diff --git a/src/checker.rs b/src/checker.rs
index b7f9ff92e..d450bcb52 100644
--- a/src/checker.rs
+++ b/src/checker.rs
@@ -3,6 +3,82 @@ use regex::bytes::Regex;
 
 use crate::*;
 
+#[inline(always)]
+fn is_child(node: &Node, id: u16) -> bool {
+    node.object()
+        .children(&mut node.object().walk())
+        .any(|child| child.kind_id() == id)
+}
+
+#[inline(always)]
+fn has_sibling(node: &Node, id: u16) -> bool {
+    node.object().parent().map_or(false, |parent| {
+        node.object()
+            .children(&mut parent.walk())
+            .any(|child| child.kind_id() == id)
+    })
+}
+
+macro_rules! check_if_func {
+    ($node: ident) => {
+        count_specific_ancestors!(
+            $node,
+            VariableDeclarator | AssignmentExpression | LabeledStatement | Pair,
+            StatementBlock | ReturnStatement | NewExpression | Arguments
+        ) > 0
+            || is_child($node, Identifier as u16)
+    };
+}
+
+macro_rules! check_if_arrow_func {
+    ($node: ident) => {
+        count_specific_ancestors!(
+            $node,
+            VariableDeclarator | AssignmentExpression | LabeledStatement,
+            StatementBlock | ReturnStatement | NewExpression | CallExpression
+        ) > 0
+            || has_sibling($node, PropertyIdentifier as u16)
+    };
+}
+
+macro_rules! is_js_func {
+    ($node: ident) => {
+        match $node.object().kind_id().into() {
+            FunctionDeclaration | MethodDefinition => true,
+            Function => check_if_func!($node),
+            ArrowFunction => check_if_arrow_func!($node),
+            _ => false,
+        }
+    };
+}
+
+macro_rules! is_js_closure {
+    ($node: ident) => {
+        match $node.object().kind_id().into() {
+            GeneratorFunction | GeneratorFunctionDeclaration => true,
+            Function => !check_if_func!($node),
+            ArrowFunction => !check_if_arrow_func!($node),
+            _ => false,
+        }
+    };
+}
+
+macro_rules! is_js_func_and_closure_checker {
+    ($grammar: ident) => {
+        #[inline(always)]
+        fn is_func(node: &Node) -> bool {
+            use $grammar::*;
+            is_js_func!(node)
+        }
+
+        #[inline(always)]
+        fn is_closure(node: &Node) -> bool {
+            use $grammar::*;
+            is_js_closure!(node)
+        }
+    };
+}
+
 pub trait Checker {
     fn is_comment(node: &Node) -> bool;
 
@@ -19,6 +95,7 @@ pub trait Checker {
     fn is_string(node: &Node) -> bool;
     fn is_call(node: &Node) -> bool;
     fn is_func(node: &Node) -> bool;
+    fn is_closure(node: &Node) -> bool;
     fn is_func_space(node: &Node) -> bool;
     fn is_non_arg(node: &Node) -> bool;
 
@@ -32,6 +109,7 @@ impl Checker for PreprocCode {
     mk_checker!(is_string, StringLiteral, RawStringLiteral);
     mk_checker!(is_call,);
     mk_checker!(is_func,);
+    mk_checker!(is_closure,);
     mk_checker!(is_func_space,);
     mk_checker!(is_non_arg,);
 }
@@ -41,6 +119,7 @@ impl Checker for CcommentCode {
     mk_checker!(is_string, StringLiteral, RawStringLiteral);
     mk_checker!(is_call,);
     mk_checker!(is_func,);
+    mk_checker!(is_closure,);
     mk_checker!(is_func_space,);
     mk_checker!(is_non_arg,);
 
@@ -66,8 +145,11 @@ impl Checker for CppCode {
         is_func,
         FunctionDefinition,
         FunctionDefinition2,
-        FunctionDefinition3
+        FunctionDefinition3,
+        FunctionDefinition4,
+        FunctionDefinitionRepeat1
     );
+    mk_checker!(is_closure, LambdaExpression);
     mk_checker!(
         is_func_space,
         TranslationUnit,
@@ -106,6 +188,7 @@ impl Checker for PythonCode {
     mk_checker!(is_string, String, ConcatenatedString);
     mk_checker!(is_call, Call);
     mk_checker!(is_func, FunctionDefinition);
+    mk_checker!(is_closure, Lambda);
     mk_checker!(is_func_space, Module, FunctionDefinition, ClassDefinition);
     mk_checker!(is_non_arg, LPAREN, COMMA, RPAREN);
 }
@@ -115,6 +198,7 @@ impl Checker for JavaCode {
     mk_checker!(is_string, StringLiteral);
     mk_checker!(is_call, MethodInvocation);
     mk_checker!(is_func, MethodDeclaration);
+    mk_checker!(is_closure,);
     mk_checker!(is_func_space, Program, ClassDeclaration);
     mk_checker!(is_non_arg,);
 }
@@ -123,15 +207,7 @@ impl Checker for MozjsCode {
     mk_checker!(is_comment, Comment);
     mk_checker!(is_string, String, TemplateString);
     mk_checker!(is_call, CallExpression);
-    mk_checker!(
-        is_func,
-        Function,
-        GeneratorFunction,
-        FunctionDeclaration,
-        GeneratorFunctionDeclaration,
-        MethodDefinition,
-        ArrowFunction
-    );
+
     mk_checker!(
         is_func_space,
         Program,
@@ -145,6 +221,8 @@ impl Checker for MozjsCode {
         ArrowFunction
     );
 
