anchor.diff:  
           ()"""
           Fsx fsharpSource
  -        |> withLangVersion46
  +        |> withLangVersion50
           |> withReferences [csharpLib]
           |> compile
           |> shouldFail
  
positive.code: """
  
          Fsx fsharpSource
          |> withLangVersion46
          |> withReferences [csharpLib]
          |> compile
          |> shouldFail
  
negative.code:         ()"""
  
          Fsx fsharpSource
          |> withLangVersion50
          |> withReferences [csharpLib]
          |> compile
          |> shouldFail
  