anchor.diff:  
   // Async helper functions copied from https://github.com/jack-pappas/ExtCore/blob/master/ExtCore/ControlCollections.Async.fs
   [<RequireQualifiedAccess>]
  -module Async =
  +module internal Async =
       /// Transforms an Async value using the specified function.
       [<CompiledName("Map")>]
       let map (mapping : 'T -> 'U) (value : Async<'T>) : Async<'U> =
  
positive.code: 
  
  [<Sealed>]
  type AsyncMaybeBuilder () =
      // 'T -> M<'T>
      member (*inline*) x.Return value : Async<'T option> = Some value |> async.Return
  
  
negative.code: /// Maybe computation expression builder, copied from ExtCore library
  /// https://github.com/jack-pappas/ExtCore/blob/master/ExtCore/Control.fs
  [<Sealed>]
  type internal MaybeBuilder () =
      // 'T -> M<'T>
      member inline x.Return value: 'T option =
          Some value
  