+    is_js_func_and_closure_checker!(Mozjs);
+
     #[inline(always)]
     fn is_else_if(node: &Node) -> bool {
         if node.object().kind_id() != <Self as TSLanguage>::BaseLang::IfStatement {
@@ -162,15 +240,6 @@ impl Checker for JavascriptCode {
     mk_checker!(is_comment, Comment);
     mk_checker!(is_string, String, TemplateString);
     mk_checker!(is_call, CallExpression);
-    mk_checker!(
-        is_func,
-        Function,
-        GeneratorFunction,
-        FunctionDeclaration,
-        GeneratorFunctionDeclaration,
-        MethodDefinition,
-        ArrowFunction
-    );
     mk_checker!(
         is_func_space,
         Program,
@@ -183,6 +252,9 @@ impl Checker for JavascriptCode {
         ClassDeclaration,
         ArrowFunction
     );
+
+    is_js_func_and_closure_checker!(Javascript);
+
     mk_else_if!(IfStatement);
     mk_checker!(is_non_arg, LPAREN, COMMA, RPAREN);
 }
@@ -191,15 +263,6 @@ impl Checker for TypescriptCode {
     mk_checker!(is_comment, Comment);
     mk_checker!(is_string, String, TemplateString);
     mk_checker!(is_call, CallExpression);
-    mk_checker!(
-        is_func,
-        Function,
-        GeneratorFunction,
-        FunctionDeclaration,
-        GeneratorFunctionDeclaration,
-        MethodDefinition,
-        ArrowFunction
-    );
     mk_checker!(
         is_func_space,
         Program,
@@ -213,6 +276,8 @@ impl Checker for TypescriptCode {
         ArrowFunction
     );
 
+    is_js_func_and_closure_checker!(Typescript);
+
     #[inline(always)]
     fn is_else_if(node: &Node) -> bool {
         if node.object().kind_id() != <Self as TSLanguage>::BaseLang::IfStatement {
@@ -230,15 +295,6 @@ impl Checker for TsxCode {
     mk_checker!(is_comment, Comment);
     mk_checker!(is_string, String, TemplateString);
     mk_checker!(is_call, CallExpression);
-    mk_checker!(
-        is_func,
-        Function,
-        GeneratorFunction,
-        FunctionDeclaration,
-        GeneratorFunctionDeclaration,
-        MethodDefinition,
-        ArrowFunction
-    );
     mk_checker!(
         is_func_space,
         Program,
@@ -252,6 +308,9 @@ impl Checker for TsxCode {
         ClassDeclaration,
         ArrowFunction
     );
+
+    is_js_func_and_closure_checker!(Tsx);
+
     mk_else_if!(IfStatement);
     mk_checker!(is_non_arg, LPAREN, COMMA, RPAREN);
 }
@@ -282,7 +341,8 @@ impl Checker for RustCode {
     }
     mk_checker!(is_string, StringLiteral, RawStringLiteral);
     mk_checker!(is_call, CallExpression);
-    mk_checker!(is_func, FunctionItem, ClosureExpression);
+    mk_checker!(is_func, FunctionItem);
+    mk_checker!(is_closure, ClosureExpression);
     mk_checker!(
         is_func_space,
         SourceFile,
diff --git a/src/metrics/nom.rs b/src/metrics/nom.rs
index 21c326ad9..13eb0a2fe 100644
--- a/src/metrics/nom.rs
+++ b/src/metrics/nom.rs
@@ -68,189 +68,29 @@ impl Stats {
     }
 }
 
