如何在匹配模式中使用“使用”声明？

Question

情况：一个函数返回一个Option（Stream）。在调用函数中，我必须以某种方式展开它，以便在使用后丢弃流。我应该把“使用”声明放在哪里？

let getSteamOpt = if System.Random().NextDouble() > 0.5 then Some(new MemoryStream()) else None
let createAndUseStreamIfAny = 
    let streamOpt = getSteamOpt
    match streamOpt with
    | Some( (* use <-- doesn't work like this *) stream) -> printf "stream has to be disposed after this"
    | None -> printf "blah"

Answer 1

let createAndUseStreamIfAny = 
    let streamOpt = getSteamOpt
    match streamOpt with
    | Some(s) -> 
        use stream = s
        printf "stream has to be disposed after this"
    | None -> printf "blah"