feat: 新增对象字面量和属性访问表达式

src/ast/expr.rs

@@ -14,6 +14,24 @@ pub enum Expr {
         value: Box<Expr>,
     },
 
+    /// 属性访问表达式：object.name
+    Get {
+        object: Box<Expr>,
+        name: String,
+    },
+
+    /// 属性赋值表达式：object.name = value
+    Set {
+        object: Box<Expr>,
+        name: String,
+        value: Box<Expr>,
+    },
+
+    /// 对象字面量：{ key: value, ... }
+    ObjectLiteral {
+        properties: Vec<(String, Expr)>,
+    },
+
     /// 一元运算：!expr / -expr
     Unary {
         op: UnaryOp,