anchor.diff:    | C of int64 * float32
   
   [<Fact>]
  -let ``simple DU`` () =
  +let simple () =
   
     let input = A
     let actual = convert input
  
positive.code: type StringKeyUnion = | D of Prop : int
  
  [<Fact>]
  let ``string key DU`` () =
  
    let input = D 1
    let actual = convert input
  
negative.code:   Assert.Equal(input, actual)
  
  [<Fact>]
  let ``builtin(string key)`` () =
  
    let input: Result<int, string> = Ok 1
    let actual = convert input
  