# File lib/xsd/codegen/classdef.rb, line 36
  def def_attr(attrname, writable = true, varname = nil)
    unless safevarname?(varname || attrname)
      raise ArgumentError.new("#{varname || attrname} seems to be unsafe")
    end
    @attrdef << [attrname, writable, varname]
  end