Fix

Author: gusty

src/FSharpPlus/Extensions/Task.fs

@@ -20,32 +20,26 @@ module Task =
         else invalidOp "Internal error: The task is not yet completed."
 
     /// <summary>Creates a task workflow from 'source' another, mapping its result with 'f'.</summary>
-    let map (f: 'T -> 'U) (source: Task<'T>) : Task<'U> =
+    let map (mapper: 'T -> 'U) (source: Task<'T>) : Task<'U> =
         let source = nullArgCheck (nameof source) source
 
-        if source.Status = TaskStatus.RanToCompletion then
-            try Task.FromResult (f source.Result)
-            with e ->
-                let tcs = TaskCompletionSource<'U> ()
-                tcs.SetException e
-                tcs.Task
+        if source.IsCompleted then
+            match source with
+            | Succeeded r ->
+                try Task.FromResult (mapper r)
+                with e -> Task.FromException<'U> e
+            | Faulted exn -> Task.FromException<'U> exn
+            | Canceled    -> Task.FromCanceled<'U> (CancellationToken true)
         else
             let tcs = TaskCompletionSource<'U> ()
-            if source.Status = TaskStatus.Faulted then
-                tcs.SetException (Unchecked.nonNull source.Exception).InnerExceptions
-                tcs.Task
-            elif source.Status = TaskStatus.Canceled then
-                tcs.SetCanceled ()
-                tcs.Task
-            else
-                let k = function
-                    | Canceled    -> tcs.SetCanceled ()
-                    | Faulted e   -> tcs.SetException e.InnerExceptions
-                    | Succeeded r ->
-                        try tcs.SetResult (f r)
-                        with e -> tcs.SetException e
-                source.ContinueWith k |> ignore
-                tcs.Task
+            let k = function
+                | Canceled    -> tcs.SetCanceled ()
+                | Faulted e   -> tcs.SetException e.InnerExceptions
+                | Succeeded r ->
+                    try tcs.SetResult (mapper r)
+                    with e -> tcs.SetException e
+            source.ContinueWith k |> ignore
+            tcs.Task
 
     /// <summary>Creates a task workflow from two workflows 'x' and 'y', mapping its results with 'f'.</summary>
     /// <remarks>Workflows are run in sequence.</remarks>
@@ -408,13 +402,8 @@ module Task =
                 ran <- true
         try
             let task = body ()
-            let rec loop (task: Task<'T>) (compensation : unit -> unit) =
-                match task.Status with
-                | TaskStatus.RanToCompletion -> compensation (); task
-                | TaskStatus.Faulted         -> task.ContinueWith((fun (x:Task<'T>) -> compensation (); x)).Unwrap ()
-                | TaskStatus.Canceled        -> task
-                | _                          -> task.ContinueWith((fun (x:Task<'T>) -> (loop x compensation: Task<_>))).Unwrap ()
-            loop task compensation
+            if task.IsCompleted then compensation (); task
+            else task.ContinueWith(fun (_: Task<'T>) -> compensation (); task).Unwrap ()
         with _ ->
             compensation ()
             reraise ()