refactor: replace O(n) children scans with O(1) firstNamedChild/childForFieldName lookups

src/metricsAnalyzer/languages/goAnalyzer.ts

@@ -227,11 +227,11 @@ export class GoMetricsAnalyzer {
         if (typeNode) {
           if (typeNode.type === "pointer_type") {
             // For pointer receivers (*T), display just the base type name T
-            // so CodeLens shows "MyStruct.Method" rather than "*MyStruct.Method"
-            const innerType = typeNode.children.find(
-              (c) => c.type === "type_identifier"
-            );
-            receiverType = innerType
+            // so CodeLens shows "MyStruct.Method" rather than "*MyStruct.Method".
+            // pointer_type has one named child: the inner type. Use firstNamedChild
+            // for O(1) access; fall back to string trimming for non-identifier types.
+            const innerType = typeNode.firstNamedChild;
+            receiverType = innerType?.type === "type_identifier"
               ? this.sourceText.substring(innerType.startIndex, innerType.endIndex)
               : this.sourceText
                   .substring(typeNode.startIndex, typeNode.endIndex)
@@ -415,9 +415,11 @@ export class GoMetricsAnalyzer {
 
   /**
    * Returns true if the node has a label_name child (labeled break/continue/goto).
+   * In Go's AST, label_name is always the first (and only) named child of a labeled
+   * break/continue statement, so firstNamedChild gives an O(1) membership test.
    */
   private hasLabel(node: Parser.SyntaxNode): boolean {
-    return node.children.some((child) => child.type === "label_name");
+    return node.firstNamedChild?.type === "label_name";
   }
 
   /**

src/metricsAnalyzer/languages/jsLikeAnalyzer.ts

@@ -208,10 +208,10 @@ export class JsLikeMetricsAnalyzer {
       }
       if (parent && parent.type === "pair") {
         // Arrow function as an object property value: { myMethod: () => {} }
-        const keyNode = parent.children.find(
-          (c) => c.type === "property_identifier" || c.type === "identifier"
-        );
-        if (keyNode) {
+        // Use childForFieldName("key") for O(1) field access; only use the name
+        // when it is a bare identifier/property_identifier (not a string literal etc.).
+        const keyNode = parent.childForFieldName("key");
+        if (keyNode?.type === "property_identifier" || keyNode?.type === "identifier") {
           return this.sourceText.substring(keyNode.startIndex, keyNode.endIndex);
         }
       }
@@ -379,12 +379,10 @@ export class JsLikeMetricsAnalyzer {
 
       // Labeled break/continue (+1)
       case "break_statement":
-      case "continue_statement": {
-        const hasLabel = node.children.some(
-          (c) => c.type === "statement_identifier"
-        );
-        return hasLabel ? 1 : 0;
-      }
+      case "continue_statement":
+        // In JS/TS, a labeled break/continue has a statement_identifier as its first
+        // (and only) named child. Use firstNamedChild for O(1) instead of a linear scan.
+        return node.firstNamedChild?.type === "statement_identifier" ? 1 : 0;
 
       default:
         return 0;
@@ -416,10 +414,10 @@ export class JsLikeMetricsAnalyzer {
     switch (node.type) {
       case "if_statement":
         return "if statement";
-      case "else_clause": {
-        const hasNestedIf = node.children.some((c) => c.type === "if_statement");
-        return hasNestedIf ? "else if clause" : "else clause";
-      }
+      case "else_clause":
+        // The first named child of else_clause is the if_statement for else-if,
+        // or a statement_block for a plain else. O(1) via firstNamedChild.
+        return node.firstNamedChild?.type === "if_statement" ? "else if clause" : "else clause";
       case "for_statement":
         return "for loop";
       case "for_in_statement": {

src/metricsAnalyzer/languages/rustAnalyzer.ts

@@ -381,10 +381,10 @@ export class RustMetricsAnalyzer {
     switch (node.type) {
       case "if_expression":
         return "if expression";
-      case "else_clause": {
-        const hasNestedIf = node.children.some((c) => c.type === "if_expression");
-        return hasNestedIf ? "else if clause" : "else clause";
-      }
+      case "else_clause":
+        // In Rust's AST, the first named child of else_clause is the if_expression
+        // for an else-if chain, or a block for a plain else. O(1) via firstNamedChild.
+        return node.firstNamedChild?.type === "if_expression" ? "else if clause" : "else clause";
       case "for_expression":
         return "for loop";
       case "while_expression":
@@ -412,10 +412,14 @@ export class RustMetricsAnalyzer {
     }
   }
 
+  /**
+   * Returns true if the node has a loop label child (labeled break/continue).
+   * In Rust's AST, the loop label is always the first named child of break_expression
+   * and continue_expression nodes. Using firstNamedChild avoids an O(n) linear scan.
+   */
   private hasLabel(node: Parser.SyntaxNode): boolean {
-    return node.children.some(
-      (child) => child.type === "label" || child.type === "loop_label"
-    );
+    const childType = node.firstNamedChild?.type;
+    return childType === "label" || childType === "loop_label";
   }
 
   /**