if type_is_unsafe_function(self.cx, base_type) {
-                    self.check_arg(receiver);
-                    for arg in args {
-                        self.check_arg(arg);
-                    }
-                }
-            },
-            hir::ExprKind::Unary(hir::UnOp::Deref, ptr) => self.check_arg(ptr),
-            _ => (),
-        }
-
-        intravisit::walk_expr(self, expr);
-    }
-}
-
-impl<'a, 'tcx> DerefVisitor<'a, 'tcx> {
-    fn check_arg(&self, ptr: &hir::Expr<'_>) {
-        if let Some(id) = path_to_local(ptr) {
-            if self.ptrs.contains(&id) {
-                span_lint(
-                    self.cx,
-                    NOT_UNSAFE_PTR_ARG_DEREF,
-                    ptr.span,
-                    "this public function might dereference a raw pointer but is not marked `unsafe`",
-                );
-            }
-        }
     }
 }

clippy_lints/src/methods/unnecessary_filter_map.rs

@@ -2,9 +2,10 @@ use super::utils::clone_or_copy_needed;
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::is_copy;
 use clippy_utils::usage::mutated_variables;
+use clippy_utils::visitors::{for_each_expr, Descend};
 use clippy_utils::{is_res_lang_ctor, is_trait_method, path_res, path_to_local_id};
+use core::ops::ControlFlow;
 use rustc_hir as hir;
-use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_hir::LangItem::{OptionNone, OptionSome};
 use rustc_lint::LateContext;
 use rustc_middle::ty;
@@ -13,7 +14,7 @@ use rustc_span::sym;
 use super::UNNECESSARY_FILTER_MAP;
 use super::UNNECESSARY_FIND_MAP;
 
-pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, name: &str) {
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>, arg: &'tcx hir::Expr<'tcx>, name: &str) {
     if !is_trait_method(cx, expr, sym::Iterator) {
         return;
     }
@@ -26,10 +27,16 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, arg: &hir::Expr<
 
         let (mut found_mapping, mut found_filtering) = check_expression(cx, arg_id, body.value);
 
-        let mut return_visitor = ReturnVisitor::new(cx, arg_id);
+        let _: Option<!> = for_each_expr(body.value, |e| {
-        return_visitor.visit_expr(body.value);
+            if let hir::ExprKind::Ret(Some(e)) = &e.kind {
-        found_mapping |= return_visitor.found_mapping;
+                let (found_mapping_res, found_filtering_res) = check_expression(cx, arg_id, e);
-        found_filtering |= return_visitor.found_filtering;
+                found_mapping |= found_mapping_res;
+                found_filtering |= found_filtering_res;
+                ControlFlow::Continue(Descend::No)
+            } else {
+                ControlFlow::Continue(Descend::Yes)
+            }
+        });
 
         let in_ty = cx.typeck_results().node_type(body.params[0].hir_id);
         let sugg = if !found_filtering {
@@ -97,35 +104,3 @@ fn check_expression<'tcx>(cx: &LateContext<'tcx>, arg_id: hir::HirId, expr: &'tc
         _ => (true, true),
     }
 }
-
-struct ReturnVisitor<'a, 'tcx> {
-    cx: &'a LateContext<'tcx>,
-    arg_id: hir::HirId,
-    // Found a non-None return that isn't Some(input)
-    found_mapping: bool,
-    // Found a return that isn't Some
-    found_filtering: bool,
-}
-
-impl<'a, 'tcx> ReturnVisitor<'a, 'tcx> {
-    fn new(cx: &'a LateContext<'tcx>, arg_id: hir::HirId) -> ReturnVisitor<'a, 'tcx> {
-        ReturnVisitor {
-            cx,
-            arg_id,
-            found_mapping: false,
-            found_filtering: false,
-        }
-    }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for ReturnVisitor<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-        if let hir::ExprKind::Ret(Some(expr)) = &expr.kind {
-            let (found_mapping, found_filtering) = check_expression(self.cx, self.arg_id, expr);
-            self.found_mapping |= found_mapping;
-            self.found_filtering |= found_filtering;
-        } else {
-            walk_expr(self, expr);
-        }
-    }
-}

clippy_lints/src/operators/assign_op_pattern.rs

@@ -2,11 +2,12 @@ use clippy_utils::binop_traits;
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::implements_trait;
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{eq_expr_value, trait_ref_of_method};
+use core::ops::ControlFlow;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
-use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_hir_analysis::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
 use rustc_lint::LateContext;
 use rustc_middle::mir::FakeReadCause;
@@ -65,15 +66,19 @@ pub(super) fn check<'tcx>(
             }
         };
 
