class RBS::EnvironmentWalker

def tsort_each_node(&block)
  env.class_decls.each_key do |type_name|
    yield InstanceNode.new(type_name: type_name)
    yield SingletonNode.new(type_name: type_name)
  end
  env.interface_decls.each_key do |type_name|
    yield TypeNameNode.new(type_name: type_name)
  end
  env.type_alias_decls.each_key do |type_name|
    yield TypeNameNode.new(type_name: type_name)
  end
end