-#[inline(always)]
-fn is_child(node: &Node, id: u16) -> bool {
-    node.object()
-        .children(&mut node.object().walk())
-        .any(|child| child.kind_id() == id)
-}
-
-#[inline(always)]
-fn has_sibling(node: &Node, id: u16) -> bool {
-    let parent = node.object().parent();
-    if let Some(parent) = parent {
-        node.object()
-            .children(&mut parent.walk())
-            .any(|child| child.kind_id() == id)
-    } else {
-        false
-    }
-}
-
-macro_rules! function {
-    ($node: ident, $stats: ident) => {
-        // If a function node has named ancestors or child then it is a function,
-        // otherwise a closure.
-        if count_specific_ancestors!(
-            $node,
-            VariableDeclarator | AssignmentExpression | LabeledStatement | Pair,
-            StatementBlock | ReturnStatement | NewExpression | Arguments
-        ) > 0
-            || is_child($node, Identifier as u16)
-        {
-            $stats.functions += 1;
-        } else {
-            $stats.closures += 1;
-        }
-    };
-}
-
-macro_rules! arrow_function {
-    ($node: ident, $stats: ident) => {
-        // If an arrow function node has named ancestors then it is a function,
-        // otherwise a closure.
-        if count_specific_ancestors!(
-            $node,
-            VariableDeclarator | AssignmentExpression | LabeledStatement,
-            StatementBlock | ReturnStatement | NewExpression | CallExpression
-        ) > 0
-            || has_sibling($node, PropertyIdentifier as u16)
-        {
-            $stats.functions += 1;
-        } else {
-            $stats.closures += 1;
-        }
-    };
-}
-
-macro_rules! js_grammar {
-    ($grammar: ident, $node: ident, $stats: ident) => {
-        use $grammar::*;
-
-        match $node.object().kind_id().into() {
-            FunctionDeclaration | MethodDefinition => {
-                $stats.functions += 1;
-            }
-            GeneratorFunction | GeneratorFunctionDeclaration => {
-                $stats.closures += 1;
-            }
-            Function => {
-                function!($node, $stats);
-            }
-            ArrowFunction => {
-                arrow_function!($node, $stats);
-            }
-            _ => {}
-        }
-    };
-}
-
-macro_rules! typescript_grammar {
-    ($grammar: ident, $node: ident, $stats: ident) => {
-        use $grammar::*;
-
-        match $node.object().kind_id().into() {
-            FunctionDeclaration | MethodDefinition => {
-                $stats.functions += 1;
-            }
-            GeneratorFunction | GeneratorFunctionDeclaration => {
-                $stats.closures += 1;
-            }
-            Function => {
-                function!($node, $stats);
-            }
-            ArrowFunction => {
-                arrow_function!($node, $stats);
-            }
-            _ => {}
-        }
-    };
-}
-
 #[doc(hidden)]
 pub trait Nom
 where
     Self: Checker,
 {
-    fn compute(_node: &Node, _stats: &mut Stats) {}
-}
-
-impl Nom for PythonCode {
     fn compute(node: &Node, stats: &mut Stats) {
-        use Python::*;
-
-        match node.object().kind_id().into() {
-            FunctionDefinition => {
-                stats.functions += 1;
-            }
-            Lambda => {
-                stats.closures += 1;
-            }
-            _ => {}
+        if Self::is_func(node) {
+            stats.functions += 1;
+            return;
         }
-    }
-}
-
-impl Nom for MozjsCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        js_grammar!(Mozjs, node, stats);
-    }
-}
-
-impl Nom for JavascriptCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        js_grammar!(Javascript, node, stats);
-    }
-}
-
-impl Nom for TypescriptCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        typescript_grammar!(Typescript, node, stats);
-    }
-}
-
-impl Nom for TsxCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        typescript_grammar!(Tsx, node, stats);
-    }
-}
-
-impl Nom for RustCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        use Rust::*;
-
-        match node.object().kind_id().into() {
-            FunctionItem => {
-                stats.functions += 1;
-            }
-            ClosureExpression => {
-                stats.closures += 1;
-            }
-            _ => {}
-        }
-    }
-}
-
-impl Nom for CppCode {
-    fn compute(node: &Node, stats: &mut Stats) {
-        use Cpp::*;
-
-        match node.object().kind_id().into() {
-            FunctionDefinition
-            | FunctionDefinition2
-            | FunctionDefinition3
-            | FunctionDefinition4
-            | FunctionDefinitionRepeat1 => {
-                stats.functions += 1;
-            }
-            LambdaExpression => {
-                stats.closures += 1;
-            }
-            _ => {}
+        if Self::is_closure(node) {
+            stats.closures += 1;
         }
     }
 }
 
+impl Nom for PythonCode {}
+impl Nom for MozjsCode {}
+impl Nom for JavascriptCode {}
+impl Nom for TypescriptCode {}
+impl Nom for TsxCode {}
+impl Nom for RustCode {}
+impl Nom for CppCode {}
 impl Nom for PreprocCode {}
 impl Nom for CcommentCode {}
 impl Nom for JavaCode {}