-        let mut visitor = ExprVisitor {
+        let mut found = false;
-            assignee,
+        let found_multiple = for_each_expr(e, |e| {
-            counter: 0,
+            if eq_expr_value(cx, assignee, e) {
-            cx,
+                if found {
-        };
+                    return ControlFlow::Break(());
+                }
+                found = true;
+            }
+            ControlFlow::Continue(())
+        })
+        .is_some();
 
-        walk_expr(&mut visitor, e);
+        if found && !found_multiple {
-
-        if visitor.counter == 1 {
             // a = a op b
             if eq_expr_value(cx, assignee, l) {
                 lint(assignee, r);
@@ -98,22 +103,6 @@ pub(super) fn check<'tcx>(
     }
 }
 
-struct ExprVisitor<'a, 'tcx> {
-    assignee: &'a hir::Expr<'a>,
-    counter: u8,
-    cx: &'a LateContext<'tcx>,
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-        if eq_expr_value(self.cx, self.assignee, expr) {
-            self.counter += 1;
-        }
-
-        walk_expr(self, expr);
-    }
-}
-
 fn imm_borrows_in_expr(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> hir::HirIdSet {
     struct S(hir::HirIdSet);
     impl Delegate<'_> for S {

clippy_lints/src/returns.rs

@@ -1,9 +1,11 @@
 use clippy_utils::diagnostics::{span_lint_and_then, span_lint_hir_and_then};
 use clippy_utils::source::{snippet_opt, snippet_with_context};
+use clippy_utils::visitors::{for_each_expr, Descend};
 use clippy_utils::{fn_def_id, path_to_local_id};
+use core::ops::ControlFlow;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::intravisit::{walk_expr, FnKind, Visitor};
+use rustc_hir::intravisit::FnKind;
 use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, HirId, MatchSource, PatKind, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
@@ -270,33 +272,20 @@ fn emit_return_lint(
 }
 
 fn last_statement_borrows<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
-    let mut visitor = BorrowVisitor { cx, borrows: false };
+    for_each_expr(expr, |e| {
-    walk_expr(&mut visitor, expr);
+        if let Some(def_id) = fn_def_id(cx, e)
-    visitor.borrows
+            && cx
-}
-
-struct BorrowVisitor<'a, 'tcx> {
-    cx: &'a LateContext<'tcx>,
-    borrows: bool,
-}
-
-impl<'tcx> Visitor<'tcx> for BorrowVisitor<'_, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
-        if self.borrows || expr.span.from_expansion() {
-            return;
-        }
-
-        if let Some(def_id) = fn_def_id(self.cx, expr) {
-            self.borrows = self
-                .cx
                 .tcx
                 .fn_sig(def_id)
-                .output()
                 .skip_binder()
+                .output()
                 .walk()
-                .any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)));
+                .any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)))
+        {
+            ControlFlow::Break(())
+        } else {
+            ControlFlow::Continue(Descend::from(!expr.span.from_expansion()))
         }
-
+    })
-        walk_expr(self, expr);
+    .is_some()
-    }
 }

clippy_lints/src/suspicious_trait_impl.rs

@@ -1,8 +1,9 @@
 use clippy_utils::diagnostics::span_lint;
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{binop_traits, trait_ref_of_method, BINOP_TRAITS, OP_ASSIGN_TRAITS};
+use core::ops::ControlFlow;
 use if_chain::if_chain;
 use rustc_hir as hir;
-use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -92,25 +93,17 @@ impl<'tcx> LateLintPass<'tcx> for SuspiciousImpl {
 }
 
