feat: 添加赋值运算符支持，更新解析器、解释器和词法分析器以处理相关语法

src/parser/parser.rs

@@ -202,12 +202,26 @@ impl Parser {
     fn assignment(&mut self) -> Expr {
         let expr = self.logical_or();
 
-        if self.match_kind(&[TokenKind::Equal]) {
+        let op = if self.match_kind(&[TokenKind::Equal]) {
+            Some(AssignOp::Equal)
+        } else if self.match_kind(&[TokenKind::PlusEqual]) {
+            Some(AssignOp::PlusEqual)
+        } else if self.match_kind(&[TokenKind::MinusEqual]) {
+            Some(AssignOp::MinusEqual)
+        } else if self.match_kind(&[TokenKind::StarEqual]) {
+            Some(AssignOp::StarEqual)
+        } else if self.match_kind(&[TokenKind::SlashEqual]) {
+            Some(AssignOp::SlashEqual)
+        } else {
+            None
+        };
+
+        if let Some(op) = op {
             let value = self.assignment();
             return match expr {
-                Expr::Variable(name) => Expr::Assign { name, value: Box::new(value) },
-                Expr::Get { object, name } => Expr::Set { object, name, value: Box::new(value) },
-                Expr::IndexGet { array, index } => Expr::IndexSet { array, index, value: Box::new(value) },
+                Expr::Variable(name) => Expr::Assign { name, op, value: Box::new(value) },
+                Expr::Get { object, name } => Expr::Set { object, name, op, value: Box::new(value) },
+                Expr::IndexGet { array, index } => Expr::IndexSet { array, index, op, value: Box::new(value) },
                 _ => panic!("Invalid assignment target."),
             };
         }