code: private static boolean propertyIsImplicitCast(ObjectType type, String prop) {
      for (; type != null; type = type.getImplicitPrototype()) {
        JSDocInfo docInfo = type.getOwnPropertyJSDocInfo(prop);
        if (docInfo != null && docInfo.isImplicitCast()) {
          return true;
        }
      }
      return false;
    }
docs: Returns true if any type in the chain has an implicitCast annotation for
  the given property.