TaskBuilder allowing two return statements in one expression

[MikeKing1994]

When using task computation expressions it's possible to have two return or return! statements in a row. In this case both the functions called by return/return! are executed, which wouldn't be the expected behavior according to the usually assumed meaning of return.

This can be replicated with the following code, in this case you'll see both "functionA executed" and "functionB executed" printed to the console.

`open FSharp.Core
open FSharp.Control.TaskBuilder

let functionA() =
task {
printfn "functionA executed"
}

let functionB() =
task {
printfn "functionB executed"
}

let main() =
task {
return! functionB()
return! functionA()
}

main() |> Async.AwaitTask |> Async.RunSynchronously`

Whilst computation expressions in general could allow this depending on the definition of the builder, I would argue that the standard TaskBuilder should define return in the canonical sense.

[vzarytovskii]

This is a "standard" behaviour around ReturnFrom semantics + returning a unit, it's not the same as return in the imperative languages.
Even if we wanted to change that behaviour, we can't, since it will be a huge runtime breaking change. Besides, it aligns with behaviour async has around returning from computations which return unit.