chore: syntax

src/eval/env.rs

@@ -88,6 +88,6 @@ fn env_should_work() {
     assert_eq!(Some(Object::Int(2)), env1.get("1"));
     // the value in outer env should be updated
     assert_eq!(Some(Object::Int(2)), outer.borrow_mut().get("1"));
-    // should not set set value for self hashmap
+    // should not set value for self hashmap
     assert_eq!(None, env1.store.get("1"))
 }