Getting the types in a union type.

gistfile1.fs

open System
open Microsoft.FSharp.Reflection

let GetUnionTypes (t:Type) =
  seq { yield t
        if FSharpType.IsUnion t
        then yield! FSharpType.GetUnionCases t
                    // implementation detail leaks here -- nested type name
                    |> Seq.map (fun x -> (string t) + "+" + x.Name)
                    |> Seq.map Type.GetType }

type expr = Num of int
          | Operation of (expr * expr)

let baseType = typeof<expr>

GetUnionTypes baseType
|> Seq.iter (printfn "%A")
;;