Propagating optional arguments

Question

The following code does not compile.

type A(?arg) =
  member __.Arg : string option = arg

type B(?arg) =
  inherit A(arg) //ERROR expected type string but has t         


        

Answer 1

Sorry had to test it first: it seems you are right - you have to do the "?" for A yourself:

type A(arg : string option) =
  new (a) = new A(Some a)
  new () = new A(None)
  member __.Arg : string option = arg

type B(?arg) =
  inherit A(arg)