 fn count_binops(expr: &hir::Expr<'_>) -> u32 {
-    let mut visitor = BinaryExprVisitor::default();
+    let mut count = 0u32;
-    visitor.visit_expr(expr);
+    let _: Option<!> = for_each_expr(expr, |e| {
-    visitor.nb_binops
+        if matches!(
-}
+            e.kind,
-
-#[derive(Default)]
-struct BinaryExprVisitor {
-    nb_binops: u32,
-}
-
-impl<'tcx> Visitor<'tcx> for BinaryExprVisitor {
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-        match expr.kind {
             hir::ExprKind::Binary(..)
-            | hir::ExprKind::Unary(hir::UnOp::Not | hir::UnOp::Neg, _)
+                | hir::ExprKind::Unary(hir::UnOp::Not | hir::UnOp::Neg, _)
-            | hir::ExprKind::AssignOp(..) => self.nb_binops += 1,
+                | hir::ExprKind::AssignOp(..)
-            _ => {},
+        ) {
+            count += 1;
         }
-
+        ControlFlow::Continue(())
-        walk_expr(self, expr);
+    });
-    }
+    count
 }

clippy_lints/src/unwrap_in_result.rs

@@ -1,12 +1,12 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{method_chain_args, return_ty};
+use core::ops::ControlFlow;
 use if_chain::if_chain;
 use rustc_hir as hir;
-use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::ImplItemKind;
-use rustc_hir::{Expr, ImplItemKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{sym, Span};
 
@@ -73,51 +73,37 @@ impl<'tcx> LateLintPass<'tcx> for UnwrapInResult {
     }
 }
 
-struct FindExpectUnwrap<'a, 'tcx> {
-    lcx: &'a LateContext<'tcx>,
-    typeck_results: &'tcx ty::TypeckResults<'tcx>,
-    result: Vec<Span>,
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for FindExpectUnwrap<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
-        // check for `expect`
-        if let Some(arglists) = method_chain_args(expr, &["expect"]) {
-            let receiver_ty = self.typeck_results.expr_ty(arglists[0].0).peel_refs();
-            if is_type_diagnostic_item(self.lcx, receiver_ty, sym::Option)
-                || is_type_diagnostic_item(self.lcx, receiver_ty, sym::Result)
-            {
-                self.result.push(expr.span);
-            }
-        }
-
-        // check for `unwrap`
-        if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
-            let receiver_ty = self.typeck_results.expr_ty(arglists[0].0).peel_refs();
-            if is_type_diagnostic_item(self.lcx, receiver_ty, sym::Option)
-                || is_type_diagnostic_item(self.lcx, receiver_ty, sym::Result)
-            {
-                self.result.push(expr.span);
-            }
-        }
-
-        // and check sub-expressions
-        intravisit::walk_expr(self, expr);
-    }
-}
-
 fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tcx hir::ImplItem<'_>) {
     if let ImplItemKind::Fn(_, body_id) = impl_item.kind {
         let body = cx.tcx.hir().body(body_id);
-        let mut fpu = FindExpectUnwrap {
+        let typeck = cx.tcx.typeck(impl_item.def_id.def_id);
-            lcx: cx,
+        let mut result = Vec::new();
-            typeck_results: cx.tcx.typeck(impl_item.def_id.def_id),
+        let _: Option<!> = for_each_expr(body.value, |e| {
-            result: Vec::new(),
+            // check for `expect`
-        };
+            if let Some(arglists) = method_chain_args(e, &["expect"]) {
-        fpu.visit_expr(body.value);
+                let receiver_ty = typeck.expr_ty(arglists[0].0).peel_refs();
+                if is_type_diagnostic_item(cx, receiver_ty, sym::Option)
+                    || is_type_diagnostic_item(cx, receiver_ty, sym::Result)
+                {
+                    result.push(e.span);
+                }
+            }
+
+            // check for `unwrap`
+            if let Some(arglists) = method_chain_args(e, &["unwrap"]) {
+                let receiver_ty = typeck.expr_ty(arglists[0].0).peel_refs();
+                if is_type_diagnostic_item(cx, receiver_ty, sym::Option)
+                    || is_type_diagnostic_item(cx, receiver_ty, sym::Result)
+                {
+                    result.push(e.span);
+                }
+            }
+
+            ControlFlow::Continue(())
+        });
 
         // if we've found one, lint
-        if !fpu.result.is_empty() {
+        if !result.is_empty() {
             span_lint_and_then(
                 cx,
                 UNWRAP_IN_RESULT,
@@ -125,7 +111,7 @@ fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tc
                 "used unwrap or expect in a function that returns result or option",
                 move |diag| {
                     diag.help("unwrap and expect should not be used in a function that returns result or option");
-                    diag.span_note(fpu.result, "potential non-recoverable error(s)");
+                    diag.span_note(result, "potential non-recoverable error(s)");
                 },
             );
         }