Remove unused enums and simplify test assertions

tests/while_loop.rs

@@ -4,12 +4,11 @@ use rhai::Engine;
 fn test_while() {
     let mut engine = Engine::new();
 
-    if let Ok(result) = engine.eval::<i64>(
-        "let x = 0; while x < 10 { x = x + 1; if x > 5 { \
-         break } } x",
-    ) {
-        assert_eq!(result, 6);
-    } else {
-        assert!(false);
-    }
+    assert_eq!(
+        engine.eval::<i64>(
+            "let x = 0; while x < 10 { x = x + 1; if x > 5 { \
+             break } } x",
+        ),
+        Ok(6)
+    );
 }