notSureWhatThis.coffee

abstract = (argTypes..., retType) -> (value) ->
  val = (args...) ->
    args.forEach((arg, index) ->
      if arg.constructor isnt argTypes[index]
        throw new Error('Invalid arg')
    )
    ret = value(args...)
    if ret.constructor isnt retType
      throw new Error('Invalid ret')
    ret
  val.type = arguments.callee
  val

move = abstract(String)
#ride = move () -> 10
ride = move () -> 'ride'

Vehicle = abstract(Object)
Bicycle = Vehicle () ->
  move: ride

#alert(Bicycle.type is Vehicle)
#alert(ride('sfsdf'))
alert(ride())