UnwrapDU.fs

// In *.fsproj add:
//  <PropertyGroup >
//    <WarningsAsErrors>FS0025</WarningsAsErrors>
//  </PropertyGroup>

module Tests

open System
open Xunit

type TestDU =
   | DUCase1 of int
   | DUCase2 of int
   | Unknown

let inline (|UnwrapDU|) x =
    match x with
    | DUCase1 y -> y
    | DUCase2 y -> y
    | Unknown -> failwith "Panic!"

[<Fact>]
let ``My test`` () =
    let du1 = DUCase1 1
    let du2 = DUCase2 2
    let (UnwrapDU u) = du1
    printfn "%i" u
    let (UnwrapDU u) = du2
    printfn "%i" u