neutral_ex_Case_b_fix.diff

+import {ok} from 'assert';
+

+const assert: <T>(item: T|undefined) => asserts
+

 function BuildClasses(topics: ReadonlyArray<TypedTopic>, classes: ClassMap) {
   for (const topic of topics) {
     if (!IsClass(topic)) continue;
 
     const cls = classes.get(topic.Subject.toString());
+    assert(cls);
-    if (!cls) {
-      throw new Error(/**... class should have been forward declared */);
-    }
     toClass(cls, topic, classes);
   }
 }