Assignment03Rules: small refactoring

java-feedback-rascal/src/Assignment03Rules.rsc

@@ -51,14 +51,12 @@ set[Message] a03_shapes_implement_comparable(M3 model)
       return { error("There should be two implementations of Geometric: Rectangle and Circle", geometric) };
     }
 
-
     // Rectangle and Circle should only implement Geometric and nothing else
-    result += union(
-      { model.implements[shape] == { geometric }
-        ? {}
-        : { error("<getName(model,shape)> should implement Geometric and nothing else", shape) }
+    result +=
+      { error("<getName(model,shape)> should implement Geometric and nothing else", shape)
       | shape <- shapes
-      });
+      , model.implements[shape] != { geometric }
+      };
 
     // Rectangle and Circle should implement Comparable.compareTo
     loc compareTo = |java+method:///java/lang/Comparable/compareTo(T)|;