Task related fixes (#657)

Author: gusty

src/FSharpPlus/Control/Comonad.fs

@@ -16,7 +16,7 @@ type Extract =
     #if FABLE_COMPILER_3 || FABLE_COMPILER_4
         Async.RunSynchronously x
     #else
-        Async.AsTask(x).Result
+        Async.AsTask(x).GetAwaiter().GetResult ()
     #endif
     static member        Extract (x: Lazy<'T>     ) = x.Value
     static member        Extract ((_: 'W, a: 'T)  ) = a
@@ -28,10 +28,10 @@ type Extract =
     static member inline Extract (f: 'Monoid -> 'T) = f (LanguagePrimitives.GenericZero)
     #endif
     #if !FABLE_COMPILER
-    static member        Extract (f: Task<'T>     ) = f.Result
+    static member        Extract (f: Task<'T>     ) = f.GetAwaiter().GetResult ()
     #endif
     #if !NET45 && !NETSTANDARD2_0 && !FABLE_COMPILER
-    static member        Extract (f: ValueTask<'T>     ) = f.Result
+    static member        Extract (f: ValueTask<'T>) = f.GetAwaiter().GetResult ()
     #endif
     static member inline Invoke (x: '``Comonad<'T>``) : 'T =
         let inline call_2 (_mthd: ^M, x: ^I) = ((^M or ^I) : (static member Extract : _ -> _) x)
@@ -82,10 +82,10 @@ type Extend =
                 | ValueTask.Canceled  -> tcs.SetCanceled ()
                 // nowarn here, this case has been handled already if g.IsCompleted
             else
-                ValueTask.continueTask tcs g (fun _ ->
+                g |> ValueTask.continueTask tcs (fun _ ->
                     try tcs.SetResult (f g)
                     with e -> tcs.SetException e)
-            tcs.Task |> ValueTask<'U>
+            ValueTask<'U> tcs.Task
 
     #endif
 

src/FSharpPlus/Extensions/Extensions.fs

@@ -38,11 +38,6 @@ module Extensions =
     open System.Threading.Tasks
     open FSharp.Core.CompilerServices
 
-    let private (|Canceled|Faulted|Completed|) (t: Task<'a>) =
-        if t.IsCanceled then Canceled
-        else if t.IsFaulted then Faulted (Unchecked.nonNull t.Exception) 
-        else Completed t.Result
-
     type Task<'t> with
         static member WhenAll (tasks: Task<'a>[], ?cancellationToken: CancellationToken) =
             let tcs = TaskCompletionSource<'a[]> ()
@@ -53,9 +48,9 @@ module Extensions =
             tasks 
             |> Seq.iteri (fun i t ->
                 let continuation = function
-                | Canceled    -> tcs.TrySetCanceled () |> ignore
-                | Faulted e   -> tcs.TrySetException e |> ignore
-                | Completed r -> 
+                | Task.Canceled    -> tcs.TrySetCanceled () |> ignore
+                | Task.Faulted e   -> tcs.TrySetException e |> ignore
+                | Task.Succeeded r -> 
                     results.[i] <- r
                     if Interlocked.Decrement pending = 0 then 
                         tcs.SetResult results
@@ -132,7 +127,7 @@ module Extensions =
                 computation,
                 ts.SetResult,
                 (function
-                    | :? AggregateException as agg -> ts.SetException agg.InnerExceptions
+                    | :? AggregateException as aex when aex.InnerExceptions.Count > 0 -> ts.SetException aex.InnerExceptions
                     | exn -> ts.SetException exn),
                 (fun _ -> ts.SetCanceled ()),
                 cancellationToken)
@@ -198,7 +193,7 @@ module Extensions =
         /// Similar to Async.Sequential but the returned Async contains a sequence, which is lazily evaluated.
         static member SequentialLazy (t: seq<Async<'T>>) : Async<seq<_>> = async {
             let! ct = Async.CancellationToken
-            return Seq.map (fun t -> Async.AsTask(t, ct).Result) t }
+            return Seq.map (fun t -> Async.AsTask(t, ct).GetAwaiter().GetResult ()) t }
         [<Obsolete("Renamed to Async.Sequential or Async.SequentialLazy")>]static member Sequence (t: seq<Async<_>>) = Async.SequentialLazy t
         #endif