Implement targeted SocketBox Clone fix for shared mutable state

Co-authored-by: moe-charm <217100418+moe-charm@users.noreply.github.com>

src/boxes/socket_box.rs

@@ -56,18 +56,14 @@ pub struct SocketBox {
 
 impl Clone for SocketBox {
     fn clone(&self) -> Self {
-        // Read the current state values atomically
-        let current_is_server = *self.is_server.lock().unwrap();
-        let current_is_connected = *self.is_connected.lock().unwrap();
-        
-        // For listener and stream, we can't clone them, so we'll share them
-        // but create new Arc instances with the current state
+        // 🔧 FIX: Share state containers for "Everything is Box" reference sharing
+        // This ensures that clones of the same SocketBox share mutable state
         Self {
-            base: BoxBase::new(), // New unique ID for clone
+            base: BoxBase::new(), // New unique ID for clone (for debugging/identity)
             listener: Arc::clone(&self.listener),      // Share the same listener
             stream: Arc::clone(&self.stream),          // Share the same stream  
-            is_server: Arc::new(Mutex::new(current_is_server)),     // New Arc with current value
-            is_connected: Arc::new(Mutex::new(current_is_connected)), // New Arc with current value
+            is_server: Arc::clone(&self.is_server),    // 🔧 Share the same state container
+            is_connected: Arc::clone(&self.is_connected), // 🔧 Share the same state container
         }
     }
 }

src/interpreter/expressions.rs

@@ -51,7 +51,8 @@ impl NyashInterpreter {
             }
             
             ASTNode::FieldAccess { object, field, .. } => {
-                self.execute_field_access(object, field)
+                let shared_result = self.execute_field_access(object, field)?;
+                Ok((*shared_result).clone_box())  // Convert Arc to Box for external interface
             }
             
             ASTNode::New { class, arguments, type_arguments, .. } => {
@@ -672,7 +673,7 @@ impl NyashInterpreter {
     
     /// フィールドアクセスを実行 - Field access processing with weak reference support
     pub(super) fn execute_field_access(&mut self, object: &ASTNode, field: &str) 
-        -> Result<Box<dyn NyashBox>, RuntimeError> {
+        -> Result<SharedNyashBox, RuntimeError> {
         
         // 🔥 Static Boxアクセスチェック
         if let ASTNode::Variable { name, .. } = object {
@@ -734,8 +735,8 @@ impl NyashInterpreter {
                 }
             }
             
-            // Normal field access - convert Arc back to Box for compatibility
-            Ok((*field_value).clone_box())
+            // Return the shared Arc reference directly
+            Ok(field_value)
         } else {
             Err(RuntimeError::TypeError {
                 message: format!("Cannot access field '{}' on non-instance type. Type: {}", field, obj_value.type_name()),

test_basic_sharing.nyash

@@ -0,0 +1,20 @@
+// Test basic field access sharing
+static box Main {
+    init { mybox }
+    
+    main() {
+        me.mybox = new IntegerBox(100)
+        
+        print("=== Test 1: Basic field access ===")
+        local temp1
+        temp1 = me.mybox
+        print("temp1 ID: " + temp1.toString())
+        
+        local temp2
+        temp2 = me.mybox  
+        print("temp2 ID: " + temp2.toString())
+        
+        // The IDs should be the same if sharing works
+        return temp1
+    }
+}

test_box_id_sharing.nyash

@@ -0,0 +1,21 @@
+// Test for Arc sharing - checking if same Box ID is returned
+static box Main {
+    init { server }
+    
+    main() {
+        me.server = new SocketBox()
+        
+        print("=== First access ===")
+        local temp1
+        temp1 = me.server
+        print("Box ID: " + temp1.toString())
+        
+        print("=== Second access ===") 
+        local temp2
+        temp2 = me.server
+        print("Box ID: " + temp2.toString())
+        
+        // If Arc sharing works, both should have same ID
+        return temp1
+    }
+}

test_simple_arc_fix.nyash

@@ -0,0 +1,24 @@
+// Simple test case to verify Arc sharing fix
+static box Main {
+    init { counter }
+    
+    main() {
+        me.counter = new IntegerBox(42)
+        
+        print("=== Initial value ===")
+        print("counter: " + me.counter.to_string())
+        
+        // Test if getting the same field returns the same object
+        local temp1
+        temp1 = me.counter
+        
+        local temp2 
+        temp2 = me.counter
+        
+        print("=== Testing shared reference ===")
+        print("temp1: " + temp1.to_string())
+        print("temp2: " + temp2.to_string())
+        
+        return me.counter
+    }
+}