anchor.diff:      match this._value with
       | Some value -> return value
       | None ->
  -    let! value = this._asyncBody()
  -    this._value <- Some value
  -    return value
  +      let! value = this._asyncBody()
  +      this._value <- Some value
  +      return value
     }
  
positive.code: type private AsyncCompletionSource<'T> =
  
    [<DefaultValue>]
    val mutable private _completed : 'T -> unit
    [<DefaultValue>]
    val mutable private _caught : exn -> unit
    [<DefaultValue>]
    val mutable private _canceled : OperationCanceledException -> unit
  
    val private _async : Async<'T>
  
  
negative.code:   /// Set result value and continue continuation.
    /// </summary>
    /// <param name="value">Result value</param>
    member this.SetResult value =
      lock (this) (fun () ->
        match this._completed with
        | Some completed -> completed value
        | None -> this._value <- Some value)
  
    /// <summary>
    /// Set exception and continue continuation.
    /// </summary>
    /// <param name="exn">Exception instance</param>
    member this.SetException exn =
      lock (this) (fun () ->
        match this._caught with
        | Some caught -> caught exn
        | None -> this._exn <- Some exn)
  
  ///////////////////////////////////////////////////////////////////////////////////
  
  