/** Visitor method: enter classes of a list of trees, returning a list of types. */ <T extends JCTree> List<Type> classEnter(List<T> trees, Env<AttrContext> env) { ListBuffer<Type> ts = new ListBuffer<Type>(); for (List<T> l = trees; l.nonEmpty(); l = l.tail) { Type t = classEnter(l.head, env); if (t != null) ts.append(t); } return ts.toList(); }