Reuse token lookup visitor across AST descent

tsc/internal/astnav/tokens.go

@@ -197,8 +197,9 @@ func getTokenAtPosition(
 		return nodeList
 	}
 
+	visitor := getNodeVisitor(visitNode, visitNodeList)
 	for {
-		VisitEachChildAndJSDoc(current, sourceFile, visitNode, visitNodeList)
+		visitEachChildAndJSDoc(current, sourceFile, visitor)
 		// If prevSubtree was set on the last iteration, it ends at the target position.
 		// Check if the rightmost token of prevSubtree should be returned based on the
 		// `includePrecedingTokenAtEndPosition` callback.
@@ -315,7 +316,10 @@ func VisitEachChildAndJSDoc(
 	visitNode func(*ast.Node, *ast.NodeVisitor) *ast.Node,
 	visitNodes func(*ast.NodeList, *ast.NodeVisitor) *ast.NodeList,
 ) {
-	visitor := getNodeVisitor(visitNode, visitNodes)
+	visitEachChildAndJSDoc(node, sourceFile, getNodeVisitor(visitNode, visitNodes))
+}
+
+func visitEachChildAndJSDoc(node *ast.Node, sourceFile *ast.SourceFile, visitor *ast.NodeVisitor) {
 	for _, jsdoc := range node.JSDoc(sourceFile) {
 		if visitor.Hooks.VisitNode != nil {
 			visitor.Hooks.VisitNode(jsdoc, visitor)

tsc/internal/astnav/tokens_test.go

@@ -620,3 +620,15 @@ func tsFindPrecedingTokens(t *testing.T, fileText string, positions []int) []*to
 	assert.NilError(t, err)
 	return info
 }
+
+func BenchmarkGetTokenAtPositionNested(b *testing.B) {
+	text := "const value = " + strings.Repeat("call(", 24) + "target" + strings.Repeat(")", 24) + ";"
+	file := parser.ParseSourceFile(ast.SourceFileParseOptions{FileName: "/test.ts", PathKey: "/test.ts"}, text, core.ScriptKindTS)
+	position := strings.Index(text, "target")
+	b.ReportAllocs()
+	for b.Loop() {
+		if token := astnav.GetTokenAtPosition(file, position); token == nil || token.Kind != ast.KindIdentifier {
+			b.Fatal("target token not found")
+		}
+	}
+}