Add printing support for assignment operators

src/lib.rs

@@ -136,8 +136,8 @@ impl ExprVisitor<String> for ASTPrinter {
         name.lexeme().to_owned()
     }
 
-    fn visit_assign(&mut self, _name: &lex::Token, _value: &Expr) -> String {
+    fn visit_assign(&mut self, name: &lex::Token, value: &Expr) -> String {
-        todo!()
+        self.parenthesize(&format!("{}=", name.lexeme()), &[value])
     }
 }
 
@@ -167,6 +167,30 @@ mod tests {
         assert_eq!("(+ 123 456)", result);
     }
 
+    #[test]
+    fn test_simple_add_assignment() {
+        let result = ASTPrinter.visit_expr(&Expr::Assign {
+            name: Token::new(
+                TokenKind::Identifier("a".to_string().into()),
+                "a".to_string(),
+                10,
+            ),
+            value: Box::new(Expr::Binary {
+                left: Box::new(Expr::Literal {
+                    value: ast::LiteralValue::Number(123_f64),
+                    token: Token::new(TokenKind::Number(456_f64), "456".to_string(), 10),
+                }),
+                operator: Token::new(TokenKind::Plus, "+".to_string(), 1),
+                right: Box::new(Expr::Literal {
+                    value: ast::LiteralValue::Number(456_f64),
+                    token: Token::new(TokenKind::Number(456_f64), "456".to_string(), 10),
+                }),
+            }),
+        });
+
+        assert_eq!("(a= (+ 123 456))", result);
+    }
+
     #[test]
     fn test_complicated_arithmetic() {
         let result = ASTPrinter.visit_expr(&Expr::Binary {