anchor.diff:                              !resultRef }
               }
           cloud {
  -            return! stream.Apply collectorf (fun v -> local { return v }) (fun left right -> match left with Some _ -> left | None -> right)
  +            return! stream.Apply collectorf (fun v -> local { return v }) (fun result -> local { return Array.tryPick id result })
           }
   
       /// <summary>Returns the first element for which the given function returns true. Raises KeyNotFoundException if no such element exists.</summary>
  
positive.code:     let ofCloudFiles (reader : System.IO.Stream -> Async<'T>) (sources : seq<CloudFile>) : CloudStream<'T> =
          { new CloudStream<'T> with
              member self.DegreeOfParallelism = None
              member self.Apply<'S, 'R> (collectorf : Local<Collector<'T, 'S>>) (projection : 'S -> Local<'R>) (combiner : 'R -> 'R -> 'R) =
                  cloud { 
                      if Seq.isEmpty sources then 
                          let! collector = collectorf
  
negative.code:     let ofCloudVector (source : CloudVector<'T>) : CloudStream<'T> =
          { new CloudStream<'T> with
              member self.DegreeOfParallelism = None
              member self.Apply<'S, 'R> (collectorf : Local<Collector<'T, 'S>>) (projection : 'S -> Local<'R>) (combiner : 'R [] -> Local<'R>) =
                  cloud {
                      let useCache = source.IsCachingSupported
                      let partitions = getPartitionIndices source
  