type A = A

type B = B

type C = C

​

[<RequireQualifiedAccess>]

type ABC =

  | A of A

  | B of B

  | C of C

​

[<RequireQualifiedAccess>]

type UData =

  | TDec of TDec

  | TDate of TDate

  | TBool of TBool 

​

and IUData = abstract member UData: UData

and TDec = TDec with

  interface IUData

    member a.UData = UData.TDec a

and TDate = TDate with 

  interface IUData

    member a.UData = UData.TDate a

and TBool = TBool with   

  interface IUData

    member a.UData = UData.TBool a

​

​

let inline makeGetA< ^T, ^D when ^T : (member A: ^D)> ()=

  fun (t: ^T) -> (^T : (member A: ^D) t)

​

let inline makeGetProp< ^T, ^D, ^P

                                  when ^T : (member A: ^D)

                                  and ^P :> IUData> ()=

  fun (t: ^T) (p: ^P) -> 

     (^T : (member A: ^D) t)

​

type IA<'D> = abstract member A: 'D

​

type IGetP<'P,'D when 'P :> IUData> = abstract member GetP: 'P -> 'D

​

let inline IFromMember< ^T, ^D when ^T : (member A: ^D)>()  =

  let getter = makeGetA< ^T, ^D> ()

  fun (e: ^E) -> { new IA< ^D> with member __.A= getter e}

​

let inline IIFromMember< ^T, ^D when ^T : (member A: ^D)>()  =

  let getter = makeGetA< ^T, ^D> ()

  fun (e: ^E) -> { new IA< ^D> with member __.A= getter e}