refactor: 用 Value::get/set 简化属性访问，消除直接 borrow/borrow_mut 调用

- Value::set 签名改为接受 &str 并返回 RuntimeError，与 evaluator 对齐
- eval_get/eval_set/eval_index_get/eval_index_set 中统一使用 get/set
- 去掉 eval_index_get 和 eval_index_set 中不再使用的 map 绑定

Co-Authored-By: Claude <noreply@anthropic.com>

src/interpreter/eval.rs

@@ -90,9 +90,9 @@ impl super::Interpreter {
     fn eval_get(&mut self, object: Expr, name: String) -> Result<Value, RuntimeError> {
         let obj = self.evaluate(object)?;
         match obj {
-            Value::Object(map) => {
-                match map.borrow().get(&name) {
-                    Some(val) => Ok(val.clone()),
+            Value::Object(_) => {
+                match obj.get(&name) {
+                    Some(val) => Ok(val),
                     None => Err(RuntimeError::RuntimeError {
                         message: format!("Undefined property '{}'", name),
                         token: None,
@@ -215,19 +215,18 @@ impl super::Interpreter {
         let obj = self.evaluate(object)?;
         let rhs = self.evaluate(value)?;
         match obj {
-            Value::Object(map) => {
+            Value::Object(_) => {
                 let val = match op {
                     AssignOp::Equal => rhs,
                     _ => {
-                        let map_borrow = map.borrow();
-                        let current = map_borrow.get(&name).ok_or_else(|| RuntimeError::RuntimeError {
+                        let current = obj.get(&name).ok_or_else(|| RuntimeError::RuntimeError {
                             message: format!("Property '{}' does not exist", name),
                             token: None,
                         })?;
-                        self.apply_assign_op(current.clone(), rhs, op)?
+                        self.apply_assign_op(current, rhs, op)?
                     }
                 };
-                map.borrow_mut().insert(name, val.clone());
+                obj.set(&name, val.clone())?;
                 Ok(val)
             }
             _ => Err(RuntimeError::RuntimeError {
@@ -241,7 +240,7 @@ impl super::Interpreter {
         let target = self.evaluate(array)?;
         let idx_val = self.evaluate(index)?;
         // Object index access: obj["key"]
-        if let Value::Object(map) = &target {
+        if let Value::Object(_) = &target {
             let key = match &idx_val {
                 Value::String(s) => s.clone(),
                 _ => return Err(RuntimeError::RuntimeError {
@@ -249,7 +248,7 @@ impl super::Interpreter {
                     token: None,
                 }),
             };
-            return map.borrow().get(&key).cloned().ok_or_else(|| RuntimeError::RuntimeError {
+            return target.get(&key).ok_or_else(|| RuntimeError::RuntimeError {
                 message: format!("Undefined property '{}'", key),
                 token: None,
             });
@@ -282,7 +281,7 @@ impl super::Interpreter {
         let idx_val = self.evaluate(index)?;
         let rhs = self.evaluate(value)?;
         // Object index assignment: obj["key"] = value
-        if let Value::Object(map) = &target {
+        if let Value::Object(_) = &target {
             let key = match &idx_val {
                 Value::String(s) => s.clone(),
                 _ => return Err(RuntimeError::RuntimeError {
@@ -293,15 +292,14 @@ impl super::Interpreter {
             let val = match op {
                 AssignOp::Equal => rhs,
                 _ => {
-                    let map_borrow = map.borrow();
-                    let current = map_borrow.get(&key).ok_or_else(|| RuntimeError::RuntimeError {
+                    let current = target.get(&key).ok_or_else(|| RuntimeError::RuntimeError {
                         message: format!("Property '{}' does not exist", key),
                         token: None,
                     })?;
-                    self.apply_assign_op(current.clone(), rhs, op)?
+                    self.apply_assign_op(current, rhs, op)?
                 }
             };
-            map.borrow_mut().insert(key, val.clone());
+            target.set(&key, val.clone())?;
             return Ok(val);
         }
         let i = self.as_array_index(&idx_val)?;

src/interpreter/mod.rs

@@ -33,6 +33,28 @@ pub enum Signal {
     Continue,       // continue 信号
 }
 
+impl Value {
+    pub fn get(&self, key: &str) -> Option<Value> {
+        match self {
+            Value::Object(obj) => obj.borrow().get(key).cloned(),
+            _ => None,
+        }
+    }
+
+    pub fn set(&self, key: &str, val: Value) -> Result<(), crate::error::RuntimeError> {
+        match self {
+            Value::Object(obj) => {
+                obj.borrow_mut().insert(key.to_string(), val);
+                Ok(())
+            },
+            _ => Err(crate::error::RuntimeError::RuntimeError {
+                message: "Only objects have properties".to_string(),
+                token: None,
+            }),
+        }
+    }
+}
+
 impl std::fmt::Debug for Value {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {