class StructWithDefaults < Struct
  def initialize(*args)
    defaults = Hash === args.last ? args.pop : {}
    super(*(args + defaults.keys))
  end
end

Foo = StructWithDefaults.new :a => 1
foo = Foo.new

Line 8:in `new': {:a=>1} is not a symbol (TypeError)
	from t.rb:8