how can I mark a context?

impl VisitMut for CleanMarker {
    fn visit_mut_module_item(&mut self, node: &mut ast::ModuleItem) {
        if let ast::ModuleItem::Stmt(ast::Stmt::Expr(expr)) = node {
            match &*expr.expr {
                ast::Expr::Call(e) => {
                    e.ctxt.apply_mark(self.mark);
                    println!("mark call expression {:?}", e.ctxt);
                    println!("has mark {:?}", e.ctxt.has_mark(self.mark));
                }
                _ => {}
            }
        }
    }
}