======= AST Display =========================
Package
  ClassDeclList [1]
  . ClassDecl
  .   "id" classname
  .   FieldDeclList [1]
  .   . (public) FieldDecl
  .   .   ClassType
  .   .     "Type" classname
  .   .   "x" fieldname
  .   MethodDeclList [0]
=============================================