Use for_each_expr in place of some visitors

Author: Jarcho

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, Closure, Expr, ExprKind};
+use rustc_hir::{BlockCheckMode, 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 };
-                walk_expr(&mut visitor, cond);
-                if let Some(block) = visitor.found_block {
-                    span_lint(cx, BLOCKS_IN_IF_CONDITIONS, block.span, COMPLEX_BLOCK_MESSAGE);
-                }
+                let _: Option<!> = for_each_expr(cond, |e| {
+                    if let ExprKind::Closure(closure) = e.kind {
+                        // do not lint if the closure is called using an iterator (see #1141)
+                        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::{Body, Expr, ExprKind, FnDecl, HirId};
+use rustc_hir::intravisit::FnKind;
+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;
@@ -63,9 +65,25 @@ impl CognitiveComplexity {
 
         let expr = &body.value;
 
-        let mut helper = CcHelper { cc: 1, returns: 0 };
-        helper.visit_expr(expr);
-        let CcHelper { cc, returns } = helper;
+        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 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 {
-            rust_cc -= ret_adjust;
+        if 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 => {
@@ -108,7 +125,7 @@ impl CognitiveComplexity {
                 fn_span,
                 &format!(
                     "the function has a cognitive complexity of ({}/{})",
-                    rust_cc,
+                    cc,
                     self.limit.limit()
                 ),
                 None,
@@ -141,27 +158,3 @@ 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<'_>) {
@@ -199,61 +202,42 @@ 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,
+fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
+    use hir::ExprKind::{Field, Index, Path};
+
+    match e.kind {
+        Path(QPath::Resolved(_, path)) => !matches!(path.res, Res::Local(_)),
+        Path(_) => true,
+        Field(inner, _) | Index(inner, _) => is_mutated_static(inner),
+        _ => false,
+    }
 }
 
-impl<'a, 'tcx> intravisit::Visitor<'tcx> for StaticMutVisitor<'a, 'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
+fn mutates_static<'tcx>(cx: &LateContext<'tcx>, body: &'tcx hir::Body<'_>) -> bool {
+    for_each_expr(&body.value, |e| {
         use hir::ExprKind::{AddrOf, Assign, AssignOp, Call, MethodCall};
 
-        if self.mutates_static {
-            return;
-        }
-        match expr.kind {
+        match e.kind {
             Call(_, args) | MethodCall(_, 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).expr_ty(arg),
-                            arg.span,
-                            &mut tys,
-                        )
+                    if cx.tcx.has_typeck_results(arg.hir_id.owner.to_def_id())
+                        && is_mutable_ty(cx, cx.tcx.typeck(arg.hir_id.owner).expr_ty(arg), arg.span, &mut tys)
                         && is_mutated_static(arg)
                     {
-                        self.mutates_static = true;
-                        return;
+                        return ControlFlow::Break(());
                     }
                     tys.clear();
                 }
+                ControlFlow::Continue(())
             },
-            Assign(target, ..) | AssignOp(_, target, _) | AddrOf(_, hir::Mutability::Mut, target) => {
-                self.mutates_static |= is_mutated_static(target);
+            Assign(target, ..) | AssignOp(_, target, _) | AddrOf(_, hir::Mutability::Mut, target)
+                if is_mutated_static(target) =>
+            {
+                ControlFlow::Break(())
             },
-            _ => {},
+            _ => ControlFlow::Continue(()),
         }
-    }
-}
-
-fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
-    use hir::ExprKind::{Field, Index, Path};
-
-    match e.kind {
-        Path(QPath::Resolved(_, path)) => !matches!(path.res, Res::Local(_)),
-        Path(_) => true,
-        Field(inner, _) | Index(inner, _) => is_mutated_static(inner),
-        _ => false,
-    }
-}
-
-fn mutates_static<'tcx>(cx: &LateContext<'tcx>, body: &'tcx hir::Body<'_>) -> bool {
-    let mut v = StaticMutVisitor {
-        cx,
-        mutates_static: false,
-    };
-    intravisit::walk_expr(&mut v, &body.value);
-    v.mutates_static
+    })
+    .is_some()
 }