Fix memory leak in tail recursion

[wantastic84]

There was a memory leak in the tail recursion loop rec loop where disposables are not being disposed until the recursion terminates. The fix was done to replace the recursion with while loop.

To illustrate the issue, here is an example for memory leak in tail recursion:

let myDisposer name =
        { new System.IDisposable
          with member this.Dispose() = printfn "disposing %s" name }
    let mutable count = 3
    let rec loop () = async {
        if count > 0 then
            use _ = myDisposer "foo"
            count <- count - 1
            printfn "sleeping for 2 sec for count %d" count
            do! Async.Sleep(2000)
            return! loop()
    }
    loop() |> Async.RunSynchronously

In this case, disposable will not be disposed until the tail recursion terminates. Thus the outcome will be:

sleeping for 2 sec for count 3
sleeping for 2 sec for count 2
sleeping for 2 sec for count 1
disposing foo
disposing foo
disposing foo

The fix was placed to replace the recursion with while loop:

let myDisposer name =
        { new System.IDisposable
          with member this.Dispose() = printfn "disposing %s" name }
    let mutable count = 3
    let aux = async {
        count <- count - 1
        printfn "sleeping for 2 sec for count %d" count
        do! Async.Sleep(2000)
    }
    let loop = async {
        use _ = myDisposer "foo"
        while count > 0 do
            do! aux
    }
    loop |> Async.RunSynchronously

In this case, you will only have one disposable that gets disposed when the while loop terminates:

sleeping for 2 sec for count 3
sleeping for 2 sec for count 2
sleeping for 2 sec for count 1
disposing foo

[bartelink]

Nice catch and fix, thanks!